Device and method for adjusting a distance between an ego vehicle and a preceding vehicle

Abstract

Device (12) for adjusting a distance between an ego vehicle (10) and a preceding vehicle (14), comprising: - an input interface (20) for receiving sensor data from an environmental sensor (16) with information about a roadway (18) in an area in front of the ego vehicle, a predetermined distance of a driver assistance system (34) and a current following distance of a following vehicle (28); - an evaluation unit (22) for determining a friction value of the road in the area in front of the ego vehicle and a road topology of the road (18) in the area in front of the ego vehicle (10) based on the sensor data; - an adaptation unit (24) for determining an adjusted distance based on the predetermined distance, the determined friction coefficient, the road surface topology and the current following distance; and - an output interface (26) for transmitting the adjusted distance to the driver assistance system.

Description

[0001] The present invention relates to a device for adjusting a distance between an ego vehicle and a vehicle traveling ahead, as well as a corresponding method. The present invention further relates to a driver assistance system for controlling a distance between an ego vehicle and a vehicle traveling ahead, as well as to an ego vehicle.

[0002] Modern vehicles (cars, vans, trucks, motorcycles, etc.) incorporate a multitude of systems that provide the driver with information and control individual vehicle functions partially or fully automatically. Sensors monitor the vehicle's surroundings and other road users. Based on the recorded data, a model of the vehicle's environment can be created and changes in this environment can be responded to. Due to the ongoing development of autonomous and semi-autonomous vehicles, the influence and scope of such advanced driver assistance systems (ADAS) are becoming ever larger. The development of increasingly precise sensors makes it possible to monitor the environment and traffic and to control individual vehicle functions completely or partially without driver intervention.Driver assistance systems can particularly contribute to increasing road safety and improving driving comfort.

[0003] A relevant functional area of driver assistance systems concerns the automatic control of a vehicle's speed. So-called adaptive cruise control (ACA) systems support the driver with acceleration and braking, maintaining speed and distance, lane guidance (for example, in speed ranges from 0 to 250 km / h), and in traffic jams. Cruise control allows the driver to maintain a preset speed without the driver having to actively accelerate or brake. So-called adaptive cruise control (ACC) systems are based on maintaining a constant preset or situation-dependent distance from a vehicle ahead. The speed of the vehicle ahead is adapted, and the vehicle ahead is essentially tracked.

[0004] One problem here can be that a safe distance from a vehicle ahead, i.e., a distance that allows sufficient time for emergency braking or another reaction, depends on a large number of different parameters. For example, a distance to a vehicle ahead may be chosen such that the ego vehicle has enough time to apply the brakes, but this makes a rear-end collision with a following vehicle unavoidable. This is particularly problematic if, in retrospect, a lower braking force would have been sufficient to avoid an accident with the vehicle ahead.

[0005] In this context, DE 199 33 782 A1 relates to a method for avoiding rear-end collisions and a device for carrying out the method. The method is based on observing the traffic area behind a first motor vehicle. The method involves determining the speed of the first motor vehicle, determining the relative speed between the first motor vehicle and a second motor vehicle located behind the first motor vehicle, determining the distance between the first and second motor vehicles, calculating the time remaining until the two vehicles would collide with each other, taking into account a predetermined value for the deceleration of the second motor vehicle, and triggering an action on the first motor vehicle if the calculated time is below a predetermined value.

[0006] DE 10 2013 013 242 A1 relates to a driver assistance system for longitudinal control of a vehicle with respect to a third-party vehicle, preferably for speed and / or distance control. Furthermore, an operating method for a driver assistance system for longitudinal control of a vehicle is disclosed, wherein a changing angle of incidence of a third-party vehicle approaching from the side or from the rear is incorporated into the longitudinal control.

[0007] DE 10 2014 215 274 A1 relates to a method for operating a vehicle, comprising the following steps: determining a distance between the vehicle and another vehicle traveling behind the vehicle, determining a relative speed between the vehicle and the other vehicle, determining a speed of the vehicle, determining a minimum required braking distance for the other vehicle based on a predetermined coefficient of friction of a road on which the two vehicles are traveling, the distance, the relative speed and the speed in order to avoid a collision between the vehicle and the other vehicle; comparing the determined braking distance with the determined distance between the vehicle and the other vehicle; guiding the vehicle based on the comparison in such a way that an available braking distance for the other vehicle is increased.

