Speed ​​control for motor vehicles

Abstract

Trailer reversing assistance system, which includes the following: a coupling angle sensor configured to determine a coupling angle between a vehicle and a trailer attached to it; an input device configured to accept an input instruction corresponding to a trailer path instruction curve; a controller configured to determine a vehicle threshold speed limit by determining a first vehicle speed limit based on the coupling angle and a second vehicle speed limit based on the trailer path instruction curvature, wherein the controller generates instructions to limit the vehicle speed in a reverse direction to below the vehicle threshold speed limit, characterized in that The control system is further configured to set the vehicle threshold speed limit to the lower of the first and second vehicle speed limits when the magnitude of a trailer path guidance curve increases, and to set the vehicle threshold speed limit to the higher of the first and second vehicle speed limits when the magnitude of the trailer path guidance curve decreases.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 243,475, filed October 19, 2015, entitled "SPEED OPTIMIZED TRAJECTORY CONTROL FOR MOTOR VEHICLES," the entire disclosure of which is hereby incorporated by reference. FIELD OF THE INVENTION

[0002] The present invention relates generally to systems for controlling / assisting vehicles during reversing operations, and more particularly to a system that controls vehicle speed during parking and / or trailer reversing operations. BACKGROUND OF THE INVENTION

[0003] Reversing a vehicle with a trailer can be a daunting task. In conventional vehicles, the operator must control the steering and vehicle speed while the vehicle is moving backward. Trailer backup assist systems were developed to assist operators when reversing a vehicle with a trailer attached.

[0004] Motor vehicles may also include active parking assistance systems that assist a driver during vehicle parking maneuvers. Such systems may be configured to provide automated parking. During parking maneuvers, the vehicle may be moved in a reverse direction.

[0005] The path a vehicle can follow in reverse is limited by the design of the vehicle and trailer (if present), as well as road conditions. Furthermore, the path a vehicle (and trailer) can follow in a reverse direction may be more limited at higher vehicle speeds.

[0006] DE 103 36 985 A1 relates to a method having the features of the preamble of claim 1. Another document relevant to the prior art is DE 10 2014 002 856 A1. SUMMARY OF THE INVENTION

[0007] According to the present invention, a trailer reversing assistance system according to claim 1 and a method for controlling the speed of a motor vehicle according to claim 6 are disclosed. Advantageous further developments emerge from the subclaims.

[0008] The trailer backup assist system includes a hitch angle sensor configured to determine a hitch angle between a vehicle and a trailer attached thereto. An input device is configured to accept an input command corresponding to a trailer path command curvature. A controller is configured to determine a threshold vehicle speed limit by determining a first vehicle speed limit based on the hitch angle and a second speed limit based on the command curvature. The controller generates a command to limit the vehicle speed in a reverse direction to below the threshold speed limit.

[0009] The method for controlling a speed of a motor vehicle includes determining a hitch angle between a vehicle and a trailer attached to the vehicle. Then, a trailer curvature command is determined based on an input from an input device. A first vehicle speed limit is calculated based on the hitch angle. A second speed limit is calculated based on the trailer curvature command. A threshold speed limit is then determined based on the first and second speed limits.

[0010] These and other aspects, objects and features of the present invention will become apparent and understandable to one skilled in the art upon closer examination of the following description, claims and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the drawings: Fig.1 is a perspective top view of a vehicle attached to a trailer with an embodiment of a hitch angle sensor for operating a trailer reversing assistance system; Fig. 2 is a schematic view of a motor vehicle including a trailer reversing assistance system according to an embodiment; Fig. 3 is a block diagram illustrating an embodiment of the trailer backup assist system with an input device, a curvature controller, and a vehicle braking system; Fig. Figure 4 is a partial view of a vehicle interior including an auxiliary control input that can be used by a vehicle operator when the vehicle is reversing with a trailer attached; Fig.5 is a schematic diagram illustrating the geometry of a vehicle and a trailer overlaid with a two-dimensional xy coordinate system that identifies variables used to determine a kinematic relationship between the vehicle and the trailer for the trailer backup assist system according to one embodiment; Fig. Figure 6 is a schematic plan view of a motor vehicle and a trailer at various positions along a vehicle path; Fig. 7 a graph showing a maximum permissible vehicle speed against a coupling angle; Fig. 8 is a graph showing a maximum allowable vehicle speed versus a desired input command; Fig.9 is a schematic block diagram illustrating portions of a curvature control according to an additional embodiment and other components of the trailer backup assist system according to such an embodiment; Fig. 10 a flowchart of the curvature control from Fig. 9, which shows the signal flow of the curvature control according to such an embodiment; and Fig. 11 a flowchart of the curvature control from Fig. 9, which shows the signal flow of the curvature controller according to such an embodiment, wherein the controller sets a plurality of speed limits, filters, and compares the speed limits to determine a threshold speed limit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] For the purposes of this description, the terms “upper”, “lower”, “right”, “left”, “rear”, “front”, “vertical”, “horizontal” and derivatives thereof shall refer to the invention as described in Fig.1. It is to be understood, however, that the invention is capable of various alternative orientations and sequences of steps 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. 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.

[0013] As required, detailed embodiments of the present invention are disclosed herein. It should be understood, however, that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures do not necessarily follow a detailed design, and some schematic representations may be exaggerated or minimized to show a functional overview. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to variously employ the present invention.

[0014] As used herein, the term “and / or” when used in a listing of two or more items means that any of the listed items can be used alone or that any combination of two or more of the listed items can be used. For example, if a composition is described as containing the components A, B, and / or C, the composition can 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.

[0015] With reference to Fig.1 - 11 generally refers to the reference number 10 as a trailer reverse assist system for controlling a reverse path of a trailer 12 attached to a vehicle 14 by enabling a driver of the vehicle 14 to specify a desired instruction curvature κ2 or the reverse path 16 of the trailer 12. In one embodiment, the trailer reverse assist system 10 automatically steers the vehicle 14 to guide the trailer 12 along the desired curvature κ2 when a driver uses the gas and / or brake pedal to control the reverse speed of the vehicle 14. Additionally, the trailer reverse assist system 10 may include an input device 18, such as a rotatable knob 20, for a driver to provide a desired rotation angle that is associated with a corresponding desired instruction curvature κ2 of the trailer 12.To monitor the position of the trailer 12 relative to the vehicle 14, the trailer backup assist system 10 may include a sensor system 22 that detects a hitch angle γ between the trailer 12 and the vehicle 14, which may generally be referred to as a hitch angle sensor 24. To prevent unacceptable trailer backing conditions, such as a jackknife condition, the hitch angle γ and the desired command curvature κ2 may be monitored and processed. A first vehicle speed limit may be generated based on the hitch angle γ, and a second vehicle speed limit may be generated based on the desired command curvature κ2 to assist in preventing unacceptable backing conditions. A controller 26 may filter the first and second speed limits and calculate a threshold speed limit based on the two input speed limits.The vehicle threshold speed limit may be the speed limit at which the vehicle 14 is operated to help mitigate unacceptable backing-up conditions. For example, according to one embodiment, the controller 26 may set the vehicle threshold speed limit to the minimum of the first and second speed limits during some phases of the backing-up process.

[0016] With reference to the Fig.1, the vehicle 14 is a pickup truck equipped with an embodiment of the trailer backup assist system 10 for controlling the backup path of the trailer 12 mounted on the vehicle 14. In particular, the vehicle 14 is pivotally mounted to an embodiment of the trailer 12 having a box frame 28 with an enclosed cargo area 30, a single axle 32 with a right wheel assembly 34a and a left wheel assembly 34b, and a tongue 36 extending longitudinally forward from the enclosed cargo area 30. The illustrated trailer 12 also includes a trailer hitch connector in the form of a coupling assembly 38 connected to a vehicle hitch connector in the form of a hitch ball 40.The coupling assembly 38 engages the coupling ball 40 to provide a ball-and-socket pivot connection 42 that allows for articulation of the hitch angle γ. It is understood that additional embodiments of the trailer 12 may alternatively be coupled to the vehicle 14 to provide a pivot connection, such as by connecting to a fifth-wheel coupling. It is also contemplated that additional embodiments of the trailer 12 may include more than one axle 32 and may have various shapes and sizes configured for different loads and objects, such as a boat trailer or a flatbed trailer.

