Adaptive fuzzy prescribed-time fault-tolerant tracking control for constrained nonlinear systems with intermittent faults

In this paper, a novel adaptive fuzzy prescribed-time fault-tolerant tracking control strategy is put forward for a class of nonlinear systems with asymmetric full-state constraints and intermittent faults. First, universal barrier functions are structured to guarantee that system states do not violate the asymmetric constraints during operation. Then, unknown nonlinear functions are approximated via fuzzy logic systems. Estimation of intermittent faults by means of projection operator techniques eliminates the problem of increasing estimates with the number of faults. Subsequently, new prescribed-time adjustment functions are devised such that the tracking errors are practically prescribed time-stable. In addition, the command filter technique is introduced into the backstepping framework to avoid the repeated differential operations of the virtual control function in conventional backstepping. Finally, the performance of the presented scheme is demonstrated via two simulation examples, one of which involves the rotary steerable drilling tool system.