Multi-axis accelerometers with reduced cross-axis sensitivity

Patent metadata

Field	Value
Publication number	US-10634696-B2
Application number	US-201715846386-A
Country	US
Kind code	B2
Filing date	Dec 19, 2017
Priority date	Dec 19, 2016
Publication date	Apr 28, 2020
Grant date	Apr 28, 2020

Abstract

A multi-axis accelerometer may include a proof mass, a first electrode set, and a second electrode set. The first electrode set may detect acceleration along a second axis of the accelerometer, and may include a first electrode (C 1 ) and a second electrode (C 2 ). The second electrode set may detect acceleration along a first axis of the accelerometer that is orthogonal to the second axis, and may include a third electrode (C 3 ) and a fourth electrode (C 4 ). Application of a force along only the second axis may result in the exhibition of a non-zero change in differential capacitance between at least C 1 and C 2 , but a zero net change in the differential capacitance between at least C 3 and C 4 . As such, the accelerometer may exhibit little or no cross axis sensitivity in response to the applied force.

First claim

What is claimed is:

1. A multi-axis accelerometer comprising:
a proof mass comprising:
a first side, a second side, a third side, and a fourth side, wherein said first and said third sides are generally parallel to each other and wherein said second and said fourth sides are generally parallel to each other and orthogonal to the first side;
a first opening having a first longitudinal axis extending along said first side;
a second opening having a second longitudinal axis extending along said second side;
a third opening having a third longitudinal axis extending along said third side; and
a fourth opening having a fourth longitudinal axis extending along said fourth side;

a first electrode set configured to detect acceleration along a second axis of the accelerometer, the first electrode set comprising a first electrode (C 1 ) and a second electrode (C 2 ), C 1 comprising a first rotor set and a first stator set, the first rotor set including a plurality of rotor fingers extending from two opposite sidewalls of the first opening, the first stator set comprising a first stator body disposed within the first opening and including a plurality of stator fingers extending from the first stator body generally towards the two opposite sidewalls of the first opening, C 2 comprising a second rotor set and a second stator set, the second rotor set including a plurality of rotor fingers extending from two opposite sidewalls of the second opening, the second stator set comprising a second stator body disposed within the second opening and including a plurality of stator fingers extending from the second stator body generally towards the two opposite sidewalls of the second opening;
a second electrode set configured to detect acceleration along a first axis of the accelerometer that is orthogonal to the second axis, the second electrode set comprising a third electrode (C 3 ) and a fourth electrode (C 4 ), C 3 comprising a third rotor set and a third stator set, the third rotor set including a plurality of rotor fingers extending from two opposite sidewalls of the third opening, the third stator set comprising a third stator body disposed within the third opening and including a plurality of stator fingers extending from the third stator body generally towards the two opposite sidewalls of the third opening, C 4 comprising a fourth rotor set and a fourth stator set, the fourth rotor set including a plurality of rotor fingers extending from two opposite sidewalls of the fourth opening, the fourth stator set comprising a fourth stator body disposed within the fourth opening and including a plurality of stator fingers extending from the fourth stator body generally towards the two opposite sidewalls of the fourth opening;
wherein the first and second electrode sets are configured such that in response to a force applied only along the second axis of the accelerometer:
a non-zero change in differential capacitance is exhibited between at least C 1 and C 2 , the non-zero net change in differential capacitance corresponding to acceleration along the second axis due to the force applied only along the second axis; and
a zero net change in differential capacitance is exhibited between at least C 3 and C 4 .

2. The multi-axis accelerometer of claim 1 , wherein the first and second electrode sets are configured such that in response to a force applied only along the first axis of the accelerometer:
a non-zero change in differential capacitance is exhibited between at least C 3 and C 4 , the non-zero net change in differential capacitance corresponding to acceleration along the first axis due to the force applied only along the first axis; and
a zero net change in differential capacitance is exhibited between at least C 1 and C 2 .

