Method for maneuvering a vehicle combination consisting of a vehicle and a trailer

Abstract

The invention relates to a method for maneuvering a vehicle combination (3) comprising a vehicle (1) and a trailer (2). According to the invention, a control and / or regulation of a trailer articulation angle of the trailer (2) is carried out by means of a rear axle steering system (4) of the vehicle (1) as a function of a steering wheel angle (LRW) of the vehicle (1).

Description

The invention relates to a method for maneuvering a vehicle combination comprising a vehicle and a trailer according to the preamble of claim 1. A trailer reversing aid control system is known from the prior art, as described in US 2014 / 0229070 A1. A trailer reversing aid system for a vehicle coupled with a trailer comprises a parking assist control unit configured to receive a distance input from a rear distance sensor and, based on this input, determine a swivel angle of the trailer relative to the vehicle. An electronic power steering system is coupled to the parking assist control unit and configured to adjust the vehicle's steering angle based on the swivel angle of the trailer. US Patent 2020 / 0001920 A1 describes systems and methods for preventing a jackknife effect in a tractor-trailer system. The described systems and methods determine a maneuvering range beyond which the jackknife effect is unavoidable due to the steering capabilities of the tractor. The described systems and methods include a plug-in safety controller that protects against a loss of maneuverability of the tractor-trailer system. US patent 2024 / 0308589 A1 describes a trailer assistance system to support the reversing maneuver of a trailer attached to a vehicle.The trailer assist system determines a reverse path to an end position for the vehicle and trailer, determines a trailer angle for the trailer relative to the vehicle, selects a target waypoint along the reverse path, determines an offset between a current position and orientation of the trailer and a target position and orientation of the trailer associated with the target waypoint, determines a target trailer angle based on the offset between the current position and orientation of the trailer and the target position and orientation of the trailer, determines an offset between the trailer angle and the target trailer angle, determines a steering angle based on the offset, and controls the vehicle's steering based on the steering angle while the vehicle is reversing. From the generic patent DE 10 2008 004 158 A1, a stabilizing device for stabilizing a towing vehicle with a trailer while reversing is known. A stabilizing steering angle is set on a rear axle of the towing vehicle to reduce the difference between the actual drawbar angle and a corresponding angle calculated from the steering angle of the front wheels. If the required stabilizing steering angle reaches a maximum limit, this is communicated to the driver via a communication device. DE 10 2006 059 082 A1 discloses a method for performing a steering maneuver in a vehicle with a trailer, which also has a front axle and a rear axle steering system. In this method, a target articulation angle is determined as a function of a steering wheel angle and the vehicle's geometric dimensions. The rear axle steering angle is then adjusted, taking into account a measured actual articulation angle and the calculated target articulation angle, to compensate for any difference between the two angles. It is proposed to measure the actual articulation angle while reversing and to calculate it while driving forward. German patent DE 10 2014 005 681 A1 describes a driver assistance system in which the image from a reversing camera is superimposed on a graphic display. This display visualizes one or more angle values ​​for the driver, such as the current articulation angle, a maximum articulation angle, or a target articulation angle, as perspectively correct directions or directional ranges. If a maximum articulation angle is exceeded during reversing, at which point a collision is imminent, the system suggests braking the vehicle to a standstill as a safety precaution. The drawbar length can be manually entered to adapt to different trailers. The invention is based on the objective of providing a method for maneuvering a vehicle combination comprising a vehicle and a trailer that is improved compared to the prior art. The problem is solved according to the invention by a method for maneuvering a vehicle combination comprising a vehicle and a trailer with the features of claim 1. According to the invention, the trailer articulation angle is controlled and regulated. The method is particularly characterized by the fact that, in a selection step, a trailer type is first chosen in order to access parameters stored for that type. Furthermore, the regulation function is used as the primary function and the control function as a fallback solution, to which the system switches when predefined limit values ​​are reached. Advantageous embodiments of the invention are the subject of the dependent claims. In a method according to the invention for maneuvering a vehicle combination comprising a vehicle and a trailer, in particular during reversing, alternatively or additionally, for example, also during forward driving, a control and regulation of a trailer articulation angle of the trailer is carried out by means of a rear axle steering system of the vehicle as a function of a steering wheel angle of the vehicle. The steering wheel angle is determined, for example, by a driver of the vehicle, i.e., by turning the vehicle's steering wheel, or it is determined, for example, by an automated, in particular highly automated, or autonomous assistance function of the vehicle. The trailer articulation angle is an angle of the trailer's orientation relative to the vehicle's orientation, particularly in a plane containing the vehicle's longitudinal and transverse axes. The trailer articulation angle is thus specifically a pivot angle of the trailer about a pivot axis running