MULTI-AXIAL LINEAR AND ROTATIONAL DISPLACEMENT SENSOR

• US 20100257933A1
• Filed: 07/15/2008
• Published: 10/14/2010
• Est. Priority Date: 07/24/2007
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Giridhar, Archit, Verjus, Fabrice
• Granted Patent: US 8,397,570 B2
• Time in Patent Office: Days
• US Class Current: 73/504.40
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass
• CPC Class Codes: G01C 19/5769 Manufacturing; Mounting; Housings
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/082 for two degrees of freedom of movement of a single mass

Abstract

A MEMS multiaxial inertial sensor of angular and linear displacements, velocities or accelerations has four comb drive capacitive sensing elements (18) integrated on a planar substrate (12), each having an output responsive to displacement along a Z axis, and responsive to a displacement along X or Y axes. The sensing elements are located at different parts of the substrate on both sides of the X axis and the Y axis, the outputs being suitable for subsequently deriving linear displacements along any of the X, Y or Z axes and angular displacements about any of the X, Y or Z axes. Fewer sensing elements are needed to sense in multiple directions, making the device more cost effective or smaller. Linear or angular movement is determined from combinations of the sensor signals.

Claims

1. A multiaxial inertial sensor of angular and linear acceleration, the sensor having at least four sensing elements integrated on a planar substrate, each of the sensing elements comprising a MEMS capacitance sensing comb drive in which a capacitance varies based on the force applied, wherein each comb drive comprises fingers which are laterally movable and movable deeper into or out of respective slots, such that each comb drive has an output responsive to displacement along a Z axis normal to a plane of the substrate, as well as responsive to a displacement parallel to the plane, the elements being located at different parts of the substrate on both sides of two perpendicular axes, an X axis and a Y axis, in the plane of the substrate, the sensing elements also being oriented in different directions in the plane, so that their outputs are also responsive to displacements along the X or Y axis, the outputs being suitable for subsequently deriving linear displacements along any of the X, Y or Z axes and angular displacements about any of the X, Y or Z axes by analyzing the variations in capacitance of the different sensing elements.

3. The sensor of claim 1, the mass comprising separate masses for each sensing element.

4. The sensor of claim 3, the separate masses being distributed over a movable part of the sensing element.

5. The sensor of claim 1, having four sensing elements arranged at quadrants of a square.

6. The sensor of claim 5, and having circuitry arranged to derive displacements from outputs of the four sensing elements C1, C2, C3 and C4, with sensor C1 in a position of negative X and positive Y, sensor C2 in a position of negative X and negative Y, C3 in a position of positive X and negative Y and C4 in a position of positive X and positive Y, using the following:

Displacement along X if Δ

C2=Δ

C4>

Δ

C1=Δ

C3,

Displacement along Y if Δ

C1=Δ

C3>

Δ

C2=Δ

C4,

Displacement along Z if Δ

C1=Δ

C2=Δ

C3=Δ

C4,

Rotation about X if Δ

C2+Δ

C3=Δ

C1+Δ

C4,

Rotation about Y if Δ

C1+Δ

C2=(−

Δ

C3+Δ

C4),

Rotation about Z if Δ

C1=−

Δ

C3; and

Δ

C2=−

Δ

C4.

7. The sensor of claim 5, each sensing element comprising a comb shaped movable electrode, surrounded by a correspondingly shaped fixed electrode.

8. The sensor of claim 7, wherein the comb shapes of each of the four sensing elements being orientated to face four different directions at right angles to each other.

2. (canceled)

9. (canceled)

10. (canceled)