Leakage fault identification in a hydraulic positioning system using extended Kalman filter

This paper presents the application of extended Kalman filter (EKF) towards leakage fault identification in a servo-hydraulic actuation system. The EKF rebuilds information about the system´s states based on the input signal and measurements of the actuator displacement and cylinder chamber pressures. By comparing the estimated states with the measured ones, residual signals are generated. When faults happen, the levels of certain residual errors change. It is shown that different leakage types could cause changes in different residual errors; thus, the EKF-based method has the potential to identify fault types. Experiments show that EKF estimator promptly and reliably responds to faults caused by different actuator leakages. With the mapping of residual error changes, the EKF successfully identifies cross-port (internal) leakage, as well as cylinder chamber (external) leakage at either side of the actuator.