Angular displacement sensor of compliant material

• US 8,941,392 B1
• Filed: 08/15/2014
• Issued: 01/27/2015
• Est. Priority Date: 08/17/2013
• Status: Active Grant

• Current Assignee: Bend Labs Inc. (Nitto Denko Corporation)
• Original Assignee: Bend Labs Inc. (Nitto Denko Corporation)
• Inventors: Reese, Shawn P.
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): Clarke, Adam
• Application Number:
  US14/460,726
• Publication Number:
  US 20150048849A1
• Time in Patent Office: 165 Days
• Field of Search: 324/658, 324/671, 324/686
• US Class Current: 324/671
• CPC Class Codes: A61B 2562/0261 Strain gauges
• CPC Class Codes: A61B 5/1071 measuring angles, e.g. using goniometers A61B5/1123 takes precedence
• CPC Class Codes: A61B 5/6801 specially adapted to be attached to or worn on the body surface
• CPC Class Codes: G01B 7/003 for measuring position, not involving coordinate determination coordinate measuring G01B7/004
• CPC Class Codes: G01B 7/22 using change in capacitance
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01L 1/142 using capacitors

Abstract

Disclosed is a sensing device that includes a flexible substrate having an elongated structure extending between a first end and a second end, the elongated structure being compliant material that is flexible and bendable from a linear, non-bent position to multiple bendable positions. The sensing device also includes a first compliant strain sensing element embedded within the compliant material and extending between the first end and the second end along a longitudinal length of the elongated structure. The first compliant strain sensing element includes a second compliant material that is flexible and bendable, where an electrical property of the first compliant strain sensing element changes in proportion to an applied strain on the elongated structure.

Claims

1. A sensor system comprising:

an angular displacement sensor comprising;

an elongated structure extending between a first end and a second end, the elongated structure being compliant material that is flexible and bendable from a linear, non-bent position to multiple bendable positions; and

a first compliant capacitor, wherein the first compliant capacitor comprises a first conductive layer embedded within and extending from the first end to the second end along a longitudinal length of the elongated structure to form a first electrode of the first compliant capacitor, a second conductive layer embedded within and extending from the first end to the second end along the longitudinal length to form a second electrode of the first compliant capacitor, and an elastomer dielectric layer extending between the first conductive layer and the second conductive layer;

a circuit coupled to the first compliant capacitor, the circuit to measure a capacitance of the first compliant capacitor to sense bending movement of the elongated structure based on the capacitance of the first compliant capacitor;

a first rigid member coupled to the first end of the angular displacement sensor, the first rigid member defining a first vector corresponding with an axis of the angular displacement sensor when the elongated structure is in the linear, non-bent position; and

a second rigid member coupled to the second end of the angular displacement sensor, the second rigid member defining a second vector corresponding with the axis of the angular displacement sensor, and

wherein the circuit is configured to determine an angular displacement between the first vector and the second vector within a first plane defined and extending along the longitudinal length and extending orthogonal through a width of the first compliant capacitor.

2. The sensor system of claim 1, wherein the angular displacement sensor comprises a plurality of compliant strain sensors having a width and extending along the longitudinal length of the elongated structure and spaced from the first compliant capacitor in a parallel manner such that a sensitivity of the angular displacement is increased.

3. The sensor system of claim 1,

wherein the compliant material is an elastomer based material,

wherein the capacitance of the first compliant capacitor changes in proportion to an applied strain on the elongated structure, wherein the first compliant capacitor comprises:

first conductive filler embedded within the elastomer based material to form the first electrode; and

second conductive filler embedded within the elastomer based material to form the second electrode, wherein the first conductive layer and second conductive layer extend linearly in separate planes that are parallel relative to one another throughout the elongated structure from the first end to the second end.

4. The sensor system of claim 1, wherein the first compliant capacitor has a width:

wherein the width of the first compliant capacitor is defined as a distance between two sides of at least one of the first electrode or second electrode, wherein the first electrode extends linearly in a first plane from the first end to the second end of the elongated structure and the second electrode extends linearly in a second plane from the first end to the second end of the elongated structure.

5. The sensor system of claim 1, wherein the first compliant capacitor further comprises a spring electrode extending along, through or partially through at least one of the first electrode or the second electrode of the first compliant capacitor, wherein the spring electrode is at least one of wavy or substantially flat.

6. The sensor system of claim 1, wherein the first compliant capacitor has a cross sectional shape that is at least one of a rectangular shape, a square shape, an ellipsoidal shape, or a circular shape, wherein a width of the first compliant strain sensing element is defined as a distance between two sides of the first compliant capacitor.

7. The sensor system of claim 1, wherein the compliant material of the elongated structure is an elastomer based material to facilitate bending of the elongated structure, wherein the elastomer based material is at least one of a thermoset elastomer or a thermoplastic elastomer.

8. The sensor system of claim 1, wherein the elastomer dielectric layer is at least one of a thermoset elastomer or a thermoplastic elastomer.

