Robust Adaptive Fault-Tolerant Control of Nonlinear Systems With Assignable Tracking Performance Under Time-Varying Control Coefficients

Abstract

This paper presents a robust adaptive fault-tolerant control method for a class of strict-feedback nonlinear systems with nonparametric uncertainties and unknown time-varying control coefficients as well as actuation faults. By employing a time-varying scaling function and an integrable function into control design, an adaptive Nussbaum gain-based fault-tolerant control approach is established, which displays the following salient features compared with the existing results: 1) the incorporation of time-varying scaling function renders that the tracking error converges to an adjustable compact set within an arbitrarily prescribed time at a decay rate no less than a pre-specified value, and 2) the utilization of the integrable function can handle the nonparametric uncertainties and actuation faults, which ensures that the nonlinear system is stable over $[0,\infty$ ) and the tracking error converges to zero as $t\to \infty $ . Furthermore, it is proved that the developed control law can guarantee that all signals of the closed-loop systems are globally uniformly ultimately bounded. Simulation results validate the benefits and effectiveness of the proposed scheme.