Unlike traditional rotational gyroscopes,microelectromechanical systems(MEMS)gyroscopes use a vibrating proof mass rather than a rotational mass to sense changes in angular rate. They are also smaller and less expensive than traditional gyroscopes.MEMSgyroscopes are known to be susceptible to the effects of acoustic noise, in particular high frequency and high power acoustic noise. Most notably, this has been proven true in aerospace applications where the noise can reach levels in excess of 120 dB and the noise frequency can exceed 20 kHz. The typical resonant frequency for the proof mass of a MEMSgyroscope is between 3 and 20 kHz. High power, high frequency acoustic noise can disrupt the output signal of the gyroscope to the point that the output becomes unreliable. In recent years, considerable research has focused on the fascinating properties found in metamaterials. A metamaterial is an artificially fabricateddevice or structure that is engineered to produce desired material responses that can either mimic known behaviors or produce responses that do not occur naturally in materials found in nature. Acoustic metamaterials, in particular, have shown great promise in the field of sound attenuation. This paper proposes a method to mitigate the performance degradation of the MEMSgyroscope in the presence of high power, high frequency acoustic noise by using a new acoustic metamaterial in the form of a two-dimensional array of micromachined Helmholtz resonators. The Helmholtz resonators are fabricated in a silicon wafer using standard MEMS manufacturing techniques and are designed to attenuate sound at the resonant frequency of the gyroscope proof mass. The resonator arrays were diced from the silicon wafer in one inch squares and assembled into a box open on one end in a manner to attenuate sound on all sides of the gyroscope, and to seal the gyroscope inside the box. The resulting acoustic metamaterialdevice was evaluated in an acoustic chamber and was found to successfully attenuate sound as much as 18 dB. This attenuation is in the form of a notch filter at and around 14.5 kHz, which was the target frequency of attenuation. The notch filter attenuation occurred over a 700 Hz frequency band with 18 dB being the largest attenuation in the band.
Gyroscopes; Turn-sensitive devices with vibrating masses; Turn-sensit...
William N. Yunker,
Colin B. Stevens,
George T. Flowers and
Robert N. Dean
Source:J. Appl. Phys. 113, 024906 (
1.M. Gad-el-Hak, MEMS Handbook (CRC, 2001).
2.C. Acar and A. Shkel, MEMS Vibratory Gyroscopes Structural Approaches to Improve Robustness (Springer, 2009).
3.R. Dean, G. Flowers, N. Sanders, R. Horvath, M. Kranz, and M. Whitley, “ Micromachined vibration isolation filters to enhance packaging for mechanically harsh environments,” J. Microelectron. Electron. Packag.2(4 ), 223–231 (2005).
4.T. G. Brown, “ Harsh military environments and microelectromechanical (MEMS) devices,” Proc. IEEE Sens.2, 753–760 (2003).
5.M. S. Weinberg and A. Kourepenis, “ Error sources in in-plane silicon tuning-fork MEMS gyroscopes,” Microelectromech. Syst.15(3 ), 479–491 (2006).
6.R. N. Dean, G. T. Flowers, A. S. Hodel, G. Roth, S. Castro, R. Zhou, A. Moreira, A. Ahmed, R. Rifki, B. E. Grantham, D. Bittle, and J. Brunsch, “ On the degradation of MEMS gyroscope performance in the presence of high power acoustic noise,” IEEE Int. Symp. Ind. Electron.1435–1440 (2007).
7.S. Zhang, Acoustic Metamaterial Design and Applications (University of Illinois at Urbana-Champaign, 2010).
8.J. Li and C. T. Chan, “ Double-negative acoustic metamaterial,” Am. Phys. Soc. Phys. Rev. E70(5 ), 055602 (2004).
17.R. N. Dean, S. Castro, G. T. Flowers, G. Roth, A. Ahmed, A. S. Hodel, B. E. Grantham, D. Bittle, and J. Brunsch, “ A characterization of the performance of MEMS gyroscopes in acoustically harsh environments,” IEEE Trans. Ind. Electron.58(7 ), 2591–2596 (2011).