Patent Publication Number: US-11654965-B2

Title: Method and system for steering control during reverse vehicle operation for maneuvering of a trailer

Description:
BACKGROUND 
     This arrangement relates to a system and method for providing steering control during vehicle reverse operation when maneuvering a trailer in a reverse direction with turn or the like and sometimes maximizing sharpness of the maneuvering turning movement. In an end position the vehicle and trailer are oriented in alignment. 
     Maneuvering a trailer can be a hard task for an inexperienced driver. In addition to the fact that a trailer must be actively stabilized in backwards movement, the steering is not intuitive. To correct the drift of a trailer to one side, the driver must steer in this direction to maneuver it back to the center. The embodiments herein support a driver in maneuvering a trailer. 
     SUMMARY 
     One embodiment is directed to a trailer tow assist system for assisting in rearward maneuvering of a trailer attached to a vehicle. The trailer tow assist system includes a rear video camera for providing a rearward image of the trailer and surroundings; a vehicle interior display and an input device for selectively displaying a rearward image from the rear video camera, and the input device configured to receive inputs from a driver; a yaw determination device for sensing a yaw angle of the vehicle; a steering angle sensor for sensing a vehicle steering angle of front wheels of the vehicle; a vehicle speed determination device for determining a vehicle speed of the vehicle; and an electronic processor and a memory. When a trajectory mode and a desired turn angle value are received from a driver, the electronic processor is configured to: receive a yaw angle for the vehicle; determine a trailer angle for the trailer relative to the vehicle based upon video data received from the rear video camera; determine a trailer trajectory based on the desired turn angle value, the trailer angle, vehicle yaw angle, and physical properties of the vehicle and trailer; and display the trailer trajectory on the vehicle interior display with the rearward image of the trailer and surroundings. When an automatic steering maneuver mode is selected by a driver, the electronic processor is configured to: provide an initial vehicle steering angle signal to a vehicle steering wheel position controller to position the steering angle of the vehicle for performing the trailer maneuvering operation corresponding to the desired turn angle value; upon rearward movement of the vehicle, updating the vehicle steering angle signal based on the desired turn angle value, the trailer angle, the vehicle speed, the vehicle yaw angle, and the physical properties of the vehicle and trailer, and provide the updated vehicle steering angle signal to the vehicle steering wheel position controller to control the vehicle steering angle to achieve the desired turn angle value with the vehicle and the trailer aligned after the maneuvering. 
     Another embodiment is a method for assisting in rearward maneuvering of a trailer attached to a vehicle with a trailer tow assist system including an electronic processor. The method operates by determining a trailer angle for the trailer relative to the vehicle based upon video data received from a rear video camera; and receiving a yaw angle for the vehicle. In response to inputs from a driver to select a trajectory mode and to select a desired turn angle value for rearwardly maneuvering the trailer, the method operates by determining with the electronic processor a trailer trajectory based on the desired turn angle value, the trailer angle, the vehicle yaw angle, and physical properties of the vehicle and the trailer; and displaying the trailer trajectory on the vehicle interior display with a rear image of the trailer and surroundings. A driver is then capable of positioning the vehicle at an appropriate position for maneuvering the trailer in a rearward direction to a desired location by moving the vehicle and trailer to align the trailer trajectory provided on the vehicle interior display with a desired location. 
     Another embodiment is directed to a non-transitory computer readable medium including program instructions executed by an electronic processor for assisting in rearward maneuvering of a trailer attached to a vehicle along a trailer trajectory. The electronic processor is configured for determining a trailer angle for the trailer relative to the vehicle based upon video data received from a rear video camera; receiving a yaw angle for the vehicle; receiving a steering angle of front wheels of the vehicle; and receiving a vehicle speed of the vehicle. The electronic processor performs a trailer steering maneuver along the trailer trajectory corresponding to a desired turn angle value by: determining an initial vehicle steering angle signal based on the desired turn angle value, the trailer angle, the vehicle yaw angle, and physical properties of the vehicle and the trailer; providing an initial vehicle steering angle signal to a vehicle steering wheel position controller to position the steering angle of the vehicle for performing the trailer steering maneuver corresponding to the desired turn angle value; upon rearward movement of the vehicle, updating the vehicle steering angle signal based on the desired turn angle value, the trailer angle, the vehicle speed, the vehicle yaw angle, and the physical properties of the vehicle and trailer, and providing the updated vehicle steering angle signal to the vehicle steering wheel position controller to automatically control the steering angle of the vehicle to maneuver the trailer along the trailer trajectory to achieve the desired turn angle value with the vehicle and the trailer aligned after the maneuvering. 
