Fault detection in electro-hydraulic servo-positioning systems using sequential test of Wald

Presents a scheme for fault detection in hydraulic servo positioning systems using analytical redundancy. A fault is understood as a malfunction in the dynamic system that leads to an unacceptable anomaly in the overall system's performance. The approach taken is to first construct a nonlinear observer. The actuator's linear velocity is taken as input to the observer. The cumulative sum of the residuals, taken from the difference between the actual and the observed velocities, is then used in a sequential test of Wald to determine the occurrence of a fault. Experiments are conducted for faults due to incorrect supply pressures as well as sensor faults. Results show the efficacy and the promise of the proposed scheme.