Programmable Logic Controller (PLC)

 

PLC

A programmable logic controller (PLC), or programmable controller is an industrial digital computer which has been ruggedised and adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis.

They were first developed in the automobile industry to provide flexible, ruggedised and easily programmable controllers to replace hard-wired relays and timers. Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a “hard” real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

Programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Some proprietary programming terminals displayed the elements of PLC programs as graphic symbols, but plain ASCII character representations of contacts, coils, and wires were common. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were minimal due to lack of memory capacity. The oldest PLCs used non-volatile magnetic core memory.

More recently, PLCs are programmed using application software on personal computers, which now represent the logic in graphic form instead of character symbols. The computer is connected to the PLC through USB, Ethernet, RS-232, RS-485, or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic. In some software packages, it is also possible to view and edit the program in function block diagrams, sequence flow charts and structured text. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC through a programming board which writes the program into a removable chip such as an EPROM

There are two types of contacts in PLC’s and they are normally open and normally closed switches. A normally open contact means the contact is on when pressed/closed, and a normally closed contact is on when open/not pressed. Contacts represent the states of real world inputs like sensors, switches, if the part is present, empty, full, etc. PLC’s also consist of coils, which are outputs like motors, pumps, lights, timers, etc. The PLC examines inputs and turns coils on or off whenever it is needed. They can also be used as inputs to other rungs in the ladder diagram.

The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems, and networking. The data handling, storage, processing power, and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Desktop computer controllers have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. Operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the controller may not always respond to changes of input status with the consistency in timing expected from PLCs. Desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs

The most basic function of a Programmable logic controller (PLC) is to receive inputs from status components, which can be from sensors or switches. Some of the basic components of a PLC are input modules, a central processing unit, output modules, and a programming device. When an input is activated, some output will also be activated by whatever you told the machine to do. Some examples of this are setting a timer to 10ms, activating the timer and once 10ms have passed a siren goes off. Some advantages to using a PLC over other programming devices are the user doesn’t have to rewire anything, the PLC has very little downtime in between running different programs, the user can program off-line, and PLC’s aren’t time constrained. If the user tells the PLC to perform an output in 10ms, it will perform the output in 10ms unlike other programs like LabView which can have a delay in activation.

The main function of a timer is to keep an output on for a specific length of time. A good example of this is a garage light needing to cut off after 2 minutes to give someone time to go into the house. The three different types of timers that are commonly used are a Delay-OFF, a Delay-ON, and a Delay-ON-Retentive. A Delay-OFF timer activates immediately when turned on, counts down from a programmed time then cuts off, and is cleared when the enabling input is off. A Delay-ON timer is activated by input and starts accumulating time, counts up to a programmed time and then cuts off, and is cleared when the enabling input is turned off. A Delay-ON-Retentive timer is activated by input and starts accumulating time, retains the accumulated value even if the rung goes false, and resets only by a RESET contact.

Counters are primarily used for counting items such as cans going into a box on an assembly line. This is important because once something is filled to its max the item needs to be moved on so something else can be filled. Many companies use counters in PLC’s to count boxes, count how many feet of something is covered, or to count how many pallets are on a truck. There are three types of counters, Up counters, Down counters, and Up/Down counters. Up counters count up to the preset value, turns on the CTU when the preset value is reached, and cleared on reset. Down counters count down from a preset value, turns on CTD when 0 is reached, and cleared on reset. Up/Down counters count up on CU, count down on CD, turns on when CTUD is greater than the preset value is reached, and cleared on reset.

In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are needed, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have 8 to 12 discrete inputs, 4 to 8 discrete outputs, and up to 2 analog inputs. Size is usually about 4″ wide, 3″ high, and 3″ deep. Most such devices include a tiny postage-stamp-sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC, and they still offer robust design and deterministic execution of the logics.

The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold), and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.

A PLC program is generally executed repeatedly as long as the controlled system is running. The status of physical input points is copied to an area of memory accessible to the processor, sometimes called the “I/O Image Table”. The program is then run from its first instruction rung down to the last rung. It takes some time for the processor of the PLC to evaluate all the rungs and update the I/O image table with the status of outputs. This scan time may be a few milliseconds for a small program or on a fast processor, but older PLCs running very large programs could take much longer (say, up to 100 ms) to execute the program. If the scan time were too long, the response of the PLC to process conditions would be too slow to be useful.

As PLCs became more advanced, methods were developed to change the sequence of ladder execution, and subroutines were implemented. This simplified programming could be used to save scan time for high-speed processes; for example, parts of the program used only for setting up the machine could be segregated from those parts required to operate at higher speed.

Special-purpose I/O modules may be used where the scan time of the PLC is too long to allow predictable performance. Precision timing modules, or counter modules for use with shaft encoders, are used where the scan time would be too long to reliably count pulses or detect the sense of rotation of an encoder. The relatively slow PLC can still interpret the counted values to control a machine, but the accumulation of pulses is done by a dedicated module that is unaffected by the speed of the program execution.

The 5 main steps in one complete scan cycle are reading the inputs, executing the program, processing communication requests, executing CPU diagnostics, and writing to the outputs. To read the inputs, the user writes values to the input image table which are reserved in bytes. When executing the program, the ladder is read from right to left, and top to bottom. When processing communication requests, the user processes any message received from the communications port. To execute the CPU Self-Diagnostic test, check the firmware, check the program, and check the status of the modules

A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O.

Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules are customized for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. Either a special high speed serial I/O link or comparable communication method is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants. Options are also available to mount I/O points directly to the machine and utilize quick disconnecting cables to sensors and valves, saving time for wiring and replacing components.

PLCs may need to interact with people for the purpose of configuration, alarm reporting, or everyday control. A human-machine interface (HMI) is employed for this purpose. HMIs are also referred to as man-machine interfaces (MMIs) and graphical user interfaces (GUIs). A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use programming and monitoring software installed on a computer, with the PLC connected via a communication interface.

PLCs have built-in communications ports, usually 9-pin RS-232, RS-422, RS-485, Ethernet. Various protocols are usually included. Many of these protocols are vendor specific.

Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.

PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.

PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non- volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays.

Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. The most commonly used programming language is Ladder diagram (LD) also known as Ladder logic. It uses Contact-Coil logic to make programs like an electrical control diagram. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. A model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.

IEC 61131-3 currently defines five programming languages for programmable control systems: function block diagram (FBD), ladder diagram (LD), structured text (ST; similar to the Pascal programming language), instruction list (IL; similar to assembly language), and sequential function chart (SFC). These techniques emphasize logical organization of operations.

While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization, and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible.

PLCs are well adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems, so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economical. This is due to the lower cost of the components, which can be optimally chosen instead of a “generic” solution, and where the non-recurring engineering charges are spread over thousands or millions of units.

For high volume or very simple fixed automation tasks, different techniques are used. For example, a cheap consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.

A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware, and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit buses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomical.

Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customized solutions; for example, aircraft flight controls. Single-board computers using semi-customized or fully proprietary hardware may be chosen for very demanding control applications where the high development and maintenance cost can be supported. “Soft PLCs” running on desktop-type computers can interface with industrial I/O hardware while executing programs within a version of commercial operating systems adapted for process control needs.

Programmable controllers are widely used in motion, positioning, and/or torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements.

PLCs may include logic for single-variable feedback analog control loop, a proportional, integral, derivative (PID) controller. A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has been blurred.

PLCs have similar functionality as remote terminal units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs, and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features, and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.

In recent years “safety” PLCs have started to become popular, either as standalone models or as functionality and safety-rated hardware added to existing controller architectures (Allen-Bradley Guardlogix, Siemens F-series etc.). These differ from conventional PLC types as being suitable for use in safety-critical applications for which PLCs have traditionally been supplemented with hard-wired safety relays. For example, a safety PLC might be used to control access to a robot cell with trapped-key access, or perhaps to manage the shutdown response to an emergency stop on a conveyor production line. Such PLCs typically have a restricted regular instruction set augmented with safety-specific instructions designed to interface with emergency stops, light screens, and so forth. The flexibility that such systems offer has resulted in rapid growth of demand for these controllers.

Industrial control system (ICS) is a general term that encompasses several types of control systems and associated instrumentation used in industrial production technology, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.

Industrial control systems are typically used in industries such as electrical, water, oil, gas and data.

Based on data received from remote stations, automated or operator-driven supervisory commands can be pushed to remote station control devices, which are often referred to as field devices. Field devices control local operations such as opening and closing valves and breakers, collecting data from sensor systems, and monitoring the local

Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controllers and discrete PID controllers to interface to the process plant or machinery. The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA supervisory computer system. However, the real-time control logic or controller calculations are performed by networked modules which connect to the field sensors and actuators.

