Tag: Automation
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How Controllers are used in Industrial Automation Systems
In many process control systems, microprocessor based programmable logic controllers are used for decision making due to the sophistication of the system and the large number of process variables involved. The PLC can be configured to receive a small number of inputs (both analog and digital) and control a small number of outputs or the…
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Types and Operations of Wired Ethernet Networks
Ethernet plays an important role as a communication platform for automation systems. The Key strength of Ethernet is in its ability to run many protocols simultaneously on the same network. Ethernet enables flexibility, scalability and performance of industrial networks in a way not seen before in automated systems. Principle of Operation of Ethernet Network Ethernet…
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Basic Features of Controller Area Network (CAN)
Controller Area Network (CAN) is a serial communication protocol developed primarily for applications in the automotive industry. It is also capable of offering good performance in other time-critical industrial applications. The CAN protocol is optimized for short messages and uses a carrier sense multiple access (CSMA)/Arbitration message priority (AMP) medium access control technique. Therefore CAN…
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Technical Aspects of Foundation Fieldbus
Foundation fieldbus (FF) is an all-digital, serial, two-way communication system for industrial applications. Foundation fieldbus specifications include two different configurations: H1 and HSE. H1 Foundation Fieldbus (FF) H1 FF communication system is mainly applied to distributed continuous process control; running at 31.25 kbps. It connects digital field equipment such as sensors, actuators and inputs/outputs allowing…
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Topological Network Structures used in Fieldbus Systems
Topology is an important property of fieldbus. It is employed in the selection and definition of the best and suitable physical layout of the fieldbus network. The physical layer of the fieldbus has to meet somewhat demanding requirements like immunity to electromagnetic disturbances, robustness, intrinsic safety for hazardous areas, etc. The most important topologies for…
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Direct Digital Control (DDC)
In direct digital control (DDC) a single computer is able to carry out PID control for multiple loops at the same time make that loop data accessible between loops for purposes of cascade control, feedforward control, ratio control or any other control strategy. The DDC controller is also accessible on networks like ethernet for operational…
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Feedforward Control
Feedforward control is based on principle of pre-emptive load counter-action i.e. if all major loads (i.e. disturbances) on a process variable are monitored, and their effects on that process variable are well-understood, a control system programmed to take the appropriate action based on load changes will shield the process variable (PV) from any adverse effect.…
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Benefits of Cascade Control
We know very well that closed loop control provides increased performance over open loop control. So it would be rational to expect benefits from adding inner control loop around plant items that have degrading overall performance. The Figure (a) below illustrates a typical example of a cascade control: In Figure (a) above, the outer loop…
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The Basics of Ladder Diagrams for Programming PLCs
The ladder diagrams are universally used as a symbolic and schematic way to represent the interconnection between the elements in a Programmable Logic Controller (PLC). The ladder network is also used as a tool for programming the operation of PLC. The elements are interconnected between the supply lines for each step in the control process…
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Basic Features of Distributed Control Systems (DCS)
In distributed control system, each process has its own separate controller located at the site. These local controllers are interconnected via a local area network so that all controllers on the network can be monitored or reprogrammed from a single supervisory computer. Once programmed, each process is essentially operating independently. Distributed control systems provides a…