Robust performances control design for a high accuracy calibration device

Abstract

This paper presents a case study of robust performances control design. The physical plant under examination consists of a platform for calibration of high accuracy accelerometers, which has to assume the properties of an inertial body, despite the vibrations coming from the surrounding ground. Plant modelling and parameter estimation, control system design and robustness analysis of the designed controllers are described and discussed. Besides a simplified model of the plant, called the nominal model, perturbations are also considered, taking into account parametric and dynamic uncertainties. The procedure followed for estimating model parameters, based on an unknown but bounded approach, is illustrated, and uncertainty intervals of parameter estimates are provided. Bounds of unstructured uncertainty are also derived from results of simulations aiming to evaluate the main effects of the unmodeled dynamics. The design has been carried on through iterative steps of “nominal” design and robustness analysis. The design has been performed through H ∞ synthesis, based on the nominal model and taking into account the main performance specifications required for the present case study, i.e. stability, disturbance attenuation and command power limitation. The robustness analysis has been performed using recent techniques able to deal with frequency domain specifications and with mixed nonlinear parametric and dynamic perturbation, as required in the present case study.