Compact dexterous robotic hand

• US 6,244,644 B1
• Filed: 01/25/1999
• Issued: 06/12/2001
• Est. Priority Date: 01/25/1999
• Status: Expired due to Fees

• Current Assignee: National Aeronautics and Space Administration US Government As Represented By The Administrator of The, US Government As Represented By The Director National Security Agency
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Diftler, Myron A., Lovchik, Christopher Scott
• Primary Examiner(s): Kramer, Dean J.
• Application Number:
  US09/236,965
• Time in Patent Office: 869 Days
• Field of Search: 294/106, 294/111, 294/907, 414/7, 901/29, 901/31-33, 901/36, 901/39, 901/45, 901/46, 901/49, 623/57, 623/61-65
• US Class Current: 294/111
• CPC Class Codes: B25J 15/0009 comprising multi-articulated fingers, e.g. resembling a human hand
• CPC Class Codes: B25J 15/10 with three or more finger members B25J15/0009 takes precedence
• CPC Class Codes: B25J 9/104 with cables, chains or ribbons
• CPC Class Codes: Y10S 294/907 Sensor controlled device

Abstract

A compact robotic hand 10 includes a palm housing 16, a wrist section 12 and a forearm section 16. The palm housing supports a plurality of fingers 18, 20, 22 and one or more movable palm members 24, 25 that cooperate with the fingers to grasp and/or release an object. Each flexible finger 18, 20, 22 comprises a plurality of hingedly connected segments, including a proximal segment 16 pivotally connected to the palm housing. The proximal finger segment 16 includes at least one groove 122 defining first and second cam surfaces 126, 128 for engagement with a cable 60. A plurality of lead screw assemblies 54 each carried by the palm housing are supplied with power from a flexible shaft 92 rotated by an actuator 91, and output linear motion to a cable 60 move a finger. The cable 60 is secured within a respective groove 122 and enables each finger to move between an opened and closed position. A decoupling assembly 288 pivotally connected to a proximal finger segment enables a cable 60 connected thereto to control movement of an intermediate and distal finger segment independent of movement of the proximal finger segment. The dexterous robotic hand closely resembles the function of a human hand yet is light weight and capable of grasping both heavy and light objects with a high degree of precision.

Claims

1. A dexterous robotic hand, comprising:

a palm housing;

a plurality of flexible fingers each movably secured to the palm housing, each finger including a plurality of hingedly connected segments, at least one segment of each finger operatively connected to another segment of the same finger;

a groove disposed in a proximal segment of each finger, each groove having a first curvilinear cam surface and a second curvilinear cam surface, the first curvilinear cam surface having a first area of curvature and the second curvilinear cam surface having a second area of curvature, the second curvilinear cam surface being opposite the first area of curvature relative to the first curvilinear cam surface and the first curvilinear cam surface being opposite the second area of curvature relative to the second curvilinear cam surface, the proximal segment being pivotally movable with respect to the palm housing such that the finger may move relative to the palm housing in a direction of at least one degree of freedom between an opened and a closed position;

a plurality of lead screw assemblies each supported on the palm housing, each lead screw assembly including a cable end and a coupling end;

a plurality of cables each secured within a respective groove such that the cable contacts the first curvilinear surface to move the flexible finger to a closed position and the cable contacts the second curvilinear surface to move the flexible finger to an open position; and

a plurality of finger actuators each operatively connected to a coupling end for actuating a respective cable to move a respective finger between the opened and closed positions.

2. The robotic hand as defined in claim 1, wherein the first and second curvilinear cam surfaces maintain a substantially constant lever arm for moving the respective finger relative to the palm housing in response to movement of a respective cable and independent of the position of the finger respective relative to the palm housing.

3. The robotic hand as defined in claim 1, wherein the cable rigidly biases the respective finger to a selected position when the cable engages one of the first and second cam surfaces.

4. The robotic hand of claim 1, wherein each lead screw assembly comprises:

a tubular sleeve having a sleeve axis;

a body movably mounted at least partially within the tubular sleeve for movement relative to the tubular sleeve along the sleeve axis, the body including a distal end for interconnection with the cable and a proximal end; and

a lead screw disposed at least partially within the tubular sleeve, the lead screw having a proximal end threadably connected to the proximal end of the body and a distal end rotatably mounted within the coupling end such that rotation of the lead screw produces movement of the body and at least a portion of the cable along the sleeve axis.