     Other aspects, features, and embodiments will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a top view of a vehicle and trailer on a roadway and in a rearwardly desired position. 
         FIG.  2    illustrates a block diagram of one embodiment of a trailer tow assist system for assisting in rearward maneuvering of a trailer. 
         FIG.  3    illustrates a flow chart for an embodiment of a trajectory mode of the tow assist system. 
         FIG.  4    illustrates a flow chart for an embodiment of an automatic steering maneuver mode of the tow assist system. 
         FIG.  5    illustrates an exemplary image for display depicting a trailer trajectory and a trailer with surroundings. 
         FIG.  6    shows a geometric diagram of a vehicle with a connected trailer. 
         FIG.  7    illustrates a block diagram showing the operation of an electronic processor(s). 
         FIGS.  8 A- 8 D  illustrate graphs of vehicle data for a desired turn angle of 90 degrees. 
         FIGS.  9 A- 9 D  illustrate graphs of vehicle data for a desired turn angle of 90 degrees with a ten degree trailer angle at start. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments are explained in detail, it is to be understood that this disclosure is not intended to be limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. Embodiments are capable of other configurations and of being practiced or of being carried out in various ways. 
     A plurality of hardware and software based devices, as well as a plurality of different structural components may be used to implement various embodiments. In addition, embodiments may include hardware, software, and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software (for example, stored on non-transitory computer-readable media) executable by one or more electronic controllers. For example, “units,” “control units,” and “controllers” described in the specification can include one or more electronic controllers, one or more memories including non-transitory computer-readable media, one or more input/output interfaces, one or more application specific integrated circuits (ASICs) and other circuits, and various connections or connectors (for example, wires, printed traces, and buses) connecting the various components. 
       FIG.  1    shows a vehicle  30  and trailer  32  disposed on a roadway  34 . From a starting position in the roadway  34 , the vehicle  30  moves in a reverse direction path  36  to maneuver the trailer  32  in a driveway  38  with assistance from a trailer tow assist system and a driver operating an accelerator pedal and brake pedal or the like. In this embodiment, the trailer tow assist system controls vehicle steering to move the vehicle  30 /trailer  32  combination throughout a 90° backwards turn angle along a trailer trajectory that is a sharpest possible path going rearwardly a shortest possible distance. Other desired turn angle values are contemplated, including a first range between about 10 degrees and about 90 degrees and/or a second range between about −10 degrees and −90 degrees in some embodiments. In one embodiment, the trailer  32  is a common non-steering one-axle trailer. In some embodiments, the trailer  32  has a length from about 1 to about 20 meters. In some embodiments, the sharpest possible path to obtain the desired turn angle is not desired. In most embodiments, a final position for the trailer  32  and the vehicle  30  are provided in a longitudinal orientation. Thus, the trailer  32  and the vehicle  30  are aligned in the same direction of travel. 
       FIG.  2    shows a block diagram view of a trailer tow assist system  40  for controlling vehicle steering to maneuver a trailer  32 . In one embodiment, the trailer tow assist system  40  includes an electronic tow assist unit  44 . The electronic tow assist unit  44  includes an electronic processor  50  and a memory. The memory includes one or more memory modules, such as a random access memory (“RAM”)  54  and/or an electronically erasable programmable read-only memory (“EEPROM”)  56 . An input/output interface  58  transmits and receives information over a communication bus  60 . The electronic processor  50  processes the information by executing one or more applications or modules. The applications or modules can be stored as instructions or commands in the memory  54 ,  56 . The electronic processor  50  also stores information in the memory  54  generated by applications. 
     The communication bus  60  shown in  FIG.  2    is a FlexRay automotive communication bus, controller area network (CAN) bus or other type of communication link between a plurality of control units, sensors, and other devices. In some embodiments, the communication bus  60  connects the electronic tow assist unit  44  to an electronic steering wheel position controller  62 , such as a power steering control motor, that is controlled by the electronic tow assist unit  44  in a trailer tow assist operating mode. 
