Capacitive tactile sensor with nested matrix electrodes

• US 20170010707A1
• Filed: 09/07/2015
• Published: 01/12/2017
• Est. Priority Date: 07/07/2015
• Status: Active Grant

• Current Assignee: Pressure Profile Systems Inc. (PPS U.K. Limited)
• Original Assignee: Pressure Profile Systems Inc. (PPS U.K. Limited)
• Inventors: Son, Jae S.
• Granted Patent: US 9,983,744 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 2203/04112 Electrode mesh in capacitive digitiser: electrode for touch sensing is formed of a mesh of very fine, normally metallic, interconnected lines that are almost invisible to see. This provides a quite large but transparent electrode surface, without need for ITO or similar transparent conductive material
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/0447 Position sensing using the local deformation of sensor cells
• CPC Class Codes: H05K 1/0296 Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295 H05K1/11 takes precedence; lay-out adapted to mounted component configuration H05K1/18
• CPC Class Codes: H05K 2201/0145 Polyester, e.g. polyethylene terephthalate [PET], polyethylene naphthalate [PEN]
• CPC Class Codes: H05K 2201/0154 Polyimide
• CPC Class Codes: H05K 2201/10151 Sensor

Abstract

A capacitive tactile sensor for measuring location and force of touch from an external object includes a drive electrode layer separated from a sense electrode layer by a dielectric substrate, which may be a two-sided FPCB. A first deformable conductive shield layer is further provided and is separated from either the drive electrode layer or the sense electrode layer by a first compressible dielectric layer. A control electronics are operatively connected to all of the drive electrode layer, sense electrode layer, and the first conductive shield layer. The control electronics may be configured to measure a change in capacitance upon the external object imparting local mechanical compression onto the first conductive shield layer and the first compressible dielectric layer. The tactile sensor improves reliability of interconnections between drive and sense electrodes and the control electronics.

Claims

1. A capacitive tactile sensor for measuring location of touch and force of touch imparted by an external object, said tactile sensor comprising:

an array of electrodes with a drive electrode layer separated from a sense electrode layer by a dielectric substrate, at least one of said drive electrode layer or said sense electrode layer comprising a plurality of individual electrodes, at least one of said individual electrodes in turn comprising three or more parallel fine conductors,

a first deformable conductive shield layer separated from either said drive electrode layer or said sense electrode layer by a first compressible dielectric layer, and

a control electronics operatively connected to said drive electrode layer, said sense electrode layer, and said first conductive shield layer, said control electronics configured to measure a change in capacitance upon imparting local mechanical compression onto said first conductive shield layer and said first compressible dielectric layer by said external object.

2. The tactile sensor as in claim 1, wherein said dielectric substrate separating said drive electrode layer from said sense electrode layer is non-compressible.

3. The tactile sensor as in claim 2, wherein said dielectric substrate has a thickness ranging from about 10 microns to about 100 microns.

4. The tactile sensor as in claim 1, wherein said array of electrodes is a flexible printed circuit board or printed electronics.

5. The tactile sensor as in claim 4, wherein said drive electrode layer and said sense electrode layer are placed on opposite sides of a polymer thin film forming together said flexible printed circuit board.

6. The tactile sensor as in claim 3, wherein said dielectric substrate is a thin film made from a flexible polymer.

7. The tactile sensor as in claim 6, wherein said flexible polymer is selected from a group consisting of a polyester polymer, a PEEK polymer, a polyimide polymer, and a polyethylene terephthalate polymer.

8. The tactile sensor as in claim 1, wherein said array of electrodes is formed as printed conductive electrodes on said dielectric substrate.

9. The tactile sensor as in claim 1, wherein a ratio of a width of a fine conductor to a gap between adjacent fine conductors in at least some individual electrodes is in a range from about 0.5 to about 1.5.

10. The tactile sensor as in claim 1, wherein the width of the fine conductor or the gap between adjacent fine conductors is in a range from about 25 microns to about 100 microns.

11. The tactile sensor as in claim 1, wherein said first compressible dielectric layer has a thickness ranging from about 50 microns to about 200 microns.

12. The tactile sensor as in claim 1 further comprising a second compressible dielectric layer adjacent to either said sense electrode layer or said drive electrode layer, said second compressible dielectric layer located on the opposite side of said tactile sensor relative to said first compressible dielectric layer.

13. The tactile sensor as in claim 12 further comprising a second deformable conductive shield layer separated from either said drive electrode layer or said sense electrode layer by said second compressible dielectric layer, said second conductive shield layer is operably connected to said control electronics.

14. The tactile sensor as in claim 1, wherein said control electronics is configured to determine said location and force of touch by said external object by detecting attenuation of conductive field formed between said drive electrode layer and said sense electrode layer upon energizing thereof using said control electronics, said attenuation being a result of imparting a depression in said first compressible dielectric layer by said external object.

15. The tactile sensor as in claim 14, wherein said control electronics is configured to use said first conductive shield layer to isolate said conductive field from influence of said external object being in vicinity thereof and regardless of whether said external object is non-conductive, conductive, or grounded.

16. The tactile sensor as in claim 1, wherein said drive electrode layer comprises a plurality of parallel drive electrodes forming rows or said array, said sense electrode layer comprises a plurality of parallel sense electrodes forming columns of said array.

17. A capacitive tactile sensor for measuring location of touch and force of touch imparted by an external object, said tactile sensor comprising:

an array of electrodes with a plurality of drive electrode separated from a plurality of sense electrode layer by a non-compressible dielectric substrate,

a first deformable conductive shield layer separated from either said drive electrode layer or said sense electrode layer by a first compressible dielectric layer, and

a control electronics operatively connected to said drive electrode layer, said sense electrode layer, and said first conductive shield layer, said control electronics configured to energize said drive electrodes and said sense electrodes to create a conductive field, isolate said conductive field from influence by said external object using said first deformable conductive shield, and determine location of touch and force of touch from said external object using mechanical deformation of said first compressible layer and a corresponding attenuation of said conductive field associated with said drive electrodes and said sense electrodes.

18. A capacitive tactile sensor for measuring location of touch and force of touch imparted by an external object, said tactile sensor comprising:

an array of electrodes with a drive electrode layer separated from a sense electrode layer by a dielectric substrate, at least one of said drive electrode layer or said sense electrode layer comprising a plurality of individual electrodes, at least one of said individual electrodes in turn comprising three or more parallel fine conductors,

a first compressible dielectric layer adjacent to said array of electrodes, and

a control electronics operatively connected to said drive electrode layer and said sense electrode layer, said control electronics configured to measure a change in capacitance upon imparting local mechanical compression onto said first compressible dielectric layer by said external object.

19. The tactile sensor as in claim 18, wherein said array of electrodes is a flexible printed circuit board or printed electronics, and a ratio of a width of a fine conductor to a gap between adjacent fine conductors in at least some individual electrodes of said array of electrodes is in a range from about 0.5 to about 1.5.

20. The tactile sensor as in claim 18 further comprising a second compressible dielectric layer positioned adjacent to said array of electrodes and on the opposite side of said first dielectric compressible layer.