Multiple sense axis MEMS gyroscope having a single drive mode
View Patent ↗A gyroscope includes a first drive mass driven in a first drive motion along a first axis, the first drive motion generating a first sense motion of a first sense mass in response to rotation of the gyroscope. The gyroscope further includes a second drive mass driven in a second drive motion along a second axis that is transverse to the first axis. The second drive motion generates a second sense motion of a second sense mass in response to rotation of the gyroscope. A drive spring system interconnects the two drive masses to couple the first and second drive motions so that a single drive mode can be implemented. The sense motion of each sense mass is along a third axis, where the third axis is transverse to the other axes. The sense motion is translational motion such the sense masses remain parallel to the surface of the substrate.
1. A MEMS gyroscope comprising:
a first drive mass configured to be driven in a first drive motion along a first axis;
a second drive mass configured to be driven in a second drive motion along a second axis that is transverse to said first axis, each of said first and second axes being parallel to a surface of a substrate;
a drive spring system interconnecting said first drive mass with said second drive mass to couple said first drive motion to said second drive motion, said drive spring system including a first spring element coupled to each of said first drive mass and said second drive mass, an anchor element coupled to said substrate, a second spring element interconnected between said first drive mass and said anchor element, and a third spring element interconnected between said second drive mass and said anchor element, wherein said first spring element is directly physically coupled to each of said first and second drive masses without an intervening interconnection to either of said second and third spring elements;
a first sense mass coupled to said first drive mass such that said first drive motion generates first sense motion of said first sense mass along a third axis in response to rotation of said MEMS gyroscope, said third axis being transverse to each of said first and second axes, said first sense motion being translational motion such that a first planar surface of said first sense mass remains substantially parallel to said surface of said substrate; and
a second sense mass coupled to said second drive mass such that said second drive motion generates second sense motion of said second sense mass along said third axis in response to rotation of said MEMS gyroscope, said second sense motion being translational motion such that a second planar surface of said second sense mass remains substantially parallel to said surface of said substrate.
2. A MEMS gyroscope as claimed in claim 1 wherein said drive spring system is a first drive spring system, and said MEMS gyroscope further comprises:
a third drive mass configured to be driven in said first drive motion along said first axis;
a fourth drive mass configured to be driven in said second drive motion along said second axis;
a second drive spring system interconnecting said second drive mass with said third drive mass;
a third drive spring system interconnecting said third drive mass with said fourth drive mass; and
a fourth drive spring system interconnecting said fourth drive mass with said first drive mass.
3. A MEMS gyroscope as claimed in claim 2 wherein:
said first, second, third, and fourth drive masses are uniformly arranged about a central region; and
said MEMS gyroscope further comprises a drive assembly configured to impart said first drive motion on said first drive mass such that when said first and third drive masses are driven to move along said first axis toward said central region, said second and fourth drive masses concurrently move along said second axis away from said central region.
4. A MEMS gyroscope as claimed in claim 2 further comprising:
a third sense mass coupled to said third drive mass such that said first drive motion generates said first sense motion of said third sense mass along said third axis in response to rotation of said MEMS gyroscope;
a fourth sense mass coupled to said fourth drive mass such that said second drive motion generates said second sense motion of said fourth sense mass along said third axis in response to rotation of said MEMS gyroscope;
an anchor system coupled to said substrate with said first, second, third, and fourth sense masses being arranged around said anchor system; and
compliant members, wherein each of said first, second, third, and fourth sense masses are coupled to said anchor system via said compliant members.
5. A MEMS gyroscope as claimed in claim 4 wherein:
first ones of said compliant members are interconnected between each of said first and third sense masses and said anchor system, said first ones of said compliant members enabling said first sense motion of said first and third sense masses in phase opposition; and
second ones of said compliant members are interconnected between each of said second and fourth sense masses and said anchor system, said second ones of said compliant members enabling said second sense motion of said second and fourth sense masses in said phase opposition.