       FIG.  2    also shows a vehicle speed limiter  66  that limits speed of a vehicle in an automatic steering maneuver mode. In one embodiment, the vehicle speed limiter  66  is an electronic drive control system of a vehicle that receives an input of a vehicle speed limit signal from the electronic processor  50  from the tow assist system that limits the reverse direction speed for a vehicle to prevent a driver from exceeding the vehicle speed limit for an automatic steering maneuver mode. 
       FIG.  2    shows a rear video camera  70  for providing images from the rear of a vehicle. The images can include a trailer that is hitched to the vehicle. In one embodiment, the images are a panoramic view. In another embodiment, multiple video cameras are provided. The rear video camera  70  provides video data over the communication bus  60  to the electronic processor  50 . 
       FIG.  2    shows a vehicle yaw angle determination device  74  provided on a vehicle. In one embodiment, the yaw angle determination device  74  includes a gyro sensor that communicates yaw rate to units via the communication bus  60 . The yaw rate is integrated to determine a yaw. In another embodiment, the vehicle yaw angle is calculated based on vehicle speed and vehicle steering angle. Thus, the vehicle yaw angle determination device is provided by the electronic processor  50  in one embodiment. The vehicle yaw angle is determined with respect to a starting position for a vehicle maneuver. 
     A steering angle sensor  80  is connected to the communication bus  60  to provide a steering wheel position to the electronic processor  50  via the input/output interface  58 . In one embodiment, the steering angle sensor  80  is disposed on a steering column of the steering device. In another embodiment, the steering angle sensor  80  is configured to sense rotation of a pinion gear secured to a steering shaft of the vehicle. In another embodiment, the steering angle sensor  80  determines steering angle based on motor rotation of the power steering control motor and a ratio with respect to the rack and pinion gear. 
     In one embodiment, a vehicle speed determination device  84  shown in  FIG.  2    determines a vehicle speed and provides the vehicle speed to other units via the communication bus  60 . In another embodiment, the vehicle speed determination device  84  is a vehicle speed sensor. In another embodiment, calculations of other information provide vehicle speed. 
       FIG.  2    shows a vehicle interior display  90  and an input device  94 . In one embodiment, the vehicle interior display  90  is a display panel for displaying images and instructions to a driver. The input device  94  is a keyboard, joystick, keypad or other data entry mechanism, such as a microphone and voice analysis to receive voice commands. In one embodiment, the arrangement is a touchscreen  98  that integrates the vehicle interior display  90  and input device  94  into a single element that displays information and images and receives touch inputs. In one embodiment, the touchscreen  98  is disposed at a console in the vehicle interior. 
     Operation 
     In operation, the electronic tow assist unit  44  includes a trajectory mode and an automatic steering maneuver mode. The trajectory mode is selected and operated before the automatic steering maneuver mode as follows. 
     Trajectory Mode. 
       FIG.  3    shows a flow chart  100  of the trajectory mode for the electronic tow assist unit  44  shown in  FIG.  2   . While a single electronic tow assist unit  44  is shown in  FIG.  2   , multiple control units and/or electronic processors  50  can perform the various functions shown in  FIG.  3   . The multiple steps shown in  FIG.  3    can occur essentially simultaneously or in parallel with multiple electronic processors of the electronic tow assist unit  44 . 
     At step  104 , in one embodiment, a trajectory mode selection is received by the electronic processor  50  from the input device  94  over the communication bus  60 . Thereafter, at step  108 , the electronic processor  50  also receives a desired turn angle value from the input device  94 . The driver can input the desired turn angle value before selecting the trajectory mode in another embodiment. The desired turn angle value can be from 10 degrees to 90 degrees and from −10 degrees to −90 degrees depending on the direction of the desired reverse turn maneuver of the trailer  32 . 
     At step  112  shown in  FIG.  3   , the electronic processor  50  is configured to determine trailer angle based on video data received from the rear video camera  70  over the communication bus  60 . The trailer angle is defined by the relative orientation of the trailer  32  with respect to the vehicle  30 . When the vehicle  30  and trailer  32  are aligned along the same axis, for example when the vehicle  30  is driven forward in a straight direction, the trailer angle is zero degrees. After step  112 , the electronic processor advances to step  116 . 
