Development of a hydraulic propulsion system controlled by proportional pressure valves for the 4500m work-class ROV

Hydraulic propulsion system is widely used in remotely operated underwater vehicles (ROVs) especially work-class ROVs due to its high power density and strong work capability. In most hydraulic ROVs, the propellers are controlled by servo flow rate control valves or variable displacement motors. In this paper, a novel hydraulic propulsion system controlled by proportional pressure valves with rotational speed feedback is proposed, including new-material thrusters and adaptive electronic control units (ECUs) which can work properly in the high-pressure oil. The proportional pressure control system has a much lower cost and a higher efficiency compared with servo valve control systems. And its response is still quick enough to control the underwater vehicles´ attitude compared with variable displacement control system. Moreover, it can reduce the influence on the vehicle dynamics caused by the dead-zone and hysteresis of the proportional valves due to the rotational speed feedback. This paper describes both the design and technical integration of the deep water proportional-pressure-controlled hydraulic propulsion system, including hydraulic and electronic elements. Additionally, the simulation and in-water tests of several key elements such as the thrusters and hydraulic pump are presented. Both the simulation and experiments results show that the closed-loop propulsion system has a fast response with high precision.