A Design Method for the Real Order Phase Lead-Lag Compensator with a Reference Model

Abstract

This paper proposes a design method for the real order phase lead-lag compensator to control the controlled object having a higher order lag element and a dead time. In this method, a reference model of very simple open-loop transfer function is introduced. A close relation between the resonance peak Mp of frequency response and the overshoot of the response to unit step input is shown in this model. The desgin procedure which makes the frequency characteristics of the objected open-loop system close as precisely as possible to one of the reference model is presented. The frequency chracteristics of objected system are designed to satisfy the specifid quantities such as phase margin, value of Mp and gain margin. The condition that the gain-phase plot of the open-loop system is tangent to the constant M locus in the Nichols chart is treated especially. By this method, the overshoot of the step response to reference input is able to consider to be the specification in stead of the resonance peak Mp. Finally, the effectiveness of the design method is approved by examples.