Abstract: The electro-hydraulic servo system directly controlled with speed variable pumps is a competitive and environmental beneficial driving principle. In this system the all throttle losing existed in principle can be eliminated and hardly consume any energy in the pause period so the system has good efficiency and low noise. The dynamic performance is investigated with theoretical simulation and experimental methods. The results show that the dynamic and static performance can be compared with the systems controlled by a servo valve.

Key words: Differential cylinder circuit, Electro-hydraulic servo control, Speed variable pump