Fault tolerant control of nonlinear hydraulic systems with prescribed performance constraint.

Aiming at the low tracking accuracy and poor fault tolerance of displacement-controlled systems, this paper puts forward a fault tolerant robust controller. The influence of many uncertain factors on trajectory tracking performance have been considered, such as external disturbances, high nonlinearity, system faults, and complex modeling uncertainty of the system. First, a new finite-time observer is proposed to estimate the system states, disturbances, and system faults simultaneously. Then, an improved fast super twisting algorithm is designed to guarantee the reachability of the sliding surface in finite time. Furthermore, the prescribed performance constrained control technique is combined to ensure that the tracking error remains within the prescribed bounded range even though faults occur. Finally, the effectiveness of the proposed control method is validated by simulation results.