Trailer reverse assist system with predictive hitch angle function

Abstract

A trailer back-up assist system is provided herein. The system includes a calibration feature for calibrating an imaging device for hitch angle detection. The system also employs a plurality of hitch angle detection methods, many of which can be run in parallel to increase the interval over which hitch angles can be measured. The system additionally includes a prediction feature in which the hitch angle can be predicted in the event of a trailer sensing device failure. The system is further configured to estimate a trailer length and generate a steering command that is invariant to the estimated trailer length under certain conditions.

Description

Technical Field

[0001] The present invention generally relates to systems for assisting a driver in reversing a trailer, and more particularly to systems using imager-based hitch angle detection. Background Art

[0002] Backing up a vehicle while towing a trailer can be challenging for many drivers, especially for drivers who do not often drive with a trailer or who drive with various types of trailers. Some systems for assisting the driver in backing up a trailer rely on hitch angle measurements to determine the position of the trailer relative to the vehicle. Therefore, the accuracy and reliability of the hitch angle measurements may be critical to the operation of the trailer back-up assist system. In systems that employ imager-based hitch angle detection, improper calibration of the imaging device may result in inaccurate hitch angle measurements. In addition, in the event that the imaging device is obstructed, such systems may be forced offline and unable to determine the hitch angle between the vehicle and the trailer. In order to operate correctly, some systems require the user to input measurements such as the length of the trailer. This is not only cumbersome for the user, but may also result in erroneous measurements being input into the system. Therefore, there is a need for a trailer back-up assist system that overcomes the above-mentioned problems. The present disclosure is intended to meet this need. Summary of the invention

[0003] According to a first aspect of the present invention, a calibration method is provided. The method comprises the following steps: capturing an image of a rear bumper using an imaging device; and providing a controller configured to: process the captured image, identify a boundary separating the rear bumper from the ground, compare the identified boundary with an ideal boundary, and determine an offset between the identified boundary and the ideal boundary.

[0004] Embodiments of the first aspect may include any one or a combination of the following features:

[0005] ● the ideal boundary comprises a continuous line;

[0006] The ideal boundary includes a line with a break;

[0007] ● the ideal boundary is overlaid on the captured image;

[0008] The offset is defined by a vector having a horizontal component, a vertical component and a rotational component;

[0009] The controller determines the offset by iterating candidate values ​​for each of the horizontal component, the vertical component, and the rotational component until the identified boundary overlaps the ideal boundary; and

[0010] • The controller is further configured to generate a warning when the offset cannot be determined.

[0011] According to a second aspect of the present invention, a trailer back-up assist system is provided. The system comprises: a device configured to sense a trailer; and a controller configured to determine a coupling angle between a vehicle and the trailer based on data provided by the device. If the device fails, the controller predicts the coupling angle based on the latest known coupling angle, the latest known angular velocity of the trailer, and the execution cycle time.

[0012] Embodiments of the second aspect may include one or a combination of the following features:

[0013] • the device comprises an imaging device, and the controller is configured to predict the hitch angle in the event that the imaging device is obstructed or otherwise fails;

[0014] The controller is further configured to predict the hitch angle until an error band reaches a threshold;

[0015] The controller is further configured to determine an upper error band and a lower error band of the predicted hitch angle and formulate a countermeasure if the upper error band reaches a maximum controllable hitch angle or the lower error band reaches a minimum controllable hitch angle, whichever occurs first;

[0016] The upper error band and the lower error band are each determined based on a predicted hitch angle, an initial degree error when the device fails, a cumulative vehicle travel distance, and a trailer length;

[0017] The countermeasure comprises at least one of: steering the vehicle to prevent exceeding the maximum controllable hitch angle or the minimum controllable hitch angle, and reducing the speed of the vehicle; and

[0018] • The most recently known angular velocity is based on the angular velocity adjusted by a percentage error.

[0019] According to a third aspect of the present invention, there is provided a method for determining a hitch angle between a vehicle and a trailer. The method comprises the following steps: selecting at least one hitch angle detection method from among a plurality of hitch angle detection methods; determining the hitch angle between the vehicle and the trailer using the selected at least one hitch angle detection method; and switching to another hitch angle detection method when the selected at least one hitch angle detection method becomes unavailable.

[0020] Embodiments of the third aspect may include one or a combination of the following features:

[0021] ● The plurality of mounting angle detection methods each employs imager-based mounting angle detection;

[0022] ● ranking the plurality of hitch angle detection methods based on a confidence score assigned to each hitch angle detection method, and wherein the at least one selected hitch angle detection comprises the available hitch angle detection method having the highest confidence score;

[0023] ● the step of limiting said speed of said vehicle based on said confidence score assigned to said at least one selected hitch angle detection method;

[0024] ● step of predicting the hitch angle during a transition between the at least one selected hitch angle detection method and another hitch angle detection method, or when each of the plurality of hitch angle detection methods becomes unavailable; and

[0025] - The step of using said determined hitch angle to control at least one of a hitch angle operating range, a speed limit of said vehicle and said curvature of a reverse path of said trailer.

[0026] According to a fourth aspect of the present invention, a trailer back-up assist system is provided. A steering input device is configured to provide a curvature command based on a user input. A controller is configured to estimate a trailer length based on a vehicle and trailer yaw rate. The controller generates a steering command based on the estimated trailer length, the curvature command, a maximum steering angle, and a vehicle speed. The generated steering command is constant for the estimated trailer length under certain conditions.

[0027] Embodiments of the fourth aspect may include one or a combination of the following features:

[0028] The steering input device includes a rotatable knob configured to allow a user to input a desired direction and curvature of a reverse path for a trailer being reversed by the vehicle;

[0029] The controller includes a curvature input scaling module configured to scale the curvature command by a maximum effective curvature to generate a curvature input based on the maximum steering angle and the estimated trailer length;

[0030] The controller further includes a curvature mapping module configured to generate a reference hitch angle based on the curvature input and the estimated trailer length;

[0031] The controller further includes a subtractor configured to subtract an estimated hitch angle from the reference hitch angle to generate a signal provided to a proportional-integral (PI) controller configured to generate a control variable, wherein the estimated hitch angle is based on the vehicle and trailer yaw rates;

[0032] The controller further comprises a hitch angle controller configured to generate the steering angle based on the control variable, the estimated trailer length and the vehicle speed;

[0033] The controller further comprises a scaling factor for the PI controller, the scaling factor for the PI controller being based solely on the estimated trailer length such that a transient response of the controller is invariant to the estimated trailer length; and

[0034] • The certain conditions include one of a zero curvature command, a maximum curvature command, and a minimum curvature command.

