STEERING CONTROL DEVICE OF AUTONOMOUS VEHICLE, AUTONOMOUS VEHICLE HAVING THE SAME AND STEERING CONTROL METHOD OF AUTONOMOUS VEHICLE

• US 20120072075A1
• Filed: 09/28/2010
• Published: 03/22/2012
• Est. Priority Date: 05/11/2010
• Status: Active Grant

• Current Assignee: Agency For Defense Development (Government of The Republic of China)
• Original Assignee: Agency For Defense Development (Government of The Republic of China)
• Inventors: Choe, Tok Son, Park, Yong Woon, Chae, Jeong Sook
• Granted Patent: US 8,983,708 B2
• Time in Patent Office: Days
• US Class Current: 701/41
• CPC Class Codes: B62D 1/283 for unmanned vehicles
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence
• CPC Class Codes: G05D 1/021 specially adapted to land vehicles

Abstract

Disclosed are a steering control device of an autonomous vehicle, an autonomous vehicle having the same, and a steering control method of an autonomous vehicle. The steering control method comprises receiving a position of an autonomous vehicle, and a first heading angle of the autonomous vehicle with respect to the north; calculating a second heading angle of the autonomous vehicle toward a tracking waypoint based on the position of the autonomous vehicle, and computing a rotation radius of the autonomous vehicle with respect to the tracking waypoint; calculating a yaw rate based on a speed of the autonomous vehicle and the computed rotation radius, and generating a steering command corresponding to the calculated yaw rate; and compensating for the steering command based on the first and second heading angles.

Claims

1. A steering control method of an autonomous vehicle, the method comprising:

receiving a position of an autonomous vehicle, and a first heading angle of the autonomous vehicle with respect to north;

calculating a second heading angle of the autonomous vehicle toward a tracking waypoint based on the position of the autonomous vehicle, and computing a rotation radius of the autonomous vehicle with respect to the tracking waypoint;

calculating a yaw rate based on a speed of the autonomous vehicle and the computed rotation radius, and generating a steering command corresponding to the calculated yaw rate; and

compensating for the steering command based on the first and second heading angles.

2. The method of claim 1, wherein the step of generating a steering command is a step of generating a steering command corresponding to the calculated yaw rate based on a preset characteristic formula.

3. The method of claim 2, wherein the characteristic formula is a polynomial expression having the steering command and the yaw rate as an independent variable and a dependent variable, respectively, and a coefficient of the polynomial expression is calculated based on an output yaw rate measured on a road surface of a specific condition with respect to a steering command having undergone a sampling process within a predetermined range.

4. The method of claim 3, further comprising changing the preset characteristic formula into a specific ratio when the steering command or the compensated steering command corresponds to a maximum value within the predetermined range, in correspondence to a condition of a road surface on which the autonomous vehicle runs.

5. The method of claim 4, wherein the step of changing comprises:

a detecting step of detecting a current steering command, and comparing the current steering command with the maximum value within the predetermined range thereby detecting a maximum yaw rate corresponding to the maximum value; and

an updating step of updating the preset characteristic formula based on the maximum yaw rate, and a maximum output yaw rate obtained when the steering command having undergone a sampling process is maximized.

6. The method of claim 1, further comprising increasing or decreasing the steering command into a specific ratio in correspondence to a condition of a road surface on which the autonomous vehicle runs.

7. The method of claim 6, wherein the step of generating a steering command is a step of generating a steering command corresponding to the calculated yaw rate based on a preset polynomial expression,

wherein the step of increasing or decreasing the steering command is a step of increasing or decreasing the coefficient of the polynomial expression into a specific ratio,

wherein the polynomial expression is set based on a steering command having undergone a sampling process, and an output yaw rate of the autonomous vehicle is acquired by the steering command having undergone a sampling process, and

wherein the specific ratio is a ratio between a maximum output yaw rate corresponding to a maximum value of the steering command having undergone a sampling process, and a maximum yaw rate corresponding to a maximum vale of the steering command.

8. The method of claim 1, wherein the step of compensating is a step of adding, to the steering command, a value obtained by multiplying a difference between the first and second heading angles by a preset gain.

9. The method of claim 1, wherein the rotation radius is a radius of a circular arc formed by connecting the autonomous vehicle to the tracking waypoint.

10. A steering control device of an autonomous vehicle, the device comprising:

a waypoint selection unit for selecting a tracking waypoint of an autonomous vehicle based on a current position of the autonomous vehicle with using received waypoints;

a computation unit for calculating a second heading angle of the autonomous vehicle toward the tracking waypoint based on the position of the autonomous vehicle, and computing a rotation radius of the autonomous vehicle with respect to the tracking waypoint; and

a steering command generation unit for calculating a yaw rate based on a speed of the autonomous vehicle and the computed rotation radius, generating a steering command corresponding to the calculated yaw rate, and compensating for the steering command based on the second heading angle, and a first heading angle of the autonomous vehicle with respect to north.

11. The device of claim 10, wherein the steering command is generated by a preset characteristic formula,

wherein the characteristic formula is a polynomial expression having the steering command and the yaw rate as an independent variable and a dependent variable, respectively, and

wherein a coefficient of the polynomial expression is calculated based on an output yaw rate measured on a road surface of a specific condition with respect to a steering command having undergone a sampling process within a predetermined range.

12. The device of claim 11, wherein the steering command generation unit changes the preset characteristic formula into a specific ratio when the steering command or the compensated steering command corresponds to a maximum value within the predetermined range, in correspondence to a condition of a road surface on which the autonomous vehicle runs.

13. An autonomous vehicle, comprising:

a body configured to autonomously move and mounted with a driving means;

a receiver for receiving a position of the body, a first heading angle of the body with respect to north, and waypoints;

a steering control device for selecting one of the waypoints as a tracking waypoint based on the position of the body, and generating a steering command such that the body tracks the tracking waypoint; and

a driving controller for receiving the steering command, and controlling the driving means according to the received steering command,

wherein the steering control device calculates a second heading angle of the autonomous vehicle toward the tracking waypoint based on the position of the autonomous vehicle, and computes a rotation radius of the autonomous vehicle,

wherein the steering control device calculates a yaw rate based on a speed of the autonomous vehicle and the computed rotation radius, generates a steering command corresponding to the calculated yaw rate, and

wherein the steering control device compensates for the generated steering command based on the first and second heading angles.