     At step  116 , the electronic processor  50  receives a yaw angle from the vehicle yaw angle determination device  74  on the vehicle  30 . The vehicle yaw angle is determined by integrating the yaw rate signal in one embodiment. The electronic processor  50  advances to step  120 . 
     At step  120 , the electronic processor  50  determines a trailer trajectory for the desired turn angle value that is based on the desired turn angle value, the trailer angle, the vehicle yaw angle, and physical properties of the vehicle and trailer. The determination is provided when the vehicle  30  is stationary or being driven by a driver. Thereafter, the electronic processor  50  advances to step  124 . Physical properties or parameters of the vehicle and trailer can include vehicle wheelbase, vehicle overhang, trailer length, maximum wheel angle, and maximum wheel angle change rate. 
     At step  124 , the electronic processor  50  displays a trailer trajectory on the vehicle interior display  90  with the rearward image of the trailer  32  and surroundings. The trailer trajectory is superimposed or an overlay on the video image. The electronic processor  50  advances to step  128 . 
     At decision step  128 , the electronic processor  50  determines whether a driver input to the input device  94  selecting an automatic steering maneuver mode has been received and the vehicle is in reverse gear and the vehicle is stationary due to application of the brakes. So long as the inputs are not received, decision step  128  returns to step  112  and again determines the trailer angle, vehicle yaw angle, and a trailer trajectory as discussed above. Thus, when the vehicle  30  and trailer  32  are moving, the trailer trajectory is updated to show the new relative position thereof shown in the rearward image of the trailer  32  on the vehicle interior display  90 . During operation in the trajectory mode, a driver views the trailer trajectory on the vehicle interior display  90  and manually moves the vehicle  30  and the trailer  32  to a location so that the trailer trajectory for each of the trailer wheels leads to a desired area where the driver intends to maneuver the trailer to. 
     At decision step  128  when the electronic processor  50  receives an input that the vehicle is not moving, and that a driver has selected the automatic steering maneuver mode, the electronic processor  50  advances to step  132 . This selection is made when the driver sees the trailer trajectory directed to a desired trailer location and provides a manual actuation to select the mode with the input device  94 . In some embodiments, the vehicle  30  must also be in reverse gear to advance to the automatic steering maneuver mode. 
     Automatic Steering Maneuver Mode 
       FIG.  4    shows a flow chart  200  of the switched to automatic steering maneuver mode corresponding to step  132  shown in  FIG.  3   . The automatic steering maneuver mode provides automatic vehicle steering to achieve the vehicle maneuvering rearward along the trailer trajectory as follows. 
     At step  212 , the electronic processor  50  is configured to determine trailer angle based on video data received from the rear video camera  70  over the communication bus  60 . The trailer angle is defined by the relative position of the trailer  32  with respect to the vehicle  30 . After step  212 , the electronic processor advances to step  216 . 
     At step  216 , the electronic processor  50  receives a vehicle yaw angle from the vehicle yaw angle determination device  74  on the vehicle  30 . The vehicle yaw angle is determined by integrating the yaw rate signal in one embodiment. The electronic processor  50  advances to step  220 . 
     At step  220 , the electronic processor  50  receives a steering angle for front wheels of the vehicle  30 , which is sensed by the steering angle sensor  80  and provided over the communication bus  60 . The electronic processor  50  advances to decision step  230 . 
     At decision step  230 , the electronic processor  50  determines whether automated steering maneuver mode has already started. If not, the electronic processor  50  advances to step  234 . At step  234 , the electronic processor  50  provides an initial vehicle steering angle signal to an electronic steering wheel position controller to prepare for reverse operation of the vehicle  30 . The initial vehicle steering angle signal is determined to follow a trailer trajectory based on the desired turn angle value, the trailer angle, the vehicle yaw angle, and physical properties of the vehicle  30  and the trailer  32 . Thereafter, the electronic processor  50  returns to step  212  and repeats the steps  212 ,  216 ,  220 ,  224 . 