[0017] With further reference to Fig.1, in the illustrated embodiment, the sensor system 22 includes both a sensor module 44 and a vision-based hitch angle sensor 24 for estimating the hitch angle γ between the vehicle 14 and the trailer 12. The illustrated hitch angle sensor 24 employs a camera 46 (e.g., a video imaging camera), which, as shown, may be located near an upper portion of the vehicle tailgate 48 at the rear of the vehicle 14 such that the camera 46 may be elevated relative to the tongue 36 of the trailer 12. The illustrated camera 46 has an imaging field of view 50 positioned and oriented to capture one or more images of the trailer 12, including an area containing one or more desired target placement zones for at least one target 52 to be secured.Although it is contemplated that the camera 46 may capture images of the trailer 12 without a target 52 to determine the hitch angle γ, the trailer backup assist system 10 in the illustrated embodiment includes a target 52 placed on the trailer 12 to enable the trailer backup assist system 10 to utilize information obtained by image capture and processing of the target 52. For example, the illustrated camera 46 may include a video imaging camera that repeatedly captures successive images of the trailer 12, which may be processed to identify the target 52 and its positioning on the trailer 12 to determine movement of the target 52 and the trailer 12 relative to the vehicle 14 and the corresponding hitch angle γ.It should also be noted that the camera 46 may include one or more video imaging cameras and may be positioned at other locations on the vehicle 14 to obtain images of the trailer 12 and the desired target placement zone, such as at a passenger compartment of the vehicle 14 for capturing images of a gooseneck trailer.It is further contemplated that additional embodiments of the hitch angle sensor 24 and the sensor system 22 for providing the hitch angle γ may include one or more of the following, or a combination thereof: a potentiometer, a magnetic-based sensor, an optical sensor, a proximity sensor, a rotary sensor, a capacitive sensor, an inductive sensor, and a mechanically based sensor, such as a mechanical sensor assembly mounted on the ball joint pivot connection 42, energy converters of a reverse assist system, a blind spot system, and / or a cross traffic alert system, and other conceivable sensors or indicators of the hitch angle γ in addition to, or instead of, the vision-based hitch angle sensor 24.

[0018] The design of the Fig.The sensor module 44 illustrated in Figure 1 includes a sensor cluster 54 within a housing mounted on the tongue 36 of the trailer 12 proximate the enclosed cargo area 30 and includes left and right wheel speed sensors 56 on laterally opposite wheels of the trailer 12. It is contemplated that the wheel speed sensors 56 may be bidirectional wheel speed sensors 56 for monitoring both forward and reverse speeds. Furthermore, it is contemplated that the sensor cluster 54 may be mounted on alternative portions of the trailer 12 and / or the vehicle 14 in additional embodiments.

[0019] The sensor module 44 generates a plurality of signals indicative of various dynamic characteristics of the trailer 12. The signals may include a yaw rate signal, a lateral acceleration signal, and wheel speed signals, each of which is sensed by a yaw rate sensor 58 ( Fig.3), an accelerometer 60 ( Fig. 3) and the wheel speed sensors 56. Accordingly, the yaw rate sensor 58 and the accelerometer 60 are included in the housingd sensor cluster 54 in the illustrated embodiment, although other configurations are conceivable. It is conceivable that in some embodiments, the accelerometer 60 may be two or more separate sensors that may be arranged at an offset angle, such as two sensors arranged at plus and minus forty-five degrees from the longitudinal direction of the trailer 12 or parallel to the longitudinal and lateral directions of the trailer 12, to produce a more robust acceleration signal. It is also contemplated that these sensor signals could be compensated and filtered to eliminate offsets or drifts and smooth out disturbances. Further, the controller 26 ( Fig.3) processed signals received outside the sensor system 22, including standard signals from the brake control system 62 ( Fig. 3) and the power steering system 64 ( Fig. 3), such as vehicle yaw rate ω1, vehicle speed v1, and steering angle δ, to estimate the trailer hitch angle γ, the trailer speed, and associated trailer parameters. As described in more detail below, the controller 26 may estimate the hitch angle γ based on the trailer yaw rate ω2, the vehicle yaw rate ω1, and the vehicle speed v1 with respect to a kinematic relationship between the trailer 12 and the vehicle 14. The controller 26 of the trailer backup assist system 10 may further use the estimated trailer variables and trailer parameters to control the steering system 64, the braking control system 62, and the powertrain control system 66 ( Fig.3) to assist in reversing the combination of vehicle 14 and trailer 12 or to mitigate an unacceptable reversing condition.

[0020] With reference to Fig. 2, according to one embodiment, the trailer backup assist system 10 includes the trailer backup input device 18 operably connected to a trailer backup assist controller 26. The trailer backup assist system 10 further includes the hitch angle sensor 24 operably connected to the trailer backup assist controller 26.

[0021] The trailer backup assist control 26 is operatively connected to a brake control system 62 and a power control system 66.

[0022] The vehicle 14 also includes a power steering system 64 including a power steering control module 68 and a steering angle sensor 70. The power steering control module 68 is operatively connected to the trailer backup assist controller 26. The trailer 12 may include a hitch angle sensor 24 operatively connected to the hitch angle sensor 24 of the vehicle 14.

[0023] The hitch angle sensor 24 is configured to measure the angle of the trailer 12 relative to the vehicle 14 against a vertical axis. A hitch angle γ of zero generally corresponds to an operating condition in which the trailer 12 is aligned with the vehicle 14 such that the vehicle 14 and the trailer 12 are moving along a straight path. The hitch angle sensor 24 may also be configured to measure an orientation of the trailer 12 relative to the vehicle 14 against a horizontal axis extending from side to side and against a second horizontal axis extending in a front-to-rear direction of the vehicle 14. This allows the trailer backup assist system 10 to determine whether the trailer 12 has begun to travel on a downgrade and / or whether the trailer 12 has twisted relative to the vehicle 14 due to movement on a surface that slopes sideways.It is understood that various hitch angle detection / measurement devices may be used and the components may be mounted to the vehicle 14, the trailer 12, or both.

[0024] With reference to the Fig.In the embodiment of the trailer backup assist system 10 shown in Figure 3, the hitch angle sensor 24 provides the detected hitch angle γ to the trailer backup assist system 10. Similarly, the illustrated embodiment of the trailer backup assist system 10 receives information related to the vehicle condition from other sensors and devices. This information includes positioning information from a positioning device 74, which may include a global positioning system (GPS) on the vehicle 14 or a handheld device, to determine a coordinate position of the vehicle 14 and the trailer 12 based on the position of the positioning device 74 relative to the trailer 12 and / or the vehicle 14 and based on the detected hitch angle γ.The positioning device 74 may additionally or alternatively include a dead reckoning system for determining the coordinate position of the vehicle 14 and the trailer 12 within a localized coordinate system based on at least the vehicle speed, the steering angle, and the hitch angle γ. Other vehicle information received by the trailer backup assist system 10 may include a speed of the vehicle 14 from speed sensors 78 and a yaw rate of the vehicle 14 from a yaw angle sensor 80.It is contemplated that in additional embodiments, the hitch angle sensor 24 and other vehicle sensors 76 and devices may provide sensor signals or other information, such as proximity sensor signals or sequential images of the trailer 12, which a controller 26 of the trailer backup assist system 10 may process with various routines to determine a value or indicator, such as a hitch angle value γ or a range of hitch angles.

