Hydraulic actuator leakage quantification scheme using extended Kalman filter and sequential test method

This study is a further research based on previous published papers focusing on hydraulic leakage fault detection and isolation. The authors have verified the effectiveness of a FDI scheme based on extended Kalman filter (EKF) for the change of supply pressure (An and Sepehri, 2003). A completed FDI scheme (An and Sepehri, 2005) was also proposed by the authors focusing on various actuator leakages. However, the quantification of the leakages was not elaborated. In this paper, the quantification of leakage faults in a hydraulically powered actuation system is presented. A quantification scheme based on sequential analysis (SA) is proposed and is shown to be effective to estimate the seriousness of the leakage. A bank of hypothesis tests that based on Wald's method (Wald, 1947) is composed to report the average value of the residual error. The relation between the residual error and the corresponding leakage is determined and, based on this information, an assessment of the leakage damage can be achieved