     At decision step  230 , when the initial vehicle steering was already provided, the electronic processor advances to decision step  240 . At step  240 , the vehicle steering angle signal is updated based on the desired turn angle value, the trailer angle, the vehicle speed, the vehicle yaw angle, and the physical properties of the vehicle  30  and the trailer  32 . The electronic processor  50  returns and repeats the illustrated steps  212 ,  216 ,  220 ,  224 ,  230 ,  240  until the vehicle  30  is removed from reverse gear or otherwise disabled by an input from a driver. In one embodiment, the vehicle trailer tow assist system  40 , or at least the automatic steering maneuver mode thereof, is automatically disabled or discontinued when the vehicle  30  is shifted out of reverse gear. 
     The above steps shown in the embodiments of  FIGS.  3  and  4    are provided for purposes of illustration. The steps can occur in an entirely different order. 
     ADDITIONAL EMBODIMENT(S) 
     In one embodiment, the trajectory mode shown in  FIG.  3    continues to operate and display the trailer trajectory on the vehicle interior display  90  with the rear image of the trailer and surroundings during the automatic steering maneuver mode.  FIG.  5    shows an image of the trailer  32  and surroundings.  FIG.  5    also shows the trailer trajectory has pathways  250  corresponding to each of the spaced trailer wheels. The image shown in  FIG.  5    is updated continuously and provided on the vehicle interior display  90 , including continuing to perform the trajectory mode including displaying the trailer trajectory  250  on the vehicle interior display  90  with the rear image of the trailer  32  and surroundings while the electronic processor  50  is automatically controlling the steering angle of the vehicle  30 . In another embodiment, the trailer trajectory is a single path corresponding to a midpoint of the trailer  32 . 
     Geometrical Equations 
       FIG.  6    shows a geometric diagram of the vehicle  30  with the trailer  32  in combination. Further,  FIG.  6    shows one embodiment of the angles for determining the various values for algorithms executed in the operating modes relative to an X-Y axis. 
     A first equation for trailer angle rate is as follows: 
     
       
         
           
             
               
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     The above equation is based on vehicle speed ν, trailer angle γ, steering angle δ, vehicle overhang l 12  (distance from rear axle of the vehicle to trailer ball), vehicle wheelbase l 1 , and trailer length l 2  (distance from hitch to trailer axle). The vehicle yaw rate {dot over (ψ)} 1  is based on the equation as follows: 
     
       
         
           
             
               
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     The above vehicle yaw rate equation is based on steering angle δ, vehicle wheelbase l 1  and vehicle speed ν. Integration of the yaw rate results in a value for yaw ψ 1 . 
     P-I-D Cascade Structure 
       FIG.  7    shows a block diagram  300  of an embodiment of the electronic processor  50  of the trailer tow assist system  40  that operates as a proportional/integral/derivative (P-I-D) cascade structure. In this embodiment, a set yaw value corresponding to the desired turn angle value is provided as a set yaw, wherein a trailer angle error is determined in an inner loop and a vehicle yaw angle error is determined in an outer loop, and wherein the trailer angle error is determined more often than the vehicle yaw angle error in one embodiment. In another embodiment, the trailer angle error and the vehicle yaw angle error are determined at the same rate. 
     The yaw angle value is part of the trailer angle equation. Changing the vehicle yaw angle therefore influences the trailer angle value. The inner loop shown in  FIG.  7    operates faster than the outer loop. At a given speed and wheel angle, the change rate of the trailer angle is higher than the one of the vehicle yaw angle. 
     The PID cascade structure approach shown in  FIG.  7    is chosen as a control concept in one embodiment. The trailer angle is processed in the inner loop and the vehicle yaw in the outer loop. By designing a cascade control, the inner loop is required to be stable without the outer loop controller, thus the inner loop shown in  FIG.  7    can be operated on its own. Therefore, the first step is to solely develop and tune the inner loop as own controller. Afterwards the system and the inner loop together are considered as the control system for the outer loop. 
     More specifically,  FIG.  7    shows a yaw P-controller  304  that provides a tunable parameter for control. The yaw output=Kyaw_P*(set yaw−measured yaw) is tunable and determines sharpness of the turn and needs to be adjusted for different trailer lengths. 
     The electronic processor  50  advances to jackknife saturation  308  shown in  FIG.  7   . Jackknife angles vary with different trailer lengths  12 . The jackknife angle provides a maximum value for the permitted yaw angle output to avoid jackknifing of the trailer  32 . 