[0035] These and other features, advantages and objects of the present invention will be further understood and appreciated by those skilled in the art by referring to the following description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the attached picture:

[0037] Figure 1 is a top perspective view of a vehicle with a trailer attached having one embodiment of a hitch angle sensor for operating a trailer reverse assist system;

[0038] Figure 2 is a block diagram illustrating one embodiment of a trailer reverse assist system;

[0039] Figure 3 Shows the kinematic relationship between the vehicle and the trailer;

[0040] Figure 4 A steering input device having a rotatable knob is shown for operating a trailer reverse assist system;

[0041] Figure 5 a schematic diagram showing a rotatable knob for selecting a desired curvature of the trailer and showing the correspondence of the vehicle and trailer for various trailer curvature paths associated with the selectable desired curvature;

[0042] Figure 6 is a flow chart of a method for calibrating an imaging device of a vehicle;

[0043] Figure 7 showing a captured image showing an edge of a rear bumper of a vehicle;

[0044] Figure 8 showing a captured image in which, according to one embodiment, an ideal boundary between a rear bumper and the ground is identified;

[0045] Fig. 9 showing a captured image in which, according to an alternative embodiment, an ideal boundary is identified;

[0046] Fig.10 showing a captured image in which an identified boundary is compared to an ideal boundary to determine an offset used in calibrating an imaging device;

[0047] Fig.11 is a graph showing the deviation between the actual hitch angle and the predicted hitch angle over a range of vehicle travel distances;

[0048] Fig.12 is a flow chart of a method for determining a hitch angle between a vehicle and a trailer;

[0049] Fig.13 A curvature input scaling module is shown for scaling a curvature command input using a steering input device;

[0050] Fig.14 A controller for a trailer backup assist system including a curvature input scaling module is shown; and

[0051] Fig.15 is a graph showing a family of closed loop balances as a function of curvature command for multiple estimated trailer lengths. DETAILED DESCRIPTION

[0052] For the purposes of the description herein, it should be understood that the disclosed trailer reverse assist system and related methods may adopt various alternative embodiments and orientations, unless expressly indicated to the contrary. It should also be understood that the specific devices and processes illustrated in the accompanying drawings and described in the following specification are merely exemplary embodiments of the inventive concepts defined in the appended claims. Although various aspects of the trailer reverse assist system and related methods are described with reference to specific illustrative embodiments, the disclosed invention is not limited to such embodiments, and additional modifications, applications, and embodiments may be implemented without departing from the disclosed invention. Therefore, unless the claims expressly state otherwise, specific dimensions and other physical characteristics associated with the embodiments disclosed herein should not be considered limiting.

[0053] As used herein, the term "and / or" when used to list two or more items means that any one of the listed items may be taken alone or the two or more listed items may be taken in any combination. For example, if a composition is described as containing components A, B, and / or C, the composition may contain only A; only B; only C; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0054] See also Figure 1 and Figure 2 , reference numeral 10 generally designates a trailer back-up assist (TBA) system for assisting a vehicle 12 in backing up a trailer 14. The vehicle 12 is embodied as a pickup truck pivotally attached to one embodiment of a trailer 14 having a box-shaped 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 14 also has a trailer hitch connector in the form of a coupler assembly 28 connected to a vehicle hitch connector in the form of a hitch ball 30 and a drawbar 31. The coupler assembly 28 latches onto the hitch ball 30 to provide a pivoting hitch 32 that allows for a hitch angle (e.g., hitch angle γ; Figure 3 ) articulation. As defined herein, the hitch angle corresponds to the angle formed between the central longitudinal axis of the vehicle 12 and the central longitudinal axis of the trailer 14. It should be appreciated that additional embodiments of the trailer 14 may alternatively be coupled to the vehicle 12 to provide a pivotal connection, such as by connecting with a fifth wheel connector. It is also contemplated that additional embodiments of the trailer 14 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.

[0055] The TBA system 10 also includes an imaging device 34 located at the rear of the vehicle 12 and configured to image a rear-vehicle scene. The imaging device 34 may be centrally located at an upper region of a vehicle tailgate 35 such that the imaging device 34 is elevated relative to the tongue 26 of the trailer 14. The imaging device 34 has a field of view 36 positioned and oriented to capture one or more images that may include, among other things, the tongue 26 and hitch ball 30 of the trailer 14. The image data is supplied to and processed by a controller 38 of the TBA system 10 to determine a hitch angle between the vehicle 12 and the trailer 14. Additional information regarding image-based hitch angle detection and associated methods may be found in commonly assigned U.S. Patent No. 9,610,975, issued on April 4, 2017 to Hu et al. and entitled “HITCH ANGLE DETECTION FOR TRAILERBACKUP ASSIST SYSTEM,” the entire disclosure of which is incorporated herein by reference.

[0056] The controller 38 is configured with a microprocessor 40 and / or other analog and / or digital circuitry for processing one or more logic programs stored in a memory 42. The logic programs may include a hitch angle detection program 44, an operation program 46, and a curvature program 47. Information from the imaging device 34 or other components of the TBA system 10 may be supplied to the controller 38 via the communication network of the vehicle 12, which may include a controller area network (CAN), a local interconnect network (LIN), or other conventional protocols used in the automotive industry. It should be appreciated that the controller 38 may be a stand-alone dedicated controller or may be a shared controller integrated with the imaging device 34 or other components of the TBA system 10, in addition to any other conceivable on-board or off-board vehicle control systems.

[0057] With respect to the present embodiment, the controller 38 is configured to communicate with a variety of vehicle devices. The TBA system 10 may include a vehicle sensor module 48 that monitors certain dynamics of the vehicle 12. The vehicle sensor module 48 may generate a plurality of signals that are sent to the controller 38, such as a vehicle speed signal generated by a speed sensor 50 and a vehicle yaw rate signal generated by a vehicle yaw rate sensor 52. A trailer sensor module 53 is provided that monitors certain dynamics of the trailer 14. The trailer sensor module 53 includes a trailer yaw rate sensor 54 that is configured to generate a trailer yaw rate signal that is provided to the controller 38.

[0058] A steering input device 55 is provided to enable the driver to control or otherwise modify the desired curvature of the reverse path of the trailer 14 (e.g., desired curvature 56; Figure 5). The steering input device 55 may be communicatively coupled to the controller 38 in a wired or wireless manner and provides input to the controller 38 defining a desired curvature of the reverse path of the trailer 14. In response to the input, the controller 38 generates a corresponding steering command, which is supplied to a power-assisted steering system 57 of the vehicle 12. In one embodiment, the steering input device 55 includes a rotatable knob 58 operable between a plurality of rotational positions, each rotational position providing an incremental change in the desired curvature 56 of the reverse path to the trailer 14.

