| Electro-hydraulic control elements as a bridge of connecting electrical parts and hydraulic parts, is the core component of servo system. The performance of servo system is a large extent depended to its propoties. With the development of computer technology and the expansion of electro-hydraulic servo system applications, electro-hydraulic control elements are required to reach higher demands, such as: high frequency response, large discharge, digital, anti-pollution. 2D digital valve as one of the electro-hydraulic control elements possesses anti-pollution, fast response, high repetition accuracy and digital control, etc. It is good to meet above-metioned requirements. The electromechanical converter as a key component in 2D digital valve, the improvement of its frequency response can greatly enhance the overall performance of the valve. So it is also necessary to research on the electromechanical converter.Hybrid stepping motor as the electromechanical converter of a 2D digital valve with anti-interference, high frequency response, high positioning accuracy, little influence by friction and other nonlinear factors , etc. But it also brings the problems of control: (1) under the traditional control way, there is a contradiction between the quantitative accuracy and response speed. Although it is suggested that continuous tracking algorithm use, but this method only applies to open loop control, easily to cause stepper motor out of step. (2) input the course of any control signals, the rotor can quickly respond to signals, pinpoint any location and the rotor without loss. The major work and the results are as follows.1. For fast frequency response, digital, strong anti-pollution and other requirements, 2D digital valve uses a servo screw mechanism in structure. In the second chapter, mathematical model of the 2D digital valve's servo screw mechanism is built and it is simulated under Matlab environment. Simulation results: step response time is about 1 ms; the bandwidth is about 150 Hz at -3dB gain, 90°phase lag for sinusoidal signal which amplitude is 25% of the largest valve opening.2. Hybrid stepping motor as an electromechanical converter of 2D digital valve, the frequency response affects the overall performance of the valve. In the third chapter, mathematical modeling of the electromechanical converter is built and simulated. Simulation results: the bandwidth is about 230 Hz at -3dB gain, 90°phase lag for sinusoidal signal which amplitude is 25% of the largest valve opening.3. For the hybrid stepping motor as an electromechanical converter of 2D digital valve exists two control problems which are mentioned above. This paper especially designes an embedded controller which uses DSP (TMS320F2812) as the master chip. And a synchronous servo control algorithm is put forward; using location and current double closed-loop system to ensure that angular displacement of the rotor keep tracking of the input signal.4. An experimental platform is established. And then the experimental investigations of the electromechanical converter and 2D digital valve properties are carried out respectively. The results show that they have good static and dynamic characteristics. The experimental results of electromechanical converter: step response time is about 6 ms; the bandwidth is about 210 Hz at -3dB gain, 90°phase lag for sinusoidal signal which amplitude is 25% of the largest valve opening. The experimental results of 2D digital valve: step response time is about 8 ms; the bandwidth is about 130 Hz at -3dB gain, 90°phase lag for sinusoidal signal which amplitude is 25% of the largest valve opening. Compared with the simulation curves, the results coincide.5. The experimental results prove that the 2D digital valve which uses synchronous control algorithm has good static and dynamic characteristics. It achieves a higher frequency response, broadens the scope of application and solves the control problems. If 2D digital vlave uses a hollow cup low inertia stepper motor or a three-phase hybrid stepping motor can further improve the valve's frequency response.
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