Study Of The Control System Of The Axial-Drive Electrostatic Micromotor With Levitated Rotor

With the development of MEMS (Micro-electromechanical Systems), micromotor, as the power element and important execution unit, is always one of the research focus in the field of MEMS. Micromotor not only has driving function, but also precision Control. It has wide prospect in the region of information, medical treatment, aerospace, military and so on. In order to ensure the micromotor working well, it is important to keep the rotor rotating stably. This paper mainly studies the closed-loop control system for the axial-drive electrostatic micromotor with levitated rotor.The main research content and results of this thesis are as follows:Firstly, the configuration and the mechanism of suspending and rotation of the micromotor are introduced. The 2nd order of dynamic mathematics model and the equivalent model of differential capacitance of the micromotor are established. To achieve closed-loop control of motor, switch-control method is proposed. Secondly, using the method of numerical calculation or finite element analysis, Simulation curves about the changing of the differential capacitance and electrostatic moment are gained.The dynamic model is simulated in Simulink environment,seeing about the speed response without disturb input or with disturb input. It has validated the feasibility of the control method.And the rotation mathematics model is preliminary establishedFinally, design the measurement and control system. As the aspect of signal detection, a weak capacitance signal measurement based on charge integral amplifier, Cross-Correlation detection and lock-in, is proposed. The measurement is simulated in ORCAD environment. According to the simulation, the feasibility is validated. It also has important reference for the practical circuit components choice, parameters setting and system debug. At the same time, a DSP controller based on SEED-DEC2812(TMS320F2812 platform) is designed for the closed-loop control.The measurement and control system discussed in this thesis has some main advantages below:(1)Sine wave generator with DDS is controled by DSP. It has the advantages of high stability frequency output, high precison, high resolution, and easily adjustable frequency and phase. (2) The weak capacitance signal measurement proposed has the advantages of low drift, high signal/noise ratio, high resolution, and simple circuit. With the DSP controller, the reset, spin up, and open-loop operation are accomplished. When it works in closed-loop control, the Capture Port captures and deals with the differential capacitance signal from signal detection circuit, then ouputs four-channel square waves possessing some control logic. The waves dominate the on-and-off time of four-channel analog switchs for the load of feedback voltages.