Unstructured uncertainty and graphic robust control system design

Preliminary results regarding robust control design in the presence of unstructured uncertainty are presented. The basic aim is to develop graphic tools to carry out computer aided design for this type of uncertain system. The core of the tool is a modified Nichols chart, where the magnitudes of both sensitivity and complementary sensitivity are depicted. It is shown that unstructured plant uncertainty can be very easily represented and manipulated on this diagram. It is also shown that Horowitz´s design philosophy can be easily implemented using simple templates extracted from the chart itself