Motor vehicle with front axle steering, rear axle steering and a driver assistance system

Abstract

To provide a motor vehicle with front-axle steering and rear-axle steering, with which a driving behavior with a lateral movement component generated during cornering by setting a front steering angle and a rear steering angle can be easily controlled by a human driver, a motor vehicle (100) with front-axle steering (10), rear-axle steering (11) and a steering wheel (14), further comprising a, preferably first, driver assistance system (15) comprising a data processing device (16), is proposed, wherein the data processing device (16) is configured, when the driver assistance system (15) is switched on, to calculate a trajectory (17) depending on a steering instruction and, depending on the trajectory (17), to set a front steering angle (18) of the front-axle steering (10) and a rear steering angle (19) of the rear-axle steering (11) such thatthat the motor vehicle (100) follows the trajectory (17), furthermore provided that, while the motor vehicle (100) follows the trajectory (17), a steering wheel angle (20) of the steering wheel (14) is decoupled from the front steering angle (18) such that the steering wheel angle (20) corresponds to the trajectory (17).

Description

[0001] The present invention relates to a motor vehicle with a front-axle steering system, a rear-axle steering system, and a steering wheel, further comprising a, preferably first, driver assistance system comprising a data processing device. When the driver assistance system is switched on, the data processing device is configured to calculate a trajectory as a function of a steering instruction and, as a function of the trajectory, to adjust a front steering angle of the front-axle steering system and a rear steering angle of the rear-axle steering system such that the motor vehicle follows the trajectory. Furthermore, the present invention relates to a computer program product for a driver assistance system.

[0002] In automatically or autonomously driving motor vehicles that have rear-axle steering, the rear-axle steering can be used to make cornering particularly comfortable for the vehicle occupants. In this way, the rear-axle steering can enable the vehicle to handle with minimal force impulses in the longitudinal and / or transverse directions. With large steering angles of the rear-axle steering, it can happen that the vehicle exhibits a lateral movement component transverse to its longitudinal axis when cornering and thus drifts through the curve to a certain extent. In order for the vehicle to continue to follow the curve despite this lateral drift, the steering angle of the front-axle steering must be adjusted accordingly. With particularly large steering angles of the rear-axle steering, the steering angle of the front-axle steering can then even be set in the same direction as the rear steering angle.Controlling such driving behavior is no problem for an automated or autonomous vehicle. However, the aforementioned drift condition is difficult for a human driver to manage, since the steering wheel, which indicates the steering angle of the front axle steering, is turned in the opposite direction to the curve. For example, in a left-hand bend, the steering wheel has a steering angle for a right-hand bend.

[0003] WO 2014 / 106559 A1 discloses a drift training assistance system for a motor vehicle for learning the drifting required in highly dynamic driving training (e.g. in a circle), wherein both the steering action and the accelerator pedal movement or their combined action are taken over and / or supported by at least one drift assistance system.

[0004] DE 10 2018 105 598 A1 discloses methods and systems for operating a powertrain of a hybrid vehicle. The torque output from the internal combustion engine and the electric motor is adjusted to provide controlled vehicle sideslip while a vehicle is cornering.

[0005] It is an object of the present invention to provide a motor vehicle with a front axle steering system and a rear axle steering system, with which a driving behavior with a lateral movement component generated during cornering by adjusting a front steering angle and a rear steering angle can be easily controlled by a human driver.

[0006] To achieve the object underlying the invention, a motor vehicle with a front axle steering system, a rear axle steering system and a steering wheel is proposed, wherein the motor vehicle further comprises a, preferably first, driver assistance system comprising a data processing device, wherein the data processing device is configured, when the driver assistance system is switched on, to calculate a trajectory as a function of a steering instruction and, as a function of the trajectory, to set a front steering angle of the front axle steering system and a rear steering angle of the rear axle steering system in such a way that the motor vehicle follows the trajectory, wherein it is further provided that, while the motor vehicle follows the trajectory, a steering wheel angle of the steering wheel is decoupled from the front steering angle in such a way that the steering wheel angle corresponds to the trajectory.

