Multiple axis rate sensor
View Patent ↗A microelectromechanical systems (MEMS) device includes at least two rate sensors ( 20, 50 ) suspended above a substrate ( 30 ), and configured to oscillate parallel to a surface ( 40 ) of the substrate ( 30 ). Drive elements ( 156, 158 ) in communication with at least one of the rate sensors ( 20, 50 ) provide a drive signal ( 168 ) exhibiting a drive frequency. One or more coupling spring structures ( 80, 92, 104, 120 ) interconnect the rate sensors ( 20, 50 ). The coupling spring structures enable oscillation of the rate sensors ( 20, 50 ) in a drive direction dictated by the coupling spring structures. The drive direction for the rate sensors ( 20 ) is a rotational drive direction ( 43 ) associated with a first axis ( 28 ), and the drive direction for the rate sensors ( 50 ) is a translational drive direction ( 64 ) associated with a second axis ( 24, 26 ) that is perpendicular to the first axis ( 28 ).
1. A microelectromechanical systems (MEMS) device comprising:
a first rate sensor;
a second rate sensor, said first and second rate sensors being configured to oscillate parallel to a planar surface;
drive elements in communication with at least one of said first and second rate sensors for providing a drive signal exhibiting a drive frequency; and
a first coupling spring structure interconnecting said first and second rate sensors, said first coupling spring structure enabling oscillation of said first and second rate sensors at said drive frequency in a drive direction dictated by said coupling spring structure, wherein said drive direction for said first rate sensor is a first drive direction associated with a first axis and said drive direction for said second rate sensor is a second drive direction associated with a second axis, said second axis being perpendicular to said first axis; and wherein
said first axis is perpendicular to said planar surface, said first drive direction is a rotational drive direction such that said first rate sensor is driven in said rotational drive direction about said first axis; and
said second axis is parallel to said planar surface, said second drive direction is a translational drive direction such that said second rate sensor is driven in said translational drive direction parallel to said second axis.
2. A MEMS device as claimed in claim 1 wherein each of said first and second rate sensors comprises:
a drive frame having a central opening; and
a sense mass positioned in said central opening and flexibly coupled to said drive frame, wherein said first coupling spring structure is interconnected with said drive frame of said each of said first and second rate sensors.
3. A MEMS device as claimed in claim 1 wherein
said first coupling spring structure interconnecting said first and second rate sensors is stiff in said translational drive direction and compliant relative to a third axis that is orthogonal to each of said first and second axes.
4. A MEMS device as claimed in claim 1 further comprising:
a third rate sensor disposed beside said second rate sensor; and
a second coupling spring structure interconnecting said second and third rate sensors, said second coupling spring structure enabling oscillation of said third rate sensor at said drive frequency in said drive direction dictated by said second coupling spring structure.
5. A MEMS device as claimed in claim 4 wherein said drive direction for said third rate sensor is said second drive direction, and said second coupling spring structure constrains said oscillation of said second and third rate sensors to anti-phase motion.
6. A MEMS device as claimed in claim 4 further comprising:
a fourth rate sensor disposed beside said third rate sensor; and
a third coupling spring structure interconnecting said third and fourth rate sensors, said third coupling spring structure enabling oscillation of said fourth rate sensor at said drive frequency in said drive direction dictated by said third coupling spring structure.
7. A MEMS device as claimed in claim 6 wherein said first, second, third, and fourth rate sensors are arranged in a row.
8. A MEMS device as claimed in claim 6 wherein:
said first, second, third, and fourth rate sensors are arranged around a central location of said planar surface; and
said MEMS device further comprises a fourth coupling spring structure interconnected between said first and fourth rate sensors.
9. A MEMS device as claimed in claim 1 wherein said first coupling spring structure comprises:
a first spring element coupled to said first rate sensor;
a second spring element coupled to said second rate sensor; and
a pivot lever having an anchor coupled to said planar surface, said pivot lever being configured to oscillate about a pivot axis centered at said anchor and perpendicular to said planar surface, said first spring element being coupled to said pivot lever, and said second spring element being coupled to said pivot lever.
10. A MEMS device as claimed in claim 9 wherein:
said first rate sensor exhibits a first midline oriented parallel to said planar surface, said first spring element being coupled with said first rate sensor at a location offset from said first midline; and
said second rate sensor exhibits a second midline oriented parallel to said planar surface and parallel to said first midline, said second spring element being coupled with said second rate sensor at a second location along said second midline.
11. A MEMS device as claimed in claim 10 wherein
said first and second spring elements are stiff in said translational drive direction and compliant relative to a third axis that is orthogonal to each of said first and second axes.
12. A MEMS device as claimed in claim 1 further comprising:
a third rate sensor disposed beside said second rate sensor; and
a second coupling spring structure interconnecting said second and third rate sensors, said second coupling spring structure enabling oscillation of said third rate sensor at said drive frequency in said drive direction dictated by said second coupling spring structure, said second coupling spring structure including:
a first spring element coupled to said second rate sensor;
a second spring element coupled to said third rate sensor; and
a pivot lever having an anchor coupled to said planar surface, said pivot lever being configured to oscillate about a pivot axis centered at said anchor and perpendicular to said planar surface, said first spring element being coupled to said pivot lever, and said second spring element being coupled to said pivot lever.
13. A MEMS device as claimed in claim 12 wherein
said first and second spring elements are stiff in said translational drive direction and compliant relative to a third axis that is orthogonal to each of said first and second axes.
14. A MEMS device as claimed in claim 12 further comprising:
a fourth rate sensor disposed beside said third rate sensor such that said first, second, third, and fourth rate sensors are arranged in a row;
a third coupling spring structure interconnecting said third and fourth rate sensors, said third coupling spring structure enabling oscillation of said fourth rate sensor at said drive frequency in said drive direction dictated by said third coupling spring structure; and
said second coupling spring structure further includes a third spring element and a fourth spring element, said third spring element being coupled to each of said first rate sensor and said pivot lever, and said fourth spring element being coupled to each of said fourth rate sensor and said pivot lever.
15. A microelectromechanical systems (MEMS) device comprising:
a plurality of rate sensors configured to oscillate parallel to a planar surface;
drive elements in communication with at least one of said rate sensors for providing a drive signal exhibiting a drive frequency; and
coupling spring structures interconnecting said plurality of rate sensors, said coupling spring structures enabling oscillation of each of said plurality of rate sensors at said drive frequency in a drive direction dictated by said coupling spring structures, wherein:
said drive direction for a first subset of said rate sensors is a rotational drive direction associated with a first axis that is perpendicular to said planar surface, such that said first subset of said rate sensors is driven into rotational oscillation about said first axis; and
said drive direction for a second subset of said rate sensors is a translational drive direction associated with a second axis that is parallel to said planar surface, such that said second subset of said rate sensors is driven into translational oscillation parallel to said second axis.
16. A MEMS device as claimed in claim 15 wherein said plurality of rate sensors comprises:
a first rate sensor;
a second rate sensor interconnected with said first rate sensor via a first one of said coupling spring structures;
a third rate sensor interconnected with said second rate sensor via a second one of said coupling spring structures; and
a fourth rate sensor interconnected with said third rate sensor via a third one of said coupling spring structures, wherein said first and fourth rate sensors form said first subset of said rate sensors configured to undergo said rotational oscillation and said second and third rate sensors form said second subset of said rate sensors configured to undergo said translational oscillation.
17. A MEMS device as claimed in claim 16 wherein said second one of said coupling spring structures constrains said translational oscillation of said second and third rate sensors to anti-phase motion.