COUPLING ANGLE DETECTION FOR TRAILER REVERSING ASSISTANCE SYSTEM

Abstract

A system for detecting a coupling angle between a vehicle (14) and a trailer (12), comprising: an imaging device (34) configured to capture images of the trailer (12); a controller (38) designed to: Processing the images captured by the imaging device (34); Deriving a pattern image (158) with a trailer contour (152) by: Deriving an averaged image from all images captured by the imaging device (34) during a period in which the vehicle (14) and the trailer (12) are moving in a straight direction; Calculating an edge value for each pixel of the averaged image; Comparing the edge value of each pixel with a threshold to identify trailer pixels and ground pixels; and Determining the trailer contour (152) based on the identified trailer pixels; and Matching the sample image (158) with a search image (171); wherein the coupling angle is determined based on a positional relationship between the pattern image (158) and the search image (171); wherein the controller (38) compares the pattern image (158) with the search image (171) by rotating the pattern image (158) relative to the search image (171) about a pivot point; and wherein the coupling angle correlates with an angle by which the pattern image (158) is rotated relative to the search image (171) to produce a match therebetween.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to trailer reversing assistance systems in general and, more particularly, to trailer reversing assistance systems that employ hitch angle detection by image processing. BACKGROUND OF THE INVENTION

[0002] Reversing a vehicle while towing a trailer can be challenging for many drivers, especially those who rarely tow a trailer or who tow multiple trailers. Some systems used to assist a driver in reversing a trailer rely on hitch angle measurements to determine the trailer's position relative to the vehicle. Thus, the accuracy and reliability of the hitch angle measurements can be critical to the operation of the trailer reversing assistance system. SUMMARY OF THE INVENTION

[0003] According to one aspect of the present invention, a system for detecting a hitch angle between a vehicle and a trailer is provided. An imaging device is configured to capture images of the trailer, and a controller is configured to process the images captured by the imaging device. The controller derives a template image including a trailer contour and compares the template image with a search image. The hitch angle is determined based on a positional relationship between the template image and the search image.

[0004] According to another aspect of the present invention, a system for detecting a hitch angle between a vehicle and a trailer is provided. An imaging device is configured to capture images of the trailer, and a controller is configured to process the images captured by the imaging device. The controller derives a template image having a trailer contour and rotates the template image relative to a search image about an imaged hitch point common to the template image and the search image. The controller determines the hitch angle based on an angle by which the template image is rotated relative to the search image to create a match therebetween.

[0005] According to yet another aspect of the present invention, a method for detecting a hitch angle between a vehicle and a trailer is provided. The method includes the steps of capturing images of the trailer using an imaging device and providing a controller configured to process the images captured by the imaging device. The controller derives a template image including a trailer contour and compares the template image with a search image. The hitch angle is determined based on a positional relationship between the template image and the search image.

[0006] These and other features, advantages and objects of the present invention will be better understood and appreciated by those skilled in the art by reference to the following description, claims and appended drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the drawings: Fig. 1 is a top perspective view of a trailer mounted on a vehicle having one embodiment of a hitch angle sensor for operating a trailer backup assist system; Fig. 2 is a block diagram illustrating an embodiment of the trailer backup assist system including a steering input device, a turn control, and a trailer braking system; Fig. 3 is a flowchart for a method for detecting a hitch angle according to one embodiment. Fig. Figure 4 is a captured image showing a trailer in straight alignment with a vehicle and the presence of ground disturbances; Fig. 5 is an edge mapping of the recorded image Fig. 4 shown image; Fig. Figure 6 illustrates the blurring of ground disturbances in an averaged image; Fig. 7 is an edge mapping of the averaged Fig. 6 shown image; Fig. 8 illustrates a pendant outline of a sample image; Fig. 9 illustrates a pattern image being compared with a search image to determine a coupling angle; and Fig. 10 is a search image having a proximity zone for collapse detection and a number of candidate hitch point locations around which a pattern image can be rotated to determine an actual imaged hitch point and a hitch angle; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] For the purposes of the description herein, it is to be understood that the disclosed trailer backup assist system and related methods are capable of various alternative embodiments and orientations, unless expressly stated to the contrary. Further, it is to be understood that the specific devices and processes illustrated in the appended drawings and described in the following description are simply embodiments of the inventive concepts defined in the appended claims. Although various aspects of the trailer backup assist system and related methods are described with reference to a particular illustrated embodiment, the disclosed invention is not limited to such embodiments, and additional modifications, applications, and embodiments may be practiced without departing from the disclosed invention.Therefore, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered limiting unless expressly stated to the contrary in the claims.