[0008] On the one hand, the distance between an ego vehicle and a vehicle in front should be sufficiently large to react to unforeseen actions of the vehicle in front. On the other hand, the distance should not be too large to avoid requiring continuous adjustments due to other road users queuing in front of the ego vehicle.

[0009] Based on this, the present invention addresses the problem of selecting a distance between an ego vehicle and a vehicle traveling ahead in such a way that a safe yet comfortable ride is possible. On the one hand, active and passive safety should be increased, while on the other hand, acceleration and braking operations should be minimized to optimize driving comfort and energy efficiency.

[0010] To achieve this object, the present invention relates in a first aspect to a device for adjusting a distance between an ego vehicle and a preceding vehicle, comprising: an input interface for receiving sensor data from an environmental sensor with information about a roadway in an area in front of the ego vehicle, a specified distance of a driver assistance system and a current following distance of a following vehicle; an evaluation unit for determining a friction coefficient of the road in the area in front of the ego vehicle and a road topology of the road in the area in front of the ego vehicle based on the sensor data; an adaptation unit for determining an adjusted distance based on the specified distance, the determined friction value, the road topology and the current following distance; and an output interface for transmitting the adjusted distance to the driver assistance system

[0011] In a further aspect, the present invention relates to a driver assistance system for controlling a distance between an ego vehicle and a preceding vehicle, comprising: a distance unit for determining a predetermined distance between the ego vehicle and the preceding vehicle based on a user input, a predefined control parameter and / or an automatic vehicle control system; a device as previously described; and a control unit for controlling a motor and / or a brake of the ego vehicle to adjust the distance to the vehicle in front based on the adjusted distance.

[0012] In a further aspect, the present invention relates to an ego vehicle having a device or a driver assistance system as described above and an environmental sensor for detecting a hazard in an area in front of the ego vehicle.

[0013] Further aspects of the invention relate to a corresponding method and a computer program product with program code for carrying out the steps of the method when the program code is executed on a computer, as well as a storage medium on which a computer program is stored which, when executed on a computer, effects execution of the method described herein.

[0014] Preferred embodiments of the invention are described in the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the present invention. In particular, the driver assistance system, the ego vehicle, the method, and the computer program product can be designed according to the embodiments described for the device in the dependent claims.

[0015] The device according to the invention serves to adjust a distance between an ego vehicle and a vehicle traveling ahead. A current distance of a driver assistance system is used as an input variable. The distance can be specified, for example, based on a user input or based on an autonomous decision of a corresponding automatic vehicle control system of an autonomous or semi-autonomous vehicle. This specified distance currently used in the driver assistance system is adjusted based on sensor data from an environmental sensor. Based on the sensor data, a friction value of the road surface in an area in front of the ego vehicle is determined or estimated. This friction value is evaluated to determine whether an adjustment of the specified distance is necessary. In particular, it is determined whether the specified distance should be increased or decreased in order to adapt the distance to the current road condition.The adjusted distance determined by the device according to the invention is transmitted back to the driver assistance system. Based on this, the driver assistance system can then control an engine and / or a brake of the ego vehicle accordingly in order to adjust or correct the distance to the vehicle ahead according to the adjusted distance.

[0016] In comparison to previous approaches for automatically selecting a distance from the vehicle ahead, the invention also takes into account the friction coefficient of the road surface in the area that the ego vehicle will travel through in the immediate future. In this respect, the current road situation is included. Previous approaches typically assume standard values for road surface friction in order to estimate a braking distance and, based on this, select a situation-appropriate distance from the vehicle ahead. It does not take into account that different road surfaces can cause significant differences in the braking and evasive behavior of the ego vehicle. For example, a significantly longer braking distance can be expected on an icy road than on a dry road. Modern sensor technology allows for insights into the current and immediately expected road surface.By taking this information into account, the safety of the ego vehicle can be improved and driving comfort and energy efficiency can be increased by avoiding acceleration and braking processes.

[0017] In an advantageous embodiment, the adjustment unit is designed to determine an adjusted distance that is greater than the specified distance if the determined friction value falls below a predefined standard friction value. Furthermore, the adjustment unit is designed to determine an adjusted distance that is smaller than the specified distance if the determined friction value exceeds a predefined standard friction value. Previous approaches have usually assumed an average (standard) friction value in order to establish a sufficient safety standard based on this. Based on this standard friction value, which is known as a predefined parameter, the required safety distance can be increased or decreased by comparing it with the current friction value.In particular, the distance can be increased if it is determined that the current friction is lower than the friction under standard conditions. This ensures that the vehicle behavior or the behavior of the driver assistance system is adapted to the current situation of the ego vehicle.

