Design of robust controllers with time domain specifications Projeto de controladores robustos com especificações temporais

Abstract

The robust design of compensators with time domain specifications aiming setpoint tracking and disturbance rejection is discussed in this paper from a perspective of loop shaping. The constraints to provide robust disturbance rejection are derived as functions of reference models, which contain the associated time domain specifications. It is shown that the larger is the distance between the nominal plant model and the reference models to be followed the more restrictive the design constraints will be. The problems can be posed as model matching compensators and the proposed procedure may reduce the conservativeness normally associated with their design. The plant model is assumed subject to unstructured uncertainties and the design specifications are written in the usual form of loop shape constraints. Hence techniques like H∞ and LQG/LTR can be applied as design tools. In order to illustrate the use of the proposed methodology we consider a multivariable mixture tank as an example.