Vehicle hitch assist system

1. A hitch assist system for a vehicle, comprising:

an imager for capturing one or more images of a hitch assembly and a trailer coupler, the imager operably coupled with a tailgate of the vehicle that is operably coupled to a body of the vehicle, wherein the hitch assembly includes a ball mount and a hitch ball; and

a controller configured to generate an image that includes the hitch assembly and a portion of the body of the vehicle, identify the hitch assembly within the image, and estimate a ball mount length based on a predefined reference length, wherein the predefined reference length is a length of the portion of the body of the vehicle included in the image generated by the controller.

2. The hitch assist system of claim 1 , wherein the imager is moved from a first position to a second position when the tailgate is moved from the first position to the second position, the second position rearwardly and downwardly of the first position.

3. The hitch assist system of claim 1 , wherein the imager is located on a rear of a vehicle and is disposed to capture one or more images of a rear-vehicle scene.

4. The hitch assist system of claim 1 , wherein the controller is further configured to determine a hitch ball height.

5. The hitch assist system of claim 1 , wherein the controller is further configured to estimate a height of the trailer coupler.

6. The hitch assist system of claim 1 , wherein the trailer coupler comprises a coupler ball socket.

7. The hitch assist system of claim 1 , wherein the controller further estimates a hitch ball height based on the ball mount length and projective geometry of the imager.

8. The hitch assist system of claim 7 , wherein the controller further determines a hitch ball height related to a ground surface based on the estimated ball mount length, a height of the imager, a focal length of the imager, a pitch of the imager, and a vertical distance between the imager and the hitch assembly.

9. The hitch assist system of claim 1 , further comprising:

a display configured to display the one or more images of the imager and overlay a central locus line disposed through the hitch assembly, the central locus line defining a direction of a vehicle and hitch assembly that is updated in response to a change in a steering wheel angle of the vehicle.

10. A hitch assist method comprising the steps of:

rotating a tailgate operably supporting an imager from a first position to a second position;

capturing one or more images of a hitch assembly and a portion of a body of the vehicle with the imager;

estimating a ball mount length of the hitch assembly based on a comparison to a predefined reference length, wherein the predefined reference length is stored in memory and corresponds to a length of the portion of the body of the vehicle captured in the one or more images;

rotating the tailgate from the second position to the first; and

estimating a hitch ball height based on the ball mount length and projective geometry of the imager.

11. The hitch assist method of claim 10 , further comprising:

estimating a height of a trailer coupler.

12. The hitch assist method of claim 11 , further comprising:

comparing the hitch ball height to the trailer coupler height.

13. The hitch assist method of claim 12 , further comprising:

providing an alert if the hitch ball height is greater than the trailer coupler height.

14. The hitch assist method of claim 10 , wherein the hitch ball height comprises a height of the hitch ball relative to a ground surface.

15. The hitch assist method of claim 11 , wherein the height of the trailer coupler comprises a height of the hitch coupler relative to a ground surface, and wherein the coupler comprises a coupler ball socket.

16. A hitch assist system for a vehicle comprising:

an imager for capturing one or more images of a hitch assembly and a trailer coupler;

a display generating a rear contextual view based on the one or more images; and

a controller for:

identifying the hitch assembly;

identifying a trailer coupler;

displaying an overlaid line on the display that extends through the hitch assembly;

displaying a zoom window of the trailer coupler and the overlaid line;

estimating a ball mount length based on a comparison of the hitch assembly identified in the in the one or more images and a reference length stored in memory that corresponds to at least a portion of a component of the vehicle identified in the one or more images; and

determining a hitch ball height related to a ground surface based on the estimated ball mount length, a height of the imager, a focal length of the imager, and a vertical distance between the imager and the hitch assembly.

17. The hitch assist system of claim 16 , wherein the overlaid line illustrates a direction of a vehicle and the hitch assembly that is updated in response to a change in a steering wheel angle of the vehicle.

18. The hitch assist system of claim 16 , wherein the controller is further configured to estimate a trailer coupler height; compare a hitch ball height to the trailer coupler height; and provide an alert if the hitch ball height is greater than the trailer coupler height.