ABSTRACT
This chapter discusses the frequency response methods for designing compensators for feedback control systems. Frequency response methods predate the root locus method and the time-domain design methods. These methods base the controller design on the frequency response of the loop transfer function, which maybe empirically obtained. The frequency response of a system can be graphed in multiple ways. The two most common representations are: the Bode plot and the Nyquist or Polar plot. The chapter reviews the plotting of frequency response and the associated performance metrics. The measures of performance used with frequency response design methods include gain and phase margins, system error constants, sensitivity and complementary sensitivity functions, and so on. The Bode plot serves as a main design tool for the frequency response design method in control systems. The chapter presents a comparison of the step responses for the various controller designs.