[0009] As used herein, the term "and / or," when used in a list of two or more elements, means that each of the listed elements may be employed alone or in any possible combination of two or more of the listed elements. For example, if a composition is described as containing components A, B, and / or C, the composition may contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0010] With reference to the Fig. 1 and Fig. 2, reference numeral 10 generally designates a trailer backup assist system for controlling a backup path of a trailer 12 attached to a vehicle 14 by allowing a driver of the vehicle 14 to specify a desired curved path of the backup path of the trailer 12. The vehicle 14 is implemented as a pickup truck pivotally mounted to an embodiment of the trailer 12 having a box frame 16 with an enclosed cargo area 18, a single axle 20 operably coupled to wheels 22 and 24, and a tongue 26 extending longitudinally forward from the enclosed cargo area 18. The illustrated trailer 12 also includes a trailer hitch connector in the form of a coupling assembly 28 connected to a vehicle hitch connector in the form of a hitch ball 30 and a drawbar 31.The coupling assembly 28 engages the coupling ball 30 to create a coupling pivot point 32 that allows for articulation of a coupling angle between the vehicle 14 and the trailer 12. As defined herein, the coupling angle corresponds to the angle formed between the centered longitudinal axis of the vehicle 14 and that of the trailer 12 (see coupling angle γ; ). Fig. 17). It is understood that additional embodiments of the trailer 12 may alternatively be coupled to the vehicle 14 to provide a pivoting connection, such as by connecting with a fifth wheel connection. It is also contemplated that additional embodiments of the trailer 12 may include more than one axle and may have various shapes and sizes configured for different loads and items, such as a boat trailer or a flatbed trailer.

[0011] The trailer backup assist system 10 includes an imaging device 34 located at the rear of the vehicle 14 and configured to image a rear vehicle scene. The imaging device 34 may be centrally located in an upper portion of the tailgate 35 such that the imaging device 34 is raised relative to the tongue 26 of the trailer 12. The imaging device 34 has a field of view 36 positioned and oriented to capture one or more images, which may include, among other things, the tongue 26 of the trailer 12 and the hitch ball 30. Captured images are provided to a controller 38 of the trailer backup assist system 10 and are processed by the controller 38 to determine the hitch angle between the vehicle 14 and the trailer 12, as will be described in more detail herein.The controller 38 is configured with a microprocessor 40 and / or other analog and / or digital circuitry for processing one or more logic routines stored in a memory 42. The logic routines may include one or more hitch angle detection routines 44 and operational routines 46. Information from the imaging device 34 or other components of the trailer backup assist system 10 may be provided to the controller 38 via a communications network of the vehicle 14, which may include a controller area network (CAN), a local area network (LIN), or other conventional protocols used in the automotive industry.It will be appreciated that the controller 38 may be a standalone, dedicated controller, or a common controller integrated with the imaging device 34, or another component of the trailer backup assist system 10, in addition to any other conceivable onboard or off-board vehicle control systems.

