Inertial sensor with off-axis spring system
View Patent ↗An inertial sensor ( 20 ) includes a drive mass ( 30 ) configured to undergo oscillatory motion and a sense mass ( 32 ) linked to the drive mass ( 30 ). On-axis torsion springs ( 58 ) are coupled to the sense mass ( 32 ), the on-axis torsion springs ( 58 ) being co-located with an axis of rotation ( 22 ). The inertial sensor ( 20 ) further includes an off-axis spring system ( 60 ). The off-axis spring system ( 60 ) includes off-axis springs ( 68, 70, 72, 74 ), each having a connection interface ( 76 ) coupled to the sense mass ( 32 ) at a location on the sense mass ( 32 ) that is displaced away from the axis of rotation ( 22 ). Together, the on-axis torsion springs ( 58 ) and the off-axis spring system ( 60 ) enable the sense mass ( 32 ) to oscillate out of plane about the axis of rotation ( 22 ) at a sense frequency that substantially matches a drive frequency of the drive mass ( 30 ).
1. An inertial sensor comprising:
a substrate having a surface;
a drive mass configured to undergo oscillatory motion within a plane substantially parallel to said surface;
a sense mass linked to said drive mass, said sense mass including first and second ends, wherein an entirety of said first end is located on a first side of an axis of rotation, an entirety of said second end is located on a second side of said axis of rotation, and said first and second ends are symmetrically displaced away from said axis of rotation;
an on-axis torsion spring coupled to said sense mass, said on-axis torsion spring being co-located with an axis of rotation; and
an off-axis spring system having a connection interface that is coupled to said sense mass at a location on said sense mass that is displaced away from said axis of rotation, said off-axis spring system including a first off-axis spring disposed at said first end of said sense mass and a second off-axis spring disposed at said second end of said sense mass, each of said first and second off-axis springs including said connection interface, wherein said on-axis torsion spring and said off-axis spring system enable said sense mass to oscillate out of said plane.
2. An inertial sensor as claimed in claim 1 wherein said drive mass undergoes said oscillatory motion at a drive frequency, and said on-axis torsion spring and said off-axis spring system enable said sense mass to oscillate at a sense frequency that is substantially equivalent to said drive frequency.
3. An inertial sensor as claimed in claim 1 further comprising link spring components coupling said sense mass to said drive mass, wherein a first total spring constant of said on-axis torsion spring and said off-axis spring system is substantially equivalent to a second total spring constant of said link spring components.
4. An inertial sensor as claimed in claim 1 wherein said off-axis spring system restricts movement of said sense mass such that said sense mass rotates about said axis of rotation.
5. An inertial sensor as claimed in claim 1 wherein said sense mass has a central opening, and said drive mass resides in said central opening.
6. An inertial sensor as claimed in claim 1 wherein:
said sense mass includes a central opening delineated by an inner periphery of said sense mass, said inner periphery including said first and second ends;
said first off-axis spring resides in said central opening and has said connection interface disposed at said first end; and
said second off-axis spring resides in said central opening and has said connection interface disposed at said second end.
7. An inertial sensor as claimed in claim 1 wherein said on-axis torsion spring and said off-axis spring system connect said sense mass to said surface of said substrate.
8. An inertial sensor as claimed in claim 1 wherein said drive mass has a central opening, and said sense mass resides in said central opening.
9. An inertial sensor as claimed in claim 8 wherein:
said sense mass has a second central opening; and
said inertial sensor further comprises an anchor coupling said on-axis torsion spring to said surface of said substrate, said anchor being positioned in said second central opening.
10. An inertial sensor as claimed in claim 9 wherein said anchor is co-located with said axis of rotation.
11. An inertial sensor as claimed in claim 1 further comprising:
a second sense mass linked to said drive mass;
a second on-axis torsion spring coupled to said second sense mass, said second on-axis torsion spring being co-located with a second axis of rotation that is perpendicular to said axis of rotation; and
a second off-axis spring system having a second connection interface that is coupled to said second sense mass at a second location that is displaced away from said second axis of rotation, wherein said second on-axis torsion spring and said second off-axis spring system enable said second sense mass to oscillate out of said plane.
12. An inertial sensor as claimed in claim 1 wherein said drive mass comprises:
a first drive mass structure; and
a second drive mass structure, said first and second drive mass structures exhibiting reflectional symmetry relative to said axis of rotation.
13. An inertial sensor as claimed in claim 12 wherein:
said second drive mass structure is disposed in said plane laterally relative to said first drive mass structure; and
said inertial sensor further comprises a drive system configured to drive said first and second drive mass structures in opposite directions parallel to said plane.
14. An inertial sensor comprising:
a substrate having a surface;
a sense mass having first and second ends, and said sense mass including a central opening, said sense mass including first and second ends, wherein an entirety of said first end is located on a first side of an axis of rotation, an entirety of said second end is located on a second side of said axis of rotation, and said first and second ends are symmetrically displaced away from said axis of rotation;
a drive mass linked to said sense mass and residing in said central opening, said drive mass being configured to undergo oscillatory motion within a plane substantially parallel to said surface;
an on-axis torsion spring coupled to said sense mass, said on-axis torsion spring being co-located with said axis of rotation; and
an off-axis spring system including a first off-axis spring disposed at said first end of said sense mass and a second off-axis spring disposed at said second end of said sense mass, each of said first and second off-axis springs including a connection interface coupled to said sense mass at a location on said sense mass that is displaced away from said axis of rotation, wherein said on-axis torsion spring and said off-axis spring system enable said sense mass to rotate out of said plane about said axis of rotation.
15. An inertial sensor as claimed in claim 14 wherein said drive mass undergoes said oscillatory motion at a drive frequency, and said inertial sensor further comprises link spring components coupling said sense mass to said drive mass, said on-axis torsion spring and said off-axis spring system having a first total spring constant that is substantially equivalent to a second total spring constant of said link spring components to enable said sense mass to oscillate about said axis of rotation at a sense frequency that is substantially equivalent to said drive frequency.
16. An inertial sensor as claimed in claim 14 wherein:
said drive mass comprises a first drive mass structure and a second drive mass structure, said first and second drive mass structures exhibiting reflectional symmetry relative to said axis of rotation; and
said inertial sensor further comprises a drive system configured to drive said first and second drive mass structures in opposite directions parallel to said plane.
17. An inertial sensor comprising:
a substrate having a surface;
a drive mass configured to undergo oscillatory motion within a plane substantially parallel to said surface at a drive frequency, said drive mass including a first drive mass structure and a second drive mass structure, said first and second drive mass structures exhibiting reflectional symmetry relative to an axis of rotation, and said first and second drive mass structures being driven in opposite directions parallel to said plane;
a sense mass linked to said drive mass, said sense mass including first and second ends, wherein an entirety of said first end is located on a first side of an axis of rotation, an entirety of said second end is located on a second side of said axis of rotation, and said first and second ends are symmetrically displaced away from said axis of rotation;
an on-axis torsion spring coupled to said sense mass, said on-axis torsion spring being co-located with said axis of rotation; and
an off-axis spring system having a connection interface that is coupled to said sense mass at a location on said sense mass that is displaced away from said axis of rotation, said off-axis spring system including a first off-axis spring disposed at said first end of said sense mass and a second off-axis spring disposed at said second end of said sense mass, each of said first and second off-axis springs including said connection interface, wherein said on-axis torsion spring and said off-axis spring system enable said sense mass to oscillate out of said plane at a sense frequency that is substantially equivalent to said drive frequency.
18. An inertial sensor as claimed in claim 17 wherein said sense mass has a central opening, and said first and second drive mass structures reside in said central opening.