ABSTRACT
This chapter describes the basic topics of proportional, integral, derivative (PID) control. It presents how PID controllers operate and why they have prevailed in the field of industrial control, without having appeared as something more effective than their digital implementation. A feedback controller is designed to produce an "output", which acts correctively in one process, in order to lead a measured process variable to the desired value, known as the set point. All the feedback controllers determine their output by taking into account the error between the desired and the measured actual value of the controlled variable. A PID controller implements the same function as a thermostat, but determines the output with a more complex control algorithm. In the case of programmable logic controllers (PLCs), PID control is implemented in two ways: In the first case, the PID algorithm is integrated in the programming software of the PLC and is called as a subroutine.
