Page 287 - Mechanical design of microresonators _ modeling and applications

0-07-145538-8_CH05_286_08/30/05

Resonant Micromechanical Systems

286 Chapter Five
flexure hinge

resonant beam
seismic mass

anchor

Figure 5.61 Resonant beam microaccelerometer with side supporting flexure hinges.

Another solution for sensing an external acceleration through
bending-generated modification of the relevant resonant frequency is
sketched in Fig. 5.61 and was utilized by Burrer, Esteve, and Lora-
28
29
Tamayo and Roszhart et al., for instance. The beam microresonator
is located in the center and is flanked by two side flexure hinges
supporting the seismic mass, which will move under the action of an
external acceleration. This action will produce bending of the central
beam, which will alter its resonant frequency.
30
Tudor et al. propose utilizing a double-ended tuning fork instead of
the simple beam resonator in Fig. 5.61. The particular solution with a
double-ended tuning fork presents the advantage that the externally
applied acceleration can be monitored by means of Coriolis effects (as
shown in the previous section of this chapter) in addition to the normal
change in the resonator’s resonant frequency.
31
Huang et al. proposed utilizing one single supporting flexure hinge
and two side beam resonators, as sketched in Fig. 5.62. This specific
design could be tailored to sense external acceleration which is applied
either in plane (case where the seismic mass will move laterally) or out
of the plane.
32
A similar design was mentioned by Esashi and is sketched in
Fig. 5.63. The seismic mass this time is supported by two side torsion
hinges, whereas the beam resonator remains in a central position. Its
clamping point to the seismic mass goes up or down out of the plane of
the structure, and therefore the beam resonator bends upward or
downward, which modifies the resonant frequency.
33
Burns et al. microfabricated and tested a resonant microbeam
accelerometer for sensing out-of-the-plane acceleration. Figure 5.64
sketches the top view of the accelerometer which comprises four
resonant beams and has a seismic mass supported by flexure pairs at
its corners.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.