[0059] The knob 58 may be rotatable about an axis of rotation extending through the top surface or face of the knob 58. In other embodiments, the knob 58 may be rotatable about an axis of rotation extending substantially parallel to the top surface or face of the knob 58. In addition, according to further embodiments, the steering input device 55 may include alternative devices for providing the desired input, such as a joystick, a keypad, a series of push-buttons or switches, a sliding input device, various user interfaces on a touch screen display, a vision-based system for receiving gestures, a control interface on a portable device, and other conceivable input devices generally understood by those of ordinary skill in the art. It is contemplated that the steering input device 55 may also be used as an input device for other features, such as providing input for other vehicle features or systems.

[0060] According to one embodiment, the controller 38 of the TBA system 10 may control the power steering system 57 of the vehicle 12 to operate the steering wheels 60 of the vehicle 12 for moving the vehicle 12 in a manner such that the trailer 14 reacts according to the desired curvature 56 of the reverse path of the trailer 14. The power steering system 57 may be an electric power steering (EPAS) system including an electric steering motor 62 for turning the steering wheels 60 to a steering angle based on a steering command generated by the controller 38, whereby the steering angle may be sensed by a steering angle sensor 64 of the power steering system 57 and provided to the controller 38. The steering command may be provided for autonomously steering the vehicle 12 during reverse operation, and may alternatively be provided manually by a rotational position (e.g., steering wheel angle) of a steering wheel 66 or a rotatable knob 58. However, in some embodiments, the steering wheel 66 of the vehicle 12 may be mechanically coupled to the steering wheel 60 of the vehicle 12 such that the steering wheel 66 moves in unison with the steering wheel 60 through internal torque, thereby preventing manual intervention through the steering wheel 66 during autonomous steering of the vehicle 12. In such cases, the power-assisted steering system 57 may include a torque sensor 68 that senses torque (e.g., clamping and / or turning) on ​​the steering wheel 66 that is not expected to come from autonomous control of the steering wheel 66 and, therefore, indicates manual intervention by the driver. In some embodiments, the external torque applied to the steering wheel 66 may be used as a signal to the controller 38 (i.e., the driver has assumed manual control) to cause the TBA system 10 to stop the autonomous steering function.

[0061] The controller 38 of the TBA system 10 may also communicate with the vehicle brake control system 70 of the vehicle 12 to receive vehicle speed information, such as individual wheel speeds of the vehicle 12. Additionally or alternatively, the vehicle speed information may be provided to the controller 38 via the powertrain control system 72 and / or the speed sensor 50, as well as other conceivable means. It is contemplated that the individual wheel speeds may be used to determine a vehicle yaw rate, which may be provided to the controller 38 as an alternative 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 a braking command to the vehicle brake control system 70, thereby allowing the TBA system 10 to adjust the speed of the vehicle 12 during reverse operation of the trailer 14. It should be appreciated that the controller 38 may additionally or alternatively adjust the speed of the vehicle 12 through interaction with the powertrain control system 72.

[0062] By interacting with the power steering system 57, the vehicle brake control system 70, and / or the powertrain control system 72 of the vehicle 12, the likelihood of an unacceptable trailer back-up condition occurring may be reduced. Examples of unacceptable trailer back-up conditions include, but are not limited to, vehicle overspeed conditions, high hitch angle rates, hitch angle dynamic instability, trailer jackknifing conditions, sensor failures, and the like. In such cases, the driver may not be aware of the failure until an unacceptable trailer back-up condition is about to occur or has occurred. Therefore, it is disclosed herein that the controller 38 of the TBA system 10 may generate an alert signal corresponding to a notification of an actual, impending, and / or anticipated unacceptable trailer back-up condition, and may generate countermeasure measures prior to driver intervention to prevent such an unacceptable trailer back-up condition from occurring.

[0063] According to one embodiment, the controller 38 may communicate with one or more devices including a vehicle alarm system 74 that may prompt visual, audible, and tactile warnings. For example, the vehicle brake lights 76 and the vehicle emergency flashers may provide visual warnings, and the vehicle horn 78 and / or the speaker 80 may provide audible warnings. In addition, the controller 38 and / or the vehicle alarm system 74 may communicate with a human machine interface (HMI) 82 of the vehicle 12. The HMI 82 may include a touch screen vehicle display 84, such as a center-stack mounted navigation or entertainment display capable of displaying an image indicative of the warning. Such an embodiment may be expected to notify the driver of the vehicle 12 that an unacceptable trailer back-up condition is occurring. In addition, it is contemplated that the controller 38 may communicate with one or more electronic portable devices, such as a portable electronic device 86 embodied as a smart phone, via wireless communication. 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 warnings.

[0064] When the imaging device 34 is mounted on the vehicle 12, it is important to minimize errors that may occur during or after the installation. Such errors are typically caused by improper alignment between the imaging device 34 and the vehicle 12 in terms of yaw, pitch, and roll. These errors may be caused by various factors, such as manufacturing variability, component-to-component variability over time, vehicle damage, or component replacement, for example, all of which may change the alignment between the imaging device 34 and the vehicle 12. Initially, these errors are calibrated, after which the imaging device 34 can be used to support functions such as imager-based hitch angle detection. If not properly calibrated, the resulting errors may negatively affect the accuracy and robustness of the functions provided by the imaging device 34.

[0065] See also Figure 6, a flow chart describing a method 90 for calibrating an imaging device (e.g., imaging device 34) that is typically mounted to the rear of a vehicle and configured to image a rear vehicle scene is shown. However, it should be understood that method 90 may be similarly configured for calibrating imaging devices located elsewhere on a vehicle.

[0066] At step 95, a reference installation is prepared. For example, the reference installation includes positioning the imaging device in a desired orientation relative to the vehicle. Figure 1 In an embodiment of the present invention, for example, the imaging device is ideally mounted to an upper region of the vehicle tailgate 35 and is oriented to capture images of the rear vehicle scene including the rear bumper. When the imaging device is ideally positioned, at step 100, the imaging device is operated to capture images including the rear bumper, which is similarly configured as the rear bumper 96 ( Figure 1 According to one embodiment, the images are captured against a homogenized background (e.g., a uniformly illuminated white wall), or compiled from a series of images captured while the vehicle is moving at a predefined speed. The speed may be a specific speed or speed range, and is typically selected to prevent excessive vibration of the imaging device and further allow the ground to be blurred in the compiled image.

