Lead/lag compensator design for unstable processes based on gain and phase margin specifications

This paper describes lead/lag compensators tuning method based on gain and phase margin specifications for two kinds of unstable processes. A simple and effective graphic method is used to solve a set of nonlinear coupled equations. The solutions are determined from the intersections of the two kinds of curves constructed from gain and phase margin specifications. The results are applied to the tuning of the lead/lag compensator. Examples are provided for illustration.