[0007] In the context of the present invention, a steering instruction can be understood, in the simplest case, as an indicator that simply indicates that a change of direction of the motor vehicle must be made, or that no change of direction is necessary. Optionally, the steering instruction can additionally contain the information that the change of direction should be to the left or right.

[0008] Furthermore, the steering instruction can also be more specific and include information about the parameters of the direction change. For example, the steering instruction can include information about the radius of curvature of a curve intended for the direction change, or information about the time at which the direction change should occur.

[0009] The data processing device thus receives a steering instruction and uses this steering instruction to calculate a trajectory that the motor vehicle should follow. The trajectory can, for example, be a trajectory for cornering. Depending on the calculated trajectory, the data processing device instructs the front-axle steering and the rear-axle steering systems to adjust a front steering angle of the front-axle steering system and a rear steering angle of the rear-axle steering system such that the motor vehicle follows the trajectory.

[0010] If the rear steering angle is particularly large, driving situations can arise in which the front steering angle of the front axle steering does not appear to correspond to the desired trajectory. In certain driving situations, the front steering angle and the rear steering angle may even be set in the same direction while the vehicle is following the trajectory. For example, when driving through a left-hand bend, the front steering angle relative to a longitudinal axis of the vehicle may be set to correspond to a right-hand bend. This front steering angle to the right is then compensated for by the larger rear steering angle, which is also directed to the right, so that the vehicle follows the left-hand bend. This can be confusing for the driver, as a steering wheel angle corresponding to the front steering angle would correspond to a steering instruction to the right, even though the vehicle is moving along a trajectory for a left-hand bend.The same applies in reverse when driving through a right-hand bend.

[0011] According to the invention, it is therefore provided that, while the motor vehicle follows the trajectory, a steering wheel angle of the steering wheel is decoupled from the front steering angle in such a way that the steering wheel angle corresponds to the trajectory, that is to say in particular that the steering wheel angle is adjusted to match the trajectory.

[0012] In the above-described case, in which the front steering angle and the rear steering angle are set in the same direction, but a trajectory that appears to contradict the front steering angle due to a rear steering angle that is greater than the front steering angle, the invention thus makes it possible for the steering wheel angle to be opposite to the actual front steering angle and / or to have a different value, so that from the driver's perspective, the steering wheel angle continues to correspond to the trajectory traversed by the motor vehicle. In other words, from the driver's perspective, the steering wheel angle and the trajectory correspond, even though the front steering angle appears to deviate from the trajectory with respect to the longitudinal axis of the motor vehicle.This avoids irritation for the driver and makes drifting behavior caused by simultaneous adjustment of front axle steering and rear axle steering, especially when cornering, manageable for the driver.

[0013] It is preferably provided that the data processing device is configured to adjust the steering wheel angle of the steering wheel independently of at least the front steering angle such that the steering wheel angle corresponds to the trajectory.

[0014] In other words, the data processing device can actively and independently adjust the steering wheel angle such that the steering wheel angle from the driver's perspective corresponds to the calculated trajectory.

[0015] Preferably, the trajectory is a curve.

[0016] The data processing device can adjust the front steering angle of the front axle steering and the rear steering angle of the rear axle steering even before reaching the curve. This causes the vehicle to rotate or angle itself, so to speak, before cornering begins, making the transition into cornering, especially into drifting behavior during cornering, even more comfortable for the driver.

[0017] It can be further advantageously provided that the steering instruction is generated by the driver assistance system or by a second driver assistance system, in particular an active lane keeping assistant or a lane centering assistant.

[0018] Modern motor vehicles incorporate systems for road edge detection or driving corridor detection. Such systems are typically sensor-based and may include cameras, lidar, or radar sensors. If the steering instruction is generated by the driver assistance system itself, the driver assistance system receives data from the road edge detection system and / or the driving corridor detection system. The data may include information about the road edges and / or the space provided and available by a driving corridor. The driver assistance system, in particular the data processing device, then independently generates the steering instruction. The data processing device also calculates the trajectory based on the steering instruction and / or the data from the road edge detection system and / or the data from the driving corridor detection system.

