TOUCH SENSITIVE ROBOTIC GRIPPER

• US 20130238129A1
• Filed: 03/08/2013
• Published: 09/12/2013
• Est. Priority Date: 03/08/2012
• Status: Active Grant

• Current Assignee: Quality Manufacturing Inc. (Integrated Aerospace Manufacturing LLC)
• Original Assignee: Quality Manufacturing Inc. (Integrated Aerospace Manufacturing LLC)
• Inventors: Rose, Jeffrey A., Rose, James Adam, Rose, Stephen D., Cooper, Raymond
• Granted Patent: US 9,205,567 B2
• Time in Patent Office: Days
• US Class Current: 700/258
• CPC Class Codes: B25J 13/081 Touching devices, e.g. pressure-sensitive
• CPC Class Codes: B25J 15/00 Gripping heads and other end effectors grippers used in machine tools B23Q7/04; gripping members fitted on cranes B66C1/42, B66C1/44; gripping means used in the manufacture of semiconductors H01L21/68707; gripping means used for mounting electrical components H05K13/04
• CPC Class Codes: B25J 18/00 Arms
• CPC Class Codes: B25J 19/0029 arranged within the different robot elements
• CPC Class Codes: B25J 19/005 using batteries, e.g. as a back-up power source
• CPC Class Codes: B25J 19/02 Sensing devices
• CPC Class Codes: B25J 9/1612 characterised by the hand, wrist, grip control
• CPC Class Codes: F04B 9/10 the fluid being liquid
• CPC Class Codes: G01B 7/00 Measuring arrangements characterised by the use of electric or magnetic techniques
• CPC Class Codes: Y10S 901/27 Arm part
• CPC Class Codes: Y10S 901/28 Joint
• CPC Class Codes: Y10T 74/20311 including power cable or connector

Abstract

A displacement measuring cell may be used to measure linear and/or angular displacement. The displacement measuring cell may include movable and stationary electrodes in a conductive fluid. Electrical property measurements may be used to determine how far the movable electrode has moved relative to the stationary electrode. The displacement measuring cell may include pistons and/or flexible walls. The displacement measuring cell may be used in a touch-sensitive robotic gripper. The touch-sensitive robotic gripper may include a plurality of displacement measuring cells mechanically in series and/or parallel. The touch-sensitive robotic gripper may be include a processor and/or memory configured to identify objects based on displacement measurements and/or other measurements. The processor may determine how to manipulate the object based on its identity.

Claims

1. A displacement measuring cell comprising:

a conductive fluid;

a stationary electrode electrically coupled to the conductive fluid;

a movable electrode electrically and physically coupled to the conductive fluid and configured to move relative to the stationary electrode; and

an electrical property measuring device coupled to the movable and stationary electrodes and configured to measure an electrical property dependent on movement of the movable electrode relative to the stationary electrode.

2. The displacement measuring cell of claim 1, wherein the conductive fluid is configured to prevent accumulation of charge between the movable and stationary electrodes.

3. The displacement measuring cell of claim 1, wherein the displacement measuring cell is configured to change a volume of conductive fluid between the stationary and movable electrodes when the movable electrode moves relative to the stationary electrode.

4. The displacement measuring cell of claim 3, wherein the electrical property measuring device is configured to measure changes in an electrical property selected from the group consisting of voltage, current, impedance, and resistance when the volume of conductive fluid changes.

5. The displacement measuring cell of claim 1, wherein the electrical property measuring device is selected from the group consisting of an ohmmeter, an ammeter, a voltmeter, and an analog-to-digital converter.

6. The displacement measuring cell of claim 1, further comprising a processor configured to compute a displacement from an electrical property measurement.

7. The displacement measuring cell of claim 6, wherein the processor is configured to compute at least one of a linear displacement and an angular displacement from the electrical property measurement.

8. The displacement measuring cell of claim 6, wherein the processor is configured to calibrate electrical property measurements to displacements.

9. The displacement measuring cell of claim 1, further comprising a power source, wherein the power source is electrically coupled with the stationary electrode and electrically coupled with the movable electrode.

10. The displacement measuring cell of claim 1, wherein the stationary electrode comprises a flat plate.

11. The displacement measuring cell of claim 1, further comprising a conductive fluid reservoir.

12. The displacement measuring cell of claim 11, further comprising a pressure controller configured to regulate a pressure of the conductive fluid.

