The use of the PID algorithm does not guarantee optimal control of the system or its control stability (see § Limitations, below). PI controllers are fairly common in applications where derivative action would be sensitive to measurement noise, but the integral term is often needed for the system to reach its target value. This is achieved by setting the unused parameters to zero and is called a PI, PD, P or I controller in the absence of the other control actions. A PID controller continuously calculates an error value e ( t ) Selective use of control terms Īlthough a PID controller has three control terms, some applications need only one or two terms to provide appropriate control. r( t) is the desired process value or setpoint (SP), and y( t) is the measured process value (PV).Ī proportional–integral–derivative controller ( PID controller or three-term controller) is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control.
A block diagram of a PID controller in a feedback loop.