The SCADA concept was developed as a universal means of remote access to a variety of local control modules, which could be from different manufacturers allowing access through standard automation protocols. In practice, large SCADA systems have grown to become very similar to distributed control systems in function, but using multiple means of interfacing with the plant. They can control large-scale processes that can include multiple sites, and work over large distances. It is one of the most commonly-used types of industrial control systems, however there are concerns about SCADA systems being vulnerable to cyberwarfare/cyberterrorism attacks.

Referring to the functional hierarchy diagram in this article:

Level 1 contains the PLCs or RTUs

Level 2 contains the SCADA software and computing platform.

The SCADA software exists only at this supervisory level as control actions are performed automatically by RTUs or PLCs. SCADA control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow. The SCADA also enables alarm conditions, such as loss of flow or high temperature, to be displayed and recorded. A feedback control loop is directly controlled by the RTU or PLC, but the SCADA software monitors the overall performance of the loop.

 

PLCs can range from small “building brick” devices with tens of I/O in a housing integral with the processor, to large rack-mounted modular devices with a count of thousands of I/O, and which are often networked to other PLC and SCADA systems.

They can be designed for multiple arrangements of digital and analog inputs and outputs (I/O), extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory.

It was in the automotive industry in the USA that the PLC was created. Before the PLC, the control, sequencing, and safety interlock logic for manufacturing automobiles was mainly composed of relays, cam timers, drum sequencers, and dedicated closed-loop controllers. Since these could number in the hundreds or even thousands, the process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire the relays to change their operational characteristics.

When digital computers became available, being general-purpose programmable devices, they were soon applied to control sequential and combinatorial logic in industrial processes. However these early computers required specialist programmers, and stringent operating environmental control for temperature, cleanliness, and power quality. To meet these challenges this the PLC was developed with several key attributes. It would tolerate the shop-floor environment, it would support discrete input and output, and it was easily maintained and programmed.

Control system security is the prevention of intentional or unintentional interference with the proper operation of industrial automation and control systems. These control systems manage essential services including electricity, petroleum production, water, transportation, manufacturing, and communications. They rely on computers, networks, operating systems, applications, and programmable controllers, each of which could contain security vulnerabilities. The 2010 discovery of the Stuxnet worm demonstrated the vulnerability of these systems to cyber incidents.The United States and other governments have passed cyber-security regulations requiring enhanced protection for control systems operating critical infrastructure.

Control system security is known by several other names such as SCADA security, PCN security, industrial network security, and control system cyber security.

Insecurity of industrial automation and control systems can lead consequences in categories such as:

Safety
Environmental impact
Lost production
Equipment damage
Information theft
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Operational Technology is utilized in many sectors and environments, such as:

Oil & Gas
Power and Utilities
Chemicals manufacturing
Water treatment
Waste management
Transportation
Scientific experimentation

An industrial safety system is a counter measure crucial in any hazardous plants such as oil and gas plants and nuclear plants. They are used to protect human, industrial plant, and the environment in case of the process going beyond the allowed control margins.

As the name suggests, these systems are not intended for controlling the process itself but rather protection. Process control is performed by means of process control systems (PCS) and is interlocked by the safety systems so that immediate actions are taken should the process control systems fail.

Process control and safety systems are usually merged under one system, called Integrated Control and Safety System (ICSS). Industrial safety systems typically use dedicated systems that are SIL 2 certified at minimum; whereas control systems can start with SIL 1. SIL applies to both hardware and software requirements such as cards, processors redundancy and voting functions.

Pressure safety valves
Pressure safety valves or PSVs are usually used as a final safety solution when all previous systems fail to prevent any further pressure accumulation and protect vessels from rupture due to overpressure by their designed action.

 

There are three main types of industrial safety systems in process industry:

Process Safety System or Process Shutdown System, (PSS).
Safety Shutdown System (SSS): This includes Emergency Shutdown-(ESD) and Emergency Depressurization-(EDP) Systems.

 

SSS
The safety shutdown system (SSS) shall shut down the facilities to a safe state in case of an emergency situation, thus protecting personnel, the environment and the asset. The safety shutdown system shall manage all inputs and outputs relative to emergency shutdown (ESD) functions (environment and personnel protection). This system might also be fed by signals from the main fire and gas system.

FGS
The main objectives of the fire and gas system are to protect personnel, environment, and plant (including equipment and structures). The FGS shall achieve these objectives by:

Detecting at an early stage, the presence of flammable gas,
Detecting at an early stage, the liquid spill (LPG and LNG),
Detecting incipient fire and the presence of fire,
Providing automatic and/or facilities for manual activation of the fire protection system as required,
Initiating environmental changes to keep liquids below their flash point
Initiating signals, both audible and visible as required, to warn of the detected hazards,
Initiating automatic shutdown of equipment and ventilation if 2 out of 2 or 2 out of 3 detectors are triggered,
Initiating the exhausting system.
EDP
Due to closing ESD valves in a process, there may be some trapped flammable fluids, and these must be released in order to avoid any undesired consequences (such as pressure increase in vessels and piping). For this, emergency depressurization (EDP) systems are used in conjunction with the ESD systems to release (to a safe location and in a safe manner) such trapped fluids.

 

PLC technicians design, program, repair and maintain programmable logic controller (PLC) systems used within manufacturing and service industries ranging from industrial packaging to commercial car washes and traffic lights.

 

PLC technicians are knowledgeable in overall plant systems and the interactions of processes. They install and service a variety of systems including safety and security, energy delivery (hydraulic, pneumatic and electrical), communication, and process control systems. They also install and service measuring and indicating instruments to monitor process control variables associated with PLCs, and monitor the operation of PLC equipment. PLC technicians work with final control devices such as valves, actuators and positioners to manipulate the process medium. They install and terminate electrical, pneumatic and fluid connections. They also work on network and signal transmission systems such as fibre optic and wireless.

Along with the calibration, repair, adjustment and replacement of components, PLC technicians inspect and test the operation of instruments and systems to diagnose faults and verify repairs. They establish and optimize process control strategies, and configure related systems such as Distributed Control Systems (DCSs), Supervisory Control & Data Acquisition (SCADA), and Human Machine Interfaces (HMIs). PLC technicians maintain backups, documentation and software revisions as part of maintaining these computer-based control systems. Scheduled maintenance and the commissioning of systems are also important aspects of the work. PLC technicians consult technical documentation, drawings, schematics and manuals. They may assist engineering in plant design, modification and hazard analysis, and work with plant operators to optimize plant controls.

PLC technicians use hand, power and electronic tools, test equipment, and material handling equipment. They work on a variety of systems including primary control elements, transmitters, analyzers, sensors, detectors, signal conditioners, recorders, controllers and final control elements (actuators, valve positioners, etc.). These instruments measure and control variables such as pressure, flow, temperature, level, motion, force and chemical composition. PLC systems designed and maintained by PLC technicians range from high speed robotic assembly to conveyors, to batch mixers, to DCS and SCADA systems. PLC systems are often found within industrial and manufacturing plants, such as food processing facilities. Alternate job titles include PLC engineer, Automation Technician, Field Technician or Controls Technician.

Automation equipment wholesalers
Industrial manufacturing companies
Water Treatment plants
Nuclear and Hydro Electric Power companies
Pharmaceutical companies
Mining, petrochemical and natural gas companies
Pulp and paper processing companies

Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controllers and discrete PID controllers to interface to the process plant or machinery. The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA supervisory computer system. However, the real-time control logic or controller calculations are performed by networked modules which connect to the field sensors and actuators.

 

Human-machine interface
Further information: Graphical user interface
File:Scada Animation.ogv
More complex SCADA animation showing control of four batch cookers
The human-machine interface (HMI) is the operator window of the supervisory system. It presents plant information to the operating personnel graphically in the form of mimic diagrams, which are a schematic representation of the plant being controlled, and alarm and event logging pages. The HMI is linked to the SCADA supervisory computer to provide live data to drive the mimic diagrams, alarm displays and trending graphs. In many installations the HMI is the graphical user interface for the operator, collects all data from external devices, creates reports, performs alarming, sends notifications, etc.

Mimic diagrams consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.

Supervisory operation of the plant is by means of the HMI, with operators issuing commands using mouse pointers, keyboards and touch screens. For example, a symbol of a pump can show the operator that the pump is running, and a flow meter symbol can show how much fluid it is pumping through the pipe. The operator can switch the pump off from the mimic by a mouse click or screen touch. The HMI will show the flow rate of the fluid in the pipe decrease in real time.

