Stabilization of the Mechanical Dynamics of a Road Load Simulator Using Classical Control Techniques

Abstract

The open-loop transfer function of a complex hydrostatic pump-motor dynamometer system was derived from an analysis of the dynamics of the individual components. Many system components exhibit non-linearities; however, internal feedback mechanisms contribute to linearization of sub-systems. The resulting model, which was in good agreement with the system's open-loop performance, was used to predict the behaviour of the closed-loop system, this indicated that the system would be unstable. Classical control theory was used to analyse the performance of a number of stabilizing control strategies, with root locus plots, Bode diagrams and Nichols charts being used to assess the resultant performance. A lead compensation, designed as a differential controller, combined with a bi-linear gain was predicted to provide acceptable speed control. The performance of the system with this controller installed was found to satisfy the design requirements of speed of response, limited overshoot and zero steady-state error.