9. The sensor system of claim 1, wherein the first and second electrodes each comprises an elastomer composite comprising an elastomer matrix, wherein the elastomer matrix comprises conductive filler and at least one of a thermoset elastomer or a thermoplastic elastomer, wherein the conductive filler is at least one carbon nanotubes, carbon nanofibers, nickel nanostrands, or silver nanowires.

10. The sensor system of claim 1, wherein the circuit comprises a differential measurement circuit configured to determine the angular displacement between the first vector and the second vector based on a difference between outputs of the first compliant capacitor and the second compliant capacitor.

11. The sensor system of claim 1, wherein the angular displacement sensor comprises a second pair of compliant capacitors embedded within the compliant material, the second pair of compliant capacitors having a width and extending along the longitudinal length of the elongated structure and spaced from each other in a parallel manner, the width of the second pair of compliant capacitors oriented orthogonally with respect to the width of a first pair of the first and second compliant capacitors.

12. The sensor system of claim 11, further comprising:

wherein the circuit is further configured to determine a second angular displacement between the first vector and second vector that correspond with a second plane defined and extending along the length of the elongated structure and extending orthogonal through the width of the second pair.

13. The sensor system of claim 11, wherein the angular displacement sensor comprises an additional compliant capacitor oriented in a helical fashion or an additional pair of additional compliant capacitors oriented in a cohelical fashion and extending through the longitudinal length of the elongated structure and embedded within the compliant material of the elongated structure.

14. The sensor system of claim 13, further comprising:

wherein the circuit is further configured to determine a second angular displacement between the first vector and second vector that correspond with a second plane defined and extending along the length of the elongated structure and extending orthogonal through the width of the second pair, and to determine a third angular displacement around the axis of the angular displacement sensor and within a third plane orthogonal to this axis when a torsional displacement is applied to the first and second rigid members, and wherein the third plane is orthogonal to the first and second planes.

15. A sensor system comprising:

an angular displacement sensor comprising;

an elongated structure extending between a first end and a second end, the elongated structure being compliant material that is flexible and bendable from a linear, non-bent position to multiple bendable positions;

a first compliant capacitor, wherein the first compliant capacitor comprises a first conductive layer embedded within and extending from the first end to the second end along a longitudinal length of the elongated structure to form a first electrode of the first compliant capacitor, a second conductive layer embedded within and extending from the first end to the second end along the longitudinal length to form a second electrode of the first compliant capacitor, and an elastomer dielectric layer extending between the first conductive layer and the second conductive layer; and

a second compliant capacitor embedded within the compliant material, the second compliant capacitor having a width and extending along the longitudinal length of the elongated structure and spaced from the first compliant capacitor in a parallel manner, wherein the first and second compliant capacitors are offset from a center axis of the elongated structure and are reflected about the center axis of the elongated structure; and

a circuit coupled to the first compliant capacitor, the circuit to measure a capacitance of the first compliant capacitor to sense bending movement of the elongated structure based on the capacitance of the first compliant capacitor, wherein the circuit is further configured to measure a second capacitance of the second compliant capacitor to sense the bending movement of the elongated structure, wherein the bending movement of the elongated structure induces an opposing response between the first compliant capacitor and the second compliant capacitor.

16. The sensor system of claim 15, wherein the angular displacement sensor comprises a second pair of compliant capacitors embedded within the compliant material, the second pair of compliant capacitors having a width and extending along the longitudinal length of the elongated structure and spaced from each other in a parallel manner, the width of the second pair of compliant capacitors oriented orthogonally with respect to the width of a first pair of the first and second compliant capacitors.

17. The sensor system of claim 16, further comprising:

a first rigid member coupled to the first end of the angular displacement sensor, the first rigid member defining a first vector corresponding with an axis of the angular displacement sensor when the elongated structure is in the linear, non-bent position; and

a second rigid member coupled to the second end of the angular displacement sensor, the second rigid member defining a second vector corresponding with the axis of the angular displacement sensor,

wherein the circuit is configured to determine a first angular displacement between the first vector and the second vector within a first plane defined and extending along the longitudinal length and extending orthogonal through the width of the first pair and to determine a second angular displacement between the first vector and second vector that correspond with a second plane defined and extending along the length of the elongated structure and extending orthogonal through the width of the second pair.

18. The sensor system of claim 16, wherein the angular displacement sensor comprises an additional compliant capacitor oriented in a helical fashion or an additional pair of additional compliant capacitors oriented in a cohelical fashion and extending through the longitudinal length of the elongated structure and embedded within the compliant material of the elongated structure.

19. The sensor system of claim 18, further comprising:

a first rigid member coupled to the first end of the angular displacement sensor, the first rigid member defining a first vector corresponding with an axis of the angular displacement sensor when the elongated structure is in the linear, non-bent position; and

a second rigid member coupled to the second end of the angular displacement sensor, the second rigid member defining a second vector corresponding with the axis of the angular displacement sensor, and wherein the circuit is configured to determine a first angular displacement between the first vector and the second vector within a first plane defined and extending along the longitudinal length and extending orthogonal through the width of the first pair, a second angular displacement between the first vector and second vector that correspond with a second plane defined and extending along the length of the elongated structure and extending orthogonal through the width of the second pair, and a third angular displacement around the axis of the angular displacement sensor and within a third plane orthogonal to this axis when a torsional displacement is applied to the first and second rigid members, and wherein the third plane is orthogonal to the first and second planes.