parallel to the vehicle's vertical axis, which in particular passes through a trailer coupling head, especially a trailer coupling ball, of the vehicle's trailer hitch. The process is carried out, in particular, in a processing unit of the vehicle. Specifically, the necessary calculations are performed in this processing unit. This processing unit is therefore specifically designed and configured to carry out the process. The processing unit is, for example, a control unit for the rear axle steering. The described solution makes driving with a trailer easier, as this is always a challenge for the average inexperienced driver, especially when reversing. In particular, the driver needs skill to move the trailer in the desired direction or to stabilize it by steering so that it doesn't drift in an unwanted direction. Previously known trailer assistance functions that support driving with a trailer relate to driver assistance via the vehicle's front-axle steering or control of the front-axle steering angle during autonomous parking. Rear-axle steering, and in particular a degree of freedom of rear-axle steering, is not used for this purpose. Specifically, it has not been previously possible to use the rear-axle steering specifically to control and / or regulate the trailer's articulation angle. This is now provided for in the solution described here, for which the rear-axle steering is specifically controlled and / or regulated accordingly, particularly in a manner that deviates from a normal rear-axle steering function, where it is, for example, only controlled and / or regulated depending on vehicle speed, whether the vehicle is traveling forward or in reverse, and the steering wheel angle.In contrast to the standard function of rear-axle steering, the solution described here advantageously operates the rear-axle steering system based on an actual trailer articulation angle and / or a target trailer articulation angle. The actual trailer articulation angle is the currently observed trailer articulation angle, which is determined, in particular, by means of a reversing camera on the vehicle, and the target trailer articulation angle is the trailer articulation angle that is to be achieved by the control and / or regulation of the rear-axle steering system. This is particularly advantageous because the rear axle steering provides suitable support, especially when reversing with a trailer, since the rear axle steering is installed in a more suitable position than the front axle steering in terms of distance to the trailer and the vehicle's center of gravity for aligning the trailer. The solution described here enables, in particular, the control and / or regulation of the rear axle steering in such a way as to stabilize the trailer and allow for intuitive trailer steering. Especially when reversing with a trailer, and particularly when driving straight ahead, the trailer can fishtail. This is compensated for by the solution described here, specifically by controlling and / or regulating the trailer articulation angle via the rear axle steering, so that the vehicle always follows the steering wheel angle and does not fishtail. To steer the trailer while reversing, it was previously necessary to first steer in the opposite direction to align the trailer correctly. For example, a steering wheel angle to the right was required to align the trailer to the left, or vice versa. The solution described here makes this more intuitive for the driver, because by controlling and / or regulating the trailer's articulation angle via the rear axle steering, the trailer is immediately moved in the intended direction determined by the steering wheel angle. That is, if the steering wheel angle is turned to the right, the trailer immediately moves to the right, and if the steering wheel angle is turned to the left, the trailer immediately moves to the left. The method according to the invention is divided into two process steps: the control and regulation of the trailer articulation angle, also referred to as the trailer maneuvering assistance function, and a trailer selection function. That is, the trailer selection function precedes the described control and regulation of the trailer articulation angle. In particular, it is provided that parameters for several different trailer types are stored in the processing unit, for example, in the control unit of the rear axle steering. The driver of the vehicle is offered a selection of the trailer types and, after selecting a trailer type corresponding to the trailer connected to the vehicle, the parameters stored for this trailer type are used for the process. The trailer selection function also advantageously offers the driver the option of first activating the trailer assistance, i.e., the trailer maneuvering assistance function. For example, the activation option is displayed to the driver on a display unit in the vehicle. This display unit is, for example, a touch-sensitive display, i.e., in particular, a corresponding screen in the vehicle. For example, after activation, the driver is offered a choice of three or more trailer types, such as bicycle trailers, standard trailers, and caravans. The driver then selects the trailer type that corresponds to, or is at least most similar to, the trailer connected to the vehicle. Based on this selection, the corresponding parameters stored in the trailer maneuvering assistance function are then used. The trailer maneuvering assistance function is then performed, in such a way that the trailer articulation angle is controlled and regulated via the rear axle steering so that the trailer moves in the desired direction, in particular as specified by the steering wheel angle. The system comprises a control unit and a regulation unit. The primary function of the regulation unit is to adjust the rear axle steering angle. Under predefined conditions, the control unit acts as a fallback, i.e., it takes over from the regulation unit if the regulation unit reaches its limit or if the difference between the target trailer articulation angle and