13. The displacement measuring cell of claim 1, wherein the conductive fluid is incompressible.

14. The displacement measuring cell of claim 1, wherein the movable electrode is configured to move linearly relative to the stationary electrode.

15. The displacement measuring cell of claim 1, wherein the movable electrode comprises at least one material selected from the group consisting of silver, gallium, conductive ink, and tungsten.

16. The displacement measuring cell of claim 1, wherein the conductive fluid comprises at least one material selected from the group consisting of sodium chloride, potassium chloride, and gallium alloy.

17. The displacement measuring cell of claim 1, wherein the movable electrode is configured to move along a circular path relative to the stationary electrode.

18. The displacement measuring cell of claim 17, further comprising:

a torus-shaped cavity, wherein the torus-shaped cavity contains the circular path;

an end cap, wherein the stationary electrode is coupled to the end cap;

a piston, wherein the movable electrode is coupled to the piston, and wherein the piston and the movable electrode are configured to move along the circular path; and

a bladder coupled to the piston, wherein the bladder is configured to prevent conductive fluid from leaking out of the torus-shaped cavity.

19. The displacement measuring cell of claim 1, further comprising:

an end cap, wherein the stationary electrode is coupled to the end cap;

a piston assembly comprising;

a piston, wherein the movable electrode is coupled to the piston; and

a piston rod, wherein the piston is coupled to a proximal end of the piston rod.

20. The displacement measuring cell of claim 19, wherein the piston comprises a nonconductive material.

21. The displacement measuring cell of claim 19, further comprising a piston extension chamber and a piston retraction chamber.

22. The displacement measuring cell of claim 21, further comprising a pump configured to add additional conductive fluid to the piston extension chamber and remove conductive fluid from the piston retraction chamber.

23. The displacement measuring cell of claim 21, further comprising a pump configured to add additional conductive fluid to the piston retraction chamber and remove conductive fluid from the piston extension chamber.

24. The displacement measuring cell of claim 19, further comprising a contact head coupled to a distal end of the piston rod, wherein the contact head is coupled to a second displacement measuring sensor.

25. The displacement measuring cell of claim 19, further comprising:

a processor configured to control movement of the piston based on computer code stored in a memory; and

an output device configured to output displacement measurements.

26. The displacement measuring cell of claim 19, further comprising:

a piston chamber; and

a positive displacement pump configured to move the piston by adding or removing a quantity of the conductive fluid to the piston chamber, wherein the positive displacement pump is insulated from the conductive fluid.

27. The displacement measuring cell of claim 26, wherein the positive displacement pump comprises plastic to insulate the positive displacement pump from the conductive fluid.

28. The displacement measuring cell of claim 26, further comprising a valve configured to control flow of the conductive fluid to the piston chamber.

29. The displacement measuring cell of claim 19, further comprising a bladder coupled to the piston, wherein the bladder is configured to prevent the conductive fluid from leaking from the displacement measuring cell.

30. The displacement measuring cell of claim 1, further comprising a conformable wall configured to enclose the conductive fluid and the movable and stationary electrodes.

31. The displacement measuring cell of claim 30, further comprising a shear sensor, wherein the conformable wall further comprises a contact surface, wherein the shear sensor is coupled to the contact surface, wherein the shear sensor comprises at least one material selected from the group consisting of a piezoresistive material and a piezoelectric material, wherein the piezoelectric material comprises a polyvinylidene fluoride (PVDF) film, and wherein the shear sensor is perpendicular to the contact surface.

32. The displacement measuring cell of claim 30, wherein the conformable wall comprises silicon.

33. The displacement measuring cell of claim 1, further comprising:

a flexible wall comprising a contact surface;

one or more stationary electrodes in contact with the conductive fluid, wherein the one or more stationary electrodes include the stationary electrode; and

a plurality of movable electrodes coupled to the flexible wall and in contact with the conductive fluid, wherein the plurality of movable electrodes include the movable electrode;

a power source; and

a control circuit configured to selectively couple and decouple the one or more stationary and movable electrodes from the power source.