[0012] With respect to the present embodiment, the controller 38 of the trailer backup assist system 10 may be configured to communicate with a variety of vehicle equipment. The trailer backup assist system 10 may include a vehicle sensor module 48 that monitors certain dynamics of the vehicle 14. The vehicle sensor module 48 may generate a plurality of signals communicated to the controller 38, which may include a vehicle speed signal generated by a speed sensor 50 and a vehicle yaw rate signal generated by a yaw rate sensor 52. A steering input device 54 may be provided to enable a driver to control or otherwise modify the desired curvature of the trailer 12's backup path.The steering input device 54 may be communicatively coupled to the controller 38 in a wired or wireless manner and provides the controller 38 with information defining the desired curvature of the return path of the trailer 12. In response, the controller 38 processes the information and generates corresponding steering commands, which are provided to a power steering system 56 of the vehicle 14. In one embodiment, the steering input device 54 includes a rotary knob 58 operable between a number of rotational positions, each providing an incremental change in the desired curvature of the return path of the trailer 12.

[0013] According to one embodiment, the controller 38 of the trailer backup assist system 10 may control the power steering system 56 of the vehicle 14 to operate the steerable wheels 60 of the vehicle 14 to move the vehicle 14 such that the trailer 12 responds in accordance with the desired curvature of the trailer's 12 reversing path. The power steering system 56 may be an electric power-assisted steering (EPAS) system that includes an electric steering motor 62 for turning the steerable wheels 60 to a steering angle based on a steering command generated by the controller 38, wherein the steering angle may be sensed by a steering angle sensor 64 of the power steering system 56 and provided to the controller 38. The steering command may be provided for autonomous steering of the vehicle 14 during a reversing maneuver and may alternatively be manually controlled via a rotational position (e.g.,a steering wheel angle) of a steering wheel 66 or a rotary knob 58. However, in some embodiments, the steering wheel 66 of the vehicle 14 is mechanically coupled to the steered wheels 60 of the vehicle 14 such that the steering wheel 66 moves in concert with the steered wheels 60 via an intrinsic torque, thereby preventing manual intervention via the steering wheel 66 during autonomous steering of the vehicle 14. In such cases, the power steering system 56 may include a torque sensor 68 that detects torque (e.g., gripping and / or slipping) at the steering wheel 66 that is not expected from autonomous control of the steering wheel 68 and thus indicates manual intervention by the driver.In some embodiments, the external torque applied to the steering wheel 66 may serve as a signal to the controller 38 that the driver has assumed manual control and for the trailer backup assist system 10 to terminate the autonomous steering functionality.

[0014] The controller 38 of the trailer backup assist system 10 may also communicate with a vehicle braking control system 70 of the vehicle 14 to receive vehicle speed information, such as individual wheel speeds of the vehicle 14. Additionally or alternatively, vehicle speed information may be provided to the controller 38 from, among other sources, a powertrain control system 72 and / or the speed sensor 50. It is contemplated that individual wheel speeds may be used to determine a vehicle yaw rate, which may be provided to the controller 38 alternatively or in addition to the vehicle yaw rate measured by the yaw rate sensor 52 of the vehicle sensor module 48. In some embodiments, the controller 38 may provide braking commands to the braking control system 70, thereby enabling the trailer backup assist system 10 to regulate the speed of the vehicle 14 during a backing maneuver of the trailer 12.It is understood that the controller 38 may additionally or alternatively control the speed of the vehicle 14 via interaction with the powertrain control system 72.

[0015] By interacting with the power steering system 56, the vehicle brake control system 70, and / or the powertrain control system 72 of the vehicle 14, the potential for unacceptable trailer backing conditions may be reduced. Examples of unacceptable trailer backing conditions include, but are not limited to, a vehicle-too-fast condition, a high hitch angle rate, dynamic hitch angle instability, a trailer collapse condition, sensor failure, and the like. Under such circumstances, the driver may not be aware of the failure until the unacceptable trailer backing condition is imminent or already in progress.Thus, it is disclosed herein that the controller 38 of the trailer backup assist system 10 may generate a warning signal corresponding to a notification of an incipient, impending, and / or anticipated unacceptable trailer backup condition and may generate a countermeasure to prevent such an unacceptable trailer backup condition prior to driver intervention.

