Fuzzy fault tree theory-based fault search strategy research for FAST hydraulic actuators

As the active mechanism of the main reflector system for a Five Hundred Meter Aperture Spherical Radio Telescope (FAST), the reliable operation of 2225 hydraulic actuators is the basis of normal observation for the telescope. The purpose of this research is to find the right fault search strategy for these hydraulic actuators. According to the characteristics of hydraulic systems, this study proposes a fault search strategy analysis method based on fuzzy fault tree theory. Considering the maintenance factors of hydraulic actuators, such as the searching cost, the failure probability and the degree of influence, the optimal search strategy model for fault diagnosing of hydraulic actuators is established. The multi objective optimization decision theory and sequential decision theory are also applied in this model. Finally, the fault search order for FAST hydraulic actuators is calculated. The top three fault search components are motor, controller and hydraulic control check valve. The calculated results are in agreement with the reliability test results and Failure Mode Effects and Criticality Analysis (FMECA) of hydraulic actuators. This study has guiding significance for the maintenance of the hydraulic actuators for FAST.