Motion planner for unmanned ground vehicles traversing at high speeds in partially known environments

• US 7,734,387 B1
• Filed: 03/31/2006
• Issued: 06/08/2010
• Est. Priority Date: 03/31/2006
• Status: Expired due to Fees

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Young, Shih-Yih, Jerome, Kristen M.
• Primary Examiner(s): Hellner; Mark
• Assistant Examiner(s): Algahaim; Helal A
• Application Number:
  US11/394,403
• Time in Patent Office: 1,530 Days
• Field of Search: 701/23, 701/209, 701/301
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0214 in accordance with safety or protection criteria, e.g. avoiding hazardous areas monitoring the location of vehicles within a certain area, e.g. forbidden or allowed areas, in traffic control systems for road vehicles G08G1/13
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30
• CPC Class Codes: G05D 1/0278 using satellite positioning signals, e.g. GPS

Abstract

A motion planner for unmanned ground vehicles capable of traversing at high speeds to reach remote locations in partially known environments. The motion planner comprises a global path planner and a local path planner in communication with the global path planner. The global path planner determines a path to reach a goal location. The local motion planner revises the path determined by the global path planner to generate a motion profile accounting for constraints on the maneuverability of the unmanned ground vehicle. The motion profile provides a revised path for being traversed by the unmanned ground vehicle to reach the goal location.

Claims

1. A motion planner for an unmanned ground vehicle, comprising:

a global path planner configured to determine a path to reach a goal location, the path determined by the global path planner comprises a polygonal path, the polygonal path includes at least one discontinuity wherein the unmanned ground vehicle is required to change heading so that the polygonal path includes a first substantially straight path segment and a second substantially straight path segment, the second substantially straight path segment joining the first substantially straight path segment at the at least one discontinuity; and

a local motion planner in communication with the global path planner configured to revise the path determined by the global path planner to generate a motion profile accounting for at least one constraint on maneuverability of the unmanned ground vehicle,

said motion profile provides a revised path for being traversed by the unmanned ground vehicle to reach the goal location, the revised path created by the local motion planner comprises a smoothed path with at least one arc that complies with the at least one constraint on the maneuverability of the unmanned ground vehicle, the local motion planner creating the revised path based upon a curve speed of the unmanned ground vehicle following said at least one arc of the smoothed path and a turning rate of the unmanned ground vehicle, the curve speed of the unmanned ground vehicle being a highest speed following said at least one arc to avoid a rollover of the unmanned ground vehicle, the motion profile further including a speed profile whereby the unmanned ground vehicle decelerates to said curve speed while avoiding a rollover of the unmanned ground vehicle when beginning said at least one arc of the smoothed path and maintains said curve speed through said at least one arc.

2. The motion planner as claimed in claim 1, wherein the global path planner determines the path using predetermined terrain information and real-time sensor inputs.

3. The motion planner as claimed in claim 1, wherein the local motion planner determines three anchor points based on the polygonal path, the three anchor points being used for revising the polygonal path.

4. The motion planner as claimed in claim 3, wherein the three anchor points include a first anchor point comprising a current location of the unmanned ground vehicle or an end point of a previously saved motion profile, a second anchor point comprising a point at a distance from the at least one discontinuity of the polygonal path, and a third anchor point comprising a point on the second substantially straight path segment.

5. A method for planning a path for an unmanned ground vehicle, comprising:

determining a path, via a global path planner, to be traversed by the unmanned ground vehicle to reach a goal location, the determined path comprises a polygonal path, the polygonal path includes at least one discontinuity wherein the unmanned ground vehicle is required to change heading so that the polygonal path includes a first path substantially straight segment and a second substantially straight path segment, the second substantially straight path segment joining the first substantially straight path segment at the at least one discontinuity; and