[0025] As further stated in Fig. 3, an embodiment of the trailer backup assist system 10 is in communication with a power steering system 64 of the vehicle 14 to control steered wheels 82 ( Fig.1) of the vehicle 14 to move the vehicle 14 such that the trailer 12 responds in accordance with the desired command curvature κ2 of the trailer 12. In the illustrated embodiment, the power steering system 64 is an Electric Power-Assisted Steering (EPAS) system that includes an electric steering motor 84 for turning the steered wheels 82 to a steering angle based on a steering command, wherein the steering angle is sensed by a steering angle sensor 70 of the power steering system 64. The steering command may be provided by the trailer backup assist system 10 for autonomous steering during a reversing maneuver, and may alternatively be provided manually by means of a rotational position (e.g., steering wheel angle) of a steering wheel 86 ( Fig.1). However, in the illustrated embodiment, the steering wheel 86 of the vehicle 14 is mechanically coupled to the steered wheels 82 of the vehicle 14 such that the steering wheel 86 moves in concert with the steered wheels 82, thereby preventing manual intervention via the steering wheel 86 during autonomous steering. More specifically, a torque sensor 88 is provided on the power steering system 64 that detects torque at the steering wheel 86 that is not expected by the autonomous control of the steering wheel 86 and thus indicates manual intervention, whereby the trailer backup assist system 10 can alert the driver to discontinue manual intervention via the steering wheel 86 and / or autonomous steering.

[0026] In alternative embodiments, some vehicles 14 include a power steering system 64 that allows a steering wheel 86 to be partially decoupled from the movement of the steered wheels 82 of such vehicle 14. Accordingly, the steering wheel 86 can be rotated independently of the manner in which the vehicle's power steering system 64 controls the steered wheels 82 (e.g., autonomous steering as commanded by the trailer backup assist system 10). Therefore, in those types of vehicles 14 where the steering wheel 86 can be selectively decoupled from the steered wheels 82 to enable their independent operation, the steering wheel 86 can be used as an input device 18 for the trailer backup assist system 10, as disclosed in more detail herein.

[0027] With further reference to the Fig.In the embodiment illustrated in FIG. 3, the power steering system 64 provides information related to a rotational position of steered wheels 82 of the vehicle 14, including a steering angle, to the controller 26 of the trailer backup assist system 10. In the illustrated embodiment, the controllers 26 process the current steering angle, in addition to other conditions related to the vehicle 14 and the trailer 12, to guide the trailer 12 along the desired command curvature κ2. It is contemplated that the trailer backup assist system 10 may be an integrated component of the power steering system 64 in additional embodiments.For example, the power steering system 64 may include a trailer backup assist algorithm for generating vehicle steering information and instructions as a function of all or a portion of the information received from the input device 18, the hitch angle sensor 24, the power steering system 64, a vehicle brake control system 62, a powertrain control system 66, and other vehicle sensors 76 and devices.

[0028] As in Fig.3, the vehicle brake control system 62 may also communicate with the controller 26 to provide braking information, such as wheel speed, to the trailer backup assist system 10 and receive braking commands from the controller 26. For example, vehicle speed information may be determined from individual wheel speeds monitored by the brake control system 62. Vehicle speed may also be determined by the powertrain control system 66, the speed sensors 78, and the positioning device 74, among other conceivable means. In some embodiments, individual wheel speeds may also be used to determine a vehicle yaw rate, which may be provided to the trailer backup assist system 10 alternatively or in addition to the yaw sensor 80 for use in determining vehicle steering commands.In certain embodiments, the trailer backup assist system 10 may provide vehicle braking information to the brake control system 62 to enable the trailer backup assist system 10 to control the braking of the vehicle 14 during the reversing of the trailer 12. For example, in some embodiments, the trailer backup assist system 10 may regulate the speed of the vehicle 14 during the reversing of the trailer 12, which may reduce the possibility of unacceptable trailer reversing conditions occurring. Examples of unacceptable trailer reversing conditions include, but are not limited to, an overspeed condition of the vehicle 14, a high hitch angle rate (i.e.,the change in the hitch angle over time), a dynamic instability of the trailer angle γ, a calculated theoretical trailer jackknife condition (defined by a maximum vehicle steering angle, a tongue length, a wheelbase of the tow vehicle, and an effective trailer length), or a jackknife limitation by physical contact (defined by an angular displacement limit relative to the vehicle 14 and the trailer 12), and the like. The trailer backup assist system 10 may also output a warning signal corresponding to notification of a current, impending, and / or expected unacceptable trailer backup condition, as disclosed in more detail herein.

[0029] That as in the in Fig.The powertrain control system 66 shown in the embodiment illustrated in Figure 3 may also cooperate with the trailer backup assist system 10 to regulate the speed and acceleration of the vehicle 14 during the reversing of the trailer 12. As mentioned above, regulation of the speed of the vehicle 14 may be necessary to limit the possibility of unacceptable trailer backing conditions, such as jackknifing and dynamic instability of the hitch angle γ, occurring. Similar to considerations of the relationship between high speed and unacceptable trailer backing conditions, high acceleration and highly dynamic driver-desired curvature commands κ2 may also result in such unacceptable trailer backing conditions.

[0030] With further reference to Fig.3, the trailer backup assist system 10 in the illustrated embodiment may communicate with one or more devices, including vehicle warning devices 90, which may be used to alert the driver of the vehicle in a variety of ways. For example, the vehicle warning devices 90 may use the generated warning signal to trigger visual, audible, and tactile warnings. As such, the vehicle warning devices 90 may include lights 92, such as exterior brake lights and vehicle hazard warning lights, as well as interior instrument cluster lights and mirror lights. Additionally, for audible warnings, the vehicle warning devices 90 may include a vehicle horn 94 and / or a speaker 96 within the vehicle 14.Furthermore, the trailer backup assist system 10 may communicate warnings and other information to a human machine interface (HMI) 98 for the vehicle 14, including a vehicle display 100 such as a center console-mounted navigation / entertainment display (. Fig.1). Regarding a tactile or haptic warning, the vehicle warning devices 90 may include a variety of equipment, such as the input device 18, a driver seat, and / or other vehicle devices. Furthermore, the trailer backup assist system 10 may communicate via wireless communication with another embodiment of the HMI 98, such as one or more handheld or wearable devices, including one or more smartphones. The wearable device may further include the display 100 for displaying one or more images and other information to a user. For example, the wearable device may display one or more images of the trailer 12 and the target position within a desired target placement zone on the display. Furthermore, the wearable device may provide feedback information, such as audible and tactile warnings.

[0031] As further stated in Fig.3, the trailer backup assist system 10 includes an input device 18 connected to the controller 26 to enable information communication therebetween. It is disclosed herein that the input device 18 may be coupled to the controller 26 in a wired or wireless manner. The input device 18 provides information to the trailer backup assist system 10 defining the desired backup path 16 of the trailer 12 for the controller 26 to process and generate steering commands. Namely, the input device 18 accepts an input command based on a desired trailer curvature input through the input device 18 and, in response, provides a desired curvature κ2 of the trailer travel 12.Additionally, the trailer steering instructions may include information related to a commanded change in the travel path, such as a change in the radius of the return path 16 (e.g., the curvature), and information related to an indication that the trailer 12 should travel along a path defined by a longitudinal centerline axis of the trailer 12 (i.e., along a substantially straight travel path or zero curvature). As discussed in more detail below, the input device 18 according to the illustrated embodiment may include the input device 18 for selecting the longitudinal direction of the trailer 12, the longitudinal direction of the vehicle 14, or the curvature based on the present hitch angle γ.

[0032] The input device 18 in the illustrated embodiment may additionally or alternatively include a rotary control input device to enable a driver of the vehicle 14 to command desired trailer steering actions or otherwise select the desired input command and / or the desired curvature κ2. For example, the rotary control input device may be a rotary knob 20 that is rotatable about a rotational axis extending through a top surface or face of the knob 20. In other embodiments, the rotary knob 20 may be rotatable about a rotational axis extending substantially parallel to a top surface or face of the rotary knob 20.Furthermore, according to further embodiments, the input device 18 may include alternative devices for providing a desired input instruction or other information defining a desired return path 16, such as a joystick, depressible buttons, slide input devices, various controls on a handheld device, various user interfaces on a touchscreen display, vision-based systems for receiving gestures, a path planner or other programmable route system, and other conceivable input devices as generally understood by one of ordinary skill in the art.