the actual trailer articulation angle is too large. For example, the coordination between the control unit and the regulation unit can be configured, and in particular, individually adjustable, for instance, adapted to the vehicle and / or the trailer currently attached to the vehicle. It is specifically intended that the trailer articulation angle control is implemented as a map-based control system, which outputs a target rear axle steering angle as a control unit signal. The steering wheel angle and the actual trailer articulation angle are used as input signals for this control system. This trailer articulation angle control is thus based on a map that outputs the target rear axle steering angle. This target rear axle steering angle is determined by the steering wheel angle and the actual trailer articulation angle as input signals. It is therefore a function of the steering wheel angle and the actual trailer articulation angle (target rear axle steering angle = f(steering wheel angle, actual trailer articulation angle)). For example, this target rear axle steering angle can be individually parameterized for the vehicle and / or for different trailer types. It is specifically provided that the trailer articulation angle is controlled based on a steering wheel angle map and / or a front wheel steering angle map, with the steering wheel angle and / or front wheel steering angle as the input signal and the target trailer articulation angle as the output signal. It is specifically provided that a gradient of the target trailer articulation angle is limited by a steering wheel angular velocity. It is specifically provided that a difference between the target trailer articulation angle and the actual trailer articulation angle is fed to a trailer angle controller, whereby the trailer angle controller regulates a rear axle target steering angle such that the actual trailer articulation angle corresponds to the target trailer articulation angle, i.e., such that the difference between the target trailer articulation angle and the actual trailer articulation angle becomes zero.The trailer angle controller uses additional input signals such as vehicle speed and / or wheel speeds. Specifically, a trailer target angle feedforward control system calculates a rear axle target steering angle based on the target trailer articulation angle or the actual trailer articulation angle, specifically as the product of the target trailer articulation angle or the actual trailer articulation angle multiplied by a factor (predefined rear axle target steering angle = factor * (target trailer articulation angle or actual trailer articulation angle)). This control of the trailer articulation angle constitutes the main operating mode of the trailer maneuvering assistance function. The control system includes, in particular, a map-based setpoint calculation as described above, a gradient limitation as described above, the trailer angle controller, and the trailer target angle feedforward control. The target trailer articulation angle is calculated using a characteristic map based on the steering wheel angle and / or the front wheel steering angle as input. The target trailer articulation angle is therefore a function of the steering wheel angle and / or the front wheel steering angle. The steering wheel angle and the front wheel steering angle can be substituted for each other, as they are related via the vehicle's front axle steering; that is, the front wheel steering angle depends on the steering wheel angle. This characteristic map can also be advantageously set / parameterized individually for the vehicle or for different vehicle variants and / or for different trailer types. Further input signals for calculating the target trailer articulation angle are also possible, in particular additional input signals for the characteristic map. Advantageously, the gradient of the target trailer articulation angle is subsequently limited via the steering wheel angle speed, so that rapid changes in the steering wheel angle are not immediately passed on to the control of the rear axle steering angle, in particular the rear axle target steering angle of the control system. After calculating the target trailer articulation angle, it is to be adjusted via the rear axle steering. For this purpose, a trailer angle controller with trailer target angle feedforward is used. The trailer angle controller is specifically a PID controller, in particular a standard PID controller. As mentioned above, the actual trailer articulation angle is advantageously determined via the vehicle's reversing camera and, in particular, provided to the processing unit, especially the rear axle steering control unit, via a vehicle bus. The trailer angle controller then uses the rear axle target steering angle as a control variable to regulate the difference between the calculated target trailer articulation angle and the measured actual trailer articulation angle to zero, so that the trailer advantageously follows the calculated target trailer articulation angle. To support the trailer angle controller, the trailer target angle feedforward control is also implemented, which calculates the rear axle target steering angle of the feedforward control on the basis of the target trailer articulation angle or the actual trailer articulation angle, in particular as the product of the target trailer articulation angle or the actual trailer articulation angle multiplied by a factor, in particular a specified one. The primary goal of trailer steering angle pre-control is to enhance the dynamics of the control system and the stabilizing effects of the rear axle steering (where the rear axle steering angle has the same sign as the front axle steering angle). Furthermore, the system allows, for example, the trailer steering angle pre-control to be dependent on the steering wheel angular velocity. A rear axle steering angle limiter is provided, which switches from the regulation of the trailer articulation angle to the control of the trailer articulation angle when a maximum trailer