[0019] If the steering instruction is generated by an active lane keeping assistant or a lane centering assistant, the vehicle follows the trajectory via an active steering system. The driver assistance system or the data processing device of the driver assistance system then actively adjusts the steering wheel angle so that, from the driver's perspective, the steering wheel angle corresponds to the trajectory. For the driver, the steering wheel angle thus corresponds to the vehicle's usual behavior. If the driver wishes to take control of the vehicle during assisted driving by the active lane keeping assistant or the lane centering assistant, the steering wheel is already pointing in the direction corresponding to the trajectory and expected by the driver. The driver can therefore easily initiate the transition from assisted driving to driver-controlled driving.

[0020] The second driver assistance system, in particular the lane keeping assistant or the lane centering assistant, can be integrated into the first driver assistance system or represent a subfunction of the first driver assistance system. However, it is fundamentally possible for two driver assistance systems to be involved, with the second driver assistance system, in particular designed as an active lane keeping assistant or a lane centering assistant, serving to transmit the steering instruction to the first driver assistance system provided according to the invention.

[0021] If the steering instruction is generated by a second driver assistance system, in particular an active lane keeping assistant or a lane centering assistant, it can be provided that the steering instruction has already been created by the second driver assistance system based on the data from the lane edge detection system and / or the data from the driving corridor detection system. In this case, the data processing device receives only the steering instruction and calculates the trajectory on this basis. Alternatively or additionally, it is also possible for the data processing device to receive data from the lane edge detection system and / or the driving corridor detection system in addition to the steering instruction.The data processing device can then include in the calculation of the trajectory not only the steering instruction received from the second driver assistance system but also the data from the road edge detection system and / or the data from the driving corridor detection system.

[0022] In principle, it is also possible for the steering instruction to be generated by a driver inputting the steering wheel.

[0023] In other words, the driver sets a steering wheel angle that corresponds to a desired trajectory of the motor vehicle, for example, cornering. The driver assistance system receives this steering instruction, and the data processing device of the driver assistance system converts this steering instruction into a front steering angle for the front-axle steering and a rear steering angle for the rear-axle steering. Depending on how the rear steering angle is set by the data processing device, a deviation between the front steering angle and the steering wheel angle may occur. However, since the steering wheel angle is decoupled from the front steering angle in such a way that the steering wheel angle continues to correspond to the trajectory, this apparently deviating front steering angle is not noticeable to the driver.

[0024] If the steering instruction is generated by a driver input into the steering wheel, it is particularly advantageous if the driver assistance system receives data from the lane edge detection system and / or from the driving corridor detection system.

[0025] Preferably, the data processing device additionally determines the trajectory based on map information. The map information can be provided, for example, by a navigation device. This enables a predictive calculation of the trajectory.

[0026] With further advantage, it can be provided that the front axle steering is a superimposed steering system or a steer-by-wire steering system.

[0027] Using a superimposed steering system or a steer-by-wire steering system, the decoupling of the steering wheel angle and the front steering angle can be achieved in a particularly advantageous manner. In particular, with a steer-by-wire steering system, the data processing device can control the steering wheel of the motor vehicle, independent of the front steering angle selected for the trajectory, such that the steering wheel assumes a steering angle that corresponds to the trajectory. The steering wheel angle is thus largely independent of the front steering angle. With a superimposed steering system, the steering wheel angle can be adjusted by superimposing the front steering angle with a superimposed angle.

[0028] With further advantage, the rear axle steering can be provided as a steer-by-wire steering system.

[0029] It can preferably be provided that the data processing device is configured to adjust the front steering angle and the rear steering angle in the same direction, wherein the rear steering angle is greater than the front steering angle, so that the motor vehicle follows the trajectory, wherein the trajectory is preferably a curve.

