# PID Controller

A proportional–integral–derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs.

The PID controller calculation (algorithm) involves three separate constant parameters, and is accordingly sometimes called three-term control: the proportional, the integral and derivative values, denoted P, I, and D. Heuristically, these values can be interpreted in terms of time: P depends on the present error, I on the accumulation of past errors, and D is a prediction of future errors, based on current rate of change. The weighted sum of these three actions is used to adjust the process via a control element such as the position of a control valve, or the power supplied to a heating element.

In the absence of knowledge of the underlying process, a PID controller has historically been considered to be the best controller. By tuning the three parameters in the PID controller algorithm, the controller can provide control action designed for specific process requirements. The response of the controller can be described in terms of the responsiveness of the controller to an error, the degree to which the controller overshoots the setpoint and the degree of system oscillation. Note that the use of the PID algorithm for control does not guarantee optimal control of the system or system stability.

Some applications may require using only one or two actions to provide the appropriate system control. This is achieved by setting the other parameters to zero. A PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions. PI controllers are fairly common, since derivative action is sensitive to measurement noise, whereas the absence of an integral term may prevent the system from reaching its target value due to the control action.

### Other articles related to "pid controller, pid, controller":

Classical Control Theory - PID Controller
... For more details on this topic, see PID controller ... The PID controller is probably the most-used feedback control design ... PID is an acronym for Proportional-Integral-Derivative, referring to the three terms operating on the error signal to produce a control signal ...
PID Controller - Alternative Nomenclature and PID Forms - Pseudocode
... Here is a simple software loop that implements a PID algorithm previous_error = 0 integral = 0 start error = setpoint - measured_value integral = integral + error*dt derivative = (error ...
Feedback - Applications - Control Theory
... Further information PID controller The most common general-purpose controller using a control-loop feedback mechanism is a proportional-integral-derivative (PID) controller ... Heuristically, the terms of a PID controller can be interpreted as corresponding to time the proportional term depends on the present error, the integral term on the accumulation of past errors, and the derivative ...