ROBUST ADAPTIVE OUTPUT-FEEDBACK CONTROL OF A CLASS OF UNCERTAIN NONLINEAR SYSTEMS

摘要

With an attempt to simplify the controller design and to reduce the control effort, a new robust output-feedback controller is designed to solve the tracking problem of a class of nonlinear uncertain systems by using observer plus backstepping. In the controller design, a simple observer is constructed, by which only a coarse estimate of the unknown states is provided, and a positive function used to generate a new normalization signal and the positive nonlinear functions used in nonlinear Ramping terms are all left to be chosen freely. Thanks to these techniques, the new controller can be designed with a simpler structure and reduced control effort under weaker assumptions on both the uncertainties and the reference signal. The global boundness of all closed-loop signals can be guaranteed, and the output tracking error can be made as small as possible.