According to the problem of slow response and severe time_variable of unsymmetrical cylinder position system controlled by a proportional valve, the policy of fuzzy_PID self_adaption control was suggested.

?A system to control unsymmetrical cylinder position by a proportional valve was studied.

The unsymmetrical cylinder controlled by unsymmetrical valve is often used in hydraulic servo system.

This paper presents a new concept of asymmetrical valve controlled asymmetrical cylinder,makes new definition of load flow and load pressure,thus illustrated static and dynamic properties of asymmetrical cylinders,derives its transfer function and block diagram,which can be universally applied to all kinds valve controlled cylinder and may be a meaningful guide to the design of such servo systems.

In this paper,the domination principle of the hydraulic position closed-loop system consisted of the position sensor and symmetrical hydraulic cylinder controlled by the servo valve is introduce.

According to the asymmetry and nonlinearity of the symmetrical valve controlled asymmetrical piston system, in order to improve control precision of the system, the work characteristic of the system is analyzed, then a new control method based on the cerebellar model articulation controller(CMAC) is advanced, and the CMAC compound controller is designed.