Variable structure conventional controllers

Most process controllers are frequently of PID type. Many variations of the basic structure have been developed; one of the most significant is the introduction of self-tuning features. Advanced model based controllers have also been implemented by using microprocessors. The controllers to be used in automated processes must be simple, reliable and low cost; the introduction of microprocessor technology complies with these requirements and allows to consider also non linear features in a straightforward manner. In this paper a Variable Structure Controller approach is used to design a complex controller capable of retaining both the main advantages of switching systems (with high insensitivity to external and parametric disturbances) and a satisfactory transient response along with a very simple non linear structure directly implementable by microprocessors. A complete set of simulation results is reported.