20. The sensor system of claim 15, wherein the first compliant capacitor has a width, the width of the first compliant capacitor being defined as a distance between two sides of at least one of the first electrode or second electrode, wherein the first electrode extends linearly in a first plane from the first end to the second end of the elongated structure and the second electrode extends linearly in a second plane from the first end to the second end of the elongated structure.

21. The sensor system of claim 15, wherein the first compliant capacitor further comprises a spring electrode extending along, through or partially through at least one of the first electrode or the second electrode of the first compliant capacitor.

22. The sensor system of claim 15, wherein the compliant material of the elongated structure is an elastomer based material to facilitate bending of the elongated structure, wherein the elastomer based material is at least one of a thermoset elastomer or a thermoplastic elastomer.

23. The sensor system of claim 15, wherein the elastomer dielectric layer is at least one of a thermoset elastomer or a thermoplastic elastomer.

24. The sensor system of claim 15, wherein at least one of the first and second electrodes comprises an elastomer composite comprising an elastomer matrix, wherein the elastomer matrix comprises conductive filler and at least one of a thermoset elastomer or a thermoplastic elastomer.

25. The sensor system of claim 15, wherein the first compliant capacitor has a cross sectional shape that is at least one of a rectangular shape, a square shape, an ellipsoidal shape, or a circular shape, wherein a width of the first compliant strain sensing element is defined as a distance between two sides of the first compliant capacitor.

26. The sensor system of claim 15, further comprising:

a first rigid member coupled to the first end of the angular displacement sensor, the first rigid member defining a first vector corresponding with an axis of the angular displacement sensor when the elongated structure is in the linear, non-bent position; and

a second rigid member coupled to the second end of the angular displacement sensor, the second rigid member defining a second vector corresponding with the axis of the angular displacement sensor,

wherein the circuit comprises a differential measurement circuit configured to determine an angular displacement between the first vector and the second vector within a first plane defined and extending along the longitudinal length and extending orthogonal through a width of the first compliant capacitor based on a difference between outputs of the first compliant capacitor and the second compliant capacitor.

27. The sensor system of claim 15, wherein the compliant material is an elastomer based material, wherein the capacitance of the first compliant capacitor changes in proportion to an applied strain on the elongated structure, wherein the first compliant capacitor comprises:

first conductive filler embedded within the elastomer based material to form the first electrode; and

second conductive filler embedded within the elastomer based material to form the second electrode, wherein the first conductive layer and second conductive layer extend linearly in separate planes that are parallel relative to one another throughout the elongated structure from the first end to the second end.

28. A sensor system comprising:

an angular displacement sensor comprising;

an elongated structure extending between a first end and a second end, the elongated structure being compliant material that is flexible and bendable from a linear, non-bent position to multiple bendable positions; and

a first pair of compliant capacitors, wherein the first pair of compliant capacitors each comprises a first conductive layer embedded within and extending from the first end to the second end along a longitudinal length of the elongated structure to form an outer electrode, a second conductive layer embedded within and extending from the first end to the second end along the longitudinal length to form an inner electrode, and an elastomer dielectric layer extending between the first conductive layer and the second conductive layer, wherein the first pair of compliant capacitors are offset from a center axis of the elongated structure and are reflected about the center axis;

a first rigid member coupled to the first end of the angular displacement sensor, the first rigid member defining a first vector corresponding with an axis of the angular displacement sensor when the elongated structure is in the linear, non-bent position; and

a second rigid member coupled to the second end of the angular displacement sensor, the second rigid member defining a second vector corresponding with the axis of the angular displacement sensor, wherein bending movement of the elongated structure induces an opposing response between the first pair of compliant capacitors that is proportional to an applied strain on the elongated structure.

29. The sensor system of claim 28, wherein the first and second rigid members are composed of a material to prevent motion of ends of the angular displacement sensor with respect to a substrate with which the material is attached and to make the ends rigid with respect to that substrate, wherein the substrate comprises at least one of plastic, metal, elastomers, material, cloth, or wires strings.

30. The sensor system of claim 28, wherein the first and second rigid members comprise material that at least completely encases, partially encases, is embedded within, or attached to ends of the angular displacement sensor.

31. The sensor system of claim 28, further comprising an attachment mechanism coupled to a substrate to which the first rigid member is attached, wherein the attachment mechanism is at least one of a strap, a hook and loop fastener, an adhesive, a fabric sleeve, or a wire.

32. The sensor system of claim 31, wherein the attachment mechanism is configured to couple the first rigid member and the second rigid member to a human appendage.

33. The sensor system of claim 28, further comprising an interface device coupled to the angular displacement sensor, wherein the interface device comprises a user interface and a micro-controller to calculate angular displacement of the angular displacement to measure movement of a human appendage and to store the calculated angular displacement.

34. The sensor system of claim 33, further comprising a feedback device configured to provide feedback to a user via at least one of a visual notification, an audible notification, or a tactile notification.