DE102015203969B4 - System and method for determining an offset between a measured and a current hitch angle - Google Patents

Abstract

Method for determining an offset (γ (o)) between a measured (γ (m)) and a current (γ (a)) coupling angle between a vehicle (100) and a trailer (110), the method comprising the following steps: • Detection of a measured coupling angle (γ (a)) with a coupling angle sensor (1312) provided on the vehicle (100); when the measured coupling angle (γ (m)) and the steering angle (δ) are constant while the vehicle (100) is reversing; and • determining an offset (γ (o)) between the measured hitch angle (γ (m)) and the current hitch angle (γ (a)) if the measured hitch angle (γ (a)) and the steering angle (δ) during the Reversing the vehicle (100) can be determined as constant.

Description

The invention relates to a method and a system for determining an offset between a measured and a current coupling angle between a vehicle and a trailer.

Reversing a vehicle while towing a trailer is a major challenge for many drivers. This is especially true for drivers who are inexperienced in reversing vehicles with trailers attached, including possibly those who do not drive a trailer regularly (e.g. who have a rented trailer, do not use their own trailer regularly, etc.).

One of the reasons is that reversing a vehicle with a trailer attached requires steering inputs that are reversed from normal steering when reversing the vehicle without a trailer attached and / or require turning to stabilize the vehicle and trailer combination before a transverse position occurs. Another reason is that small errors in steering are amplified while reversing a vehicle with a trailer attached, causing the trailer to deviate from a desired path.

Out DE 10 2011 015 033 A1 a method for determining a drawbar angle between a longitudinal axis of a motor vehicle and a longitudinal axis of a trailer connected to the motor vehicle with a drawbar is known, with a measured value for the drawbar angle being measured at a plurality of times predetermined by a chronological sequence, then at each point in time the A plurality of points in time depending on at least one state variable of the motor vehicle and / or the trailer, an estimated value for the drawbar angle is determined and finally a correction factor for the measured value at each point in time of the plurality of points in time depending on the respective estimated value and one preceding in the chronological order Time certain estimated value is determined. The estimated value is determined in particular as a function of at least one dynamic state variable of the motor vehicle and / or the dimensions of the motor vehicle and / or the trailer.

Out US 2004/0130441 A1 a system for estimating the length of a drawbar of a trailer pulled by a vehicle is known, the estimation being based on signals measured by sensors provided for this purpose for the angle of the front wheels, the vehicle speed, the yaw rate and the coupling angle between the vehicle and the trailer. A corresponding controller for estimating the length of the drawbar is designed in particular to only calculate the estimated value for the drawbar length when certain minimum values for the vehicle speed, the yaw rate and the coupling angle are exceeded.

Out US 2004/0222880 A1 a coupling arrangement for a vehicle / trailer combination is known, an angle sensor for determining a coupling angle according to one embodiment being designed for self-calibration on the basis of vehicle speed and steering angle.

The problem described above is solved by a method with the features of claim 1 or claim 8 and by a system with the features of claim 17. Advantageous further developments result from the dependent claims.

• - Erfassen eines gemessenen Kupplungswinkels mit einem an dem Fahrzeug vorgesehenen Kupplungswinkelsensor;
• - Erfassen eines Lenkwinkels gelenkter Räder des Fahrzeugs;
• - Rückwärtsfahren des Fahrzeugs;
• - Bestimmen, wann während des Rückwärtsfahrens des Fahrzeugs der gemessene Kupplungswinkel und der Lenkwinkel konstant sind; und
• - Bestimmen eines Offsets zwischen dem gemessenen Kupplungswinkel und dem aktuellen Kupplungswinkel, wenn der gemessene Kupplungswinkel und der Lenkwinkel während des Rückwärtsfahrens des Fahrzeugs als konstant bestimmt werden.

According to one aspect of the present invention, a method for determining an offset between a measured and a current hitch angle between a vehicle and a trailer is provided, the method comprising the following steps:

• - Detecting a measured coupling angle with a coupling angle sensor provided on the vehicle;
• - Detecting a steering angle of steered wheels of the vehicle;
• - backing up the vehicle;
• Determining when the measured coupling angle and the steering angle are constant while the vehicle is reversing; and
• - Determination of an offset between the measured coupling angle and the current coupling angle if the measured coupling angle and the steering angle are determined to be constant while the vehicle is reversing.

• - kontinuierliches Erfassen eines gemessenen Kupplungswinkels;
• - kontinuierliches Erfassen eines Lenkwinkels des Fahrzeugs;
• - Bestimmen, wann während eines über eine Distanz oberhalb eines Distanzschwellenwerts erfolgenden Rückwärtsfahrens des Fahrzeugs der gemessene Kupplungswinkel und der Lenkwinkel konstant sind; und
• - Bestimmen eines Offsets zwischen dem gemessenen Kupplungswinkel und dem aktuellen Kupplungswinkel, wenn der gemessene Kupplungswinkel und der Lenkwinkel während des über eine Distanz oberhalb des Distanzschwellenwerts erfolgenden Rückwärtsfahrens des Fahrzeugs als konstant bestimmt werden.

According to another aspect of the present invention, a method for determining an offset between a measured and a current hitch angle between a vehicle and a trailer is provided, the method comprising the following steps:

• - Continuous acquisition of a measured coupling angle;
• - continuous detection of a steering angle of the vehicle;
• - Determining when the measured hitch angle and the steering angle are constant while the vehicle is reversing a distance above a distance threshold value; and
• Determination of an offset between the measured hitch angle and the current hitch angle if the measured hitch angle and the steering angle are determined to be constant while the vehicle is reversing over a distance above the distance threshold value.

• - einem an dem Fahrzeug vorgesehenen Kupplungswinkelsensor, welcher kontinuierlich einen gemessenen Kupplungswinkel erfasst,
• - einem Lenksensor, welcher kontinuierlich einen Lenkwinkel des Fahrzeugs erfasst, und
• - einer Steuervorrichtung zum Bestimmen eines Offsets zwischen dem gemessenen Kupplungswinkel und dem aktuellen Kupplungswinkel, wenn der gemessene Kupplungswinkel und der Lenkwinkel als konstant bestimmt werden, während das Fahrzeug und der Anhänger rückwärts fahren.

According to a further aspect of the present invention, a system for determining an offset between a measured and a current hitch angle between a vehicle and a trailer is provided, comprising:

• - a hitch angle sensor provided on the vehicle, which continuously detects a measured hitch angle,
• - A steering sensor which continuously detects a steering angle of the vehicle, and
• a control device for determining an offset between the measured hitch angle and the current hitch angle if the measured hitch angle and the steering angle are determined to be constant while the vehicle and the trailer are reversing.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the accompanying figures.

