Non linear standard regulators

The problem of designing Non Linear Standard Regulators (NLSR) is faced for uncertain systems with time delay. Some recent rules for robust tuning of conventional controllers are recalled. The favourable characteristics of the Variable Structure Control (VSC) approach to the design of NLSR for system without delay are shown by a comparison of performance with Standard Regulators in the presence of large parameter variations. The VSC approach is then extended, by means of a suitable modification of the Smith predictor control structure, to systems with time delay. A control law, able to give acceptable performance for different process parameters, is then proposed and simulation results are discussed.