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A block diagram of a PID controller in a feedback loop. r(t) is the desired process variable (PV) or setpoint (SP), and y(t) is the measured PV. The distinguishing feature of the PID controller is the ability to use the three control terms of proportional, integral and derivative influence on the controller output to apply accurate and optimal ...
A block diagram of a PID controller in a feedback loop, r(t) is the desired process value or "set point", and y(t) is the measured process value. A proportional–integral–derivative controller (PID controller) is a control loop feedback mechanism control technique widely used in control systems.
The proportional control concept is more complex than an on–off control system such as a bi-metallic domestic thermostat, but simpler than a proportional–integral–derivative (PID) control system used in something like an automobile cruise control. On–off control will work where the overall system has a relatively long response time, but ...
In cybernetics and control theory, a setpoint (SP; [1] also set point) is the desired or target value for an essential variable, or process value (PV) of a control system, [2] which may differ from the actual measured value of the variable.
A typical application is a PID controller fed by a flow meter and using a control valve as the final control element. The DCS sends the setpoint required by the process to the controller which instructs a valve to operate so that the process reaches and stays at the desired setpoint. (see 4–20 mA schematic for example).
Classical control theory uses the Laplace transform to model the systems and signals. The Laplace transform is a frequency-domain approach for continuous time signals irrespective of whether the system is stable or unstable.
During the Industrial Revolution in the 18th century, there was a growing need for precise control over boiler pressure in steam engines. In the 1930s, pneumatic and electronic controllers, such as PID (Proportional-Integral-Derivative) controllers, were breakthrough innovations that laid the groundwork for modern control theory.
A control loop is the fundamental building block of control systems in general and industrial control systems in particular. It consists of the process sensor, the controller function, and the final control element (FCE) which controls the process necessary to automatically adjust the value of a measured process variable (PV) to equal the value of a desired set-point (SP).