generating a motion profile by revising the determined path to account for at least one constraint on maneuverability of the unmanned ground vehicle, the motion profile allowing traversal of a revised path by the unmanned ground vehicle to reach the goal location, the revised path comprises a smoothed path with at least one arc that complies with the at least one constraint on the maneuverability of the unmanned ground vehicle, the revised path based upon a curve speed of the unmanned ground vehicle following said at least one arc of the smoothed path and a turning rate of the unmanned ground vehicle;

wherein the unmanned ground vehicle is suitable to traverse the revised path at a speed greater than the speed at which the unmanned ground vehicle is suitable to traverse the determined path, the curve speed of the unmanned ground vehicle being a highest speed following said at least one arc to avoid a rollover of the unmanned ground vehicle, the motion profile further including a speed profile whereby the unmanned ground vehicle decelerates to said curve speed while avoiding a rollover of the unmanned ground vehicle when beginning said at least one arc of the smoothed path and maintains said curve highest speed through said at least one arc.

6. The method as claimed in claim 5, wherein the determined path to be traversed by the unmanned ground vehicle is determined using stored terrain information and real-time sensor inputs.

7. The method as claimed in claim 5, wherein revising the determined path comprises determining three anchor points based on the polygonal path, the three anchor points being used for revising the polygonal path.

8. The method as claimed in claim 7, wherein the three anchor points include a first anchor point comprising a current location of the unmanned ground vehicle or an end point of a previously saved motion profile, a second anchor point comprising a point at a distance from the at least one discontinuity, and a third anchor point comprising a point on the second substantially straight path segment.

9. An unmanned ground vehicle, comprising:

a global path planner configured to determine a path to be traversed by the unmanned ground vehicle to reach a goal location, the path determined by the global path planner comprises a polygonal path, the polygonal path including at least one discontinuity where the ground vehicle is required to change heading so that the polygonal path includes a first substantially straight path segment and a second substantially straight path segment, the second substantially straight path segment joining the first substantially straight path segment at the discontinuity; and

a local motion planner in communication with the global path planner configured to revise the path determined by the global path planner to generate a motion profile accounting for at least one constraint on maneuverability of the unmanned ground vehicle, the motion profile providing a revised path for being traversed by the unmanned ground vehicle to reach the goal location, the revised path comprises a smoothed path with at least one arc that complies with the at least one constraint on the maneuverability of the unmanned ground vehicle, the local motion planner creating the revised path based upon a curve speed of the unmanned ground vehicle following act the at least one arc of the smoothed path and a turning rate of the unmanned ground vehicle;

said unmanned ground vehicle is configured to traverse the revised path at a speed greater than the speed at which the unmanned ground vehicle is configured to traverse the path determined by the global path planner, the curve speed of the unmanned ground vehicle being a highest speed following said at least one arc to avoid a rollover of the unmanned ground vehicle, the motion profile further including a speed profile whereby the unmanned ground vehicle decelerates to said curve speed while avoiding a rollover of the unmanned ground vehicle when beginning said at least one arc of the smoothed path and maintains said curve speed through said at least one arc.

10. The unmanned ground vehicle as claimed in claim 9, wherein the global path planner determines the path using predetermined terrain information and real-time sensor inputs.

11. The unmanned ground vehicle as claimed in claim 9, wherein the local motion planner determines three anchor points based on the polygonal path, the three anchor points being used for revising the polygonal path.

12. The unmanned ground vehicle as claimed in claim 11, wherein the three anchor points include a first anchor point comprising a current location of the unmanned ground vehicle or an end point of a previously saved motion profile, a second anchor point comprising a point at a distance from the discontinuity of the polygonal path, and a third anchor point on the polygonal path.

13. The motion planner as claimed in claim 1, wherein said constraint on the maneuverability of the unmanned ground vehicle includes at least one of acceleration limit and deceleration limit.

14. The method as claimed in claim 5, wherein said constraint on the maneuverability of the unmanned ground vehicle includes at least one of acceleration limit and deceleration limit.

15. The unmanned ground vehicle as claimed in claim 9, wherein said constraint on the maneuverability of the unmanned ground vehicle includes at least one of acceleration limit and deceleration limit.