5. The robotic hand of claim 1, further comprising:

a forearm section for housing the plurality of finger actuators;

a wrist cuff pivotally attached to the palm housing and pivotally attached to the forearm section, the wrist cuff having a through opening therein;

a first and a second shock loader each positioned within the forearm section and attached to the wrist cuff for mitigating stress exerted on the hand; and

a first and a second wrist actuator each operatively connected to the palm housing for transmitting pivotal movement to the palm housing relative to the forearm section in directions having at least two degrees of freedom defined by the pivotal connection of the wrist cuff to the forearm section and the pivotal connection of the palm housing to the wrist cuff.

6. The robotic hand of claim 5, further comprising:

a plurality of segment sensors each for sensing a relative position of a respective segment of a finger; and

a plurality of wrist sensors for sensing a position of the palm housing relative to the forearm section.

7. The robotic hand of claim 5, further comprising:

a plurality of lead screw sensors each attached to a respective one of the plurality of lead screw assemblies for sensing stress on a respective finger upon grasping an object; and

a wrist gauge positioned between one of a respective first and second wrist actuator and the palm housing for sensing stress on the palm housing upon grasping an object.

8. The robotic hand of claim 1, further comprising:

a forearm section for housing the plurality of finger actuators;

a wrist cuff pivotally attached to the palm housing and pivotally attached to the forearm section, the wrist cuff having a through opening therein; and

a plurality of flexible shafts each passing through the through opening in the wrist cuff and having a first end connected to a respective finger actuator and a second end connected to a respective coupling end of a lead screw assembly for transmitting rotational movement from a respective finger actuator to a respective lead screw assembly.

9. The robotic hand of claim 1, wherein the plurality of flexible fingers comprises:

a dexterous finger, a grasping finger and a thumb each movably secured to the palm housing;

the grasping finger being positioned opposite the thumb relative to the dexterous finger; and

the thumb being pivotally connected to the palm housing at a position spaced from a plane of the pivotal connection of the dexterous finger and the grasping finger with the palm housing.

10. The robotic hand of claim 9, wherein the plurality of hingedly connected segments on the grasping finger comprises:

the proximal segment, an intermediate segment and a distal segment, the proximal, intermediate and distal segments being pivotally linked such that the intermediate and distal segments simultaneously bend as a function of the bending of the proximal segment.

11. The robotic hand of claim 9, wherein the plurality of hingedly connected segments on the dexterous finger comprises:

the proximal segment, an intermediate segment and a distal segment, the intermediate segment being pivotally linked to a decoupling assembly such that the intermediate and distal segment bend independent of the proximal segments.

12. The robotic hand of claim 11, wherein the plurality of hingedly connected segments on the thumb comprises:

the proximal segment and a distal segment, the distal segment being pivotally linked to a decoupling assembly such that the distal segment bends independent of the proximal segment.

13. The robotic hand of claim 11, further comprising:

a plurality of yokes each positioned between the palm housing and a respective proximal segment of a dexterous finger, each proximal segment being pivotally moveable with respect to the palm housing such that the proximal segment of the dexterous finger independently moves in directions having at least two degrees of freedom;

another groove disposed in the proximal segment of each dexterous finger, the another groove and the groove being spaced on opposite sides of a centerline of the yoke to achieve yaw movement, the another groove having another first curvilinear cam surface and another second curvilinear cam surface, the another first curvilinear surface having an another first area of curvature and the another second curvilinear cam surface having an another second area of curvature, the another second curvilinear cam surface being opposite the another first area of curvature relative to the another first curvilinear cam surface and the another first curvilinear cam surface being opposite the another second area of curvature relative to the second curvilinear cam surface;

a plurality of another lead screw assemblies each supported on the palm housing, each another lead screw assembly including another cable end and another coupling end;

a plurality of another cables are secured within a respective another groove; and

a plurality of another actuators each operatively connected to the another coupling end of a respective another lead screw assembly for actuating a respective another cable to move the proximal segment of the dexterous finger in directions having at least two degrees of freedom.

