| Recent years, with the development of science and technology, the concept of digital hydraulic has been proporsed. Thereafter because of the advantages of its strong robust, simple structure, high reliability the digital hydraulic has been received widely attention from the academic. The digital pump, digital valve, digital motor mushroomed catches people’s eyes. Digital hydraulic technology could be divided into two types of high speed switching and parallel connection. But the parallel connection technology was expensive and the size was large, and the high speed switching technology can only control the single direction and the control precision was bad. The static and dynamic characteristics of the high speed switching type digital valve was simulated and tested, and useing the valve components digital valve controlled cylinder position servo system. The control performance was studies. And the compound control of feedforward and feedback by neural network and PID was proporsed to improve the control precision of the digital valve controlled cylinder position servo system. Therefore, the research work as following:(1) The digital valve model was established and characteristic was analyzed. The mathematical model including electric force, magnetic force, hydrodynamic force and block force was established. The simulation model using Matlab / Simulink was builded, the digital valve performance test rig was designed and set up, and the dynamic and static characteristics of the digital valve was simulated and tested. The results showed that the digital valve electric response time decreases with the decreasing of the pressure of oil, and power loss of response time increases with the decreasing of the oil pressure; the digital valve linear flow characteristics was good, the dead zone increased with the decreasing of oil pressure decreases, and the saturation region increased with decreasing the pressure of oil; the digital valve mathematical model is correct through the comparison of simulation and experiment, and provide the basis work for the further research.(2)The model of the position servo system of digital valve control cylinder was established and analyzed. The digital valve controlled cylinder position servo system was composition of a single digital valve and directional valve. Its mathematic model was established, and its simulation model was constructed in Matlab / Simulink. And the related experimental research was done. The simulation and experimental results show that digital valve controlled cylinder position servo system control precision was rated with the working frequency of the digital valve, and with the increasing of working frequency the position control accuracy and transient response characteristics were improved.(3)The high precision control method of digital valve control cylinder position servo system with was studied. The CMAC-PID compound control combined the CMAC control algorithm, implementation of feedforward control, and PID control, achieving feedback control, and it was applicated to the digital valve control cylinder position servo system. The simulation and experimental results showed that the system transient response characteristics has been significantly improved. The steady state accuracy of the system has also been significantly improved, and the steady-state error was controlled in less than 0.1mm. Besides, the effect of working frequency on the steady state accuracy of the system was very small. |
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