Steering control system for vehicle

• US 6,178,365 B1
• Filed: 09/11/1998
• Issued: 01/23/2001
• Est. Priority Date: 09/13/1997
• Status: Expired due to Term

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Ishida, Shinnosuke, Kawagoe, Hiroyuki, Teramoto, Tomoaki, Matsuno, Kaoru
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US09/151,761
• Time in Patent Office: 865 Days
• Field of Search: 701/41, 701/1, 701/23, 180/168, 180/167, 180/169, 180/421, 180/422, 180/280
• US Class Current: 701/41
• CPC Class Codes: B60T 2201/08 Lane monitoring; Lane Keeping Systems
• CPC Class Codes: B60T 2201/087 using active steering actuation
• CPC Class Codes: B62D 1/286 Systems for interrupting non-mechanical steering due to driver intervention
• 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

Abstract

A system for controlling steering of a vehicle, including a steering device such as a steering wheel with an electric motor which assists steering of driven wheels of the vehicle, first steering control unit for controlling the motor, a CCD camera for detecting a lane condition of a road on which the vehicle travels, a yaw rate sensor for detecting motion of the vehicle, steering assist torque calculating unit for calculating a steering assist torque necessary for holding the lane, a torque sensor for detecting an actual steering torque manually applied to the steering device by the driver, and second steering control unit for calculating a torque command to be output to the first steering control unit based on the steering assist torque calculated by the steering assist torque calculating unit and the detected steering torque to control the actuator such that the torque command decreases. In the system, a switching device is provided for switching between modes of control by the first steering control unit and the second steering control unit gradually with respect to time, thereby ensuring to switch the mode of control smoothly and preventing the occurrence of disadvantages including that the vehicle driver experiences annoyance upon sensing a change in steering assist.

Claims

1. A system for controlling steering of a vehicle, comprising:

steering means having an actuator which steers driven wheels of the vehicle;

first steering control means for controlling the actuator;

first detecting means for detecting a lane condition of a road on which the vehicle travels;

second detecting means for detecting motion of the vehicle;

steering assist torque calculating means for calculating a steering assist torque necessary for holding a positional relationship between the vehicle and the lane condition;

torque detecting means for detecting a steering torque manually applied to the steering means by the driver;

second steering control means for calculating a torque command to be output to the first steering control means based on the steering assist torque calculated by the steering assist torque calculating means and the detected steering torque to control the actuator such that the torque command decreases; and

switching means for switching between the mode of control by the first steering control means and the mode of control by the second steering control means gradually with respect to time.

2. A system according to claim 1, wherein the switching means switches from the mode of control by the second steering control means to the mode of control by the first steering control means, when the detected steering torque is greater than a reference value.

3. A system according to claim 2, wherein the switching means switches from the mode of control by the second steering control means to the mode of control by the first steering control means in a time which decreases with increasing detected steering torque.

4. A system according to claim 1, further including:

steering speed detecting means for detecting a steering speed manually applied to the steering means by the driver;

and wherein the switching means switches from the mode of control by the second steering control means to the mode of control by the first steering control means, when the detected steering speed is greater than a reference value.

5. A system according to claim 4, wherein the switching means switches from the mode of control by the second steering control means to the mode of control by the first steering control means in a time which decreases with increasing detected steering speed.

6. A system according to claim 1, wherein the steering torque calculating means calculates the steering assist torque in accordance with a constituent ratio determined with respect to time when the modes of control by the first steering control means and the second steering control means are switched.

7. A system according to claim 6, wherein the steering torque calculating means calculates the steering assist torque in accordance with the constituent ratio determined which increases with increasing time, when the mode of control by the first steering control means is switched to the mode of control by the second steering control means.

8. A system according to claim 1, further including:

driver'"'"'s intention determining means for determining whether a driver has an intention to initiate steering;

and wherein the switching means switches from the mode of control by the second steering control means to the mode of control by the first steering control means, when it is determined that the driver has the intention to initiate steering.

9. A method of controlling steering of a vehicle, including:

steering means having an actuator which steers driven wheels of the vehicle;

first steering control means for controlling the actuator;

first detecting means for detecting a lane condition of a road on which the vehicle travels;

second detecting means for detecting motion of the vehicle;

steering assist torque calculating means for calculating a steering assist torque necessary for holding a positional relationship between the vehicle and the lane condition;

torque detecting means for detecting a steering torque manually applied to the steering means by the driver, and

second steering control means for calculating a torque command to be output to the first steering control means based on the steering assist torque calculated by the steering assist torque calculating means and the detected steering torque to control the actuator such that the torque command decreases;

wherein the method comprises the step of;

switching between mode of control by the first steering control means and the mode of control by the second steering control means (SAS ECU 74) gradually with respect to time.

10. A method according to claim 9, wherein switching from the mode of control by the second steering control means to the mode of control by the first steering control means, when the detected steering torque is greater than a reference value.

11. A method according to claim 10, wherein switching from the mode of control by the second steering control means to the mode of control by the first steering control means in a time which decreases with increasing detected steering torque.

12. A method according to claim 9, further including:

steering speed detecting means for detecting a steering speed manually applied to the steering means by the driver;

and wherein switching from the mode of control by the second steering control means to the mode of control by the first steering control means, when the detected steering speed is greater than a reference value.

13. A method according to claim 12, wherein switching from the mode of control by the second steering control means to the mode of control by the first steering control means in a time which decreases with increasing detected steering speed.

14. A method according to claim 9, wherein calculating the steering assist torque in accordance with a constituent ratio determined with respect to time when the modes of control by the first steering control means and the second steering control means are switched.

15. A method according to claim 14, wherein calculating the steering assist torque in accordance with the constituent ratio determined which increases with increasing time, when the mode of control by the first steering control means is switched to the mode of control by the second steering control means.

16. A method according to claim 9, further including:

driver'"'"'s intention determining means for determining whether a driver has an intention to initiate steering;

and wherein switching from the mode of control by the second steering control means to the mode of control by the first steering control means, when it is determined that the driver has the intention to initiate steering.

17. A computer program embodied on a computer-readable medium for controlling steering of a vehicle, including:

steering means having an actuator which steers driven wheels of the vehicle;

first steering control means for controlling the actuator;

first detecting means for detecting a lane condition of a road on which the vehicle travels;

second detecting means for detecting motion of the vehicle;

steering assist torque calculating means for calculating a steering assist torque necessary for holding a positional relationship between the vehicle and the lane condition;

torque detecting means for detecting a steering torque manually applied to the steering means by the driver, and

second steering control means for calculating a torque command to be output to the first steering control means based on the steering assist torque calculated by the steering assist torque calculating means and the detected steering torque to control the actuator such that the torque command decreases;

wherein the computer program comprises the step of;

switching between the mode of control by the first steering control means and the mode of control by the second steering control means (SAS ECU 74) gradually with respect to time.