Active Fault-Tolerant Control for Electro-Hydraulic Systems With an Independent Metering Valve Against Valve Faults

Aiming at the tough requirements for safety and maintainability in mobile hydraulic systems, in this article, an active fault-tolerant control (FTC) system is proposed against the valve faults of an independent metering valve. Not only moderate faults of activated valves, but also significant faults and unactivated valve faults are considered. Without additional hardware redundancy, analytical redundancy is derived by the coordinate control of other fault-free valves. Accordingly, an FTC system in parallel with a normal controller is designed based on the pressure feedback. It consists of a set of reconfigurable controllers and a decision mechanism. The control signals, control loops, and operating modes can all be precisely reconfigured to adaptively match unmodeled fault dynamics. A bumpless transfer controller based on a latent tracking loop is designed to smooth the switching between the normal controller and FTC. Consequently, random valve faults can be tolerated with minor degradations in motion tracking and energy-saving performance. The feasibility of the FTC system is evaluated by a 2-ton excavator.