34. The displacement measuring cell of claim 33, wherein the control circuit comprises a multiplexer.

35. The displacement measuring cell of claim 34, wherein the control circuit is configured to couple at most one of the one or more stationary electrodes and at most one of the plurality of movable electrodes to the power source at any time.

36. The displacement measuring cell of claim 35, wherein the control circuit is configured to enable only directly opposing stationary and movable electrodes at the same time.

37. The displacement measuring cell of claim 33, wherein the control circuit comprises a plurality of transistors corresponding to the plurality of movable electrodes, wherein the source of each transistor is electrically coupled with the power source and the drain of each transistor is electrically coupled with the corresponding movable electrode.

38. The displacement measuring cell of claim 33, further comprising an integrated circuit embedded in the flexible wall, wherein the integrated circuit comprises at least one of the electrical property measuring device, the control circuit, a multiplexer, and a transistor, and wherein the flexible wall comprises a flexible printed circuit board.

39. The displacement measuring cell of claim 38, wherein the integrated circuit comprises carbon nanotubes.

40. The displacement measuring cell of claim 33, wherein the plurality of movable electrodes are embedded in the flexible wall.

41. The displacement measuring cell of claim 40, wherein the plurality of movable electrodes comprise microfluidic channels to enhance electrical coupling with the conductive fluid.

42. The displacement measuring cell of claim 1, further comprising a temperature sensor to measure the temperature of the conductive fluid.

43. The displacement measuring cell of claim 42, wherein the temperature sensor is in contact with at least one of a reservoir, a hydraulic line, the movable electrode, the stationary electrode, a chamber containing the movable and stationary electrodes, and a portion of the chamber adjacent to a contact surface.

44. The displacement measuring cell of claim 1, further comprising a shear sensor selected from the group consisting of a piezoresistive sensor and a polyvinylidene fluoride (PVDF) film sensor, wherein the shear sensor is perpendicular to the movable electrode.

45. A touch-sensitive robotic gripping system comprising:

a first gripping member comprising a first plurality of displacement measuring cells, each displacement measuring cell comprising;

a conductive fluid,

a stationary electrode electrically coupled to the conductive fluid, and

a movable electrode electrically coupled to the conductive fluid and configured to move relative to the stationary electrode; and

a first electrical property measuring device configured to measure a first electrical property while selectively coupled to the stationary electrode and the movable electrode of a selected displacement measuring cell, wherein the first electrical property depends on movement of the movable electrode relative to the stationary electrode.

46. The touch-sensitive robotic gripping system of claim 45, further comprising:

a processor configured to receive measurements of the first electrical property and generate a model of an object being sensed by the first plurality of displacement measuring cells; and

a memory in electrical communication with the processor and configured to store the measurements.

47. The touch-sensitive robotic gripping system of claim 46, wherein the processor is configured to generate the model of the object by:

determining maximum and minimum extension positions during a calibration process; and

computing a plurality of differential volumes based on;

differences between current movable electrode positions computed from the received measurements and the maximum or the minimum extension positions; and

an electrode area of each movable electrode.

48. The touch-sensitive robotic gripping system of claim 47, wherein the processor is configured to generate a three dimensional model of the object by assembling the plurality of differential volumes into the three dimensional model based on known positions of the first plurality of displacement measuring cells.

49. The touch-sensitive robotic gripping system of claim 46, wherein the processor is configured to:

determine a perimeter of the object from the received measurements; and

generate a three dimensional representation of the object from the determined perimeter.

50. The touch-sensitive robotic gripping system of claim 46, wherein the memory is configured to store a diagram of the object.

51. The touch-sensitive robotic gripping system of claim 50, wherein the processor determines at least one of an orientation and a location of the object being sensed by the first plurality of displacement measuring cells by comparing the model of the object to the diagram of the object.

52. The touch-sensitive robotic gripping system of claim 51, further comprising a plurality of servo motors, wherein the plurality of servo motors control movement of the first gripping member and a second gripping member and the processor instructs the plurality of servo motors to change the orientation of the object so a manufacturing operation may be performed.

53. The touch-sensitive robotic gripping system of claim 52, wherein the processor instructs the plurality of servo motors to change the orientation of the object to match a predetermined orientation.

54. The touch-sensitive robotic gripping system of claim 46, wherein the processor moves the first gripping member relative to a second gripping member such that the stationary electrode does not touch the movable electrode.

