| Traditional electro-hydraulic servo system has been employed in many fields, such as aviation, spaceflight, national defence and other civil industries, because of its high power, fast response, and high precision. However, it has great energy loss during work and is very sensitive to oil contaminated and temperature change. At the same time, it needs high manufacture precision and is hard to look up the causes when it fails to work. The last, it is expensive and needs high cost of repair and maintenance. All of these shortages restrict the application of traditional hydraulic servo system.With the development of AC servo technology, valveless electro-hydraulic servo system, also called direct drive volume control system, comes into being. It's a new kind of electro-hydraulic servo system with the advantage of flexible control, high power, high efficiency, energy-saving, small volume, and high reliability performance. So it is regarding as one important developmental trend of electro-hydraulic servo system.Based on the correlative literature and reference materials at home and abroad, this paper summarizes the development of research progress of valveless electro-hydraulic servo system. The mathematical models of pump control asymmetry cylinder and force control of valveless electro-hydraulic system are established. Stable error of system is discussed in detail. With the aid of Matlab simulation, the dynamic characteristics of the model are analyzed.Aiming at the characteristics of valveless electro-hydraulic servo system, the controller based on structure invariance principle and optimal quadratic controller are applied. The two control strategies are introduced in the paper. In virtue of Matlab simulation of step and sine signal response, some conclusions are obtained. They show that the controllers used in system are effective. Experiment validates the theoretical study. Then some beneficial conclusions are obtained. |
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