14. The robotic hand of claim 1, further comprising:

a decoupling lead screw assembly supported by the palm housing, the decoupling lead screw assembly including a cable end and a coupling end;

a decoupling mechanism powered by the decoupling lead screw assembly for controlling movement of a finger segment independent of movement of the proximal segment of the respective finger;

a decoupling flexible cable secured to the decoupling lead screw assembly; and

a decoupling actuator operatively connected to the coupling end of the decoupling lead screw assembly for actuating the decoupling flexible cable.

15. The robotic hand of claim 1, further comprising:

a palm member including a first end hingedly connected to the palm housing and a second end for supporting at least one of the plurality of fingers;

a palm lead screw assembly carried by the palm housing, the palm lead screw assembly including a cable end and a coupling end;

a cable secured to the palm member and the cable end of the palm lead screw assembly; and

a palm actuator operatively secured to the coupling end of the palm lead screw assembly for actuating the cable and moving the palm member towards a closed position.

16. The robotic hand of claim 1, further comprising:

a plurality of shock mounts each positioned between the palm housing and a respective finger for mitigating stress transmitted through the respective finger.

17. The robotic hand of claim 1, further comprising:

a plurality of springs each connected to at least one of the plurality of hingedly connected segments of a respective finger for biasing the respective finger towards the opened position.

18. A dexterous robotic hand, comprising:

a palm housing;

a plurality of fingers each movably secured to the palm housing, each finger including a plurality of hingedly connected segments, at least one segment of each finger operatively connected to another segment of the same finger by a pivoting link for transmitting movement to the at least one segment, each finger being pivotally moveable with respect to the palm housing such that each finger may independently move in a direction having at least one degree of freedom between an opened and a closed position;

a palm member including a first end hingedly connected to the palm housing and a second end for supporting at least one of the plurality of fingers;

a plurality of finger lead screw assemblies each supported on the palm housing, each finger lead screw assembly including a cable end and a coupling end;

a plurality of cables each secured to a respective finger;

a plurality of finger actuators each operatively connected to the coupling end of a respective finger lead screw assembly for actuating a respective cable and moving a respective finger between the opened and closed position;

a palm lead screw assembly supported on the palm housing; and

a palm actuator operatively connected to the palm lead screw assembly for moving the palm member relative to the palm housing.

19. The robotic hand of claim 18, wherein each of the plurality of finger lead screw assemblies comprises:

a tubular sleeve having a sleeve axis;

a body movably mounted at least partially within the tubular sleeve for movement relative to the tubular sleeve along the sleeve axis, the body including a distal end for interconnection with the cable and a proximal end; and

a lead screw disposed at least partially within the tubular sleeve, the lead screw having a proximal end threadably connected to the proximal end of the body and a distal end rotatably mounted within the coupling end such that rotation of the lead screw produces movement of the body and at least a portion of the cable along the sleeve axis.

20. The robotic hand of claim 18, further comprising:

a plurality of shock mounts each positioned between the palm housing and a respective finger for mitigating stress transmitted through the respective finger.

21. The robotic hand of claim 18, further comprising:

a forearm section for housing the plurality of finger actuators;

a wrist cuff pivotally attached to the palm housing and pivotally attached to the forearm section, the wrist cuff having a through opening therein;

a first and a second shock loader each positioned within the forearm section and attached to the wrist cuff for mitigating stress exerted on the hand; and

a first and a second wrist actuator operatively connected to the palm housing for transmitting pivotal movement to the palm housing relative to the forearm section in directions having at least two degrees of freedom defined by the pivotal connection of the wrist cuff to the forearm section and the pivotal connection of the palm housing to the wrist cuff.

22. The robotic hand of claim 21, further comprising:

a plurality of flexible shafts each passing through the through opening in the wrist cuff and having a first end connected to a respective finger actuator and a second end connected to a respective coupling end of a lead screw assembly for transmitting rotational movement from a respective finger actuator to a respective lead screw assembly.

