Line acquisition path generation using curvature profiles

• US 10,416,675 B2
• Filed: 04/10/2017
• Issued: 09/17/2019
• Est. Priority Date: 04/12/2016
• Status: Active Grant

• Current Assignee: Agjunction LLC (Kubota Corporation)
• Original Assignee: Agjunction LLC (Kubota Corporation)
• Inventors: Dang, Tri M., Sullivan, Timothy J., Medagoda, Eran D. B.
• Primary Examiner(s): Badii, Behrang
• Assistant Examiner(s): Greene, Daniel L
• Application Number:
  US15/483,524
• Publication Number:
  US 20170293304A1
• Time in Patent Office: 890 Days
• CPC Class Codes: A01B 69/006 derived from the steering of the tractor
• CPC Class Codes: A01B 69/008 automatic
• CPC Class Codes: B62D 15/029 Steering assistants using warnings or proposing actions to the driver without influencing the steering system
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G05D 1/021 specially adapted to land vehicles
• 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 1/0278 using satellite positioning signals, e.g. GPS

Abstract

A line acquisition system generates a curvature profile based on initial vehicle states (starting position, heading, curvature and speed), vehicle steering capabilities (calibrated vehicle curvature and curvature rate limits), and initial vehicle position errors relative to the destination path. The curvature profile describes changes in vehicle curvature over a path distance from a current position to a destination path. The line acquisition system constructs an acquisition path from a combination of clothoid, circular arc, and straight lines corresponding with different segments of the curvature profile. The acquisition path can be displayed on a user interface allowing a vehicle operator to observe, prior to automatic steering engagement, the path the vehicle would take from a current state to the destination path.

Claims

1. A line acquisition system for generating an acquisition path for a vehicle, comprising:

a hardware processor to;

identify a destination path;

identify a position of the vehicle;

identify a heading error between the destination path and the vehicle;

generate a curvature profile for turning the vehicle onto the destination path based on the heading error, the curvature profile including line segments for clothoid paths, circular arc paths, and straight line zero curvature paths; and

generate an acquisition path from the position of the vehicle to the destination path from the clothoid path, circular arc path, and zero curvature paths identified the in the curvature profile, wherein the processor is further configured to;

convert a current section of the curvature profile and a next section of the curvature profile with different curvatures into a clothoid section of the acquisition path,

convert a current section of the curvature profile with a zero curvature and a next section of the curvature profile with a same zero curvature into a straight line zero curvature section of the acquisition path; and

convert a current section of the curvature profile with a nonzero curvature and a next section of the curvature profile with a same nonzero curvature into a circular arc path section of the acquisition path.

2. The line acquisition system of claim 1, the processor further to:

identify an end location of the acquisition path; and

display the acquisition path on a user interface when the end location comes within the predetermine range of the destination path.

3. The line acquisition system of claim 1, wherein the processor is further to:

repeatedly generate new curvature profiles for new positions of the vehicle;

repeatedly generate new acquisition paths for the new curvature profiles;

display the new acquisition paths on a user interface;

receive an input selecting one of the new acquisition paths; and

automatically steer the vehicle along the selected one of the new acquisition paths to the destination path.

4. The line acquisition system of claim 1, wherein the processor is further to:

generate a line with a changing curvature value over path distance for the clothoid path segments;

generate a line with a constant non-zero curvature value over path distance for the circular path segments; and

generate a line with a constant zero curvature value over path distance for the zero curvature straight path segments.

5. The line acquisition system of claim 1, the processor further to:

generate a first section of the curvature profile that moves a current heading of the vehicle to an attack heading towards the destination path; and

generate a second section of the curvature profile that moves the vehicle from the attack heading onto the destination path.

6. The line acquisition system of claim 5, the processor further to:

generate the first section of the curvature profile so the vehicle has zero curvature at the attack heading;

identify an end point of the acquisition path; and

add a zero-curvature segment between the first and second section of the curvature profile when the end point is short of the destination path.

