Removal of the rate table:MEMS gyrocompass with virtual maytagging

High-performance micro-electro-mechanical system(MEMS)gyrocompasses for north-finding systems have been very popular for decades.In this paper,a MEMS north-finding system(NFS)based on virtual maytagging(VM)is presented for the first time.In stark contrast to previous schemes of MEMS-based NFSs(e.g.,carouseling,maytagging)and the abandoning rate table,we developed a honeycomb disk resonator gyroscope(HDRG)and two commercial accelerometers for azimuth detection.Instead of the physical rotation of the integrated turntable in traditional NFSs,the vibratory working modes of the HDRG are rotated periodically with electronic control to reduce the uncertainty in the azimuth.After systematically analyzing the principle of NFSs with VM,we designed tests to verify the practicability at the sensor level.A bias instability of 0.0078°/h can be obtained during one day with VM in an HDRG.We also implemented comparative north-finding experiments to further check our strategy at the system level.The accuracy in the azimuth can reach 0.204°for 5 min at 28.2°latitude with VM and 0.172°with maytagging.The results show that without any mechanical turning parts,VM technology makes it possible to develop high-precision handheld MEMS NFSs.

0.04 degree-per-hour MEMS disk resonator gyroscope with high-quality factor (510 k) and long decaying time constant(74.9 s)

The disk resonator gyroscope is an attractive candidate for high-performance MEMS gyroscopes.This gyroscope consists of a sensor and readout electronics,and the characteristics of the sensor directly determine the performance.For the sensor,a high-quality factor and long decaying time constant are the most important characteristics required to achieve high performance.We report a disk resonator gyroscope with a measured quality factor of 510 k and decaying time constant of 74.9 s,which is a record for MEMS silicon disk resonator gyroscopes,to the best of our knowledge.To improve the quality factor of the DRG,the quality factor improvement mechanism is first analyzed,and based on this mechanism two stiffness-mass decoupled methods,i.e.,spoke length distribution optimization and lumped mass configuration design,are proposed and demonstrated.A disk resonator gyroscope prototype is fabricated based on these design strategies,and the sensor itself shows an angle random walk as low as 0.001°/√h,demonstrating true potential to achieve navigation-grade performance.The gyroscope with readout electronics shows an angle random walk of 0.01°/√h and a bias instability of 0.04°/h at room temperature without compensation,revealing that the performance of the gyroscope is severely limited by the readout electronics,which should be further improved.We expect that the quality factor improvement methods can be used in the design of other MEMS gyroscopes and that the newly designed DRG can be further improved to achieve navigation-grade performances for high-end industrial,transportation,aerospace,and automotive applications.

0.79 ppm scale-factor nonlinearity whole-angle microshell gyroscope realized by real-time calibration of capacitive displacement detection

Whole-angle gyroscopes have broad prospects for development with inherent advantages of excellent scale factor,wide bandwidth and measurement range,which are restrictions on rate gyroscopes.Previous studies on the whole-angle mode are based mostly on the linear model of Lynch,and the essential nonlinearity of capacitive displacement detection is always neglected,which has significant negative effects on the performance.In this paper,a novel realtime calibration method of capacitive displacement detection is proposed to eliminate these nonlinear effects.This novel method innovatively takes advantage of the relationship between the first and third harmonic components of detective signals for calibration.Based on this method,the real-time calibration of capacitive displacement detection is achieved and solves the problems of traditional methods,which are usually related to the vibration amplitude,environmental variations and other factors.Furthermore,this novel calibration method is embedded into a whole-angle control system to restore the linear capacitive response in real time and then combined with a microshell resonator for the first time to exploit the enormous potential of an ultrahigh Q factor and symmetric structure.The effectiveness is proven because the angle drift is reduced significantly to improve the scale-factor nonlinearity by 14 times to 0.79 ppm with 0.0673/h bias instability and a 0.0017s rate threshold,which is the best reported performance of the MEMS whole-angle gyroscope thus far.More importantly,this novel calibration method can be applied for all kinds of resonators with the requirement of a linear capacitive response even under a large resonant amplitude.