Tag: control systems
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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…
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Proportional-Integral-Derivative (PID) Control Systems
Proportional-Integral-Derivative For processes that are able to operate with continuous cycling, the relatively inexpensive two position controller is sufficient. For processes that cannot tolerate continuous cycling, a proportional controller is used. For processes that tolerate neither cycling nor offset error, a proportional plus integral/reset controller can be used. For processes that require improved stability and…
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Proportional plus Derivative (PD) Control System
Proportional plus derivative (rate) control is a control mode in which a derivative section is added to the proportional controller. This derivative section responds to the rate of change of the error signal, not the amplitude as with the integral control; this derivative action responds to the rate of change the instant it starts. This…
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Why you should replace your old DCS systems with modern ones
To keep up with evolving technology manufacturers need to upgrade their legacy Distributed Control Systems (DCS). This might be a challenging task to undertake and at a cost to the company, but in the long run the benefits outweigh the costs of doing the upgrade. The legacy DCS systems faces increased components failure that leads…
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Proportional Plus Integral (PI) Control System
This type of control is combination of two control modes, proportional and integral (reset). The Combining of the two modes results in gaining the advantages and compensating for the disadvantages of the two individual control modes. The main advantage of the proportional control is that an immediate proportional output is produced as soon as an…
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Basic Features of Programmable Logic Controllers (PLCs)
Introduction to Programmable Logic Controllers What is a Programmable Logic Controller? A PLC is a user friendly; microprocessor-based specialized equipment that carries out many types of control functions with levels of complexity for use in industrial automation applications. Its objective is to monitor crucial process parameters and adjust process operations accordingly. A PLC can be…
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Integral (Reset) Control Systems
Integral (Reset) control Reset/Integral control describes a controller in which the output rate of change is dependent on the magnitude of the input. Specifically, a smaller amplitude input causes a slower rate of change of the output. This controller is termed to as integral controller because it approximates the mathematical function of integration. This integral…
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Proportional Control Systems
The control mode In the proportional control mode, the final control element is throttled to various positions that are dependent on the process systems conditions. The controller operates within a band that is between the 0 % output point and the 100 % output point and where the output of the controller is proportional to…
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Process Time Lags and Stability of Automatic Control Systems
Processes have the characteristics of delaying and retarding changes in the values of the process variables. Process time lags generally describe these process delays and retardations. Process time lags are caused by three properties of the process. They include: Capacitance Resistance Transportation time Capacitance is the ability of a process to store energy. This energy-storing…