System and method for vehicle steering control

• US 9,499,197 B2
• Filed: 10/15/2014
• Issued: 11/22/2016
• Est. Priority Date: 10/15/2014
• Status: Active Grant

• Current Assignee: Han-Shue Tan, Hua-chuang Automobile Information Technical Center Co., Ltd., Jihua Huang
• Original Assignee: Han-Shue Tan, Hua-chuang Automobile Information Technical Center Co., Ltd., Jihua Huang
• Inventors: Tan, Han-Shue, Huang, Jihua
• Primary Examiner(s): HOLLOWAY, JASON R
• Application Number:
  US14/515,006
• Publication Number:
  US 20160107682A1
• Time in Patent Office: 769 Days
• US Class Current: 1/1
• CPC Class Codes: B60T 2201/022 Collision avoidance systems
• CPC Class Codes: B60T 2201/08 Lane monitoring; Lane Keeping Systems
• CPC Class Codes: B60W 2554/00 Input parameters relating to objects
• CPC Class Codes: B60W 30/00 Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
• CPC Class Codes: B60W 30/095 Predicting travel path or likelihood of collision
• CPC Class Codes: B60W 30/18163 Lane change; Overtaking manoeuvres
• 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: B62D 15/0255 Automatic changing of lane, e.g. for passing another vehicle
• CPC Class Codes: B62D 15/0265 Automatic obstacle avoidance by steering
• CPC Class Codes: B62D 6/00 Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits means for initiating a change in direction B62D1/00; steering valves B62D5/06; combined with means for inclining the vehicle body or wheels on bends B62D9/00
• CPC Class Codes: G05D 1/0212 with means for defining a desired trajectory involving a plurality of land vehicles G05D1/0287

Abstract

A method for steering control of a vehicle having an actuator which turns steered wheels of the vehicle. The steering control method includes obtaining a location of a target point at a look-ahead distance away from the vehicle based on a maneuver the vehicle is performing, predicting a forward location of the vehicle at the look-ahead distance away from the vehicle, determining a distance between the location of the target point and the forward location, computing a normalized error by dividing the distance with the look-ahead distance, and determining a steering control command based on an integration of the normalized error. The actuator then turns the steered wheels of the vehicle according to the steering control command so as to steer the vehicle to perform various maneuvers.

Claims

1. A method for steering control of a vehicle having an actuator which turns steered wheels of the vehicle, comprising:

obtaining a location of a target point at a look-ahead distance away from the vehicle;

predicting a forward location of the vehicle, wherein the forward location is at the look-ahead distance away from the vehicle;

determining an error as a distance between the location of the target point and the forward location;

computing a normalized error by dividing the error with the look-ahead distance;

determining a steering control command based on an integration of the normalized error; and

outputting the steering control command to the actuator, wherein the actuator turns the steered wheels according to the steering control command so as to steer the vehicle to perform various maneuvers.

2. The method of claim 1 determining the look-ahead distance based on at least one of the following:

vehicle speed, vehicle rotating speed, vehicle lateral acceleration, vehicle steering angle, a curvature of the lane, a distance to a lane boundary, a distance to an obstacle, the normalized error, the distance between the location of the target point and the forward location, and the maneuver.

3. The method of claim 1, wherein the look-ahead distance is a linear function of vehicle speed.

4. The method of claim 1 obtaining the location of the target point by

locating the target point based on a maneuver the vehicle is performing, wherein

the target point is located at an offset, including zero offset, to a lane centerline of the lane the vehicle is traveling in when the vehicle is performing a lane keeping maneuver;

the target point is located at an offset, including zero offset, to a lane centerline of the lane the vehicle is changing to when the vehicle is performing a lane change maneuver;

the target point is located at an offset, including zero offset, to a lane centerline of the lane the vehicle is turning to when the vehicle is performing a left turn maneuver or a right turn maneuver; and

computing the location of the target point based on the lane centerline, the offset, and the look-ahead distance.

5. The method of claim 1 predicting the forward location of the vehicle by assuming that the vehicle maintains its current speed and rotating speed while traveling the look-ahead distance, wherein the current rotating speed is determined based on at least one of the following:

vehicle current yaw rate and vehicle current steering angle.

6. The method of claim 1 predicting the forward location of the vehicle by assuming the vehicle maintains its current speed and steering angle while traveling the look-ahead distance.

