Research On Bi-directional Pump Flow Field And Low Speed Characteristics Of DDVC System

The Direct Drive Volume Control (DDVC) Electro-hydraulic Servo System is a new electro-hydraulic servo system that uses AC servo motor and bi-directional pump to replace the combination of servo valve and variable displacement pump. This system adjusts the AC servo motor speed and steering to control the output of the pump, and then the motion of the actuator can be changed. With high efficiency and energy saving, small integrated, simple manipulation and control. DDVC Electro-hydraulic Servo System is widely used in the national production and military fields.For the precise control of occasions, low speed output performance of the system is particularly important to avoid jitter and instability. Bi-directional pump is an important hydraulic component of DDVC system, its inner leakage, pressure pulsation and flow pulsation phenomena affect the stability and accuracy of the system output, especially at low speed. Therefore, it is necessary to research the bi-directional pump flow field and the low speed characteristics of DDVC system.In this paper, the DDVC system motor model, the hydraulic model, the bi-directional pump leak model, and the flow pulsation model were established. And the bi-directional pump 2D simulation model was established to analyze the pressure field, velocity field and the output flow in Fluent simulation software. The phenomena of pump leakage, vortex,pressure pulsation and flow pulsation were analyzed by these physical quantities. Then the influence of the gear parameters on the pulsation phenomenon is analyzed by the flow pulsation model, and the parameters of the gear pump are optimized according to the results of the analysis.In this paper, the hydraulic model was established in AMESim, and the servo motor control model, the leak model and flow pulsation model were established in Matlab/Simulink to analysis the impact of the system output. Finally, based on PID control method, the pressure close-loop control at pump outlet was set to reduce the pump output flow pulsation,and the position close-loop control was set in DDVC system to reduce the pump flow pulsation and leakage effects on output. The system output jitter, "spire" and dead zone has been obviously improved by simulation analysis.