Research Of Tuning Fork Type Micromachined Gyroscope Based On Slide-Film Damping

Micromachined gyroscopes have a variety of applications in many fields due to their small size, light weight and low cost. Many effort 5 have been spent in improving the sensitivity in past years, In this dissertation, a novel micromachined vibratory gyroscope, based on slide-film damping principle, is investigated, including the operating principle, design and fabrication, packaging and measurement of the device.By means of analyzing the fundamentals and dynamic characteristics of micromachined vibratory gyroscopes, the influence of the operating frequencies, Q-values and driving force on the sensitivity and bandwidth of the device has been discussed. The air damping, quadrature error, parasite Coriolis force and interference from axial accelerations are also discussed.On the basis of theoretic analysis and previous works, we proposed a novel design for the micromachined gyroscope, in which electromagnetic driving is used, and the air damping in driving and sensing vibration mode is mainly slide-film damping. The former helps to obtain large driving force with constant ampl :tude, and the latter makes it possible to achieve high Q-values at atmospheric pressure. The mechanical coupling in the device is constrained significantly by using the decoupled design, and the tuning fork type design suppresses the interference from axial accelerations.System consideration, including the mechanical behavior, capacitive sensing, electronics, and noise sources of the device, were discussed. The natural frequencies and Q-values at atmospheric pressure are 2800Hz and 1613 for driving mode, and 3000Hz and 1613 for sensing mode, respectively. The expected noise equivalent rate is 0.123.The device was fabricated using silicon bulk mioromachining processes. The rootingeffect and marginal distortion of the structure in Deep Reactive Ionic Etching (DRIE) process were investigated.An equivalent circuit model of the device was built and used to simulate the behavior of the device, which is in good accordance with the analytic result. The interface circuit for the device was designed, tested, and applied to measure the device.At atmospheric pressure, the device is packaged and the performance was tested. The measured resonant frequencies and Q-values are 2906Hz and 1004 for driving mode, and 2996Hz and 522, 3033Hz and 421 for both sensing proof masses vibration modes, respectively. The sensor obtained a scale factor of 9.8mV/s, and a non-linearity of 0.43%. The noise equivalent angular rate and Zero Rate Output (ZRO) are and 144?h, respectively.The analyzed and measured results show that the device designed in this dissertation has achieved high Q-values and sensitivity at atmospheric pressure, low mechanical coupling and thermal noise, with the interference from axial accelerations suppressed effectively. The device has shown its potential in some practical applications.