[0016] According to one embodiment, the controller 38 may communicate with one or more devices, including a vehicle warning system 74, which may provide visual, audible, and tactile warnings. For example, vehicle brake lights 76 and vehicle hazard warning flashers may provide a visual warning, and a vehicle horn 78 and / or speakers 80 may provide an audible warning. Additionally, the controller 38 and / or the vehicle warning system 74 may communicate with a human-machine interface (HMI) 82 for the vehicle 14. The HMI 82 may include a touchscreen vehicle display 84, such as a center console-mounted navigation or entertainment display, capable of displaying images indicative of the warning. Such an embodiment may be desirable to notify the driver of the vehicle 14 that an unacceptable trailer backing condition is in progress.It is further contemplated that the controller 38 may communicate via wireless communication with one or more portable electronic devices, such as the portable electronic device 86 implemented as a smartphone. The portable electronic device 86 may include a display 88 for displaying one or more images and other information to a user. In response, the portable electronic device 86 may provide feedback information, such as visual, audible, and tactile alerts.

[0017] Referring to Fig. 3 illustrates a method for detecting a hitch angle. The method, also referred to herein as "the pattern matching method," may be executed by the controller 38 of the trailer backup assist system 10 and is shown as one embodiment of the hitch angle detection routine 44. The pattern matching method generally involves processing image information to distinguish a trailer contour from ground disturbances in images captured by the imaging device 34. The trailer contour then serves as a pattern and is matched to a search image to determine the hitch angle between the vehicle 14 and the trailer 12.

[0018] For illustrative purposes, Fig. 4 shows, by way of example, a captured image 90 illustrating the trailer 12 in a straight alignment with the vehicle 14 and the presence of ground disturbances. As defined herein, ground disturbances generally correspond to any ground structure capable of interfering with the image capture of the trailer 12. With regard to the captured image 90, candidate disturbances may include large stones (e.g., stone 92) and irregular ground surfaces (e.g., ground surface 94). As such, it may be difficult to accurately identify the trailer 12 when an image capture technique, namely edge detection, is applied to the captured image 90, as exemplified in Fig. 5. With these things in mind, the pattern matching method described here is capable of blurring ground disturbances to enable identification of one or more trailer contours. Once identified, the trailer contour(s) can be stored as a pattern image, which is matched to a search image to determine the coupling angle between the vehicle 14 and the trailer 12. In practice, this method has been found to be highly robust and benefits from relatively quick and simple calculations.

[0019] The pattern matching process may begin at step 100, where the driver or other occupant initializes the trailer backup assist system 10. This may be accomplished via user input using the display 84 of the vehicle 14 or by other conceivable means. At step 110, the driver is instructed to pull the trailer 12 in a straight direction so that the hitch angle between the vehicle 14 and the trailer 12 is substantially zero. While the vehicle 14 and the trailer 12 are locked in the straightening maneuver, at step 120, the controller 38 derives an averaged image of all images captured by the imaging device 34 during a period of time. It has been found that typically 1-3 seconds is sufficient. Note that the trailer 12 appears stationary within the images captured by the imaging device 34, whereas the ground disturbances vary from image to image.Thus, pixels associated with the trailer 12 will retain their contrast with respect to the averaged image, whereas pixels associated with the ground disturbances will be blurred. To illustrate this effect, . Fig. 6 shows an averaged image 125 as an example.

[0020] At step 130, the controller 38 derives an edge map of the averaged image by calculating the intensity gradient for each pixel of the averaged image 125. The intensity gradient, or edge value, of each pixel can range from 0 to 255. For illustrative purposes, Fig. 7 shows, by way of example, an edge map 135 in which the edge values ​​of pixels associated with ground disturbances have been significantly attenuated due to the blurring effect. At step 140, the controller 38 compares the edge value of each pixel of the edge map 135 to a threshold value (e.g., 30). Pixels with an edge value that meets or exceeds the threshold are identified as trailer pixels, whereas pixels with an edge value that does not meet or exceed the threshold are identified as ground disturbance pixels. Once the trailer pixels have been identified, the controller 38 determines one or more trailer contours at step 150. The trailer contour(s) is / are stored in the memory 42 of the controller 38 as a sample image at step 160 and may include a substantial entirety of the imaged trailer 12 or portions thereof. For illustrative purposes, Fig. 8, a trailer contour 152 is shown. As shown, the trailer contour 152 has a rectangular shape, which is generally more computationally efficient. In its current position, the trailer contour 152 can serve as a zero hitch angle reference and allows the hitch angle between the vehicle 14 and the trailer 12 to be determined in subsequent images (i.e., search images) via pattern matching at step 170.

