An integrated packaged resonant accelerometer with temperature compensation

Abstract

This paper describes the design, fabrication, and testing of an integrated packaged sensor that is composed of a micro resonant accelerometer and a temperature sensor. The resonant accelerometer with differential configuration consists of double quartz resonators and a silicon substrate. When acceleration is applied along the sensing axis, the inertial force induced by the proof mass will transfer force to the resonators, which causes an opposite frequency shift of the dual quartz resonators. The loaded acceleration can be measured through detecting the differential frequency shift. The symmetric differential configuration response to spurious effects of thermal loading and inelastic effect causing prestress in the resonators is similar, which can be reduced by detecting the differential frequency, effectively. However, during the manufacture and packaging process, the otherness of residual stress in two quartz resonators results in that the response of resonators to temperature variation is not strictly the same. In other words, this temperature drift cannot be eliminated by the structure design. Thus, a temperature sensor and an accelerometer were packaged in a shell together. These novel integrated sensors can measure acceleration and temperature simultaneously. With the testing temperature data, a novel temperature compensation that is a combination of the variable coefficient regression and least squares support vector machine is used for improving the performance of the accelerometer. By means of this compensation and field programmable gate array, a real-time and online compensation is achieved. The tumble testing results indicate that the sensitivity of the accelerometer is ∼16.97 Hz/g. With the temperature compensation, the output drift of the scale factor is improved by 0.605 Hz/g in the full temperature range, which is from 0.072 Hz/g to 0.015 Hz/g. The drift of zero bias is improved from 345 mg to 1.9 mg.

Temperature compensation of MEMS resonant accelerometers with an on-chip platinum film thermometer

“…To further reduce the temperature drift effect in practice, two commonly used approaches are constant temperature control of the sensor or modeling and real-time compensation of the drift [18][19][20][21]. Draper Laboratory reported a high-precision MRA prototype with excellent stability required for strategic navigation systems, which demonstrated a bias stability of 0.19 µg and 2 µg for 3-day and 30-day measurements under 0.01 • C precise temperature control [22].…”

A Novel Self-Temperature Compensation Method for Mode-Localized Accelerometers

“…Furthermore, as the Young’s modulus of the silicon material is very sensitive to temperature, mechanical coupling stiffness is temperature-dependent, making the temperature performance worse. To improve the temperature performance of MEMS accelerometers, some methods were proposed including active temperature control [ 20 , 21 , 22 , 23 ], temperature compensation [ 24 , 25 , 26 ] and less temperature sensitivity structure [ 27 ]. The active temperature control scheme requires complex temperature control systems and higher power consumption.…”

An Improved Difference Temperature Compensation Method for MEMS Resonant Accelerometers

“…Salvia presented a real time temperature compensation for MEMS oscillators using an integrated oven, achieving a frequency stability of ±1 ppm from −20 • C to +80 • C. Yang adopted a micro oven-control system to keep temperature in inertial sensors, providing the temperature-induced root of sum of squares bias error 1.920 mg from −40 • C Micromachines 2021, 12, 1022 2 of 11 to 85 • C for three-axis accelerometers in their Invensense MPU-6050. Another way is to remove the side effects caused by temperature change with thermal compensation [22][23][24]. In [22], an integrated temperature sensor is set to sense the temperature and the compensation algorithm is implemented in FPGA.…”

“…Another way is to remove the side effects caused by temperature change with thermal compensation [22][23][24]. In [22], an integrated temperature sensor is set to sense the temperature and the compensation algorithm is implemented in FPGA. The zero bias is reduced from 345 mg to 1.9 mg over the temperature range from −10 • C to 80 • C. The work presented in [23] uses an additional resonator to sense the temperature and the result is used to make temperature compensation.…”