[0033] Further referring to the Fig.In the embodiment shown in Figure 3, the controller 26 is configured with a microprocessor 102 to process logic and routines stored in memory 104 that receive information from the input device 18, the hitch angle sensor 24, the power steering system 64, the vehicle brake control system 62, the powertrain control system 66, and other vehicle sensors 76 and devices. As noted above, the controller 26 may process the hitch angle and related information from the hitch angle sensor 24 or other input to generate a warning signal with sufficient time for the driver to respond to an unacceptable trailer backing condition.Examples of unacceptable trailer backing conditions include, but are not limited to, a high-speed condition, a high hitch angle rate, dynamic instability of the hitch angle γ, a calculated theoretical trailer jackknife condition, jackknife restraint by physical contact, an approach of the trailer 12 or the vehicle 14 to physical contact with an object, and the like. It is disclosed herein that the trailer backup assist system 10 may output an alarm signal corresponding to a notification of a current, impending, and / or expected unacceptable trailer backing condition.

[0034] The controller 26 may additionally or alternatively generate vehicle steering information and commands as a function of all or a portion of the information received from the input device 18, the hitch angle sensor 24, the power steering system 64, the vehicle brake control system 62, the trailer brake system, the powertrain control system 66, and other vehicle sensors 76 and devices. The vehicle steering information and commands may then be provided to the power steering system 64 to influence the steering of the vehicle 14 to achieve a commanded travel path for the trailer 12. The controller 26 may include the microprocessor 102 and / or other analog and / or digital circuitry for processing one or more routines.Furthermore, the controller 26 may include the memory 104 for storing one or more routines, including a curvature routine 106, an operation routine 108, and a hitch angle estimation routine 110. It is understood that the controller 26 may be a standalone, dedicated controller or a common controller integrated with other control functions, such as the sensor system 22, the power steering system 64, and other conceivable onboard or off-board vehicle control systems.

[0035] With reference to Fig.4, an input device 18, such as a rotatable knob 20, may be mounted to a vehicle interior component, such as a center console 112. Upon activation of the trailer backup assist system 10, a user may rotate the knob 20 to provide a user steering request, or input command, to the power steering system 64. During vehicle backup operations, a user may use the knob 20 to provide steering input instead of turning the vehicle steering wheel. More specifically, the angular position of the rotatable knob 20 may be related to a desired command curvature κ2, such that rotation of the knob 20 to a different angular position provides a different desired curvature κ2 with an incremental change based on the amount of rotation.As described in more detail below, the trailer backup assist system 10 may be configured to generate steering command signals to change the wheel angle of the steered wheels. The steering command signals may be directly proportional to the user's steering request, or the system may override or modify the steering request to generate steering command signals. The rotatable knob 20 may be biased (e.g., by a spring return) to a center or rest position P(AR) between opposite rotational ranges of movement R(R), R(L).

[0036] With further reference to Fig.4, a first opposite range of motion rotation R(R) is substantially equal to a second opposite range of motion rotation R(L). To provide a tactile indication of an amount of rotation of the rotatable knob 20, a force biasing the knob 20 toward the rest position P(AR) may increase (e.g., non-linearly) as a function of the amount of rotation of the rotatable knob 20 with respect to the rest position P(AR). Additionally, the rotatable knob 20 may be configured with position-indicating detents so that the driver can clearly feel the rest position P(AR) and the approach of the ends of the opposite ranges of motion rotation R(L), R(R) (e.g., soft end stops). The input device knob 20 and its operation are described in detail in co-pending U.S. patent application Ser. No. US 2017 / 0 029 024 A1, filed on June 30, 2017.July 2015, entitled “MULTI-MODE TRAILER BACKUP ASSIST INTERFACE KNOB,” the entire disclosure of which is hereby incorporated by reference.

[0037] With reference to Fig.5, a kinematic relationship between a curvature of a travel path of the trailer 12 and the steering angle of the vehicle 14 pulling the trailer 12 may be determined for a trailer backup assist system 10 configured in accordance with some embodiments, including for use by a curvature routine 106 of the controller 26 in one embodiment. To achieve such a kinematic relationship, certain assumptions may be made regarding parameters associated with the vehicle 14 and trailer 12 system. Examples of such assumptions include, but are not limited to, the trailer 12 being backed up by the vehicle 14 at a relatively low speed, the wheels of the vehicle 14 and trailer 12 having negligible (e.g., no) slippage, the tires of the vehicle 14 having negligible (e.g.,no) lateral compliance, the tires of the vehicle 14 and the trailer 12 have negligible (e.g., no) deformation, the actuator dynamics of the vehicle 14 are negligible, and the vehicle 14 and the trailer 12 exhibit negligible (e.g., no) roll or pitch movements, among other conceivable factors that have a potential effect on the steering of the trailer 12 with the vehicle 14.

[0038] As in Fig. As shown in Figure 5, the kinematic relationship for a trailer backup assist system 10, defined by a vehicle 14 and a trailer 12, is based on various parameters associated with the vehicle 14 and the trailer 12. These parameters include: δ steering angle at the steered front wheels of the vehicle; α yaw angle of the vehicle; β yaw angle of the trailer; γ coupling angle (γ = β - α); W Wheelbase of the vehicle; L Length between the coupling point and the rear axle of the vehicle; D Distance between the coupling point and the axle of the trailer or the effective axle in the case of a multi-axle trailer (axle length may be an equivalent); and r2 radius of curvature for the trailer.

[0039] One embodiment of a kinematic relationship between the radius of curvature r2 of the trailer path at the center of an axle of the trailer 12, the steering angle δ of the steered wheels 82 of the vehicle 14, and the hitch angle γ can be expressed in the equation provided below. Thus, given the hitch angle, the curvature κ2 of the trailer path can be controlled based on regulating the steering angle δ (where β̇ is the trailer yaw rate and η̇ is the trailer speed). κ2=1r2=β˙η˙=(W+KV2g)sinγ+L cosγtanδD((W+KV2g)cosγ−L sinγtanδ)

[0040] This relationship can be formulated to provide the steering angle δ as a function of the curvature κ2 of the trailer path and the coupling angle γ. δ=tan−1((W+KV2g)[κ2D cosγ−sinγ]DLκ2sinγ+Lcosγ)=F(γ,κ2,K)

[0041] Accordingly, for a particular combination of vehicle 14 and trailer 12, certain parameters (e.g., D, W, and L) of the kinematic relationship are constant and assumed to be known. V is the vehicle's longitudinal velocity, and g is the acceleration due to gravity. K is a speed-dependent parameter that, when set to zero, makes the calculation of the steering angle independent of vehicle speed. For example, vehicle-specific parameters of the kinematic relationship may be predefined in an electronic control system of the vehicle 14, and trailer-specific parameters of the kinematic relationship may be entered by a driver of the vehicle 14, determined from sensed trailer behavior in response to vehicle steering commands, or otherwise determined from signals provided by the trailer 12.The curvature κ2 of the trailer path is determined from the driver input via the input device 18. By using the equation to provide the steering angle, the curvature routine 106 can generate an appropriate steering command to control the power steering system 64 of the vehicle 14. Furthermore, the controller 26 can predict an unacceptable backing condition based on the driver's manipulation of the input device 18. Accordingly, the trailer backup assist system 10 can set a speed limit of a desired command curvature κ2 based on the rotation of the input device 18 to assist in preventing unacceptable backing conditions.

[0042] Further with reference to Fig.5, the memory of the controller 26 may include look-up tables (LUTs) that contain a relationship between a desired command curvature κ2 and the time to reach the desired command curvature κ2. Accordingly, the controller 26 may predict an unacceptable backing-up condition, such as a jackknife condition, before the trailer 12 reaches the specific situation. Accordingly, when varying the input size of the user input device 18, the controller 26 may set a maximum speed limit of a desired command curvature based on a value within a LUT so that the jackknife condition may be prevented. Reducing the maximum vehicle speed based on the desired command curvature κ2 may also reduce noise during use of the trailer backup assist system 10.