55. The touch-sensitive robotic gripping system of claim 45, wherein the first plurality of displacement measuring cells is configured in a plurality of layers, wherein the plurality of layers are mechanically in series with each other, and wherein displacement measuring cells within each layer are mechanically in parallel with each other.

56. The touch-sensitive robotic gripping system of claim 55, wherein the plurality of layers comprises a final layer comprising pistonless displacement measuring cells comprising flexible walls, and wherein each layer other than the final layer comprises displacement measuring cells comprising pistons.

57. The touch-sensitive robotic gripping system of claim 45, further comprising a pressure monitoring device configured to measure a pressure of the conductive fluid.

58. The touch-sensitive robotic gripping system of claim 57, further comprising a processor configured to move the first gripping member relative to a second gripping member based on at least one of a pressure measurement and a first electrical property measurement.

59. The touch-sensitive robotic gripping system of claim 45, further comprising a second gripping member, a third gripping member, and a fourth gripping member, wherein the first gripping member is disposed opposite the second gripping member, the third gripping member is disposed opposite the fourth gripping member, and the first gripping member is perpendicular to the third gripping member.

60. The touch-sensitive robotic gripping system of claim 45, further comprising:

a second gripping member comprising a second plurality of displacement measuring cells, each displacement measuring cell in the second plurality of displacement measuring cells comprising;

a conductive fluid,

a stationary electrode electrically coupled to the conductive fluid, and

a movable electrode electrically coupled to the conductive fluid; and

a second electrical property measuring device configured to measure a second electrical property of an object being sensed while coupled to movable electrodes in at least two different displacement measuring cells.

61. The touch-sensitive robotic gripping system of claim 60, wherein the second electrical property measuring device is configured to measure a capacitance of the object.

62. The touch-sensitive robotic gripping system of claim 61, further comprising a processor configured to compute a dielectric constant and/or permittivity of the object.

63. The touch-sensitive robotic gripping system of claim 62, further comprising a memory configured to store dielectric values and/or permittivity values for one or more materials, wherein the processor is further configured to determine a material of the object by comparing the dielectric constant and/or permittivity of the object to the stored dielectric values and/or permittivity values.

64. The touch-sensitive robotic gripping system of claim 62, wherein the second electrical property measuring device is further configured to be calibrated by measuring a capacitance without the object between the movable electrodes.

65. The touch-sensitive robotic gripping system of claim 61, wherein the second electrical property measuring device is configured to measure a plurality of capacitances while electrical power is applied at a corresponding plurality of frequencies and/or amplitudes.

66. The touch-sensitive robotic gripping system of claim 60, wherein the second electrical property measuring device is configured to measure a dissipation factor.

67. The touch-sensitive robotic gripping system of claim 60, wherein the second electrical property measuring device is configured to measure resistivity.

68. The touch-sensitive robotic gripping system of claim 60, further comprising a strain gauge, wherein the strain gauge comprises a beam comprising a length-sensitive electrical resistor.

69. The touch-sensitive robotic gripping system of claim 60, further comprising an electrical motor and a lead screw, wherein the electrical motor and the lead screw are configured to move the second gripping member.

70. The touch-sensitive robotic gripping system of claim 60, further comprising a quick-change turret to perform one or more operations on the object.

71. The touch-sensitive robotic gripping system of claim 70, wherein the quick-change turret determines which operation to perform based on at least one of the first electrical property and the second electrical property.

72. The touch-sensitive robotic gripping system of claim 70, wherein the quick-change turret comprises a rotary joint.

73. The touch-sensitive robotic gripping system of claim 60, further comprising a cam guide configured to move the second gripping member.

74. The touch-sensitive robotic gripping system of claim 45, further comprising:

a second gripping member comprising a second plurality of displacement measuring cells, each displacement measuring cell in the second plurality of displacement measuring cells comprising;

a conductive fluid,

a stationary electrode electrically coupled to the conductive fluid, and

a movable electrode electrically coupled to the conductive fluid,

wherein each displacement measuring cell in the first and second pluralities of displacement measuring cells further comprises;

a wall enclosing the conductive fluid, the stationary electrode, and the movable electrode; and

an external electrode attached to an outside of the wall; and

a second electrical property measuring device configured to measure a second electrical property of the object while coupled to external electrodes in at least two different displacement measuring cells.