• 1 eine Kombination aus Fahrzeug und Anhänger, wobei das Fahrzeug ausgelegt ist, um eine Anhängerrückfahr-Unterstützungsfunktionalität gemäß einer Ausführungsform auszuführen;
• 2 eine Ausführungsform des Anhängerrückfahr-Lenkeingabegeräts gemäß 1;
• 3 eine Skizzenansicht, die ein Kinematikmodell zeigt, das konfiguriert ist, um Informationen bereitzustellen, die beim Bereitstellen einer Anhängerrückfahr-Unterstützungsfunktionalität gemäß einer Ausführungsform verwendet werden;
• 4 ein Flussdiagramm, das zu der Anhängerrückfahrunterstützung gehört;
• 5 ein Blockschaltbild, das eine Ausführungsform des Anhängerrückfahr-Unterstützungssystems veranschaulicht, das ein Anhängerrückfahr-Unterstützungssteuermodul mit einem Kupplungswinkelkalibrierungsprogramm hat;
• 6 eine Skizze, die die Geometrie eines Fahrzeugs und eines Anhängers überlagert mit einem zweidimensionalen X-Y-Koordinatensystem veranschaulicht, das Variablen identifiziert, die verwendet werden, um kinematische Informationen des Systems aus Fahrzeug und Anhänger zu berechnen;
• 7 ein Flussdiagramm, das eine Ausführungsform des Kupplungswinkelkalibrierungsprogramms veranschaulicht;
• 8 ein Flussdiagramm, das ein Initiierungsprogramm veranschaulicht, das vor dem Berechnen des Anhängerkupplungswinkeloffsets ausgeführt wird;
• 9 ein Flussdiagramm, das eine zusätzliche Ausführungsform des Kupplungswinkelkalibrierungsprogramms veranschaulicht; und
• 10 ein Flussdiagramm, das ein Verfahren zum Kalibrieren eines Anhängerrückfahr-Unterstützungssystems vor dem Bestimmen eines Offsets des gemessenen Kupplungswinkels veranschaulicht.

Show it:

• 1 a combination of vehicle and trailer, the vehicle configured to perform trailer backup assist functionality according to an embodiment;
• 2 an embodiment of the trailer reversing steering input device according to 1 ;
• 3 FIG. 13 is a schematic view showing a kinematics model configured to provide information used in providing trailer backup assist functionality in accordance with an embodiment; FIG.
• 4th a flowchart associated with trailer backup assistance;
• 5 Figure 3 is a block diagram illustrating an embodiment of the trailer backup assist system having a trailer backup assist control module with a hitch angle calibration program;
• 6th Figure 12 is a sketch illustrating the geometry of a vehicle and trailer overlaid with an XY two-dimensional coordinate system that identifies variables used to compute kinematic information of the vehicle and trailer system;
• 7th Fig. 3 is a flow chart illustrating one embodiment of the hitch angle calibration program;
• 8th Fig. 3 is a flow diagram illustrating an initiation program executed prior to calculating the hitch angle offset;
• 9 Fig. 3 is a flow diagram illustrating an additional embodiment of the hitch angle calibration program; and
• 10 Figure 4 is a flow chart illustrating a method for calibrating a trailer backup assist system prior to determining an offset of the measured hitch angle.

The disclosure includes trailer backup assist functionality that is relatively inexpensive and offers an intuitive user interface. In particular, such a trailer backup assistance functionality provides for controlling the curvature of a path of a trailer that is attached to a vehicle (ie trailer path control) by allowing a driver of a vehicle to specify a desired path of the trailer by selecting a desired path Enters trailer path as the vehicle and trailer reversing maneuver continues. Although a control button, set of virtual buttons, or a touch screen can be provided to implement trailer curve control, the disclosure is not limited to any particular user interface configuration through which a desired trailer curve is entered. Furthermore, in the event that a steering wheel can be mechanically decoupled from the steered wheels of the vehicle, the steering wheel can also be used as an interface through which a desired trailer path curvature is input. As will be described in detail herein, kinematic information of a system defined by the vehicle and trailer is used to calculate a relationship (ie, kinematics) between the curvature of the trailer and the steering angle of the vehicle in order to correlate changes in steering angle of the vehicle to realize the specified trailer travel determine. Steering commands, which correspond to the changes in the steering angle, are used to control a steering system of a towing vehicle (e.g. electric Power steering system (“electric power assisted steering” (EPAS)) to implement changes in the steering angle of the steered wheels of the vehicle in order to achieve (eg approximate) the specified path of the trailer. The trailer backup assist system automatically controls the vehicle and trailer combination while a driver uses the vehicle transmission, accelerator pedal and brakes to reverse the vehicle and trailer combination. The driver inputs a desired trailer curvature command using an input device such as a trailer steering button.

The disclosure further includes embodiments aimed at determining a hitch angle of the trailer attached to the vehicle. In such an embodiment, the vehicle backup assistance system can utilize a target that is placed on the trailer, allowing the trailer backup assistance system to utilize information captured via image capture and processing of the target. The target object is an identifiable visual target object that can be recorded in an image by the video imaging camera and processed via image processing. According to one embodiment, the target object can be attached to the trailer, preferably within a target placement zone, so that the camera and image processing can capture the target object and its location on the trailer in order to determine trailer-related information, such as the hitching angle between the trailer and the trailer Tow vehicle.

In such embodiments of the disclosed trailer backup assistance system, it may prove advantageous to use information representing a hitch angle between the vehicle and a trailer attached to the vehicle. The disclosure includes embodiments that aim to estimate a current hitch angle of a trailer attached to a vehicle. An inaccurately determined hitch angle can lead to inadequate or unsuitable vehicle system control, especially if the hitch angle information is important to control the vehicle system, such as a trailer backup assist system or a trailer brake control.

To ensure the precision of the measured hitch angle, one embodiment of the trailer backup assist system includes a hitch angle calibration program to determine any offset between the measured hitch angle and the current hitch angle based on certain vehicle and / or trailer characteristics. In one of these embodiments, a method provides for the acquisition of a measured coupling angle with at least one coupling angle sensor provided on the vehicle and the acquisition of a steering angle of the steered wheels of the vehicle. The method further provides reversing and thereby determining an offset between a measured coupling angle and a current coupling angle if the measured coupling angle and the steering angle are constant during reversing of the vehicle. Another of these embodiments provides for the vehicle to be driven forward substantially at a speed just above a speed threshold while a yaw rate of the vehicle is detected and a measured hitch angle of the trailer is detected. The method further provides determining an angular rate based on the measured hitch angle, and then determining an offset between the measured hitch angle and the current hitch angle when the yaw rate and the angular rate are substantially zero. The offset can then be used to more precisely manipulate the actual hitch angle with the trailer backup assist system.

