Method and apparatus of controlling an automotive vehicle using brake-steer as a function of steering wheel torque

1. A method of controlling an automotive vehicle having a turning radius comprising:

determining a hand wheel torque; and

comparing the steering wheel torque to a predetermined torque and when the steering torque is greater than the predetermined torque, performing the step of applying brake-steer, and when the steering wheel torque is below the predetermined torque not applying brake-steer.

2. A method as recited in claim 1 further comprising determining a steering wheel angle, wherein applying brake-steer comprises applying brake-steer as a function of hand wheel torque and steering wheel angle.

3. A method as recited in claim 1 further comprising determining a steering wheel angle direction, wherein applying brake-steer comprises applying brake-steer as a function of hand wheel torque, steering wheel direction and steering wheel angle.

4. A method as recited in claim 3 wherein the steering wheel direction comprises a torque increasing direction and a torque decreasing direction, wherein applying brake-steer comprises applying brake-steer using a first boost curve in the torque increasing direction and applying brake-steer using a second boost curve in the torque decreasing direction wherein the first boost curve is different than the second boost curve.

5. A method as recited in claim 4 wherein the first boost curve comprises a non-linear-boost curve.

6. A method as recited in claim 4 wherein the first boost curve increases brake-steer at a first rate for a first period of time, increases brake-steer at a second rate for a second period of time, wherein the second rate is greater than the first rate and increases brake-steer at a third rate for a third period of time wherein the third rate is less than the second rate.

7. A method as recited in claim 4 wherein the second boost curve comprises a non-linear-boost curve.

8. A method as recited in claim 4 wherein the second boost curve decreases brake-steer at a first rate for a first period of time, decreases brake-steer at a second rate for a second period of time, wherein the second rate is less than the first rate.

9. A method as recited in claim 1 wherein the torque comprises an increasing torque and a decreasing torque and wherein applying brake-steer comprises applying brake-steer using a first boost curve during increasing torque and applying brake-steer using a second boost curve during decreasing torque wherein the first boost curve is different than the second boost curve.

10. A method as recited in claim 9 wherein the first boost curve comprises a non-linear-boost curve.

11. A method as recited in claim 9 wherein the first boost curve increases brake-steer at a first rate for a first period of time, increases brake-steer at a second rate for a second period of time, wherein the second rate is greater than the first rate, and increases brake-steer at third rate for a third period of time wherein the third rate is less than the second rate.

12. A method as recited in claim 9 wherein the second boost curve comprises a non-linear-boost curve.

13. A method as recited in claim 9 wherein the second boost curve decreases brake-steer at a first rate for a first period of time, decreases brake-steer at a second rate for a second period of time, wherein the second rate is less than the first rate.

14. A method as recited in claim 1 further comprising reducing the turning radius of the vehicle during applying brake-steer.

15. A method as recited in claim 1 wherein applying brake-steer comprises applying at least one brake at a first wheel to reduce a vehicle turning radius.

16. A method as recited in claim 1 wherein applying brake-steer comprises applying an increased drive torque to a second wheel.

17. A method as recited in claim 1 further comprising determining a speed wherein applying a brake-steer comprises applying brake-steer as a function of steering wheel torque and vehicle speed.

18. A control system for a vehicle comprising:

a steering torque sensor generating a steering torque signal; and

a controller applying brake-steer to a vehicle as a function of the steering torque signal, wherein said controller changes to a 4×2 mode from a 4×4 mode to apply brake-steer.

19. A control system as recited in claim 18 wherein said controller applies brake-steer as a function of a vehicle speed.

20. A control system as recited in claim 18 wherein said controller applies a brake to apply brake-steer.

21. A control system as recited in claim 18 wherein said controller applies a differential torque steer.