Cobots

• US 5,952,796 A
• Filed: 10/28/1997
• Issued: 09/14/1999
• Est. Priority Date: 02/23/1996
• Status: Expired due to Term

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Peshkin, Michael A., Colgate, James E.
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/959,357
• Time in Patent Office: 686 Days
• Field of Search: 318/1, 318/2, 318/580, 318/587, 318/568.11, 318/568.12, 318/568.14, 318/625, 318/560, 901/1, 901/2, 901/4, 901/19, 901/20, 901/50, 180/6.44, 180/6.54-6.62
• US Class Current: 318/1
• CPC Class Codes: B25J 9/1656 characterised by programming, planning systems for manipulators
• CPC Class Codes: B25J 9/1689 Teleoperation
• CPC Class Codes: G05B 2219/39253 Virtual arm, has end effector on any joint of real manipulator
• CPC Class Codes: G05B 2219/40117 Virtual mecanism, like slider to constraint movement in task space
• CPC Class Codes: G05B 2219/40118 Task oriented virtual tool, developed for task, assists operator in task
• CPC Class Codes: G05B 2219/40122 Manipulate virtual object, for trajectory planning of real object, haptic display
• CPC Class Codes: G05B 2219/40131 Virtual reality control, programming of manipulator
• CPC Class Codes: G05B 2219/40415 Semi active robot, cobot, guides surgeon, operator to planned trajectory, constraint
• CPC Class Codes: G05B 2219/40517 Constraint motion planning, variational dynamic programming
• CPC Class Codes: G06F 3/011 Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00

Abstract

An apparatus and method for direct physical interaction between a person and a general purpose manipulator controlled by a computer. The apparatus, known as a collaborative robot or "cobot," may take a number of configurations common to conventional robots. In place of the actuators that move conventional robots, however, cobots use variable transmission elements whose transmission ratio is adjustable under computer control via small servomotors. Cobots thus need few if any powerful, and potentially dangerous, actuators. Instead, cobots guide, redirect, or steer motions that originate with the person. A method is also disclosed for using the cobot'"'"'s ability to redirect and steer motion in order to provide physical guidance for the person, and for any payload being moved by the person and the cobot. Virtual surfaces, virtual potential fields, and other guidance schemes may be defined in software and brought into physical effect by the cobot.

Claims

1. A robotic device allowing for collaboration with a human operator, said device having one or more joints and an endpoint movable by an operator in a plurality of directions, comprising:

at least one non-holonomic transmission element which couples a velocity of said endpoint in one of said directions with a velocity of said endpoint in another of said directions, said nonholonomic transmission element having a steering angle which controls a ratio of said velocities, whereby mechanically allowed directions of motion of said endpoint are dictated by the steering angle of said at least one non-holonomic transmission element; and

a computer, connected to said motor and said at least one non-holonomic transmission element, which controls the mechanically allowed directions of motion through space of said endpoint by adjusting the steering angle of said at least one non-holonomic transmission element.

2. The device of claim 1 wherein said endpoint has one instantaneous degree of freedom, a direction of said instantaneous degree of freedom being under control of said computer.

3. The device of claim 1 further comprising a memory which stores a description of a virtual surface.

4. The device of claim 1 wherein contents of said memory can be altered by the operator.

5. The device of claim 4 wherein said virtual surface includes a path to be followed by said endpoint.

6. The device of claim 4 wherein said computer controls the steering angle of said non-holonomic transmission element in order to prohibit any motion of the endpoint which would penetrate the virtual surface.

7. The device of claim 4 wherein said computer controls the steering angle of said non-holonomic transmission element so as to prohibit any motion of the endpoint that would penetrate said virtual surface when said robotic device is in contact with said virtual surface, and said computer controls the steering angle of said non-holonomic transmission element so as to provide apparent freedom of motion of said endpoint to a user when said endpoint is not in contact with said virtual surface.

8. The apparatus of claim 7, wherein said computer controls the steering angle of said non-holonomic transmission element when said endpoint is not in contact with said virtual surface in a manner such that said endpoint appears to the operator to have a plurality of degrees of freedom.

9. The device of claim 5 wherein said computer continuously adjusts the steering angle of said non-holonomic transmission element as said endpoint is moved along said path by an operator so that the endpoint will move smoothly along said path.

