A simulation method for an underwater electro-hydraulic actuator with the leakage fault

The underwater electro-hydraulic actuator (EHA) system is a critical technology for deep-sea exploration and development, which is particularly suitable for high-performance and high-reliability requirements under high-pressure and complex environmental conditions. However, the underwater EHA system always produces some failures, such as the hydraulic cylinder leakage, piston pump leakage, and valve leakage et al., in the extreme working environments. Those failures not only degrade system performance but can also lead to catastrophic system failures. This paper proposes a simulation method to investigate the typical faults in an underwater EHA system. A pressure compensator is added when establishing the simulation model to ensure the normal operation of the EHA system under the water, and to simulate the high-pressure environment of the underwater operation by changing the load value of the load end. In this paper, we study the changes of rod displacement, pressure, shaft torque, and fluid velocity caused by different faults under high-pressure conditions. An experiment is also conducted to validate the simulation model and the results. The research shows that the effective stroke of the hydraulic cylinder, the outlet pressure of the piston pump, and the shaft torque all significantly decrease with the increasing of leakage, which can reduce the system efficiency. This research can provide some guidance for the fault analysis and diagnosis in underwater EHA systems.