Robust Control Systems Design Using Matlab

In general, robustness does not “come for free” from a controller designed via optima control and estimation theory (observer design): a controller designed for a nominal process model generally works fine for the nominal plant model, but may fail for even a “nearby” plant model. An important point of all feedback control synthesis methods is the control engineer’s awareness of inherent trade–offs : increasing the robustness will generally make the controller“less aggressive”, and will thereby decrease system performance.Robust control allows to specify more or less directly the plant uncertainty, and allows to predict the possible trade–offs between robustness and closed–loop performance.