10. The device of claim 4 wherein the at least one non-holonomic transmission element comprises a wheel.

11. The device of claim 10 wherein said wheel couples translational velocities of motion of the endpoint.

12. The device of claim 11 wherein said wheel is confined in contact with a plane.

13. The device of claim 4, wherein the at least one non-holonomic transmission element comprises three wheels which roll in contact with a single plane.

14. The device of claim 4 wherein the at least one non-holonomic transmission element comprises a spherical transmission element confined in contact with a plurality of rollers.

15. The device of claim 4 wherein a spherical transmission element couples rotational velocities of motion of some of said rollers in a ratio set by a steering angle other of said rollers.

16. The device of claim 4 wherein a spherical transmission element couples angular velocities of two joints of the robotic device.

17. The device of claim 4 further comprising sensors for measuring a configuration of said robotic device, a heading and speed of said endpoint, and a force applied by an operator to said endpoint, wherein said computer controls the steering angle of said non-holonomic transmission element in response to the position and speed of the robotic device and the force applied by an operator to the endpoint of the robotic device.

18. The device of claim 4 further comprising a motor, connected to the non-holonomic transmission element, which receives an input from the computer and adjusts the steering angle of the non-holonomic transmission element based on the input received from the computer.

19. The device of claim 4, comprising a plurality of non-holonomic transmission elements.

20. The device of claim 19, wherein each of said plurality of non-holonomic transmission elements is located at one of the joints of the robotic device.

21. The device of claim 20 wherein the number of said non-holonomic transmission elements is greater than two.

22. The device of claim 4 wherein said computer includes software that can be reprogrammed to alter the operation of said computer.

23. The device of claim 4 wherein said endpoint comprises a tool to be manipulated by an operator.

24. The device of claim 4 wherein said endpoint comprises a payload to be moved by an operator.

25. The device of claim 4, wherein said robotic device is passive, whereby all motive power necessary to move the endpoint is supplied by the operator.

26. The device of claim 4, wherein said robotic device is active, whereby the robotic device supplies power to assist or resist forces applied by the operator to the endpoint.

27. The device of claim 26, wherein said non-holonomic transmission element is coupled to an actuator for assisting forces applied by the operator to the endpoint.

28. The device of claim 26, wherein said non-holonomic transmission element is coupled to a brake for resisting forces applied by the operator to the endpoint.

29. The device of claim 26, further comprising a plurality of non-holonomic transmission elements, said plurality of non-holonomic transmission elements including a common link.

30. The device of claim 29, wherein said common link is coupled to an actuator for assisting forces applied by the operator to the endpoint.

31. The device of claim 29, wherein said common link is coupled to a brake for resisting forces applied by the operator to the endpoint.

32. The device of claim 30, wherein said actuator is coupled to said common link in a manner such as to assist an operator in lifting loads against gravity.

33. The device of claim 30, wherein said actuator is coupled to said common link in a manner such as to assist an operator in overcoming frictional or inertial resistance in moving a large load.

34. The device of claim 31, wherein said brake is coupled to said common link in a manner such as to slow down said endpoint when it reaches a particular location.

35. The device of claim 17, further comprising:

an overhead rail assembly comprising a platform slidably mounted on a plurality of rails such that the platform can move in a plane; and

an arm having a first end attached to said platform and a second end extending downwardly from said platform, whereby said second end corresponds to the endpoint of the robotic device;

wherein said at least one non-holonomic transmission element couples directional velocities of motion of said platform in said plane.

36. The device of claim 35, wherein said arm is attached to a payload to be moved by a human operator.

37. The device of claim 36, wherein said at least one non-holonomic transmission element comprises a spherical transmission element confined in contact with a plurality of rollers.

38. The device of claim 37 wherein said overhead rail assembly comprises a plurality of pulleys, whereby a ratio of speeds of said pulleys are controlled by said spherical transmission element, and said ratio of speeds of said pulleys control directional motion of said platform in said plane.

39. The device of claim 36, wherein said at least one non-holonomic transmission element comprises a plurality of spherical transmission elements, further comprising a common link coupled to said plurality of spherical transmission elements.

