Research On Novel Electro-Mechanical Converter For2D Valve And Its Application

In recent years2D valve based the principle of hydraulic servo screw mechanism has been widely used in the metal material tester, earthquake simulator and areas of aeronautics and astronautics since it has advantages of simple structure, fast dynamic response, high accuracy and excellent anti-pollution capability. The electro-mechanical converter for2D valve is commercial hybrid stepping motor, which was not specially developed for valve electro-mechanical converter but for control and driving motor of electro-mechanical servo system. Therefore it has shortcomings of inflexible structure, large rotating inertia, limited dynamic response and deficiency of high pressure resistance, which heavily influence the application extension and structure innovation of2D valve. As a crucial component of2D valve, electro-mechanical converter functions as the bridge between electrical signal and mechanical movement, and it has a decisive influence on the overall performance of2D valve. The aim of developing novel electro-mechanical converter is to improve performance of2D valve and extend its application area, which also acts as the key of whether2D valve can be further developed or not. The research to novel electro-mechanical converter structure has both theoretical significance and engineering practical background. The main research content and achievements in this dissertation are listed as follows:1. The disadvantages of commercial hybrid stepping motor are deeply analyzed and main defects such as output torque loss, low power weight ratio, large rotating inertia, complicated structure and driving circuit and deficiency of high pressure resistance are pointed out.2. Two novel structures of electro-mechanical converter for2D valve, i.e. rotary electromagnet with low inertia and rotary electromagnet with high pressure resistance are proposed. The working principles are analyzed and correctness of schemes are validated both by finite element analysis. The method of constituting electro-mechanical converter based on approach of stator axial phase separation is deeply researched and another three new structures, i.e., rotary electromagnet with single phase, direct-acting electromagnet with single phase and direct-acting electromagnet with double phases are deduced from the scheme of rotary electromagnet with high pressure resistance.3. Two prototypes of rotary electromagnet with low inertia with different rotor tooth numbers are manufactured. The performance of electromagnets are studied by using approaches of magnetic circuit analytical method, finite element simulation and experimental study. Experimental results illustrate that torque-angle characteristics of electromagnets with rotor teeth number of50and18are both sinusoidal waveform, whose maximum static torque under current of3.5A reach about0.09N·m and0.082N·m, respectively. And the amplitude frequency widths with-3dB are about220Hz and125Hz, respectively. The phase frequency widths with-90°are about220Hz and130Hz, respectively. The rise times of step response are about5.6ms and5.5ms, respectively. The experimental results are in good accordance with simulated results. It can be concluded that the electromagnets have both excellent static and dynamic characteristics, which is suitable for applications where high dynamic response is perferred. Besides, from comparison of two prototypes with different rotor tooth number it can be found that the main static and dynamic characteristics of electromagnet with double salient structure on both stator and rotor can be further improved by increasing tooth number. Therefore different electromagnets can be obtained by adjusting tooth number which is suitable for different applications such as electrohydraulic servo valve, proportional valve and etc., respectively.4. The prototype of rotary electromagnet with high pressure resistance is manufactured. The performance of electromagnet is studied by using approaches of magnetic circuit analytical method, finite element simulation and experimental study. Experimental results illustrate that torque-angle characteristic of electromagnet with rotor teeth number of15is sinusoidal waveform, whose maximum static torque under current of3.5A reaches about0.19N·m. The amplitude frequency width with-3dB and phase frequency widths with-90°are about113Hz and65Hz, respectively. The rise time of step response is about18ms. The experimental results are in good accordance with simulated results except for slight deviation of cogging torque. It can be concluded that the electromagnet has both good static and dynamic characteristics, which can be used as electro-mechanical converter where high pressure resistance is preferred.5. In order to solve the problem that traditional hydraulic servo screw mechanism can not have both low leakage of pilot stage and fast dynamic response, a novel hydraulic servo screw mechanism that has "groove to groove" pilot stage is proposed in this paper. The mathematical model is established and transfer function is derived. Its dynamic characteristics are simulated and results show that the simulated amplitude frequency width reaches about280Hz/-3dB and rise time for step response is about4.4ms, which demonstrates that the novel hydraulic servo screw mechanism has excellent dynamic response even with zero lap of pilot stage.6. In order to act as an application example of rotary electromagnet with high pressure resistance, structures of non-direct driving2D valve is put forward, which are based on hydraulic servo screw mechanism that has "groove to groove" pilot stage. The prototype is designed and manufactured. The test rig is built and main static and dynamic characteristics are measured. Results show that with system pressure of20MPa the zero position leakage and rated flow of prototype are about5.4L/min and100L/min, respectively; the amplitude frequency width with-3dB and phase frequency widths with-90°are about17Hz and10Hz, respectively. The rise time of step response is about46ms with almost zero steady error.