Four-wheel steered vehicle and torque distribution control methods for same

• US 9,008,915 B2
• Filed: 02/13/2013
• Issued: 04/14/2015
• Est. Priority Date: 02/13/2013
• Status: Expired due to Fees

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Kang, Xiaodi, Cymbal, Christopher J., Thompson, David A.
• Primary Examiner(s): Nguyen, John Q
• Assistant Examiner(s): Sood, Anshul
• Application Number:
  US13/765,768
• Publication Number:
  US 20140229071A1
• Time in Patent Office: 790 Days
• Field of Search: 701/42, 701/69, 701/89, 180/245
• US Class Current: 701/42
• CPC Class Codes: B60W 10/12 including control of differentials
• CPC Class Codes: B60W 10/14 Central differentials for dividing torque between front and rear axles
• CPC Class Codes: B60W 10/20 including control of steering systems
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 2556/00 Input parameters relating to data
• CPC Class Codes: B60W 30/02 Control of vehicle driving stability
• CPC Class Codes: B60W 30/045 Improving turning performance
• CPC Class Codes: B62D 6/002 computing target steering angles for front or rear wheels B62D7/159 takes precedence
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A method for operating steerable rear wheels of a vehicle includes detecting a rear wheel steering angle of at least one of the steerable rear wheels, and detecting a first vehicular condition. The method further includes determining a weighted rear steering angle value based at least in part upon the rear wheel steering angle and the first vehicular condition, and controlling the steerable rear wheels in response to the weighted rear steering angle value.

Claims

1. A method for controlling torque distribution to steerable rear wheels of a vehicle, the method comprising:

generating rear wheel steering data, by a first controller, to facilitate steering of at least one of the steerable rear wheels;

generating a theoretical standard torque bias ratio value, by a second controller, for controlling the distribution of torque to the steerable rear wheels without rear steering;

transmitting the rear wheel steering data from the first controller to the second controller along a bidirectional communication bus;

determining, by the second controller, a vehicular speed;

determining, by the second controller, a lateral acceleration;

calculating, by the second controller, a scaling factor based at least in part upon one or more of the vehicular speed and the lateral acceleration;

calculating, by the second controller, a enhanced torque bias ratio value based at least in part upon the theoretical standard torque bias ratio value and the scaling factor;

transmitting the enhanced torque bias ratio value from the second controller to the first controller along the bidirectional communication bus;

allocating a first control authority to the first controller in response to the enhanced torque bias ratio value;

allocating a second control authority to the second controller in response to the enhanced torque bias ratio value;

controlling steering of the steerable rear wheels, by the first controller, in response to the first control authority; and

controlling distribution of torque among the steerable rear wheels, by the second controller, in response to the second control authority;

wherein the first control authority and the second control authority are inversely proportional to one another.

2. The method of claim 1 wherein calculating the scaling factor comprises calculating a four-wheel steering based scaling factor by:

determining, by the second controller, a turning direction of the vehicle;

determining, by the second controller, inner and outer wheels based at least in part upon the turning direction;

determining, by the second controller, an inner wheel scaling factor based at least in part upon the vehicular speed;

determining, by the second controller, an outer wheel scaling factor based at least in part upon the vehicular speed;

detecting an inner steering angle value of the inner wheel;

applying the inner wheel scaling factor to the inner steering angle value;

detecting an outer steering angle of the outer wheel; and

applying the outer wheel scaling factor to the outer steering angle value;

wherein the inner wheel scaling factor is less than the outer wheel scaling factor.

3. The method of claim 2 further comprising increasing the first control authority and decreasing the second control authority when at least one of the vehicular speed, the steering angle value of the inner wheel, and the steering angle value of the outer wheel increases.

4. The method of claim 2 wherein:

the inner wheel scaling factor;

remains at a first value for a first range of vehicular speeds;

increases from the first value to a second value for a second range of vehicular speeds; and

remains at a third value for a third range of vehicular speeds;

the outer wheel scaling factor;

remains at a fourth value for the first range of vehicular speeds;

increases from the first value to the second value for a fifth range of vehicular speeds; and

remains at the third value for a sixth range of vehicular speeds;

the fourth value is greater than the first value;

the fifth value is greater than the second value; and

the sixth value is greater than the third value.

