Capacitive tactile sensor

• US 4,584,625 A
• Filed: 09/11/1984
• Issued: 04/22/1986
• Est. Priority Date: 09/11/1984
• Status: Expired due to Fees

• Current Assignee: Nelson R. Kellogg
• Original Assignee: Nelson R. Kellogg
• Inventors: Kellogg, Nelson R.
• Primary Examiner(s): GRIFFIN, DONALD
• Application Number:
  US06/649,312
• Time in Patent Office: 588 Days
• Field of Search: 361/283, 73/718, 73/721, 901/33, 414/5
• US Class Current: 361/283.1
• CPC Class Codes: B25J 13/084 Tactile sensors in general G01L5/16, G01L5/22
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G01L 5/228 using tactile array force sensors
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

Contact pressure between the surface of the sensor and the surface of a second object can be measured by a change in capacitance across compressible cells, which comprise the active elements of the sensor. The design allows for the accurate measurement of different pressures at different locations in the area of contact (spatial discrimination), and can be used over a wide range of pressure. As a passive device, it requires external modulation and detection.

Claims

1. A sensor for determining pressures of contact between the surface of said sensor and the surface of an object to be acted on, or from which action is to be received;

wherein said sensor is comprised of regions of capacitance, whose capacitance varies according to force applied to the contact surface of said region;

where capacitance of said region is estabilished, at least in part, by the separation of conducting surfaces;

wherein said seperation is maintained by compression cells, and wherein said compression cells contain only gas and provide means wherein capacitance of said regions varies linearly with external force applied to said region within the mechanical limits of said cell, and wherein said capacitance is measured by external means.

2. A sensor according to claim 1, wherein said conducting surfaces are secured to their respective carriers by any common metal-film deposition technique.

3. A sensor according to claim 2 wherein one said carrier secures conducting surfaces which are interconnected so as to be electrically equivalent, and wherein a common electrical connection is provided from these interconnected conducting surfaces at one or several edge locations on said carrier.

4. A sensor according to claim 2 wherein the second said carrier of said conducting surfaces is made of a thin, flexible, insulating sheet, and wherein said conducting surfaces are electrically unique and wherein every said unique conducting surface is connected by a conducting path to an edge of said flexible sheet;

and wherein said conducting paths are affixed to said sheet in the same manner used to secure said conducting surfaces.

5. A carrier of conducting surfaces according to claim 4, wherein the carrier is provided with corrugations between all adjacent regions bearing said unique conducting surfaces, and wherein said corrugations are sufficient only to allow for the independent operational displacement of said conducting surfaces without any distension of said carrier.

6. A sensor according to claim 3 wherein said compression cells are formed by regularly-spaced hollow contours in a single, contiguous sheet;

wherein said contours have the overall geometry of a frustum of a right circular cone, but whereas the sides thereof are provided with several concentric, bellows-like, pleated folds allowing for increasing or decreasing compression cell height; and

wherein the material comprising said sheet offers minimal mechanical resistance to folding, but which exhibits maximal tensile strength such as is characteristic in certain bi-axially oriented polymers;

wherein said compression cells are completed and sealed when said contoured sheet is bonded to the surface of said carrier of said electrically-equivalent conducting surfaces; and

wherein the spacing of adjacent cells should be greater than twice the cell height.

7. A sensor according to claim 5, wherein said regions of capacitance experience external forces of compression during operation, and wherein force applied to said unique conducting surfaces is mediated through rigid, non-conducting segments;

wherein one such segment is centered over each said unique conducting surface, and wherein said segments cover the entire area of said carrier of said unique conducting surfaces excepting a small spacing between adjacent segments, and wherein the dimension of said spacing is comparable to the lateral measure of said corrugations appearing on said carrier.

8. A sensor according to claim 7 wherein said rigid segments are bonded to a thin, elastic sheet, and wherein said sheet comprises the working surface of said sensor.