Research On Key Technologies Of High-Pressure High-Speed On-Off Electro-mechanical Converter

With increasingly sophisticated and extensively used computer technology, the digital electro-hydraulic control technology becomes an important mean for achieving electro-mechanical machinery industry and is widely used in many sections of national economy and social surroundings, such as aerospace, automotive, metallurgy, arms control, agricultural machinery, and construction machinery, due to its advantages of high-speed, high-precision control of hydraulic systems. The high-speed on-off electro-mechanical converter is the core technology. Compared with the conventional converters for servo valves or proportional valves, the high-speed on-off electro-mechanical converters can be directly connected with the computer without the need for D/A converters and has the advantages of low cost, easy processing, strong anti-pollution, high repeatability, high stability, high reliability, and low energy consumption. So the high-speed on-off electro-mechanical converter has come to a hot topic of researches on the electro-mechanical converters. Researches on high-pressure high-speed on-off electro-mechanical converters would improve the overall performance index of digital electro-hydraulic control systemes and promote the theory, technology and equipment of related areas, to better meet the ever-increasing productions and livings.Based on theory analysis, numerical simulation and experimental study, the key technologies of high-pressure high-speed on-off electro-mechanical converters are systematically, deep researched in the thesis. Based on the research of moving-iron high-pressure high-speed on-off electro-mechanical converters, taking comprehensive consideration of closing performance and opening performance for long stroke condition, analyzing the dynamic process of magnetic changes, discussing the influence of structural parameters on the static and dynamic characteristics, and developing the planar-polar and conical-polar high-pressure high-speed on-off electro-mechanical converters are presented. And simulation and experimental results show that these two electro-mechanical converters match different characteristics of the spring load to apply to different working stroke. Aiming at the leakage problem of the single-piece high-pressure high-speed on-off electro-mechanical converters, a high-pressure high-speed on-off electro-mechanical converter with permanent magnet (PM) shielding is proposed, and the simulation analysis and experimental study are conducted. The results show that the PM shielding strategy can reduce the flux leakage, avoid self-locking force inherited from polarization of the permanent magnet flux, increase electromagnetic force, and enhance closing performance by forming a mutual constraint of the permanent magnet flux and the magnetic field coil flux. As an application instance, a high-pressure high-speed on-off electro-mechanical converter is applied to the electro-hydraulic vibration impact system, and the original servo valve is replaced by a high-speed on-off valve. And simulation and experimental results show that new system performance meets the design requirements with lower cost.The main content of each chapter is summarized as following:In chapter 1, from standpoints of the high-speed valves for the digital electro-hydraulic control technology, the research progress of the high-pressure high-speed on-off electro-mechanical converters is introduced. The structural and high-speed feature, development trend of the electro-mechanical converters for valves are summarized.In chapter 2, the function, classification and structural characteristics of electro-mechanical converters are described. Future, the typical structure, the working principle and performances of the widely used moving-iron high-speed on-off electro-mechanical converters are introduced. The dynamic mathematical model of electro-mechanical converters is established. Taking the calculation of electromagnetic force as the central task, the magnetic circuit analysis and finite element analysis are introduced. The characteristics and applicable fields of the two analytical methods are pointed out.In chapter 3, the planar-polar and conical-polar high-pressure high-speed on-off electro-mechanical converters are developed. Being conditional on long working stroke, the influences of dynamic process of magnetic field/magnetic field changes on the static and dynamic characteristics are analyzed as the design basis. By explaining the mechanism of structural parameters, the structure parameters of the two long working stroke electro-mechanical converters are specified. The principle, constitution and test methods of static and dynamic test systems are introduced. Based on the static and dynamic test systems, the static and dynamic characteristics of two long working stroke electro-mechanical converters are measured, and compared with simulation results.In chapter 4, the structure and working principle of the new high-speed on-off electro-mechanical converter with permanent-magnet (PM) shielding are proposed. Using combined methods of magnetic circuit analysis and finite element simulation, the influences of main structure parameters on static and dynamic characteristics are discussed. Based on the energy conversion relations in dynamic process and the failure mode under oil pressure, temperature and strength analyses are carried out using the finite element tools and results are all within the limits permitted. Compared the PM shielding type high-pressure high-speed on-off electro-mechanical converters with the single-piece type high-pressure high-speed on-off electro-mechanical converters, the experimental results verify the effectiveness of PM shielding strategy.In chapter 5. as an application instance of high-pressure high-speed on-off electro-mechanical converters, the electro-hydraulic vibration impact system based on high-speed valves is developed. The simulation models of the high-pressure high-speed on-off electro-mechanical converter, the high-speed valve, and the electro-hydraulic vibration impact system are established to obtain their static and dynamic characteristics. The influences of the high-pressure high-speed on-off electro-mechanical converter on the electro-hydraulic vibration impact system are conducted. Through the impact energy test system for the electro-hydraulic vibration impact system, the impact forces are measured and compared with the simulation results.In chapter 6, all achievements of the dissertation are summarized and the further research work is put forward.