1 Figure 3 shows an embodiment of a vehicle 100 that is designed to perform trailer backup assist functionality. A trailer reverse assist system 105 of the vehicle 100 controls the curvature of the path of a trailer 110 that is on the vehicle 100 is attached. Such control is achieved through the interaction of a power steering system 115 of the vehicle 100 and the trailer backup assistance system 105 carried out. In operation of the trailer backup support system 105 while the vehicle 100 is driven backwards is a driver of the vehicle 100 occasionally in the manner in which he / she provides steering input through a steering wheel for the vehicle 100 can make, limited. This is due to the fact that the trailer backup support system 105 in certain vehicles, the power steering system 115 controls and the power steering system 115 is directly coupled to the steering wheel (i.e. the steering wheel of the vehicle 100 moves in accordance with the steered wheels of the vehicle 100 ). A man-machine interface (HMI) device of the reversing assistance system 105 , such as a button, is used to make changes to the curvature of a path of the trailer 110 to control by executing such commands on the steering wheel of the vehicle 100 be disconnected. However, some vehicles that are designed to provide trailer backup assist functionality in accordance with the disclosure have the ability to selectively Steering movement from the movement of steerable wheels on the vehicle 100 decouple, so that the use of the steering wheel to control changes in the curvature of a path of a trailer during such trailer backup assistance is enabled.

The embodiment of the trailer backup assist system 105 according to 1 has a trailer backup assist control module 120 , a trailer reversing steering input device 125 as well as a hitch angle detection device 130 on. The trailer reverse assist control module 120 is with the trailer reversing steering input device 125 and the hitch angle detector 130 connected to allow the exchange of information between them. The trailer backup assist system control module 120 is on a power steering assist control module 135 of the power steering assist system 115 connected to enable the exchange of information between them. A steering angle detection device 140 of the power steering assist system 115 is with the power steering assist control module 135 connected to provide information. The trailer backup support system 105 is also on a brake system control module 145 attached, and to a powertrain control module 150 to enable the exchange of information between them. Together we define the trailer backup support system 105 , the power steering assist system 115 , the brake system control module 145 , the powertrain control module 150 and the gear shifting device (PRNDL) is a trailer backup assist architecture configured in accordance with an embodiment.

The trailer reverse assist control module 120 is designed to include logic (ie, instructions) for receiving information from the trailer reverse steering input device 125 , the hitch angle detection device 130 , the power steering assist control module 135 , the brake system control module 145 and the powertrain control module 150 to implement. The trailer reverse assist control module 120 (e.g., a trailer curvature algorithm thereof) generates vehicle steering information depending on all or part of the information received from the trailer reverse steering input device 125 , the hitch angle detection device 130 , the power steering assist control module 135 , the brake system control module 145 and the powertrain control module 150 be received. Thereafter, the vehicle steering information becomes the power steering assist control module 135 given to steering the vehicle 100 through the power steering assist system 115 to influence to an induced or intended route of the trailer 110 to realize.

The trailer reversing steering input device 125 transmitted to the trailer backup assist control module 120 Information about the planned or planned route of the trailer 110 define (i.e. trailer steering information). The trailer steering information can have information in connection with an initiated or intended change in the course of the path (e.g. a change in the radius of the path curvature), and information in connection with an indication that the trailer should drive along a path which is defined by a longitudinal center line axis of the trailer is (ie along a largely straight route). The trailer reversing steering input device 125 may include a rotation control input device to provide a driver of the vehicle 100 to enable desired trailer steering actions to be initiated (e.g. commands a desired change in the radius of the path of the trailer and / or commands that the trailer should drive along a substantially straight path (as defined by the longitudinal centerline axis of the trailer). The rotary control input device can be a button that is rotatable about an axis of rotation passing through a top surface / side of the knob. In other embodiments, the rotary control input device may be a knob that is rotatable about an axis of rotation that is substantially parallel to a top surface / side of the Button extends.

At the in 1 shown embodiment works the hitch angle detection device 130 together with a coupling angle detection component 155 of the trailer 110 to the trailer backup assist control module 120 Provide information on an angle between the vehicle 100 and the trailer 110 are related (i.e. hitch angle information). In one embodiment, the hitch angle sensing device 130 a camera-based device, such as a vehicle's rear-view camera 100 who have favourited one on the trailer 110 attached target (the hitch angle detection component 155 ) maps, ie visually monitored, while the trailer 110 from the vehicle 100 is driven backwards. Alternatively, the hitch angle detection device 130 be a device that physically engages a coupling component of the vehicle 100 and / or a matching coupling component of the trailer 110 is mounted at an angle between the median longitudinal axes of the vehicle 100 or the trailer 110 to determine.

The power steering assist control module 135 the in 1 embodiment shown provides the trailer reversing Support control module 120 Information in connection with a rotational position (for example angle) of the steering wheel angle and / or a rotational position (for example one / more turning angles of the steered wheels) of the vehicle 100 . In certain embodiments, the trailer backup assist control module 120 an integrated part of the power steering assist system 115 be. The braking system control module 145 supplies the trailer backup assist control module 120 Information related to the vehicle speed. Such vehicle speed information can be determined from individual wheel speeds as viewed by the braking system control module 145 monitored, or can be supplied by a machine control module with signal plausibility. The vehicle speed can also be determined by an engine control module. In certain embodiments, the trailer backup assist control module 120 Vehicle braking information to the braking system control module 145 deliver it to the trailer backup assist control module 120 to enable braking of the vehicle 100 while the trailer is reversing 110 to control. The powertrain control module 150 can also be used with the trailer backup assist control module 120 to regulate the speed and acceleration of the vehicle 100 while the trailer is reversing 110 are in interaction.