The HMI package for a SCADA system typically includes a drawing program that the operators or system maintenance personnel use to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of an actual traffic light in the field, or as complex as a multi-projector display representing the position of all of the elevators in a skyscraper or all of the trains on a railway.

A “historian”, is a software service within the HMI which accumulates time-stamped data, events, and alarms in a database which can be queried or used to populate graphic trends in the HMI. The historian is a client that requests data from a data acquisition server.

 

An important part of most SCADA implementations is alarm handling. The system monitors whether certain alarm conditions are satisfied, to determine when an alarm event has occurred. Once an alarm event has been detected, one or more actions are taken (such as the activation of one or more alarm indicators, and perhaps the generation of email or text messages so that management or remote SCADA operators are informed). In many cases, a SCADA operator may have to acknowledge the alarm event; this may deactivate some alarm indicators, whereas other indicators remain active until the alarm conditions are cleared.

Alarm conditions can be explicit—for example, an alarm point is a digital status point that has either the value NORMAL or ALARM that is calculated by a formula based on the values in other analogue and digital points—or implicit: the SCADA system might automatically monitor whether the value in an analogue point lies outside high and low- limit values associated with that point.

Examples of alarm indicators include a siren, a pop-up box on a screen, or a coloured or flashing area on a screen (that might act in a similar way to the “fuel tank empty” light in a car); in each case, the role of the alarm indicator is to draw the operator’s attention to the part of the system ‘in alarm’ so that appropriate action can be taken.

“Internet of things”
With the commercial availability of cloud computing, SCADA systems have increasingly adopted Internet of things technology to significantly reduce infrastructure costs and increase ease of maintenance and integration. As a result, SCADA systems can now report state in near real-time and use the horizontal scale available in cloud environments to implement more complex control algorithms than are practically feasible to implement on traditional programmable logic controllers. Further, the use of open network protocols such as TLS inherent in the Internet of things technology, provides a more readily comprehensible and manageable security boundary than the heterogeneous mix of proprietary network protocols typical of many decentralized SCADA implementations. One such example of this technology is an innovative approach to rainwater harvesting through the implementation of real time controls (RTC).

This decentralization of data also requires a different approach to SCADA than traditional PLC based programs. When a SCADA system is used locally, the preferred methodology involves binding the graphics on the user interface to the data stored in specific PLC memory addresses. However, when the data comes from a disparate mix of sensors, controllers and databases (which may be local or at varied connected locations), the typical 1 to 1 mapping becomes problematic. A solution to this is data modeling, a concept derived from object oriented programming.

In a data model, a virtual representation of each device is constructed in the SCADA software. These virtual representations (“models”) can contain not just the address mapping of the device represented, but also any other pertinent information (web based info, database entries, media files, etc.) that may be used by other facets of the SCADA/IoT implementation. As the increased complexity of the Internet of things renders traditional SCADA increasingly “house-bound,” and as communication protocols evolve to favor platform-independent, service-oriented architecture (such as OPC UA), it is likely that more SCADA software developers will implement some form of data modeling.

 

Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, standardized as IEC 61158.

A complex automated industrial system — such as manufacturing assembly line — usually needs a distributed control system—an organized hierarchy of controller systems—to function. In this hierarchy, there is usually a Human Machine Interface (HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controllers (PLC) via a non-time-critical communications system (e.g. Ethernet). At the bottom of the control chain is the fieldbus that links the PLCs to the components that actually do the work, such as sensors, actuators, electric motors, console lights, switches, valves and contactors.

 

Fieldbus can be used for systems which must meet safety-relevant standards like IEC 61508 or EN 954-1. Depending on the actual protocol, fieldbus can provide measures like counters, CRCs, echo, timeout, unique sender and receiver IDs or cross check. Ethernet/IP and SERCOS III both use the CIP Safety protocol, Ethernet Powerlink uses openSAFETY, while FOUNDATION Fieldbus and Profibus (PROFIsafe) can address SIL 2 and SIL 3 process safety applications.

 

Advanced process control

 

APC: Advanced process control
ARC: Advanced regulatory control, including feedforward, adaptive gain, override, logic, fuzzy logic, sequence control, device control, inferentials, and custom algorithms; usually implies DCS-based.
Base-Layer: Includes DCS, SIS, field devices, and other DCS subsystems, such as analyzers, equipment health systems, and PLCs.
BPCS: Basic process control system (see “base-layer”)
DCS: Distributed control system, often synonymous with BPCS
MPO: Manufacturing planning optimization
MPC: Multivariable Model predictive control
SIS: Safety instrumented system
SME: Subject matter expert

Control Applications
Automation and Remote Control
Distributed Control System
Electric motors
Industrial Control Systems
Mechatronics
Motion control
Process Control
Robotics
Supervisory control (SCADA)

In control theory Advanced process control (APC) refers to a broad range of techniques and technologies implemented within industrial process control systems. Advanced process controls are usually deployed optionally and in addition to basic process controls. Basic process controls are designed and built with the process itself, to facilitate basic operation, control and automation requirements. Advanced process controls are typically added subsequently, often over the course of many years, to address particular performance or economic improvement opportunities in the process.

Process control (basic and advanced) normally implies the process industries, which includes chemicals, petrochemicals, oil and mineral refining, food processing, pharmaceuticals, power generation, etc. These industries are characterized by continuous processes and fluid processing, as opposed to discrete parts manufacturing, such as automobile and electronics manufacturing. The term process automation is essentially synonymous with process control.

Process controls (basic as well as advanced) are implemented within the process control system, which usually means a distributed control system (DCS), programmable logic controller (PLC), and/or a supervisory control computer. DCSs and PLCs are typically industrially hardened and fault-tolerant. Supervisory control computers are often not hardened or fault-tolerant, but they bring a higher level of computational capability to the control system, to host valuable, but not critical, advanced control applications. Advanced controls may reside in either the DCS or the supervisory computer, depending on the application. Basic controls reside in the DCS and its subsystems, including PLCs.

 

Manufacturing

Factory
Heavy industry
Light industry
Mass production
Production line

Aerospace industry
Automotive industry
Chemical industry
Computer industry
Electronics industry
Food processing industry
Garment industry
Pharmaceutical industry
Pulp and paper industry
Toy industry

Production technology
Industrial robot
Computer-aided manufacturing
Computer Integrated Manufacturing
Production equipment control
Computer numerically controlled
Distributed Control System
Fieldbus control system
PLCs / PLD
Advanced Planning & Scheduling
Scheduling (production processes)
SCADA supervisory control and data acquisition
computerized maintenance management system (CMMS)
Packaging and labeling
Machinery
Machinery
Production line
Assembly line
Conveyor belt
Woodworking machinery
Metalworking machinery
Textile machinery
Equipment manufacturer

 

Control system – a device, or set of devices to manage, command, direct or regulate the behavior of other devices or system.
Industrial control system (ICS) – encompasses several types of control systems used in industrial production, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as skid-mounted programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.
Industrialization – period of social and economic change that transforms a human group from an agrarian society into an industrial one.
Numerical control (NC) – refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage medium, as opposed to controlled manually via handwheels or levers, or mechanically automated via cams alone.
Robotics – the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots and computer systems for their control, sensory feedback, and information processing.

 

Autonomous automation – autonomous software agents to adapt the controllers of computer controlled industrial machinery and processes
Building automation – advanced functionality provided by the control system of a building. A building automation system (BAS) is an example of a distributed control system.
Home automation – control system of a home.

 

Artificial neural network (ANN) – mathematical model or computational model that is inspired by the structure or functional aspects of biological neural networks.
Human machine interface (HMI) – operator level local control panel that control monitors the field devices,
Laboratory information management system (LIMS) – software package that offers a set of key features that support a modern laboratory’s operations.
Industrial control system – encompasses several types of control systems used in industrial production, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as skid-mounted programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.
Distributed control system (DCS) – control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers.
Manufacturing execution system (MES) – system that manages manufacturing operations in a factory, including management of resources, scheduling production processes, dispatching production orders, execution of production orders, etc.
Programmable automation controller (PAC) – digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures.
Programmable logic controller (PLC)A Programmable Logic Controller, PLC or Programmable Controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. The abbreviation “PLC” and the term “Programmable Logic Controller” are registered trademarks of the Allen-Bradley Company (Rockwell Automation). PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is an example of a hard real time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result. –
Supervisory control and data acquisition (SCADA) – generally refers to industrial control systems (ICS): computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:* Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
Simulation#Engineering Technology simulation or Process simulation –

Wireless Networks for Industrial Automation
Wireless sensor networks
The main features of WSNs, as could be deduced by the general description given in the previous sections, are:
scalability with respect to the number of nodes in the network, self-organization, self-healing, energy efficiency, a sufficient degree of connectivity among nodes, low-complexity, low cost and size of nodes. Those protocol architectures and technical solutions providing such features can be considered as a potential framework for the creation of these networks, but, unfortunately, the definition of such a protocol architecture and technical solution is not simple, and the research still needs to work on it.