[0018] According to the invention, the evaluation unit is designed to determine a road topology of the road in the area in front of the ego vehicle based on the sensor data. Furthermore, the adaptation unit is designed to determine the adjusted distance based on the road topology. In addition to taking the friction coefficient into account, a further improvement can be achieved by including a road topology in determining the adjusted distance. A road topology is understood to be a course of the road. The road topology preferably includes an incline of the road. In particular, the road topology includes a positive or negative incline of the road (uphill or downhill gradient). For example, an increased adjusted distance may be necessary on a downhill road. The adaptation of the distance to the requirements of the current environmental situation is further improved.

[0019] According to the invention, the input interface is designed to receive a current following distance of a following vehicle. Furthermore, the adaptation unit is designed to determine the adjusted distance based on the current following distance. It is possible that the distance of a following vehicle from the ego vehicle is also taken into account when calculating the adjusted distance. For example, a corresponding distance can be determined by a rear sensor. This allows a reaction to the behavior of the following vehicle. If the following vehicle maintains a sufficient safety distance, an adjustment of the distance between the ego vehicle and the vehicle in front is not necessary.However, if the safety distance of the following vehicle is too small, i.e. the following vehicle is following too closely, it can be advantageous to actively increase the distance between the ego vehicle and the vehicle in front. In the event of emergency braking, the following vehicle can then be given an additional safety buffer. The emergency braking of the ego vehicle, for example, does not occur with maximum braking force, so that the following vehicle has more time to react. In this respect, the knowledge available according to the invention about the road surface condition, in particular the coefficient of friction of the road surface, is used to reduce the probability of an accident with a following vehicle. The own knowledge is used, so to speak, to adjust the safety distance between the ego vehicle and the following vehicle. This can further improve active and passive safety.

[0020] In a further advantageous embodiment, the evaluation unit is designed to determine a safe following distance based on the current following distance of the following vehicle and the determined friction coefficient. Furthermore, the adaptation unit is designed to add a safety buffer to the adapted distance if the current following distance is smaller than the safe following distance. Preferably, based on the current friction coefficient, a safe following distance is first determined, which corresponds to a distance at which a following vehicle has sufficient reaction time in the event of emergency braking. Based on this determined safe following distance, it can be determined whether the adapted distance needs to be increased. In particular, the adapted distance is increased if the current following distance is smaller than the safe following distance.Active and passive safety are further improved.

[0021] In a further advantageous embodiment, the input interface is designed to receive rear sensor data from a rear environmental sensor. The rear sensor data includes information about a roadway in an area below and / or behind the ego vehicle. The evaluation unit is designed to determine a rear friction coefficient of the roadway in the area below and / or behind the ego vehicle based on the rear sensor data. Furthermore, the adaptation unit is designed to determine the adjusted distance based on the rear friction coefficient. In addition to taking into account the roadway condition in the area in front of the ego vehicle, it is also possible to take into account a condition or a friction coefficient of the roadway below or behind the ego vehicle.For example, the distance between the ego vehicle and the vehicle in front can be increased if, due to a road surface with a low coefficient of friction behind the ego vehicle, it is determined that a following vehicle may have difficulty braking. The increased, adjusted distance between the ego vehicle and the vehicle in front can then allow this following vehicle additional reaction time in the event of an emergency stop by the ego vehicle. For example, braking can be performed with a braking force that is less than the maximum braking force. This improves driving comfort on the one hand, and safety on the other.

[0022] In a further advantageous embodiment, the input interface is configured to receive rain sensor data from a rain sensor. Furthermore, the evaluation unit is configured to determine the friction coefficient and / or the rear friction coefficient based on the rain sensor data. It is also possible to take into account whether the road surface is wet. Typically, a wet road surface has a lower friction coefficient than a dry road surface. The additional use of a rain sensor can improve the accuracy of determining the current friction coefficient. The determined friction coefficient is more informative with regard to the actual current friction.

