Research On Dsp-Based Control System For Six-Axis Electrostatically Suspended Micro-Machined Accelerometer

Electrostatically Suspended Micro-machined Accelerometer(ESMA) not only can measure the small displacement, acceleration, and an insignificant force, but also can be used in the microgravity environment of space to measure the vibration and non-conservative forces. ESMA based on micro-electromechanical systems (MEMS) technology can be integrated with the detecting circuit in one device, which will become a MEMS device with great prospect. Some research on ESMA has been started by the US, Japan, British. With the further development of China's space technology, ESMA in China will have a wider application space.Key technologies of realizing Electrostatically Suspended Micro-machined Accelerometer include simulation technique, micro-mechanical manufacturing technology, small capacitance detection techniques, suspension control of proof mass, noise measurements, environmental measurements, and so on.This issue focuses on the design and realize of the suspension control system of proof mass for six-axis Electrostatically Suspended Micro-machined Accelerometer. And the combination of simulation and experimental methods are used to analyze the characteristic of control system. This issue studies the content of the control system design and analysis, including control design and simulation models, and small capacitance detection technology,implementation of control system on digital signal processor (DSP). The main contents of this paper are as follows:First, the structure and characteristics of ESMA are introduced and analyzed. And the working principle of the ESMA is given here. Combined with the capacitance measuring principles, the model and dynamic equation of the ESMA are proposed. The linear Reynolds equation is used to describe the squeeze damping of the device, which can provide reference parameters for the simulation of the control system.Secondly, two different control models are discussed and compared here: Fuzzy-PID control algorithm and PID control algorithm. Here also discussed the centralized control strategy and not-centralized control strategy using to achieve synchronic control of six-DOF acceleration measurement and control.Finally, in order to realize the closed-loop electrostatic suspension control system, a digital close-loop controller is designed, which is implemented on digital signal processer (TMS320f28335). The control system of six-axis ESMA requires multiple channels of data to be read and write simultaneously, so extension circuit using to realize A/D convert and D/A convert is necessary. ADC and DAC chips AD7656 and AD7835 are adopted here,which can be controlled by the DSP using Assembly language and C language. Then, the 7-channel capacity measuring data and 14-channel voltage feedback data can be read and write simultaneous under the control of multi-channel controller.