[0021] According to one embodiment, as in Fig. 9, the hitch angle between the vehicle 14 and the trailer 12 may be determined based on a positional relationship between a template image 158 and a search image 171. In particular, the hitch angle may be determined by overlaying the template image 158 over the search image 171 such that the template image 158 is initially in a zero hitch angle position, and then rotating the template image 158 about a pivot point, preferably about the mapped hitch point 172. The direction of rotation may be predicted based on information received from the steering angle sensor 64 or other sensors, from which an initial assessment may be made regarding the angular position of the trailer 12 relative to the vehicle 14.Once the pattern image 158 has been matched to the search image 171, the angle θ by which the pattern image 158 is rotated relative to the zero hitch angle position can be correlated with the hitch angle between the vehicle 14 and the trailer 12.

[0022] According to one embodiment, the mapped coupling point 172 may be determined using an elimination process. For example, the controller 38 may, as exemplified in Fig. 10, define a number of hitch point location candidates 173a-173d positioned along a reference line 174 extending vertically across the center column of the search image 171. The reference line 174 is defined by the controller 38 and is assumed to coincide with the central longitudinal axis of an imaged drawbar 175 and to intersect the hitch point 172 of the imaged vehicle 14 and trailer 12. The hitch point location candidates 173a-173d are shown as evenly spaced along the reference line 174, but may vary in number and spacing in other embodiments.Once the template image 158 has been derived and the vehicle 14 and trailer 12 are moving along a curvilinear trajectory, the controller 38 may overlay the template image 158 on the search image 171 at the zero hitch angle position and rotate the template image 158 around each of the hitch point location candidates 173a-173d in an attempt to match the template image 158 to the search image 171. Based on the matching quality, each hitch point location candidate 173a-173d is given a confidence score, and the hitch point location candidate 173a-173d receiving the highest confidence score is selected as the hitch point.In the event that the matching quality associated with each hitch point location candidate 173a-173d is below a predetermined threshold, the controller 38 may define additional hitch point location candidates (not shown) along the reference line 174 in one or both directions from the hitch point location candidate 173a-173d that received the highest confidence rating and perform pattern matching with respect to each of the additional hitch point location candidates. This process may be iterated as many times as necessary until the predetermined threshold is met. By doing so, the location of the hitch point location candidate ultimately selected as the mapped hitch point will accurately reflect the location of the actual hitch point 172.

[0023] During the comparison of the pattern image 158 with the search image 171, the controller 38 may additionally determine the occurrence of an impending collapse scenario at step 180. Further referring to Fig. 10, the displacement of the pattern image 158 relative to a proximity zone 182 may be monitored while the pattern image 158 is rotated about the pivot point. In the illustrated embodiment, the proximity zone 182 may be defined as the space between an imaged rear bumper 184 of the vehicle 14 and a boundary line 186 defined by the controller 38 and superimposed on the search image 171. The boundary line 186 may be V-shaped and include a pair of straight segments 188 extending outward at an angle from a point 189 located on the reference line 174 and disposed between the imaged hitch point 172 and the imaged rear bumper 184. It should be understood that the boundary line 186 may take other shapes in alternative embodiments.The location and shape of the boundary line 186 can be determined based on various factors, including, but not limited to, vehicle speed, trailer length, drawbar length, imager characteristics, trailer contour, and vehicle contour. It is generally assumed that the vehicle speed, trailer length, drawbar length, and imager characteristics are known or otherwise measured and input into the trailer backup assist system 10. A vehicle contour, such as that of the depicted rear bumper 184, may be programmed at the factory.

