Control actions (P controller, PI controller,PID controller)

The Control Actions An automatic controller compares the actual value of the system output with the reference input (desired value), determines the deviation, and produces a control signal that will reduce the deviation to zero or a small value. The manner in which the automatic controller produces the control signal is called the control action. The controllers may be classified according to their control actions as  1) Proportional controllers 2) Proportional-plus- integral controllers 3) Proportional-plus-integral-plus-derivative controllers A two position controller has two fixed positions usually on or off. A proportional control system is a feedback control system in which the output forcing function is directly proportional to error. A integral control system is a feedback control system in which the output forcing function is directly proportional to the first time integral of error. A proportional-plus-integral control system is a feedback control system in whi...