Research on pressure compensation for underwater hydraulic systems with underwater ambient pressure-compensated valve

Based on the influence of underwater ambient pressure (UAP) on underwater hydraulic actuators, and the state-of-the-art of pressure compensation of underwater hydraulic systems (UHSs), this paper proposes a pressure compensation method, which is used in a UHS whose hydraulic power unit is installed inside a deep diving submersible or a submersible drilling platform in which the pressure is an atmospheric pressure, and some actuators of which are directly surrounded by seawater, and others are installed inside it. A 3 port pressure reducing valve with underwater ambient pressure compensation is developed. The pressure compensation accuracy is guaranteed by a direct detection. Its dynamic performance and stability are improved by a dynamic feedback. The pressure in the return line of underwater sub-circuits of the UHS is compensated by this pressure-compensated valve. But other sub-circuits in the atmospheric pressure needn´t be compensated. The simulation and experimental results show that the performance of the reliable pressure compensation can be ensured