[0024] If the pattern image 158 extends into the proximity zone 182 of the search image 171, the controller 38 determines at step 190 that an impending collapse scenario exists and initiates a collapse countermeasure. Otherwise, if it is determined that no impending collapse scenario exists, the controller 38 may proceed to determine the hitch angle between the vehicle 14 and the trailer 12, as previously discussed with reference to step 170. The collapse countermeasure may include generating an audible warning via the vehicle warning system 74, generating a visual warning via the display 84, generating a braking command to the vehicle braking control system 70, reducing the torque of the powertrain control system 72, modifying the steering angle of the vehicle 14, or a combination thereof, in addition to any other conceivable countermeasures.Because the trailer 12 is likely to be moving when the controller 38 determines that an impending collapse scenario is present, it is generally desirable to locate and size the proximity zone 182 in a manner that allows sufficient time to detect a collapse scenario, thereby minimizing the potential for an actual collapse and / or collision between the trailer 12 and the vehicle 14. Doing so also overcomes any response latency that may be inherent in the trailer backup assist system 10. Although steps 170 and 180 have been illustrated in a linear manner, it should be understood that both steps may be performed concurrently. Key to symbols

[0025] Fig. 2 10 TRAILER REVERSING ASSISTANCE SYSTEM 34 IMAGING DEVICE 38 CONTROL 40 MICROPROCESSOR 42 STORAGE 44 CLUTCH ANGLE DETECTION ROUTINE 46 OPERATION ROUTINE 48 VEHICLE SENSOR MODULE 50 SPEED SENSOR 52 Yaw Rate Sensor 54 STEERING INPUT DEVICE 56 POWER STEERING SYSTEM 58 ROTARY KNOB 62 ELECTRIC STEERING MOTOR 64 STEERING ANGLE SENSOR 68 TORQUE SENSOR 70 VEHICLE BRAKE CONTROL SYSTEM 72 POWERTRAIN CONTROL SYSTEM 74 VEHICLE WARNING SYSTEM 76 BRAKE LIGHTS 78 HORN 80 SPEAKERS 82 VEHICLE MMS

