Research On The Mode-localized Accelerometer Based On Multi-degree Of Freedom Weakly Coupled Resonators

In recent years,the mode localization phenomenon has been widely used in various types of resonant sensors,and the output metric based on the amplitude ratio exhibits ultra-high sensitivity and better robustness than the traditional frequency output.The mode-localized accelerometers based on multi-degree of freedom(M-Do F)weakly coupled resonators(WCRs)are proposed in this thesis.The mode localization phenomenon of 3-Do F and 4-Do F WCRs is studied,and several key issues including nonlinearity suppression,feedthrough signal elimination,and temperature drift suppression are studied.First,the mode localization phenomenon and key performance parameters of M-Do F WCRs are analyzed.The dynamic model and sensitivity model of 3-Do F and 4-Do F WCRs are established.The sensitivity enhancement mechanism of WCRs based on the increasing of the Do F is analyzed.For the WCRs with higher Do F,the sensitivity based on amplitude ratio can be more significantly improved than that based on frequency.The improvement effect is mainly determined by the coupling factor.The smaller the coupling factor,the more significant the improvement.The mode-localized accelerometers based on 3-Do F and 4-Do F WCRs are designed.Second,the nonlinear characteristics of the M-Do F WCRs are analyzed and a suppression method is proposed.The amplitude ratio-based sensitivity of M-Do F WCRs in full range is analyzed,and that the M-Do F WCRs has a larger linear working range is revealed.The sum of amplitude ratios is used as the output metric to suppress the nonlinearity of the M-Do F WCRs near the veering point,and the weak nonlinearity in the linear working range is further improved.Finally,the sum of amplitude ratios of the M-Do F WCRs is tested to verify the feasibility of proposed method.Third,the self-temperature drift suppression characteristic of the M-Do F WCRs accelerometer is theoretically analyzed and experimentally verified.Firstly,the theoretical temperature drift model of the amplitude ratio and frequency of the M-Do F WCRs accelerometer are established.Secondly,the main factor affecting the amplitude ratio and frequency is verified to be the thermal stress by the COMSOL finite element simulation analysis,then the stress isolation structure is used to further weaken the effect of the temperature on the accelerometer.Finally,the temperature characteristic of the 3-Do F mode-localized accelerometer is tested and it is proved that the effect of the temperature on the mode-localzied accelerometer with stress isolation structure has been significantly suppressed and the amplitude ratio has a superior self-temperature suppression capability.Finally,the mode localized accelerometers based on M-Do F WCRs are fabricated and measured.Firstly,3-Do F and 4-Do F mode-localized accelerometer are fabricated using siliconon-glass(SOG)technology.Then the amplitude-frequency characteristics of the M-Do F WCRs accelerometer in the frequency domain are measured and the mode localization phenomenon of M-Do F WCRs is observed.In the time domain the amplitude ratio-based sensitivity of the3-Do F and 4-Do F mode-localized accelerometer are measured to be 3012 and 6828 times higher than that of frequency respectively,furthermore,the noise floor are 3.49 μg/√Hz and65.76 ng/√Hz respectively.In summary,this thesis proposes the mode-localized accelerometers based on M-Do F WCRs which suppresses the nonlinearity near the veering point,verifies the self-temperature drift suppression characteristics,achieves an ultra-high sensitivity and lower nosie floor and owns important application prospects in the field of micromechanical resonant accelerometers.