[0067] At step 105, edge detection is performed on the captured image. For illustration purposes, Figure 7 1 is a sample captured image showing a detected edge (e.g., edge 106) of a rear bumper 96' that is similarly configured as the rear bumper 96 of the vehicle 12. At step 110, an ideal boundary between the rear bumper and the ground is identified in the captured image based on the one or more edges detected at step 105. For illustration purposes, Figure 8 Shown in Figure 7 An ideal boundary 111 is identified between the detected edge 106 and the ground 112. As shown, the ideal boundary 111 is a continuous line across the image and separates the rear bumper 96 from the ground 112. Fig. 9 In the alternative embodiment shown, the ideal boundary 111 includes a central break and is identified from an edge that appears only in the lower corner portion 113 of the captured image. In other words, when identifying the ideal boundary 111, the main portion 114 of the captured image is ignored. The main portion generally corresponds to an area in the captured image where a valid boundary is unlikely to exist. Optionally, as Fig. 9As shown, the main portion 114 includes a lower center area 114' of the captured image to avoid processing areas where the trailer hitch connector can be detected and may disrupt the shape of the ideal boundary 111. By ignoring certain portions of the captured image, the size of the captured image is effectively reduced, thereby allowing the ideal boundary 111 to be identified more quickly. In yet another alternative embodiment, the ideal boundary 111 can be generated from a computer picture or the like. At step 115, the ideal boundary 111 and its location are recorded for later use in calibrating other imaging devices of the same model and similarly installed on the same vehicle model. Therefore, it should be understood that steps 95-115 only need to be performed once for each vehicle model. In this way, if desired, steps 95-115 can be performed in a laboratory environment.

[0068] In contrast, steps 120-150 are typically performed on an assembly line and repeated for each vehicle of the same model. Figure 1 The embodiment of the vehicle 12 shown describes steps 120-150. At step 120, the ideal boundary 111 and its position predetermined at step 110 are provided to the controller 38 (e.g., stored on the memory 42). Next, at step 125, the controller 38 operates the imaging device 34 to capture an image including the rear bumper 96 of the vehicle 12. At step 130, the controller 38 processes the captured image to identify the boundary between the rear bumper 96 of the vehicle 12 and the ground. When the boundary is identified, the controller 38 compares the position of the identified boundary with the position of the stored ideal boundary 111. For example, the stored ideal boundary 111 can be overlaid on the captured image. If the position of the identified boundary overlaps with the position of the stored ideal boundary 111, the installation of the imaging device 34 is complete and no calibration is required. In other words, the imaging device 34 is installed correctly and is ready for use. In this way, the method 90 ends at step 140.

[0069] Alternatively, if the location of the identified boundary fails to overlap with the location of the stored ideal boundary 111, the controller 38 determines the offset between the identified boundary and the stored ideal boundary 111 at step 145. For illustration purposes, Fig.10 1 is a sample image showing the identified boundary 146 offset relative to the stored ideal boundary 111. In the depicted embodiment, the offset is defined as a vector having a horizontal component X, a vertical component Y, and a rotational component θ. It is contemplated that the offset can be determined by iterating reasonable candidate values ​​for each of the components X, Y, and θ until the identified boundary 146 overlaps the stored ideal boundary 111, or vice versa. When the offset is determined, calibration of the imaging device 34 is complete, and the imaging device 34 is now ready for use. Thus, the method 100 ends at step 150.

[0070] It will be appreciated that the imaging device 34 may be calibrated multiple times during the life of the vehicle 12. For example, it is contemplated that the foregoing steps may be performed at regular intervals, i.e., once per ignition cycle, when replacement of the imaging device 34 is detected, and / or when a collision is detected. It is further contemplated that the controller 38 may inhibit calibration of the imaging device 34 when, for example, the orientation and / or position of the rear bumper 96 has changed significantly, the shape of the identified boundary 146 does not match the stored ideal boundary 111 (typically due to damage or modification of the rear bumper 96), the rear bumper 96 is not securely attached to the vehicle 12, or the imaging device 34 is not securely fixed to the vehicle 12 (e.g., the tailgate 35 is not secure). Additionally or alternatively, calibration of the imaging device 34 may be inhibited when the values ​​of the components X, Y, and θ exceed one or more predetermined thresholds or when the error between the pixels of the boundary and the pixels of the identified boundary exceeds a threshold.

[0071] In the event that the controller 38 inhibits calibration of the imaging device 34, a warning may be provided to the user of the TBA system 10. The warning may be generated by the controller 38 and executed by existing vehicle components such as, for example, the display 34, the speaker 80, and the portable electronic device 86. It is contemplated that the warning may be visual, audible, tactile, or a combination thereof. In the event that damage to the vehicle 12 is detected (e.g., by inertial and / or peripheral sensors), the TBA system 10 may store a corresponding diagnostic trouble code (DTC) and / or warn the user that the imaging device 34 and / or the rear bumper 96 may require repair.

[0072] As described herein, the TBA system 10 has, among other features, imager-based hitch angle detection. As a drawback, there are situations that may prevent the imaging device 34 from tracking the trailer 14 or other objects in the imaging scene used for hitch angle detection. For example, obstruction may occur when debris or other objects are deposited on the lens of the imaging device 34, the imaging device 34 experiences glare due to direct sunlight, or the imaging device 34 is unable to reliably image key features in the scene. In such situations where the imaging device 34 is obstructed, it is expected that the TBA system 10 may report the condition to the driver and may additionally stop imager-based hitch angle detection and any other functions that rely on image data processing. Although such situations are generally uncommon, the driver may be frustrated if certain functions of the TBA system 10 become unavailable. Therefore, a solution is needed that minimizes the downtime of image-based hitch angle detection caused by the inability of the imaging device 34 to reliably image the scene.

[0073] In this case, the TBA system 10 may be configured to predict the hitch angle using a "predictive model approach" which may be embodied in the hitch angle detection routine 44 and will be referred to below. Figure 3 Describing in more detail, Figure 3 The kinematic relationship between the vehicle 12 and the trailer 14 is shown. To predict the hitch angle, the controller 38 first determines the angular velocity of the trailer 14 It can be determined by the following equation:

[0074]

[0075] in:

[0076] γ is the coupling angle (β-α) between the vehicle 12 and the trailer 14,

[0077] δ is the steering angle of the steering wheel 60 of the vehicle 12,

[0078] L is the length of the drawbar between the hitch 32 and the rear axle 155 of the vehicle 12,

[0079] D is the trailer length between the hitch 32 and the effective axle 20 of the trailer 14,

[0080] W is the wheelbase length between the front axle 157 and the rear axle 155 of the vehicle 12, and v is the longitudinal velocity of the vehicle 12. It should be noted that the function corresponds to the yaw rate of the vehicle 12 and can be determined by the vehicle yaw rate sensor 52 ( Figure 2 ) is supplied by other means.

