Approximation-Free Prescribed Performance Control

A universal controller is designed for strict feedback systems with unknown nonlinearities, capable of guaranteeing, for any a priori known initial state condition, bounded signals in the closed loop, as well as prescribed performance for the output tracking error. By prescribed performance we mean that the output tracking error converges to a predefined arbitrarily small residual set, with convergence rate no less than a certain prespecified value, exhibiting maximum overshoot less than some sufficiently small preassigned constant. The proposed control scheme is of low complexity and requires reduced levels of a priori system knowledge. A comparative simulation study verifies the superiority of the proposed control scheme against the well known backstepping technique, which has been the main tool for designing controllers for the class of systems considered.