Inertial sensor and method of levitation effect compensation

• US 9,335,170 B2
• Filed: 11/28/2012
• Issued: 05/10/2016
• Est. Priority Date: 11/28/2012
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Lin, Yizhen, Mehner, Jan, Naumann, Michael
• Primary Examiner(s): Martin, Laura
• Assistant Examiner(s): Shah, Samir M
• Application Number:
  US13/687,299
• Publication Number:
  US 20140144231A1
• Time in Patent Office: 1,259 Days
• US Class Current: 1/1
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion

Abstract

An inertial sensor (110) includes a drive system (118) configured to oscillate a drive mass (114) within a plane (24) that is substantially parallel to a surface (50) of a substrate (28). The drive system (118) includes first and second drive units (120, 122) having fixed fingers (134, 136) interleaved with movable fingers (130, 132) of the drive mass (114). At least one of the drive units (120) is located on each side (126, 128) of the drive mass (114). Likewise, at least one of the drive units (122) is located on each side (126, 128) of the drive mass (114). The drive units (122) are driven in phase opposition to the drive units (120) so that a levitation force (104) generated by the drive units (122) compensates for, or at least partially suppresses, a levitation force (100) generated by the drive units (120).

Claims

1. An inertial sensor comprising:

a substrate;

a drive mass flexibly coupled to said substrate, said drive mass including first movable fingers and second movable fingers, said drive mass having first and second opposing sides delineated by a centerline of said drive mass; and

a drive system configured to oscillate said drive mass within a plane substantially parallel to a surface of said substrate, said drive system comprising;

first drive units coupled to said substrate and having first fixed fingers interleaved with said first movable fingers, at least one of said first drive units being located at said first side and at least another one of said first drive units being located at said second side; and

second drive units coupled to said substrate and having second fixed fingers interleaved with said second movable fingers, at least one of said second drive units being located at said first side and at least another one of said second drive units being located at said second side, and said second drive units being driven in phase opposition to said first drive units.

2. An inertial sensor as claimed in claim 1 wherein:

said inertial sensor is configured to detect angular velocity about an input axis that is substantially parallel to said surface of said substrate;

said drive system moves said drive mass in an oscillatory motion along a drive axis that is substantially parallel to said surface of said substrate and substantially perpendicular to said input axis;

said first drive units produce a first error component detectable along a sense axis that is substantially perpendicular to said surface of said substrate; and

said second drive units produce a second error component detectable along said sense axis, and at least a first portion of said first error component substantially cancels at least a second portion of said second error component.

3. An inertial sensor as claimed in claim 2 wherein said centerline of said drive mass is substantially parallel to said input axis.

4. An inertial sensor as claimed in claim 2 wherein said drive mass undergoes said oscillatory motion at a drive frequency, and said at least a first portion of said first error component and said at least a second portion of said second error component include a first harmonic frequency of said drive frequency.

5. An inertial sensor as claimed in claim 1 further comprising:

a sense mass; and

flexible support elements connecting said sense mass to said drive mass, said flexible support elements enabling said sense mass to oscillate relative to said sense axis in response to said angular velocity.

6. An inertial sensor as claimed in claim 1 wherein:

said at least one of said first drive units located at said first side of said drive mass is aligned transverse to said centerline with said at least another one of said second drive units located at said second side; and

said at least one of said second drive units located at said first side is aligned transverse to said centerline with said at least another one of said first drive units located at said second side of said drive mass.

7. An inertial sensor as claimed in claim 1 wherein:

said at least one of said second drive units located at said first side is adjacent to said at least one of said first drive units located at said first side; and

said at least another one of said second drive units located at said second side is adjacent to said at least another one of said first drive units located at said second side.

8. An inertial sensor as claimed in claim 1 wherein:

each of said first drive units includes a first overlap region in which said first movable fingers and said first fixed fingers are immediately adjacent to one another; and

each of said second drive units includes a second overlap region in which said second movable fingers and said second fixed fingers are immediately adjacent to one another, and said first and second overlap regions exhibit an overlap length that is substantially equivalent for said each of said first and second drive units.

9. An inertial sensor as claimed in claim 8 wherein said first and second overlap regions are displaced away from said centerline an equivalent distance.

10. An inertial sensor as claimed in claim 1 wherein said first and second drive units are displaced away from said centerline toward an outer perimeter of said drive mass.

11. An inertial sensor as claimed in claim 1 wherein said drive mass is a first drive mass, and:

said inertial sensor further comprises a second drive mass flexibly coupled to said substrate, said second drive mass including third movable fingers and fourth movable fingers, said second drive mass having third and fourth opposing sides delineated by a second centerline of said second drive mass; and

said drive system is configured to oscillate said second drive mass within said plane in antiphase to said first drive mass, said drive system further including;

third drive units coupled to said substrate and having third fixed fingers interleaved with said third movable fingers, at least one of said third drive units being located at said third side and at least another one of said third drive units being located at said fourth side; and

fourth drive units coupled to said substrate and having fourth fixed fingers interleaved with said fourth movable fingers, at least one of said fourth drive units being located at said third side and at least another one of said fourth drive units being located at said fourth side, said third drive units being driven in phase opposition to said fourth drive units.