The massive research on WSNs started after the year 2000. However, it took advantage of the outcome of the research on wireless networks performed since the second half of the previous century. In particular, the study of ad hoc networks attracted a lot of attention for several decades, and some researchers tried to report their skills acquired in the field of ad hoc networks, to the study of WSNs. According to some general definitions, wireless ad hoc networks are formed dynamically by an autonomous system of nodes connected via wireless links without using an existing network infrastructure or centralized
administration. Nodes are connected through “ad hoc” topologies, set up and cleared according to user needs and temporary conditions. Apparently, this definition can include WSNs. However, this is not true. This is the list of main features for wireless ad hoc networks: unplanned and highly dynamical; nodes are “smart” terminals (laptops, etc.); typical applications include realtime or non-realtime data, multimedia, voice; every node can be either source or destination of information; every node can be a router toward other nodes; energy is not the most relevant matter; capacity is the most relevant matter.

Apart from the very first item, which is common to WSNs, in all other cases there is a clear distinctionbetween WSNs and wireless ad hoc networks. In WSNs, nodes are simple and low-complexity devices;the typical applications require few bytes sent periodically or upon request or according to some external event; every node can be either source or destination of information, not both; some nodes do not play the role of routers; energy efficiency is a very relevant matter, while capacity is not for most applications.Therefore, WSNs are not a special case of wireless ad hoc networks. Thus, a lot of care must be used when considering protocols and algorithms which are good for ad hoc networks, and using them in the context of WSNs

Sensor Technologies functions in highly powered high-speed and low-cost electronic circuits. In a developing world, the need for sensor technologies with a view to support systems automation, security and information dissemination is on the increase. The application of sensor technology in diverse ways has eventually enforced the increase of the requirement for the implementation. The design of smart homes and environment is made possible by the use of sensor devices. Sensor technologies in this respect are expected to provide novel approaches and solutions as required. Sensor can be considered as complex devices that can be used to detectand respond to signals being produced. A sensor primarily converts physical parameters into signal. These parameters can be; temperature, humidity, and speed. The signal produced can be measured electronically. When deciding on a particular sensor to use in a given task, the following consideration will be employed; Cost, Range, Accuracy, Environmental consideration, and Resolution The Industrial Wireless Sensor Networks IWSNs have the potential to improve productivity of industrial systems by providing greater awareness, control, and integration of business processes. Despite of the great progress on development of IWSNs, quite a few issues still need to be explored in the future. For example, an efficient deployment of IWSNs in the real world is highly dependent on the ability to devise analytical models to evaluate and predict IWSNs performance characteristics, such as communication latency and reliability and energy efficiency. However, because of the diverse industrial-application requirements and large scale of the network, several technical problems still
remain to be solved in analytical IWSN models. Other open issues include optimal sensor-node deployment, localization, security, and interoperability between different IWSN manufacturers. Finally, to cope with RF interference and dynamic/varying wireless-channel conditions in industrial environments, porting a cognitive radio paradigm to a low-power industrial sensor node and developing controlling mechanisms for channel handoff is another challenging area yet to be explored

The main characteristics of a WSN include:
Nodes can easily be relocated
Can automatically handle node failures
Nodes are similar in function and behavior
Easily scalable to grow into larger networks with thousands of nodes
Suitable for harsh environmental conditions since there are no cables and low or no power maintenance
Easy to use; adding a node is as simple as placing and activating it (low or no configuration requirements)
Low power consumption
Very low power consumption for nodes that use batteries or harvest energy

I/O Modules, DAQ
Simulators, Optimizers
Diagnostics, Asset Mgt.
Process Safety
PID, APC
Sensors, Actuators
HMI, OI
DCS, SCADA, Controllers

System Integrators
Asset Management
Project Management
Energy Efficiency
Energy, Power

System integration

System integration (SI) is an IT or engineering process or phase concerned with joining different subsystems or components as one large system. It ensures that each integrated subsystem functions as required.

What is meant by system integration?
In engineering, system integration is defined as the process of bringing together the component subsystems into one system and ensuring that the subsystems function together as a system.

What is an integrator?
The operational amplifier integrator is an electronic integration circuit. Based on the operational amplifier (op-amp), it performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.

What is a V integration?
The process of integration involves creating the connections between these devices (usually through a series of switchers or matrix devices) and then programming software that connects the devices and enables that seamless switching. Creating an audio visual integrated room is a meld of art and science.

What is the meaning of integration?
Integration is the act of bringing together smaller components into a single system that functions as one.

Who are system integrators?
A systems integrator is a person or company that specializes in bringing together component subsystems into a whole and ensuring that those subsystems function together, a practice known as system integration.

What is Si in it?
A systems integrator (SI) is an individual or business that builds computing systems for clients by combining hardware and software products from multiple vendors.

What is system integration testing in software testing?
System Integration Testing(SIT) is a black box testing technique that evaluates the system’s compliance against specified requirements. System Integration Testing is usually performed on subset of system while system testing is performed on a complete system and is preceded by the user acceptance test (UAT).

What is an integrated software?
In the computer industry, integration software is a general term for any software that serves to join together or mediate between two separate and usually already existing programs, applications, or systems.

System integration is defined in engineering as the process of bringing together the component sub-systems into one system (an aggregation of subsystems cooperating so that the system is able to deliver the overarching functionality) and ensuring that the subsystems function together as a system, and in information technology as the process of linking together different computing systems and software applications physically or functionally, to act as a coordinated whole.

The system integrator integrates discrete systems utilizing a variety of techniques such as computer networking, enterprise application integration, business process management or manual programming.

System integration involves integrating existing often disparate systems and is also about adding value to the system, capabilities that are possible because of interactions between subsystems. In the modern world connected by Internet, the role of system integration engineers is important: more and more systems are designed to connect, both within the system under construction and to systems that are already deployed.

A systems integrator is a person or company that specializes in bringing together component subsystems into a whole and ensuring that those subsystems function together, a practice known as system integration. They also solve problems of automation. Systems integrators may work in many fields but the term is generally used in the information technology (IT) field such as computer networking, the defense industry, the mass media, enterprise application integration, business process management or manual computer programming. Data quality issues are an important part of the work of systems integrators

System Integrators in the automation industry typically provide the product and application experience in implementing complex automation solutions. Often, System Integrators are aligned with automation vendors, joining their various System Integrator programs for access to development products, resources and technical support. System integrators are tightly linked to their accounts and often are viewed as the engineering departments for small manufacturers, handling their automation system installation, commissioning and long term maintenance.

Systems engineering is an interdisciplinary field of engineering and engineering management that focuses on how to design and manage complex systems over their life cycles. At its core systems engineering utilizes systems thinking principles to organize this body of knowledge. Issues such as requirements engineering, reliability, logistics, coordination of different teams, testing and evaluation, maintainability and many other disciplines necessary for successful system development, design, implementation, and ultimate decommission become more difficult when dealing with large or complex projects. Systems engineering deals with work-processes, optimization methods, and risk management tools in such projects. It overlaps technical and human-centered disciplines such as industrial engineering, mechanical engineering, manufacturing engineering, control engineering, software engineering, electrical engineering, cybernetics, organizational studies, engineering management and project management. Systems engineering ensures that all likely aspects of a project or system are considered, and integrated into a whole.

The systems engineering process is a discovery process that is quite unlike a manufacturing process. A manufacturing process is focused on repetitive activities that achieve high quality outputs with minimum cost and time. The systems engineering process must begin by discovering the real problems that need to be resolved, and identify the most probable or highest impact failures that can occur – systems engineering involves finding elegant solutions to these problems.

Description

PLC

A programmable logic controller (PLC), or programmable controller is an industrial digital computer which has been ruggedised and adapted for the control of manufacturing processes, such as assembly lines, or robotic devices, or any activity that requires high reliability control and ease of programming and process fault diagnosis.

They were first developed in the automobile industry to provide flexible, ruggedised and easily programmable controllers to replace hard-wired relays and timers. Since then they have been widely adopted as high-reliability automation controllers suitable for harsh environments. A PLC is an example of a “hard” real-time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result.

Programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Some proprietary programming terminals displayed the elements of PLC programs as graphic symbols, but plain ASCII character representations of contacts, coils, and wires were common. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were minimal due to lack of memory capacity. The oldest PLCs used non-volatile magnetic core memory.