[0030] The rear steering angle being larger than the front steering angle usually only occurs in wide corners, as the rear steering angle can only be adjusted up to 5°. In tighter corners, the front steering angle will generally be larger than the rear steering angle.

[0031] In this case, it can particularly preferably be provided that the motor vehicle has a longitudinal axis, and that the motor vehicle, while the motor vehicle follows the trajectory, moves laterally to the longitudinal axis.

[0032] In the example of negotiating a left-hand bend explained above, it may happen that, if the rear steering angle is set particularly large, the front steering angle must be adjusted in the same direction so that the vehicle follows the left-hand bend. With respect to the vehicle's longitudinal axis, the front steering angle then exhibits a steering angle to the right during the bend. This results in the vehicle moving laterally relative to its longitudinal axis while following the trajectory, i.e., the bend.

[0033] It is preferably provided that the data processing device is configured to detect, in particular as a function of a steering input and / or an accelerator pedal input and / or a brake pedal input, that the driver intends to take control of the motor vehicle and / or that the driver intends to deactivate the driver assistance system, wherein the data processing device is further preferably configured to reduce the rear steering angle and to adjust the front steering angle such that the motor vehicle continues to follow the trajectory.

[0034] This is particularly advantageous when the steering instruction is generated by the driver assistance system itself or by a second driver assistance system, particularly one designed as an active lane keeping assistant. In this case, the driver may wish to regain control of the vehicle. For example, the driver can press the accelerator or brake pedal or move the steering wheel. This allows the data processing device to recognize that the driver wishes to deactivate the driver assistance system or take control of the vehicle.

[0035] The data processing device can then be provided to reduce the rear steering angle so that the motor vehicle largely returns to normal driving behavior, as is known from the prior art. Reducing the rear steering angle requires an adjustment of the front steering angle, as otherwise the motor vehicle would deviate from the trajectory. In other words, the rear steering angle and the front steering angle are continuously changed without the motor vehicle deviating from the trajectory.

[0036] During this transition phase, the steering wheel angle remains decoupled from the front steering angle in such a way that it corresponds to the trajectory regardless of the currently set front steering angle. For this purpose, the data processing device can be configured to actively adjust the steering wheel angle.

[0037] A further solution to the problem underlying the invention consists in a computer program product for a driver assistance system, comprising instructions which, when executed on a data processing device of a previously described motor vehicle, cause the data processing device to calculate a trajectory as a function of a steering instruction and, as a function of the trajectory, to set a front steering angle of the front axle steering and a rear steering angle of the rear axle steering such that the motor vehicle follows the trajectory, and to set a steering wheel angle of the steering wheel independently of at least the front steering angle such that the steering wheel angle corresponds to the trajectory.

[0038] In particular, the instructions may cause the data processing device to adjust the front steering angle and the rear steering angle in the same direction, wherein the rear steering angle is greater than the front steering angle, so that the motor vehicle follows the trajectory, wherein the trajectory is preferably a curve.

[0039] The invention is explained in more detail below with reference to the accompanying figures. They show: Fig. 1 a schematic representation of a motor vehicle with a front axle steering and a rear axle steering, Fig. 2 a motor vehicle constructed in accordance with the invention driving through a curve, Fig. 3 a motor vehicle not constructed in accordance with the invention driving through the curve, and Fig. 4 the motor vehicle constructed in accordance with the invention when a driver takes over control of the vehicle.

[0040] Fig. 1 schematically shows a motor vehicle 100 with a front-axle steering system 10 and a rear-axle steering system 11 in accordance with the invention. The front-axle steering system 10 comprises two front wheels 12. Accordingly, the rear-axle steering system 11 has two rear wheels 13. The motor vehicle 100 further comprises a steering wheel 14. Furthermore, the motor vehicle 100 comprises a driver assistance system 15 with a data processing device 16.

