Stability Determination of Retarded Linear Control System Using Dual-Locus-Diagram Technique

Abstract

This paper first reviews in brief, the different methods presented in the last ten years and then outlines the Nyquist stability criterion for linear control systems with time-delay, using dual-locus diagram technique. The variation of the loopgain and time-delay are investigated when the time-delay occurs in the forward loop or the feedback-loop or both. The criterion employs a delay chart prepared beforehand and only requires the plotting of a simple curve derived from the open-loop transfer function. The stability condition of a simple control system is used to illustrate the method.