Claims

[1] A system for detecting a coupling angle between a vehicle (14) and a trailer (12), comprising: an imaging device (34) configured to capture images of the trailer (12); a controller (38) designed to: Processing the images captured by the imaging device (34); Deriving a pattern image (158) with a trailer contour (152) by: Deriving an averaged image from all images captured by the imaging device (34) during a period in which the vehicle (14) and the trailer (12) are moving in a straight direction; Calculating an edge value for each pixel of the averaged image; Comparing the edge value of each pixel with a threshold to identify trailer pixels and ground pixels; and Determining the trailer contour (152) based on the identified trailer pixels; and Matching the sample image (158) with a search image (171); wherein the coupling angle is determined based on a positional relationship between the pattern image (158) and the search image (171); wherein the controller (38) compares the pattern image (158) with the search image (171) by rotating the pattern image (158) relative to the search image (171) about a pivot point; and wherein the coupling angle correlates with an angle by which the pattern image (158) is rotated relative to the search image (171) to produce a match therebetween. [2] The system of claim 1, wherein pixels with edge values ​​that meet or exceed the threshold are identified as trailer pixels and pixels with edge values ​​that do not meet or exceed the threshold are identified as ground pixels. [3] The system of claim 1, wherein the controller (38) monitors a displacement of the trailer contour (152) relative to a proximity zone (182) in the search image (171) and initiates a collapsing countermeasure if the trailer contour (152) extends into the proximity zone (182). [4] The system of claim 3, wherein the proximity zone (182) is defined as a space between an imaged rear bumper (184) of the vehicle (14) and a boundary line (186) defined by the controller (38) and superimposed onto the search image (171). [5] The system of claim 3, wherein the collapse countermeasure comprises generating an audible warning via a vehicle warning system (74), generating a visual warning via a vehicle display (84), generating a braking command to a vehicle braking control system (70), reducing a torque of a powertrain control system (72), modifying a steering angle of the vehicle (14), or a combination thereof. [6] A system for detecting a coupling angle between a vehicle (14) and a trailer (12), comprising: an imaging device (34) configured to capture images of the trailer (12); a controller (38) designed to: Processing the images captured by the imaging device (34); Deriving a pattern image (158) with a trailer contour (152) by: Deriving an averaged image from all images captured by the imaging device (34) during a period in which the vehicle (14) and the trailer (12) are moving in a straight direction; Calculating an edge value for each pixel of the averaged image; Comparing the edge value of each pixel with a threshold to identify trailer pixels and ground pixels; and Determining the trailer contour (152) based on the identified trailer pixels; Rotating the pattern image (158) relative to a search image (171) about a depicted coupling point (172) common to the pattern image (158) and the search image (171); and Determining the coupling angle based on an angle by which the sample image (158) is rotated relative to the search image (171) to produce a match therebetween. [7] The system of claim 6, wherein pixels with edge values ​​that meet or exceed the threshold are identified as trailer pixels and pixels with edge values ​​that do not meet or exceed the threshold are identified as ground pixels. [8] System according to one of claims 6 or 7, wherein the controller (38) monitors a displacement of the trailer contour (152) relative to a proximity zone (182) in the search image (171) and initiates a collapsing countermeasure if the trailer contour (152) extends into the proximity zone (182). [9] The system of claim 8, wherein the proximity zone (182) is defined as a space between an imaged rear bumper (184) of the vehicle (14) and a boundary line (186) defined by the controller (38) and superimposed onto the search image (171). [10] The system of claim 8, wherein the collapse countermeasure comprises generating an audible warning via a vehicle warning system (74), generating a visual warning via a vehicle display (84), generating a braking command to a vehicle braking control system (70), reducing a torque of a powertrain control system (72), modifying a steering angle of the vehicle (14), or a combination thereof. [11] A method for detecting a coupling angle between a vehicle (14) and a trailer (12), comprising the following steps: Capturing images of the trailer (12) using an imaging device (34); Providing a controller (38) designed to: Processing the images captured by the imaging device (34); Deriving a pattern image (158) with a trailer contour (152) by: Deriving an averaged image from all images captured by the imaging device (34) during a period in which the vehicle (14) and the trailer (12) are moving in a straight direction; Calculating an edge value for each pixel of the averaged image; Comparing the edge value of each pixel with a threshold to identify trailer pixels and ground pixels; and Determining the trailer contour (152) based on the identified trailer pixels; and Matching the sample image (158) with a search image (171); wherein the coupling angle is determined based on a positional relationship between the pattern image (158) and the search image (171); wherein the controller (38) compares the pattern image (158) with the search image (171) by rotating the pattern image (158) relative to the search image (171) about a pivot point; and wherein the coupling angle correlates with an angle by which the pattern image (158) is rotated relative to the search image (171) to produce a match therebetween. [12] The method of claim 11, wherein pixels with edge values ​​that meet or exceed the threshold are identified as trailer pixels and pixels with edge values ​​that do not meet or exceed the threshold are identified as ground pixels. [13] The method of claim 11, wherein the controller (38) monitors a displacement of the trailer contour (152) relative to a proximity zone (182) in the search image (171) and initiates a collapsing countermeasure if the trailer contour (152) extends into the proximity zone (182). [14] The method of claim 13, wherein the proximity zone (182) is defined as a space between an imaged rear bumper (184) of the vehicle (14) and a boundary line (186) defined by the controller (38) and superimposed onto the search image (171). [15] The method of claim 13, wherein the collapsing countermeasure comprises generating an audible warning via a vehicle warning system (74), generating a visual warning via a vehicle display (84), generating a braking command to a vehicle braking control system (70), reducing a torque of a powertrain control system (72), modifying a steering angle of the vehicle (14), or a combination thereof.

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