ENHANCEMENTS TO IMPROVE THE FUNCTION OF A BIOMIMETIC TACTILE SENSOR

• US 20090272201A1
• Filed: 04/02/2009
• Published: 11/05/2009
• Est. Priority Date: 03/28/2007
• Status: Active Grant

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Lin, Chia Hsien (Gary), Santos, Veronica J., Loeb, Gerald E., Wettels, Nicholas, Peck, Raymond, Fishel, Jeremy
• Granted Patent: US 8,272,278 B2
• Time in Patent Office: Days
• US Class Current: 73/862.41
• CPC Class Codes: G01L 5/228 using tactile array force sensors

Abstract

Tactile sensors are disclosed that mimic the human fingertip and its touch receptors. The mechanical components are similar to a fingertip, with a rigid core surrounded by a weakly conductive fluid contained within an elastomeric skin. The deformable properties of the finger pad can be used as part of a transduction process. Multiple electrodes can be mounted on the surface of the rigid core and connected to impedance measuring circuitry within the core. External forces deform the fluid path around the electrodes, resulting in a distributed pattern of impedance changes containing information about those forces and the objects that applied them. Strategies are described for extracting features related to the mechanical inputs and using this information for reflexive grip control. Controlling grip force in a prosthetic having sensory feedback information is described. Techniques are described for enhancing the useful force range for impedance sensors by internally texturing the elastomeric skin.

Claims

1. A biomimetic tactile sensor system comprising:

a rigid core having a surface and a plurality of electrodes disposed on the surface, wherein the electrodes are configured and arranged to detect impedance changes of a fluid;

an elastomeric skin surrounding at least a portion of the core and having an inner and outer surface, and configured and arranged to form a space for confining a fluid between the surface of the core and the inner surface;

a temperature sensor configured and arranged to detect a temperature of the surface of the rigid core; and

detection circuitry configured and arranged to (i) detect changes in electrical impedance of the fluid between at least one of the electrodes caused by force that is exerted on the elastomeric skin, and (ii) sense temperature associated with the temperature sensor.

2. The system of claim 1, wherein the detection circuitry is configured and arranged to provide as an output a control signal for position and/or force based on the detected changes in impedance.

3. The system of claim 1, further comprising a fluid disposed within the space, wherein the fluid comprises an electrically conductive liquid

4. The system of claim 1, wherein the temperature sensor comprises a thermistor.

5. The system of claim 1, further comprising electronic means for heating the sensor above ambient temperature.

6. The system of claim 5, wherein the electronic means for heating include a microprocessor configured and arranged to have power dissipation be controlled by software.

7. The system of claim 5, wherein the temperature sensor is used for control of the electronic means for heating the sensor.

8. The system of claim 1, wherein the temperature sensor is used to monitor temperature changes resulting from contact between the sensor system and an external object or surface.

9. A biomimetic tactile sensor system comprising:

a rigid core having a surface and a plurality of electrodes disposed on the surface, wherein the electrodes are configured and arranged to detect impedance changes of a fluid;

an elastomeric skin surrounding at least a portion of the core and having an inner and outer surface, and configured and arranged to form a space for confining a fluid between the surface of the core and the inner surface, wherein the inner surface of the skin comprises a plurality of asperities; and

detection circuitry configured and arranged to detect changes in electrical impedance of the fluid between at least one of the electrodes caused by force that is exerted on the elastomeric skin.

10. The system of claim 9, wherein the detection circuitry is configured and arranged to provide as an output a control signal for controlling position and/or force based on the detected changes in impedance.

11. The system of claim 9, further comprising a fluid disposed within the space, wherein the fluid comprises an electrically conductive liquid

12. The system of claim 9, wherein the asperities comprise a repeated pattern.

13. The system of claim 9, wherein the asperities comprise pyramidal protrusions from the inner surface of the skin.

14. The system of claim 9, wherein the asperities comprise columnar protrusions from the inner surface of the skin.

15. The system of claim 9, wherein the asperities are cylindrical asperities.

16. The system of claim 15, wherein the asperities are about 0.25 mm tall and 0.25 mm in diameter.

17. The system of claim 16, wherein the asperities are about 0.5 mm apart and are configured and arranged in a regular square grid pattern.

18. The sensor of claim 9, wherein the elastomeric skin comprises silicone or polyurethane.

19. The sensor of claim 9, wherein the elastomeric skin includes bumps or ridges on the outer surface.

20. A biomimetic tactile sensor system comprising:

a rigid core having a surface;

an elastomeric skin surrounding at least a portion of the core and having an inner and outer surface, and configured and arranged to form a space for confining a fluid between the surface of the core and the inner surface;

one or more sensors configured and arranged to detect a physical characteristic of the fluid within the sensor system;

a collar seal for sealing the skin against the core in a fluid tight configuration.

21. The system of claim 20, further comprising a fluid disposed within the space, wherein the fluid comprises an electrically conductive liquid.

22. The system of claim 20, further comprising an inflation port disposed within the skin.

23. The system of claim 20, wherein the collar seal comprises a self-compressing edge seal that is molded as an integral part of the skin for simplifying removal and replacement of the skin for field service.

24. The system of claim 23, wherein the collar seal further comprises a groove configured and arranged around a circumference of a portion of the core.

25. A biomimetic tactile sensor system comprising:

a rigid core having a surface;

an elastomeric skin surrounding at least a portion of the core and having an inner and outer surface, and configured and arranged to form a space for confining a fluid between the surface of the core and the inner surface;

one or more sensors configured and arranged to detect a physical characteristic of the fluid within the sensor system; and

a resealable inflation port disposed within the skin for filling the space with fluid.

26. The system of claim 25, further comprising conditioning circuitry configured and arranged to receive and condition electrical signals received from the one or more sensors.

27. The system of claim 25, further comprising a fluid disposed within the space, wherein the fluid comprises an electrically conductive liquid.

28. The system of claim 25, wherein the resealable inflation port comprises a plate with an aperture for receiving a needle.

29. The system of claim 28, wherein the resealable inflation port comprises a thickened portion of the skin corresponding to the location of the plate, wherein when the plate is secured to the skin, compressive forces exist in the thickened portion.

30. The system of claim 28, wherein either or both of the plate and core include one or more rigid surfaces that are angled for producing resultant forces within the thickened portion of skin producing compression perpendicular to an axis of a needle inserted through the skin for filling the space.