[0023] In an advantageous embodiment, the input interface is configured to receive sensor data from a radar, lidar, and / or ultrasonic sensor. The evaluation unit is preferably configured to determine the damping of the road surface. If a distance-based sensor principle is used, a conclusion can be drawn about the damping or reflectivity of the ground based on the received reflection of the signal. This allows the coefficient of friction of the road surface to be determined. By using a sensor principle already present in modern vehicles, the device according to the invention can be used without additional dedicated environmental sensors. Costs can be reduced.

[0024] In an advantageous embodiment, the input interface is designed to receive sensor data from a camera sensor. Preferably, the evaluation unit is designed to determine light reflection from the road surface. Alternatively or additionally, it is possible to use a camera, which is also regularly present in modern vehicles. Different surfaces cause different reflections. Based on these reflections, conclusions can be drawn about the condition and friction coefficient of the road surface.

[0025] An area in front of the ego vehicle here specifically includes a section of road that the ego vehicle will travel over in the immediate future. An environmental sensor can also comprise multiple sensors. On the one hand, it is possible to combine (merge) different sensor principles. On the other hand, it is alternatively or additionally possible to use sensors of the same type, which, for example, enable a 360-degree panoramic view. A road surface's friction value corresponds specifically to a friction coefficient. A road surface's friction value depends specifically on the road surface (material properties) and the current weather conditions (humidity, temperature, etc.).

[0026] It is also possible that the properties of the vehicle's current tires are taken into account when determining the friction coefficient. A predefined standard friction coefficient may correspond to a value programmed into a driver assistance system. It is also possible that the predefined standard friction coefficient corresponds to a value determined in tests that is only indirectly used as the basis for a corresponding control in a driver assistance system.

[0027] A following distance refers to the distance between an ego vehicle and a following vehicle, i.e., a vehicle located behind the ego vehicle in the same direction of travel and on the same lane. A leading vehicle refers to a vehicle located in front of the ego vehicle on the same lane, i.e., within a lane area that the ego vehicle will travel through in the immediate future. A road topology refers to the geometric properties of the road course.

[0028] The computer program product may be stored / distributed on a non-volatile storage medium, for example, on an optical storage device or on a solid-state drive (SSD). A computer program may be distributed together with hardware and / or as part of hardware, for example, via the Internet or via wired or wireless communication systems.

[0029] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show: Fig. 1 a schematic representation of an ego vehicle according to the invention; Fig. 2 is a schematic representation of a distance adjusting device according to the present invention; Fig. 3 a schematic representation of the inventive approach for taking road typology into account; Fig. 4 a schematic representation of the inventive approach for taking into account a following distance of a following vehicle; Fig. 5 a schematic representation of an ego vehicle according to the invention; and Fig. 6 a schematic representation of a method according to the invention.

[0030] Fig. 1 shows a schematic representation of an ego vehicle 10 according to the invention. The ego vehicle 10 comprises a device 12 for adjusting a distance d between the ego vehicle 10 and a vehicle 14 traveling ahead, as well as an environmental sensor 16 connected to the device 12. The direction of travel of the ego vehicle 10 runs from left to right in the illustration. Information about a roadway 18 in an area in front of the ego vehicle 10 is received via the environmental sensor 16. Based on the received sensor data, a friction coefficient of the roadway is calculated. Based on this calculated friction coefficient, the distance d to the vehicle 14 traveling ahead is adjusted.

[0031] The present invention is based on the fact that in previous systems the calculation of a safe distance between an ego vehicle (own vehicle) and a vehicle driving ahead is based solely on a measurement of a current distance or a current speed. Based on this, a potential braking distance is calculated and a safe distance is derived. In modern adaptive cruise control systems, the geometry of the road surface is sometimes also taken into account. The potential braking distance is therefore calculated based on a predefined friction value (default value). A comparatively high friction value is usually assumed. The potential braking distance therefore does not always correspond to reality. Even if a current friction value were used, i.e. a friction value of the road surface below the ego vehicle, the situation in the area in front of the ego vehicle can be different.According to the invention, the current friction coefficient of the road ahead of the vehicle is estimated based on sensor data, and a realistic braking distance for the vehicle is determined based on this. This predictive calculation of the friction coefficient can improve driving safety.

[0032] In the Fig. 2 schematically shows a device 12 according to the invention. The device comprises an input interface 20, an evaluation unit 22, an adaptation unit 24, and an output interface 26. The device 12 according to the invention can, for example, be integrated into a vehicle control unit or be designed as part of a driver assistance system, or even be implemented as a separate module. It is possible for the device according to the invention to be partially or completely implemented in software and / or hardware. The various units and interfaces can preferably be designed as a processor, processor module, or software for a processor.

