Automatic Tuning of PID Controllers

Relay feedback control has been one of the key instruments used in the automatic tuning of proportional integral derivative (PID) controllers. Its application is associated with the identification of process frequency response information via the self‐generated excitation signals in a closed‐loop operation. This chapter discusses the automatic tuning of PID controllers where the process frequency response information is obtained from relay feedback experiments and the PID controllers are designed using the design methods. It discusses relay feedback control systems in combination with hysteresis or with an integrator. Simulink tutorials are presented for both cases, which is convenient for simulation studies and experimental validations. The chapter also presents examples to show the estimation of frequency response of the system using the fast Fourier transform with relay feedback control data in a noisy environment. It further introduces a model based approach for the estimation of process frequency response based on the input and output data collected from relay feedback control.