A Closed Loop Speed Control System for Hydraulic Pump-Motor

Mathematical models of hydraulic pump-motor and displacement servo system were built up.Characteristics were analyzed according to bode diagram and step-input response.Results of analysis showed that the band width of displacement servo system is small because of low flow gain of servo-valve,whereas the band width of hydraulic pump-motor compared to be wider,and it responds quickly with overshooting.A motor speed closed loop control digital PID controller is given.The PID control parameters as achieved by simulation was used in the velocity control system of pump-motor operating on test-bed and gained excellent dynamic and stable characteristics.