2 Figure 3 shows one embodiment of the trailer reverse steering input device 125 from 1 . A rotatable control in the form of a button 120 is with a motion detection device 175 coupled. The button 170 is preloaded, for example, by a return spring to a rest position P (AR) between opposing rotational movement ranges R (R), R (L). A first one of the opposite rotational movement ranges R (R) is substantially equal to a second one of the opposite rotational movement ranges R (R), R (L). The motion detection device 175 is designed to be one movement of the button 170 and a corresponding signal (ie, motion detection device signal) to the trailer backup assist device 125 , this in 1 is shown to output. The motion detector signal is generated as a function of the rotation of the knob 170 with respect to the rest position P (AR) of rate movement of the button 170 and / or a direction of movement of the button 170 generated with respect to the rest position P (AR). The rest position P (AR) of the button 170 corresponds to a motion detection device signal indicating that the vehicle 100 should be steered in such a way that the trailer 110 is driven backwards along an essentially straight path (zero trailer curvature requirement on the part of the driver), such as from a center line longitudinal axis of the trailer 110 defined when the button 170 to the rest position P (AR) is returned, and a maximum clockwise and counterclockwise position of the button (i.e. limits of the opposite motion rotation ranges R (R), R (L)) each corresponds to a respective motion detection device signal that has a narrowest radius of curvature indicates (i.e. the sharpest path) a path of the trailer 110 which is possible without the corresponding vehicle steering information causing a lateral position condition. In this regard, the rest position P (AR) is a command position to zero curvature with respect to the opposite motion rotation ranges R (R), R (L).

Embodiments of the disclosure may also include a non-rotating control input device. Similar to a rotary control input device (e.g., the knob 170 and the associated motion detection device), such a non-rotating control input device is configured to selectively provide a signal that causes a trailer to follow a path segment that is substantially straight and selectively to provide a signal that causes the trailer to follow a Follow path segment that is essentially curved. Examples of such a non-rotating control input device include (without the invention being limited thereto), a plurality of pushbuttons, buttons (e.g. left turn, right turn and straight ahead), a touchscreen on which a driver draws a curve for route commands or otherwise inputs , a button that is slidable along an axis to allow the driver to input route commands, a joystick, the like.

In discussing a kinematic model that is used to calculate a relationship between a curvature of a path of a trailer and the steering angle of a vehicle towing the trailer, a low order kinematic model for a trailer backup assist system may be desirable, as shown in FIG some embodiments is designed. In order to provide such a kinematic model of low order, certain assumptions are made in connection with parameters belonging to the system of vehicle and trailer. Examples of such assumptions include, without the invention being limited thereto, reversing the trailer with the vehicle at a relatively low speed, negligible slip (e.g. no slip) of the tires of the vehicle and the trailer, negligible suspension (e.g. no side suspension) of the Tire of the vehicle, negligible (e.g. no) deformation of the tires of the vehicle and the trailer, negligible actuator dynamics of the vehicle, negligible roll or tilt movements of the vehicle and the trailer.

• δ: Lenkwinkel an gelenkten Vorderrädern 306 des Fahrzeugs 302,
• α: Gierwinkel des Fahrzeugs 302,
• β: Gierwinkel des Anhängers 304,
• γ: Kupplungswinkel (γ = β -α);
• W: Radstand des Fahrzeugs 302,
• L: Länge zwischen Kuppelstelle 308 und Hinterachse 310 des Fahrzeugs 302,
• D: Länge zwischen Kuppelstelle 308 und Achslänge 312 des Anhängers 304 (die Achslänge 312 kann eine effektive oder äquivalente Achslänge für einen Anhänger sein, der mehrere Achskonfigurationen hat), und
• r₂: Krümmungsradius für den Anhänger 304.

As in 3 shown, the kinematics model is based 300 for a system run by a vehicle 302 and a trailer 304 is defined on different parameters related to the vehicle 302 and the trailer 304 . These kinematic model parameters include:

• δ: steering angle on steered front wheels 306 of the vehicle 302 ,
• α: yaw angle of the vehicle 302 ,
• β: trailer yaw angle 304 ,
• γ: coupling angle (γ = β-α);
• W: wheelbase of the vehicle 302 ,
• L: length between coupling point 308 and rear axle 310 of the vehicle 302 ,
• D: length between coupling point 308 and axis length 312 of the trailer 304 (the axis length 312 can be an effective or equivalent axle length for a trailer that has multiple axle configurations), and
• r ₂ : radius of curvature for the trailer 304 .

The kinematics model 300 according to 3 shows a relationship between trailer path radius with curvature r ₂ at the middle 314 one axis 312 of the trailer 304 , Steering angle δ the steered wheels 306 of the vehicle 302 and coupling angle γ on. As shown in the equation below, this relationship can be expressed to provide trailer path curvature κ ₂ such that, if γ is given, the trailer path curvature κ ₂ based on the regulation of the steering angle δ can be controlled (where β̇ is the trailer _{yaw rate} and η _{̇ is} the trailer _speed ). $${\kappa }_2=\frac{1}{r_2}=\frac{\dot{\beta }}{\dot{\eta }}=\frac{\left(\mathrm{W.}+\frac{K{V}^2}{G}\right)\text{sin}\gamma +\mathrm{L.}\text{cos}\gamma \text{tan}\delta }{\mathrm{D.}\left(\left(\mathrm{W.}+\frac{K{V}^2}{G}\right)\text{cos}\gamma -\mathrm{L.}\text{sin}\gamma \text{tan}\delta \right)}$$

This relationship can now be expressed in terms of the steering angle δ as a function of the trailer path curvature κ ₂ and the coupling angle γ to provide. $$\delta ={\text{tan}}^{-1}\left(\frac{\left(\mathrm{W.}+\frac{K{V}^2}{G}\right)\left[{\kappa }_2\mathrm{D.}\text{cos}\gamma -\text{sin}\gamma \right]}{\mathrm{D.}\mathrm{L.}{\kappa }_2\text{sin}\gamma +\mathrm{L.}\text{cos}\gamma }\right)=\mathrm{F.}\left(\gamma ,{\kappa }_2,K\right)$$

The trailer path curvature κ ₂ is determined from the driver input via a trailer reversing steering input device. By using the equation for providing a steering angle, a corresponding steering command for controlling a steering system (for example its actuator) of the vehicle can be generated.

With further reference to 3 In one embodiment it may be desirable to increase the potential for the vehicle 302 and the trailer 304 to achieve a transverse position angle (ie to realize a transverse position state of the system composed of vehicle and trailer). A transverse position angle γ (j) relates to a coupling angle γ that cannot be overcome by the maximum steering input for a vehicle when reversing, such as the steered front wheels 306 of the vehicle 302 leading to a maximum steering angle δ moved at a maximum rate of change in the steering angle.

To control features of an embodiment of a trailer backup assist system 105 to implement, a driver must use the trailer backup system 105 interact with the trailer backup assistance system 105 to configure. The vehicle 100 may include a human machine interface (HMI) device 102 for implementing the trailer backup assist function through the interaction of the driver with the HMI device 102 be equipped. For example, the driver can have several HMI menus 104 presented via the HMI device 102 displayed with the HMI menus 104 support the driver through the modules that make up the trailer backup support system 105 set (setting module 600 ), calibrate (calibration module 700 ) and activate it. The trailer backup support system 105 guides a driver through the steps required to hook up a trailer, enter its dimensions (such as the horizontal distance from the rear of the vehicle to the center of the hitch ball), and check that the trailer is compatible and that the hitch angle sensor is operational.