More recently, PLCs are programmed using application software on personal computers, which now represent the logic in graphic form instead of character symbols. The computer is connected to the PLC through USB, Ethernet, RS-232, RS-485, or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic. In some software packages, it is also possible to view and edit the program in function block diagrams, sequence flow charts and structured text. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC through a programming board which writes the program into a removable chip such as an EPROM

There are two types of contacts in PLC’s and they are normally open and normally closed switches. A normally open contact means the contact is on when pressed/closed, and a normally closed contact is on when open/not pressed. Contacts represent the states of real world inputs like sensors, switches, if the part is present, empty, full, etc. PLC’s also consist of coils, which are outputs like motors, pumps, lights, timers, etc. The PLC examines inputs and turns coils on or off whenever it is needed. They can also be used as inputs to other rungs in the ladder diagram.

The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems, and networking. The data handling, storage, processing power, and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Desktop computer controllers have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. Operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the controller may not always respond to changes of input status with the consistency in timing expected from PLCs. Desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs

The most basic function of a Programmable logic controller (PLC) is to receive inputs from status components, which can be from sensors or switches. Some of the basic components of a PLC are input modules, a central processing unit, output modules, and a programming device. When an input is activated, some output will also be activated by whatever you told the machine to do. Some examples of this are setting a timer to 10ms, activating the timer and once 10ms have passed a siren goes off. Some advantages to using a PLC over other programming devices are the user doesn’t have to rewire anything, the PLC has very little downtime in between running different programs, the user can program off-line, and PLC’s aren’t time constrained. If the user tells the PLC to perform an output in 10ms, it will perform the output in 10ms unlike other programs like LabView which can have a delay in activation.

The main function of a timer is to keep an output on for a specific length of time. A good example of this is a garage light needing to cut off after 2 minutes to give someone time to go into the house. The three different types of timers that are commonly used are a Delay-OFF, a Delay-ON, and a Delay-ON-Retentive. A Delay-OFF timer activates immediately when turned on, counts down from a programmed time then cuts off, and is cleared when the enabling input is off. A Delay-ON timer is activated by input and starts accumulating time, counts up to a programmed time and then cuts off, and is cleared when the enabling input is turned off. A Delay-ON-Retentive timer is activated by input and starts accumulating time, retains the accumulated value even if the rung goes false, and resets only by a RESET contact.

Counters are primarily used for counting items such as cans going into a box on an assembly line. This is important because once something is filled to its max the item needs to be moved on so something else can be filled. Many companies use counters in PLC’s to count boxes, count how many feet of something is covered, or to count how many pallets are on a truck. There are three types of counters, Up counters, Down counters, and Up/Down counters. Up counters count up to the preset value, turns on the CTU when the preset value is reached, and cleared on reset. Down counters count down from a preset value, turns on CTD when 0 is reached, and cleared on reset. Up/Down counters count up on CU, count down on CD, turns on when CTUD is greater than the preset value is reached, and cleared on reset.

In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are needed, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have 8 to 12 discrete inputs, 4 to 8 discrete outputs, and up to 2 analog inputs. Size is usually about 4″ wide, 3″ high, and 3″ deep. Most such devices include a tiny postage-stamp-sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC, and they still offer robust design and deterministic execution of the logics.

The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold), and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC.

A PLC program is generally executed repeatedly as long as the controlled system is running. The status of physical input points is copied to an area of memory accessible to the processor, sometimes called the “I/O Image Table”. The program is then run from its first instruction rung down to the last rung. It takes some time for the processor of the PLC to evaluate all the rungs and update the I/O image table with the status of outputs. This scan time may be a few milliseconds for a small program or on a fast processor, but older PLCs running very large programs could take much longer (say, up to 100 ms) to execute the program. If the scan time were too long, the response of the PLC to process conditions would be too slow to be useful.

As PLCs became more advanced, methods were developed to change the sequence of ladder execution, and subroutines were implemented. This simplified programming could be used to save scan time for high-speed processes; for example, parts of the program used only for setting up the machine could be segregated from those parts required to operate at higher speed.

Special-purpose I/O modules may be used where the scan time of the PLC is too long to allow predictable performance. Precision timing modules, or counter modules for use with shaft encoders, are used where the scan time would be too long to reliably count pulses or detect the sense of rotation of an encoder. The relatively slow PLC can still interpret the counted values to control a machine, but the accumulation of pulses is done by a dedicated module that is unaffected by the speed of the program execution.

The 5 main steps in one complete scan cycle are reading the inputs, executing the program, processing communication requests, executing CPU diagnostics, and writing to the outputs. To read the inputs, the user writes values to the input image table which are reserved in bytes. When executing the program, the ladder is read from right to left, and top to bottom. When processing communication requests, the user processes any message received from the communications port. To execute the CPU Self-Diagnostic test, check the firmware, check the program, and check the status of the modules

A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O.

Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules are customized for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. Either a special high speed serial I/O link or comparable communication method is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants. Options are also available to mount I/O points directly to the machine and utilize quick disconnecting cables to sensors and valves, saving time for wiring and replacing components.

PLCs may need to interact with people for the purpose of configuration, alarm reporting, or everyday control. A human-machine interface (HMI) is employed for this purpose. HMIs are also referred to as man-machine interfaces (MMIs) and graphical user interfaces (GUIs). A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use programming and monitoring software installed on a computer, with the PLC connected via a communication interface.

PLCs have built-in communications ports, usually 9-pin RS-232, RS-422, RS-485, Ethernet. Various protocols are usually included. Many of these protocols are vendor specific.

Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control And Data Acquisition) system or web browser.

PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations.

PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non- volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays.

Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. The most commonly used programming language is Ladder diagram (LD) also known as Ladder logic. It uses Contact-Coil logic to make programs like an electrical control diagram. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. A model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today.

IEC 61131-3 currently defines five programming languages for programmable control systems: function block diagram (FBD), ladder diagram (LD), structured text (ST; similar to the Pascal programming language), instruction list (IL; similar to assembly language), and sequential function chart (SFC). These techniques emphasize logical organization of operations.

While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization, and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible.

PLCs are well adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems, so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economical. This is due to the lower cost of the components, which can be optimally chosen instead of a “generic” solution, and where the non-recurring engineering charges are spread over thousands or millions of units.

For high volume or very simple fixed automation tasks, different techniques are used. For example, a cheap consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities.

A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware, and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit buses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomical.

Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customized solutions; for example, aircraft flight controls. Single-board computers using semi-customized or fully proprietary hardware may be chosen for very demanding control applications where the high development and maintenance cost can be supported. “Soft PLCs” running on desktop-type computers can interface with industrial I/O hardware while executing programs within a version of commercial operating systems adapted for process control needs.

Programmable controllers are widely used in motion, positioning, and/or torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements.

PLCs may include logic for single-variable feedback analog control loop, a proportional, integral, derivative (PID) controller. A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has been blurred.

PLCs have similar functionality as remote terminal units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs, and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features, and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments.

In recent years “safety” PLCs have started to become popular, either as standalone models or as functionality and safety-rated hardware added to existing controller architectures (Allen-Bradley Guardlogix, Siemens F-series etc.). These differ from conventional PLC types as being suitable for use in safety-critical applications for which PLCs have traditionally been supplemented with hard-wired safety relays. For example, a safety PLC might be used to control access to a robot cell with trapped-key access, or perhaps to manage the shutdown response to an emergency stop on a conveyor production line. Such PLCs typically have a restricted regular instruction set augmented with safety-specific instructions designed to interface with emergency stops, light screens, and so forth. The flexibility that such systems offer has resulted in rapid growth of demand for these controllers.

Industrial control system (ICS) is a general term that encompasses several types of control systems and associated instrumentation used in industrial production technology, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.

Industrial control systems are typically used in industries such as electrical, water, oil, gas and data.

Based on data received from remote stations, automated or operator-driven supervisory commands can be pushed to remote station control devices, which are often referred to as field devices. Field devices control local operations such as opening and closing valves and breakers, collecting data from sensor systems, and monitoring the local

Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controllers and discrete PID controllers to interface to the process plant or machinery. The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA supervisory computer system. However, the real-time control logic or controller calculations are performed by networked modules which connect to the field sensors and actuators.

The SCADA concept was developed as a universal means of remote access to a variety of local control modules, which could be from different manufacturers allowing access through standard automation protocols. In practice, large SCADA systems have grown to become very similar to distributed control systems in function, but using multiple means of interfacing with the plant. They can control large-scale processes that can include multiple sites, and work over large distances. It is one of the most commonly-used types of industrial control systems, however there are concerns about SCADA systems being vulnerable to cyberwarfare/cyberterrorism attacks.