articulation angle is reached and / or when the difference between the target trailer articulation angle and the actual trailer articulation angle increases. The rear axle steering angle limiter limits the rear axle steering angle, in particular the target rear axle steering angle, specifically the target rear axle steering angle set by the control system, in such a way that it does not increase the error of the trailer articulation angle, i.e., the difference between the target trailer articulation angle and the actual trailer articulation angle, or reach or exceed the maximum trailer articulation angle, for example, 45°. This is particularly relevant because a maximum rear axle steering angle is not infinitely large, but is, for example, 10° or 4.5°; i.e., a larger rear axle steering angle is not possible due to the design. If, for example, the control system is at its limit, i.e., the maximum rear axle steering angle has been reached and / or the trailer angle controller is in saturation, and the error, i.e.,If the difference between the target trailer articulation angle and the actual trailer articulation angle increases over time instead of decreasing, the rear axle steering angle limiter reacts and switches from regulating the trailer articulation angle to controlling the trailer articulation angle. This switch from trailer articulation angle control to trailer articulation angle control also occurs when the maximum trailer articulation angle, particularly the adjustable one, is reached. In this case, the control system is unable to maintain the desired articulation angle, i.e., the target trailer articulation angle. This can lead to a situation where the rear axle steering angle is in an unfavorable direction. For example, the rear axle steering angle may have the same sign as the front axle steering angle. Therefore, switching from trailer articulation angle control to trailer articulation angle control is necessary to ensure greater vehicle maneuverability. Switching between trailer articulation angle regulation and trailer articulation angle control is primarily managed via a coordination block. For this purpose, the coordination block advantageously receives corresponding limiter information from the rear axle steering angle limiter. This limiter information from the rear axle steering angle limiter can also be, for example, another input signal for the trailer angle controller. The coordination block advantageously also receives the rear axle target steering angle of the control system, the difference between the target trailer articulation angle and the actual trailer articulation angle, and a sum of the rear axle target steering angle of the control system and the rear axle target steering angle of the feedforward control system. The rear axle steering angle limiter advantageously receives from the coordination block the rear axle target steering angle of the control system, the difference between the target trailer articulation angle and the actual trailer articulation angle, and the sum of the rear axle target steering angle of the control system and the rear axle target steering angle of the feedforward control system. The rear axle steering angle limiter also advantageously receives the actual trailer articulation angle and the maximum trailer articulation angle. The trailer articulation angle control system is a so-called fallback solution. If the articulation angle error (i.e., the difference between the target and actual trailer articulation angles) becomes too large, or if the rear axle steering angle limiter intervenes, the system switches from trailer articulation angle regulation to trailer articulation angle control. As a result, a rear axle steering angle is provided to the rear axle steering system, in particular by the rear axle steering angle limiter and / or the coordination block. This rear axle steering angle is based in particular on the rear axle steering angle set by the control unit when, in particular according to the decision of the coordination block, the trailer articulation angle is controlled, and in particular on the sum of the rear axle steering angle set by the control unit and the rear axle steering angle set by the feedforward control unit when, in particular according to the decision of the coordination block, the trailer articulation angle is controlled. Based on this, the rear axle steering on the vehicle, more precisely on its rear axle, advantageously sets the corresponding rear wheel steering angle. The front wheel steering angle is advantageously set according to the steering wheel angle on the front axle of the vehicle. It is specifically designed that the steering wheel angle is converted into the front wheel steering angle using a steering ratio, which is particularly configurable. This makes the described solution independent of the specific steering gear used. It is specifically intended that the trailer maneuvering assistance function, or at least its control of the trailer articulation angle, is only active when reversing. For example, it is intended that the control of the trailer articulation angle is deactivated when driving forward, but the trailer articulation angle control itself remains active. This is configured accordingly, for example, by the coordination block. To carry out the procedure, the vehicle or a corresponding vehicle system, designed and configured for this purpose, includes in particular the processing unit described above, such as the rear axle steering control unit, and also, in particular, the reversing camera, which records the actual trailer articulation angle with sufficient accuracy and cycle time. The reversing camera is thus designed and configured accordingly. The calculation and evaluation of the actual trailer articulation angle takes place, for example, in a control unit responsible for implementing an automated, in particular highly automated, or autonomous parking function (ADAS) of the vehicle, and / or, for example, in the processing unit.The actual trailer articulation angle is then provided to the