Vehicle trajectory optimization for autonomous vehicles

• US 9,405,293 B2
• Filed: 05/30/2014
• Issued: 08/02/2016
• Est. Priority Date: 05/30/2014
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan North America Incorporated (Nissan Motor Co., Ltd.)
• Inventors: Meuleau, Nicolas
• Primary Examiner(s): Khatib, Rami
• Assistant Examiner(s): BOOMER, JEFFREY C
• Application Number:
  US14/291,411
• Publication Number:
  US 20150345959A1
• Time in Patent Office: 795 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B60W 30/18145 Cornering
• CPC Class Codes: B62D 15/00 Steering not otherwise provided for
• CPC Class Codes: B62D 15/025 Active steering aids, e.g. helping the driver by actively influencing the steering system after environment evaluation B62D1/28 takes precedence
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 21/34 Route searching; Route guidance
• CPC Class Codes: G01C 21/3453 Special cost functions, i.e. other than distance or default speed limit of road segments
• 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 1/0217 in accordance with energy consumption, time reduction or distance reduction criteria
• CPC Class Codes: G05D 1/0268 using internal positioning means
• CPC Class Codes: G05D 1/0278 using satellite positioning signals, e.g. GPS
• CPC Class Codes: G06Q 10/047 Optimisation of routes or paths, e.g. travelling salesman problem

Abstract

A method for controlling an autonomous vehicle includes obtaining information describing a roadway; defining a plurality of layers along the roadway between a starting position and a goal position, each layer having a first width, and each layer having a plurality of nodes that are spaced from one another transversely with respect to the roadway within the first width; and determining a first trajectory from the starting position to the goal position, by minimizing a cost value associated with traversing the layers. Determining the first trajectory includes, for each layer, determining layer-specific weighting factors for each of a plurality of cost components, based on information associated with the respective layer, and determining, for each node of the respective layer, a cost for travelling to one or more of the nodes in a subsequent layer based on the plurality of cost components and the layer-specific weighting factors.

Claims

1. A method for controlling an autonomous vehicle, comprising:

obtaining, by one or more processors, information describing a roadway from a starting position to a goal position;

defining, by the one or more processors, a plurality of layers along the roadway at spaced locations between the starting position and the goal position, each layer having a respective first width, and each layer having a plurality of nodes that are spaced from one another transversely with respect to the roadway within the respective first width;

determining, by the one or more processors, a trajectory from the starting position to the goal position, by minimizing a cost value associated with traversing the layers, including, for each layer;

obtaining a plurality of cost components;

obtaining information associated with the respective layer;

determining layer-specific weighting factors for each of the plurality of cost components, based on the information associated with the respective layer, and

determining, for each node of the respective layer, a cost for travelling to one or more of the nodes in a subsequent layer based on the plurality of cost components and the layer-specific weighting factors;

defining a plurality of refinement layers along the roadway at spaced locations between the starting position and the goal position, each refinement layer having a respective second width that extends transversely outward from the trajectory and is less than or equal to a transverse width between transversely adjacent pairs of the nodes from each layer of the plurality of layers, and each layer having a plurality of refinement nodes that are spaced from one another transversely with respect to the roadway;

modifying the trajectory by minimizing a cost value associated with traversing the refinement layers, wherein modifying the trajectory includes, for each refinement layer;

determining refinement layer-specific weighting factors for each of a plurality of refinement cost components, based on information associated with the respective refinement layer, and

determining, for each refinement node of the respective refinement layer, a cost for travelling to one or more of the refinement nodes in a subsequent refinement layer based on the plurality of refinement cost components and the refinement layer-specific weighting factors;

outputting a steering control signal based on the trajectory to a steering device for controlling operation of the steering device; and

changing a steering angle of at least one steered wheel using the steering device in response to the steering control signal.

2. The method of claim 1, wherein the plurality of cost components includes a distance travelled value, wherein the distance travelled value represents travelling to a respective one of nodes in the subsequent layer.

3. The method of claim 1, wherein the plurality of cost components includes a cross-track error value representing a transverse distance of each node from a central track of the roadway.

4. The method of claim 1, wherein the plurality of cost components includes a lateral acceleration value.

5. The method of claim 1, wherein the information associated with the respective layer includes environmental information describing the roadway adjacent to the respective layer.

