RESEARCH ON THE STATIC PERFORMANCE OF ELECTRO-HYDRAULIC SERVO SYSTEM WITH SPEED VARIABLE PUMPS

：A new energy saving concept to control the position of a differential cylinder with speed variable pump is put forward. Through the research of control principle，a double speed variable pumps circuit concept and sum pressure controlling principle is established. With these two new methods the unsymmetrical flow of differential cylinder can be balanced automatically and the cavitation and lose of control avoided. The flow-pressure function and pressure gain function is derived. The research has further proved that the new electro-hydraulic servo control principle can eliminate all the throttle losing and has the same technical features as the valve controlled servo system.