Sum-of-Squares Design Method for Four-Parameter Lag-Lead Compensator

The four-parameter lag-lead compensator design has received much attention in the last two decades. However, most approaches have been either trial-and-error or only for special cases. This paper presents a non-trial-and-error design method for four-parameter lag-lead compensators. Here, the compensator design problem is formulated into a polynomial function optimization problem and solved by using the recently developed sum-of-squares (SOS) techniques. This result not only provides a useful design method but also shows the power of the SOS techniques.