processing unit, in particular the rear axle steering control unit, via the vehicle bus. Alternatively, the calculation and evaluation of the actual trailer articulation angle can be carried out directly in the processing unit, for example in the rear axle steering control unit. To carry out the procedure, the vehicle or its system also features rear-axle steering, in particular with the control unit on which the described function is advantageously implemented, especially the trailer maneuvering assistance function and, advantageously, also the trailer selection function. The rear-axle steering is designed and configured in such a way that it can establish a sufficiently large rear-axle steering angle. Advantageously, the vehicle or its system also features trailer detection, which recognizes when the vehicle is connected to a trailer. Advantageously, the described trailer selection function is also provided, which allows the driver to select from several, for example three, different trailer types the one that corresponds to, or at least most closely resembles, the trailer connected to the vehicle, as described above. In one embodiment, the target trailer articulation angle and the actual trailer articulation angle are also displayed on the vehicle's display unit, particularly together with the reversing camera image. This makes it more intuitive for the driver to understand how to adjust the target trailer articulation angle via the steering wheel angle. Exemplary embodiments of the invention are explained in more detail below with reference to drawings. Figure 1 schematically shows a vehicle combination with a vehicle and trailer, and Figure 2 schematically shows a control and / or regulation structure of a method for maneuvering the vehicle combination. Corresponding parts are marked with the same reference symbols in all figures. With reference to Figures 1 and 2, a method for maneuvering a vehicle combination 3 comprising a vehicle 1 and a trailer 2, particularly during reversing, is described below. Figure 1 shows a schematic representation of the vehicle combination 3, and Figure 2 shows a control structure used for the method. Figure 1 shows the direction of a vehicle speed v of vehicle 1 forward or backward, the front wheel steering angle VRW of front wheels VR of a front axle VA and the rear wheel steering angle HRW of rear wheels HR of a rear axle HA of vehicle 1, as well as an actual trailer articulation angle IAW. The method provides, in particular, that a rear axle steering system 4 of the vehicle 1 is used to control and regulate the articulation angle of the trailer 2 as a function of a steering wheel angle LRW of the vehicle 1. The articulation angle of the trailer 2 is an angle of orientation relative to an orientation of the vehicle 1, in particular in a plane in which a longitudinal axis and a transverse axis of the vehicle 1 lie. The articulation angle of the trailer 2 is thus, in particular, a pivot angle of the trailer 2 about a pivot axis running parallel to a vertical axis of the vehicle 1. The process is carried out, in particular, in a processing unit of vehicle 1. Specifically, the necessary calculations are performed in this processing unit. The processing unit is, for example, a control unit for the rear axle steering 4. In the solution described here, the rear axle steering 4 is specifically used to control and regulate the articulation angle of the trailer 2, for which the rear axle steering 4 is controlled and regulated accordingly, particularly deviating from its normal function. In contrast to this normal function, the rear axle steering 4 in the solution described here is advantageously operated as a function of the actual trailer articulation angle IAW and a target trailer articulation angle SAW. The actual trailer articulation angle (IAW) is a currently observed trailer articulation angle, which is determined, in particular, by means of a trailer articulation angle detection system 5, specifically by means of a reversing camera of the vehicle 1. The trailer articulation angle detection system 5 provides the actual trailer articulation angle (IAW) and, for example, additionally a permissible range of the trailer articulation angle and thus, in particular, a maximum trailer articulation angle (MAW). Additional information can also be provided by the trailer articulation angle detection system 5. The target trailer articulation angle SAW is a trailer articulation angle that is to be achieved by controlling and regulating the rear axle steering 4. In the illustrated embodiment of the method, a division into two basic functions is provided: the control and regulation of the trailer articulation angle of trailer 2, also referred to as trailer maneuvering assistance function 6, and a trailer selection function 7. Advantageously, the trailer selection function 7 is integrated upstream of the described control and regulation of the trailer articulation angle. In particular, it is provided that parameters for several different trailer types are stored in the processing unit, for example, in the control unit of the rear axle steering 4. The driver of the vehicle 1 is offered a selection of the trailer types, and after selecting a trailer type corresponding to the trailer 2 connected to the vehicle 1, the parameters stored for this trailer type are used for the method. The trailer selection function 7 also advantageously offers the driver the option of first activating the support function for trailer operation, i.e., the trailer maneuvering assistance function 6. For example, the activation option is displayed to the driver in a display unit in vehicle 1. The display unit is, for example, a touch-sensitive display unit, i.e., in particular a corresponding display in vehicle 1. For example, after activation, the driver is offered a choice of three or more trailer types, such as bicycle trailers, standard trailers, and caravans. The driver then selects the trailer type that corresponds to, or is most similar to, the trailer 2 connected to vehicle 1. Based on this selection, the