75. The touch-sensitive robotic gripping system of claim 74, wherein the second electrical property measuring device is configured to measure resistance.

76. The touch-sensitive robotic gripping system of claim 75, further comprising a processor configured to compute a resistivity of the object.

77. The touch-sensitive robotic gripping system of claim 76, further comprising a memory configured to store resistivity values for one or more materials, wherein the processor is further configured to determine a material of the object by comparing the resistivity of the object to the stored resistivity values.

78. The touch-sensitive robotic gripping system of claim 76, wherein the second electrical property measuring device is further configured to be calibrated by measuring a resistance without the object between the first external electrode and the second external electrode.

79. The touch-sensitive robotic gripping system of claim 45, wherein the first gripping member comprises a foot comprising:

the first plurality of displacement measuring cells;

a pressure sensor configured to measure a fluid pressure of the conductive fluid;

one or more shear sensors configured to measure a shear force against a bottom of the foot; and

a processor configured to determine at least one of a robot weight and a robot load from at least one of the fluid pressure and a plurality of displacement measurements from the first plurality of displacement measuring cells,

wherein the first plurality of displacement measuring cells are configured to support the foot and measure the contour of the ground.

80. A method of gripping an object using a touch-sensitive robotic gripper, the method comprising:

providing a first gripping member comprising a plurality of layers including one or more non-final layers and a final layer configured to contact the object, each layer comprising one or more displacement measuring cells, each displacement measuring cell in each layer comprising;

a conductive fluid,

a stationary electrode in contact with the conductive fluid, and

a movable electrode in contact with the conductive fluid,

wherein each displacement measuring cell in the one or more non-final layers comprises a piston assembly comprising;

a piston, wherein the movable electrode is coupled to the piston,

a piston rod, wherein a proximal end of the piston rod is coupled to the piston, and

a contact head, wherein the contact head is coupled to a distal end of the piston rod;

retracting each piston to a minimum extension position;

extending the piston in each displacement measuring cell in each non-final layer until the conductive fluid reaches a predetermined pressure; and

calculating a total distance travelled for each displacement measuring cell in the final layer, wherein the total distance travelled for a particular displacement measuring cell is a distance travelled by the movable electrode in the particular displacement measuring cell plus distances travelled by movable electrodes in displacement measuring cells mechanically in series with the particular displacement measuring cell.

81. The method of claim 80, wherein extending the piston in each displacement measuring cell comprises extending the piston in each displacement measuring cell in each non-final layer simultaneously.

82. The method of claim 81, wherein extending the piston in each displacement measuring cell comprises extending the piston in each displacement measuring cell with a common pump and a common control valve.

83. The method of claim 82, wherein extending the piston in each displacement measuring cell with a common pump comprises controlling the common pump based on measurements from pressure sensors hydraulically coupled to the pump.

84. The method of claim 80, wherein extending the piston in each displacement measuring cell comprises extending the piston in each displacement measuring cell in each non-final layer until the conductive fluid reaches a predetermined pressure once each piston in a preceding layer has finished extending.

85. The method of claim 80, further comprising initial calibrating steps of:

providing a second gripping member;

retracting each piston to the minimum extension position;

extending each piston until each contact head in the final layer touches the second gripping member to obtain a maximum extension position; and

mapping the minimum and maximum extension positions to displacements.

86. The method of claim 85, wherein mapping comprises associating measurements of an electrical characteristic with the minimum and maximum extension positions.

87. The method of claim 86, wherein the electrical characteristic is selected from the group consisting of a voltage, a current, an impedance, and a resistance.

88. The method of claim 85, wherein mapping the minimum and maximum extension positions to displacements comprises mapping the minimum and maximum extension positions to discrete values, and wherein a minimum discrete increment corresponds to a desired displacement measurement resolution.

89. The method of claim 85, wherein mapping the minimum and maximum extension positions to displacements comprises defining a function or curve mapping electrical property measurements to displacements.

90. The method of claim 89, wherein the function or curve is configured to receive a temperature measurement as input and output a temperature-corrected displacement.

91. The method of claim 80, wherein retracting each piston comprises adding conductive fluid to a piston retraction chamber.

92-142. -142. (canceled)