As soon as the activity of the setting module 600 has completed 624, the calibration module begins 700 . The calibration module 700 is designed to calibrate the curvature control algorithm with the correct trailer measurements and to calibrate the trailer backup assist system for any possible hitch angle offset. After finishing the setting module 600 the calibration module begins 700 , and the driver will step in 702 instructed to pull the vehicle and trailer combination straight forward until one Hitch angle sensor calibration is complete. The HMI device 102 can use a pop-up or on-screen display to notify the driver that the vehicle and trailer combination must be pulled forward until calibration is complete. After the calibration has been completed (step 704 ), the HMI device can 102 inform the driver of this. Any hitch angle offset value is stored in memory, accessed by the curvature control algorithm, and the operation of the calibration module 700 ends. Various other methods of hitch angle calibration can also be used with the invention.

The trailer backup assist system of the vehicle may use a target placed on the trailer to act as a hitch angle sensing component 155 to serve. The trailer backup support system can then use information that is captured via image capture and processing for use in the hitch angle detection device 130 use according to one embodiment. According to other embodiments, the target object can be used to identify changing an attached trailer, connecting or disconnecting the trailer, and other trailer-related information. The target object is an identifiable visual target that is recorded in an image by the video imaging camera and processed via image processing. According to one embodiment, the target object can have a sticker that can be stuck to the trailer using an adhesive on one side, preferably within a target placement zone, so that the camera and the image processing can detect the target object and its position on the trailer in order to provide trailer-related information to determine such as the coupling angle between the trailer and the vehicle.

As above with reference to 4th and the interaction of a driver with the HMI device 102 mentioned, calibrates the calibration module 700 after completing the trailer setting module 600 in step 620 according to one embodiment, the curvature control algorithm with the appropriate trailer measurements, and calibrates the trailer backup assist system for any hitch angle offset that may be present. According to one embodiment, the calibration module 700 instruct the driver to pull the vehicle and trailer combination straight forward until a hitch angle sensor calibration is complete, which is communicated to the driver via the HMI device 102 can be reported. Depending on any failure resulting from the trailer mass or the potential inability of the vehicle to be pulled straight forward, here are additional and alternative embodiments of calibrating the trailer backup assist system 105 described.

With reference to 5 is the trailer backup support system 105 of the vehicle with the trailer backup assist control module 120 in communication with a sensor system 1200 and the trailer reverse steering input device 125 as part of the trailer reversing assistance system 105 illustrated. The trailer backup support system 105 according to the embodiment receives sensor information from one or more hitch angle sensors 1312 , a vehicle yaw rate sensor 1314 and a vehicle speed sensor 1316 , and can use other conceivable sensors on the vehicle 100 or the trailer 110 be in touch. The illustrated embodiment of the trailer backup assist system 105 is also associated with a vehicle transmission control device, for example 1318 , e.g. to receive the gear currently engaged, in connection. Also is the trailer backup assist control module 120 also in direct connection with the power steering support system 115 , which is a power steering assist control module 135 for data exchange with a steering angle detection device 140 and a power steering motor 1300 has to the steered wheels 1302 of the vehicle 100 to operate ( 6th ). The embodiment of the trailer backup assist control module 120 has a microprocessor 1304 to process one or more programs in a corresponding memory 1306 of the trailer backup assistance control module 120 are stored on. The memory 1306 has a hitch angle calibration program in one embodiment 1308 and an initiation program 1310 on. The trailer reverse assist control module 120 may be an independent dedicated control device or a common control device integrated with other control functions such as the sensor system 1200 , the trailer reverse steering input device or other systems of the vehicle.

As in 6th Shown is a schematic illustration of a combination of the vehicle 100 and trailers 110 superimposed on an XY coordinate system that shows kinematic variables and angles, including the steering angle δ, the trailer length D and the hitch angle γ, which are determined by the dynamics of the vehicle combination 100 and trailers 110 influenced and represented in kinematic equations, as similarly with reference to 3 discussed.

With reference to 7-8 is a method of estimating the current Coupling angle γ (a) between the vehicle 100 and the trailer 110 shown according to one embodiment. The method represents the acquisition of a measured hitch angle γ (m) with at least one hitch angle sensor 1312 ( 5 ) on the vehicle 100 and detecting a steering angle δ of the steered wheels 1302 ( 6th ) of the vehicle 100 ready. The method also provides reversing of the vehicle 100 and thereby determining an offset γ (o) between a measured hitch angle γ (m) and a current hitch angle γ (a) when the measured hitch angle γ (m) and the steering angle δ while the vehicle is reversing 100 essentially match.

According to 6th is the yaw rate of the vehicle 100 if the hitch angle γ and the steering angle δ are substantially constant, they are also substantially constant and equal to the yaw rate of the trailer 110 . This interaction is used to formulate kinematic equations that can be solved to determine the offset γ (o) between the measured hitch angle γ (m) and the current hitch angle γ (a). In particular, it gives the yaw rate of the vehicle 100 as seen from the vehicle yaw rate sensor 1314 ( 5 ) or any other conceivable onboard vehicle sensor that may be configured to sense yaw rate is measured using the following equation: $$\frac{d\alpha }{dt}=-\frac{\nu }{\mathrm{W.}}\text{tan}\delta$$

wobei

• δ der Lenkwinkel der Vorderräder ist,
• D die Entfernung von der Kupplung zu der Anhängerachse ist,
• W der Radstand des Fahrzeugs ist (Entfernung zwischen beiden Achsen),
• L die Entfernung von der Fahrzeughinterachse und der Kupplung ist, und
• γ der Kupplungswinkel ist.

Furthermore, the yaw rate of the trailer 110 can be represented with the following equation: $$\frac{d\beta }{dt}=\frac{\nu }{\mathrm{D.}}\text{sin}\gamma +\frac{\mathrm{L.}\nu }{\mathrm{D.}\mathrm{W.}}\text{cos}\gamma \text{tan}\delta$$

in which

• δ is the steering angle of the front wheels,
• D is the distance from the coupling to the trailer axle,
• W is the wheelbase of the vehicle (distance between both axles)
• L is the distance from the vehicle rear axle and the clutch, and
• γ is the coupling angle.

