Model-Based Real-Time Fault Monitoring Strategy for Hydraulic Servo Actuators

Hydraulic servo actuator is still widely used in flight control system. To enhance its reliability, redundancy technology is applied to improve its fault-tolerant ability by isolating defective channels. To supply the decision bases for this isolation, the working status of all channels of the system must be monitored. In this paper, a model-based monitoring scheme is presented and simulated according to this principle. The mathematical model is established by analyzing the principle of components such as the linear force motor, the servo valve and the cylinder. According to the variable monitored, the reduced-order reference model in the monitor can be determined based on the link contained through appropriate reduction. Then, a redundant model is developed in AMESim to simulate the actual actuator. This approach offers the benefit of facilitating the implementation of fault injection. The mathematical model is then used to monitor the actuator under normal and faulty conditions. It is expected that the monitoring results are consistent with the actual state of the actuator. As a result, when serious faults occur in the system, the model monitoring scheme can accurately decide and give corresponding redundancy switching instructions. But it is not sensitive to the degradation of system performance. The effect of the technique depends on an accurate system model, and a reasonable threshold.