[0081] In calculating the angular velocity of the trailer 14 When the trailer length D, the drawbar length L and the wheelbase length W are assumed to be known, the steering angle δ and the longitudinal speed v can be respectively measured by the steering angle sensor 64 ( Figure 2 ) and speed sensor 50( Figure 2 ) is readily provided to the controller 38. Under normal operating conditions, the hitch angle γ may be determined according to any known imager-based hitch angle detection method. Thus, as long as the imaging device 34 is not obstructed, or in other words, is able to reliably track the trailer 14, the controller 38 is able to determine the angular velocity of the trailer 14

[0082] However, if the imaging device 34 is suddenly obstructed such that imager-based hitch angle detection becomes unavailable, the controller 38 may determine the hitch angle based on information including the last known hitch angle, the last known angular velocity of the trailer 14, and an image processor (e.g., microprocessor 40, Figure 2 ) is used to predict the hook angle based on the predetermined information of the execution cycle time of the 2000-010 ...

[0083]

[0084] in:

[0085] γ p is the predicted attachment angle,

[0086] γ lk is the latest known mounting angle,

[0087] is the latest known angular velocity of the trailer 14, and

[0088] t c is the execution cycle time of the image processor. Therefore, as long as the controller 38 is able to iterate Equation 1 at least once before the imaging device 34 is blocked, the controller 38 will have sufficient information to predict the hook angle γ by iterating Equation 2 p The controller 38 can again calculate the angular velocity of the trailer 14 This is done by dividing the predicted hook angle γ p Substitute into equation 1 and then predict the hook angle γ again p , which is obtained by recalculating the angular velocity using As the latest known angular velocity Thus, by progressively re-iterating Equations 1 and 2, the controller 38 is able to predict the hitch angle in situations where imager-based hitch detection is unavailable or otherwise unreliable.

[0089] The prediction model approach outlined above can be implemented for extended durations. However, over time, the predicted hook angle may begin to deviate from the true or actual hook angle. Fig.11 , shows a graph showing the deviation between the actual hitch angle and the predicted hitch angle within a range of vehicle travel distance D. For exemplary purposes, when the imaging device 34 is at any distance D 0 As the vehicle 12 continues to travel, the error bands for the predicted hitch angles, shown as an upper error band and a lower error band, begin to increase exponentially relative to the vehicle's travel distance D. Thus, as the vehicle's travel distance increases, the hitch angle predictions tend to lose reliability. In operation, the controller 38 continues to predict the hitch angle until the error band reaches a threshold. For example, the controller 38 will stop predicting the hitch angle when the upper error band reaches the maximum controllable hitch angle 160 or the lower error band reaches the minimum controllable hitch angle 162, whichever occurs first. In the illustrated embodiment, the upper error band is shown at a distance D. 最大 The maximum controllable hitch angle is reached, thus prompting the controller 38 to stop predicting the hitch angle.

[0090] The error in degrees between the predicted hitch angle and the true hitch angle is determined by the following equation:

[0091]

[0092] in:

[0093] e is the error in degrees,

[0094] e 0 is the initial degree error when the imaging device 34 is obstructed (e.g., 0.5 to 1 degree, depending on the accuracy of the hitch angle detection),

[0095] s is the cumulative vehicle distance traveled as determined by the odometer of the vehicle 12, and

[0096] D is the trailer length, which is assumed to be known.

[0097] Knowing the degree error e, the error band is determined by the following equation:

[0098] γ + =γ p +e (4)

[0099] γ - =γ p -e (5)

[0100] in:

[0101] γ + is the upper error band,

[0102] γ - is the lower error band,

[0103] γ p is the predicted hitch angle determined by Equation 2, and

[0104] e is the degree error determined by Equation 3. Alternatively, the determination of the upper and lower error bands may include an error adjustment incorporated into each iteration of Equation 1. That is, the angular velocity determined using Equation 1 The percentage error is adjusted, and the adjusted angular velocity is then used as the latest known angular velocity This is when the predicted hitch angle γ in Equation 2 p It is carried out at the time.

[0105] Specifically, relative to the upper error band γ + , angular velocity The adjustment made is given by the following equation:

[0106]

[0107] Relative to the lower error band γ - , angular velocity The adjustment made is given by the following equation:

[0108]

[0109] in:

[0110] is the adjusted angular velocity,

[0111] is the angular velocity determined in Equation 1, and

[0112] ε is the percentage error and is derived experimentally. Therefore, from Equations 6 and 7, it can be seen that the adjusted angular velocity associated with the upper and lower error bands is will be different and therefore produce a different predicted attachment angle γ p , which is when the angular velocity is used as the latest known angular velocity in equation 2 Therefore, Equation 2 is iterated twice, once using the adjusted angular velocity determined in Equation 6 and the second time using the adjusted angular velocity determined in Equation 7 Each resulting predicted attachment angle γ p Then, it is used to determine the upper error band γ in the corresponding equations 4 and 5 respectively. + and the lower error band γ - .

[0113] In the upper error band γ + Approaching or reaching the maximum controllable hook angle or lower error band γ - When the minimum controllable hitch angle is reached, the controller 38 may formulate countermeasures. For example, the countermeasures may include providing power steering system 57 ( Figure 2 ) provides a steering command for steering the vehicle 12 to attempt to prevent the hitch angle from exceeding the maximum controllable hitch angle or falling below the minimum controllable hitch angle. Additionally or alternatively, the countermeasure may include providing a vehicle brake control system 70 ( Figure 2 ) provides a braking command to reduce the speed of the vehicle 12. Still additionally or alternatively, the countermeasures may include: instructing the driver to clean the lens of the imaging device 34, instructing the driver to control the steering input device 55 ( Figure 2 ), ramping out steering control, taking the autonomous steering function offline, or a combination thereof. In some embodiments, one or more countermeasures may be applied at a predetermined vehicle travel distance that occurs within the upper error band or the lower error band γ. + , γ - Before reaching the maximum or minimum controllable hitch angle, respectively.

[0114] In the present embodiment, the controller 38 implements the error band determination and serves as an image processor and a steering controller. In alternative embodiments where the image processor and the steering controller are separated, it is contemplated that the error band determination may be implemented by the image processor, the steering controller, or a combination thereof. Typically, if the image processor and the steering controller are used together to implement the error band determination, additional traffic on the vehicle communication network (e.g., a CAN bus) may be avoided at the expense of additional hardware. If only the steering controller is used to implement the error band determination, higher accuracy may be achieved at the expense of increased traffic on the vehicle communication network. Alternatively, if only the image processor is used to implement the error band determination, additional traffic on the vehicle communication network may be avoided at the expense of accuracy. In the case where only one of the image processor and the steering controller is used to implement the error band determination, a copy of the error band may be supplied to the other of the image processor and the steering controller. Typically, when no network interface (e.g., a CAN interface) accommodates the transmission of the error band signal, it is preferred to use both the image processor and the steering controller to implement the error band determination.

