Analytical redundancy approach for fault detection in electro-hydraulic servo-positioning systems using a nonlinear observer and sequential test of Wald

This thesis presents a scheme for condition monitoring and fault detection in hydraulic servo positioning systems using analytical redundancy. The work contributes to fault detection and isolation (FDI) of nonlinear systems. In this context, a fault is defined as any kind of malfunction in the dynamic system that leads to an unacceptable anomaly in overall system performance.; The approach taken in this thesis is to reconstruct the output of a system by an observer. The comparison between the estimated and the measured values of the output is permitted by using an average sequential test of Wald to detect the failure.; Velocity output from the system is taken as input to the observer. Residuals are taken from the difference of the actual and the estimated velocities. The cumulative sum of the residuals is then used in a sequential test of Wald to determine the occurrence of fault. Simulation studies are conducted for cross-port leakage in the actuator, external leakage from the actuator, faults due to compliance variation, faults due to incorrect supply pressure, and sensor faults. Experiments are conducted for faults due to incorrect supply pressures and sensor faults. (Abstract shortened by UMI.)...