Hitch angle detection using automotive radar

1. A trailer detection system for a vehicle, comprising:

a radar system outputting object point location data to a rear of the vehicle;

a vehicle steering system; and

a controller receiving the object point location data from the radar system and:

during non-trailering driving of the vehicle, using the object point location data to detect objects by processing the object point location data at a first predetermined detection threshold configured to detect objects including cars and people with a surface area open to the vehicle;

in a trailer angle detection routine during trailering driving of the vehicle:

monitoring a position of an edge of a trailer relative to the vehicle by continuously processing the object point location data from the radar system at a second predetermined detection threshold lower than the first detection threshold and configured to detect trailer edges on surfaces open away from the vehicle to derive additional detection points relative to a number of points derived using the first threshold and filtering out object point location data not correlated with the edge of the trailer based on object point location data persistence during driving of the vehicle;

correlating the determined position of the edge of the trailer relative to the vehicle to determine an angle of the trailer relative to the vehicle about a coupling point, at which the trailer is coupled with the vehicle, over successive radar scans on a continuous basis; and

controlling the steering system of the vehicle using the angle of the trailer in a kinematic model of the vehicle and trailer combination to steer the vehicle along a backing path.

2. The system of claim 1 , wherein the backing path corresponds with a user-commanded curvature of the vehicle and trailer.

3. The system of claim 1 , wherein the radar system includes a first radar unit mounted on a rear of the vehicle.

4. The system of claim 3 , wherein:

the first radar unit is mounted on a right side of the rear of the vehicle; and

the radar system further includes a second radar unit mounted on a left side of the rear of the vehicle.

5. The system of claim 4 , wherein the controller:

detects points along the edge of the trailer using the first and second radar units;

establishes locations of the points within first and second coordinate systems associated respectively with the first and second radar units; and

uses the locations of the points within the first and second coordinate systems to establish locations for the points in a third coordinate system aligned with a hitch ball of the vehicle.

6. The system of claim 5 , wherein at least the first and second coordinate systems are population grids.

7. The system of claim 1 , wherein the controller correlates the determined position of the edge of the trailer relative to the vehicle to determine the angle of the trailer relative to the vehicle about the coupling point by:

populating a first matrix of static object location points corresponding with the edge of the trailer relative to the vehicle when the angle is known to be zero;

continuing to receive the object point location data and determining the position of the edge of the trailer relative to the vehicle when the angle is not known to be zero and populating a second matrix of dynamic object location points corresponding with the edge of the trailer relative to the vehicle; and

using the first and second matrices to calculate a rotation matrix for the static rotation points to the dynamic rotation points.

8. The system of claim 7 , wherein the rotation matrix is processed to derive the angle.

9. The system of claim 1 , wherein the controller receives the object point location data and determines the position of the edge of the trailer relative to the vehicle and correlates the determined position of the edge of the trailer relative to the vehicle to determine the angle of the trailer relative to the vehicle during forward driving at a vehicle speed of less than 10 miles per hour.

10. A method for determining a trailer position relative to a vehicle, comprising:

during non-trailering driving of the vehicle, receiving object point location data from a radar system useable at a first detection threshold to detect objects including cars and people; and

in a trailer angle detection routine during trailering driving of the vehicle:

determining a position of an edge of the trailer relative to the vehicle by processing the object point location data from the radar system at a second detection threshold lower than the first detection threshold and configured to detect objects including portions of a trailer to derive additional detection points relative to a number of points derived using the first threshold and filtering out object point location data not correlated with the edge of the trailer based on object point location data persistence during driving of the vehicle;

correlating the determined position of the edge of the trailer relative to the vehicle to determine an angle of the trailer relative to the vehicle about a coupling point at which the trailer is coupled with the vehicle; and

controlling a steering system of the vehicle using the angle of the trailer in a kinematic model of the vehicle and trailer combination to maintain the vehicle along a backing path.

