FORCE LIMITING DEVICE AND METHOD

• US 20110126660A1
• Filed: 11/30/2009
• Published: 06/02/2011
• Est. Priority Date: 11/30/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company), Universite Laval
• Original Assignee: GM Global Technology Operations Incorporated (General Motors Company), Universite Laval
• Inventors: Lauzier, Nicolas, Grenier, Martin, Stevenson, Robin, Gao, Dalong, Gosselin, Clement
• Granted Patent: US 8,601,897 B2
• Time in Patent Office: Days
• US Class Current: 74/490.05
• CPC Class Codes: B25J 17/00 Joints
• CPC Class Codes: B25J 17/0208 Compliance devices
• CPC Class Codes: B25J 17/0266 comprising more than two actuating or connecting rods
• CPC Class Codes: B25J 19/0091 Shock absorbers in general F16F
• CPC Class Codes: B25J 19/063 working only upon contact with an outside object
• CPC Class Codes: B25J 9/0048 with kinematics chains of the type rotary-rotary-rotary
• CPC Class Codes: Y10S 901/28 Joint
• CPC Class Codes: Y10S 901/46 Sensing device
• CPC Class Codes: Y10T 74/20305 Robotic arm
• CPC Class Codes: Y10T 74/20329 Joint between elements

Abstract

The present invention relates to a method and apparatus for limiting the contact force between a moving device and another object, using a parallel mechanism and torque limiters where the threshold force to activate the force limiting mechanism is not related to the configuration of the moving device or the location of the contact force relative to the activation point of the force limiting mechanism, and where the mechanism may be configured for one, two or three degrees of freedom. A counterbalance mechanism is also provided to counteract gravity load when the force limiting mechanism is configured for three degrees of freedom and responsive to contact forces including a vertical element. In particular, the invention relates to a method and apparatus for limiting the contact force between a moving robotic device and a contactable object.

Claims

1. A force limiting device configured to limit the contact force of a moving object with a contacted object, the device comprising:

a first attachable portion;

a second attachable portion;

one or more parallelogram linkages; and

a torque limiter;

wherein the first attachable portion is connectable at a first end of the force limiting device and the second attachable portion is connectable at a second end of the force limiting device;

wherein the one or more parallelogram linkages establish the orientation of the first attachable portion to the second attachable portion;

wherein each of the one or more parallelogram linkages is configured to transmit an input torque;

wherein the torque limiter has an activation torque and is configured to be activated when the input torque transmitted through the one or more parallelogram linkages exceeds the activation torque;

wherein the one or more parallelogram linkages is configured to maintain a rigid orientation between the first attachable portion and the second attachable portion when the input torque is less than the activation torque; and

wherein the one or more parallelogram linkages is configured to be sufficiently compliant when the input torque exceeds the activation torque to decrease the contact force between the moving object and the contacted object.

2. The force limiting device of claim 1,

wherein the moving object has a moving portion and a suspended portion;

wherein the first attachable portion is attached to the moving portion and the second attachable portion is attached to the suspended portion; and

wherein the one or more parallelogram linkages of the force limiting device is configured to operatively connect the moving portion and the suspended portion of the moving object.

3. The force limiting device of claim 1,

wherein the one or more parallelogram linkages includes a rotatable joint;

wherein the rotatable joints of at least one of the one or more parallelogram linkages includes a torque limiting mechanism configured to activate the force limiting device when the input torque exceeds a torque limit; and

wherein the torque limit is equivalent to the activation torque.

4. The force limiting device of claim 1,

wherein each of the one or more parallelogram linkages is operatively connected to the first attachable portion through one or more rotatable joints;

wherein each of the one or more parallelogram linkages is operatively connected to the second attachable portion through a one or more rotatable joints;

wherein one of the rotatable joints of each of the one or more parallelogram linkages includes a torque limiting mechanism configured to activate the force limiting device when the input torque exceeds a torque limit; and

wherein the torque limit is equivalent to the activation torque.

