Shock-robust integrated multi-axis MEMS gyroscope
Various embodiments of the invention integrate multiple shock-robust single-axis MEMS gyroscopes into a single silicon substrate while avoiding the complexities typically associated with designing a multi-drive control system for shock immune gyroscopes. In certain embodiments of the invention, a shock immune tri-axial MEMS gyroscope is based on a driving scheme that employs rotary joints to distribute driving forces generated by two sets of driving masses to individual sensors, thereby, simplifying the control of the gyroscope.
1. A single-drive multi-axis MEMS gyroscope for detecting movements in an orthogonal coordinate system having X-, Y-, and Z-axes, the single-drive multi-axis MEMS gyroscope comprising:
axial gyroscopes comprising proof masses;
first and second sets of driving masses configured to be driven into oscillation relative to each other in a first driving direction that takes place along a first axis of the X-, Y-, and Z-axes; and
a set of joints connected to at least one of the first and second sets of driving masses to distribute driving forces of the first and second set of driving masses in the first driving direction, the set of joints is configured to transfer the oscillation and the driving forces of the first and second sets of driving masses in the first driving direction into driving forces that oscillate the proof masses of the axial gyroscopes in second driving directions, at least some of the second driving directions being at angles relative to the first driving direction, wherein each of the second driving directions is orthogonal to a respective sense direction of the axial gyroscope associated therewith, and each of the sense directions is orthogonal to a respective second axis of the X-, Y-, and Z-axes about which the axial gyroscope associated therewith detects rotation, such that in the event of a rotation about the respective second axis of any one of the axial gyroscopes, a Coriolis force is generated in the sense direction thereof.
2. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein at least one of the axial gyroscopes is a single-axis shock-robust gyroscope.
3. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein at least two of the axial gyroscopes are disposed in a mirror image arrangement about the first axis.
4. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein the angle of at least one of the second driving directions is at positive 45 degrees to the first driving direction and the angle of at least another one of the second driving directions is at negative 45 degrees to the first driving direction.
5. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein the angle of at least one of the second driving directions is at zero degrees to the first driving direction.
6. The single-drive multi-axis MEMS gyroscope according to claim 1 , further comprising at least one of a redundant gyroscope and a dummy mass.
7. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein the set of joints constrains motions of the first and second sets of driving masses to be antiphase, synchronous, and restricted to a single degree of freedom.
8. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein the set of joints is anchored to a substrate at anchoring points to hold the set of joints onto the substrate and to enable rotary movements around the anchoring points.
9. The single-drive multi-axis MEMS gyroscope according to claim 1 , wherein the set of joints comprises a first subset of joints connected to the first set of driving masses to synchronize the oscillations of the first set of driving masses with at least a first of the proof masses in a first gyroscope of the axial gyroscopes.
10. The single-drive multi-axis MEMS gyroscope according to claim 9 , wherein the first subset of joints comprises two rotary joints connected to the first gyroscope, the two rotary joints enable at least first and second proof masses of the proof masses in the first gyroscope to move antiphase.
11. The single-drive multi-axis MEMS gyroscope according to claim 9 , wherein the set of joints comprises a second subset of joints connected to the first set of driving masses to synchronize the oscillations of the first set of driving masses with at least a second of the proof masses in a second gyroscope of the axial gyroscopes.
12. The single-drive multi-axis MEMS gyroscope according to claim 11 , wherein the second subset of joints is connected to the first set of driving masses in a mirror image arrangement about the first driving direction.
13. A system to drive a multi-axis MEMS gyroscope in an orthogonal coordinate system having X-, Y-, and Z-axes, the system comprising:
a driving element;
a multi-axis MEMS gyroscope comprising first and second driving masses coupled to the driving element, the driving element sets the first and second driving masses into an antiphase oscillation in a driving direction that takes place along a first axis of the X-, Y-, and Z-axes, the multi-axis MEMS gyroscope comprising:
a first set of joints configured to enable a proof mass in a first gyroscope to move at a first angle relative to a first spatial direction;
a second set of joints configured to enable a proof mass in a second gyroscope to move at a second angle relative to the first spatial direction;
a third gyroscope having a proof mass enabled to move at a third angle relative to the first spatial direction,
wherein each of the first, second and third angles is orthogonal to a respective sense direction that, in turn, is orthogonal to a respective second axis of the X-, Y-, and Z-axes about which the first, second, or third gyroscope associated therewith detects rotation, such that in the event of a rotation about the respective second axis of any one of the first, second, or third gyroscopes, a Coriolis force is generated in the respective sense direction; and
a control system that controls an actuation of the driving elements via comb electrodes and detects displacements of the proof masses via plate electrodes.
14. The system according to claim 13 , wherein the number of the driving masses is eight.
15. A method to drive a multi-axis MEMS gyroscope, the method comprising:
providing a plurality of single-axis gyroscopes;
distributing driving forces to the plurality of single-axis gyroscopes via a joint system;
electro-mechanically driving the plurality of single-axis gyroscopes to generate synchronous, antiphase motions; and
determining an angular acceleration with at least one of the plurality of single-axis gyroscopes.
16. The method according to claim 15 , wherein at least one of the plurality of single-axis gyroscopes is a shock-robust gyroscope.
17. The method according to claim 15 , wherein the synchronous, antiphase motions are generated by more than two masses.
18. The method according to claim 15 , further comprising controlling the synchronous, antiphase motions by an external control system.
19. The method according to claim 15 , wherein the plurality of single-axis gyroscopes comprises an in-plane gyroscope and an out-of-plane gyroscope.
20. The method according to claim 15 , wherein the joint system is a rotary joint system.