Method for planning/controlling robot motion

• US 5,889,926 A
• Filed: 07/22/1997
• Issued: 03/30/1999
• Est. Priority Date: 11/09/1994
• Status: Expired due to Term

• Current Assignee: Amada America, Inc. (Amada Company Limited), 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:
  US08/898,551
• Time in Patent Office: 616 Days
• Field of Search: 395/90, 364/461
• 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 method comprising:

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

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

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

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; and

estimating a cost to be associated with each proposed movement, whereby said generating 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 said robot closer to the goal position, and that has a lowest estimated cost.

2. The method according to claim 1, wherein the estimated cost for a particular proposed movement comprises a Euclidian distance to the goal position from the position of said robot after said particular proposed movement is made in said sequence of movements.

3. The method according to claim 1, wherein the estimated cost for a particular proposed movement comprises an estimated value indicative of a robot travel time to move from a position after another movement is made to a position of said robot after said particular proposed movement is made.

4. 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 method comprising:

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

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

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

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; and

specifying, before proposing a plurality of proposed movements, 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 comprising proposing movements from among the movements identified as feasible, and said specified plurality of movements for said movement in said sequence of movements comprising movements in a plurality of intelligent movement directions.

5. The method according to claim 4, said method including planning motion of said robot in order to unload a malleable workpiece from a tooling punch of a bending apparatus after completion of a bend, said intelligent directions comprising a downward movement of said robot causing said workpiece to move downward.

6. The method according to claim 4, said method including planning motion of said robot in order to unload a malleable workpiece from a tooling punch of a 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.

7. The method according to claim 4, said method including planning motion of said robot in order to unload a malleable workpiece from a tooling punch of a 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.

8. The method according to claim 4, said method including planning motion of said robot in order to unload a malleable workpiece from a tooling punch of a 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.

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

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

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

a determining module that determines whether a collision will occur between said robot and any of said obstacles for a proposed movement being executed as said movement within said sequence of movements;

a generating module that generates a plan including said sequence of movements, by choosing, for each movement within said sequence of movements, a proposed movement that will not result in the collision that will bring said robot closer to the goal position; and

an estimating module that estimates a cost to be associated with each proposed movement, whereby said generating module comprises 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.

10. The system according to claim 9, wherein the estimated cost for a particular proposed movement comprises a Euclidian distance to the goal position from the position of said robot after said particular proposed movement is made within said sequence of movements.

11. The system according to claim 9, wherein the estimated cost for a particular proposed movement comprises an estimated value indicative of a robot travel time from another movement to the position of said robot after said particular proposed movement is made as said movement in said sequence of movements.

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

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

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

a determining module that determines whether a collision will occur between said robot and any of said obstacles for a proposed movement being executed as said movement within said sequence of movements;

a generating module that generates a plan including said sequence of movements, by choosing, for each movement within said sequence of movements, a proposed movement that will not result in the collision that will bring said robot closer to the goal position; and

a specifying module for specifying a plurality of movements in configuration space for said movement in said sequence of movements, said specifying module including identifying means for identifying which ones of the specified plurality of movements are feasible by performing collision checking, said proposing module comprising means for proposing movements from among the movements identified by said identifying means as feasible, and said specified plurality of movements for said movement in said sequence of movements comprising movements in a plurality of intelligent movement directions.

13. The system according to claim 12, said system further comprising a planning system that plans motion of said robot in order to unload a malleable workpiece from a tooling punch of a bending apparatus after completion of the bend, said intelligent directions comprising a downward movement of said robot causing said workpiece to move downward.

14. The system according to claim 12, said system further comprising a planning system that plans motion of said robot in order to unload a malleable workpiece from a tooling punch of a bending apparatus after completion of the bend, said intelligent directions comprising a backward movement of said robot causing said workpiece to be backed out of the bending apparatus.

15. The system according to claim 12, said system further comprising a planning system that plans motion of said robot in order to unload a malleable workpiece from a tooling punch of a bending apparatus after completion of the 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.

16. The system according to claim 12, said system further comprising a planning system that plans motion of said robot in order to unload a malleable workpiece from a tooling punch of a bending apparatus after completion of the bend, said intelligent directions comprising a movement of said robot causing said workpiece to move downward, to be moved backward and away from said bending apparatus, and to drop in a pitch from an angled position towards a horizontal position.