     The electronic process or  50  advances to P-controller trailer angle  312  that receives a trailer angle error based on the jackknife output angle minus measured trailer angle as shown in  FIG.  7   . The P-controller trailer angle is a tunable parameter that is stable for a desired operation range. Factors that are tunable include vehicle speed, etc. In one embodiment, gain scheduling occurs. 
       FIG.  7    shows a feed-forward control  320 . The latter part is responsible for a good set-point tracking, whereas the measured feedback of the systems leads to stabilization and error compensation. The feed-forward control  320  calculates the corresponding steady-state vehicle steering angle for a given trailer angle based on a steady-state equation. This wheel angle is added as an offset to the turn angle output from P-controller trailer angle  312  to achieve faster set-point following. 
     The electronic processor  50  then advances to maximum wheel angle saturation  330  as shown in  FIG.  7   . The turn angle combined is compared with a maximum wheel angle so that the steering angle provided to the electronic steering wheel position controller  62  in a car-trailer system  334  does not exceed a maximum wheel angle of the vehicle  30 . The maximum wheel angle is dependent on properties of the vehicle  30  and trailer  32  as discussed above. 
     In general, a PID-controller processes the error of the measured variable in comparison to the set point and consists of three terms: The P-term is proportional to the error, the I-term is proportional to the integral of the error, and the D-term is proportional to the derivative of the error. However, not all terms have to be included to get a proper control quality. 
     Example 1—90 Degree Desired Turn Angle 
       FIGS.  8 A- 8 D  illustrate graphs of vehicle data for a desired turn angle of 90 degrees, which corresponds to the reverse direction path  36  shown in  FIG.  1   .  FIG.  8 A  shows a set or desired trailer angle (set TA) of about 40 degrees. At time 0 seconds, the trailer angle is 0 degrees, as the trailer  32  has about the same axis direction as the vehicle  30 .  FIG.  8 B  shows a desired vehicle steering angle (reqWA) of about 10 degrees. At start up or time 0, the vehicle steering angle is 0 degrees. At about 3 seconds, the actual steering wheel is automatically adjusted to about 10 degrees by the electronic steering wheel position controller  62  in response to the vehicle steering angle signal from the electronic processor  50 . This adjustment is shown in  FIG.  8 B . 
     At about seven seconds time, a driver operates the vehicle in reverse at a negative speed as shown in  FIG.  8 D . At this time the trailer angle begins to increase as shown in  FIG.  8 A , the vehicle steering angle adjusts as shown in  FIG.  8 B , and the vehicle yaw angle and trailer yaw angle change as shown in  FIG.  8 C . After an increase in trailer angle shown in  FIG.  8 A , the steering angle is adjusted to a negative value between 10 and 15 seconds to return the turn angle to about 0 degrees with the vehicle  30  and trailer  32  in the position of 90 degrees from the starting position as shown in  FIG.  1   . At about 45 second time, the vehicle speed returns to zero as the maneuver along a steering path is complete. 
     90 Degree Desired Turn Angle at 10 Degree Trailer Angle Start 
       FIGS.  9 A- 9 D  illustrate graphs of vehicle data for a desired turn angle of 90 degrees with a ten degree trailer angle value at start. Thus,  FIGS.  9 A- 9 D  are similar to  FIGS.  8 A- 8 D . One of the differences is the 10 degree starting trailer angle value at time 0 as shown in  FIG.  9 A . The vehicle steering angle adjusts as shown in  FIG.  9 B .  FIG.  9 C  shows that the vehicle and trailer have different yaw angle values corresponding to the ten degree trailer angle. Of course, upon completion of the maneuver, the trailer angle is zero degrees. 
     While the electronic tow assist unit  44  is illustrated as a separate unit in  FIG.  2   , in some embodiments, the electronic tow assist unit is provided as an algorithm executed by a vehicle assist unit that performs other functions, such as collision avoidance warnings and lane change warnings. 
     Although the system depicts components as logically separate, such depiction is merely for illustrative purposes. In some embodiments, the illustrated components may be combined or divided into separate software, firmware and/or hardware. Regardless of how they are combined or divided, these components may be executed on the same computing device or may be distributed among different computing devices or electronic processors  50  connected by one or more networks or other suitable communication means. 
     Various features, advantages, and embodiments are set forth in the following claims.