Holistic control for stabilizing vehicle-trailer swaying

1. A trailer sway intervention system, comprising:

a trailer including a plurality of wheels, each wheel having a brake; and

a vehicle towing the trailer, the vehicle including a plurality of sensors configured to sense operating characteristics of the vehicle, a controller configured to receive the sensed operating characteristics from the plurality of sensors, determine an error, the error being a difference between an expected yaw rate and a sensed yaw rate, asymmetrically apply braking forces to one or more trailer wheels based on the difference between the expected yaw rate and the sensed yaw rate, and symmetrically apply braking forces to the trailer wheels when the absolute value of the difference between the expected yaw rate and the sensed yaw rate is declining;

wherein the asymmetric braking forces have an inverse relationship to the symmetric braking forces.

2. The trailer sway intervention system of claim 1 , wherein a magnitude of the asymmetric braking forces are determined by a first closed loop controller using the error.

3. The trailer sway intervention system of claim 2 , wherein the first closed loop controller is a PID controller.

4. The trailer sway intervention system of claim 2 , wherein a magnitude of the symmetric braking forces are determined by a second closed loop controller using a difference between the error and a peak magnitude of the difference between the expected yaw rate and the sensed yaw rate.

5. The trailer sway intervention system of claim 4 , wherein the second closed loop controller is a PID controller.

6. The trailer sway intervention system of claim 1 , wherein the trailer sway intervention system is part of a vehicle electronic stability control system.

7. The trailer sway intervention system of claim 6 , wherein an operation of the vehicle electronic stability control system on the vehicle is modified when the trailer is present.

8. A method of reducing trailer oscillation, comprising:

calculating a target yaw rate for a vehicle;

sensing an actual yaw rate for the vehicle;

determining an error value based on a difference between the target yaw rate and sensed yaw rate;

asymmetrically applying braking forces to one or more wheels of a trailer based on the error; and

symmetrically applying braking forces to a plurality of the one or more wheels of the trailer when the absolute value of a magnitude of the error is declining;

wherein the braking forces applied asymmetrically have an inverse relationship to the braking forces applied symmetrically.

9. The method of claim 8 , further comprising performing proportional integral derivative closed loop control on the error to determine the asymmetric braking force.

10. The method of claim 8 , further comprising determining a peak magnitude of the error for each cycle of the error.

11. The method of claim 10 , further comprising determining a difference between the peak magnitude of the error and the determined error.

12. The method of claim 11 , further comprising performing proportional integral derivative closed loop control on the difference between the peak magnitude of the error and the determined error to determine the symmetric braking force.

13. The method of claim 8 , wherein one or more vehicle electronic stability control functions is altered when the vehicle is towing a trailer.