Method for planning/controlling robot motion

• US 5,835,684 A
• Filed: 11/09/1994
• Issued: 11/10/1998
• Est. Priority Date: 11/09/1994
• Status: Expired due to Term

• Current Assignee: Amada Company Limited
• Original Assignee: Amada America, Inc. (Amada Company Limited), Amada Company Limited
• Inventors: Bourne, David Alan, Krishnan, Sivaraj Sivarama
• Primary Examiner(s): Davis, George B.
• Application Number:
  US08/338,115
• Time in Patent Office: 1,462 Days
• Field of Search: 395/90, 364/461, 364/474.2
• US Class Current: 700/255
• CPC Class Codes: B25J 9/1666 Avoiding collision or forbidden zones
• CPC Class Codes: G05B 2219/40421 Motion planning for manipulator handling sheet metal profiles
• CPC Class Codes: G05B 2219/40444 Hierarchical planning, in levels
• CPC Class Codes: G05B 2219/40445 Decompose n-dimension with n-links into smaller m-dimension with m-1-links
• CPC Class Codes: G05B 2219/40446 Graph based
• CPC Class Codes: G05B 2219/40458 Grid adaptive optimization
• CPC Class Codes: G05B 2219/40463 Shortest distance in time, or metric, time optimal
• CPC Class Codes: G05B 2219/40476 Collision, planning for collision free path
• CPC Class Codes: G05B 2219/40488 Coarse and fine motion planning combined
• CPC Class Codes: G05B 2219/40497 Collision monitor controls planner in real time to replan if collision
• CPC Class Codes: G05B 2219/45143 Press-brake, bending machine

Abstract

A computerized method/system is provided for planning motion of a robot within a free space confined by obstacles, from an initial position to a goal position. In executing the method/system, a plan is generated so that the robot can hold and maneuver a workpiece throughout a sequence of bending operations to be performed by a bending apparatus. A plurality of proposed movements to be made by the robot are proposed for an mth movement within a sequence of movements, and at least a portion of the robot and the obstacles that confine the free space are modeled. A determination is made as to whether a collision will occur between the robot and an obstacle for each proposed movement, and a plan is generated including the sequence of movements by choosing for each movement in the sequence of movements, a proposed movement that will not result in a collision and that will bring the robot closer to the goal position. In choosing proposed movements, an estimated cost associated with each proposed movement may be taken into account. The estimated cost may be based upon a euclidian distance to the goal position from the position of the robot after the particular proposed movement is made as the mth movement, and/or the estimated cost may be determined as a function of the robot travel time from an (m-1)th movement to the mth movement. Different methods are provided for performing fine motion planning and gross motion planning.

Claims

1. In a computer having at least one processor and a memory, a method for planning motion of a robot within free space, restricted by obstacles, from an initial position to a goal position, said obstacles comprising components of a bending apparatus, said method comprising:

proposing, for a movement within a sequence of movements, a plurality of proposed movements to be made by the robot;

modeling at least a portion of the robot and the obstacles that restrict the free space;

determining whether a collision will occur between the robot and an obstacle for a proposed movement being executed as said movement within said sequence of movements; and

generating a plan including said sequence of movements, by choosing, for each movement in said sequence of movements, a proposed movement that will not result in a collision and that will bring the robot closer to the goal position, said generating a plan comprising planning a gross motion plan including movements of the robot in the free-space and planning a fine motion plan including movements of the robot to and from the bending apparatus.

2. The method according to claim 1, wherein said robot comprises a robot gripper for holding and maneuvering a workpiece throughout a sequence of bending operations to be performed by the bending apparatus.

3. The method according to claim 2, wherein:

said fine motion planning comprises planning a plurality of free space fine motion solution paths that extend between a plurality of respective pairs of positions, q_i and q_g ; and

said gross motion planning comprises planning a plurality of free space gross motion solution paths that extend between a plurality of respective pairs of positions, Q_i and Q_g.

4. The method according to claim 3, wherein said fine motion planning comprises performing said steps of proposing, modeling, determining and generating, for each pair of positions q_i and q_g, said proposing step comprising specifying a plurality of movements in configuration space for the said movement in said sequence of movements and identifying which ones of the specified plurality of movements are feasible by performing collision checking.

5. The method according to claim 4, wherein said gross motion planning comprises performing said steps of proposing, modeling, determining and generating, for each pair of positions Q_i and Q_g, said proposing step comprising proposing a set of movements within a maximal overlapping parallelepiped within the free space of said robot.

