| The main objective of this paper is to develop a valve-controlled cylinder electro-hydraulic positioning system with a longer hydraulic transmission line through theoretical study, simulation and engineering practice. The valve-controlled cylinder electro-hydraulic positioning system will be used to a underwater parallel manipulator with redundant actuation; the underwater parallel manipulator has features a redundant hydraulic actuation and longer hydraulic transmission line.Firstly, based on the actual needs of the parallel manipulator, an electro hydraulic servo system has design; the key element selection finished; a typical model of the electro-hydraulic positioning system to be establishes.Secondly, Pipeline dynamics theory and working principle of the valve-controlled cylinder electro-hydraulic positioning system is expounded base on hydro-dynamics equation/ conservation of energy/hydro-status equation.The effect of longer pipeline model has been considered based on the frequency-dependent model. On the basis of the mathematical description of the system, the computer simulation on the system is implemented and the important parameters of the system are analyzed.Analysis of the response characteristics of the hydraulic pipeline, discussed the characteristics of the electro-hydraulic positioning system of hydraulic pipe. Simulation results show that the channel length, flexible tube wall thickness and diameter of the system have proved a great impact. The computer simulation laid a foundation for the optimization of the pipeline. In considering the effects of electro-hydraulic positioning system based on the model of pipeline, AMEsim/Simulink joint use of simulation technology, classic PID control strategies were used to the system control simulation. Optimize the pipeline Based on the results of simulation studies.Finally, design and build a valve-controlled cylinder electro-hydraulic positioning system performance test platform. Valve-controlled cylinder electro-hydraulic servo system is test and pilot studies. Test results show that the PID control strategy is feasible and reasonable advantages. Steady control with high precision, over-regulation of smaller, steady-state error of less than 0.1mm. Do 0.5Hz sinusoid campaigns, the amplitude ratio of 1.005, 4.8°phase lag. Control with fast response and strong robustness.The results show that the existing valve-controlled cylinder electro-hydraulic positioning system and control strategies completely applicable to the underwater parallel manipulator.
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