MULTICAPACITOR FORCE/MOMENT SENSOR ARRAYS

• US 20140076066A1
• Filed: 09/19/2012
• Published: 03/20/2014
• Est. Priority Date: 09/19/2012
• Status: Active Grant

• Current Assignee: College Park Industries, Inc. (Ossur hf)
• Original Assignee: College Park Industries, Inc. (Ossur hf)
• Inventors: Harrington, Richard H., Leydet, Michael G.
• Granted Patent: US 9,250,143 B2
• Time in Patent Office: Days
• US Class Current: 73/862.636
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 5/165 using variations in capacitance

Abstract

A multicapacitor sensor system facilitates the measurement of applied shear and moment forces. In one disclosed configuration, moments may be detectable in x, y and z directions, resulting in a full, 3-axis load cell with 6 degrees of freedom. The system may further include electrical circuitry to generate electrical drive pulses, sense amplify and buffer the voltages induced on the sense plates, and compute applied forces. An array of multicapacitor sensors that can be addressed individually without cross-talk and globally produce a map of forces and moments applied to the whole array. A MEMS implementation enables in vivo application.

Claims

1. A multicapacitor sensor system, comprising:

a drive plate or plates in the case of an array defining an electrically conductive pattern having a center point, the pattern including at least two orthogonal electrodes and at least one electrode extending radially outwardly from the center point;

an electrically conductive sensor pattern including at least one electrode parallel to each of the orthogonal electrodes and at least two electrodes parallel to each electrode extending radially outwardly from the center point; and

a compressible, elastic dielectric material separating the drive and sensor patterns, whereby the drive and sensor patterns and dielectric define a two-dimensional plane with x and y directions and a z direction perpendicular to the plane, and;

a) Forces applied to the system in the x and y directions may be detected by changes in the capacitance between the orthogonal electrodes of the drive plate pattern and the electrodes of the sense plate pattern parallel to the orthogonal electrodes, and

b) Moments applied to the system around the z direction may be detected by changes in the capacitance between the electrode extending radially outwardly from the center point of the drive plate pattern and the electrodes of the sense plate pattern parallel to the electrode extending radially outwardly.

2. The multicapacitor sensor system of claim 1, wherein the drive plate pattern includes a plurality of orthogonal electrodes forming a ring around the center point.

3. The multicapacitor sensor system of claim 1, wherein the drive plate pattern includes a plurality of orthogonal electrodes forming a plurality of rings around the center point.

4. The multicapacitor sensor system of claim 1, wherein the drive plate pattern includes a plurality of orthogonal electrodes forming a plurality of generally square rings around the center point.

5. The multicapacitor sensor system of claim 1, wherein the drive plate pattern includes a plurality of electrodes extending radially outwardly from the center point.

6. The multicapacitor sensor system of claim 1, wherein the drive plate pattern includes a plurality of orthogonal electrodes extending radially outwardly from the center point forming a cruciate shape.

7. The multicapacitor sensor system of claim 1, further including electrical circuitry operative to perform the following functions:

a) generate electrical pulses to drive the drive plate or plates,

b) sense, amplify and buffer the voltages induced on the sense plates,

c) compute changes in the capacitances between the drive and plate patterns, and

d) determine if any forces or moments have been applied to the system as a function of the changes in the capacitances.

8. The multicapacitor sensor system of claim 1, wherein the electrodes of the sense plate pattern parallel to each of the orthogonal electrodes of the drive plate pattern are formed with a plurality of segments enabling force applied in the z direction and torques around the x and y directions to be detected as a moments, resulting in a 3-axis load cell with 6 degrees of freedom.

9. The multicapacitor sensor system of claim 8, wherein:

the drive plate pattern includes a plurality of orthogonal electrodes forming a ring around the center point;

at least eight electrodes of the sense plate pattern parallel to each of the orthogonal electrodes of the drive plate pattern, resulting in a total of at least 10 separate electrically conductive nodes in the sense plate pattern.

10. The multicapacitor sensor system of claim 9, wherein the ring of the drive plate pattern forms a square shape.

11. The multicapacitor sensor system of claim 8, wherein the drive plate pattern includes a plurality of electrodes extending radially outwardly from the center point.

12. The multicapacitor sensor system of claim 8, wherein the drive plate pattern includes a plurality of orthogonal electrodes extending radially outwardly from the center point forming a cruciate shape.

13. The multicapacitor sensor system of claim 8, further including electrical circuitry operative to perform the following functions:

a) generate electrical pulses to drive the drive plate,

b) sense, amplify and buffer the voltages induced on the sense plates,

c) compute changes in the capacitances between the drive and sense patterns, and

d) determine if any forces and or moments have been applied to the system as a function of the changes in the capacitances.

14. The multicapacitor sensor system of claim 1, further comprising an array of drive and sense plates forming multiple sensor nodes with forces and moments being sensed at each node.

15. The multicapacitor sensor system of claim 8, further comprising an array of drive and sense plates forming multiple sensor nodes with forces and moments being sensed at each node with full 3-axis/6 degree of freedom capability.

16. The multicapacitor sensor system of claim 1, further comprising an array of drive and sense plates forming multiple sensor nodes with forces and moments being sensed at each node;

and

a mathematical map in a computer memory that computes the global forces and moments applied to the array.

17. The multicapacitor sensor system of claim 1, wherein the drive and sense plates form part of a hermetically sealed MicroElectroMechanical System (MEMS) device.

18. The multicapacitor sensor system of claim 8, wherein the drive and sense plates form part of a hermetically sealed MicroElectroMechanical System (MEMS) device.