[0043] In an additional embodiment, the curvature routine 106 may make an assumption that a longitudinal distance L between the pivot connection and the rear axle of the vehicle 14 is zero in order to operate the trailer backup assist system 10 when connecting a gooseneck trailer or other similar trailer with a hitch ball or with a fifth wheel positioned over a rear axle of the vehicle 14. The assumption essentially assumes that the pivot connection to the trailer is substantially vertically aligned with the rear axle of the vehicle 14. When such an assumption is made, the controller 26 may generate the steering angle command for the vehicle 14 as a function that is independent of the longitudinal distance L between the pivot connection and the rear axle of the vehicle 14.It should be understood that the reference to a gooseneck trailer generally refers to the configuration of the tongue 36 being elevated for attachment to the vehicle 14 at an elevated location above the rear axle, such as in a truck bed, and embodiments of the gooseneck trailer may include flatbeds, enclosed beds, caravans, livestock trailers, horse trailers, low loader trailers, and other conceivable trailers having such a tongue configuration.

[0044] With reference to Fig.6, the vehicle 14 and the trailer 12 move along a path 122, which may include a portion 122a with a smaller radius and a portion 122b that is substantially straight or has a large radius. The coupling angle γ is zero when the path 122 is straight and increases as the radius of the path portion 122a decreases. Accordingly, the coupling angle γ between the vehicle 14 and the trailer 12 will be greater in the path portions 122a than in the relatively straight path portions 122b. The trailer backup assist system 10 may be configured to limit the speed of the vehicle 14 and the trailer 12 to a maximum speed during reversing. For example, when the operator triggers the trailer backup assist system 10 and presses the input device button 20 ( Fig.4), the trailer backup assist system 10 may limit the speed of the vehicle 14 to 7 kilometers per hour (km / h), even if the hitch angle γ is zero degrees and the vehicle 14 and trailer 12 are moving along a straight portion 122b of the path 122. However, according to one embodiment, if the vehicle 14 and trailer 12 follow a portion 122a of the path 122 with a relatively small radius of curvature, thereby creating a larger hitch angle γ, the speed of the vehicle 14 may be limited by the trailer backup assist system 10 to a speed less than 7 km / h to ensure control is maintained and jackknifing is prevented.

[0045] The trailer backup assist system 10 may be configured to establish a vehicle reverse threshold speed limit when a trailer 12 is attached to the vehicle 14 to ensure that the vehicle 14 can be controlled and prevent jackknifing or other unacceptable reversing conditions. Fig. Figure 7 illustrates different ways of mapping the maximum permissible vehicle speed as a function of the coupling angle γ. Fig. Figure 8 illustrates various ways of mapping the maximum allowable vehicle speed as a function of the desired command curvature κ2. As described therein, both speed limits may be monitored in conjunction with each other by controller 26 to determine a threshold vehicle speed limit.

[0046] In use, the coupling angle γ may be measured while the vehicle 14 is reversing, and the trailer backup assist system 10 limits the vehicle speed, for example, using the vehicle brakes or propulsion, so that the vehicle 14 does not exceed the maximum allowable speed even if a vehicle operator attempts to reverse at a higher speed by depressing the accelerator pedal.

[0047] With reference to Fig.7, line 124 represents a maximum permissible vehicle speed at different hitch angles γ. In the illustrated example, line 124 is a straight line and the maximum vehicle speed at a hitch angle γ of 0° is 10 km / h, and at a hitch angle of 70°, the maximum permissible vehicle speed is reduced to 3 km / h. It should be understood that at a lower hitch angle γ (e.g., 60°), the maximum vehicle speed may be reduced to 3 km / h, as shown by line 126. Furthermore, it should be understood that in some embodiments, the vehicle may be decelerated to a speed below 3 km / h. For example, the vehicle may stop when the hitch angle γ approaches too large an angle to prevent a jackknife condition.

[0048] As shown by line 128, the maximum vehicle speed cannot be limited to a speed below 7 km / h until a coupling angle γ that is significantly greater than 0° (e.g., 30°) is reached, and then the maximum vehicle speed can be limited by a straight line that becomes 0 at a predefined coupling angle γ (e.g., 60°). Fig. In Figure 7, line 128 includes a section 128a that is horizontal until the coupling angle γ reaches 30°, and then the maximum permissible vehicle speed approaches 3 km / h linearly, as shown by line section 128b. The maximum permissible vehicle speed as a function of the coupling angle γ may also be nonlinear (e.g., parabolic), as shown by the dashed lines 130 and 132.

[0049] The maximum permissible vehicle speed for a given hitch angle γ can be determined empirically to provide several pairs of data points, and the data can be interpolated using a fitting curve to produce a line representing the maximum permissible vehicle speed as a function of the hitch angle γ, which can be stored in a LUT. Alternatively, the maximum permissible vehicle speed can be determined as a function of the hitch angle γ using a straight (linear) line of the form y = mx + b or a curved (non-linear) line of the form y = mx 2 + cx + b or another suitable equation.

[0050] The trailer backup assist system 10 may also consider other variables to determine the maximum permissible vehicle speed based on the hitch angle γ for a given operating condition. For example, the Fig. 7 (e.g., 124, 128) may be modified to take hill angles into account. Specifically, the maximum allowable vehicle speed for a given (measured) hitch angle γ may be reduced if the vehicle 14 and trailer 12 are reversing on a hill. The hill angle may be measured using a gravity sensor located in the vehicle 14, or it may be measured using a sensor in the hitch assembly 38 ( Fig.1) connecting the vehicle 14 and the trailer 12. Additional variables, such as road conditions, may also be used to adjust the maximum allowable vehicle speed for a given hitch angle γ. For example, the vehicle 14 may include sensors that enable the trailer backup assist system 10 to determine whether the vehicle 14 is on loose gravel, wet pavement, or another surface with reduced traction. If the vehicle 14 and / or the trailer 12 are on gravel or a wet surface, the maximum allowable vehicle speed for a given hitch angle γ may be further reduced to ensure the operator can maintain control of the trailer 12 during reversing operations.

[0051] Additionally, the angle on a hill may be determined using topographical information that may be stored by the trailer backup assist system 10 or obtained using a GPS system. Vehicle 14 may include an electronic compass or other positioning device 74, wherein the position and orientation of the vehicle 14 on a topographical map may be determined so that the angle of the vehicle 14 and trailer 12 on a hill may be determined.

[0052] Additionally, road condition data can be obtained from a remote source, and the maximum allowable vehicle speed can be adjusted if necessary. For example, if weather data in the vicinity of vehicle 14 indicates that it is raining or snowing, the maximum allowable vehicle speed for a given (measured) hitch angle γ can be reduced to account for the reduction in road grip. Similarly, map data concerning the road surface (e.g., gravel or asphalt road) can be used to adjust the maximum allowable vehicle speed as a function of the hitch angle γ.

[0053] With reference to Fig.8, line 134 represents a maximum allowable vehicle speed for various sizes of the input device 18. In the illustrated example, line 134 is a straight line, and the maximum vehicle speed at a hitch angle γ of 0° is 7 km / h, and at a hitch angle γ of 70°, or any other desired speed and / or stopping condition as described above, the maximum allowable vehicle speed is reduced to 3 km / h. Furthermore, as described above and shown by line 140a, the maximum vehicle speed may not be significantly limited to a speed below 7 km / h until an input size significantly greater than 0° (e.g., 60°) is reached, and the maximum allowable vehicle speed then slopes parabolically toward 0, as shown by line segment 140b.The maximum permissible vehicle speed as a function of the input size of the input device 18 may also be linear in other embodiments.

[0054] The maximum allowable vehicle speed for a given input may be determined empirically to provide multiple pairs of data points, and the data may be interpolated using a fit curve to generate a line representing the maximum allowable vehicle speed as a function of the input. Alternatively, the maximum allowable vehicle speed may be modeled as a function of the input of the input device 18 using a straight line, a curved line, or another suitable equation, as described above.

[0055] In operation, a user activates the trailer backup assist system 10 and begins backing up the vehicle 14 and trailer 12. The user uses the input device 18 to provide the desired command curvature κ2 to the trailer backup assist system 10. The trailer backup assist system 10 uses the vehicle speed and hitch angle γ data to determine a maximum allowable vehicle threshold speed, taking into account road conditions and the like, as discussed above.