5. The force limiting device of claim 1,

wherein the one or more parallelogram linkages includes a first parallelogram linkage and a second parallelogram linkage;

and

wherein the first parallelogram linkage is perpendicular to the second parallelogram linkage.

6. The force limiting device of claim 1,

wherein the one or more parallelogram linkages includes at least three parallelogram linkages;

and

wherein the at least three parallelogram linkages are arranged in a Delta configuration.

7. The force limiting device of claim 6, further comprising a gravity compensating mechanism.

8. The force limiting device of claim 7, wherein the gravity compensating mechanism includes at least one of a spring and a counterbalance.

9. A robot system adapted for overhead suspension, the system comprising:

a robot;

a suspended portion movable by the robot toward an object; and

a force limiting device activatable at an activation level and including a parallelogram linkage;

wherein the parallelogram linkage of the force limiting device is configured to operatively attach the robot to the suspended portion;

wherein the suspended portion is configured to exert a contact force against the object when the suspended portion moves;

wherein an activation force is inputted to the suspended portion opposing the contact force;

wherein the force limiting device is activated when the activation force exceeds the activation level;

wherein the force limiting device becomes sufficiently compliant when activated so that the contact force exerted against the object by the suspended portion is decreased when the force limiting device becomes compliant.

10. The robot system of claim 9, further comprising:

wherein the force limiting device includes one or more parallelogram linkages;

wherein the one or more parallelogram linkages establish the orientation of the robot to the suspended portion;

wherein each of the one or more parallelogram linkages is operatively connected to the robot through a revolute joint including a torque limiter;

wherein the activation force is transmitted to the at least one torque limiter.

11. The robot system of claim 9, further comprising:

two parallelogram linkages including a first parallelogram linkage and a second parallelogram linkage; and

wherein the first parallelogram linkage is perpendicular to the second parallelogram linkage.

12. The robot system of claim 9, further comprising:

at least three parallelogram linkages; and

wherein the at least three parallelogram linkages are arranged in a Delta architecture.

13. The robot system of claim 12, wherein the system suspended overhead includes a payload;

and further comprising;

a gravity compensating mechanism;

wherein the gravity compensating mechanism counteracts the weight of at least one of the suspended portion and the payload.

14. The robot system of claim 13, wherein the gravity compensating mechanism includes at least one of a spring and a counterbalance.

15. A method for limiting the contact force of a robot with an object, the method comprising:

operatively attaching an activatable force limiting device between a robot and a suspended portion;

wherein the force limiting device includes at least one jointed parallelogram linkage;

transmitting a contact force to the force limiting device when the suspended portion contacts an object;

activating the force limiting device when the contact force exceeds an activation force such that the force limiting device becomes compliant; and

decreasing the contact force inputted to the object by the suspended portion when the force limiting device becomes compliant.

16. The method of claim 15,

wherein at least one joint of the at least one parallelogram linkage is rotatable;

and

wherein the rotatable joint of the at least one parallelogram linkage includes a torque limiting mechanism for activating the force limiting device when the input torque exceeds a torque limit equivalent to the activation torque.

17. The method of claim 15, further comprising:

wherein the at least one parallelogram linkage is configured to be operatively connected to the robot through one or more rotatable joints;

wherein each of the at least one parallelogram linkage is configured to be operatively connected to the suspended portion through the one or more rotatable joints;

wherein one of the rotatable joints of each of the at least one parallelogram linkage includes a torque limiting mechanism for activating the force limiting device when the input torque exceeds a torque limit equivalent to the activation torque.

18. The method of claim 15, further comprising:

wherein the at least one parallelogram linkage includes a first parallelogram linkage and a second parallelogram linkage; and

wherein the first parallelogram linkage is perpendicular to the second parallelogram linkage.

19. The method of claim 15, further comprising:

wherein the at least one parallelogram linkage includes at least three parallelogram linkages arranged in a Delta configuration; and

the force limiting device includes a gravity compensating mechanism.

20. The method of claim 15, further comprising:

wherein the gravity compensating mechanism includes at least one of a spring and a counterbalance.