Cascade control for a class of uncertain nonlinear systems: a backsteppingapproach

A design procedure for adaptive cascade control of a class of uncertain sin gle-input nonlinear systems in strict feedback form is proposed. The contro l scheme is based on a backstepping design endowed with a modeling error es timator. In the one-dimensional case, the resulting controller is equivalen t to a PI control law. Constructed as an extension of the one-dimensional c ase, the high-dimensional case can be interpreted as a cascade PI controlle rs. Stability of the underlying closed-loop system is established from resu lts of singularly perturbed nonlinear systems. Our results are illustrated via numerical simulations. (C) 2000 Elsevier Science Ltd. All rights reserv ed.