| As a kind of MOEMS inertial sensor,the micro-grating accelerometer has the advantages of high theoretical accuracy,high sensitivity,and anti-electromagnetic interference.It has broad application prospects in national defense and military navigation and guidance,and gravitational wave detection.However,the optically weak signals of micro-grating accelerometers are easily affected by various noises and light source fluctuations,which brings challenges to the signal processing scheme of high-precision micro-grating accelerometers.In addition,although the micro-grating accelerometer has theoretically ultra-high precision,it also has the problems of too small dynamic range and poor linearity,which are also the problems that must be faced to achieve high-precision and large dynamic range acceleration detection.Therefore,it is necessary to design a set of high-precision micro-grating accelerometer measurement and control circuit for the above problems.In this paper,taking the micro-grating accelerometer as the research object,in order to improve the detection performance of the sensor,a control and signal detection circuit is designed pertinently,which realizes the modulation and demodulation of semiconductor laser,photoelectric detection,electromagnetic force feedback closed-loop control and other key technologies.The research work of this paper is mainly summarized in the following aspects:Firstly,the overall structure of micro-grating accelerometer is introduced in detail;on the basis of introducing the structure of the micro-grating accelerometer,the basic theory and sensitive mechanism of the micro-grating accelerometer are studied;the factors affecting the accuracy and dynamic range of the micro-grating accelerometer are analyzed,and the solution of electromagnetic force closed-loop feedback control is discussed and designed;the principle of electromagnetic force closed-loop control is studied,and the feasibility of the electromagnetic force feedback control scheme is preliminarily verified.Secondly,the signal detection scheme of laser modulation and demodulation is theoretically analyzed and verified by simulation;The action mechanism of feedback torque converter coil permanent magnet is studied,and the simulation model is established on the ANSYS software platform.Then the functional relationship between coil turns and driving force and that between coil current and driving force are simulated and analyzed by using ANSYS software.The theoretical analysis and system modeling of the sensor closed-loop control system are completed,and the effects of PI control parameters and sensitive structure quality factor on the stability and bandwidth of the control system are analyzed in the Simulink environment,which verifies the feasibility of the control scheme,and provides a basis for the design of subsequent actual circuit parameters.Then,according to the proposed control and signal detection scheme,the control and signal detection scheme including laser modulation and demodulation circuit,photoelectric detection circuit and electromagnetic force feedback control loop are designed in detail.According to the requirements of high-precision detection,the semiconductor laser light source,photodetector and low-noise operational amplifier are selected,and the equivalent noise of the key parameters of the photodetector is analyzed.According to the requirements of the control system,the FPGA main control chip,ADC and DAC are selected.Finally,the circuit board is made,the hardware description language is written,and the debugging of the whole circuit is completed.The key performance indicators of the micro-grating accelerometer are tested;the laser modulation and demodulation scheme and the electromagnetic force feedback control scheme designed in this paper are tested respectively.Compared with the above two schemes,the results show that the signal-to-noise ratio of the modulated system is improved by about 10d B in the working bandwidth of 0.1Hz to 10Hz compared with the unmodulated,which validates the feasibility and practicability of the modulation and demodulation scheme described in this paper,and achieves the expected goal.Similarly,compared with the open-loop system,the dynamic range of the micro grating accelerometer with the electromagnetic force closed-loop control system is increased from6ug to 1mg,which is nearly 167 times higher than that of the open-loop system;the closed-loop scale factor is 3384V/g;the noise level of the system in the bandwidth of 0.1Hz to 10Hz is about 10ng/0.5,which verifies the feasibility and practicability of the electromagnetic force feedback control scheme described in this paper. |