11. The method of claim 10 , wherein:

receiving object point location data, determining the position of the edge of the trailer, and determining the angle of the trailer relative to the vehicle is initially carried out during an initial edge detection process during straight driving at a vehicle speed of less than 10 miles per hour; and

the initial edge detection process is completed prior to controlling a steering system of the vehicle to maintain the vehicle along a backing path.

12. The method of claim 11 , wherein controlling the steering system of the vehicle to maintain the vehicle along the backing path also includes:

receiving object point location data, determining the position of the edge of the trailer, and determining the angle of the trailer relative to the vehicle.

13. The method of claim 10 , wherein:

receiving the object point location data from the radar system and determining the position of the edge of the trailer relative to the vehicle includes detecting points along the edge of the trailer using first and second radars in the radar system and determining locations of the points within first and second coordinate systems associated respectively with the first and second radars; and

correlating the determined position of the edge of the trailer relative to the vehicle to determine the angle of the trailer relative to the vehicle about the coupling point includes using the locations of the points within the first and second coordinate systems to establish locations for the points in a third coordinate system aligned with a hitch ball of the vehicle and included in the coupling point.

14. The method of claim 10 , wherein correlating the determined position of the edge of the trailer relative to the vehicle to determine the angle of the trailer relative to the vehicle about the coupling point includes:

populating a first matrix of static object location points corresponding with the edge of the trailer relative to the vehicle when the angle is known to be zero;

continuing to receive the object point location data and determining the position of the edge of the trailer relative to the vehicle when the angle is not known to be zero and populating a second matrix of dynamic object location points corresponding with the edge of the trailer relative to the vehicle;

using the first and second matrices to calculate a rotation matrix for the static rotation points to the dynamic rotation points; and

processing the rotation matrix is to derive the angle.

15. A vehicle, comprising:

a radar system outputting object point location data to a rear of the vehicle; and

a controller:

receiving the object point location data and determining the position of an edge of the trailer relative to the vehicle by:

processing the object point location data from the radar system at a first detection threshold configured to detect objects including cars and people with a surface area open to the vehicle and determining, based on the processing, a number of detected points to be insufficient to detect an edge of the trailer; and

processing the object point location data from the radar system at a second detection threshold lower than the first threshold and configured to detect trailer edges on surfaces open away from the vehicle, and filtering out object point location data not correlated with the edge of the trailer based on object point location data persistence during driving of the vehicle; and

correlating the determined position of the edge of the trailer relative to the vehicle to determine an angle of the trailer relative to the vehicle about a coupling point, at which the trailer is coupled with the vehicle, over successive radar scans on a continuous basis.

16. The vehicle of claim 15 , further including a steering system, wherein:

the controller further controls the steering system of the vehicle using the angle of the trailer in a kinematic model of the vehicle and trailer combination to maintain the vehicle along a backing path.

17. The vehicle of claim 15 , wherein:

the radar system includes a first radar unit mounted on a right side of the rear of the vehicle and a second radar unit mounted on a left side of the rear of the vehicle; and

the controller:

detects points along the edge of the trailer using the first and second radars;

establishes locations of the points within first and second coordinate systems associated respectively with the first and second radars; and

uses the locations of the points within the first and second coordinate systems to establish locations for the points in a third coordinate system aligned with a hitch ball of the vehicle.

18. The vehicle of claim 15 , wherein the controller correlates the determined position of the edge of the trailer relative to the vehicle to determine the angle of the trailer relative to the vehicle about the coupling point by:

populating a first matrix of static object location points corresponding with the edge of the trailer relative to the vehicle when the angle is known to be zero;

continuing to receive the object point location data and determining the position of the edge of the trailer relative to the vehicle when the angle is not known to be zero and populating a second matrix of dynamic object location points corresponding with the edge of the trailer relative to the vehicle;

using the first and second matrices to calculate a rotation matrix for the static rotation points to the dynamic rotation points; and

processing the rotation matrix to derive the angle.