[0115] It should be appreciated that the predictive model approach described herein may be used to mitigate failures in other devices configured to sense the trailer 14. Such devices may include yaw rate sensors, Hall effect sensors, rotary potentiometers, etc. In operation, the controller may use data from these devices to predict the hitch angle between the vehicle and the trailer. Thus, if one of these devices becomes unavailable due to a failure or some other factor, the predictive model approach may be used to determine the hitch angle.

[0116] See also Fig.12 , a method for determining the hitch angle between the vehicle 12 and the trailer 14 is shown. The method may be executed by the controller 38 of the TBA system 10 and may be embodied in the hitch angle detection program 44. At step 170, the controller 38 selects at least one hitch angle detection method from a plurality of hitch angle detection methods. The hitch angle detection methods may each employ imager-based hitch angle detection and include any hitch angle detection method described in U.S. Pat. No. 9,610,975 to Hu et al. For example, the hitch angle detection method may include a template matching method, a centerline method, and / or a steady-state method, as described in U.S. Pat. No. 9,610,975. It is contemplated that the hitch angle detection methods may be ranked based on a confidence score assigned to each hitch angle detection method. The confidence score may be based on the reliability and / or robustness of a given hitch angle detection method. For example, the template matching method is typically the most reliable and robust, followed by the steady-state method and the centerline method. Thus, the at least one selected hitch angle detection method typically comprises the available hitch angle detection method having the highest confidence score.

[0117] At step 175, the controller 38 determines the hitch angle between the vehicle 12 and the trailer 14 using the selected at least one hitch angle detection method. In determining the hitch angle, other relevant data may become available, such as, but not limited to: hitch angle error band, hitch angle rate, hitch angle rate error band, hitch angle accuracy, etc. According to one embodiment, it is contemplated that all hitch angle detection methods may be used in parallel to determine the hitch angle, and the hitch angle determined by the hitch angle detection method with the highest confidence score is used by the TBA system 10 to employ a function related to the backing up of the trailer 14. In other embodiments, only the hitch angle detection method with the highest confidence score is used. Alternatively, if desired, some but not all of the hitch angle detection methods may be used in parallel. In any case, it is contemplated that the number of hitch angle detection methods selected may be limited by the hardware performance of the TBA system 10 or certain components thereof (e.g., the imaging device 34 and the controller 38). In this way, the number of hitch angle detection methods used in parallel can be selected so as to minimize the computational strain on the TBA system 10 and / or related components. In addition, it is contemplated that the controller 38 can limit the speed of the vehicle 12 based on the confidence score assigned to the at least one selected hitch angle detection method. That is, the lower the confidence score, the greater the speed limit imposed on the vehicle 12. In order to limit the speed of the vehicle 12, the controller 38 can output a braking command to the vehicle brake control system 70 of the vehicle 12.

[0118] At step 180, when at least one of the selected hitch angle detection methods becomes unavailable, the controller 38 switches to another hitch angle detection method. As described herein, imager-based hitch angle detection relies on the ability of the imaging device 34 to accurately capture images of the rear vehicle scene and generally including the trailer 14 or its components. As such, the image quality of the images captured by the imaging device 34 may be impaired when the imaging device 34 is obstructed by debris on the lens, glare from the sun, etc. Therefore, there may be situations where some hitch angle detection methods are available while other hitch angle detection methods are not available.

[0119] If the image quality of the captured image drops below a threshold associated with a specific hook angle detection method, the controller 38 may determine that the specific hook angle detection method has become unavailable. Therefore, in an embodiment where only the hook angle detection method with the highest confidence score is used and the method suddenly becomes unavailable, the controller 38 may switch to another hook angle detection method that is available and has the next highest confidence score. In an embodiment where some but not all hook angle detection methods are used in parallel, if one of the selected hook angle detection methods suddenly becomes unavailable, the controller 38 may replace it with another hook angle detection method that is available and has the highest confidence score among the unselected hook angle detection methods. In this way, the total selected hook angle detection method being used remains unchanged. By using more than one hook angle detection method, the hook angle can be determined at a larger interval because each selected hook angle detection method may require a certain period of time to determine the hook angle. Therefore, by increasing the number of hook angle detection methods being used, the possibility of being able to determine the hook angle at any given point in time is increased.

[0120] At step 185, during a transition between at least one selected hitch angle detection method and another hitch angle detection method, or when each of the multiple hitch angle detection methods becomes unavailable, the controller 38 predicts the hitch angle. To predict the hitch angle, the controller 38 may use the prediction model method previously described herein. In some embodiments, regardless of which one or more methods are used to determine the hitch angle, the controller 38 may apply a digital filter to the determined hitch angle and other trailer-related data. At step 190, the controller 38 uses the determined or predicted hitch angle to control the hitch angle operating range, the speed limit of the vehicle 12, and the desired curvature 56 (of the reverse path of the trailer 14) of the vehicle 12. Figure 5 ). For example, if the determined or predicted hitch angle has a hitch angle accuracy of ±10% and the TBA system 10 has a maximum controllable hitch angle of 50 degrees, the controller 38 may limit the maximum controllable hitch angle to 40 degrees according to the hitch angle accuracy of the determined hitch angle. In addition, the controller 38 may limit the speed of the vehicle 12 or bring the vehicle 12 to a complete stop at some predetermined deceleration of the trailer 14.

[0121] Existing TBA systems may utilize a curvature program that requires the driver to measure the trailer length D for input into the system memory. Such systems exhibit certain disadvantages, such as the introduction of human error and / or the inability of the TBA system to operate immediately upon coupling, for example, the trailer 14 to the vehicle 12. Therefore, the present controller 38 may include in the curvature program 47 ( Figure 2) which may operate without knowledge of the trailer length D or the detected hitch angle in order to ensure stability and avoid kinking. However, it is contemplated that the controller 38 may also include a standard curvature program that requires input of the trailer length D and functions by directly detecting the hitch angle, such as using an imaging device (e.g., imaging device 34). An example of a standard curvature program is described in U.S. Patent No. 8,909,426, issued December 9, 2014 to Rhode et al. and entitled “TRAILER PATH CURVATURE CONTROL FOR TRAILER BACKUP ASSIST,” the entire disclosure of which is incorporated herein by reference.

