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

Patent metadata

Field	Value
Publication number	US-9958873-B2
Application number	US-201514881511-A
Country	US
Kind code	B2
Filing date	Oct 13, 2015
Priority date	Apr 11, 2011
Publication date	May 1, 2018
Grant date	May 1, 2018

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.

First claim

What is claimed is:

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 c

Assignees

• Crown Equipment Ltd
• Crown Equip Corp

Inventors

• Thomson Jacob Jay

Classifications

• G01C21/206 Primary

  specially adapted for indoor navigation · CPC title

• G05D1/0289

  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 title

• G05D1/0274

  using mapping information stored in a memory device (navigation using map-matching G01C21/30) · CPC title

• G05D1/0212

  with means for defining a desired trajectory (involving a plurality of land vehicles G05D1/0287) · CPC title

• G05D2201/0216

  Physics · mapped topic