Referring to the functional hierarchy diagram in this article:

Level 1 contains the PLCs or RTUs

Level 2 contains the SCADA software and computing platform.

The SCADA software exists only at this supervisory level as control actions are performed automatically by RTUs or PLCs. SCADA control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow. The SCADA also enables alarm conditions, such as loss of flow or high temperature, to be displayed and recorded. A feedback control loop is directly controlled by the RTU or PLC, but the SCADA software monitors the overall performance of the loop.

 

PLCs can range from small “building brick” devices with tens of I/O in a housing integral with the processor, to large rack-mounted modular devices with a count of thousands of I/O, and which are often networked to other PLC and SCADA systems.

They can be designed for multiple arrangements of digital and analog inputs and outputs (I/O), extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory.

It was in the automotive industry in the USA that the PLC was created. Before the PLC, the control, sequencing, and safety interlock logic for manufacturing automobiles was mainly composed of relays, cam timers, drum sequencers, and dedicated closed-loop controllers. Since these could number in the hundreds or even thousands, the process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire the relays to change their operational characteristics.

When digital computers became available, being general-purpose programmable devices, they were soon applied to control sequential and combinatorial logic in industrial processes. However these early computers required specialist programmers, and stringent operating environmental control for temperature, cleanliness, and power quality. To meet these challenges this the PLC was developed with several key attributes. It would tolerate the shop-floor environment, it would support discrete input and output, and it was easily maintained and programmed.

Control system security is the prevention of intentional or unintentional interference with the proper operation of industrial automation and control systems. These control systems manage essential services including electricity, petroleum production, water, transportation, manufacturing, and communications. They rely on computers, networks, operating systems, applications, and programmable controllers, each of which could contain security vulnerabilities. The 2010 discovery of the Stuxnet worm demonstrated the vulnerability of these systems to cyber incidents.The United States and other governments have passed cyber-security regulations requiring enhanced protection for control systems operating critical infrastructure.

Control system security is known by several other names such as SCADA security, PCN security, industrial network security, and control system cyber security.

Insecurity of industrial automation and control systems can lead consequences in categories such as:

Safety
Environmental impact
Lost production
Equipment damage
Information theft
Company image

Operational Technology is utilized in many sectors and environments, such as:

Oil & Gas
Power and Utilities
Chemicals manufacturing
Water treatment
Waste management
Transportation
Scientific experimentation

An industrial safety system is a counter measure crucial in any hazardous plants such as oil and gas plants and nuclear plants. They are used to protect human, industrial plant, and the environment in case of the process going beyond the allowed control margins.

As the name suggests, these systems are not intended for controlling the process itself but rather protection. Process control is performed by means of process control systems (PCS) and is interlocked by the safety systems so that immediate actions are taken should the process control systems fail.

Process control and safety systems are usually merged under one system, called Integrated Control and Safety System (ICSS). Industrial safety systems typically use dedicated systems that are SIL 2 certified at minimum; whereas control systems can start with SIL 1. SIL applies to both hardware and software requirements such as cards, processors redundancy and voting functions.

Pressure safety valves
Pressure safety valves or PSVs are usually used as a final safety solution when all previous systems fail to prevent any further pressure accumulation and protect vessels from rupture due to overpressure by their designed action.

 

There are three main types of industrial safety systems in process industry:

Process Safety System or Process Shutdown System, (PSS).
Safety Shutdown System (SSS): This includes Emergency Shutdown-(ESD) and Emergency Depressurization-(EDP) Systems.

 

SSS
The safety shutdown system (SSS) shall shut down the facilities to a safe state in case of an emergency situation, thus protecting personnel, the environment and the asset. The safety shutdown system shall manage all inputs and outputs relative to emergency shutdown (ESD) functions (environment and personnel protection). This system might also be fed by signals from the main fire and gas system.

FGS
The main objectives of the fire and gas system are to protect personnel, environment, and plant (including equipment and structures). The FGS shall achieve these objectives by:

Detecting at an early stage, the presence of flammable gas,
Detecting at an early stage, the liquid spill (LPG and LNG),
Detecting incipient fire and the presence of fire,
Providing automatic and/or facilities for manual activation of the fire protection system as required,
Initiating environmental changes to keep liquids below their flash point
Initiating signals, both audible and visible as required, to warn of the detected hazards,
Initiating automatic shutdown of equipment and ventilation if 2 out of 2 or 2 out of 3 detectors are triggered,
Initiating the exhausting system.
EDP
Due to closing ESD valves in a process, there may be some trapped flammable fluids, and these must be released in order to avoid any undesired consequences (such as pressure increase in vessels and piping). For this, emergency depressurization (EDP) systems are used in conjunction with the ESD systems to release (to a safe location and in a safe manner) such trapped fluids.

 

PLC technicians design, program, repair and maintain programmable logic controller (PLC) systems used within manufacturing and service industries ranging from industrial packaging to commercial car washes and traffic lights.

 

PLC technicians are knowledgeable in overall plant systems and the interactions of processes. They install and service a variety of systems including safety and security, energy delivery (hydraulic, pneumatic and electrical), communication, and process control systems. They also install and service measuring and indicating instruments to monitor process control variables associated with PLCs, and monitor the operation of PLC equipment. PLC technicians work with final control devices such as valves, actuators and positioners to manipulate the process medium. They install and terminate electrical, pneumatic and fluid connections. They also work on network and signal transmission systems such as fibre optic and wireless.

Along with the calibration, repair, adjustment and replacement of components, PLC technicians inspect and test the operation of instruments and systems to diagnose faults and verify repairs. They establish and optimize process control strategies, and configure related systems such as Distributed Control Systems (DCSs), Supervisory Control & Data Acquisition (SCADA), and Human Machine Interfaces (HMIs). PLC technicians maintain backups, documentation and software revisions as part of maintaining these computer-based control systems. Scheduled maintenance and the commissioning of systems are also important aspects of the work. PLC technicians consult technical documentation, drawings, schematics and manuals. They may assist engineering in plant design, modification and hazard analysis, and work with plant operators to optimize plant controls.

PLC technicians use hand, power and electronic tools, test equipment, and material handling equipment. They work on a variety of systems including primary control elements, transmitters, analyzers, sensors, detectors, signal conditioners, recorders, controllers and final control elements (actuators, valve positioners, etc.). These instruments measure and control variables such as pressure, flow, temperature, level, motion, force and chemical composition. PLC systems designed and maintained by PLC technicians range from high speed robotic assembly to conveyors, to batch mixers, to DCS and SCADA systems. PLC systems are often found within industrial and manufacturing plants, such as food processing facilities. Alternate job titles include PLC engineer, Automation Technician, Field Technician or Controls Technician.

Automation equipment wholesalers
Industrial manufacturing companies
Water Treatment plants
Nuclear and Hydro Electric Power companies
Pharmaceutical companies
Mining, petrochemical and natural gas companies
Pulp and paper processing companies

Supervisory control and data acquisition (SCADA) is a control system architecture that uses computers, networked data communications and graphical user interfaces for high-level process supervisory management, but uses other peripheral devices such as programmable logic controllers and discrete PID controllers to interface to the process plant or machinery. The operator interfaces which enable monitoring and the issuing of process commands, such as controller set point changes, are handled through the SCADA supervisory computer system. However, the real-time control logic or controller calculations are performed by networked modules which connect to the field sensors and actuators.

 

Human-machine interface
Further information: Graphical user interface
File:Scada Animation.ogv
More complex SCADA animation showing control of four batch cookers
The human-machine interface (HMI) is the operator window of the supervisory system. It presents plant information to the operating personnel graphically in the form of mimic diagrams, which are a schematic representation of the plant being controlled, and alarm and event logging pages. The HMI is linked to the SCADA supervisory computer to provide live data to drive the mimic diagrams, alarm displays and trending graphs. In many installations the HMI is the graphical user interface for the operator, collects all data from external devices, creates reports, performs alarming, sends notifications, etc.

Mimic diagrams consist of line graphics and schematic symbols to represent process elements, or may consist of digital photographs of the process equipment overlain with animated symbols.

Supervisory operation of the plant is by means of the HMI, with operators issuing commands using mouse pointers, keyboards and touch screens. For example, a symbol of a pump can show the operator that the pump is running, and a flow meter symbol can show how much fluid it is pumping through the pipe. The operator can switch the pump off from the mimic by a mouse click or screen touch. The HMI will show the flow rate of the fluid in the pipe decrease in real time.