[0041] In Fig. 2, the motor vehicle 100 is shown negotiating a curve 24. The data processing device 16 is configured to calculate a trajectory 17 for negotiating the curve 24 as a function of a steering instruction and, as a function of the trajectory 17, to set a front steering angle 18 of the front-axle steering system 10 and a rear steering angle 19 of the rear-axle steering system 11 such that the motor vehicle 100 follows the trajectory 17. The data processing device 16 is also configured to set a steering wheel angle 20 of the steering wheel 14 independently of at least the front steering angle 18 such that the steering wheel angle 20 corresponds to the trajectory 17.

[0042] For comparison, Fig. 3 a case in which the data processing device 16 is not configured to adjust the steering wheel angle 20 of the steering wheel 14 independently of the front steering angle 18. In Fig. In the case illustrated in Figure 3, the driver assistance system 15 or a second driver assistance system 21, which is preferably embodied as an active lane keeping assistant 22, generated a steering instruction corresponding to cornering to the left. The data processing device 16 calculates a planned trajectory 17 based on this steering instruction. Furthermore, the data processing device sets the front steering angle 18 of the front-axle steering system 10 and the rear steering angle 19 of the rear-axle steering system 11 such that the motor vehicle 100 follows the trajectory 17. The rear steering angle 19 is selected to be so large that it must be at least partially compensated for by the front steering angle 18. As a result, the front steering angle 18 and the rear steering angle 20 are set in the same direction, and the front steering angle 18 corresponds to a steering angle to the right with respect to a longitudinal axis 23 of the motor vehicle 100.To ensure that the motor vehicle 100 nevertheless follows the trajectory 17, the rear steering angle 19 is significantly greater than the front steering angle 18. At the steering angles 18, 19 shown, the motor vehicle 100 has a movement component transverse to the longitudinal axis 23 and, in a sense, "drifts" around the curve 24. Since the data processing device 16 is not configured to adjust the steering angle 20 of the steering wheel 14 independently of the front steering angle 18, from the driver's perspective, the steering angle 20 also corresponds to a steering angle to the right. Such a situation is very irritating for the driver.

[0043] Returning to Fig. 2, the data processing device 16 is configured in accordance with the invention to adjust the steering wheel angle 20 of the steering wheel 14 independently of the front steering angle 18 such that the steering wheel angle 20 corresponds to the trajectory 17. The steering wheel angle 20 determined by the data processing device 16 according to Fig. The steering wheel angle 20 set in Figure 2 corresponds to a left-hand steering angle, although the front steering angle 18 with respect to the longitudinal axis 23 of the motor vehicle 100 corresponds to a right-hand steering angle. From the driver's perspective, the usual driving behavior of the motor vehicle 100 is thus established, and the steering wheel angle 20 does not irritate the driver.

[0044] Fig. Figure 4 shows a case where the driver, starting from the situation in Fig. 2 through active steering intervention 26 in the steering wheel 14, the driver wishes to take control of the motor vehicle 100 and follow a desired trajectory 25 that deviates from the calculated trajectory 17. The data processing device 16 detects that the driver wishes to take control. In order to make the transition from cornering controlled by the driver assistance system 15 to cornering controlled by the driver safe for the driver, the data processing device 16 reduces the rear steering angle 19, preferably to 0°, and simultaneously adjusts the front steering angle 18 such that the motor vehicle 100 follows the desired trajectory 25. This adjustment takes place continuously, so that the driver does not notice the transition and the usual driving behavior of the motor vehicle 100 quickly sets in. The position of the front wheels 12 and the rear wheels 13 after the adjustment has been made is shown with dashed lines in Fig. 4 shown. List of reference symbols 100 motor vehicles 10 Front axle steering 11 Rear-axle steering 12 front wheel 13 Rear wheel 14 Steering wheel 15 Driver assistance system 16 Data processing device 17 Trajectory 18 Front steering angle 19 Rear steering angle 20 steering wheel angle 21 Second driver assistance system 22 Active Lane Keeping Assist 23 Longitudinal axis 24 Curve 25 Desired trajectory 26 Active steering intervention QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2014 / 106559 A1

[0003] DE 10 2018 105 598 A1

[0004]

