Biomimetic tactile sensor for control of grip

• US 7,878,075 B2
• Filed: 05/16/2008
• Issued: 02/01/2011
• Est. Priority Date: 05/18/2007
• Status: Active Grant

• Current Assignee: University of Southern California
• Original Assignee: University of Southern California
• Inventors: Santos, Veronica J., Popovic, Djordje, Wettels, Nicholas, Johansson, Roland S., Loeb, Gerald E.
• Primary Examiner(s): Caputo; Lisa M
• Assistant Examiner(s): DAVIS, OCTAVIA L
• Application Number:
  US12/122,569
• Publication Number:
  US 20090133508A1
• Time in Patent Office: 991 Days
• Field of Search: 73862041-862046
• US Class Current: 73/862.046
• CPC Class Codes: B25J 13/084 Tactile sensors in general G01L5/16, G01L5/22
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: G01L 5/228 using tactile array force sensors

Abstract

Disclosed is a robust tactile sensor array that mimics 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. It uses the deformable properties of the finger pad as part of the transduction process. Multiple electrodes are 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 for extracting features related to the mechanical inputs and using this information for reflexive grip control.

Claims

1. A biomimetic tactile sensor system comprising:

a biomimetic tactile sensor comprising;

a deformation sensor comprising;

a rigid core having a substantially convex surface;

an elastic covering attached to the rigid core and substantially surrounding the surface;

a multiplicity of electrodes on the surface of the rigid core; and

a weakly conductive fluid between the electrodes and the elastic covering; and

a controller configured to control movement of a prosthetic hand or robotic manipulator that is attached to the biomimetic tactile sensor in response to contact between the biomimetic tactile sensor and an external object in a manner at least partially comparable to the way in which a human brain would control the movement of a human fingertip in response to contact between the human fingertip and the external object.

2. The biomimetic tactile sensor system of claim 1 wherein the biomimetic tactile sensor further comprises a pressure transducer in contact with the weakly conductive fluid which is configured to sense vibration of the elastic covering as it slides over a surface of the external object that propagates through the deformable liquid material to the pressure transducer.

3. The biomimetic tactile sensor system of claim 2 wherein the controller is configured to determine changes in the volume of the weakly conductive fluid between the rigid core and the elastic covering based on information from the pressure transducer.

4. The biomimetic tactile sensor system of claim 2 wherein the outer surface of the elastic covering has a pattern of ridges that are configured to enhance the vibration of the elastic covering as it slides over the surface.

5. The biomimetic tactile sensor system of claim 2 wherein the controller is configured to infer a texture property of the surface of the object based on the vibration sensed by the pressure transducer as the elastic covering slides over the external object.

6. The biomimetic tactile sensor system of claim 1 wherein the biomimetic tactile sensor includes a temperature sensor.

7. The biomimetic tactile sensor system of claim 6 including a heating element configured to heat the rigid core.

8. The biomimetic tactile sensor system of claim 6 wherein the deformation sensor has a temperature dependency and wherein the controller is configured to correct for the temperature dependency of the deformation sensor based on a temperature measured by the temperature sensor.

9. The biomimetic tactile sensor system of claim 6 wherein the controller is configured to infer a thermal property of the external object from a time course of temperature measurements made by the temperature sensor.

10. The biomimetic tactile sensor system of claim 1 wherein the controller is configured to control the movement of the prosthetic hand or robotic manipulator in a manner that increases information about the external object that can be extracted from the biomimetic tactile sensor.

11. The biomimetic tactile sensor system of claim 1 wherein the deformation sensor is configured to sense deformation by sensing changes in the electrical resistance in a circuit that includes at least one of the electrodes and the weakly conductive fluid.

12. The biomimetic tactile sensor of claim 1 wherein the deformation sensor is configured to combine and convert signals from all of the electrodes into a single, serial digital output.

13. The biomimetic tactile sensor system of claim 1 wherein the controller is configured to formulate a hypothesis about properties of the object based on information from the biomimetic tactile sensor.