corresponding parameters stored in the trailer maneuvering assistance function 6 are then used. In the trailer selection function 7, the function activation 8 and the trailer type selection 9 are thus carried out in the example shown via the, in particular touch-sensitive, display unit of the vehicle 1, and via the, in particular touch-sensitive, display unit of the vehicle 1. Subsequently, the trailer maneuvering assistance function 6 is performed, such that the trailer articulation angle of the trailer 2 is controlled and regulated via the rear axle steering 4 so that the trailer 2 moves in the desired direction, in particular specified by the steering wheel angle LRW. The system comprises a control unit and a regulation unit. The regulation unit is designed to adjust the rear axle steering angle. It is intended that the control unit takes over under predefined conditions, i.e., it performs this function instead of the regulation unit. This occurs when the regulation unit reaches its limit or when the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW, also known as articulation angle error, is too large. For example, the coordination between the control unit and the regulation unit can be adjusted, and in particular, individually adjustable, for example, adapted to vehicle 1 and / or to the trailer 2 connected to vehicle 1. It is specifically intended that the trailer articulation angle control is implemented as a map-based control unit 10, which outputs a rear axle target steering angle (SLWS) as a control unit signal. The steering wheel angle (LRW) and the actual trailer articulation angle (IAW) are used as input signals for the map-based control unit 10. This trailer articulation angle control is thus based, in particular, on a map that outputs the rear axle target steering angle (SLWS) to the control unit. This rear axle target steering angle (SLWS) is determined by the input signals steering wheel angle (LRW) and actual trailer articulation angle (IAW). It is therefore, in particular, a function of steering wheel angle (LRW) and actual trailer articulation angle (IAW). For example, this rear axle target steering angle (SLWS) can be individually parameterized for vehicle 1 and / or for the trailer types. It is specifically provided that the trailer articulation angle is controlled based on a steering wheel angle map and / or a front wheel steering angle map, with the steering wheel angle LRW and / or front wheel steering angle VRW as the input signal and the target trailer articulation angle SAW as the output signal. It is specifically provided that a gradient of the target trailer articulation angle SAW is limited by a steering wheel angular velocity LRWG. It is specifically provided that the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW is fed to a trailer angle controller 11, wherein the trailer angle controller 11 controls a rear axle target steering angle SLWR such that the actual trailer articulation angle IAW corresponds to the target trailer articulation angle SAW, i.e., such that the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW becomes zero.The trailer angle controller 11 uses, for example, the vehicle speed v and / or wheel speeds n of the vehicle 1 as further input signals. In particular, it is provided that a rear axle target steering angle SLWVS of the feedforward control is calculated by means of a trailer target angle feedforward control 12 based on the target trailer articulation angle SAW or on the actual trailer articulation angle IAW, in particular as the product of the target trailer articulation angle SAW or the actual trailer articulation angle IAW multiplied by a factor, in particular a predetermined one. This control of the trailer articulation angle constitutes the main operating mode of the trailer maneuvering assistance function 6. The control includes, in particular, a map-based setpoint calculation 13 as described above, a gradient limitation 14 as described above, the trailer angle controller 11, and the trailer setpoint angle feedforward control 12. The target trailer articulation angle (SAW) is calculated using a characteristic map based on the steering wheel angle (LRW) and / or the front wheel steering angle (VRW) as input. The target trailer articulation angle (SAW) is therefore a function of the steering wheel angle (LRW) and / or the front wheel steering angle (VRW). This characteristic map is also advantageously adjustable / parameterizable for vehicle 1, for different vehicle variants, and / or for different trailer types. Additional input signals for calculating the target trailer articulation angle (SAW), in particular further input signals for the characteristic map, are also possible. Advantageously, the gradient of the target trailer articulation angle SAW is subsequently limited via the steering wheel angle speed LRWG, so that rapid changes in the steering wheel angle LRW are not immediately passed on to the control of the rear axle steering angle, in particular the rear axle target steering angle SLWR of the control system. After calculating the target trailer articulation angle SAW, this is to be controlled via the rear axle steering 4. For this purpose, the trailer angle controller 11 with trailer target angle feedforward control 12 is used. The trailer angle controller 11 is, in particular, a PID controller, specifically a standard PID controller. The actual trailer articulation angle (IAW) is advantageously determined via the reversing camera of vehicle 1, as mentioned above, and is provided to the processing unit, in particular the control unit of the rear axle steering 4, via a vehicle bus 15 of vehicle 1. For example, further sensor data from vehicle sensors 16 of vehicle 1, such as vehicle dynamics data, can also be provided via the vehicle bus 15. The trailer angle controller 11 then regulates the difference D between the calculated target trailer articulation angle SAW and the detected actual trailer articulation angle IAW to zero via the rear axle target steering angle SLWR of the control system as a manipulated variable, so