[0033] Sensor data from an environmental sensor is received via the input interface 20. The input interface 20 can, for example, be implemented as a plug-in connection in hardware. It is also possible for the input interface 20 to be designed as a corresponding software interface for receiving data. The received sensor data includes information about the road surface in an area in front of the ego vehicle. In particular, the sensor data includes information about the condition of the road surface in the area that will be driven over in the immediate future. It is understood that the sensor data can include further information. In particular, data from a sensor that is already present on the vehicle can be received via the input interface 20. The data is usually received in digital, preprocessed form. For example, the input interface 20 can be coupled to a vehicle bus for this purpose.

[0034] In the evaluation unit 22, the received sensor data is evaluated to determine a coefficient of friction of the road surface. For this purpose, image processing algorithms or other evaluation algorithms can be used, for example. In particular, the roughness of the reflective surface can be determined based on the attenuation of an electromagnetic signal, a light signal, or an ultrasonic signal. Based on this, it is possible to estimate the current coefficient of friction. A rough surface usually has a higher coefficient of friction than a smooth surface, which reflects the aforementioned signals better. It is also possible to evaluate a camera signal. In particular, highly reflective areas within a camera image can indicate that there is lower friction in these areas.For example, reflection can mean that the road surface is icy or wet and therefore has less friction.

[0035] In the adaptation unit 24, an adjusted distance is determined based on the determined friction coefficient and the specified distance. In particular, the specified distance is corrected to take into account the current road surface conditions in front of the ego vehicle. For example, the specified distance can be increased in the case of a comparatively smooth road surface in the area in front of the vehicle. It is also possible for a predefined standard friction coefficient to be taken into account when adjusting the distance. Such a standard friction coefficient can be included in the calculation of the specified distance previously performed within the driver assistance system. Such standard friction coefficients are usually set relatively high. If it is determined in the current situation that the road surface is smoother than defined by the standard friction coefficient, the adjusted distance can be increased compared to the specified distance.

[0036] A predefined distance is also received via input interface 20. For this purpose, input interface 20 communicates with a driver assistance system. Communication can also take place, for example, via the vehicle bus. The predefined distance corresponds, for example, to a controlled variable, in particular a setpoint or an actual value of the controlled variable of the distance control system. The predefined distance can be based, for example, on a user input from a specification by the vehicle driver. It is also possible for the predefined distance to be determined based on an autonomous decision by a vehicle control system of a semi-autonomous or autonomous vehicle.

[0037] The determined adjusted distance is transmitted back to the driver assistance system via the output interface 26. The output interface 26 can, for example, be designed in accordance with the input interface. It is possible for the output interface 26 to be integrated with the input interface 20. The adjusted distance is determined and transmitted back, for example, in the form of an absolute value (metric value) or in the form of a relative value (value relative to the specified distance).

[0038] In the Fig. Figure 3 schematically illustrates an optional and advantageous development of the functioning of the device 12 according to the invention or of the vehicle 10 according to the invention. In addition to determining the friction coefficient of the road surface 18 in the area in front of the ego vehicle, a road surface topology can be determined based on the received sensor data. In particular, it is possible that, as in Fig. 3, there is an incline in the roadway. In the example shown, it is indicated that the roadway is rising. This roadway topology can be taken into account when determining the adjusted distance to the vehicle 14 in front. In the case of an uphill roadway, for example, it may not be necessary to increase the distance to the vehicle 14 in front despite the road surface being slippery if, at the same time, there is an uphill roadway 18 in the area in front of the ego vehicle 10. Due to gravity, braking can still be carried out sufficiently quickly in this case. It is understood that the present illustration is merely to be understood as an example. It is also possible that in the case of a negative incline of the roadway, i.e. a downhill gradient, an increased adjusted distance is determined despite a high coefficient of friction.

[0039] In the Fig. Figure 4 schematically illustrates a further optional and advantageous mode of operation of the device 12 according to the invention or of the ego vehicle 10 according to the invention. In addition to taking into account the distance d between the ego vehicle 10 and the preceding vehicle 14, a following distance n to a following vehicle 28 can be taken into account. The following distance n can be determined, for example, via a rear environmental sensor 30.