Claims

[1] Motor vehicle (100) with a front-axle steering system (10), a rear-axle steering system (11) and a steering wheel (14), further comprising a, preferably first, driver assistance system (15) comprising a data processing device (16), wherein the data processing device (16) is configured, when the driver assistance system (15) is switched on, to calculate a trajectory (17) as a function of a steering instruction and, as a function of the trajectory (17), to set a front steering angle (18) of the front-axle steering system (10) and a rear steering angle (19) of the rear-axle steering system (11) such that the motor vehicle (100) follows the trajectory (17), characterized by that, while the motor vehicle (100) follows the trajectory (17), a steering wheel angle (20) of the steering wheel (14) is decoupled from the front steering angle (18) such that the steering wheel angle (20) corresponds to the trajectory (17). [2] Motor vehicle (100) according to claim 1, characterized bythat the data processing device (16) is configured to adjust the steering wheel angle (20) of the steering wheel (14) independently of at least the front steering angle (18) such that the steering wheel angle (20) corresponds to the trajectory (17). [3] Motor vehicle (100) according to claim 1 or 2, characterized by that the trajectory (17) is a curve (24). [4] Motor vehicle (100) according to one of the preceding claims, characterized by that the steering instruction is generated by the driver assistance system (15). [5] Motor vehicle (100) according to one of the preceding claims, characterized by that the steering instruction is generated by a second driver assistance system (21). [6] Motor vehicle (100) according to claim 5, characterized by that the second driver assistance system (21) is an active lane keeping assistant (22) or a lane centering assistant. [7] Motor vehicle (100) according to one of the preceding claims, characterized bythat the steering instruction is given by a steering input from a driver into the steering wheel (14). [8] Motor vehicle (100) according to one of the preceding claims, characterized by that the front axle steering (10) is a superimposed steering system or a steer-by-wire steering system. [9] Motor vehicle (100) according to one of the preceding claims, characterized by that the rear axle steering (11) is a steer-by-wire steering system. [10] Motor vehicle (100) according to one of the preceding claims, characterized by in that the data processing device (16) is designed to set the front steering angle (18) and the rear steering angle (19) in the same direction, wherein the rear steering angle (19) is greater than the front steering angle (18), so that the motor vehicle (100) follows the trajectory (17), wherein the trajectory (17) is preferably a curve (24). [11] Motor vehicle (100) according to one of the preceding claims, characterized bythat the motor vehicle (100) has a longitudinal axis (23), and that the motor vehicle (100) moves laterally to the longitudinal axis (23) while the motor vehicle (100) follows the trajectory (17). [12] Motor vehicle (100) according to one of the preceding claims, characterized by that the data processing device (16) is configured to detect, in particular as a function of a steering input and / or an accelerator pedal input and / or a brake pedal input, that the driver intends to take control of the motor vehicle (100) and / or that the driver intends to switch off the driver assistance system (15). [13] Motor vehicle (100) according to claim 12, characterized by in that the data processing device (16) is configured to reduce the rear steering angle (19) and to adjust the front steering angle (18) such that the motor vehicle (100) continues to follow the trajectory (17). [14] Computer program product for a driver assistance system (15), comprising instructions which, when executed on a data processing device of a motor vehicle (100) according to one of the preceding claims, cause the data processing device (16) to calculate a trajectory (17) as a function of a steering instruction and, as a function of the trajectory (17), to set a front steering angle (18) of the front-axle steering (10) and a rear steering angle (19) of the rear-axle steering (11) such that the motor vehicle (100) follows the trajectory (17), and to set a steering wheel angle (20) of the steering wheel (14) independently of at least the front steering angle (18) such that the steering wheel angle (20) corresponds to the trajectory (17). [15] Computer program product according to claim 14, wherein the instructions cause the data processing device (16) to set the front steering angle (18) and the rear steering angle (19) in the same direction, wherein the rear steering angle (19) is greater than the front steering angle (18), so that the motor vehicle (100) follows the trajectory (17), wherein the trajectory (17) is preferably a curve (24).

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