ℒ1 adaptive output feedback controller for a class of nonlinear systems

This paper presents an extension of the L₁ adaptive output feedback controller to a class of nonlinear systems where nonlinearities satisfy a semiglobal Lipschitz condition. The control algorithm consists of an output predictor which is designed to predict the system´s output with arbitrary accuracy, and a control law which is used to control the predictor output instead of the actual system´s output. It is shown that the adaptive output feedback controller ensures uniformly bounded output tracking for the system. The performance bound can be systematically improved by reducing the step size of integration. Numerical simulation results are provided to illustrate the algorithm´s performance.