Mathematical Model And Control Algorithm Research On The Parallel Pilot Control Electro-hydraulic Servo Valve

Along with the wide range of applications of servo system in major equipments, the fast-response of high flow servo valve have become increasingly demanding. Conventional series-type pilot control servo valves have encountered insurmountable difficulties when in the settlement of "high flow" and "high frequency", and the parallel-type servo control scheme has become an important research direction to solve the problem. Of which, parallel-type servo valves based on pilot-controlled have been confirmed to be the most effective solution. The accurate simulation model was established, based on which the simulation and experimental research about the asymmetric parameters match of the parallel pilot valves and the nonlinear control program of the main stage position closed-loop was carried out. Studies have shown that the scheme proposed can achieve the optimization of the performance indicators (the step response of the servo valve when transitions between two operating points in the large-scale and the high-frequency response when adjusts near a specific working point included) simultaneously, which has not only laid an important theoretical basis for the new development of our electro-hydraulic servo valve technology in high-flow and high-frequency response, but also further broaden the application field of electro-hydraulic servo valve.In the first chapter of the paper, the urgency of servo valve used in the modern electro-hydraulic control system in high-flow and high-frequency response was introduced briefly, the contradiction between high flow and high-frequency response was analyzed and its technical difficulties were pointed out. The significance and value of this research were further cleared through a large amount of analysis on the research status of the servo valve. At last, the research objectives and the main contents of this topic were both proposed, which was useful for the later work.In the second chapter, the Mathematical model and the AMESim simulation model was established on the basis of the composition of the object studied as well as the working mechanism of its various parts was analyzed deeply. The effects of some parameters was analyzed theritically based on the mathematical model, and the simulation model was verified through experimental research, whichIn the third chapter, the influence of the pipeline parameters and accumulator parameters on the dynamic characteristics of the main valve was analyzed based on simulation model, and AMESim genetic algorithm was used to optimize the matching parameters. For the steady-state flow force of the main valve port calculations, the FLUENT software was involved. Referring to the flow force calculated in FLUENT, the flow force coefficients in AMESim model can be adjusted to accurate values, and the steady-state flow force generated on the condition that the flow was from B to A was confirmed to be smaller. Based on the model, a shock phenomenon of the main valve spool and zero position drift phenomenon of the pilot valves were found. Fortunately, reasonable solutions were proposed after a large number of simulation studies.In the fourth chapter, the control characteristics under different control methods were simulated, linear control and nonlinear control included, and the later one was verified to be the most effective method in solving the contradiction between high frequency response and high flow. Control strategies and control solutions followed, finally, the optimal parameters of nonlinear control were obtained through the simulation model, which laid a solid foundation for the experimental study later.The fifth chapter gave a brief description of the high flow valve test platform design and the test methods. The experimental data processing was completed by communicating MATLAB with NI data acquisition card and MATLAB_XPC was applied for real-time control system. The parameters optimized with the simulation model were applied for the experimental study of step response, frequency response and hysteresis characteristics under nonlinear control. Based on these studies, the model was verified to be accurate in the time domain as well as frequency domain and the nonlinear control method was confirmed to be more superior.A comprehensive summary was made in the last chapter, also both the research problems and the focal points for the future research were put forward.