Simulation research on the variable displacement hydraulic motor with variable effective piston stroke for hydraulic propulsion system

Variable displacement speed regulation is a good method for hydraulic propulsion system compared with throttle speed regulation and high speed on/off valve speed regulation, however the minimum variable displacement motor we can get is about 28cc/r, which is too large for a light or medium weight ROV. The variable effective piston stroke (VEPS) motor is a kind of virtual variable displacement (WD) motor which is suitable for hydraulic propulsion system. The VEPS motor have hydro-mechanically controlled poppet control valves on every cylinder of the piston motor, and have a completely symmetrical port plate instead of a kidney plate as in a conventional motor, creating a hydraulic motor capable of producing variable power. It is based on the conventional axial piston motor but with hydraulic operated poppet valves as distributor for each cylinder. All the poppet control valves are set to execute at the same setpoint(an angle position on the portplate), each cylinder works as a independent WD motor and drives the shaft with the other cylinder. The VEPS motor adjust its displacement by changing the duty ratio of the effective piston stroke. The VEPS motor can change its rotate direction, adjust its displacement just by changing the setpoint of the poppet control valves. A computer model of the VEPS motor based on AMEsim is built to check the novel variable piston motor, and the simulation results show that VEPS motor can achieve the functions mentioned above with proper parameters. The functional test of the prototype also shows that the VEPS pump-motor is feasible.