Research And Experiment On Digital Electrostatic Compensation And Frequency Tuning Technology For Silicon Micro-machined Gyroscope

With the rapid development of MEMS technology, silicon micro-machined gyroscope is more and more attention. Silicon micro-machined gyroscope is a kind of microsensor with measuring angular velocity, which has the advantages of small volume, light weight, low power consumption, low cost, and easy to mass production. But due to the limitation of processing technology, the precision of silicon micromechanical gyroscope is still relatively low. An important factor restricting its precision is the error, such as elastic beam size deviation, asymmetry error, residual stress, cross-coupling error and so on, existing in manufacture processing. All these affect the improvement of the performance of silicon micro-machined gyroscope. Under the existing process level, introducing sense closed-loop design, quadrature coupling stiffness correction, electrostatic frequency tuning techniques,and combined with the flexible digital circuit, the accuracy of silicon micro-machined gyroscope can be effectively improved.This dissertation is to improve the performance of silicon micro-machined gyroscope developed in our laboratory with the function of sense mode electrostatic force feedback,quadrature coupling stiffness correction and electrostatic frequency tuning. Relevant digital control technology is studied in this dissertation. The main research works and innovations are as follows:1. Design and implementation of the digital closed-loop system of drive mode for silicon micro-machined gyroscopeDiscrete domain model of drive mode is deduced by the frequency correction of bilinear transformation. The corresponding linear discrete model in the digital phase locked loop and automatic gain control are built, respectively and the stability of the control loops are analyzed. The stability conditions of the phase and amplitude control are given. The simulation results and experiments verify the stability of the digital closed loop drive of the gyroscope.2. Research on the closed-loop of sense mode for silicon micro-machined gyroscopeThe digital corrector combined with PI controller and phase lead controller is designed.And the digital-analog hybrid simulation system is established in Simulink. The performance of gyro digital control system is tested in open-loop detection mode and closed-loop detection mode respectively. Compared with open-loop detection, the performance of closed-loop detection is improved significantly; working bandwidth extends from 6 Hz to 93 Hz.3. Research on the quadrature coupling correction for silicon micro-machined gyroscopeAs to the structure of silicon micro-machined gyroscope with quadrature correction,quadrature force correction and quadrature coupling stiffness correction technology are proposed, the closed-loop control system of which are established respectively. The simulation results indicate that the feasibility of the two correction technology. The experiment comparisons on these two correction technologies are carried out. The experimental results show that quadrature correction technology can reduce zero bias and improve drift tendency of the gyroscope, the effect of quadrature coupling stiffness correction is better than that of quadrature force correction.4. Research on the automatic mode-matched control for silicon micro-machined gyroscopeDue to the flexibility of digital measurement and control system, three automatic mode-matched methods are utilized based on the phase-frequency characteristics of quadrature coupling signal, low-frequency modulation excitation signal and the BP neural network. These methods are analyzed in theory, simulation,and experiment, respectively.The results show that these methods can be work at a temperature range of -40? to 60? with the frequency offset less than 1 Hz, 0.5 Hz, and 0.016 Hz.5. Analysis and optimization of the digital demodulation algorithm for silicon micro-machined gyroscopeIn view of the demodulation method and algorithm requirements for silicon micro-machined gyroscope, Multiplication demodulator (MD), Least mean square demodulator (LMSD), Fourier demodulator (FD), all-phase FFT demodulator (APFD) and synchronous integral demodulator (SID) are designed. By comparing these demodulation algorithms on startup, the ability to suppress noise and hardware resource utilization, the synchronous integral demodulator (SID) is chosen as the demodulation algorithm of the digital control system for silicon micro-machined gyroscope, which guarantees the signal efficiency and presion.6. Experiments on the digital electrostatic compensation and frequency tuning technologyWith reference to the testing conditions of domestic micro-machined gyroscope, the experiments of the tested gyroscope are carried in three states: sense open-loop & quadrature stiffness closed-loop & mode-mismatched (state 1), sense open-loop & quadrature stiffness closed-loop & mode-matched (state 2) and sense closed-loop & quadrature stiffness closed-loop & mode-matched (state 3). The test results show that state 3 achieves the best performance. Compared with state 1, the bias stability and the angular random walk are improved from 15.13°/h and 2.63°/h/?Hz to 1.3°/h and 1.320/h/?Hz, respectively. Compared with state 2, measuring range is increased from ±100°/s to ±400°/s, scale factor nonlinearity is decreased from 649 ppm to 21 ppm, and working bandwidth is expanded from 5 Hz to 90 Hz.The experiment results show that the closed-loop of sense mode effectively improve the performance of scale factor and expand measurement range and banwidth, the mode-matched technology effectively improve the mechanical sensitivity and reduce the noise.This dissertation provides an effective technical way to improve the performance of silicon micro-machined gyroscope and a reference value for the subsequent high-performance micro-machined gyroscope.