[0122] like Figure 4 and Figure 5 As shown, the TBA system 10 disclosed herein provides a knob 58 for driver input. The driver indicates the desired direction and curvature of the reverse path by turning the knob 58. Various positions or knob angles of the knobs 58a-58e are interpreted by the controller 38 as requests to cause the trailer 14 to follow a path similar to k(a)-k(e), respectively. According to one embodiment, position 58a may correspond to a rest position P(AR) of the knob 58 (the knob may be spring-biased to such a position), which corresponds to reverse along a substantially straight path k(a), and various other positions 58b, 58c are within a left range R(L) of motion of the knob 58, and other positions 58d, 58e are within a right range R(R) of motion of the knob 58.

[0123] See also Fig.13 , showing the curvature input scaling module 200 of the controller 38. The knob angle of the knob 58 can be mapped to the interval [-1, 1] by a certain (possibly nonlinear) function k. Since the knob angle is a function of time, the value of the mapping function is also a function of time. For convenience, this time-varying variable is referred to herein as a "curvature command" and is simply denoted as k(t). When the curvature program 47 is used, the knob 58 provides the curvature command k(t) to the curvature input scaling module 200 and is converted to the curvature input scaling module 200 by the maximum effective curvature. Scaling to generate curvature input in As shown in the figure, the maximum effective curvature By composite function limited.

[0124] Corresponds to the effective bend angle and is given by the following equation:

[0125]

[0126] in:

[0127] is a constant that is determined by the maximum steering angle δ 最大 Subtract configurable buffer Δ buf To limit, where Δ buf ≥0,

[0128] is the estimated trailer length,

[0129] L is the drawbar length and is assumed to be known, and

[0130] W is the vehicle wheelbase and is assumed to be known. The effective bending angle It may be less than the theoretical kink angle because, in practice, the controller 38 may generate some overshoot in the hitch angle, and it is generally desirable to maintain additional steering lock to ensure a quick transition from maximum curvature to zero curvature.

[0131] Corresponding to the maximum effective curvature and is given by the following equation:

[0132]

[0133] in:

[0134] is the effective bend angle determined by Equation 8,

[0135] is the drawbar length, and

[0136] is the estimated trailer length. With respect to the present disclosure, for simplicity, the curvature input scaling module 200 (which is composed of the composite function The continuous input-output limit) is determined by express.

[0137] refer to Fig.14 , shows a controller 38 including a curvature input scaling module 200. The curvature input scaling module 200 is in communication with an estimator 202, which is configured to generate an estimated trailer length and the estimated attachment angle This is based on the vehicle yaw rate ω 1 (t) and trailer yaw rate ω 2 (t) is generated. As described in this paper, the vehicle and trailer yaw rates ω 1 (t),ω 2 (t) can be provided to the controller 38 by the vehicle yaw rate sensor 52 and the trailer yaw rate sensor 54, respectively. The estimator 202 calculates the estimated trailer length Provided to the curvature input scaling module 200 so that the curvature input As previously referenced herein Fig.13 The estimator 202 also calculates the estimated trailer length The curvature mapping module 204 provided to the controller 38, for simplicity, the curvature mapping module 204 is composed of The curvature mapping module 204 is configured to generate a reference attachment angle This is based on the estimated trailer length received from the estimator 202 and the curvature input received from the curvature input scaling module 200 Generated. Reference mounting angle Corresponding to the curvature input The required steady state mounting angle is given by:

[0138]

[0139] in:

[0140] is the curvature input,

[0141] L is the drawbar length, and

[0142] is the estimated trailer length.

[0143] The reference mounting angle provided by the curvature mapping module 204 and the estimated hitch angle provided by the estimator 202 The signal is received by the subtractor 206, and the subtractor 206 is configured to generate a signal e(t) by reference to the mounting angle Subtract the estimated hitch angle Estimated hitch angle Given by the following equation:

[0144]

[0145] in:

[0146] ω 1 (t) is the vehicle yaw rate,

[0147] ω 2 (t) is the trailer yaw rate,

[0148] L is the length of the drawbar,

[0149] is the estimated trailer length, and

[0150] υ(t) is the vehicle speed. In real-time implementation, the Kalman filter can be used with the estimated hitch angle and its internal state measurements.

[0151] The signal e(t) is provided to a proportional-integral (PI) controller 208 to generate a control variable u(t), which is defined by the following equation:

[0152]

[0153] in:

[0154] e(t) is the signal generated by subtractor 206,

[0155] K p is a non-negative scaling factor, and

[0156] K i is an integral coefficient with a non-negative value.

[0157] The control variable u(t) together with the estimated trailer length provided by the estimator 202 and the estimated attachment angle and a speed sensor 50 ( Figure 2 ) is provided to the hitch angle controller 210 to generate a torque which is supplied to the power steering system 57 ( Figure 2 ) is a steering command in the form of a steering angle δ(t). For simplicity, the hitch angle controller 210 is composed of is represented and given by the following equation:

[0158]

[0159] in:

[0160] u(t) is the control variable generated by the PI controller 208,

[0161] is the estimated trailer length,

[0162] is the estimated hitch angle provided by the estimator 202,

[0163] W is the vehicle wheelbase,

[0164] is the estimated trailer length, and

[0165] υ(t) is the velocity sensor 50( Figure 2 ) provides the vehicle speed

[0166] When based on Fig.14The illustrated embodiment configures the controller 38 so that the trailer 14 reaches the same equilibrium under steady-state conditions (e.g., under zero, maximum, or minimum curvature command k(t)) regardless of which estimated trailer length is used. For the purpose of illustration and understanding, Fig.15 Shows a family of closed-loop equilibrium γ eq (in degrees) as a function of the curvature command k(t) (for estimating the trailer length For exemplary purposes, the balance γ eq Corresponding to the following situation, where W = 3.98m, L = 1.35m, υ(t)=5,K p =0.75. For simplicity, assume that the integral control is turned off, that is, K i = 0. Fig.15 As shown, the dashed line 212 corresponds to and the dashed line 214 corresponds to In particular, the estimated trailer length Converge to the same equilibrium γ eq , which is done under zero curvature command k(t)=0, maximum curvature command k(t)=1, and minimum curvature command k(t)=-1. Therefore, under certain conditions (e.g., steady-state conditions), the generated steering angle δ(t) is for the estimated trailer length In some embodiments, the transient response of the controller 38 to the estimated trailer length It can also be constant. This is achieved by the gain scheduling proportionality factor K p (Based on estimated trailer length only ). For example, the proportionality coefficient K p Can be done by function In this way, the closed loop dynamics are shaped in a uniform manner.

[0167] It is to be understood that changes and modifications may be made to the foregoing structures and methods without departing from the concepts of the present invention and further it is to be understood that such concepts are intended to be encompassed by the following claims unless the claims in their language expressly state otherwise.

