Dynamic Characteristics Of High-g Piezoresistive Accelerometer

High-g piezoresistive accelerometer is essential to the accurate measurement of theprojectile penetration acceleration during the "smart" munitions system development process.But in practical application, the dynamic characteristic and measuring accuracy of the high-gaccelerometer is volatile because of the high-g pulse stimulation. Aiming at this problem, thedynamic characteristics of high-g piezoresistive accelerometer was researched, from thefollowing two aspects.(1) Influence of the damping factor on the dynamic characteristics during the firstpackage process of sensor core.Based on the typical second-order system model, the model that described theaccelerometer response to the unit impulse signal and semi-sine pulse signal was derived. Theinfluence of the damping on the dynamic characteristics of the high-g accelerometer wasstimulated in both time domain and frequency domain where the special applicationenvironment, short rise-time and high natural frequency were considered. The results showedthat the dynamic characteristics of the high-g accelerometer could be improved obviouslywhen the damping ratio was between0.1~0.25and the test precision of the system could beimproved as well. By comparison of three accelerometers with different damping factors thesimulation model was verified and the validity of the simulation provided the important basisfor the adjusting of the damping ratio in the design process of the accelerator.(2) Influence of the encapsulating material selection on the dynamic characteristicsduring the second package process of sensor chip.The accelerometer with encapsulation could be equivalent to the two degree of freedomsystem of the chip level sensor and the encapsulating material. The influence of thecharacteristic parameters of the encapsulating material on the dynamic characteristics of theaccelerometer was studied and the foundation in selecting the appropriate encapsulating material was put forward, which meant that the encapsulation with relatively high elasticmodulus, damping ratio and stiffness coefficient would have a better performance. Thesimulation model was verified through dynamic characteristics experiments of accelerometerswith varied encapsulating material, and both of them provided guidance in the secondpackage process for accelerometers. The experiment results also showed that epoxy resin,whose elastic modulus were more than2GPa, was quite appropriate for the secondencapsulation of the high-g piezoresistive accelerometer.The influence of the damping factor and encapsulating material on the dynamiccharacteristics of high-g piezoresitive accelerometer during the first and second packageprocess was mainly studied by theoretical analysis, computer simulation and experimenttesting. The results provided theoretical guidance and technical support for the accelerometerdesign and application.