Application of describing function technique to idle speed control

This paper aims at providing a simple solution to the idle speed control problem. The controller design method is systematic. The method is based on obtaining a describing function model of the I.C. engine followed by designing a classical controller via an algebraic approach. The application of the controller design method to an uncertain automobile engine with time-delay revealed satisfactory results. The performance of the controller is compared with one other procedure previously reported in the open literature. Stability is demonstrated by successful generation of describing function models of the final nonlinear closed-loop system.