This paper researches on the temperature effects of a fully-symmetrical micromachined gyroscope. The Young’s modulus and thermal expansion coefficient of silicon vary with the environment temperature, which affects the modes’ resonant frequencies of micromachined gyroscopes. The effects of temperature fluctuation on the modes’ resonant frequencies is simulated by the FEM software ANSYS. The simulation results show that the fully-symmetrical gyroscope’s resonance frequencies decrease with the increase of temperature and the decrease degree nearly 0.256Hz/°C, but the two modes’ resonance frequencies matches well. The micromachined gyroscope’s dynamic characteristics are tested. The resonant frequencies and the quality factor are reduced with the increase of temperature and the decrease degree of the fit linear about the resonant frequencies is 0.276 Hz/°C. The test results are in good accordance with the simulation results.
The resonance phenomenon is suppressed by adjusting the damping of the comb
accelerometer structure to widen the frequency bandwidth of the capacitive accelerometer. The
capacitive accelerometer with asymmetrical combs, fabricated with DRIE and anodic bonding, is
presented. The damping category of the accelerometer is introduced, in which the squeeze-film
damping coefficient and the damping ratio factor are detailed. The damping ratio factor of the
accelerometer, measured by a vibration method, is 0.17. The damping ratio factor of the optimized
structure is calculated of 0.15 to 0.18 with the change of experiential modulus C from 25 to 30,
theoretically.
Structure’s strain reflects the stability of the project, the excessive structural strain will destroy the stability of the structure. Fiber Bragg Grating has many features, such as, strong anti-interference ability, low optical loss, and it can be used for a long time in the project, etc. Base on the features, the Fiber Bragg Grating Strain Sensor can be used in slope and other projects for the long-term monitoring. In this paper, we develop a Fiber Bragg Grating Strain Sensor based on the spring-steel pipe, FBG be fixed to the inner of the steel pipe by epoxy glue, it is protected by a stainless steel pipe outside, the Flange be fixed to the both side of the spring-steel pipe. When the tension acting one the flanges, the spring-steel pipe occurs an axial strain, this axial strain makes the center wavelength of the Fiber Bragg Grating change, measuring the wavelength shift amount of the Fiber Bragg Grating can calculate the strain. The loading experiment indicates that the sensitivity of the Spring-steel pipe Fiber Bragg Grating Strain Sensor is 0.81pm/με, the linearity of the sensor is 2.1%FS, and the repeatability error of the sensor is 2.29%FS.
During the period of tunnel excavation, shoring, forming and long-term operation, stress changes of tunnel surrounding rock are complex, the real-time monitoring of surrounding rock pressure is the key factor in ensuring long-term stability in tunnel. Fiber Bragg grating earth pressure sensors apply in surrounding rock pressure of tunnel which can change the pressure of the surrounding rock into fiber Bragg grating wavelength shift. According to the feature of pressure and temperature in Tian Xin Tunnel, 40 earth pressure sensors are embedded in 20 representative sections and one earth pressure sensor is embedded in each arch shoulder. In addition, one temperature compensation sensor is embedded in each arch crown. During the 235 monitoring days, the biggest daily change of surrounding rock pressure reaches 800 KPa. In 3 months of the sensor installation, the average monthly variation is within 50 KPa. The long-term measurement results indicate that the changes of surrounding rock pressure are different in different locations. When the surrounding rock is close to the excavated and blasted surface the surrounding rock pressure changes largely.
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