7. A method for steering control of a vehicle having an actuator which turns steered wheels of the vehicle, comprising:

obtaining a target line ahead of the vehicle based on a maneuver the vehicle is performing;

predicting a forward location of the vehicle, wherein the forward location is at the look-ahead distance away from the vehicle;

determining an error as a distance from the forward location to the target line;

computing a normalized error by dividing the error with the look-ahead distance;

determining a steering control command based on an integration of the normalized error;

outputting the steering control command to the actuator, wherein the actuator turns the steered wheels according to the steering control command so as to steer the vehicle to perform the maneuver.

8. The method of claim 7 determining the look-ahead distance based on at least one of the following:

vehicle speed, vehicle rotating speed, vehicle lateral acceleration, vehicle steering angle, a curvature of the lane, a distance to a lane boundary, a distance to an obstacle, the normalized error, the distance from the forward location to the target line, and the maneuver.

9. The method of claim 7 obtaining the target line by

locating the target line based on the maneuver, wherein

the target line is at an offset, including zero offset, to a lane centerline of the lane the vehicle is traveling in when the vehicle is performing a lane keeping maneuver;

the target line is at an offset, including zero offset, to a lane centerline of the lane the vehicle is changing to when the vehicle is performing a lane change maneuver;

the target line is at an offset, including zero offset, to a lane centerline of the lane the vehicle is turning to when the vehicle is performing a left turn maneuver or a right turn maneuver; and

computing the location of the target line based on the lane centerline and the offset.

10. A lateral control system installed on a vehicle including steered wheels for controlling the steering of the vehicle, comprising:

a road detection means that provides information of the road in front of the vehicle;

a speed sensor for providing a vehicle speed signal;

a steering angle sensor for providing a steering angle signal;

a processor, connected to the road detection means to receive the information of the lane and connected to the speed sensor and the steering angle sensor to receive the vehicle speed signal and the steering angle signal, for computing a steering angle command by determining a look-ahead distance, computing a location of a target point at the look-ahead distance ahead the vehicle, predicting a forward location of the vehicle, calculating an error as a distance between the location of the target point and the forward location, computing a normalized error by dividing the error with the look-ahead distance, and integrating the normalized error; and

at least one steering actuator for turning the steered wheels according to the steering angle command so as to steer the vehicle to perform the maneuver.

11. The lateral control system in claim 10, wherein the road detection means comprises an image sensor for taking an image of the view ahead of the vehicle and an image processing unit for calculating a road shape as the road information from the image taken by the image sensor.

12. The lateral control system in claim 10, wherein the road detection means comprises a satellite navigation system for determining a location of the vehicle, a digital map, and a processing unit for mapping the location of the vehicle into the digital map and providing the road information ahead the location of the vehicle.

13. The lateral control system in claim 10, wherein the road detection means comprises a laser scanner for sending laser pulses and capturing lights reflected from objects in front of the vehicle and a processing unit for determining a road shape as the road information from the reflected lights.

14. The lateral control system in claim 10, wherein the processor determines the look-ahead distance based on at least one of the following:

vehicle speed, vehicle yaw rate, vehicle lateral acceleration, vehicle steering angle, a curvature of the lane, a distance to a lane boundary, a distance to an obstacle, the normalized error, the distance between the target point and the forward location, and a maneuver the vehicle is performing.

15. The lateral control system in claim 10, wherein the processor determines the location of the target point by

estimating a lane centerline based on the road information from the road detection means,

calculating the location of the target point based on the lane centerline and the look-ahead distance, wherein the target point is located at an offset, including zero offset, to the lane centerline and at the look-ahead distance ahead of the vehicle.

16. The lateral control system in claim 10, wherein the processor predicts the forward location of the vehicle by first estimating a vehicle rotating speed based on the steering angle signal and then computing the forward location based on the vehicle speed signal, the vehicle rotating speed, and the look-ahead distance.

17. The lateral control system in claim 10 further comprising a rotating speed sensor for providing a rotating speed signal of the vehicle, wherein the processor predicts the forward location of the vehicle based on the speed signal from the speed sensor and the rotating speed signal from the rotating speed sensor.

18. The lateral control system in claim 10 further connected to a maneuver decision unit installed on the vehicle, wherein the processor

receives a maneuver command from the maneuver decision unit, wherein the maneuver command comprises at least one of the following commands:

lane keeping, lane changing, left turn, right turn, and avoiding an obstacle;

selects a target line based on the maneuver command, wherein the target point is located on the target line; and

computes the location of the target point based on the target line and the look-ahead distance.