A discrete characteristic locus design for a multichannel structural test system

Abstract

Structural tests are carried out in the automotive and aerospace industries to assess fatigue and vibration properties of engineering structures. Very often the multivariable nature of these tests is ignored and a sequential loop closure scheme is used with PID controllers in each loop. Earlier work has focused on the application of continuous-time Nyquist Array and Characteristic Locus methods to such tests. This paper extends that work by considering a discrete design approach to the Characteristic Locus method. The design process for a two-input two-output system and subsequent implementation on a beam and vibrator rig is described. With modest computational hardware, excellent results are obtained and shown to be superior to those obtained from the implementation of a discretised continuous-time Characteristic Locus controller.