READOUT METHOD AND ELECTRONIC BANDWIDTH CONTROL FOR A SILICON IN-PLANE TUNING FORK GYROSCOPE

• US 20120192647A1
• Filed: 05/19/2011
• Published: 08/02/2012
• Est. Priority Date: 07/13/2007
• Status: Active Grant

• Current Assignee: Ajit Sharma, Farrokh Ayazi, Mohammad F. Zaman
• Original Assignee: Ajit Sharma, Farrokh Ayazi, Mohammad F. Zaman
• Inventors: Ayazi, Farrokh, Sharma, Ajit, Zaman, Mohammad Faisal
• Granted Patent: US 8,677,821 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

Disclosed are methods and a sensor architecture that utilizes the residual quadrature error in a gyroscope to achieve and maintain perfect mode-matching, i.e., ˜0 Hz split between the drive and sense mode frequencies, and to electronically control sensor bandwidth. In a reduced-to-practice embodiment, a 6 mW, 3V CMOS ASIC and control algorithm are interfaced to a mode-matched MEMS tuning fork gyroscope to implement an angular rate sensor with bias drift as low as 0.15°/hr and angle random walk of 0.003°/√hr, which is the lowest recorded to date for a silicon MEMS gyroscope. The system bandwidth can be configured between 0.1 Hz and 1 kHz.

Claims

1-8. -8. (canceled)

9. A mode matching method for use with a microelectromechanical systems gyroscope, comprising:

determining a current zero rate output level of the gyroscope;

storing the current zero rate output level;

determining if the current zero rate output level is greater than or equal to a previous zero rate output level;

if the current zero rate output level is less than the previous zero rate output level, incrementing a counter, increasing polarization voltage applied to the gyroscope, and determining the zero rate output level of the gyroscope;

if the current zero rate output level is greater than or equal to the previous zero rate output level, decreasing the polarization voltage applied to the gyroscope, and verifying the phase difference (.DELTA.phi.) between drive and sense signals applied to and derived from the gyroscope;

iteratively incrementing the polarization voltage until a maximum in residual zero rate output amplitude level is detected;

monitoring the 90.degree. phase difference to ensure that mode-matching is achieved; and

once mode matching is achieved, controlling the bandwidth of the sensor by varying the polarization voltage to introduce a controlled frequency separation between drive and sense resonant modes of the gyroscope.

10-15. -15. (canceled)