If therefore the yaw rate of the vehicle 100 and the trailer 110 become equal, the current hitch angle γ (a) is likely to be constant, so the desired hitch angle provided by the trailer reversing steering input device 125 such as the rotatable input control device described above shown in FIG 2 is shown, is provided is also constant. The desired hitch angle from the trailer reversing steering input device 125 received, for example, may be constant when the driver tries to pull the trailer 110 along a straight line with the vehicle 100 (i.e., zero curvature command) to reverse or when the driver inputs a maximum button angle command. The resulting constant coupling angle gives the following equation: $$c=a\text{cos}\gamma +b\text{sin}\gamma$$

This equation can be rewritten as follows: $$c=a\sqrt{1-{\text{sin}}^2\gamma }+b\text{sin}\gamma$$

wobei $$c=-\frac{1}{W}\text{tan}\delta ,b=\frac{1}{D},\text{und }a=\frac{L}{DW}\text{tan}\delta \text{ gilt}\text{.}$$

The above equation can also be solved with the quadratic equation that solves for the coupling angle γ. Then, if the hitch angle γ is broken down into a measured hitch angle γ (m) and an offset angle y (o), the equation can be rewritten as follows: $${\gamma }_O=\text{arcsin}\frac{bc\pm a\sqrt{b^2+a^2-c^2}}{b^2+a^2}-{\gamma }_m$$

in which $$c=-\frac{1}{\mathrm{W.}}\text{tan}\delta ,b=\frac{1}{\mathrm{D.}},\text{and}a=\frac{\mathrm{L.}}{\mathrm{D.}\mathrm{W.}}\text{tan}\delta \text{applies}\text{.}$$

The hitch angle offset γ (o) can therefore be used as a function of the length D of the trailer 110 , the wheelbase length W of the vehicle 100 and the distance L from a rear axle of the vehicle 100 to the trailer 110 , as in 6th can be determined while satisfying the conditions provided above for the use of such an equation. In particular, the terms generally include that the vehicle 100 and the trailer 110 drive backwards, and that the measured coupling angle γ (m) and the steering angle δ are constant during the backward movement for at least one time span threshold value or for a movement over a distance above a distance threshold value.

As in 7th illustrates, the calibration module processes 700 an embodiment of the hitch angle calibration program 1308 to provide the method according to the following steps. At step 1320 the system receives generally defined features of the vehicle 100 and the trailer 110 , including the trailer length D, the wheelbase length W of the vehicle 100 and the distance L from the rear axle of the vehicle to the coupling connection. These general characteristics are described because of the dimensions of the vehicle 100 and the trailer 100 preloaded or looked up in product specifications, and if these dimensions are not known or otherwise already determined by the system, they can be measured and stored in memory 1306 or other vehicle memory prior to operating the vehicle 100 with the trailer backup support system 105 can be entered. The hitch angle calibration program 1308 , this in 7th is shown at step 1322 also the confirmation that the vehicle is ready 100 reverses when the sensors of the sensor system 1200 already uninterrupted measurements of the vehicle's variables 100 and the trailer 110 record, tape. In particular, the system can confirm that the vehicle 100 using directional speed sensors, the gear position of the transmission control device 1318 , GPS inputs or other possible indicators of the direction of the vehicle 100 drives backwards.

At step 1324 leads the vehicle 100 the initiation program 1310 out to further confirm that the combination vehicle 100 and trailers 110 is in a state to determine the offset γ (o) between the measured hitch angle γ (m) and the current hitch angle γ (a). As in 8th shows one embodiment of the initiation program 1310 then determining a compensated steering wheel angle (step 1326 ), calculating a filtered steering wheel angle rate (step 1328 ) on, and at step 1330 determining whether the filtered steering wheel angle rate is less than a maximum allowable steering wheel angle rate for the offset calculation. The initiation program 1310 also takes the measured trailer angle γ (m) at step 1332 and computes a filtered temporal trailer angle rate at step 1334 . The initiation program 1310 then determined at step 1336 whether the filtered trailer angle rate is less than the maximum allowable trailer angle rate for determining the offset calculation. It also takes the initiation program 1310 the detected or otherwise calculated vehicle speed from step 1338 and further calculates at step 1340 a filtered vehicle speed. The filtered vehicle speed is then at step 1342 processed to determine if it is less than a maximum allowable vehicle speed for determining the offset calculation. If the conditions of the initiation program 1310 at step 1344 are met, the trailer backup assistance system allows 105 the continuation of the hitch angle calibration program to determine the offset γ (o).

With further reference to 7th when the initiation program 1310 is complete, the hitch angle calibration program determines at step 1346 whether the hitch angle rate and the steering angle rate are both substantially equal to zero or, in other words, whether the hitch angle and the steering angle are substantially constant. If the hitch angle rate and the steering angle rate are both not substantially equal to zero, the hitch angle calibration program runs 1308 continued to the initiation program 1310 at step 1324 and will be taking measurements with the sensor system 1200 continued until the hitch angle rate and the steering wheel angle rate are substantially zero. Once they are both substantially equal to zero, the hitch angle calibration program determines 1308 at step 1348 the current hitch angle rate based on the generally established characteristics of the vehicle 100 and the trailer 110 according to the above equations. With the current coupling angle γ (a), the coupling angle calibration program 1308 then the offset γ (o) between the current coupling angle γ (a) and the measured coupling angle γ (m) at step 1350 determine. After determining the offset γ (o), the calibration module and the trailer backup support system are complete 105 can continue operation.

In an additional embodiment of the hitch angle calibration program 1308 , as in 9 Illustrated is a method of calibrating the trailer backup assist system 105 for the trailer 110 that is on the vehicle 100 is attached, provided that the forward movement of the vehicle 100 essentially at a speed just above a speed threshold. The method also provides for detecting a yaw rate of the vehicle 100 and detecting a measured hitch angle γ (m) of the trailer 110 ready. The method further provides determining an angle rate based on the measured hitch angle γ (m), and then determining an offset γ (o) between the measured hitch angle γ (m) and the current hitch angle γ (a) if the yaw rate and Angular rate are essentially zero.

At the above with reference to 7th described embodiment of the hitch angle calibration program 1308 drives the vehicle 100 backwards, and such an embodiment is therefore designed for situations in which the vehicle 100 may not be able to drive forward far enough to use the trailer backup system 105 to calibrate. However, if there is room to move the vehicle forward 100 is available, an alternative method can be used to determine the offset γ (o) between the current hitch angle γ (a) and the measured hitch angle γ (m), which does not affect the precision of the measured or otherwise determined trailer geometry and dimensions falls back. In particular, the user can adjust the trailer 110 with the vehicle 100 in one embodiment instructed different dimensions of the trailer 110 , below to measure the trailer length D. The dimensions of the vehicle 100 can, however, with a higher degree of precision in assembling the vehicle 100 measured or otherwise in a precise manner to the trailer backup assist system 105 such as a look-up table provided by the vehicle manufacturer.

