Sensor fault accommodation: a model-free framework

A novel model-free sensor fault accommodation approach is proposed in this paper. One of the main problems associated with sensor faults in closed-loop systems is that it is the measurement that follows the desired operating point, but not the output to be controlled. The proposed approach is not model-based and works when the closed loop is in steady-state behaviour. First, the sensor fault is estimated using only the closed-loop static characteristic. Second, this estimation allows to accommodate the control law so that the operating point of the regulated output follows the desired setpoint. The sensor fault accommodation procedure is developed for both linear and nonlinear systems. Unlike in the linear case, the accommodation procedure is iterative in the nonlinear one, and a sufficient convergence condition is given in the latter case. The validation of the sensor fault accommodation strategy is carried out for both linear and nonlinear systems by embedding it in a whole fault detection, identification and accommodation (FDIA) procedure, where the choices of the control law design and of the sensor fault detection are model-free approaches given in the literature.