The HMI package for a SCADA system typically includes a drawing program that the operators or system maintenance personnel use to change the way these points are represented in the interface. These representations can be as simple as an on-screen traffic light, which represents the state of an actual traffic light in the field, or as complex as a multi-projector display representing the position of all of the elevators in a skyscraper or all of the trains on a railway.

A “historian”, is a software service within the HMI which accumulates time-stamped data, events, and alarms in a database which can be queried or used to populate graphic trends in the HMI. The historian is a client that requests data from a data acquisition server.

 

An important part of most SCADA implementations is alarm handling. The system monitors whether certain alarm conditions are satisfied, to determine when an alarm event has occurred. Once an alarm event has been detected, one or more actions are taken (such as the activation of one or more alarm indicators, and perhaps the generation of email or text messages so that management or remote SCADA operators are informed). In many cases, a SCADA operator may have to acknowledge the alarm event; this may deactivate some alarm indicators, whereas other indicators remain active until the alarm conditions are cleared.

Alarm conditions can be explicit—for example, an alarm point is a digital status point that has either the value NORMAL or ALARM that is calculated by a formula based on the values in other analogue and digital points—or implicit: the SCADA system might automatically monitor whether the value in an analogue point lies outside high and low- limit values associated with that point.

Examples of alarm indicators include a siren, a pop-up box on a screen, or a coloured or flashing area on a screen (that might act in a similar way to the “fuel tank empty” light in a car); in each case, the role of the alarm indicator is to draw the operator’s attention to the part of the system ‘in alarm’ so that appropriate action can be taken.

“Internet of things”
With the commercial availability of cloud computing, SCADA systems have increasingly adopted Internet of things technology to significantly reduce infrastructure costs and increase ease of maintenance and integration. As a result, SCADA systems can now report state in near real-time and use the horizontal scale available in cloud environments to implement more complex control algorithms than are practically feasible to implement on traditional programmable logic controllers. Further, the use of open network protocols such as TLS inherent in the Internet of things technology, provides a more readily comprehensible and manageable security boundary than the heterogeneous mix of proprietary network protocols typical of many decentralized SCADA implementations. One such example of this technology is an innovative approach to rainwater harvesting through the implementation of real time controls (RTC).

This decentralization of data also requires a different approach to SCADA than traditional PLC based programs. When a SCADA system is used locally, the preferred methodology involves binding the graphics on the user interface to the data stored in specific PLC memory addresses. However, when the data comes from a disparate mix of sensors, controllers and databases (which may be local or at varied connected locations), the typical 1 to 1 mapping becomes problematic. A solution to this is data modeling, a concept derived from object oriented programming.

In a data model, a virtual representation of each device is constructed in the SCADA software. These virtual representations (“models”) can contain not just the address mapping of the device represented, but also any other pertinent information (web based info, database entries, media files, etc.) that may be used by other facets of the SCADA/IoT implementation. As the increased complexity of the Internet of things renders traditional SCADA increasingly “house-bound,” and as communication protocols evolve to favor platform-independent, service-oriented architecture (such as OPC UA), it is likely that more SCADA software developers will implement some form of data modeling.

 

Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, standardized as IEC 61158.

A complex automated industrial system — such as manufacturing assembly line — usually needs a distributed control system—an organized hierarchy of controller systems—to function. In this hierarchy, there is usually a Human Machine Interface (HMI) at the top, where an operator can monitor or operate the system. This is typically linked to a middle layer of programmable logic controllers (PLC) via a non-time-critical communications system (e.g. Ethernet). At the bottom of the control chain is the fieldbus that links the PLCs to the components that actually do the work, such as sensors, actuators, electric motors, console lights, switches, valves and contactors.

 

Fieldbus can be used for systems which must meet safety-relevant standards like IEC 61508 or EN 954-1. Depending on the actual protocol, fieldbus can provide measures like counters, CRCs, echo, timeout, unique sender and receiver IDs or cross check. Ethernet/IP and SERCOS III both use the CIP Safety protocol, Ethernet Powerlink uses openSAFETY, while FOUNDATION Fieldbus and Profibus (PROFIsafe) can address SIL 2 and SIL 3 process safety applications.

 

Advanced process control

 

APC: Advanced process control
ARC: Advanced regulatory control, including feedforward, adaptive gain, override, logic, fuzzy logic, sequence control, device control, inferentials, and custom algorithms; usually implies DCS-based.
Base-Layer: Includes DCS, SIS, field devices, and other DCS subsystems, such as analyzers, equipment health systems, and PLCs.
BPCS: Basic process control system (see “base-layer”)
DCS: Distributed control system, often synonymous with BPCS
MPO: Manufacturing planning optimization
MPC: Multivariable Model predictive control
SIS: Safety instrumented system
SME: Subject matter expert

Control Applications
Automation and Remote Control
Distributed Control System
Electric motors
Industrial Control Systems
Mechatronics
Motion control
Process Control
Robotics
Supervisory control (SCADA)

In control theory Advanced process control (APC) refers to a broad range of techniques and technologies implemented within industrial process control systems. Advanced process controls are usually deployed optionally and in addition to basic process controls. Basic process controls are designed and built with the process itself, to facilitate basic operation, control and automation requirements. Advanced process controls are typically added subsequently, often over the course of many years, to address particular performance or economic improvement opportunities in the process.

Process control (basic and advanced) normally implies the process industries, which includes chemicals, petrochemicals, oil and mineral refining, food processing, pharmaceuticals, power generation, etc. These industries are characterized by continuous processes and fluid processing, as opposed to discrete parts manufacturing, such as automobile and electronics manufacturing. The term process automation is essentially synonymous with process control.

Process controls (basic as well as advanced) are implemented within the process control system, which usually means a distributed control system (DCS), programmable logic controller (PLC), and/or a supervisory control computer. DCSs and PLCs are typically industrially hardened and fault-tolerant. Supervisory control computers are often not hardened or fault-tolerant, but they bring a higher level of computational capability to the control system, to host valuable, but not critical, advanced control applications. Advanced controls may reside in either the DCS or the supervisory computer, depending on the application. Basic controls reside in the DCS and its subsystems, including PLCs.

 

Manufacturing

Factory
Heavy industry
Light industry
Mass production
Production line

Aerospace industry
Automotive industry
Chemical industry
Computer industry
Electronics industry
Food processing industry
Garment industry
Pharmaceutical industry
Pulp and paper industry
Toy industry

Production technology
Industrial robot
Computer-aided manufacturing
Computer Integrated Manufacturing
Production equipment control
Computer numerically controlled
Distributed Control System
Fieldbus control system
PLCs / PLD
Advanced Planning & Scheduling
Scheduling (production processes)
SCADA supervisory control and data acquisition
computerized maintenance management system (CMMS)
Packaging and labeling
Machinery
Machinery
Production line
Assembly line
Conveyor belt
Woodworking machinery
Metalworking machinery
Textile machinery
Equipment manufacturer

 

Control system – a device, or set of devices to manage, command, direct or regulate the behavior of other devices or system.
Industrial control system (ICS) – encompasses several types of control systems used in industrial production, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as skid-mounted programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.
Industrialization – period of social and economic change that transforms a human group from an agrarian society into an industrial one.
Numerical control (NC) – refers to the automation of machine tools that are operated by abstractly programmed commands encoded on a storage medium, as opposed to controlled manually via handwheels or levers, or mechanically automated via cams alone.
Robotics – the branch of technology that deals with the design, construction, operation, structural disposition, manufacture and application of robots and computer systems for their control, sensory feedback, and information processing.

 

Autonomous automation – autonomous software agents to adapt the controllers of computer controlled industrial machinery and processes
Building automation – advanced functionality provided by the control system of a building. A building automation system (BAS) is an example of a distributed control system.
Home automation – control system of a home.

 

Artificial neural network (ANN) – mathematical model or computational model that is inspired by the structure or functional aspects of biological neural networks.
Human machine interface (HMI) – operator level local control panel that control monitors the field devices,
Laboratory information management system (LIMS) – software package that offers a set of key features that support a modern laboratory’s operations.
Industrial control system – encompasses several types of control systems used in industrial production, including supervisory control and data acquisition (SCADA) systems, distributed control systems (DCS), and other smaller control system configurations such as skid-mounted programmable logic controllers (PLC) often found in the industrial sectors and critical infrastructures.
Distributed control system (DCS) – control system usually of a manufacturing system, process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers.
Manufacturing execution system (MES) – system that manages manufacturing operations in a factory, including management of resources, scheduling production processes, dispatching production orders, execution of production orders, etc.
Programmable automation controller (PAC) – digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures.
Programmable logic controller (PLC)A Programmable Logic Controller, PLC or Programmable Controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. The abbreviation “PLC” and the term “Programmable Logic Controller” are registered trademarks of the Allen-Bradley Company (Rockwell Automation). PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is an example of a hard real time system since output results must be produced in response to input conditions within a limited time, otherwise unintended operation will result. –
Supervisory control and data acquisition (SCADA) – generally refers to industrial control systems (ICS): computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:* Industrial processes include those of manufacturing, production, power generation, fabrication, and refining, and may run in continuous, batch, repetitive, or discrete modes.
Simulation#Engineering Technology simulation or Process simulation –

Wireless Networks for Industrial Automation
Wireless sensor networks
The main features of WSNs, as could be deduced by the general description given in the previous sections, are:
scalability with respect to the number of nodes in the network, self-organization, self-healing, energy efficiency, a sufficient degree of connectivity among nodes, low-complexity, low cost and size of nodes. Those protocol architectures and technical solutions providing such features can be considered as a potential framework for the creation of these networks, but, unfortunately, the definition of such a protocol architecture and technical solution is not simple, and the research still needs to work on it.