According to 9 starts at step 700 the trailer reversing support system 105 , the system for the trailer 110 that is on the vehicle 100 is attached to calibrate. At step 1352 the system receives the vehicle characteristics, including the dimensions of the vehicle 100 and the operational characteristics, such as the current gear of the transmission. At step 1354 the system then confirms that the vehicle is 100 moves forward while the sensors of the sensor system 1200 Record measurements and other readings. In particular, in this embodiment, the sensors used have a sensor for determining the vehicle yaw rate, such as an onboard yaw rate sensor 1314 or a separate sensor that is designed to measure the yaw rate of the vehicle 100 to determine. The sensors used in this embodiment of the hitch angle calibration program 1308 are used, also have at least one hitch angle sensor 1312 as above with reference to the sensor system 1200 described on.

With further reference to 9 , are the steered wheels 1302 of the vehicle 100 at step 1356 steered straight while the vehicle 100 drives forward. In one embodiment, the user can be directed to drive the vehicle 100 steer straight by manually steering the steering wheel. In an additional embodiment, the vehicle 100 automatically using the power steering assist system 115 be steered straight. In particular, the trailer backup support system 105 the steered wheels 1302 of the vehicle 100 using the power steering motor 1300 combined with the steering angle detection device 140 actuate.

Once the sensor readings are received and the vehicle 100 is steering and driving forward, the embodiment of the hitch angle calibration program goes 1308 then for processing an initiation program 1310 at step 1358 further. The initiation program 1310 of the present embodiment, similar to the initiation program described in 8th 3, calculate filtered values for steering wheel angle rate, hitch angle rate, and vehicle speed. Further, these filtered values can be compared to threshold values to ensure that the hitch angle calibration program is executed when vehicle conditions are acceptable for such a calculation. In particular, the filtered steering angle rate can be less than a maximum allowable steering angle rate, the trailer angle rate can be less than the maximum allowable trailer angle rate, and the filtered vehicle speed can be less than the maximum allowable vehicle speed, such as 16.0934km / h (= 10 mph), 24.1402 km / h (= 15 mph) or another conceivable speed threshold. If these or more or less conditions are met, the system can proceed to the following step of the hitch angle calibration program.

As in 9 determines the hitch angle calibration program 1308 in step 1360 whether the hitch angle rate and the yaw rate are both substantially zero. In particular, the determination of the reaching of a value of substantially equal to zero can be one or more combinations of the values at which the value is in close proximity to zero or the value is zero or is substantially zero during a predetermined period of time. The time increment can be proportional to the filtered vehicle speed, so that an increasing speed of the vehicle results in a decrease in the time increment of the measured coupling angle γ (m), and the steering angle must be essentially constant in order to determine the offset γ (o). The offset can also be determined when the measured hitch angle and the steering angle are essentially constant while the vehicle is in motion 100 and the trailer 110 Reverse a distance above a distance threshold, such as a distance greater than half a circumference of a steered wheel of the vehicle 100 or other conceivable distances. When the system determines that both values are substantially equal to zero, the system is at step 1362 then able to determine the current hitch angle γ (a) based on the vehicle characteristics. In one embodiment, the current hitch angle y (a) is equal to zero if the above conditions are met. However, some vehicle features, such as an offset coupling position, can result in the current coupling angle γ (a) deviating from zero and these conditions being met. At step 1364 the system then determines the offset y (o) between the current hitch angle γ (a) and the measured hitch angle γ (m) for operating the trailer backup support system 105 . At step 704 can use the trailer backup support system 105 again inform the driver that the calibration is complete and can store the hitch angle offset value in memory to use with the attached trailer 110 to be associated.

In 10 is an additional embodiment of the hitch angle calibration program 1308 illustrates the direction of movement or potential direction of movement of the vehicle 100 taken into account before a method for determining the offset γ (o) of the measured hitch angle γ (m) is selected. The direction of movement of the vehicle 100 can be based on the gear currently engaged, such as forward ("Drive") or reverse ("Reverse") in automatic transmissions. The potential direction of movement of the vehicle 100 however, it can be on the available space in front of or behind the combination vehicle 100 and trailers 110 based. At step 1366 if the vehicle is 100 Moved in either the forward or reverse direction, the system can determine if there is enough room for the vehicle 100 continues to drive in such a direction and the calibration of the trailer backup support system 105 to lock. If there is not enough room, the hitch angle calibration program 1308 of the illustrated embodiment instruct the driver to drive the vehicle 100 in the opposite or alternate direction, provided that there is enough room in either direction to complete the calibration. If the vehicle is 100 not moving, the system can therefore use the vehicle's preferred direction of movement 100 and the trailer 110 Determine to move in order to have enough space for the vehicle 100 the calibration of the trailer backup assistance system 105 concludes. At step 1368 the system can inform the driver for example through the HMI device 102 instruct you to drive either forwards or backwards as in the previous step 1366 certainly. Based on the direction the vehicle is heading 100 is instructed to drive, this embodiment of the hitch angle calibration program 1308 use one of two alternative methods to determine the current hitch angle y (a) to complete the calibration. Especially if the vehicle 100 at step 1370 drives forward, the system goes to ensure that the vehicle 100 is being steered (step 1372 ) continues while the vehicle yaw rate 100 (in step 1374 ) and the hitch angle rate (in step 1376 ) can be recorded. The detected hitch angle γ (m) is used by the system to calculate the hitch angle rate at step 1378 to determine and then to step 1380 proceed to determine if the hitch angle rate and the yaw rate of the vehicle 100 are substantially zero, similar to that described above with reference to FIG 9 disclosed embodiment method described. When the hitch angle rate and the yaw rate of the vehicle are substantially zero, the hitch angle calibration program may 1308 at step 1380 determine that the current hitch angle γ (a) is essentially equal to zero, which can then be used together with the measured hitch angle γ (m) to determine the offset γ (o) at step 1382 to determine.

