The Study Of Self-turning PID Algorithm Using In Electro-hydraulic Proportional Flow Valve Controller

The technology of hydraulic has advantages of high precision, smooth transmission, strong ability to load and be convenient to achieve step less speed adjustment and complex movements, so it has been used widely in modern industrial control and engineering machinery. The digital controllers are much more flexible and convenient in the controlling system than the analog ones, it is one of the development trend in the future.The thesis has made standard input and output interface that based on actual demand, and we have also completed the design of hardware system and algorithm software system. In the thesis, we study the characteristics of the proportion flow valve and stress analysis of the slide during different positions. The hard system contains power amplifier, data acquisition circuit and sensor regulate circuit etc. which sets the ARM7as the controlling center. The software system contains different tasks that be coordinated by the μC/OSⅡ, the system can produce64tasks at most at one time.The most difficult job during the designing of digital electrohydraulic proportional controller is the design of algorithms, the fundamental purpose of the closed-loop control algorithm is to improve control precision. Because of the interference of friction and fluid power, the system has many nonlinear links, so it is also important to improve the compensation for nonlinear links. We have the special experimental platform to test our controller:step response, steady-state error and shock signal.We make the algorithm of PID be used in the digital controller and we proved by the experiment that the algorithm can suit the system, but it is difficult to make the parameters to be the best ones because of the complex influences which contain different powers. The system will produce huge overshoot during the step response. So we designed the self-turning PID algorithm by the method of relay feedback, using this method we got the parameters of proportion, integral and differential. It is proved that the parameters from this method would improve the performance of the digital electrohydraulic proportional controller markedly.