[0168] According to the present invention, a calibration method is provided, the method having the following steps: capturing an image of a rear bumper using an imaging device; and providing a controller, the controller being configured to: process the captured image, identify a boundary separating the rear bumper from the ground, compare the identified boundary with an ideal boundary, and determine an offset between the identified boundary and the ideal boundary.

[0169] According to an embodiment, the ideal boundary comprises a continuous line.

[0170] According to an embodiment, the ideal boundary comprises a line having breaks.

[0171] According to an embodiment, the ideal boundary is overlaid on the captured image.

[0172] According to an embodiment, the offset is defined by a vector having a horizontal component, a vertical component and a rotational component.

[0173] According to an embodiment, the controller determines the offset by iterating candidate values ​​of each of the horizontal component, the vertical component, and the rotational component until the identified boundary overlaps the ideal boundary.

[0174] According to an embodiment, the controller is further configured to generate a warning when the offset cannot be determined.

[0175] According to the present invention, a trailer reverse assist system is provided, which has: a device, which is configured to sense a trailer; and a controller, which is configured to determine the coupling angle between the vehicle and the trailer based on data provided by the device, wherein if the device fails, the controller predicts the coupling angle based on the latest known coupling angle, the latest known angular velocity of the trailer and the execution cycle time.

[0176] According to an embodiment, the device comprises an imaging device and the controller is configured to predict the hitch angle in the event that the imaging device is obstructed or otherwise malfunctions.

[0177] According to an embodiment, the controller is further configured to predict the hitch angle until an error band reaches a threshold value.

[0178] According to an embodiment, the controller is further configured to determine an upper error band and a lower error band of the predicted hitch angle, and to formulate countermeasures when the upper error band reaches the maximum controllable hitch angle or the lower error band reaches the minimum controllable hitch angle, whichever occurs first.

[0179] According to an embodiment, the upper error band and the lower error band are each determined based on a predicted hitch angle, an initial degree error when the device fails, a cumulative vehicle travel distance, and a trailer length.

[0180] According to an embodiment, the countermeasure comprises at least one of: steering the vehicle to prevent exceeding the maximum controllable hitch angle or the minimum controllable hitch angle, and reducing the speed of the vehicle.

[0181] According to an embodiment, the known latest angular velocity is based on an angular velocity adjusted by a percentage error.

[0182] According to the present invention, a method for determining the hitch angle between a vehicle and a trailer is provided, the method comprising the following steps: selecting at least one hitch angle detection method from a plurality of hitch angle detection methods; determining the hitch angle between the vehicle and the trailer using the selected at least one hitch angle detection method; and switching to another hitch angle detection method when the selected at least one hitch angle detection method becomes unavailable.

[0183] According to an embodiment, the plurality of mounting angle detection methods each employs imager-based mounting angle detection.

[0184] According to an embodiment, the plurality of hitch angle detection methods are ranked based on a confidence score assigned to each hitch angle detection method, and wherein the at least one selected hitch angle detection comprises the available hitch angle detection method having the highest confidence score.

[0185] According to an embodiment, the above invention is further characterized by the step of limiting said speed of said vehicle based on said confidence score assigned to said at least one selected hitch angle detection method.

[0186] According to an embodiment, the above invention is further characterized by the following step: predicting the hitch angle during a transition between the at least one selected hitch angle detection method and another hitch angle detection method, or when each of the multiple hitch angle detection methods becomes unavailable.

[0187] According to an embodiment, the above invention is further characterized by the step of using said determined hitch angle to control at least one of a hitch angle operating range, a speed limit of said vehicle and said curvature of a reverse path of said trailer.

[0188] According to the present invention, a trailer back-up assist system is provided, which comprises: a steering input device, which is configured to provide a curvature command based on a user input; and a controller, which is configured to estimate a trailer length based on a yaw rate of the vehicle and the trailer, and to generate a steering command based on the estimated trailer length, the curvature command, a maximum steering angle and a vehicle speed, wherein the generated steering command is unchanged for the estimated trailer length under certain conditions.

[0189] According to an embodiment, the steering input device comprises a rotatable knob configured to allow a user to input a desired direction and curvature of a reverse path of the trailer being reversed by the vehicle.

[0190] According to an embodiment, the controller comprises a curvature input scaling module configured to scale the curvature command by a maximum effective curvature to generate a curvature input based on the maximum steering angle and the estimated trailer length.

[0191] According to an embodiment, the controller further comprises a curvature mapping module configured to generate a reference hitch angle based on the curvature input and the estimated trailer length.

[0192] According to an embodiment, the controller further comprises a subtractor configured to subtract an estimated hitch angle from the reference hitch angle to generate a signal, the signal being provided to a proportional-integral controller configured to generate a control variable, wherein the estimated hitch angle is based on the vehicle and trailer yaw rates.

[0193] According to an embodiment, the controller further comprises a hitch angle controller configured to generate the steering angle based on the control variable, the estimated trailer length and the vehicle speed.

[0194] According to an embodiment, the proportionality coefficient of the proportional-integral controller is based only on the estimated trailer length, so that the transient response of the controller is invariant to the estimated trailer length.

[0195] According to an embodiment, the certain conditions include one of a zero curvature command, a maximum curvature command, and a minimum curvature command.

Claims

1. A trailer reverse assist system, comprising: a device configured to sense a trailer; as well as A controller is configured to determine a hitch angle between the vehicle and the trailer based on data provided by the device, wherein if the device fails, the controller predicts the hitch angle based on a last known hitch angle, a last known angular velocity of the trailer, and an execution cycle time.

2. The trailer reverse assist system of claim 1, wherein the device comprises an imaging device, and the controller is configured to predict the hitch angle if the imaging device is obstructed or fails. 3 . The trailer backup assist system of claim 1 , wherein the controller is further configured to predict the hitch angle until an error band reaches a threshold.

4. The trailer backup assist system of claim 1 , wherein the controller is further configured to determine an upper error band and a lower error band for the predicted hitch angle and, if the upper error band reaches a maximum controllable hitch angle or the lower error band reaches a minimum controllable hitch angle, enact a countermeasure at least associated with attempting to prevent the hitch angle from exceeding the maximum controllable hitch angle or falling below the minimum controllable hitch angle, whichever occurs first.

5. The trailer backup assist system of claim 4, wherein the upper error band and the lower error band are each determined based on a predicted hitch angle, an initial degree error when the device fails, a cumulative vehicle travel distance, and a trailer length.

6. The trailer reverse assist system of claim 4, wherein the countermeasure comprises at least one of: steering the vehicle to prevent exceeding the maximum controllable hitch angle or the minimum controllable hitch angle, and reducing the speed of the vehicle.

7. The trailer back-up assist system according to any one of claims 1 to 6, wherein the known latest angular velocity is based on an angular velocity adjusted by a percentage error.

Images