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.