6. A MEMS gyroscope as claimed in claim 1 further comprising multiple beam springs, wherein a first pair of said beam springs interconnects said first sense mass with said first drive mass and a second pair of said beam springs interconnects said second sense mass with said second drive mass.
7. A MEMS gyroscope as claimed in claim 6 wherein each of said multiple beam springs comprises:
a first compliant end;
a second compliant end, each of said first and second compliant ends being configured to tilt out of a plane perpendicular to said surface of said substrate; and
a beam section spanning between said first and second compliant ends, said beam section being rigid relative to said first and second compliant ends.
8. A MEMS gyroscope as claimed in claim 6 wherein:
each of said beam springs includes a beam section having a longitudinal axis;
said beam springs of said first pair of said beam springs are located on opposing edges of said first sense mass with said longitudinal axis of each said beam section of said each beam spring of said first pair being aligned with one another; and
said beam springs of said second pair of said beam springs are located on opposing edges of said second sense mass with said longitudinal axis of each said beam section of said each beam spring of said second pair being aligned with one another.
9. A MEMS gyroscope as claimed in claim 6 wherein:
said beam springs of said first pair of said beam springs are positioned to cooperatively retain said first sense mass in balance at a first center of gravity of said first sense mass; and
said beam springs of said second pair of said beam springs are positioned to cooperatively retain said second sense mass in balance at a second center of gravity of said second sense mass.
10. A MEMS gyroscope as claimed in claim 9 further comprising:
an anchor system coupled to said surface of said substrate;
a first compliant member interconnected between said first sense mass and said anchor system, wherein said first compliant member along with said beam springs of said first pair of said beam springs are positioned to retain said first sense mass in said balance at said first center of gravity; and
a second compliant member interconnected between said second sense mass and said anchor system, wherein said second compliant member along with said beam springs of said second pair of said beam springs are positioned to retain said second sense mass in said balance at said second center of gravity.
11. A MEMS gyroscope as claimed in claim 1 wherein:
said first drive motion is configured to generate said first sense motion along said third axis in response to rotation of said MEMS gyroscope about said second axis;
said second drive motion is configured to generate said second sense motion along said third axis in response to rotation of said MEMS gyroscope about said first axis; and
said first drive motion is configured to generate a third sense motion of one of said first and second sense masses in response to rotation of said MEMS gyroscope about said third axis.
12. A MEMS gyroscope comprising:
a first drive mass configured to be driven in a first drive motion along a first axis;
a second drive mass configured to be driven in a second drive motion along a second axis that is transverse to said first axis, each of said first and second axes being parallel to a surface of a substrate;
a drive spring system interconnecting said first drive mass with said second drive mass to couple said first drive motion to said second drive motion, said drive spring system including a first spring element coupled to each of said first drive mass and said second drive mass, an anchor element coupled to said substrate, a second spring element interconnected between said first drive mass and said anchor element, and a third spring element interconnected between said second drive mass and said anchor element, wherein said first spring element is directly physically coupled to each of said first and second drive masses without an intervening interconnection to either of said second and third spring elements;
a first sense mass;
a second sense mass;
a first pair of beam springs coupling said first sense mass to said second drive mass such that said first drive motion generates first sense motion of said first sense mass along a third axis in response to rotation of said MEMS gyroscope, said third axis being transverse to each of said first and second axes, said first sense motion being translational motion such that a first planar surface of said first sense mass remains substantially parallel to said surface of said substrate; and
a second pair of beam springs coupling said second sense mass to said second drive mass such that such that said second drive motion generates second sense motion of said second sense mass along said third axis in response to rotation of said MEMS gyroscope, said second sense motion being translational motion such that a second planar surface of said second sense mass remains substantially parallel to said surface of said substrate.
13. A MEMS gyroscope as claimed in claim 12 wherein each of said beam springs of said first and second pairs of beam springs comprises:
a first compliant end;
a second compliant end, each of said first and second compliant ends being configured to tilt out of a plane perpendicular to said surface of said substrate; and
a beam section spanning between said first and second compliant ends, said beam section being rigid relative to said first and second compliant ends.