5. The method of claim 1 wherein calculating the scaling factor comprises calculating a four-wheel steering based scaling factor based at least in part upon the vehicular speed and the turning direction.

6. The method of claim 1 wherein calculating the scaling factor comprises calculating a lateral acceleration-based scaling factor based at least in part upon the lateral acceleration.

7. The method of claim 6 further comprising decreasing the first control authority and increasing the second control authority when the lateral acceleration increases.

8. A method for controlling torque distribution to steerable rear wheels of a vehicle, the method comprising:

detecting a rear wheel steering angle of at least one of the steerable rear wheels;

calculating a four wheel steering based scaling factor based at least in part upon the rear wheel steering angle;

generating a theoretical standard torque bias ratio value, by a second controller, for controlling the distribution of torque to the steerable rear wheels without rear steering;

calculating a enhanced torque bias ratio value based at least in part upon the standard torque bias ratio value and the four wheel steering based scaling factor;

determining a first control authority for a first controller based upon the enhanced torque bias ratio value, the first controller being configured to facilitate steering of the steerable rear wheels;

determining a second control authority for a second controller based at least in part upon the enhanced torque bias ratio value, the second controller being configured to facilitate distribution of torque among the steerable rear wheels;

varying each of the first control authority and the second control authority in response to a change in the enhanced torque bias ratio value; and

controlling the steering and the distribution of torque of the steerable rear wheels in response to the first control authority and the second control authority.

9. The method of claim 8 further comprising:

determining by the second controller, a vehicular speed; and

calculating the four wheel steering based scaling factor based at least in part upon the vehicular speed.

10. The method of claim 9 wherein calculating the four-wheel steering based scaling factor further comprises:

determining a turning direction for the vehicle;

identifying inner and outer wheels based at least in part upon the turning direction;

determining an inner wheel scaling factor based at least in part upon the vehicular speed;

determining an outer wheel scaling factor based at least in part upon the vehicular speed;

detecting an inner steering angle value of the inner wheel;

applying the inner wheel scaling factor to the inner steering angle value;

detecting an outer steering angle of the outer wheel; and

applying the outer wheel scaling factor to the outer steering angle value;

wherein the inner wheel scaling factor is less than the outer wheel scaling factor.

11. The method of claim 10 further comprising increasing the first control authority and decreasing the second control authority when at least one of the vehicular speed, the steering angle value of the inner wheel, and the steering angle value of the outer wheel increases.

12. The method of claim 11 further comprising:

determining by the second controller, a lateral acceleration; and

decreasing the first control authority and increasing the second control authority when the lateral acceleration increases.

13. The method of claim 9 wherein:

the inner wheel scaling factor;

remains at a first value for a first range of vehicular speeds;

increases from the first value to a second value for a second range of vehicular speeds; and

remains at a third value for a third range of inner steering angle values;

the outer wheel scaling factor;

remains at a fourth value for the first range of vehicular speeds;

increases from the first value to the second value for a fifth range of vehicular speeds; and

remains at the third value for a sixth range of inner steering angle values;

the fourth value is greater than the first value;

the fifth value is greater than the second value; and

the sixth value is greater than the third value.

14. A method for controlling torque distribution to steerable rear wheels of a vehicle, the method comprising:

determining a lateral acceleration;

calculating a lateral acceleration based scaling factor based at least in part upon the lateral acceleration;

generating a theoretical standard torque bias ratio value for controlling the distribution of torque to the steerable rear wheels without rear steering;

calculating a enhanced torque bias ratio value based at least in part upon the theoretical standard torque bias ratio value and the lateral acceleration based scaling factor;

determining a first control authority for a first controller based upon the enhanced torque bias ratio value, the first controller being configured to facilitate steering of the steerable rear wheels;

determining a second control authority for a second controller based at least in part upon the enhanced torque bias ratio value, the second controller being configured to facilitate distribution of torque among the steerable rear wheels;

varying each of the first control authority and the second control authority in response to a change in the enhanced torque bias ratio value; and

controlling the steering and the distribution of torque of the steerable rear wheels in response to the first control authority and the second control authority.