Detection Circuit Of Small Capacitance For MEMS Gyroscopes Used In Rotating Ammunitions

Traditional gyroscopes are not suitable for attitude measurement of high rotatingammunitions, because high rotating ammunitions have the features of high overload, highdynamic and small space, and traditional gyroscopes have the disadvantages of range, size,dynamic characteristic and anti-overload when using in high rotating ammunitions. Aiming atthe difficulty of high rotating ammunitions attitude measure, a new MEMS gyroscope used onrotating ammunitions is designed by our group. Because high rotating ammunitions have highaxial direction rotation while flying, the gyroscope is drove by the axial direction rotation.The new MEMS gyroscope has the advantages of low cost, small size, big measure range andhigh anti-overload ability, it has a good prospect. The gyroscope senses angle rate throughdifference capacity to decrease temperature nonlinearity, inhibit disturbance accelerometerand simplify fabrication technology. For the capacity change is very small, the output ofgyroscope is week, so a point technology of gyroscope’s signal extraction is high accuracycapacity detection. The aim of this study is to design high accuracy capacity detectioncircuits.This paper includes analysis of gyroscope’s principle and electronic characteristics,design and achievement of static and dynamic capacity detection circuits, gyroscope’scharacteristics analysis on detection circuits.Firstly, the principle and dynamic model of the MEMS gyroscope used in rotatingammunitions is analyzed. The characteristic of the gyroscope output signals is detailed. Thegyroscope’s electronic indexes are calculated based on high rotating ammunitions’ motionparameters and the MEMS gyroscope’s structure parameters, theoretical indexes for the latterdetection circuits are supplied by the gyroscope’s electronic indexes.Secondly, because of current processing technical, the structure parameters of gyroscopeare not completely same with the design. This problem gives rise to the mismatch of polarplate. It will effect for the output signal detection of gyroscope. Aiming at this question, thestatic detection circuit is designed on capacity detection chip AD7747. The experiments showthat the static detection circuit can meet requirements on performances and indexes.Then after based on the analyzing the advantages and disadvantages of a variety of small capacitance detection principle, in view of the rotating cylinder with MEMSgyroscope capacitance changes the characteristics of the signal, The charge and dischargemethod is used for the design of capacitance detection circuit. And through the C-Vconversion circuit, carrier circuit, signal conditioning circuit and filter circuit module torealize the dynamic capacitance detection circuit, And the function and performance of thecircuit is verified by experiment.In the end, the capacitance characteristics and the solution rate sensitive characteristics ofthe rotating ammunitions used MEMS gyroscope are corresponding detected through thestatic capacitance detection circuit and the dynamic capacitance detection circuit. Test resultsshow that gyro output signal can be extracted by the design of the static and dynamicdetection circuit. At the same time, the output signal of the rotating ammunitions used MEMSgyroscope is consistent with the theoretical analysis, which is able to complete detection rateof diagonal.In summary, the static capacitance detection circuit and the dynamic capacitancedetection circuit designed by this article can meet the output requirement of new gyroscope,which has laid a good foundation for the optimized design of the subsequent new gyroscope.At the same timeThe capacitance detection circuit is designed in this article. It has a good engineeringpractical value, which is not only can be used for new MEMS gyro signal detection, and canalso be used for the other capacitance signal detection field.