Wrist with decoupled motion transmission

• US 20030208186A1
• Filed: 03/06/2003
• Published: 11/06/2003
• Est. Priority Date: 05/01/2002
• Status: Active Grant

• Current Assignee: Manuel Ricardo Moreyra
• Original Assignee: Manuel Ricardo Moreyra
• Inventors: Moreyra, Manuel Ricardo
• Granted Patent: US 6,969,385 B2
• Time in Patent Office: Days
• US Class Current: 606/1
• CPC Class Codes: A61B 2034/305 Details of wrist mechanisms at distal ends of robotic arms
• CPC Class Codes: A61B 2034/715 Cable tensioning mechanisms for removing slack
• CPC Class Codes: A61B 34/30 Surgical robots
• CPC Class Codes: A61B 34/71 Manipulators operated by drive cable mechanisms
• CPC Class Codes: Y10T 74/20305 Robotic arm

Abstract

The present invention is a wrist mechanism and a method for making robotic devices in which the transmission of motion, force and/or torque around a revolute joint can be accomplished without coupling. This construction allows mounting the actuators on the base or lower elements of a mechanism, so that only linkage elements move the end-effector. Thus reducing inertia of the moving elements and increasing performance of the device. The decoupled motion of the end-effector or links is achieved by routing their transmission cables around idler pulleys placed parallel to the joint rotation axis on an optimal position such any stretch on the transmission cable is minimized. In particular, this construction can be use for robotic surgical tools that have two independently driven jaws, decoupled and orthogonal from its articulating wrist.

Claims

1. A wrist for minimizing stretch in a cable coupling an end-effector and a drive mechanism, the wrist comprising:

a base having a wrist axis;

a link including an end-effector portion and a base portion, wherein the end-effector portion has a link axis and is attachable to an end-effector, and wherein the base portion is pivotally attached to the base and operable to pivot about the wrist axis; and

an idler having a diameter and rotatably attached to the base, wherein the idler is operable to rotate about an idler axis that is offset from the wrist axis.

2. The wrist of claim 1 wherein the offset depends on a desired range of motion for the link, the ratio of the idler diameter to the distance between the link axis and the wrist axis, and the diameter of the idler.

3. The wrist of claim 1 wherein the desired range of motion for the link is 180°

, the idler diameter is 5 millimeters, the distance between the link and wrist axes is 12.5 millimeters, and the idler axis is offset 1.48 millimeters from the wrist axis.

4. The wrist of claim 1 further comprising an end-effector pivotally attached to the end-effector portion of the link and operable to pivot about the link axis and wherein the motion of the link about the wrist axis is independent from the motion of the end-effector about the link axis.

5. The wrist of claim 4 further comprising a cable coupled to the end-effector and operable to pivot the end-effector about the link axis, wherein when the link is pivoted about the wrist axis and the end-effector is pivoted about the link axis, a portion of the cable contacts the idler.

6. The wrist of claim 1 wherein the idler is a pulley.

7. The wrist of claim 1 wherein the idler axis is parallel or substantially parallel to the wrist axis.

8. The wrist of claim 1 wherein the link axis is perpendicular or substantially perpendicular to the wrist axis.

9. The wrist of claim 1 wherein the wrist includes at least two idlers operable to rotate about the idler axis.

10. The wrist of claim 1 wherein the wrist includes eight idlers attached to the base in four groups of two, each idler is a pulley having a diameter, and the two idlers in each group are concentric with the each other, and wherein each idler is operable to pivot about one of four respective idler axes that are each offset from the wrist axis, and each group is disposed between the base and the link.

11. The wrist of claim 3 wherein:

the end-effector includes a first and second jaw opposing each other;

a first cable is coupled to the first jaw and operable to pivot the first jaw about the link axis; and

a second cable is coupled to the second jaw and operable to pivot the second jaw about the link axis.

12. The wrist of claim 11 wherein the jaws can be pivoted about the link axis independent of each other.

13. A tool for grasping, cutting, clamping, moving items, comprising:

an arm;

a wrist including;

a base having a wrist axis,

a link including an end-effector portion and a base portion, wherein the end-effector portion has a link axis and is attachable to an end-effector, and wherein the base portion is pivotally attached to the base and operable to pivot about the wrist axis, and

an idler having a diameter and rotatably attached to the base, wherein the idler is operable to rotate about an idler axis that is offset from the wrist axis, and

an end-effector pivotally attached to the end-effector portion and operable to pivot about the link axis;

a cable coupled to the end-effector and operable to pivot the end-effector about the link axis, wherein when the link is pivoted about the wrist axis and the end-effector is pivoted about the link axis, a portion of the cable contacts the idler;

a drive mechanism coupled to the cable and operable to pivot the end-effector about the link axis.

14. The tool of claim 13 wherein the drive mechanism includes an actuator operable to pivot the end-effector about the link axis.

15. The tool of claim 13 wherein the drive mechanism includes a pulley hanger operable to pivot the end-effector about the link axis.

16. The tool of claim 13 further comprising a wrist cable coupled to the link of the wrist and operable to pivot the link about the wrist axis.

17. The tool of claim 13 wherein the arm includes two sections and a second wrist pivotally attaching the two sections together wherein the second wrist includes:

a second base having a wrist axis,

a second link including an end-effector portion having a link axis and a second base portion pivotally attached to the second base and operable to pivot about the wrist axis of the second base, and

a second idler having a diameter and rotatably attached to the second base, wherein the second idler is operable to rotate about an idler axis that is offset from the wrist axis of the second wrist.

20. A method for minimizing stretch in a cable that couples an end-effector to a drive mechanism, the method comprising:

pivotally attaching a link of a wrist to a base of the wrist, wherein the link can pivot about a wrist axis;

pivotally attaching an idler to the base such that the idler pivots about an idler axis that is offset from the wrist axis; and

contacting the idler with a cable attached to the end-effector when the link is pivoted about the wrist axis.