[0040] First, the device 12 according to the invention prevents an accident (collision) between an ego vehicle 10 and a vehicle 14 traveling in front. This does not necessarily take into account the fact that an accident could occur between the ego vehicle 10 and a following vehicle 28 traveling behind if the following vehicle 28 does not also maintain a safe distance. In particular, it is possible that the following vehicle 28 does not even have the appropriate sensor technology. In order to improve the safety of the ego vehicle 10 (active safety) and the other road users (passive safety) in this case and to avoid an accident with both the vehicle 14 traveling in front and the following vehicle 28, the device 12 according to the invention can determine whether or not the following vehicle 28 is maintaining a safe distance.If the following distance is smaller than a safe distance, the ego vehicle 10 can increase the distance to the preceding vehicle 14. This allows the ego vehicle 10 to gain a buffer, which can be advantageous in an emergency situation.

[0041] For example, an emergency situation may arise in which the vehicle 14 driving ahead brakes very sharply. The ego vehicle 10 must then also brake sharply in response. Since the ego vehicle 10 has sufficiently dimensioned the distance d to the vehicle 14 driving ahead using the device 12 according to the invention and has adapted it to the current road surface conditions (friction coefficient), a collision between the ego vehicle 10 and the vehicle 14 driving ahead can be avoided. However, if the following vehicle 28 did not maintain a safe distance, a collision between the following vehicle 28 and the ego vehicle 10 is unavoidable. According to the invention, it is possible for the traffic situation behind the ego vehicle to be observed within the device 12 according to the invention and, based on this information, to determine whether the following vehicle 28 is traveling at a sufficient distance.If this is not the case, the distance d between the ego vehicle 10 and the vehicle 14 traveling ahead is increased to create a buffer. In an emergency situation, it is now possible for the ego vehicle 10 to briefly reduce braking force or even accelerate slightly. This allows the following distance n between the ego vehicle 10 and the following vehicle 28 to be briefly increased to avoid a collision. Since the ego vehicle 10 has dimensioned the distance d to the vehicle 14 traveling ahead with a buffer, a collision between the ego vehicle 10 and the vehicle 14 traveling ahead can also be avoided.

[0042] The current distance of the following vehicle is determined using appropriate environmental sensors. The corresponding information is received via the input interface of device 12. When calculating the safe distance, i.e., when assessing whether the distance between the following vehicle 28 and the ego vehicle 10 is sufficient for an emergency situation, the friction coefficient of the road surface 18 can be taken into account. Optionally, it is also possible to include a friction coefficient for a road surface 32 in the area below and / or behind the ego vehicle 10.

[0043] In the Fig. 5 schematically shows an ego vehicle 10 according to the present invention. The vehicle comprises a device 12, which in the illustrated embodiment is integrated into a driver assistance system 34. The driver assistance system 34 comprises an environmental sensor 16, with which the roadway in an area in front of the ego vehicle is perceived. The environmental sensor 16 can be, for example, a radar, lidar, ultrasound and / or camera sensor. Furthermore, the ego vehicle 10 comprises a motor 36 and a brake 38, which can be controlled via a control unit 40 of the driver assistance system 34. By controlling the motor 36 and the brake 38, the ego vehicle 10 can be accelerated and / or decelerated in order to regulate a distance from the vehicle in front.

[0044] The driver assistance system 34 further includes a distance unit 42, which serves to determine a predetermined distance between the ego vehicle 10 and a vehicle traveling ahead. This distance unit 42 can, for example, take into account a current measured value from the environmental sensor 16. Furthermore, a value from a user input and / or a predefined parameter or information received from an automatic vehicle control system can also be used.

[0045] Optionally, it is possible for the ego vehicle 10 to also include a further, rearward environmental sensor 30, which provides sensor data with information about a roadway in an area and / or behind the ego vehicle 10. Based on this information, a rearward friction value can then be calculated in an analogous manner in order to be able to take this information into account when determining a safe distance from a following vehicle.

