System and method for calculating a horizontal camera to target distance
A system and method for calculating a horizontal camera to target distance is provided. A camera on board a vehicle is configured to image a target on a trailer that is aligned with the vehicle. A controller is in communication with the camera and is supplied a user-obtained measurement. The controller is configured to calculate a first horizontal distance and a second horizontal distance, and to sum the first and second horizontal distances to calculate a horizontal camera to target distance.
1. A trailer backup assist system comprising:
a camera configured to image a target on a trailer that is aligned with a vehicle; and a controller configured to:
estimate a target to ground measurement based on a draw bar drop measurement obtained by a user;
calculate a first and a second horizontal distance; and
sum the first and the second horizontal distance to calculate a horizontal camera to target distance.
2. The trailer backup assist system of claim 1 , wherein the camera has a vertical field of view defined by a lower field extent and an upper field extent, and wherein the first horizontal distance extends horizontally from the camera to an intersection point between the lower field extent and a centerline longitudinal axis of the target.
3. The trailer backup assist system of claim 2 , wherein the controller calculates the first horizontal distance using a camera to ground distance and an angle between a vertical axis extending through the camera and the lower field extent.
4. The trailer backup assist system of claim 3 , wherein the second horizontal distance extends horizontally from the intersection point to a target midpoint.
5. The trailer backup assist system of claim 4 , wherein the controller calculates the second horizontal distance using a camera to intersection point distance, a camera to target midpoint distance, and an angle between the camera to target midpoint distance and the camera to intersection point distance.
6. A trailer backup assist system comprising:
a camera on board a vehicle and having a vertical field of view defined by a lower field extent and an upper field extent for imaging a target located on a trailer;
an input device for entering a user-obtained measurement; and
a controller for receiving image data from the camera and the user-obtained measurement to calculate a first horizontal distance and a second horizontal distance;
wherein the first horizontal distance extends horizontally from the camera to an intersection point between the lower field extent and a centerline longitudinal axis of the target; and
wherein the second horizontal distance extends horizontally from the intersection point to a target midpoint.
7. The trailer backup assist system of claim 6 , wherein the user-obtained measurement comprises one of a target to ground distance and a draw bar drop measurement.
8. The trailer backup assist system of claim 6 , wherein the controller calculates the horizontal camera to target distance by summing the first horizontal distance and the second horizontal distance.
9. The trailer backup assist system of claim 8 , wherein the controller calculates the first horizontal distance using a first equation:
d 1 =d v tan θ
wherein d 1 is the first horizontal distance, d v is a vertical camera to target distance and θ is an angle between a vertical extent of a rear member of the vehicle and the lower field extent.
10. The trailer backup assist system of claim 8 , wherein the controller calculates the second horizontal distance using a second equation:
d 2 =√{square root over ( d a 2 +d b 2 −2 d a d b cos γ)}
wherein d 2 is the second horizontal distance, d a is a distance from the camera to the intersection point, d b is a camera to target midpoint distance, and γ is an angle between the camera to target midpoint distance d b and the camera to intersection point distance d a .
11. The trailer backup assist system of claim 10 , wherein angle γ is calculated using a third equation:
γ
δ
=
p
c
v
r
wherein δ corresponds a vertical field of view angle, p c corresponds to a pixel count of a camera image taken from the lower field extent to the target midpoint, and v r corresponds to a vertical resolution of the camera image.
12. The trailer backup assist system of claim 10 , wherein the camera to target midpoint distance d b is calculated using a fourth equation:
d
b
=
d
v
sin
∝
wherein d v is a vertical camera to target distance and α corresponds to an angle between the camera to target midpoint distance d b and the centerline longitudinal axis of the target.
13. A method for calculating a horizontal camera to target distance, comprising the steps of:
providing a camera on board a vehicle and imaging a target located on a trailer aligned with the vehicle;
supplying a controller with image data from the camera and a user-obtained measurement; and
using the controller to calculate a first horizontal distance and a second horizontal distance;
wherein the first horizontal distance extends horizontally from the camera to an intersection point between the lower field extent and a centerline longitudinal axis of the target; and
wherein the second horizontal distance extends horizontally from the intersection point to a target midpoint.
14. The method of claim 13 , wherein the user-obtained measurement comprises one of a target to ground distance and a draw bar drop measurement.
15. The method of claim 14 , wherein the user-obtained measurement is inputted to the controller via a user-input device.
16. The method of claim 13 , wherein the controller calculates the horizontal camera to target distance by summing the first horizontal distance and the second horizontal distance.
17. The method of claim 16 , wherein the controller calculates the first horizontal distance using a first equation:
d 1 =d v tan θ
wherein d 1 is the first horizontal distance, d v is a vertical camera to target distance and θ is an angle between a vertical extent of a rear member of the vehicle and the lower field extent.
18. The method of claim 16 , wherein the controller calculates the second horizontal distance using a second equation:
d 2 =√{square root over ( d a 2 +d b 2 −2 d a d b cos γ)}
wherein d 2 is the second horizontal distance, d a is a distance from the camera to the intersection point, d b is a camera to target midpoint distance, and γ is an angle between the camera to target midpoint distance d b and the camera to intersection point distance d a .
19. The method of claim 18 , wherein angle γ is calculated using a third equation:
γ
δ
=
p
c
v
r
wherein δ corresponds a vertical field of view angle, p c corresponds to a pixel count of a camera image taken from the lower field extent to the target midpoint, and v r corresponds to a vertical resolution of the camera image.
20. The method of claim 18 , wherein the camera to target midpoint distance d b is calculated using a fourth equation:
d
b
=
d
v
sin
∝
wherein d v is a vertical camera to target distance and α corresponds to an angle between the camera to target midpoint distance d b and the centerline longitudinal axis of the target.