Research And Design Of Electro-hydraulic Proportional Control System Based On High Frequency PWM

Electro-hydraulic proportional control technology is critic to construction mechanism including auto crane. With rapid development of Chinese fundamental constructions, more and more auto cranes are needed. It provides a good opportunity of expanding this market and making fortune for both abroad and civil auto crane manufacturer. But there are some difficulties to compete with overseas counterparts for civil manufacturer. One reason is that poor of technical level, most civil manufacturers'products are based on the imported electro-hydraulic proportional controller which is act as the core, as a result, the cost become higher and lost the advantage of lower cost. The other lies in the imported electro-hydraulic controller itself. Being a general product, the imported control doesn't work well in particular working conditions in China. Based on above two points, developing electro-hydraulic proportional controller of having independent intellectual property is now urgent to civil auto crane manufacturer.Combined with a significant project of Hunan province, the application and research of electro-hydraulic proportional control system base on engineering machinery has been put forward. Firstly the development history and trend of electro-hydraulic control systems are introduced. Based on the modeling of auto crane hydraulic system, to solve the non-linearity, hysteresis and time-variation of the system, a novel control algorithm-fuzzy neural network PID is put forward and the closed-loop control of hydraulic motor is implemented, the PID control parameters are adjusted by the fuzzy neural network. Secondly, kinds of field buses applied to industrial control network are studied, can bus is finally selected to guarantee the stable and real-time communication between master and slave nodes, furthermore, based on the ARM hardware platform andμC/OS-Ⅱmicro kernel platform, the CANopen protocol implemented. Lastly, the paper design a high frequency PWM driver for electro-hydraulic solenoid to implement the closed-loop control of coil current, the current of coil and the frequency of dither signal can be tuned separately, even more important, magnetic hysteresis problem is solved.The experiment of central controller states that embedded electro-hydraulic proportional control system described in the paper has reached the design demand with the advantage of stability, security and easy to handle. It also states the the research is of validity and practicability.