Combining switching, over-saturation and scaling to optimise control performance in the presence of model uncertainty and input saturation

Saturating actuators are present in all real control systems. Their effect on system performance clearly depends on the range of control action required relative to the saturation bounds. Much of the prior work on this topic has centred on how to switch linear controllers so as to avoid saturation occurring. This, however, has meant that the full input authority has not been exploited in the control law. Recently, two alternative methods have been proposed for switching linear controllers so as to force the input into saturation. They achieve this goal by scaling the controls or by allowing over-saturation in the switching scheme. In this paper the two methods are combined into a more general scheme. It is also shown that the combined scheme is capable of achieving superior performance. A robust version of the algorithm is also described which is applicable to a class of uncertain systems.