7. The line acquisition system of claim 6, the processor further to:

identify a lateral error between the end point of the acquisition path and the destination path; and

use the lateral error as a path distance for the zero-curvature segment.

8. The line acquisition system of claim 5, the hardware processor further to:

reduce the attack heading when an end point of the acquisition path overshoots the destination path;

generate a new curvature profile with the reduced attack heading;

generate a new acquisition path from the new curvature profile; and

repeatedly reduce the attack heading and generate new curvature profiles and new acquisition paths until the end point comes within a predetermine range of the destination path.

9. The line acquisition system of claim 8, the processor further to start with an initial attack heading of 90 degrees to the destination path.

10. A computer program for generating an acquisition path from a vehicle to a destination path, the computer program comprising a set of instructions operable to:

identify a heading error between the vehicle and the destination path;

generate a curvature profile based on the heading error that includes segments representing different vehicle curvatures over a path distance of the vehicle, the curvature profile including clothoid, circular arc, and zero curvature segments aligning the vehicle with the destination path;

generate an acquisition path based on the curvature profile; and

display the acquisition path on a user interface.

11. The computer program of claim 10, wherein the instructions are further operable to:

detect a selection of the acquisition path displayed on the user interface; and

automatically steer the vehicle along the acquisition path onto the destination path based on the selection.

12. The computer program of claim 10, wherein the instructions are further operable to:

generate a first segment of the curvature profile that turns the vehicle to an attack heading towards the destination path with a zero curvature; and

generate a second segment of the curvature profile that turns the vehicle from the attack heading to a heading of the destination path.

13. The computer program of claim 12, wherein the instructions are further operable to insert a zero curvature segment between the first and second segment of the curvature profile when an endpoint of the acquisition path is short of the destination path.

14. The computer program of claim 12, wherein the instructions are further operable to reduce the attack heading when an endpoint of the acquisition path overshoots the acquisition path.

15. The computer program of claim 10, wherein the instructions are further operable to:

generate a first segment for the curvature profile to change the vehicle curvature to a clothoid in a first direction;

generate a second segment for the curvature profile to change the vehicle curvature to a circular arc in the first direction; and

generate a third segment of the curvature profile to change the vehicle curvature to a zero curvature.

16. The computer program of claim 15, wherein the instructions are further operable to:

generate a fourth segment for the curvature profile to change the vehicle curvature to a clothoid in a second direction;

generate a fifth segment for the curvature profile to change the vehicle curvature to a circular arc in the second direction; and

generate a sixth segment of the curvature profile to change the vehicle curvature to a zero curvature in a same heading as the destination path.

17. The computer program of claim 15, wherein the instructions are further operable to:

identify an initial curvature of the vehicle as being in a direction away from the required direction of acquisition; and

generate an initial segment for the curvature profile before the first segment to change the initial vehicle curvature from the initial direction to a zero curvature.

18. A method for generating a curvature profile for changing a heading of a vehicle, comprising:

determining a heading error between a current heading of the vehicle and a destination path;

deriving a first portion of the curvature profile based on the heading error that turns the vehicle from the current heading to an attack heading toward the destination path;

deriving a second portion of the curvature profile that turns the vehicle from the attack heading to a heading substantially aligning with the destination path, the curvature profile including a combination of lines with;

a clothoid with varying curvature values over a path distance, constant non-zero curvature over a path distance, and constant zero curvature over a path distance; and

generating an acquisition path from the curvature profile.

19. The method of claim 18, including deriving the first portion and second portion of the curvature profile so an area underneath the curvature profile removes the heading error.

20. The method of claim 18, further comprising:

identifying an end point of the acquisition path;

inserting a zero-curvature segment between the first and second portion of the curvature profile when the end point is short of the destination path; and

reducing the attack heading and derive new first and second portions of the curvature profile with the reduced attack heading when the end point overshoots the destination path.