40. The device of claim 17, further comprising an articulated arm assembly having a plurality of rotatable links coupled together by said at least one non-holonomic transmission element, said articulated arm assembly having an endpoint corresponding to the endpoint of the robotic device and capable of movement within a three dimensional workspace;

wherein said at least one non-holonomic transmission element couples a ratio of angular velocities of said links of said articulated arm assembly.

41. The device of claim 39 wherein said at least one non-holonomic transmission element comprises a spherical transmission element confined in contact with a plurality of rollers.

42. The device of claim 40 wherein the at least one non-holonomic transmission element comprises a plurality of spherical transmission elements each confined in contact with a plurality of rollers, each of which couples a ratio of angular velocities of a plurality of links of said articulated arm assembly.

43. The device of claim 42, further comprising a common link coupled to said plurality of spherical transmission elements.

44. An apparatus allowing for collaboration between said apparatus and a human operator, said device having one or more joints and an endpoint having a plurality of apparent degrees of freedom, comprising:

one or more joints;

an endpoint having a plurality of apparent degrees of freedom;

one or more sensors for measuring a position and speed of said endpoint and a force applied by an operator to said endpoint;

at least one continuously variable transmission element which couples a velocity of said endpoint in one of said degrees of freedom with a velocity of said endpoint in another of said degrees of freedom, said continuously variable transmission element having a steering angle which controls a ratio of said velocities, whereby said continuously variable transmission element restricts motion of said endpoint at a particular instant in time to a single instantaneous degree of freedom which is adjustable by varying said steering angle;

a motor, connected to said continuously variable transmission element which adjusts the steering angle of the continuously variable transmission element, thereby adjusting the ratio of said velocities; and

a computer, which receives from said sensors signals representing the position and speed of the endpoint and the force applied by an operator to the endpoint, and controls the operation of said motor in response to said signals, thereby controlling the instantaneous degrees of freedom of said endpoint.

45. The apparatus of claim 44, wherein said computer controls said motor such that said endpoint appears to the operator to have a plurality of degrees of freedom.

46. A robotic device allowing for collaboration with a human operator, said device having one or more joints and an endpoint having a plurality of degrees of freedom, comprising:

means for determining a position and speed of said endpoint and a force applied by an operator to said endpoint;

means for coupling a velocity of said endpoint in one of said degrees of freedom with a velocity of said endpoint in another of said degrees of freedom, said continuously variable transmission element having an adjustable steering angle which controls a ratio of said velocities, whereby said coupling means restricts motion of said endpoint at a particular instant in time to a single direction of motion which is adjustable by varying said steering angle;

means for adjusting said steering angle;

means for controlling said adjusting means based on the position and speed of said endpoint and the force applied by an operator to said endpoint, thereby controlling the mechanically allowed direction of motion through space of said endpoint.

47. An apparatus as claimed in claim 46, wherein said means for controlling also controls the steering angle of said at least one non-holonomic transmission element in response to forces applied by the user when the device is remote from the virtual surface so as to provide to the user an apparent increased number of degrees of freedom of motion of the device when said device is remote from said virtual surface.

48. A method for controlling a robotic device having a plurality of joints coupled together by at least one steerable non-holonomic transmission element coupled together by at least one steerable non-holonomic transmission element and endpoint movable by an operator in a plurality of directions, said non-holonomic transmission element having a steering angle for controlling its transmission ratio, comprising:

storing a virtual surface;

determining the position and speed of the endpoint of the robotic device;

measuring the force applied by an operator to the endpoint;

adjusting a steering angle of said non-holonomic transmission element so as to prohibit any motion of the endpoint that would penetrate said virtual surface when said robotic device is in contact with said virtual surface; and

adjusting the steering angle of said non-holonomic transmission element so as to provide apparent freedom of motion of the endpoint to a user when said endpoint is not in contact with the virtual surface.

49. A method for controlling a robotic device having a plurality of joints coupled together by at least one steerable non-holonomic transmission element and an endpoint movable by an operator in a plurality of directions, comprising:

storing a path to be followed by the robotic device;

determining the position and speed of the robotic device;

measuring the force applied by an operator to the robotic device;

continuously adjusting the steering angle of said non-holonomic transmission element as said robotic device is moved along said path by an operator so that the robotic device will move smoothly along said path.