Fig. 1 – Structure of the PID controller with one output U,for the control variable, and two inputs: R, for the set-point,and Y, for the controlled variable. Input to the process ismanipulated variable w defined by the output of actuatorAC. For ideal case, considered in this paper, AC = 1. Loaddisturbance is defined by dinand output disturbance,simulating also measurement noise, is defined by n.