System and method of calibrating a trailer backup assist system
A system and a method are provided for calibrating a backup assist system for a trailer attached to a vehicle. The method includes driving the vehicle forward substantially straight above a threshold speed, sensing a yaw rate of the vehicle, and sensing a measured hitch angle of the trailer. A yaw sensor continuously senses the yaw rate of the vehicle and a hitch sensor continuously measures the hitch angle for determining an angle rate based on the measured hitch angle. Further, a controller determines an offset between the measured hitch angle and an actual hitch angle when the yaw rate and angle rate are substantially zero or otherwise the same.
1. A method of calibrating a backup assist system for a trailer attached to a vehicle, comprising:
driving the vehicle forward substantially straight above a threshold speed;
sensing a yaw rate of the vehicle with a yaw rate sensor;
sensing a measured hitch angle of the trailer with a hitch angle sensor;
determining an angle rate based on the measured hitch angle;
determining an approximate distance the vehicle needs to travel forward in a substantially straight orientation to place the actual hitch angle at substantially zero, wherein the approximate distance is determined based on a length of the trailer and the measured hitch angle; and
determining with a controller an offset between the measured hitch angle and an actual hitch angle when the yaw rate and angle rate are substantially zero and the actual hitch angle is substantially zero.
2. The method of claim 1 , further comprising:
steering the vehicle at a substantially constant steering angle to drive the vehicle in a substantially straight direction.
3. The method of claim 1 , wherein the yaw rate is sensed with the yaw rate sensor on the vehicle, and wherein the offset is determined when the yaw rate and angle rate are substantially zero over a threshold time.
4. The method of claim 1 , wherein the measured hitch angle is sensed with the hitch angle sensor that includes a video imaging camera of the vehicle that monitors a target on the trailer.
5. The method of claim 1 , wherein the offset is determined irrespective of the vehicle and the trailer dimensions.
6. The method of claim 1 , further comprising:
driving the vehicle forward in the substantially straight orientation a distance greater than the approximate distance to determine the offset.
7. A method of calibrating a backup assist system for a trailer attached to a vehicle, comprising:
driving the vehicle forward above a threshold speed;
steering the vehicle straight;
sensing a measured hitch angle of the trailer with a hitch angle sensor;
determining an angle rate based on the measured hitch angle;
determining an approximate distance the vehicle needs to travel forward in a substantially straight orientation to place the actual hitch angle at zero, wherein the approximate distance is determined based on a length of the trailer and the measured hitch angle;
steering the vehicle at a substantially constant steering angle to drive the vehicle substantially straight; and
determining with a controller an offset between the measured hitch angle and an actual hitch angle when the angle rate is substantially zero and the actual hitch angle is substantially zero.
8. The method of claim 7 , further comprising:
sensing angular changes of the vehicle with an inertial sensor on the vehicle, wherein the offset is determined when the angular changes are substantially zero.
9. The method of claim 7 , further comprising:
sensing a yaw rate of the vehicle with a yaw sensor on the vehicle, wherein the offset is determined when the yaw rate and the angle rate are substantially zero over a threshold time while the vehicle is driving forward above the threshold speed.
10. The method of claim 9 , wherein the measured hitch angle is sensed with a hitch angle sensor that includes a video imaging camera of the vehicle that monitors a target on the trailer.
11. The method of claim 7 , further comprising:
driving the vehicle forward in the substantially straight orientation a distance greater than the approximate distance to determine the offset.
12. A system for calibrating a backup assist system for a trailer attached to a vehicle, comprising:
a hitch angle sensor continuously measuring a hitch angle for determining an angle rate;
a yaw sensor continuously sensing a yaw rate of the vehicle; and
a controller determining an offset of the measured hitch angle when the vehicle is driving forward above a threshold speed and the yaw and angle rates are substantially zero, wherein the controller determines an approximate distance the vehicle must travel straight forward to place the actual hitch angle at zero based on a length of the trailer and the measured hitch angle, and wherein the offset is determined when the angle rate is substantially constant while the vehicle travels straight forward beyond the approximate distance.
13. The system of claim 12 , wherein the offset is determined between the measured hitch angle and the actual hitch angle when the actual hitch angle is substantially zero.
14. The method of claim 12 , wherein the controller determines the angle rate based on changes in the measured hitch angle over time, and wherein the hitch sensor includes a video imaging camera on the vehicle that continuously monitors a target on the trailer.
15. The system of claim 12 , wherein the yaw rate of the vehicle is substantially zero when the vehicle is steered straight, and wherein the offset is determined when the angle rate is substantially zero over a threshold time while the vehicle is driving straight forward above the threshold speed.