A simple analytical design approach based on computer aided analysis of bulk micromachined piezoresistive MEMS accelerometer for concrete SHM applications

Abstract

Structural Health Monitoring (SHM) using non destructive testing generally involves measurement of shift in natural frequency of the monitored structure. This paper presents the simulation using CoventorWare MEMS design tool and analysis of three bulk micromachined piezoresistive MEMS accelerometers namely device A, B and C that are specifically intended for SHM applications. The devices A and B have been designed for the same natural frequency (100Hz) but with different geometries. The device C has the maximum deflection sensitivity. The modal, piezoresistive and stress analyses show that beam length (L) must be less than the half side length (a) of the proof mass for achieving maximum voltage sensitivity. Thus Device-A has been selected for further analysis and the various performance factors for the Device-A have been obtained using simulation experiments and the results show that this device has excellent voltage sensitivity (3.56mV/g/V), appreciably smaller cross axes sensitivities (32.8μV/g/V), very low noise floor (4.53μg/Hz) and high resolution (12.72μg) compared with the already reported piezoresistive accelerometer designed for SHM applications and certain general purpose accelerometers available in the global market. The frequency analysis on two devices (Devices A and D) show that the resonant frequency of the sensor should be low for achieving maximum sensitivity and the damping factor (ξ) must be 0.7 for getting the maximum bandwidth over which the sensitivity remains constant (60Hz). Finally, a standard analytical design procedure for the design of piezoresistive MEMS accelerometers has been developed and presented based on the various observations and results of this study. Further, the design approach for high packing density has also evolved.