14. The biomimetic tactile sensor system of claim 13 wherein the controller is configured to test the hypothesis by directing a subsequent exploratory movement of the prosthetic hand or robotic manipulator and comparing information from the biomimetic tactile sensor resulting from the exploratory movement to information which would be expected from the biomimetic tactile sensor if the hypothesis is correct.

15. The biomimetic tactile sensor system of claim 1 wherein the controller is configured to determine the hardness of the object based on information from the deformation sensor and information about the relative velocity of motion between the deformation sensor and the object.

16. The biomimetic tactile sensor system of claim 1 further comprising a neural network configured to process information from the biomimetic tactile sensor.

17. The biomimetic tactile sensor system of claim 16 wherein the neural network is configured to provide an estimate of the location, magnitude and direction of force asserted by the external object against the elastic covering based on the information.

18. The biomimetic tactile sensor system of claim 16 wherein the neural network is configured to produce information indicative of an adjustment to a grip force to be asserted by the prosthetic hand or robot manipulator based on the estimate of the location, magnitude and/or direction of the force.

19. The biomimetic tactile sensor system of claim 1 wherein the movement is an exploratory movement to determine the identity or nature of the object and the controller is configured to adjust the exploratory movement according to information from the deformation sensor.

20. The biomimetic tactile sensor system of claim 1 wherein the movement control which the controller is configured to provide includes controlling the force with which the prosthetic hand or the robotic manipulator grips the external object.

21. A biomimetic tactile sensor system comprising:

a biomimetic tactile sensor comprising;

a deformation sensor comprising;

a rigid core having a substantially convex surface;

an elastic covering attached to the rigid core and substantially surrounding the surface;

a multiplicity of electrodes on the surface of the rigid core; and

a weakly conductive fluid between the electrodes and the elastic covering; and

a pressure transducer in contact with the weakly conductive fluid which is configured to sense pressure asserted by the weakly conductive fluid; and

a controller configured to control movement of a prosthetic hand or robotic manipulator that is attached to the biomimetic tactile sensor in response to contact between the biomimetic tactile sensor and an external object based on information from the deformation sensor and the pressure transducer.

22. The biomimetic tactile sensor system of claim 21 wherein the controller is configured to infer texture properties of a surface on the external object which contacts the elastic covering based on vibration detected by the pressure transducer.

23. The biomimetic tactile sensor system of claim 21 wherein the controller is configured to detect slippage between the external object and the biomimetic tactile sensor based on information from the pressure transducer.

24. The biomimetic tactile sensor system of claim 21 wherein the controller is configured to control the force with which the prosthetic hand or the robotic manipulator grips the external object.

25. The biomimetic tactile sensor system of claim 21 wherein the movement control which the controller is configured to provide includes exploratory movements to identify properties of the external object.

26. A biomimetic tactile sensor system comprising:

a biomimetic tactile sensor comprising;

a deformation sensor comprising;

a rigid core having a substantially convex surface;

an elastic covering attached to the rigid core and substantially surrounding the surface;

a multiplicity of electrodes on the surface of the rigid core; and

a weakly conductive fluid between the electrodes and the elastic covering; and

a temperature sensor; and

a controller configured to control movement of a prosthetic hand or robotic manipulator that is attached to the biomimetic tactile sensor in response to contact between the biomimetic tactile sensor and an external object based on information from the deformation sensor and the temperature sensor.

27. The biomimetic tactile sensor system of claim 26 wherein the movement control which the controller is configured to provide includes exploratory movements to identify properties of the external object.

28. The biomimetic tactile sensor system of claim 27 wherein the controller is configured to infer thermal properties of the external object from a time course of temperature measurements made by the temperature sensor.

29. The biomimetic tactile sensor system of claim 26 including a heating element configured to heat the rigid core.

30. The biomimetic tactile sensor system of claim 26 wherein the deformation sensor has a temperature dependency and wherein the controller is configured to correct for the temperature dependency of the deformation sensor based on a temperature measured by the temperature sensor.