[0056] In general, the trailer backup assist system 10 may ensure that the vehicle 14 and trailer 12 do not exceed the maximum threshold trailer angle by limiting the speed of the vehicle 14, the vehicle curvature, or both. Limiting the vehicle speed may be achieved by sending a command to the brake control system 62 and / or the powertrain control module 14. The brake control system 62 may be used to apply the brakes of the vehicle 14 and / or the brakes of the trailer 12 if the trailer 12 is equipped with brakes. Additionally, the powertrain control module 14 may be used to limit the amount of torque produced by the vehicle engine and / or to utilize engine braking by downshifting the engine transmission if the vehicle 14 has an internal combustion engine.If the vehicle 14 includes an electric motor 84, the powertrain system control module may use the electric motor 84 to provide braking. The trailer backup assist system 10 may also be configured to increase the vehicle speed if the vehicle speed and the hitch angle γ are within the allowable limits.

[0057] The trailer reversing assistance system 10 may also be configured to control the angle of the steered wheels to ensure that the vehicle speed is maintained against the coupling angle γ ( Fig. 7) does not exceed the permissible limits. In this case, the trailer reversing assistance system 10 will limit the angle of the steered wheels to a level lower than the value set by the user using the button 20 ( Fig.4) Input command request to prevent the hitch angle γ from exceeding the allowable limits for a given vehicle speed. Accordingly, the trailer backup assist system 10 may "override" a user steering request and generate a steering command curvature κ2 that includes a reduced steering angle relative to the user's steering request. For example, if the vehicle 14 is reversing at 7 km / h and an operator quickly turns the knob 20, the trailer backup assist system 10 may apply the brakes to slow the vehicle 14. However, the capability of the trailer backup assist system 10 may not allow the speed of the vehicle 14 to be reduced quickly enough to allow the vehicle 14 to follow the user's steering input.In this case, the trailer backup assist system 10 may generate a reduced steering command to the power steering system 64 to avoid unacceptable operating conditions (e.g., a turn too tight for the vehicle speed). Furthermore, the hitch angle γ is still limited due to the physical constraints of the connection point between the vehicle 14 and the trailer 12, even when the vehicle 14 is traveling at a very low speed (e.g., 1 km / h). Accordingly, the trailer backup assist system 10 may be configured to modify the user's steering requests and limit the commands to the power steering system 64 to a maximum value, which may be less than an input request from a user using the knob 20.

[0058] Alternatively, the trailer backup assist system 10 may be configured to reduce the maximum threshold speed of the vehicle 14 if it is calculated that the input will cause unacceptable backing conditions without a reduction in speed. The unacceptable backing condition may occur imminently, or alternatively, the controller 26 may be configured to anticipate the onset of an unacceptable backing condition that would arise if no modification of the maximum threshold speed is made.

[0059] Furthermore, the trailer backup assist system 10 may be configured to prioritize the user-requested steering input from the button 20 over the vehicle speed when determining whether to limit the vehicle speed or the turning angle to the maximum allowable values ​​as in Fig.8-9. In general, the input provided by a user to button 20 corresponds to a desired trailer path (e.g., trailer path 122 in Fig. 6) and the trailer backup assistance system 10 may be configured to assume that the desired path is more important than the desired speed. Accordingly, the trailer backup assistance system 10 may be configured to first adjust the vehicle speed to remain within the Fig. 8-9, followed (in terms of priority), if necessary, by restricting the trailer curvature to remain within the Fig. 8-9 shown permissible limits.

[0060] In addition, the actual steering angle may be delayed relative to the steering angle request, and the final (static) steering angle may be slightly less than the steering request. The trailer backup assist system 10 may be configured to optimize the vehicle's reverse speed to match the desired path 122 ( Fig.6) within an acceptable error. This allows the trailer backup assist system 10 to maintain the steering speed within an optimal range to help maintain the vehicle 14 on the desired path 122 with an acceptable amount of error. In general, the required speed of the power steering system 64 is a function of the vehicle speed and the lateral movement required to follow the desired path 122. For example, the steering speeds required to follow a given lateral change in path increase with vehicle speed. Likewise, the steering speeds required at a given vehicle speed increase with increasing change in lateral movement.

[0061] In general, vehicle speed and steering may be controlled in any combination to optimize the vehicle path. For example, the powertrain system control module 66 ( Fig.2) be configured to control the torque output. The torque output can be monitored and modified to help maintain the optimal speed to assist the power steering system 64's ability to position the vehicle 14 in a desired path. The driveline torque output can be limited to reduce the speed of the vehicle 14 when necessary for the power steering system 64 to keep the vehicle path error within a desired range. Likewise, the generated braking torque can also be monitored and modified to help maintain the optimal speed to assist the power steering system 64's ability to position the vehicle in a desired path.

[0062] The brake control system 62 can be triggered to reduce the speed of the vehicle 14 when required by the power steering system 64 to maintain the path error within a desired range. Furthermore, the automatic gear selection of the vehicle 14 can be controlled, and the vehicle 14 can downshift to promote engine braking and reduce the risk of overheating of the braking system. Furthermore, if the vehicle 14 is reversing with a trailer 12 attached, and if the trailer 12 has trailer brakes, the trailer braking torque can be monitored and modified to help maintain the optimal speed to assist the power steering system 64's ability to position the vehicle 14 on a desired path.Trailer braking torque may be applied to help reduce the speed of the vehicle 14 when required by the power steering system 64 to maintain the path error within a desired range.

[0063] With reference to Fig.9 illustrates the curvature routine 106 of the trailer backup assist system 10, showing an architectural layout according to one embodiment. The trailer backup assist system 10 includes a plurality of inputs that communicate with a speed limit controller 156 such that routines of the speed limit controller 156 stored in memory 104 can operate based on the plurality of inputs. The plurality of inputs may include storage devices separate from or integrated with the trailer backup assist system controller 26 within the vehicle 14 that store data from sensors of the trailer backup assist system 10, such as the hitch angle sensor 24, the vehicle speed sensor 78, the steering angle sensor 70, or alternatively, the plurality of inputs may otherwise transmit data directly from the sensors without acting as a storage device.Additionally, it is understood that each of the plurality of inputs disposed within the vehicle 14 may be an independent system disposed within the vehicle 14 or may be integrally disposed within any system within the vehicle 14.

[0064] As in Fig.9, an input device 18 may be configured to accept an input command corresponding to the desired command curvature κ2. In some embodiments, the input device 18 may be in a separate system located within the vehicle 14 or the trailer 12, such as a trailer coupling lighting module. In the illustrated layout, the input device 18 provides the desired command curvature κ2 to the speed limit controller 156, which may be determined based on the desired return path 16 input with the input device 18. The speed limit controller 156 calculates a desired threshold speed based on the desired command curvature κ2 and the current hitch angle γ.

[0065] As further stated in Fig.As illustrated in Figure 9, the brake control system 62 transmits a vehicle speed to the speed limit controller 156. An image processing module 142 may continuously determine the hitch angle between the vehicle 14 and the trailer 12, as described herein. The powertrain control system 66 may transmit the current state of the transmission to the speed limit controller 156.

[0066] Once the desired threshold speed is calculated by the speed limit controller 156, the speed limit controller 156 generates a speed limit command based on a desired threshold speed and a current speed of the vehicle 14. The speed limit controller 156 outputs data in the form of a speed limit command to the brake control system 62, the powertrain control system 66, and / or any other suitable system within the vehicle 14, which is then fed back to the plurality of inputs 62, 66, 142 to re-evaluate the effects of other vehicle characteristics affected by the implementation of the speed limit command or other changes to the trailer backup assist system 10.Accordingly, the speed limit controller 156 continuously processes information from the plurality of inputs 62, 66, 142 to provide accurate steering angle commands that place the trailer 12 on the desired curvature κ2 and the desired return path 16 without significantly exceeding or sharply varying the vehicle threshold speed limit of the desired curvature κ2.