6. A control apparatus for an autonomous vehicle, comprising:

one or more processors; and

one or more memory devices for storing program instructions used by the one or more processors, wherein the program instructions, when executed by the one or more processors, cause the one or more processors to;

obtain information describing a roadway from a starting position to a goal position;

define a plurality of layers along the roadway at spaced locations between the starting position and the goal position, each layer having a respective first width, and each layer having a plurality of nodes that are spaced from one another transversely with respect to the roadway within the respective first width; and

determine a trajectory from the starting position to the goal position, by minimizing a cost value associated with traversing the layers, including, for each layer;

obtaining a plurality of cost components,

obtaining information associated with the respective layer,

determining layer-specific weighting factors for each of the plurality of cost components, based on the information associated with the respective layer, and

determining, for each node of the respective layer, a cost for travelling to one or more of the nodes in a subsequent layer based on the plurality of cost components and the layer-specific weighting factors;

define a plurality of refinement layers along the roadway at spaced locations between the starting position and the goal position, each refinement layer having a respective second width that extends transversely outward from the trajectory and is less than or equal to a transverse width between transversely adjacent pairs of the nodes from each layer of the plurality of layers, and each layer having a plurality of refinement nodes that are spaced from one another transversely with respect to the roadway;

modify the trajectory by minimizing a cost value associated with traversing the refinement layers, wherein modifying the trajectory includes, for each refinement layer;

determining refinement layer-specific weighting factors for each of a plurality of refinement cost components, based on information associated with the respective refinement layer, and

determining, for each refinement node of the respective refinement layer, a cost for travelling to one or more of the refinement nodes in a subsequent refinement layer based on the plurality of refinement cost components and the refinement layer-specific weighting factors;

output a steering control signal based on the trajectory to a steering device for controlling operation of the steering device; and

change a steering angle of at least one steered wheel using the steering device in response to the steering control signal.

7. The control apparatus of claim 6, wherein the plurality of cost components includes a distance travelled value, wherein the distance travelled value represents travelling to a respective one of nodes in the subsequent layer.

8. The control apparatus of claim 6, wherein the plurality of cost components includes a cross-track error value representing a transverse distance of each node from a central track of the roadway.

9. The control apparatus of claim 6, wherein the plurality of cost components includes a lateral acceleration value.

10. The control apparatus of claim 6, wherein the information associated with the respective layer includes environmental information describing the roadway adjacent to the respective layer.

11. An autonomous vehicle, comprising:

a trajectory planning system that includes one or more processors and one or more memory devices for storing program instructions used by the one or more processors, wherein the program instructions, when executed by the one or more processors, cause the one or more processors to;

obtain information describing a roadway from a starting position to a goal position,

define a plurality of layers along the roadway at spaced locations between the starting position and the goal position, each layer having a respective first width, and each layer having a plurality of nodes that are spaced from one another transversely with respect to the roadway within the respective first width,

determine a trajectory from the starting position to the goal position, by minimizing a cost value associated with traversing the layers, including, for each layer, obtaining a plurality of cost components, obtaining information associated with the respective layer, determining layer-specific weighting factors for each of a plurality of cost components, based on information associated with the respective layer, and determining, for each node of the respective layer, a cost for travelling to one or more of the nodes in a subsequent layer based on the plurality of cost components and the layer-specific weighting factors,

define a plurality of refinement layers along the roadway at spaced locations between the starting position and the goal position, each refinement layer having a respective second width that extends transversely outward from the trajectory and is less than or equal to a transverse width between transversely adjacent pairs of the nodes from each layer of the plurality of layers, and each layer having a plurality of refinement nodes that are spaced from one another transversely with respect to the roadway,

modify the trajectory by minimizing a cost value associated with traversing the refinement layers, including, for each refinement layer, determining refinement layer-specific weighting factors for each of a plurality of refinement cost components based on information associated with the respective refinement layer, and determining, for each refinement node of the respective refinement layer, a cost for travelling to one or more of the refinement nodes in a subsequent refinement layer based on the plurality of refinement cost components and the refinement layer-specific weighting factors, and

generate an output signal based on the trajectory;

a steering device that is operable to change a steering angle of at least one steered wheel; and

a steering control system operable to receive the output signal from the trajectory planning system and output a steering control signal based on the output signal to the steering device for controlling operation of the steering device, wherein the steering device changes the steering angle of the at least one steered wheel in response to the steering control signal.

12. The autonomous vehicle of claim 11, wherein the plurality of cost components includes a distance travelled value, wherein the distance travelled value represents travelling to a respective one of nodes in the subsequent layer.

13. The autonomous vehicle of claim 11, wherein the plurality of cost components includes a cross-track error value representing a transverse distance of each node from a central track of the roadway.

14. The autonomous vehicle of claim 11, wherein the plurality of cost components includes a lateral acceleration value.

15. The autonomous vehicle of claim 11, wherein the information associated with the respective layer includes environmental information describing the roadway adjacent to the respective layer.