that the trailer 2 advantageously follows the calculated target trailer articulation angle SAW. To support the trailer angle controller 11, the trailer target angle feedforward control 12 is also implemented, which calculates the rear axle target steering angle SLWVS of the feedforward control on the basis of the target trailer articulation angle SAW or the actual trailer articulation angle IAW, in particular as the product of the target trailer articulation angle SAW or the actual trailer articulation angle IAW multiplied by a factor, in particular a specified one. The aim of the trailer target angle feedforward control 12 is, in particular, to increase the dynamics of the control system as well as the stabilizing components of the rear axle steering 4 (rear axle steering angle has the same sign as the front axle steering angle). Furthermore, for example, a dependency of the trailer target angle feedforward control 12 on the steering wheel angular velocity LRWG is provided. A rear axle steering angle limiter 17 is provided, which switches from the regulation of the trailer articulation angle to the control of the trailer articulation angle when the maximum trailer articulation angle MAW is reached, i.e. when the actual trailer articulation angle IAW reaches the maximum trailer articulation angle MAW, and / or when the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW increases. The rear axle steering angle limiter 17 limits the rear axle steering angle, in particular the rear axle target steering angle, especially the rear axle target steering angle SLWR of the control system, such that it does not increase the error of the trailer articulation angle, i.e., the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW, or reach or exceed the maximum trailer articulation angle MAW, for example, 45°. This is particularly relevant because a maximum rear axle steering angle is not infinitely large, but is, for example, 10° or 4.5°. If, for example, the control system is at its limit, i.e., the maximum rear axle steering angle MAW is reached and / or the trailer angle controller 11 is in saturation, and the error, i.e.,If the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW increases over time and does not decrease, then the rear axle steering angle limiter 17 reacts and switches from the regulation of the trailer articulation angle to the control of the trailer articulation angle. This switch from trailer articulation angle control to trailer articulation angle steering also occurs when the maximum trailer articulation angle (MAW), which is particularly adjustable, is reached. In this case, the control system is unable to regulate the desired articulation angle, i.e., the target trailer articulation angle (SAW). This can lead to a situation where the rear axle steering angle is in an unfavorable direction. For example, the rear axle steering angle may have the same sign as the front axle steering angle. Therefore, switching from trailer articulation angle control to trailer articulation angle steering is necessary to ensure greater maneuverability of the vehicle. The switching between trailer articulation angle regulation and trailer articulation angle control is primarily regulated via a coordination block 18. For this purpose, the coordination block 18 receives a corresponding limiter information BI from the rear axle steering angle limiter 17. This limiter information BI from the rear axle steering angle limiter 17 is, for example, also another input signal to the trailer angle controller 11. The coordination block 18 advantageously also receives the rear axle target steering angle SLWS of the control system, the difference D between target trailer articulation angle SAW and actual trailer articulation angle IAW and a sum of the rear axle target steering angle SLWR of the control system and the rear axle target steering angle SLWVS of the feedforward control system. The rear axle steering angle limiter 17 advantageously receives from the coordination block 18 the rear axle target steering angle SLWS of the control, the difference D between target trailer articulation angle SAW and actual trailer articulation angle IAW and the sum of the rear axle target steering angle SLWR of the control and the rear axle target steering angle SLWVS of the feedforward control. The rear axle steering angle limiter 17 also advantageously receives the actual trailer articulation angle IAW and the maximum trailer articulation angle MAW. The trailer articulation angle control represents a so-called fallback solution. For example, if the articulation angle error, i.e., the difference D between the target trailer articulation angle SAW and the actual trailer articulation angle IAW, becomes too large, or if the rear axle steering angle limiter 17 intervenes, then the system switches from trailer articulation angle regulation to trailer articulation angle control. As a result, a rear axle steering angle SHRW is provided to the rear axle steering 4, in particular by the rear axle steering angle limiter 17 and / or the coordination block 18. This rear axle steering angle SHRW is based in particular on the rear axle steering angle SLWS of the control unit when, in particular according to the decision of the coordination block 18, the control of the trailer articulation angle is carried out, and in particular on the sum of the rear axle steering angle SLWR of the control unit and the rear axle steering angle SLWVS of the feedforward control unit when, in particular according to the decision of the coordination block 18, the control of the trailer articulation angle is carried out. Based on this, the rear axle steering 4 on vehicle 1, more precisely on its rear axle HA, sets the corresponding rear wheel steering angle HRW. The front wheel steering angle VRW is set in particular according to the steering wheel angle LRW on the front axle VA of vehicle 1. It is specifically intended that the steering wheel angle LRW is converted into the front wheel steering angle VRW using a steering ratio, which is particularly configurable. This