[0067] The closed-loop speed limit controller 156 is configured such that the threshold speed limit of the vehicle 14 can be a function of both the desired command curvature κ2 and the hitch angle γ. As a result, the speed can be automatically limited to a range that allows for consistent operation and maximum maneuverability. Speed ​​and jackknife warnings can be significantly reduced or substantially eliminated from system operation altogether. Furthermore, driver braking may only be necessary based on a user comfort level or the desired speed for moving the trailer 12. It may not be necessary to keep the trailer backup assist system 10 operating or to enhance the maneuverability of the trailer backup assist system 10.As described herein, the speed limit controller 156 may determine a first speed limit based on a desired command curvature κ2 and a second speed limit based on the current hitch angle γ. The speed limit controller 156 may filter the two speed limits to determine a threshold vehicle speed limit. For example, the speed limit controller 156 may set the threshold vehicle speed limit to the lower of the first and second speed limits. Alternatively, a higher-order comparative analysis may be used by the speed limit controller 156, as described in more detail below.

[0068] With reference to Fig.10 illustrates an embodiment of the trailer backup assist system 10 in which the trailer backup assist system 10 is configured to monitor the hitch angle γ and the desired command curvature κ2 to control the threshold speed of the vehicle 14, thereby enabling the trailer backup assist system 10 to assist in preventing unacceptable backing conditions by limiting the threshold speed of the vehicle 14.

[0069] The Fig.The method illustrated in Figure 10 generally begins when the trailer backup assist system 10 is activated at step 160. At step 160, the trailer backup assist system 10 begins the process of steering the vehicle 14 along the desired command curvature κ2 at a threshold speed limit, as described above. At step 162, the kinematic relationship between the trailer 12 and the vehicle 14 to which the trailer 12 is attached is determined. To determine the kinematic relationship at step 162, various parameters of the vehicle 14 and the trailer 12 are sensed or otherwise determined so that the trailer backup assist system 10 can generate steering commands for the power steering system 64 according to the desired curvature κ2 or the desired reversing path 16 of the trailer 12.

[0070] As mentioned with reference to Fig.5, the kinematic parameters for defining the kinematic relationship may include, among other previously described variables and parameters, a length of the trailer 12, a wheelbase of the vehicle 14, a distance from a hitch connection to a rear axle of the vehicle 14, and a hitch angle γ between the vehicle 14 and the trailer 12. After the kinematic relationship has been determined, the trailer backup assist system 10 may proceed to step 164 to determine a current hitch angle γ by receiving an input from a sensor 44 ( Fig.1) or by executing a hitch angle estimation routine 110 performed by the trailer backup assist system 10 using, among other inputs related to the kinematic relationship, a yaw rate sensor 58 of the trailer 12, a yaw rate sensor 58 of the vehicle 14, and as further described in co-pending U.S. Patent No. 9,340,228 B2, entitled "TRAILER MOTION AND PARAMETER ESTIMATION SYSTEM," the entire disclosure of which is hereby incorporated by reference. Concurrently, the desired command curvature κ2 is received from the input device 18 at step 168, which is processed based on the input of the input device 18 and the kinematic relationship. Thereafter, the trailer backup assist system 10 determines a first maximum vehicle speed limit based on the hitch angle γ at step 166, as described above.A second maximum speed limit is determined at step 170 based on the desired command curvature κ2, as also described above.

[0071] According to the illustrated embodiment, at step 172, the trailer backup assist system 10 compares the first maximum speed limit based on the hitch angle γ with the second maximum speed limit based on the desired command curvature κ2 and sets the vehicle threshold speed limit to the lower of the two values. Accordingly, at step 174, if the first speed limit is lower than the second speed limit, the vehicle speed limit is set to the first speed limit. However, if the first speed limit is greater than the second speed limit, at step 176, the second speed limit is set as the vehicle threshold speed limit. The trailer backup assist system 10 may continue to repeat steps 162-178 as long as the trailer backup assist system 10 remains active (step 160).

[0072] The trailer backup assist system 10 continues to monitor the hitch angle γ and the input device 18 to generate and implement an appropriate vehicle threshold speed, which may be performed using the speed sensors 78. The trailer backup assist system 10 may then compare the first and second vehicle speed limits and determine whether intervention is desired based on any comparative analysis.As discussed above, the threshold speed may be a speed at which the trailer backup assist system 10 is capable of generating and implementing a steering command to prevent the hitch angle γ from approaching the articulation angle γ(j) at an uncontrollable rate, which may be influenced by, among other things, the speed of the processor 192, the responsiveness of the power steering system 64 and, in particular, the electric steering motor 84, and the length L of the trailer 12. The speed threshold may be predetermined and stored for access by the trailer backup assist system 10 when performing a comparison of the first and second vehicle speed limits to the threshold speed. The speed threshold may be estimated based on the parameters provided herein, while being conservative in estimating L for a short trailer length.

[0073] With reference to Fig. 11 illustrates the trailer backup assist system 10 according to an embodiment in which the hitch angle γ and the desired command curvature κ2 are continuously monitored. It may be advantageous to implement a higher-order function or LUT to generate a first or second speed limit from the hitch angle γ and / or the desired command curvature κ2. Instead of simply assigning the threshold speed limit to the minimum, as described with reference to Fig. 10, it may further be desirable to have a primary and secondary fixed speed limit that allows for higher vehicle speeds as the absolute value of the rate of the hitch angle γ decreases and / or the input magnitude of the desired command curvature κ2 decreases, resulting in a decrease in the absolute rate of the hitch angle γ.

[0074] As in Fig.11, the system begins at step 182. At step 184, the trailer backup assist system 10 calculates whether the rate of the hitch angle γ is increasing or decreasing. If the hitch angle γ is not decreasing, the system 10 proceeds to step 186 and sets a primary fixed speed limit based on values ​​stored within a LUT or by any other means. At step 183, the desired command angle is received from the input device 18. At step 188, the trailer backup assist system 10 receives the desired command angle and calculates the corresponding command curvature κ2, which is provided to the system from the input device 18 or any other suitable device. At step 190, the trailer backup assist system 10 calculates whether the desired command curvature κ2 is less than the hitch angle γ.If the desired command curvature κ2 is not less than the hitch angle γ, the primary speed limit established at step 192 is used. However, if the desired command curvature κ2 is less than the current hitch angle γ, a secondary speed limit is established at step 194. The primary and secondary speed limits are both input to a filter within the controller at step 196. Based on the predefined calculation method within the filter, the filter may determine the vehicle's threshold speed limit based on the current input primary and secondary set speed limits. The trailer backup assist system 10 may continue to repeat steps 184-198 as long as the trailer backup assist system 10 remains active (step 198).

[0075] If only the primary speed limit is specified, the vehicle speed limit is set to the primary speed limit accordingly. If a primary speed limit and a secondary speed limit are specified, the speed limits are filtered to determine the vehicle threshold speed. The filter can be configured as a discrete-time low-pass filter of any order, a continuous-time low-pass filter of any order, and / or a band-pass filter.Alternatively, the controller 26 may calculate the threshold speed based on an average of the primary and secondary speed limits, set the speed limit to the higher or lower value, interpolate between any number of values, use a best-fit analysis, and / or use any other comparative technique that can remove errors within the trailer backup assist system 10. The vehicle threshold speed may be filtered before being passed to the feedback control, which may help smooth transitions between threshold speed limits.

[0076] The primary speed limit may be set based on any desired input within the trailer backup assist system 10. Similarly, the secondary speed limit may also be set based on any other desired input. If more than a single input is present, the controller 26 may then filter the first and second inputs based on any known method to determine a current threshold speed for the vehicle 14. It is also contemplated that the controller 26 may determine a threshold vehicle speed based on any number of monitored inputs from the vehicle 14 and / or the trailer 12 during use.

[0077] With reference to Fig. 10 and Fig.11, the trailer backup assist system 10 may compare the vehicle threshold speed determined at step 172 with the actual vehicle speed. If the vehicle speed is below the threshold speed, the trailer backup assist system 10 may continue without intervention. If the vehicle speed is above the threshold speed, the trailer backup assist system 10 may take actions such as causing the powertrain control system 66 to reduce engine power, which may be accomplished by adjusting the throttle position to reduce power below that demanded by the accelerator pedal position, as commanded by the driver. The trailer backup assist system 10 may continue to monitor the vehicle speed to determine if the action is sufficient to reduce the speed of the vehicle 14 below the threshold speed.If the vehicle speed has been reduced below the threshold speed at such a point, the trailer backup assist system 10 may return to normal operation or may continue to cause the powertrain control system 74 to operate at a reduced throttle position for as long as necessary to effectively maintain the vehicle speed below the threshold speed. If, after reducing engine power, the trailer backup assist system 10 determines that the vehicle speed is still above the threshold speed, the trailer backup assist system 10 may cause the vehicle brake control system 62 to apply the vehicle brakes, thereby applying braking torque to the vehicle 14 to further attempt to decelerate the vehicle speed below the threshold speed.

