System for efficient scheduling for multiple automated non-holonomic vehicles using a coordinated path planner

• US 9,958,873 B2
• Filed: 10/13/2015
• Issued: 05/01/2018
• Est. Priority Date: 04/11/2011
• Status: Active Grant

• Current Assignee: Crown Equipment Corporation
• Original Assignee: Crown Equipment Corporation
• Inventors: Thomson, Jacob Jay
• Primary Examiner(s): WHITTINGTON, JESS G
• Application Number:
  US14/881,511
• Publication Number:
  US 20160033971A1
• Time in Patent Office: 931 Days
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G05D 1/0212 with means for defining a desired trajectory involving a plurality of land vehicles G05D1/0287
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30
• CPC Class Codes: G05D 1/0289 with means for avoiding collisions between vehicles vehicle fittings for automatically controlling speed including means for detecting potential obstacles B60K31/0008; avoiding obstacles by action on the steering system B62D; radar, sonar, lidar systems designed for anti-collision purposes G01S13/93, G01S15/93, G01S17/93
• CPC Class Codes: G05D 1/0291 Fleet control monitoring fleets in traffic control systems for road vehicles G08G1/127, G08G1/127
• CPC Class Codes: G05D 1/0297 by controlling means in a control room

Abstract

A method for coordinating path planning for one or more automated vehicles is described, including querying an online path planner for possible solutions for at least one executable task for each of the one or more automated vehicles, examining the results of the query, deciding a coordinated path plan for each vehicle, and communicating the coordinated path plan to a traffic manager, wherein the traffic manager ensures that the one or more automated vehicles perform each executable task according to the coordinated path plan.

Claims

1. A system for coordinated path planning in a multivehicle warehouse environment, the system comprising a plurality of automated vehicles for moving a product around the multivehicle warehouse and one or more central processing units, wherein:

each automated vehicle of the plurality of automated vehicles comprises a memory comprising a navigation module; and

the one or more central processing units are communicatively coupled to the plurality of automated vehicles and execute instructions to;

receive an executable task in the multivehicle warehouse for one or more of the plurality of automated vehicles,

select a coordinated path plan for a number of the plurality of automated vehicles for which the executable task has been received, wherein the coordinated path plan is selected with the one or more central processing units from a solution set of roadmap graphs from a multi-level graph, the multi-level graph comprising a plurality of graph levels with respect to a floor portion of the multivehicle warehouse, the plurality of graph levels comprising at least a higher level graph of the floor portion and a lower level graph of the floor portion, the higher level graph comprising a plurality of high-level nodes, the lower level graph comprising a plurality of lower-level nodes, each lower-level node disposed in a position within or on a boundary of a respective high-level node of the plurality of high-level nodes, each lower-level node comprising a smaller surface area than the respective high-level node with respect to the floor portion, and the solution set of roadmap graphs comprising one or more unique combinations of lower-level nodes and high-level nodes and path segments connection various ones of the lower-level nodes and the high-level nodes,

communicate at least a portion of the coordinated path plan to the number of the plurality of automated vehicles for which the executable task has been received such that respective navigation modules of the number of the plurality of automated vehicles navigate a respective automated vehicle, according to the received portion of the coordinated path plan,

receive an up-coming executable task in the multivehicle warehouse for one or more of the plurality of automated vehicles,

use the up-coming executable task to forecast a revised coordinated path plan for the number of the plurality of automated vehicles operating according to the received portion of the coordinated path plan, and

communicate at least a portion of the revised coordinated path plan to the number of the plurality of automated vehicles for which the up-coming executable task has been received such that, upon receipt of instructions to execute the up-coming executable task, respective navigation modules of the number of the plurality of automated vehicles navigate the respective automated vehicle, according to the received portion of the revised coordinated path plan.

2. The system as claimed in claim 1 wherein the one or more central processing units execute instructions to monitor the plurality of automated vehicles to ensure the plurality of automated vehicles are performing each executable task according to the coordinated path plan or the revised coordinated path plan.

3. The system as claimed in claim 1 wherein the one or more central processing units are communicatively coupled to the plurality of automated vehicles through a network.

4. The system as claimed in claim 1 wherein the one or more central processing units execute instructions to:

access the multi-level graph comprising high-level nodes, wherein the high-level nodes each correspond to a region of the multivehicle warehouse, each of the high level nodes comprises one or more lower-level nodes and one or more local paths, wherein;

the one or more lower-level nodes comprise one or more connection nodes corresponding to a boundary of the region, and one or more roadmap nodes corresponding to an interior of the region, and

the one or more local paths link the connection nodes, the roadmap nodes, or a combination thereof;

construct, with the one or more central processing units, a grid associated with the multivehicle warehouse, wherein the grid demarcates a plurality of grid squares, and respective grid squares contain a portion of the multivehicle warehouse and a portion of the corresponding multi-level graph;

select from the plurality of grid squares, with the one or more central processing units, grid squares corresponding to a start position, a goal position, or both, if the start position, the goal position, or both, are within the multivehicle warehouse but off the multi-level graph;

determine within one or more of the selected grid squares, with the one or more central processing units, joining paths from the start position, the goal position, or both, to the multi-level graph;

construct, with the one or more central processing units, the solution set of roadmap graphs from the multi-level graph, wherein each of the roadmap graphs comprises the start position linked via a final path to the goal position, and the final path comprises a determined joining path and at least a portion of the local paths.