3. The multi-axis accelerometer of claim 2 , wherein:
the first and second electrode sets are configured such that a zero net change in differential capacitance is exhibited between at least C 1 and C 2 and between at least C 3 and C 4 in response to a force applied only along a third axis of the accelerometer; and
the third axis is orthogonal to the first axis and the second axis.

4. The multi-axis accelerometer of claim 1 , wherein:
the accelerometer further comprises an elastic member and a substrate; and
the elastic member is configured to support the plurality of rotors and the proof mass on the substrate, or to suspend the plurality of rotors fingers of C 1 , C 2 , C 3 , and C 4 and the proof mass from the substrate.

5. The multi-axis accelerometer of claim 1 , wherein:
the plurality of rotor fingers of the first and second rotor sets and the plurality of stator fingers of the first and second stator sets are each spaced apart by one or more gaps in a direction parallel to the second axis.

6. The multi-axis accelerometer of claim 5 , wherein:
the plurality of rotor fingers of the third and fourth rotor sets and the plurality of stator fingers of the third and fourth stator sets are each spaced apart by one or more gaps in a direction parallel to the first axis.

7. The multi-axis accelerometer of claim 1 , wherein:
the plurality of rotor fingers of C 1 extend from said proof mass;
the plurality of rotor fingers of C 2 extend from said proof mass;
each of said plurality of rotor fingers of C 1 is spaced apart from a respective one of said plurality of stator fingers of C 1 by a first gap with an initial gap spacing g 1 , so as to define a plurality of first capacitive pairs;
each of said plurality of rotor fingers of C 2 is spaced apart from a respective one of said plurality of stator fingers of C 2 by a second gap with the initial gap spacing g 1 , so as to define a plurality of second capacitive pairs; and
each of the plurality of plurality of rotor fingers of C 1 and C 2 is configured to move parallel to the second axis in response to the force applied along the second axis, such that the first gap decreases, and the second gap increases.

8. The multi-axis accelerometer of claim 7 , wherein each of the plurality of stator fingers of C 1 and C 2 is integral with or coupled to the substrate, and are configured to remain stationary in response to application of the force along one or more axes of the accelerometer.

9. The multi-axis accelerometer of claim 7 , wherein:
the plurality of rotor fingers of C 3 extend from said proof mass;
the plurality of rotor fingers of C 4 extend from said proof mass;
each of said plurality of rotor fingers of C 3 is spaced apart from a respective one of said plurality of stator fingers of C 3 by a third gap with an initial gap spacing g 2 , so as to define a plurality of third capacitive pairs;
each of said plurality of rotor fingers of C 4 is spaced apart from a respective one of said plurality of stator fingers of C 4 by a fourth gap with the initial gap spacing g 2 , so as to define a plurality of fourth capacitive pairs; and
each of the plurality of plurality of rotor fingers of C 3 and C 4 is configured to move parallel to the first axis in response to the force applied only along the first axis.

10. The multi-axis accelerometer of claim 9 , wherein each of the plurality of stator fingers of C 3 and C 4 is integral with or coupled to the substrate, and are configured to remain stationary in response to application of the force along one or more axes of the accelerometer.

11. The multi-axis accelerometer of claim 9 , wherein:
the initial gap spacing g 2 of the third and fourth gaps remains constant when the plurality of rotor fingers of C 3 and C 4 move in response to the force applied only along the second axis; and
a total effective capacitive area of the plurality of third an

Assignees

• Univ Khalifa Science & Technology

Inventors

• Mohammed Zakriya
• Gill Waqas Amin
• Rasras Mahmoud

Classifications

• G01P2015/0848

  using a plurality of mechanically coupled spring-mass systems, the sensitive direction of each system being different · CPC title

• B81B2201/0235

  Accelerometers · CPC title

• G01P2015/084

  the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass · CPC title

• G01P15/125

  by capacitive pick-up · CPC title

• G01C19/5712 Primary

  the devices involving a micromechanical structure · CPC title