| Aiming at the problem of space acceleration monitoring of objects,this paper presents a piezoresistive three-axis acceleration sensor based on MEMS technology.The three-axis acceleration sensor chip is composed of a C-type silicon cup,four L-type double beams,middle double beams and two mass blocks.The sensing unit of the three-axis acceleration sensor is twelve piezoresistors distributed on the four L-shaped double beams and the middle double beams,respectively.The twelve piezoresistors are connected to form Wheatstone bridge circuit in the direction of x-axis,y-axis and z-axis.Under the action of external acceleration,the four L-shaped double beams and the middle double beams have elastic deformation,resulting in stress concentration on the chip.So the resistance value of the piezoresistors changed,and the output voltages of the Wheatstone bridge composed of piezoresistors changed,which can realize the acceleration measurement in x-axis,y-axis and z-axis.On this basis,Ansys finite element simulation software and Comsol software has been used to simulated the characteristics of acceleration sensor chip,the mechanical and electrical characteristics of chip has been analyzed.The influence of the sensor chip's size on the resonance frequency and sensitivity of the three-axis acceleration sensor was studied,by changing the structure size to improve the consistency of the three-axis measuring sensitivity.Based on MEMS technology,the three-axis accelerometer chip was fabricated on SOI wafer,and the chip was packaged completed by ultrasonic pressure welding of gold wire.Standard vibration table and other testing instruments were used to test the characteristics of the encapsulated three-axis acceleration sensor.The results show that at room temperature,when the input voltage is 5.0 V,the sensitivity of the chip size with the highest consistency is 0.302 mV/g,0.235 mV/g and 0.347 mV/g,respectively,and the minimum cross interference value is 0.001 mV/g. |
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