The massive research on WSNs started after the year 2000. However, it took advantage of the outcome of the research on wireless networks performed since the second half of the previous century. In particular, the study of ad hoc networks attracted a lot of attention for several decades, and some researchers tried to report their skills acquired in the field of ad hoc networks, to the study of WSNs. According to some general definitions, wireless ad hoc networks are formed dynamically by an autonomous system of nodes connected via wireless links without using an existing network infrastructure or centralized
administration. Nodes are connected through “ad hoc” topologies, set up and cleared according to user needs and temporary conditions. Apparently, this definition can include WSNs. However, this is not true. This is the list of main features for wireless ad hoc networks: unplanned and highly dynamical; nodes are “smart” terminals (laptops, etc.); typical applications include realtime or non-realtime data, multimedia, voice; every node can be either source or destination of information; every node can be a router toward other nodes; energy is not the most relevant matter; capacity is the most relevant matter.

Apart from the very first item, which is common to WSNs, in all other cases there is a clear distinctionbetween WSNs and wireless ad hoc networks. In WSNs, nodes are simple and low-complexity devices;the typical applications require few bytes sent periodically or upon request or according to some external event; every node can be either source or destination of information, not both; some nodes do not play the role of routers; energy efficiency is a very relevant matter, while capacity is not for most applications.Therefore, WSNs are not a special case of wireless ad hoc networks. Thus, a lot of care must be used when considering protocols and algorithms which are good for ad hoc networks, and using them in the context of WSNs

Sensor Technologies functions in highly powered high-speed and low-cost electronic circuits. In a developing world, the need for sensor technologies with a view to support systems automation, security and information dissemination is on the increase. The application of sensor technology in diverse ways has eventually enforced the increase of the requirement for the implementation. The design of smart homes and environment is made possible by the use of sensor devices. Sensor technologies in this respect are expected to provide novel approaches and solutions as required. Sensor can be considered as complex devices that can be used to detectand respond to signals being produced. A sensor primarily converts physical parameters into signal. These parameters can be; temperature, humidity, and speed. The signal produced can be measured electronically. When deciding on a particular sensor to use in a given task, the following consideration will be employed; Cost, Range, Accuracy, Environmental consideration, and Resolution The Industrial Wireless Sensor Networks IWSNs have the potential to improve productivity of industrial systems by providing greater awareness, control, and integration of business processes. Despite of the great progress on development of IWSNs, quite a few issues still need to be explored in the future. For example, an efficient deployment of IWSNs in the real world is highly dependent on the ability to devise analytical models to evaluate and predict IWSNs performance characteristics, such as communication latency and reliability and energy efficiency. However, because of the diverse industrial-application requirements and large scale of the network, several technical problems still
remain to be solved in analytical IWSN models. Other open issues include optimal sensor-node deployment, localization, security, and interoperability between different IWSN manufacturers. Finally, to cope with RF interference and dynamic/varying wireless-channel conditions in industrial environments, porting a cognitive radio paradigm to a low-power industrial sensor node and developing controlling mechanisms for channel handoff is another challenging area yet to be explored

The main characteristics of a WSN include:
Nodes can easily be relocated
Can automatically handle node failures
Nodes are similar in function and behavior
Easily scalable to grow into larger networks with thousands of nodes
Suitable for harsh environmental conditions since there are no cables and low or no power maintenance
Easy to use; adding a node is as simple as placing and activating it (low or no configuration requirements)
Low power consumption
Very low power consumption for nodes that use batteries or harvest energy

I/O Modules, DAQ
Simulators, Optimizers
Diagnostics, Asset Mgt.
Process Safety
PID, APC
Sensors, Actuators
HMI, OI
DCS, SCADA, Controllers

System Integrators
Asset Management
Project Management
Energy Efficiency
Energy, Power

System integration

System integration (SI) is an IT or engineering process or phase concerned with joining different subsystems or components as one large system. It ensures that each integrated subsystem functions as required.

What is meant by system integration?
In engineering, system integration is defined as the process of bringing together the component subsystems into one system and ensuring that the subsystems function together as a system.

What is an integrator?
The operational amplifier integrator is an electronic integration circuit. Based on the operational amplifier (op-amp), it performs the mathematical operation of integration with respect to time; that is, its output voltage is proportional to the input voltage integrated over time.

What is a V integration?
The process of integration involves creating the connections between these devices (usually through a series of switchers or matrix devices) and then programming software that connects the devices and enables that seamless switching. Creating an audio visual integrated room is a meld of art and science.

What is the meaning of integration?
Integration is the act of bringing together smaller components into a single system that functions as one.

Who are system integrators?
A systems integrator is a person or company that specializes in bringing together component subsystems into a whole and ensuring that those subsystems function together, a practice known as system integration.

What is Si in it?
A systems integrator (SI) is an individual or business that builds computing systems for clients by combining hardware and software products from multiple vendors.

What is system integration testing in software testing?
System Integration Testing(SIT) is a black box testing technique that evaluates the system’s compliance against specified requirements. System Integration Testing is usually performed on subset of system while system testing is performed on a complete system and is preceded by the user acceptance test (UAT).

What is an integrated software?
In the computer industry, integration software is a general term for any software that serves to join together or mediate between two separate and usually already existing programs, applications, or systems.

System integration is defined in engineering as the process of bringing together the component sub-systems into one system (an aggregation of subsystems cooperating so that the system is able to deliver the overarching functionality) and ensuring that the subsystems function together as a system, and in information technology as the process of linking together different computing systems and software applications physically or functionally, to act as a coordinated whole.

The system integrator integrates discrete systems utilizing a variety of techniques such as computer networking, enterprise application integration, business process management or manual programming.

System integration involves integrating existing often disparate systems and is also about adding value to the system, capabilities that are possible because of interactions between subsystems. In the modern world connected by Internet, the role of system integration engineers is important: more and more systems are designed to connect, both within the system under construction and to systems that are already deployed.

A systems integrator is a person or company that specializes in bringing together component subsystems into a whole and ensuring that those subsystems function together, a practice known as system integration. They also solve problems of automation. Systems integrators may work in many fields but the term is generally used in the information technology (IT) field such as computer networking, the defense industry, the mass media, enterprise application integration, business process management or manual computer programming. Data quality issues are an important part of the work of systems integrators

System Integrators in the automation industry typically provide the product and application experience in implementing complex automation solutions. Often, System Integrators are aligned with automation vendors, joining their various System Integrator programs for access to development products, resources and technical support. System integrators are tightly linked to their accounts and often are viewed as the engineering departments for small manufacturers, handling their automation system installation, commissioning and long term maintenance.

Systems engineering is an interdisciplinary field of engineering and engineering management that focuses on how to design and manage complex systems over their life cycles. At its core systems engineering utilizes systems thinking principles to organize this body of knowledge. Issues such as requirements engineering, reliability, logistics, coordination of different teams, testing and evaluation, maintainability and many other disciplines necessary for successful system development, design, implementation, and ultimate decommission become more difficult when dealing with large or complex projects. Systems engineering deals with work-processes, optimization methods, and risk management tools in such projects. It overlaps technical and human-centered disciplines such as industrial engineering, mechanical engineering, manufacturing engineering, control engineering, software engineering, electrical engineering, cybernetics, organizational studies, engineering management and project management. Systems engineering ensures that all likely aspects of a project or system are considered, and integrated into a whole.

The systems engineering process is a discovery process that is quite unlike a manufacturing process. A manufacturing process is focused on repetitive activities that achieve high quality outputs with minimum cost and time. The systems engineering process must begin by discovering the real problems that need to be resolved, and identify the most probable or highest impact failures that can occur – systems engineering involves finding elegant solutions to these problems.