A comparison of multivariable control and sequential loop closure control in a dynamic structural test system-design and implementation

Structural test systems are used in aerospace and automotive industries to investigate the fatigue and vibration properties of engineering structures. Control schemes currently employed in these tests often ignore their inherent multivariable nature, using sequential closure of an array of PID loops to control the test. Previous work of Pratt et al. (1991, 1993) has investigated the design and implementation of multivariable frequency domain controllers for such tests using a laboratory-scale test rig. This paper continues that work comparing the design and implementation of both sequential loop closure and multivariable characteristic locus schemes for an industrial scale test rig. The performance achieved with the multivariable controller is shown to be far superior to that obtained with the sequential loop closure scheme.