Micromachined piezoelectric X-Axis gyroscope
This disclosure provides systems, methods and apparatus, including computer programs encoded on computer storage media, for making and using gyroscopes. Such gyroscopes may include a sense frame, a proof mass disposed outside the sense frame, a pair of anchors and a plurality of drive beams. The plurality of drive beams may be disposed on opposing sides of the sense frame and between the pair of anchors. The drive beams may connect the sense frame to the proof mass. The drive beams may be configured to cause torsional oscillations of the proof mass substantially in a first plane of the drive beams. The sense frame may be substantially decoupled from the drive motions of the proof mass. Such devices may be included in a mobile device, such as a mobile display device.
1. A gyroscope, comprising:
a sense frame;
a proof mass disposed outside the sense frame;
a pair of anchors;
a plurality of drive beams disposed on opposing sides of the sense frame and between the pair of anchors, the drive beams connecting the sense frame to the proof mass, each of the drive beams including a piezoelectric layer and configured to cause drive motions of the proof mass, the drive motions being torsional oscillations substantially in a first plane of the drive beams; and
a plurality of sense beams connecting the sense frame to the pair of anchors, each of the sense beams including a layer of piezoelectric sense electrodes configured to produce a piezoelectric charge in response to an angular rotation applied to the gyroscope,
wherein the sense frame is substantially decoupled from the drive motions of the proof mass.
2. The gyroscope of claim 1 , wherein the proof mass and the sense frame oscillate together torsionally out of the first plane, in response to the applied angular rotation, when the gyroscope is operating in a sense mode.
3. The gyroscope of claim 1 , wherein the sense beams are tapered sense beams.
4. The gyroscope of claim 1 , further including linkage beams configured to increase a transfer of a proof mass sense motion to the sense frame when the gyroscope is operating in a sense mode.
5. The gyroscope of claim 1 , wherein the sense beams are separated from the proof mass by a gap that extends around most of the sense frame.
6. The gyroscope of claim 1 , wherein each of the sense beams has a first end connected to an anchor and a second end connected to a portion of the sense frame.
7. The gyroscope of claim 1 , wherein the sense frame includes tapering portions that are wider at a first end near an anchor and narrower at a second end away from the anchor.
8. The gyroscope of claim 1 , wherein a first anchor of the pair of anchors is separated from the sense frame by a first gap and wherein a second anchor of the pair of anchors is separated from the sense frame by a second gap.
9. The gyroscope of claim 1 , wherein the drive beams are attached to the sense frame at a central portion of the sense frame disposed between the pair of anchors.
10. The gyroscope of claim 1 , wherein the drive beams are compliant to in-plane stresses applied in the first plane but stiff to out-of-plane stresses.
11. The gyroscope of claim 1 , wherein at least one of the proof mass and the sense frame are formed, at least in part, from plated metal.
12. The gyroscope of claim 1 , wherein the drive beams are configured to generate drive oscillations via a differential piezoelectric drive.
13. The gyroscope of claim 2 , wherein the pair of anchors defines a first axis through a central portion of the gyroscope and wherein the proof mass and the sense frame oscillate around the first axis when the gyroscope is operating in a sense mode.
14. The gyroscope of claim 3 , wherein bending stresses along the tapered sense beams are substantially uniform with increasing distance from the anchors when the gyroscope is in a sense mode.
15. The gyroscope of claim 4 , wherein the linkage beams are compliant to in-plane stresses applied in the first plane but stiff to out-of-plane stresses.
16. The gyroscope of claim 4 , wherein the linkage beams are serpentine flexures.
17. The gyroscope of claim 7 , further including linkage beams configured to increase a transfer of a proof mass sense motion to the sense frame when the gyroscope is in a sense mode, wherein the linkage beams are connected to the sense frame near the second ends of the tapering portions.
18. A gyroscope, comprising:
sense frame means for oscillating when the gyroscope is operating in a sense mode;
proof mass means for oscillating torsionally out of the first plane, in response to an applied angular rotation, together with the sense frame means, when the gyroscope is operating in the sense mode, the proof mass means disposed outside the sense frame means;
a pair of anchors;
a plurality of drive beam means for causing drive motions of the proof mass means, the drive beam means disposed on opposing sides of the sense frame means and between the pair of anchors, the drive beam means connecting the sense frame means to the proof mass means the drive motions being torsional oscillations substantially in a plane of the drive beam means; and
sense beam means for connecting the sense frame means to the pair of anchors and for determining when the gyroscope is operating in the sense mode,
wherein the sense frame means is configured to be substantially decoupled from the drive motions of the proof mass means.
19. The gyroscope of claim 18 , further including linkage beam means for transferring a proof mass sense motion to the sense frame means when the gyroscope is operating in the sense mode.