6. The method according to claim 3, wherein said gross motion planning comprises performing said steps of proposing, modeling, determining and generating, for each pair of positions Q_i and Q_g, said proposing step comprising proposing a set of movements within a maximal overlapping parallelepiped within the free space of said robot.

7. The method according to claim 2, further comprising:

calculating whether a simple collision-free path can be determined;

forming a plan including movements for traversing the simple collision-free path; and

inhibiting operation of said steps of proposing, determining and generating.

8. The method according to claim 2, wherein said gross motion plan comprises movements of the robot from a loading position, where a workpiece is retrieved by the robot gripper, to a bending stage position of the bending apparatus.

9. The method according to claim 2, wherein said fine motion plan comprises movements of the robot for loading a workpiece held by the robot gripper into a die space defined between a punch tool and die of the bending apparatus.

10. The method according to claim 2, wherein said gross motion plan comprises movements of the robot for moving a workpiece held by the robot gripper from a first bending stage position to a second bending stage position of the bending apparatus.

11. The method according to claim 2, wherein said fine motion plan comprises movements of the robot for unloading a workpiece held by the robot gripper from a die space defined between a punch tool and die of the bending apparatus.

12. The method according to claim 2, wherein said gross motion plan comprises movements of the robot for moving a workpiece held by the robot gripper from a final bending stage position of the bending apparatus to an unloading position.

13. The method of claim 2, wherein said modeling comprises modeling the workpiece held by the robot and said determining comprises determining whether a collision will occur between the workpiece held by the robot and an obstacle for a proposed movement.

14. The method according to claim 1, further comprising estimating a cost to be associated with each proposed movement, whereby said generating step comprises generating a plan including said sequence of movements, by choosing, for each movement in the sequence of movements, a proposed movement that will not result in a collision, that will bring the robot closer to the goal position, and that has a lowest estimated cost.

15. The method according to claim 14, wherein the estimated cost for a particular proposed movement comprises a Euclidian distance to the goal position from the position of the robot after said particular proposed movement is made as said movement in said sequence of movements.

16. The method according to claim 14, wherein the estimated cost for a particular proposed movement comprises an estimated value indicative of the robot travel time to move from a position after an another movement is made to a position of the robot after said particular proposed movement is made.

17. The method according to claim 1, further comprising, before said proposing step, specifying a plurality of movements in configuration space for said movement in said sequence of movements, and identifying which ones of the specified plurality of movements are feasible by performing collision checking, said proposing step comprising proposing movements from among the movements identified as feasible.

18. The method according to claim 17, wherein the specified plurality of movements specified for said movement in said sequence of movements comprises a plurality of movements in directions which collectively surround the position of the robot at the said another movement in said sequence of movements.

19. The method according to claim 17, wherein the specified plurality of movements for movement in said sequence of movements comprises movements in a plurality of intelligent movement directions.

20. The method according to claim 19, said method planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a downward movement of said robot causing said workpiece to move downward.

21. The method according to claim 19, said method planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a backward movement of said robot causing said workpiece to be backed out of the bending apparatus.

22. The method according to claim 19, said method planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a movement of said robot causing said workpiece to change in pitch from an inclined position towards a horizontal position.

23. The method according to claim 19, said method planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a movement of said robot causing said workpiece to be moved downward, to be moved backward away from said bending apparatus, and to drop in pitch from an angled position towards a horizontal position.

24. The method according to claim 1, further comprising:

forming an m-tree representation of a work space of said robot; and

computing maximal overlapping rectangloids within the free space of said m-tree representation of said work space.

25. The method according to claim 24, wherein said m-tree representation is an octree representation.

26. The method according to claim 24, wherein said maximal overlapping rectangloids comprise maximal overlapping parallelepipeds.

27. The method according to claim 24, wherein said proposing step comprises proposing for said movement in said sequence of movements, a set of movements of the robot to locations that fall within a maximal overlapping rectangloid within which the robot is located immediately after the another movement of said sequence of movements.

28. The method according to claim 27, wherein said set of movements comprises:

translating said robot to any one of eight corners of a presently occupied maximal overlapping rectangloid; and

moving said robot along any one of a plurality of predetermined directions which bring said robot to a position that corresponds to said goal position.

