Active Fault-Tolerant Control for Nonlinear Systems With Nonlogarithmic Sensor Resolution

Sensor resolution is an essential characteristic of almost all sensors, yet it has been overlooked in most studies on fault-tolerant control. This article considers active fault-tolerant control (AFTC) for a class of nonlinear systems in the presence of nonlogarithmic sensor resolution (NLSR) and mismatched disturbances. To achieve fault detection and ensure bounded estimation errors of the faults and states, the article designs a decoupling design approach between the estimator and the controller, utilizing the measured output. This approach relaxes the assumption of accurate fault estimation in existing AFTC approaches. Furthermore, the fault-tolerant controller design in this article utilizes a command filter technique to overcome the challenges posed by the nondifferentiable output resulting from the sensor resolution issue. The proposed control design considers error terms caused by disturbances and limited resolution as new disturbance terms for adaptive compensation. With the regulation of the fault compensation term, all signals in the closed-loop system are bounded, and the tracking errors are adjustable by choosing the appropriate parameters. A simulation example is performed to illustrate the performance of the proposed AFTC method.