Fault tolerant control of electrohydraulic servo positioning systems

This paper describes the design and experimental implementation of a fault tolerant controller for an electrohydraulic servo positioning system. The controller is expected to retain the hydraulic system at least stable in operations under sensor failure or presence of faults in the servovalve as well as the supply pump. A mathematical model describing a hydraulic actuator is derived, by which the sensor failures or the component faults are captured as uncertainties in the model. Based on the quantitative feedback theory, a robust controller is designed to maintain key properties of the closed-loop system, such as stability and disturbance rejection. The controller designed is easy to implement and no online tuning or adaptation is necessary. The feasibility of the controller was evaluated by implementing it on an experimental test rig. Experimental results demonstrate the effectiveness of the designed controller under abrupt sensor failures and incorrect supply pump pressures.