Position and flow double-close-loop direct-drive volume control electro-hydraulic servo system

The invention relates to a position and flow double-close-loop direct-drive volume control electro-hydraulic servo system, belonging to the electro-hydraulic servo field. The invention solves the defect of low volumetric efficiency at lower speed of the hydraulic pump of the existing direct-drive volume control electro-hydraulic servo system and the system performance problem caused by the delay of the starting time of an oil supplementation mechanism and a hydraulic lock. The controller of the system is provided with four input ends and a control signal output end. The control signal output end of the controller is connected with the control signal input end of a servo driver or a frequency converter. The control end of the servo driver or the frequency converter is connected with the controlled end of a servo motor. The power output shaft of the servo motor is connected with the power input shaft of a bidirectional constant flow pump. Two oil passages between the bidirectional constant flow pump and a hydraulic cylinder form a closed loop through the oil supplementation mechanism, the hydraulic lock, an overflow safety mechanism and flow sensors. The output end of the displacement sensor, the output end of a first flow sensor and the output end of a second flow sensor are connected with the three output ends of the controller. Since the flow sensors are added on the original system, the control structure is changed.