A s-plane analytic technique for lead-lag controller design

In this paper an analytic design technique for a lead-lag controller to satisfy specifications for transient and steady state response of a plant is proposed. Based on the s-plane, three closed loop roots after lead-lag compensation are forced to line up on one vertical line, then the prefiltering technique is used to cancel out undesired effects of the zero of the lead controller to satisfy the settling time and percent overshoot. The lead-lag controller values are analytically calculated by equating two characteristic equations: one is formed from desired root locations the authors specify based on their design criteria, and another one is formed from a nominal control structure. Thus the calculation of values of controllers are so straight forward that one can readily generate a lead-lag controller to satisfy given specifications. Different plant models are shown to test the proposed technique