14. A MEMS gyroscope as claimed in claim 12 wherein
said beam springs of said first pair of said beam springs are positioned to cooperatively retain said first sense mass in balance at a first center of gravity of said first sense mass; and
said beam springs of said second pair of said beam springs are positioned to cooperatively retain said second sense mass in balance at a second center of gravity of said second sense mass.
15. A MEMS gyroscope as claimed in claim 12 wherein said drive spring system is a first drive spring system, and said MEMS gyroscope further comprises:
a third drive mass configured to be driven in said first drive motion along said first axis;
a fourth drive mass configured to be driven in said second drive motion along said second axis;
a second drive spring system interconnecting said second drive mass with said third drive mass;
a third drive spring system interconnecting said third drive mass with said fourth drive mass; and
a fourth drive spring system interconnecting said fourth drive mass with said first drive mass.
16. A method of forming a MEMS gyroscope comprising:
forming a first drive mass and a first sense mass coupled to said first drive mass, said first drive mass configured to be driven in a first drive motion along a first axis;
forming a second drive mass and a second sense mass coupled to said second drive mass, said second drive mass configured to be driven in a second drive motion along a second axis that is transverse to said first axis, said first and second axes being parallel to a surface of a substrate;
forming a drive spring system interconnecting said first drive mass with said second drive mass to couple said first drive motion to said second drive motion, said drive spring system including a first spring element coupled to each of said first drive mass and said second drive mass, an anchor element coupled to said substrate, a second spring element interconnected between said first drive mass and said anchor element, and a third spring element interconnected between said second drive mass and said anchor element, wherein said first spring element is directly physically coupled to each of said first and second drive masses without an intervening interconnection to either of said second and third spring elements, wherein:
said first drive motion generates first sense motion of said first sense mass along a third axis in response to rotation of said MEMS gyroscope, said third axis being transverse to each of said first and second axes, said first sense motion being translational motion such that a first planar surface of said first sense mass remains substantially parallel to said surface of said substrate; and
said second drive motion generates second sense motion of said second sense mass along said third axis in response to rotation of said MEMS gyroscope, said second sense motion being translational motion such that a second planar surface of said second sense mass remains substantially parallel to said surface of said substrate.
17. A method as claimed in claim 16 wherein said drive spring system is a first drive spring system, and said method further comprises:
forming a third drive mass and a third sense mass coupled to said third drive mass, said third drive mass configured to be driven in said first drive motion along said first axis;
forming a fourth drive mass and a fourth sense mass coupled to said fourth drive mass, said fourth drive mass configured to be driven in said second drive motion along said second axis;
forming a second drive spring system interconnecting said second drive mass with said third drive mass;
forming a third drive spring system interconnecting said third drive mass with said fourth drive mass; and
forming a fourth drive spring system interconnecting said fourth drive mass with said first drive mass, wherein:
said first drive motion additionally generates said first sense motion of said third sense mass along said third axis in response to rotation of said MEMS gyroscope; and
said second drive motion additionally generates said second sense motion of said fourth sense mass along said third axis in response to rotation of said MEMS gyroscope.
18. A method as claimed in claim 17 further comprising:
uniformly arranging said first, second, third, and fourth drive masses about a central region; and
forming a drive assembly configured to impart said first drive motion on said first drive mass such that when said first and third drive masses are driven to move along said first axis toward said central region, said second and fourth drive masses concurrently move along said second axis away from said central region.
19. A method as claimed in claim 16 wherein:
said first drive motion is configured to generate said first sense motion along said third axis in response to rotation of said MEMS gyroscope about said second axis;
said second drive motion is configured to generate said second sense motion along said third axis in response to rotation of said MEMS gyroscope about said first axis; and
said first drive motion is configured to generate a third sense motion of one of said first and second sense masses in response to rotation of said MEMS gyroscope about said third axis.