[0046] In the Fig. Figure 6 schematically illustrates a method according to the invention. The method comprises the steps of receiving S10 sensor data, determining S12 a friction value, determining S14 an adjusted distance, and transmitting S16 the adjusted distance. The method can be implemented, for example, as software that is executed on a vehicle control unit. It is also possible for the method according to the invention to be implemented as software for a mobile device (smartphone app). The method can also be executed entirely or partially in a cloud-based manner. Reference symbol 10 Ego Vehicle 12 Device 14 vehicle ahead 16 Environmental sensor 18 Lane in front of the ego vehicle 20 Input interface 22 Evaluation unit 24 adjustment unit 26 Output interface 28 following vehicle 30 rear ambient sensor 32 Roadway under / behind the ego vehicle 34 Driver assistance system 36 engine 38 Brake 40 Control unit 42 distance units

Claims

[1] Device (12) for adjusting a distance between an ego vehicle (10) and a preceding vehicle (14), comprising: - an input interface (20) for receiving sensor data from an environmental sensor (16) with information about a roadway (18) in an area in front of the ego vehicle, a predetermined distance of a driver assistance system (34) and a current following distance of a following vehicle (28); - an evaluation unit (22) for determining a friction value of the road in the area in front of the ego vehicle and a road topology of the road (18) in the area in front of the ego vehicle (10) based on the sensor data; - an adaptation unit (24) for determining an adjusted distance based on the predetermined distance, the determined friction coefficient, the road surface topology and the current following distance; and - an output interface (26) for transmitting the adjusted distance to the driver assistance system. [2] Device (12) according to claim 1, wherein the adaptation unit (24) - is designed to determine an adjusted distance which is greater than the predetermined distance if the determined friction value falls below a predefined standard friction value; and - is designed to determine an adjusted distance which is smaller than the specified distance if the determined friction value exceeds a predefined standard friction value [3] Device (12) according to one of the preceding claims, wherein the roadway topology comprises an inclination of the roadway (18). [4] Device (12) according to claim 3, wherein - the evaluation unit (22) is designed to determine a safe following distance based on the current following distance of the following vehicle (28) and the determined friction value; and - the adjustment unit (24) is designed to add a safety buffer to the adjusted distance if the current follow-up distance is smaller than the safe follow-up distance. [5] Device (12) according to one of the preceding claims, wherein - the input interface (20) is designed to receive rear sensor data from a rear environmental sensor (30); - the rear sensor data comprise information about a roadway (32) in an area below and / or behind the ego vehicle (10); wherein the evaluation unit (22) is designed to determine a rear friction coefficient of the roadway in the area below and / or behind the ego vehicle based on the rear sensor data; and wherein the adaptation unit (24) is designed to determine the adjusted distance based on the rear friction coefficient. [6] Device (12) according to one of the preceding claims, wherein - the input interface (20) is designed to receive rain sensor data from a rain sensor; and - the evaluation unit (22) is designed to determine the friction value and / or the rear friction value based on the rain sensor data. [7] Device (12) according to one of the preceding claims, wherein - the input interface (20) is designed to receive sensor data from a radar, lidar, and / or ultrasonic sensor; and - the evaluation unit is preferably designed to determine a damping of the roadway (18). [8] Device (12) according to one of the preceding claims, wherein - the input interface (20) is designed to receive sensor data from a camera sensor; and - the evaluation unit (22) is preferably designed to determine a light reflection of the roadway (18). [9] Driver assistance system (34) for controlling a distance between an ego vehicle (10) and a preceding vehicle (14), comprising: - a distance unit (42) for determining a predetermined distance between the ego vehicle and the preceding vehicle based on a user input, a predefined control parameter and / or an automatic vehicle control system; - a device (12) according to one of the preceding claims; and - a control unit (40) for controlling a motor (36) and / or a brake (38) of the ego vehicle in order to adjust the distance to the vehicle in front based on the adjusted distance. [10] Ego vehicle (10), with: - a device (12) according to one of claims 1 to 8 or a driver assistance system (34) according to claim 9; and - an environmental sensor (16) for detecting a roadway (18) in an area in front of the ego vehicle. [11] Method for adjusting a distance between an ego vehicle (10) and a preceding vehicle (14), comprising the steps: - receiving (S10) sensor data from an environmental sensor (16) with information about a roadway (18) in an area in front of the ego vehicle, a predetermined distance of a driver assistance system (34) and a current following distance of a following vehicle (28); - determining (S12) a friction value of the road in the area in front of the ego vehicle and a road topology of the road (18) in the area in front of the ego vehicle (10) based on the sensor data; - determining (S14) an adjusted distance based on the specified distance, the determined friction value, the road surface topology and the current following distance; and - Transmitting (S16) the adjusted distance to the driver assistance system. [12] A computer program product comprising program code for performing the steps of the method according to claim 11 when the program code is executed on a computer.

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