makes the described solution independent of the specific steering gear used. It is specifically intended that the trailer maneuvering assistance function 6, or at least its control of the trailer articulation angle, is only active when reversing. For example, it is intended that the control of the trailer articulation angle is deactivated when driving forward, but the trailer articulation angle control remains active even when driving forward. This is configured accordingly, for example, by coordination block 18. To carry out the procedure, the vehicle 1 or a corresponding system of the vehicle 1, which is designed and configured for carrying out the procedure, includes in particular the processing unit described above, for example, the control unit of the rear axle steering 4, and also, in particular, the reversing camera, which records the actual trailer articulation angle IAW of the trailer 2, especially with sufficient accuracy and cycle time. The reversing camera is thus designed and configured accordingly. The calculation and evaluation of the actual trailer articulation angle IAW takes place, for example, in a control unit responsible for implementing an automated, in particular highly automated, or autonomous parking function (ADAS) of the vehicle 1, and / or, for example, in the processing unit.The actual trailer articulation angle (IAW) is then provided to the processing unit, in particular the rear axle steering control unit 4, via the vehicle bus 15. Alternatively, the calculation and evaluation of the actual trailer articulation angle (IAW) can be carried out directly in the processing unit, for example in the rear axle steering control unit 4. The vehicle 1 or its system also has, for carrying out the procedure, the rear axle steering 4, in particular with the control unit on which the described function is advantageously implemented, in particular the trailer maneuvering assistance function 6 and advantageously also the trailer selection function 7. The rear axle steering 4 is in particular designed and configured such that it can establish a sufficiently large rear axle steering angle. Advantageously, the vehicle 1 or its system also has a trailer recognition function, which detects when the vehicle 1 is connected to a trailer 2. Advantageously, the described trailer selection function 7 is also provided, which allows the driver to select from several, for example three, different trailer types the one that corresponds to or at least most closely resembles the trailer 2 connected to the vehicle 1, as described above. In the illustrated embodiment, a display function 19 is also provided, by means of which the target trailer articulation angle SAW and, for example, the actual trailer articulation angle IAW are displayed on the display unit in the vehicle 1, in particular together with the reversing camera image captured by the reversing camera. In this way, it is more intuitive for the driver to see how to set the target trailer articulation angle SAW via the steering wheel angle LRW.

Claims

Method for maneuvering a vehicle combination (3) comprising a vehicle (1) and a trailer (2), in which a control and regulation of the trailer articulation angle of the trailer (2) is carried out by means of a rear axle steering system (4) of the vehicle (1) as a function of a steering wheel angle (LRW) of the vehicle (1), characterized in that in a selection step preceding the control and regulation of the trailer articulation angle, a driver of the vehicle (1) is offered several trailer types to choose from and, after the selection, parameters stored for the selected trailer type are used for the subsequent control and regulation of the trailer articulation angle, and that the regulation of the trailer articulation angle is carried out as the basic function and the control of the trailer articulation angle is activated as a fallback function.when a difference (D) between a target trailer articulation angle (SAW) and an actual trailer articulation angle (IAW) exceeds a predefined limit value or a rear axle angle limiter (17) engages. Method according to claim 1, characterized in that the control of the trailer articulation angle is carried out as a map control (10) which outputs a rear axle target steering angle (SLWS) of the control as an output signal, wherein the steering wheel angle (LRW) and an actual trailer articulation angle (IAW) are used as input signals of the map control (10). Method according to one of the preceding claims, characterized in that the control of the trailer articulation angle is carried out on the basis of a steering wheel angle characteristic map with the steering wheel angle (LRW) as input signal and a target trailer articulation angle (SAW) as output signal. Method according to claim 3, characterized in that a gradient of the target trailer articulation angle (SAW) is limited via a steering wheel angular velocity (LRWG). Method according to claim 3 or 4, characterized in that a difference (D) of the target trailer articulation angle (SAW) and an actual trailer articulation angle (IAW) is supplied to a trailer angle controller (11), wherein the trailer angle controller (11) regulates a rear axle target steering angle (SLWR) of the control such that the actual trailer articulation angle (IAW) corresponds to the target trailer articulation angle (SAW). Method according to one of claims 3 to 5, characterized in that a rear axle target steering angle (SLWVS) of the control is calculated by a trailer target angle feedforward control (12) based on the target trailer articulation angle (SAW) or on the actual trailer articulation angle (IAW). Method according to one of claims 2 to 6, characterized in that the actual trailer articulation angle (IAW) is determined by means of a reversing camera of the vehicle (1). Method according to one of claims 3 to 7, characterized in that the target trailer articulation angle (SAW) and the actual trailer articulation angle (IAW) are displayed on a display unit in the vehicle (1).

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