High performance PID control of a cascade tanks system as an example for control teaching

A detailed analysis of PID level control in the second tank of the cascade of two tanks is performed with respect to both, load disturbance attenuation and set-point change. Approximate formulas for extrema of time responses and for certain performance indices are derived, giving guidelines for controller settings. A simple method of choosing controller parameters is proposed that bases on time scale separation. For a reasonable transfer from one operating point to another, under control signal limitations, command signal generators with a feedforward from the reference are proposed and the effect of anti-windup controller augmentation is examined.