ROBUST INPUT-OUTPUT FEEDBACK LINEARIZATION

To make input-output feedback linearization a practical and systematic design methodology for single-input nonlinear systems, two problems need to be addressed. One is to handle systematically the difficulties associated with the internal dynamics or zero-dynamics when the relative degree is less than the system order. The other is to account for the effect of model uncertainties in the successive differentiations of the output of interest. While the first problem has recently received considerable attention, the second has been largely unexplored. This paper represents a preliminary study of a systematic methodology to account robustly for parametric uncertainties in the original system model. The approach is based on combining sliding control ideas with the recursive construction of a closed-loop Lyapunov function, and is illustrated with a simple example.