29. The method according to claim 27, wherein said set of movements comprises:

moving said robot in a first of three orthogonal directions to a position along the first orthogonal direction which corresponds to said goal position;

moving said robot in a second of the three orthogonal directions to a position along the second orthogonal direction which corresponds to said goal position;

moving said robot in a third of the three orthogonal directions to a position along the third orthogonal direction which corresponds to said goal position;

moving said robot in order to adjust a pitch of a gripper of said robot; and

moving said robot in order to adjust both pitch and yaw of the gripper of said robot.

30. The method according to claim 27, wherein said set of movements comprises moving along one of a plurality of orthogonal directions only when such movement would bring the robot to an orthogonal position that corresponds to the goal position.

31. The method according to claim 1, further comprising integrating said gross motion plan with said fine motion plan to generate said plan.

32. The method according to claim 1, wherein said robot comprises a robot gripper for holding a workpiece, and said fine motion plan comprises movements of the robot for loading and unloading the workpiece into a die space defined by a punch tool and die of the bending apparatus.

33. The method of claim 1, wherein said free space is a 3-D space environment, said plurality of proposed movements including a 3-D movement to be made by the robot.

34. A system for planning motion of a robot within free space, restricted by obstacles, from an initial position to a goal position, said obstacles comprising components of a bending apparatus, said system comprising:

proposing means for proposing, for a movement within a sequence of movements, a plurality of proposed movements to be made by said robot;

modeling means for modeling at least a portion of said robot and the obstacles that restrict the free space;

determining means for determining whether a collision will occur between the robot and an obstacle for a proposed movement being executed as said movement within said sequence of movements; and

generating means for generating a plan including said sequence of movements, by choosing, for each movement in said sequence of movements, a proposed movement that will not result in a collision and that will bring said robot closer to the goal position, said generating means comprising gross motion planning means for planning a gross motion plan including movements of said robot in the free-space and fine motion planning means for planning a fine-motion plan including movements of said robot to and from the bending apparatus.

35. The system according to claim 34, wherein said robot comprises a robot gripper for holding and maneuvering a workpiece throughout a sequence of bending operations to be performed by the bending apparatus.

36. The system according to claim 35, wherein:

said fine motion planning means comprises means for planning a plurality of free space fine motion solution paths that extend between a plurality of respective pairs of positions, q_i and q_g ; and

said gross motion planning means comprises means for planning a plurality of free space gross motion solution paths that extend between a plurality of respective pairs of positions, Q_i and Q_g.

37. The system according to claim 36, wherein said fine motion planning means comprises means for operating said proposing means, modeling means, determining means, and generating means, for each pair of positions q_i and q_g, said proposing means comprising specifying means for specifying a plurality of movements in configuration space for said movement in said sequence of movements and identifying means for identifying which ones of the specified plurality of movements are feasible by performing collision checking.

38. The system according to claim 36, wherein said gross motion planning means comprises means for operating said proposing means, modeling means, determining means and generating means, for each pair of positions Q_i and Q_q, said proposing means comprising means for proposing a set of movements within a maximal overlapping parallelepiped within the free space of said robot.

39. The system according to claim 36, wherein said gross motion planning means comprises means for operating said proposing means, modeling means, determining means and generating means, for each pair of positions Q_i and Q_g, said proposing means comprising means for proposing a set of movements within a maximal overlapping parallelepiped within the free space of said robot.

40. The system according to claim 35, further comprising:

calculating means for calculating whether a simple collision-free path can be determined;

forming means for forming a plan including movements for traversing the simple collision-free path; and

inhibiting means for inhibiting operation of said proposing means, determining means, and generating means.

41. The system according to claim 35, wherein said gross motion plan comprises movements of the robot from a loading position, where a workpiece is retrieved by the robot gripper, to a bending stage position of the bending apparatus.

42. The system according to claim 35, wherein said fine motion plan comprises movements of the robot for loading a workpiece held by the robot gripper into a die space defined between a punch tool and die of the bending apparatus.

43. The system according to claim 35, wherein said gross motion plan comprises movements of the robot for moving a workpiece held by the robot gripper from a first bending stage position to a second bending stage position of the bending apparatus.

44. The system according to claim 35, wherein said fine motion plan comprises movements of the robot for unloading a workpiece held by the robot gripper from a die space defined between a punch tool and die of the bending apparatus.

45. The system according to claim 35, wherein said gross motion plan comprises movements of the robot for moving a workpiece held by the robot gripper from a final bending stage position of the bending apparatus to an unloading position.

