A low-noise three-axis piezoelectric MEMS accelerometer for condition monitoring

Prognostics and health management (PHM) is a crucial measure to minimize the financial loss caused by downtime and damage in smart factories. To prevent the failures of industrial machines, a low-noise three-axis piezoelectric accelerometer in small scale is proposed to measure the vibration parameters for PHM application. It consists of a middle tungsten proof mass and 4 composite beams, which includes PZT and stainless steel layers. Simulation validates the principle of 3-axis measurement and gives the sensitivities of 0.714 mV/g, 0.714 mV/g and 1.72 mV/g for x-, y- and zaxis sensing. Calculated mechanical-thermal noise is 0.4 μg/√Hz, much lower than the typical noise of a commercial capacitive MEMS accelerometer. The designed sensor is fabricated with a metal-MEMS process and aerosol deposition method with the resonant frequency around 4.11 kHz. The testing results of x- and y-axis sensitivities, 0.5541 mV/g and 0.5420 mV/g, show the effectiveness of dual-axis measurement. In the end, the study analyzes hypotheses for the coupling of 3-axis measurement and proposes the improvement direction in further study.