Research On Low Inertia Electromechanical Converter

As one of the electro-hydraulic control elements, digital valve is applied widely because of its advantages, such as fast response time, strong ability to fight pollution, repeat direct numerical control, high precision etc. Low inertia electro-mechanical converter is a conversion interface used on digital valve, its performance largely determine the entire digital valves and even the whole control system performance. Stepper motor is an actuator which can change electrical pulse signal into position signal, and can directly control the digital valve. Selecting the low inertia permanent magnet stepper motor as the actuator and comparing different control methods to improve frequency response of the electro mechanical converter.Based on permanent magnet stepper motor, analyzing its structure and principle and presenting mathematic model and the current and position compensation control scheme. A control system is designed for magnetic disc stepper motor based on DSP and used as a low-inertia elector-mechanical converter for digital valve. The research is embedded in current and position of double closed loop control. The experimental results show that using the low-inertia motor as an elector-mechanical converter, the rise time is 2.1ms for 25% input signal and the bandwidth reaches 275Hz at -900 phase angle for 25% input signal, and that high-frequency response of digital servo valve can be realized.The contents of each chapter are listed as follows:In chapter 1, the research status of digital valve, electro-mechanical converter and permanent magnet stepper motor are summarized. The paper expounds the purpose and meanings of this research.In chapter 2, this paper selects permanent magnet stepper motor because of its low inertia and high frequency response. Describes the principle of electro-mechanical converters and establishes its mathematical modeling, draw the torque equation, voltage equation, and the kinetic equations of two-phase permanent magnet stepper motor and proposed current vector control strategies.In chapter 3, a controller is designed for low-inertia magnetic disc stepper motor based on DSP, with the current and position of double closed loop control. Introduce the hardware and software system. and the special DSP controller is designed which is used for small flow 2D digital valve. The implementation of algorithm which is used to produce signal of current and position loop is expoundedIn chapter 4, direct current feedback used in order to improve the elector mechanical converter frequency response. Current and position correction can compensate poor track with high frequency. Analysis of compensation principle and theory, experimental results show that the compensation effect of electro-mechanical converter frequency response has been greatly improved.In chapter, to build a permanent magnet stepping electro mechanical converter experiment platform, do the experiment of dynamic characteristics. The controller has a good step response, rise time up to 2.1ms; bandwidth of 275Hz, the compensation effect before the increased 66%.In chapter 6, all achievements of the paper are summarized and new prospect is put forward.