High performance single tank level control as an example for control teaching

A detailed analysis of a PI tank level control is performed with respect to both load disturbance attenuation and set-point change. Certain performance indices are given providing guidelines for achievable accuracy and controller settings. Exact formulas for extrema of time responses are derived, which use a novel parametrization of system poles. For transfer between equilibria under control signal limitations, set-point generators with a feed-forward from the reference signal are proposed. The effect of an anti-windup controller augmentation is examined. A method based on solution of the non-linear differential equation describing the tank draining is proposed for a tank model identification. Moreover, invariance of the control system properties with respect to the actual equilibrium is highlighted.