Alternatively, if the vehicle 100 at step 1384 reverses or is instructed to reverse, the system goes as soon as the vehicle is 100 drives backwards to detect the steering angle δ of the vehicle 100 at step 1386 continues and records the coupling angle γ (m) at step 1388 , and then the hitch angle rate and the steering angle rate at step 1390 to determine. At step 1392 the system determines when both the hitch angle rate and the steering angle rate are substantially zero. When these two values are essentially zero, the hitch angle calibration program 1308 the offset y (o) of the measured hitch angle γ (m) based on the length D of the trailer 110 , the wheelbase length W of the vehicle 100 and the distance L from the rear axle of the vehicle 100 to the trailer 110 as generally in the embodiment of the hitch angle calibration program 1308 according to 7th and 8th set out, determine. At the in 10 disclosed embodiment, the calibration program begins as soon as the coupling angle offset at step 1382 was determined at step 704 and can, for example, inform the driver via the HMI device 102 or instruct some other similar announcement.

Claims (20)

Method for determining an offset (γ (o)) between a measured (γ (m)) and a current (γ (a)) coupling angle between a vehicle (100) and a trailer (110), the method comprising the following steps: • Detection of a measured coupling angle (γ (a)) with a coupling angle sensor (1312) provided on the vehicle (100); • detecting a steering angle (δ) of steered wheels of the vehicle (100), • reversing the vehicle (100); • determining when the measured coupling angle (γ (m)) and the steering angle (δ) are constant while the vehicle (100) is reversing; and • Determination of an offset (γ (o)) between the measured hitch angle (γ (m)) and the current hitch angle (γ (a)) if the measured hitch angle (γ (a)) and the steering angle (δ) while reversing of the vehicle (100) can be determined to be constant. Procedure according to Claim 1 , characterized in that the offset (γ (o)) as a function of a length (D), which corresponds to the distance from a coupling (308) to a trailer axle (312) of the trailer (304), a wheelbase length (W) of the vehicle (302) and a length (L) which corresponds to the distance between the coupling (308) and a rear axle (310) of the vehicle (302) is determined. Procedure according to Claim 1 or 2 , characterized in that it further comprises the step of: steering the reversing vehicle (100) with a servo motor (1300) to move the vehicle (100) and the trailer (110) from the current hitch angle (γ (a)) to a desired one To move the coupling angle. Procedure according to Claim 3 , characterized in that it further comprises the steps of: selecting the desired hitch angle between the vehicle (100) and the trailer (110) with a rotatable input control device (170), and steering the vehicle (100) backwards based on the measured hitch angle ( γ (m)), the offset (γ (o)) and the desired coupling angle. Procedure according to Claim 1 , characterized in that it further comprises the steps of: selecting a desired coupling angle which corresponds to a zero curvature, and steering the reversing vehicle (100) based on the offset (γ (o)) about the vehicle (100) and the To position trailers (110) together along a straight line. Procedure according to Claim 1 , characterized in that the hitch angle sensor (1312) has a video imaging camera which monitors a target object on the trailer (110) in order to continuously detect the measured hitch angle (γ (m)). Procedure according to Claim 1 , characterized in that the offset (γ (o)) is determined when the vehicle (100) maintains a speed that is greater than a speed threshold value for a time increment. Method for determining an offset (γ (o)) between a measured (γ (m)) and a current (γ (a)) coupling angle between a vehicle (100) and a trailer (110), the method comprising the following steps: • continuous recording of a measured coupling angle (γ (m)), • continuous detection of a steering angle (δ) of the vehicle (100); • Determining when the measured coupling angle and the steering angle are constant during backing of the vehicle (100) over a distance above a distance threshold value; • Determination of an offset (γ (o)) between the measured hitch angle (γ (m)) and the current hitch angle (γ (a)) if the measured hitch angle (γ (m)) and the steering angle (δ) during the over a distance above the distance threshold reversing of the vehicle (100) can be determined to be constant. Procedure according to Claim 8 characterized in that the vehicle (100) is reversing a distance above a distance threshold value if the vehicle (100) maintains a speed greater than a speed threshold value for an increment of time. Procedure according to Claim 9 , characterized in that at higher speed the time increment is reduced for which the measured coupling angle and the steering angle must be constant when determining the offset. Procedure according to Claim 8 , characterized in that it further comprises the step of: providing a length (D) which corresponds to the distance from a coupling (308) to a trailer axle (312) of the trailer (304), a wheelbase length (W) of the vehicle (302) and a length (L), which corresponds to the distance between the coupling (308) and a rear axle (310) of the vehicle (302), the offset with a control device based on the length (D), which corresponds to the distance from a coupling (308) corresponds to a trailer axle (312) of the trailer (304), the wheelbase length (W) of the vehicle (302) and the length (L), which corresponds to the distance between the coupling (308) and a rear axle (310) of the vehicle (302) is determined. Procedure according to Claim 8 , characterized in that the distance threshold is greater than half the circumference of a steered wheel of the vehicle (100). Procedure according to Claim 8 , characterized in that it further comprises the step of: steering the reversing vehicle (100) based on the offset (γ (o)) to the vehicle (100) and the trailer (110) from the measured coupling angle (γ (m)) to move to a desired coupling angle. Procedure according to Claim 13 characterized in that it further comprises the step of rotating an input controller (170) to select the desired hitch angle between the vehicle (100) and the trailer (110). Procedure according to Claim 8 characterized by further comprising the steps of: selecting a desired hitch angle that has substantially zero curvature; and steering the reversing vehicle (100) based on the offset (γ (o)) to position the vehicle (100) and the trailer (110) together along a straight line. Procedure according to Claim 8 , characterized in that the measured hitch angle (γ (m)) is continuously detected with a hitch sensor (1312) which has a video imaging camera which monitors the movement of a target object on the trailer (110). System for determining an offset between a measured (γ (m)) and a current coupling angle (γ (a)) between a vehicle (100) and a trailer (110), with: • a coupling angle sensor (1312) provided on the vehicle (100), which continuously detects a measured coupling angle (γ (m)), • a steering sensor which continuously detects a steering angle (δ) of the vehicle (100), and • a control device for determining an offset (γ (o)) between the measured coupling angle (γ (m)) and the current coupling angle (γ (a)) if the measured coupling angle (γ (m)) and the steering angle (δ) is determined to be constant while the vehicle (100) and trailer (110) are reversing. System according to Claim 17 , characterized in that the offset (γ (o)) as a function of a length (D), which corresponds to the distance from a coupling (308) to a trailer axle (312) of the trailer (304), a wheelbase length (W) of the vehicle (302) and a length (L) which corresponds to the distance between the coupling (308) and a rear axle (310) of the vehicle (302) is determined. System according to Claim 18 , characterized in that the offset (γ (o)) is determined when the vehicle (100) and the trailer (110) maintain a constant yaw rate. System according to Claim 18 , characterized in that the offset (γ (o)) is determined when the vehicle (100) and the trailer (110) reverse over a distance above the distance threshold value, while the measured hitch angle (γ (m)) and the steering angle Keep (δ) constant.

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