46. The system of claim 35, wherein said modeling means comprises means for modeling the workpiece held by the robot and said determining means comprises means for determining whether a collision will occur between the workpiece held by the robot and an obstacle for a proposed movement.

47. The system according to claim 34, further comprising estimating means for estimating a cost to be associated with each proposed movement, whereby said generating means comprise means for generating a plan including said sequence of movements, by choosing, for each movement in said sequence of movements, a proposed movement that will not result in a collision, that will bring the robot closer to the goal position, and that has a lowest estimated cost.

48. The system according to claim 47, wherein the estimated cost for a particular proposed movement comprises a Euclidian distance to the goal position from the position of the robot after said particular proposed movement is made as said movement in said sequence of movements.

49. The system according to claim 47, wherein the estimated cost for a particular proposed movement comprises an estimated value indicative of the robot'"'"'s travel time from an another movement to the position of the robot after said particular proposed movement is made as said mth movement.

50. The system according to claim 34, further comprising specifying means for specifying a plurality of movements in configuration space for said movement in said sequence of movements and identifying means for identifying which ones of the specified plurality of movements are feasible by performing collision checking, said proposing means comprising means for proposing movements from among the movements identified by said identifying means as feasible.

51. The system according to claim 50, wherein the specified plurality of movements specified for said movement in a sequence of movements comprises a plurality of movements and directions which collectively surround a position of the robot at the said another movement in said sequence of movements.

52. The system according to claim 50, wherein the specified plurality of movements for said movement in said sequence of movements comprises movements in a plurality of intelligent movement directions.

53. The system according to claim 52, said system further comprising means for planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a downward movement of said robot causing said workpiece to move downward.

54. The system according to claim 52, said system further comprising means for planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a backward movement of said robot causing said workpiece to be backed out of the bending apparatus.

55. The system according to claim 52, said system further comprising means for planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a movement of said robot causing said workpiece to change in pitch from an angled position towards a horizontal position.

56. The system according to claim 52, said system further comprising means for planning motion of said robot in order to unload a malleable workpiece from a tooling punch of the bending apparatus after completion of a bend, said intelligent directions comprising a movement of said robot causing said workpiece to be moved downward, to be moved backward and away from said bending apparatus, and to drop in pitch from an angled position towards a horizontal position.

57. The system according to claim 34, further comprising:

forming means for forming an m-tree representation of a work space of said robot; and

computing means for computing maximal overlapping rectangloids within the free space of said m-tree representation of said work space.

58. The method according to claim 57, wherein said m-tree representation is an octree representation.

59. The system according to claim 57, wherein said maximal overlapping rectangloids comprise maximal overlapping parallelepipeds.

60. The system according to claim 57, wherein said proposing means comprises means for proposing, for said movement in said sequence of movements, a set of movements of the robot to locations that fall within a maximal overlapping rectangloid within which the robot is located immediately after the another movement of said sequence of movements.

61. The system according to claim 60, wherein said set of movements comprises:

translating said robot to any one of eight corners of a present maximal overlapping rectangloid; and

moving said robot along any one of a plurality of predetermined directions which bring said robot to a position along a predetermined direction that corresponds to said goal position.

62. The system according to claim 60, wherein said set of movements comprises:

moving said robot in a first of three orthogonal directions to a position along the first orthogonal direction which corresponds to said goal position;

moving said robot in a second of the three orthogonal directions to a position along the second orthogonal direction which corresponds to said goal position;

moving said robot in a third of the three orthogonal directions to a position along the third orthogonal direction which corresponds to said goal position;

moving said robot in order to adjust a pitch of a gripper of said robot; and

moving said robot in order to adjust both the pitch and yaw of the gripper of said robot.

63. The system according to claim 60, wherein said set of movements comprises moving along one of a plurality of orthogonal directions only when the movement would bring the robot to an orthogonal position that corresponds to the goal position.

64. The system according to claim 34, further comprising means for integrating said gross motion plan with said fine motion plan to generate said plan.

65. The system according to claim 34, wherein said robot comprises a robot gripper for holding a workpiece, and said fine motion plan comprises movements of the robot for loading and unloading the workpiece into a die space defined by a punch tool and die of the bending apparatus.

66. The system of claim 34, wherein said free space is a 3-D space environment, said plurality of proposed movements including a 3-D movement to be made by the robot.