Fault-tolerant sliding mode control for uncertain active suspension systems against simultaneous actuator and sensor faults via a novel sliding mode observer

In this paper, the problem of fault estimation and fault-tolerant control for half-car active suspension system with simultaneous varying sprung and unsprung mass, actuator fault, and sensor fault is investigated. First, Takagi-Sugeno fuzzy approach is used to describe the uncertain half-car active suspension system with simultaneous actuator fault and sensor fault. Then, a novel augmented descriptor sliding mode observer is designed to estimate the state of system, actuator fault, and sensor fault with good precision. Based on the state and fault estimation, a fault-tolerant sliding mode control scheme is designed to stabilize the resulting fault half-car active suspension system. By utilizing Lyapunov stability theory, the existence condition for the proposed sliding mode observer and fault-tolerant sliding mode controller is provided in terms of linear matrix inequalities (LMIs). In addition, it is shown that the reachability of the developed sliding surface can be ensured under the design control law. Finally, simulation results for uncertain half-car active suspension systems are presented to demonstrate the effectiveness of the proposed design techniques.