Optical detection of the Coriolis force on a silicon micromachined gyroscope

In this paper, we report on the optical characterization of a micromachined gyroscope prototype for automotive applications, by means of feedback interferometry. In order to directly detect the rotation-induced Coriolis force, we have developed a compact and stable interferometric setup, which has been positioned inside a small vacuum bell, mounted on a rotating table. By this setup, which has a noise limit of the order of 10/sup -11/ m/(Hz)/sup 1/2/, we have measured the gyro responsivity curve, demonstrating the feasibility of the optical interferometric detection of the in-plane response of a MEMS sensor. In addition, we have carried out the full mechanical characterization of the device at different pressures, and we have performed the matching of the gyro resonance frequencies by the interferometric monitoring. Our gyro had a resonance frequency of 3986 Hz for both axes after tuning; at a pressure of 7 10/sup -2/ torr, the quality factor were Q=18000 for the driving axis and Q=1800 for the sensing axis, while the measured responsivity was 7 10/sup -10/ m/(/spl deg//s). The optical characterization represents an important feedback to the designer and is especially powerful in the case of prototypes for which the on-board electronics is not yet available.

[1]  David Wood,et al.  A system for the dynamic characterization of microstructures , 1997 .

[2]  Sabina Merlo,et al.  Comparison of capacitive and feedback-interferometric measurements on MEMS , 2001 .

[3]  V. Vorperian,et al.  A packaged silicon MEMS vibratory gyroscope for microspacecraft , 1997, Proceedings IEEE The Tenth Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots.

[4]  J. Bernstein,et al.  A micromachined comb-drive tuning fork rate gyroscope , 1993, [1993] Proceedings IEEE Micro Electro Mechanical Systems.

[5]  Fred M. Dickey,et al.  Optical measurement of micromachine engine performance , 1997, Photonics West - Micro and Nano Fabricated Electromechanical and Optical Components.

[6]  G. Giuliani,et al.  Laser diode feedback interferometer for measurement of displacements without ambiguity , 1995 .

[7]  M. W. Putty.  A Maicromachined vibrating ring gyroscope , 1994 .

[8]  K. Najafi,et al.  A HARPSS polysilicon vibrating ring gyroscope , 2001 .

[9]  Bernard Courtois,et al.  Design, Test, Integration, and packaging of MEMS/MOEMS, Paris, France, 2000 , 2000 .

[10]  Sabina Merlo,et al.  Measurements on a micromachined silicon gyroscope by feedback interferometry , 2001 .

[11]  Silvano Donati,et al.  Hybrid opto-mechanical gyroscope with injection-interferometer readout , 2001 .

[12]  Håkan Pettersson,et al.  A NOVEL SILICON BULK GYROSCOPE , 1999 .

[13]  F. Maseeh,et al.  Accurate fully-coupled natural frequency shift of MEMS actuators due to voltage bias and other external forces , 1999, Technical Digest. IEEE International MEMS 99 Conference. Twelfth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.99CH36291).

[14]  Y. Mochida,et al.  A micromachined vibrating gyroscope , 1995 .

[15]  Farrokh Ayazi,et al.  Micromachined inertial sensors , 1998, Proc. IEEE.

[16]  William C. Tang,et al.  Laterally driven polysilicon resonant microstructures , 1989, IEEE Micro Electro Mechanical Systems, , Proceedings, 'An Investigation of Micro Structures, Sensors, Actuators, Machines and Robots'.

[17]  Y. Mochida,et al.  A micromachined vibrating rate gyroscope with independent beams for the drive and detection modes , 2000, Technical Digest. IEEE International MEMS 99 Conference. Twelfth IEEE International Conference on Micro Electro Mechanical Systems (Cat. No.99CH36291).

[18]  Sabina Merlo,et al.  Mechanical–thermal noise in micromachined gyros , 1999 .

[19]  Fred M. Dickey,et al.  Optical methods for micromachine monitoring and feedback , 1999 .

[20]  Eran Socher,et al.  A novel micromachined vibrating rate-gyroscope with optical sensing and electrostatic actuation , 2000 .