Gravity-counterbalanced robot arm

Patent metadata

Field	Value
Publication number	US-9314934-B2
Application number	US-201414191611-A
Country	US
Kind code	B2
Filing date	Feb 27, 2014
Priority date	Feb 27, 2014
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

An arm assembly for use in a robot to provide gravity counterbalancing of the robot arms. The arm assembly includes an arm and a drive assembly. The arm assembly includes a differential interconnecting the drive assembly with the arm link. The differential is attached to a torso-side or upper end of the arm link, and the differential is adapted to provide gravity counterbalancing for the predefined mass of the arm link. A pair of half counterweights are provided and arranged to each move in one degree of freedom and to provide two equal counterweights to the differential's two inputs such as input gears, pulleys, or the like. The drive assembly includes two motors that are grounded. In some embodiments, both the motors and the counterweights are spaced apart from the robot's shoulder, i.e., spaced apart from the differential near the robot's pelvis or low in the torso.

First claim

I claim:

1. An arm apparatus for use in a robot to provide gravity counterbalancing, comprising:
an arm link with a predefined mass;
a drive assembly selectively operating to move the arm link through a range-of-motion; and
a differential mechanism interconnecting the drive assembly with the arm link,
wherein the differential mechanism is directly attached to an end of the arm link whereby the end of the arm link moves in direct response to operation of the differential mechanism,
wherein the differential mechanism is adapted to provide gravity counterbalancing for the predefined mass of the arm link,
wherein the differential mechanism includes first and second input elements coupled to the end of the arm link, and
wherein the differential mechanism includes a first counterweight, spaced apart from the first input element, providing gravity counterbalancing to the first input element and a second counterweight, spaced apart from the second input element, providing gravity counterbalancing to the second input element.

2. The arm apparatus of claim 1 , wherein the predefined mass is the mass of the arm link combined with an effective mass of all serially-connected links downstream of the arm link.

3. The arm apparatus of claim 1 , wherein the differential mechanism comprises a cable differential including a first pair of capstans with a first diameter and interconnected with a first cable and a second pair of capstans with a second diameter and interconnected with a second cable.

4. The arm apparatus of claim 3 , wherein an input one of the first pair of capstans and an input one of the second pair of capstans are independently driven by the drive assembly, the drive assembly including a pair of pulleys spaced apart a distance from the differential that are independently rotated by a pair of motors.

5. The arm apparatus of claim 4 , wherein each of the pulleys of the drive assembly has a counterweight providing the gravity counterbalancing for the predefined mass of the arm link.

6. The arm apparatus of claim 5 , wherein the counterweights each are configured to provide equal amounts of counter torque to balance the arm link against gravity.

7. The arm apparatus of claim 6 , wherein the counterweights have substantially equal weights.

8. The arm apparatus of claim 1 , wherein the range-of-motion is unrestricted by the differential or the drive assembly, wherein the drive assembly is backdrivable, and wherein two degrees of freedom (DOF) of the arm link are grounded.

9. A robot arm assembly, comprising:
a differential mechanism with first and second inputs and first and second outputs;
an arm attached via an arm mounting element to the differential mechanism to move with the first and second outputs;
a first counterbalance connected to the first input to counterbalance gravity on the arm in a first degree of freedom (DOF);
a second counterbalance connected to the second input to counterbalance gravity on the arm in a second DOF;
a first motor spaced apart from the differential mechanism adapted for driving the first input; and
a second motor spaced apart from the differential mechanism adapted for driving the second input independently from operations of the first motor.

10. The robot arm assembly of claim 9 , wherein the first and second counterbalances each comprise a counterweight and wherein the counterweights are of equal weight.

11. The robot arm assembly of claim 9 , wherein the first counterbalance applies a first counter torque on the first input and the second counterbalance applies a second counter torque, which is equal to the first counter torque, on the second input.

12. The robot arm assembly of claim 9 , wherein the first and second motors are grounded when the robot arm assembly is mounted in a robot.

13. A robot comprising:
a torso with a shoulder;
a differential mounted within the shoulder, wherein the differential includes two output elements and two input elements each interconnected with one of the output elements, whereby movement of one of the input elements causes corresponding movement in the interconnected output element;
an upper arm attached to the differential to move with movement of either of the output elements of the differential through a range-of-motion that is unrestricted by the differential;
first and second motors independently operating to move the two input elements; and
first and second counterbalances to apply equal counter torques, respectively, on the input elements of the differential,
wherein the upper arm is counterbalanced against gravity,
wherein the first and second motors each rotate a pulley, having a rotation axis parallel to an axis passing through the shoulder, interconnected to and driving movement of one of the input elements, and
wherein the first and second motors are positioned within the torso to be spaced from the shoulder.

14. The robot of claim 13 , wherein both of the motors are mounted within the torso to provide grounding of the motors.

15. The robot of claim 13 , wherein the first and second counterbalances each comprises a counterweight that is mounted within the torso to be spaced apart from the shoulder and to move in one of the DOFs of the differential.

16. The arm apparatus of claim 1 , wherein the first and second counterweights provide equal amounts of counter torque to balance the arm link against gravity.

Assignees

• Disney Entpr Inc

Inventors

• Whitney John P

Classifications

• Y10T74/20305

  Robotic arm · CPC title

• B25J19/002 Primary

  using counterweights · CPC title

• Y10S901/48

  Counterbalance · CPC title