Research On Key Technologies Of Accuracy Improvement Of Quartz Flexible Accelerometer

Quartz flexible accelerometer is widely used in the field of high-precision inertial navigation due to its high-accuracy,small-size and stability.When the traditional analog quartz flexible accelerometer transmits the digital information to the navigation computer through the open-loop and analog-to-digital conversion circuit,it is easy to produce noise and sharply degrade performance;The existing digital solutions adopt the method of separating the accelerometer sensor from the servo circuit,which results in the long-distance transmission of capacitive signals that are susceptible to interference.Therefore,the inevitable development trends of quartz flexible accelerometers are high-precision,high-integration and digital-output.In view of the above problems,based on the research of technology for improving accuracy while taking into account the integration,this thesis designed a digital servo circuit,further optimized the capacitance detection circuit which is the main source of noise in the circuit,and finally completed the development and testing of the accelerometer prototype.The following researches have been done in this thesis:1)Research on digital closed-loop servo scheme and error analysis.According to the requirements of high-accuracy accelerometer,this project completed the design of the capacitance detection circuit,digital controller,and feedback driving circuit,and then completed the circuit design and debugging of the digital servo loop.Then this thesis theoretically analyzed the error of each module,and performed the system noise grading test to determine that the noise of the capacitance detection circuit is the most important factor affecting the accuracy of the system 2)Analysis and performance comparison of quartz flexible accelerometer capacitance detection scheme.According to the working principle of differential capacitance sensor,several capacitance detection schemes suitable for quartz flexible accelerometer were introduced in detail.After that,the noise models of different schemes were established,the theoretical derivation and calculation of noise were carried out,and it was finally determined that the single carrier modulation and demodulation method is the best performance capacitor detection scheme.3)Research on single carrier modulation and demodulation capacitance detection accuracy improvement method.Based on the analysis of the main factors that affect the performance of the single carrier modulation and demodulation circuit,the topology of each part were optimized in consideration of the scheme accuracy and implementation complexity.This paper proposed a new method of phase sensitive demodulation using sample holder,which is beneficial to suppress the influence of high-frequency carrier waves,increase the gain of the capacitance detection circuit,and reduce the supply voltage and static power consumption of the device.4)Experimental verification and analysis of precision improvement of quartz flexible accelerometer.Completed the development of integrated prototype of quartz flexible accelerometer,set up an experimental platform,and tested various performance indicators of the accelerometer.The experimental results show that the quartz flexible accelerometer designed in this paper has excellent performance,and the acceleration sensitivity values that were originally obscured in the noise of the capacitance detection circuit have been reflected.The quartz flexible acceleration sensor developed in this subject has the advantages of high-integration,high-precision,and direct digital-output,which proves the effectiveness of the key technology research on accuracy improvement in this paper.