5. The system as claimed in claim 4 wherein the one or more central processing units execute instructions to:

generate a list of blocked nodes corresponding to the high-level nodes, the connection nodes, and roadmap nodes that are unavailable; and

stop the plurality of automated vehicles from navigating a part of the region corresponding the blocked nodes.

6. The system as claimed in claim 4 wherein the one or more central processing units execute instructions to constrain a number of the plurality of automated vehicles permitted within each of the high-level nodes to reduce the time needed to construct a solution set of roadmap graphs.

7. The system as claimed in claim 4 wherein the number of the plurality of automated vehicles permitted within each of the high-level nodes is two or less.

8. The system as claimed in claim 4 wherein the one or more central processing units execute instructions to:

stop operation of the plurality of automated vehicles at a predetermined time; and

resume operation of the plurality of automated vehicles after a period of time has elapsed after the predetermined time, wherein the coordinated path plan is selected during the period of time.

9. The system as claimed in claim 4 wherein the one or more central processing units execute instructions to form a modified-Dubins path comprising joining paths at ends of the modified-Dubins paths and a continuous change in curvature path located between the joining paths, wherein the modified-Dubins path comprises sharper turns than the continuous change in curvature path, and the one or more local paths of one of the roadmap graphs comprises the modified-Dubins path.

10. The system as claimed in claim 4 wherein the determined joining path of one of the plurality of automated vehicles does not intersect with the start position and the goal position of one or more of the roadmap graphs for another automated vehicle of the plurality of automated vehicles.

11. The system as claimed in claim 4 wherein the coordinated path plan requires one of the plurality of automated vehicles to wait until another of the plurality of automated vehicles passes a specific location.

12. The system as claimed in claim 4 wherein the one or more central processing units execute instructions to remove at least a portion of the roadmap graphs from the solution set of roadmap graphs based at least in part upon a heuristic of each removed portion of the roadmap graphs.

13. The system as claimed in claim 12 wherein the heuristic is indicative of travel time.

14. The system as claimed in claim 12 wherein the heuristic is indicative of cost associated with start-up of an idled vehicle of the plurality of automated vehicles.

15. The system as claimed in claim 12 wherein the heuristic is indicative of the high-level nodes, the connection nodes, and roadmap nodes that are unavailable.

16. The system as claimed in claim 4 wherein the one or more central processing units execute instructions to identify respective connection nodes, roadmap nodes, or local paths which correspond to the start position, the goal position, or both, if the start position, the goal position, or both are within the multivehicle warehouse and on the multi-level graph.

17. The system as claimed in claim 1 wherein the plurality of automated vehicles are non-holonomic.

18. The system as claimed in claim 1 wherein the floor portion of the multivehicle warehouse comprises a floor area of a floor, the floor area comprising:

one or more ramp portions, at least two levels comprising different elevations, or both.

19. A system for coordinated path planning in a multivehicle warehouse environment, the system comprising a plurality of automated vehicles for moving a product around the multivehicle warehouse and one or more central processing units, wherein:

each automated vehicle comprises a memory comprising a navigation module; and

the one or more central processing units are communicatively coupled to the plurality of automated vehicles and execute instructions to;

receive executable tasks in the multivehicle warehouse for one or more of the plurality of automated vehicles,

select a coordinated path plan for a number of the plurality of automated vehicles for which executable tasks have been received, wherein the coordinated path plan is selected with the one or more central processing units from a solution set of roadmap graphs from a multi-level graph, the multi-level graph comprising a plurality of graph levels with respect to a floor portion of the multivehicle warehouse, the plurality of graph levels comprising at least a higher level graph of the floor portion and a lower level graph of the floor portion, the higher level graph comprising a plurality of high-level nodes, the lower level graph comprising a plurality of lower-level nodes, each lower-level node disposed in a position within or on a boundary of a respective high-level node of the plurality of high-level nodes, each lower-level node comprising a smaller surface area than the respective high-level node with respect to the floor portion, and the solution set of roadmap graphs comprising one or more unique combinations of lower-level nodes and high-level nodes and path segments connection various ones of the lower-level nodes and the high-level nodes,

construct, with the one or more central processing units, a grid associated with the multivehicle warehouse, wherein the grid demarcates a plurality of grid squares, and respective grid squares contain a portion of the multivehicle warehouse and a portion of the corresponding multi-level graph;

select from the plurality of grid squares, with the one or more central processing units, grid squares corresponding to a start position, a goal position, or both, if the start position, the goal position, or both, are within the multivehicle warehouse but off the multi-level graph;

determine within one or more of the selected grid squares, with the one or more central processing units, joining paths from the start position, the goal position, or both, to the multi-level graph,

wherein each of the roadmap graphs comprises the start position linked via a final path to the goal position, the final path comprises a determined joining path and at least a portion of the local paths, and the coordinated path plan for the automated vehicles is selected from the solution set of roadmap graphs;

communicate at least a portion of the coordinated path plan to the number of the plurality of automated vehicles for which executable tasks have been received such that respective navigation modules of the number of the plurality of automated vehicles navigate a respective automated vehicle, according to the received portion of the coordinated path plan,

receive up-coming executable tasks in the multivehicle warehouse for one or more of the plurality of automated vehicles,

use the up-coming executable tasks to forecast a revised coordinated path plan for the number of the plurality of automated vehicles operating according to the received portion of the coordinated path plan, and

communicate at least a portion of the revised coordinated path plan to the number of the plurality of automated vehicles for which up-coming executable tasks have been received such that, upon receipt of instructions to execute up-coming executable tasks, respective navigation modules of the number of the plurality of automated vehicles navigate the respective automated vehicle, according to the received portion of the revised coordinated path plan.