Mitigation of the Effects of High Levels of High-Frequency Noise on MEMS Gyroscopes
Type of Degreedissertation
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MEMS gyroscopes are being used in a variety of applications such as camcorders, vehicle stability control and game controllers. Sometimes they are used in harsh environments such as high levels of high-frequency noise. If the frequency of the noise coincides with the natural frequency of the gyroscope, the output of the latter is corrupted. Experiments have been performed to demonstrate the effects of noise on MEMS gyroscopes. The objective of this dissertation is to suggest ways to mitigate those effects. In the first part of this research work, a mathematical model has been developed to include the effects of an external noise signal on a MEMS gyroscope. The model is simulated to assist with understanding its dynamics and it is found that the effects of the external noise signal are superimposed on the normal gyroscope’s output. This finding leads to the solution of using a non-driven gyroscope to measure the superimposed effects. Thus, a differential-measurement system consisting of two gyroscopes is implemented, and simulation of the mathematical model is performed to successfully demonstrate the mitigation of the effects of noise. Experiments were performed on five gyroscopes to confirm the simulation results, and the superposition of the effects of noise has been confirmed implying that the differential measurement is a viable solution. The second part of this research provides a study of passive approaches to attenuate the effects of noise. In this regard, four types of nickel microfibrous material were made using three diameters of nickel fibers and a wet-lay papermaking process. The Delany-Bazley analytical acoustical model was used to determine the optimum acoustical properties of the material. The properties were then used to calculate the absorption coefficients of the microfibrous media. Damping characterization of the media was performed using the vibration transmissibility concept. Enclosures have been designed and made from the materials to attenuate the effects of noise on MEMS gyroscopes. Acoustical tests performed in a reverberation room show up to 90% reduction in the amplitude of the effects of noise. In conclusion, two different approaches have been suggested to mitigate the undesirable effects of noise on MEMS gyroscopes. In the first approach an active design is proposed by utilizing a pair of gyroscopes whose outputs can be manipulated to yield the desired uncorrupted results. In the second approach, a passive design is proposed using nickel microfibrous material as an acoustical enclosure. Considerable reductions in the effects of noise have been achieved, showing that the nickel microfibrous material can be used to construct an acoustical enclosure.