According to the closed hydraulic system features dual variable speed, finishing variable pump, the use of variable speed motor expect calculate variable displacement pump and motor displacement; the use of variable structure variable motor speed control algorithm, and the algorithm of Lyapunov stability proof. The simulation shows that the variable displacement pump, based on this control strategy can effectively improve the response speed of the system, reducing the overshoot, and the algorithm is robust in the hydraulic system, as long as the motor (or other prime mover) rotation, the pump will be out of oil, maintenance variable displacement pump and the load does not move, they do not need pressure oil pump oil out of nowhere to go, repair variable displacement pump, only returned to the tank through the relief valve, the heat is very large, persistent high pressure and damage pumps and hydraulic valve. In this case must be no pressure of hydraulic oil released back into the tank, this action is called (oil pump) unloading. Maintenance variable pumps | hydraulic factory direct hit grain (certified) | Variable pump from Jinan Jing Chong Hydraulic Machinery Limited. Jinan Jing Chong Hydraulic Machinery Co., Ltd. (www.jnjcyy.com) (www.jnjcyy.com) Shandong Jinan, mining machinery leaders, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, the maximum meet customer needs. In the crystal creating hydraulic leadership with the staff warmly welcome all inquiries negotiations to create the crystal creating hydraulic better future.