2021 Fiscal Year Annual Research Report
Novel mode-matched MEMS gyroscope with high capacity to tune frequency and Q-factor
| Project/Area Number |
21J11628
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| Research Institution | Tohoku University |
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Principal Investigator |
陳 建霖 東北大学, 工学研究科, 特別研究員(DC2)
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| Project Period (FY) |
2021-04-28 – 2023-03-31
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| Keywords | Triple mass resonator / Anchor loss tuning / Squeeze film damping / Frequency tuning / Mode matched resonator / Rate integrating gyro |
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| Outline of Annual Research Achievements |
In this year, I investigated the frequency and Q-factor tuning ability of the proposed structure, which were presented in three international conferences (IEEE INERTIAL 2021, IEEE SENSORS 2021, IEEE MEMS 2022) and published in one journal paper (2-3 journal papers were prepared to publish). Two kinds of tuning fork resonators integrating novel structure were designed and fabricated. The devices worked properly and the experimental results matched well with the simulation results and theoretical models. The high tuning capacity was proved in the proposed structure, which is helpful for high performance gyroscope requiring highly symmetric structure. Additionally, the application of the proposed structure in highly sensitive accelerometer was also studied.
Purposes of this research are to investigate mechanisms of Q-factor and frequency tuning and achieve highly symmetry in proposed gyroscope structure. Then, the mode-matching resonator can be applied in rate integrating gyroscope (RIG) control system to achieve high performance MEMS gyroscopes. RIG gyroscopes are key technologies to improve MEMS gyroscopes’ stability for navigation purpose. These technologies can foster autonomous cars and robots to be available in the market soon because these ideas can make autonomous application safer, more intelligent and cheaper.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
In this year, I mainly worked on the device design, fabrication and measurement of the novel triple mass resonator (TMR) design. Q-factor and frequency tuning of the TMR were validated theoretically and experimentally. Two type of tuning mechanisms were proposed and proved. The mode-matched device was applied in the rate integrating gyroscope control system and can successfully detect inertial rotation.
For the Q-factor tuning related to anchor loss tuning, the fabricated device can tune Q-factor by 19% largely, while mirror effect on resonant frequency as small as 162 ppm. This showed the proposed structure can independently tune Q-factor from frequency, which is important for highly matched gyroscopes sensors.
Besides, the Z-axis gyroscope resonator was designed and fabricated. The independently Q-factor tuning was also validated in low vacuum environment. The mode-matching was achieved by electrostatic tuning and the Q-factor matching was also achieved by tuning the squeeze file damping. Finally the resonator with frequency mismatch under 10 ppm and Q-factor mismatch under 650 ppm was achieved by DC bias tuning.
Finally, the mode-matched resonator was applied in the rate integrating gyroscope control system. Two degenerated modes were successfully controlled by the FPGA board and the phase difference between two modes was changed under the inertial rotation applied on the device.
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| Strategy for Future Research Activity |
Now we already fabricated the design gyroscope devices and the tuning mechanism was proved in the proposed structure. In the next stage, we can measure the device in the vacuum chamber and implement the device on the servo rotation table. On the other hand, we can try to proceed the vacuum package process on the fabricated device and we can measure the device on the normal rotation table.
Firstly we will try to measure the device in the vacuum chamber and the inertial rotation will be generated by a servo motor. The device will applied in the rate integrating gyroscope control system. We need to use different tuning methods to decrease the stiffness and damping mismatch along X-Y axes, including adjusting the actuating voltage ratio and phase difference and using electrostatic tuning method. The performance of gyroscope will be measured and investigated including resolution, sensitivity and nonlinear error.
Secondly, we need to investigate the electrostatic tuning effect on the stability of the gyroscope. Under the inertial rotation, unexpected acceleration will generate and cause the change of capacitive gap and electrostatic soften stiffness. Therefore, the external acceleration will disturb the electrostatic tuning and cause detrimental effect on the stability of the gyroscope performance.
Based on the measurement results, the device structure can be further improved to prevent the acceleration noise.
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