23. A dexterous robotic hand, comprising:

a palm housing;

a plurality of flexible fingers each movably secured to the palm housing, each finger including a proximal segment supported by the palm housing and to another segment supported by the proximal segment;

a decoupling mechanism pivotally supported on the proximal segment of at least one of the plurality of fingers for controlling movement of the another segment independent of movement of the proximal segment;

a plurality of lead screw assemblies each supported on the palm housing, each lead screw assembly including a coupling end;

a plurality of finger actuators each operatively connected to a coupling end for moving the proximal segment of a respective finger relative to the palm housing;

a decoupling lead screw assembly supported b the palm housing, the decoupling lead screw assembly including a coupling end; and

a decoupling actuator operatively connected to the coupling end of the decoupling lead screw assembly for pivotally rotating the decoupling mechanism relative to the proximal segment.

24. The dexterous robotic hand of claim 23, further comprising:

a plurality of flexible cables each for interconnecting an actuator with a respective lead screw assembly.

25. The dexterous robotic hand of claim 23, further comprising:

a link member for mechanically interconnecting the decoupling mechanism with the another segment.

26. The dexterous robotic hand of claim 23, further comprising:

a cable interconnecting the decoupling lead screw assembly and the decoupling mechanism, the cable being interconnected such that pivotal movement of the proximal segment with respect to the palm housing is independent of pivotal movement of the another segment relative to the proximal segment.

27. The robotic hand of claim 23, wherein the plurality of flexible fingers comprises:

a dexterous finger, a grasping finger and a thumb each movably secured to the palm housing;

the grasping finger being positioned opposite the thumb relative to the dexterous finger; and

the thumb being pivotally connected to the palm housing at a position spaced from a plane of the pivotal connection of the dexterous finger and the grasping finger with the palm housing.

28. The robotic hand of claim 27, wherein a plurality of hingedly connected segments on the dexterous finger comprises:

the proximal segment, an intermediate segment and a distal segment, the intermediate segment being pivotally linked to the decoupling assembly such that the intermediate and distal segment bend independent of the proximal segments.

29. The robotic hand of claim 27, wherein a plurality of hingedly connected segments on the grasping finger comprises:

the proximal segment, an intermediate segment and a distal segment, the proximal, intermediate and distal segments being pivotally linked such that the intermediate and distal segments simultaneously bend as a function of the bending of the proximal segment.

30. The robotic hand of claim 27, wherein a plurality of hingedly connected segments on the thumb comprises:

the proximal segment and a distal segment, the distal segment being pivotally linked to the decoupling assembly such that the distal segment bends independent of the proximal segment.

31. A robotic finger drive train for positioning a finger with respect to a palm housing, comprising:

a drive train actuator;

a flexible shaft rotated by the drive train actuator;

a lead screw assembly for converting rotary motion of the flexible shaft into linear motion; and

a cable linearly moveable in response to a lead screw assembly and interconnected with the finger for pivoting the finger with respect to the palm housing.

32. The robotic finger drive train as defined in claim 31, wherein the lead screw assembly comprises:

a tubular sleeve having a sleeve axis;

a body movably mounted at least partially within the tubular sleeve for movement relative to the tubular sleeve along the sleeve axis, the body including a distal end for interconnection with the cable and a proximal end; and

a lead screw disposed at least partially within the tubular sleeve, the lead screw having a proximal end threadably connected to the proximal end of the body and a distal end rotatably mounted within the coupling end such that rotation of the lead screw produces movement of the body and at least a portion of the cable along the sleeve axis.

33. The robotic finger drive train of claim 32, further comprising:

a gauge attached to the tubular sleeve for sensing stress on the robotic finger cable.

34. The robotic finger drive train of claim 31, further comprising:

a decoupling lead screw assembly supported by the palm housing, the decoupling lead screw assembly including a cable end and a coupling end;

a decoupling mechanism powered by the decoupling lead screw assembly for controlling movement of a finger segment independent of movement of a proximal segment of the respective finger;

a decoupling flexible cable secured to the decoupling lead screw assembly; and

a decoupling actuator operatively connected to the coupling end of the decoupling lead screw assembly for actuating the decoupling flexible cable.

35. The robotic finger drive train of claim 34, wherein the decoupling lead screw assembly is pivotally connected to the proximal segment of the finger and enables controlled movement of an intermediate finger segment and distal finger segment independent of movement of the proximal finger segment.