[0078] Again, the trailer backup assist system 10 may continue to cause the vehicle 14 to operate with reduced engine power and with the brakes applied for as long as necessary to effectively maintain the vehicle speed below the threshold speed. Similarly, the trailer backup assist system 10 may reduce the braking torque, including to zero, and restore engine power if it is determined that no further intervention is necessary. However, if it is determined that reducing engine power and applying braking torque are not sufficient to reduce the speed of the vehicle 14 below the threshold speed, the trailer backup assist system 10 may take further action, including alerting the driver, including by displaying a warning message on the display 100 of the vehicle HMI 98 or by outputting an audible tone, such as through the speaker 96.It is noted that the actions described herein may be performed in various alternative orders in various embodiments, including initially warning the driver before reducing engine power and applying braking torque. In further alternative embodiments, the trailer backup assist system 10 may be configured to apply braking torque before reducing engine power.

[0079] The trailer reversing assistance system 10 with the features from Fig.11 can operate at higher speeds during straight-line or small-curvature maneuvers, where a large distance must be covered at low hitch angles and small input sizes of a desired command curvature κ2. Furthermore, jackknife robustness can be improved by reducing the threshold speed when the system transitions to high hitch angle conditions or is close to a jackknife condition. Furthermore, changes in vehicle speed may feel smoother and more consistent to an occupant during a turn with the varying speed threshold determined based on multiple inputs and filtering those inputs, as the system can regulate the vehicle threshold speed within a speed for safe operation before the onset of an unacceptable back-up condition.

[0080] It will be understood by one of ordinary skill in the art that the construction of the described invention and other components is not limited to any particular material. Other embodiments of the invention disclosed herein may be formed from a variety of materials, unless otherwise described herein.

[0081] For the purposes of this disclosure, the term "coupled" (in all its forms, coupling, coupled, etc.) generally means the direct or indirect interconnection of two components (electrical or mechanical). Such interconnection may be of a stationary type or a movable type. Such interconnection may be achieved with the two components (electrical or mechanical) and any additional intermediate members formed integrally as a single unitary body with each other or with the two components. Such interconnection may be of a permanent type or of a detachable or releasable type, unless otherwise specified.

[0082] Furthermore, any arrangement of components to achieve the same functionality is effectively "linked" to achieve the desired functionality. Therefore, any two components combined here to achieve a particular functionality can be considered "linked together" such that the desired functionality is achieved regardless of architectures or intermediate components. Likewise, any two components so linked can also be considered "operably connected" or "operably coupled" to achieve the desired functionality, and any two components capable of being so linked can also be considered "operably coupled" to achieve the desired functionality.Some examples of operably interposable include, but are not limited to, physically pluggable and / or physically interacting components and / or components that can interact wirelessly and / or wirelessly interacting components and / or logically interacting components and / or components that can interact logically.

[0083] It is also important to note that the construction and arrangement of the elements of the invention as shown in the embodiments are illustrative only. While only a few embodiments of the present innovations have been described in detail in this disclosure, one skilled in the art who reads this disclosure will readily recognize that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, parameter values, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter presented.For example, elements shown as being integrally formed may be constructed from multiple parts, or elements shown as being comprised of multiple parts may be integrally formed, the function of the interfaces may be reversed or otherwise varied, the length or width of the structures and / or links or connectors or other elements of the system may be varied, and the type or number of adjustment positions provided between the elements may be varied. It should be noted that the elements and / or assemblies of the system may be constructed from any of a wide variety of materials that provide sufficient strength or durability and in any of a wide variety of colors, textures, and combinations. Accordingly, all such modifications are intended to be within the scope of the present inventions.Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the desired and other embodiments without departing from the spirit of the present invention.

[0084] It is understood that any described processes or steps within described processes may be combined with other disclosed processes or steps to form structures within the scope of the present invention. The exemplary structures and processes disclosed herein are for illustrative purposes and should not be construed as limiting.

[0085] It is also to be understood that variations and modifications may be made to the above structures and methods without departing from the concepts of the present invention, and it is further understood that such concepts are intended to be covered by the following claims unless such claims expressly state otherwise. Key to symbols

[0086] Fig. 10 Activate Trailer Backup Assist System Activating the trailer reversing assistance system Determine Kinematic Relationship Determining kinematic relationships Determine Hitch Angle Determining the coupling angle Receive Curvature Command Receiving curvature instruction Determine First Maximum Speed ​​Limit Determining the first maximum speed limit Determine Second Maximum Speed ​​Limit Determining the second maximum speed limit First speed limit > second speed limit? First speed limit > Second speed limit? No No Yes Yes Set Vehicle Speed ​​Limit To First Speed ​​Limit Set vehicle speed limit to first speed limit Set Vehicle Speed ​​Limit To Second Speed ​​Limit Setting vehicle speed limit to second speed limit Trailer Backup Assist System Still Active? Trailer reversing assistance system still active? Yes Yes No No END End

Claims

[1] Trailer reversing assistance system comprising: a hitch angle sensor configured to determine a hitch angle between a vehicle and a trailer attached thereto; an input device configured to accept an input instruction corresponding to a trailer path instruction curvature; a controller configured to determine a vehicle threshold speed limit by determining a first vehicle speed limit based on the hitch angle and a second vehicle speed limit based on the trailer path command curvature, the controller generating commands to limit the vehicle speed in a reverse direction to below the vehicle threshold speed limit, characterized by , that the controller is further configured to set the vehicle threshold speed limit to the lower of the first and second vehicle speed limits as a magnitude of a trailer path command curvature increases and to set the vehicle threshold speed limit to the higher of the first and second vehicle speed limits as the magnitude of the trailer path command curvature decreases. [2] A trailer backup assist system according to claim 1, wherein the input instruction controls at least one of a braking system, an engine torque, and a transmission gear selection to thereby control the vehicle speed in the reverse direction. [3] Trailer reversing assistance system according to claim 2, wherein the braking system is a vehicle braking system. [4] The trailer backup assist system of claim 1, wherein the threshold vehicle speed limit is the higher of the first and second vehicle speed limits when a magnitude of a hitch angle rate decreases and the desired trailer path command curvature is less than an instantaneous trailer path curvature. [5] The trailer backup assist system of claim 1, wherein the input device includes a rotatable knob configured to be mounted in a vehicle interior. [6] A method for controlling the speed of a motor vehicle, the method comprising: Determining a coupling angle between a vehicle and a trailer attached to the vehicle: Determining a trailer path curvature command based on an input of an input device; Calculating a first vehicle speed limit based on the hitch angle; Calculating a second vehicle speed limit based on the trailer path curvature instruction; Determining a threshold vehicle speed limit based on the first and second vehicle speed limits; and Limiting, by means of a control, the speed of the vehicle to the vehicle threshold speed, characterized by the controller sets the threshold vehicle speed limit to the higher of the first and second vehicle speed limits when a magnitude of a hitch angle rate decreases and a desired trailer path command curvature is less than an instantaneous trailer path curvature. [7] The method of claim 6, wherein an optimal speed of the vehicle is maintained by controlling at least one of a braking system, a powertrain torque output, and a transmission gear selection to assist a power steering system in positioning the vehicle on a desired path and maintaining a vehicle path error within a desired range. [8] A method according to claim 6, wherein values ​​stored in a look-up table include a relationship between the desired trailer curvature and a time to reach the desired trailer curvature or between a first or second speed limit and a hitch angle and / or the desired trailer curvature. [9] The method of claim 6, wherein the input device is biased toward a neutral position.

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