Adaptive Failure Compensation for Uncertain Systems with Unknown Utility Decrement of Actuators

Utility decrement caused by actuator aging and unknown failures of actuators is inevitable in practice. However, there is still no result available to compensate for instantaneous failures of actuators with unknown utility decrement. This paper aims at addressing this problem by considering a class of strict-feedback nonlinear systems. The controller obtained by our proposed control scheme can be divided into two parts. The first one aims to handle the effects of unknown utility decrement, while the second one makes efforts to compensate for the uncertainties caused by unknown failures. Compared with the existing results, the proposed controller is able to compensate not only the uncertainties caused by unknown instantaneous failures but also the time-varying utility decrement effect of actuators. Moreover, it does not require the prior knowledge about the sign of the constant control gain. In addition, the pre-estimation functions of time-varying gain based on the priori knowledge of utility decrements are fully used to improve the performance of the closed-loop systems. It is shown that the proposed controller can guarantee the boundedness of all closed-loop signals.