Semiglobal Robust Backstepping Output Tracking for Strict-feedback Form Systems with Nonlinear Uncertainty

Output tracking controller design problem is dealt with for a class of nonlinear systems in strict-feedback form in the presence of time-varying nonlinear uncertainties and unmodeled dynamics with multi-operation points. A new method based on signal compensation is proposed to design a robust controller, which consists of a nominal controller and a robust compensator. It is shown that semiglobal robust tracking property can be achieved. A new feature of our results is that the controller is a linear and time-invariant one and explosion of complexity problem is avoided.