Method for displaying a braking distance and device for this purpose

Abstract

Method for displaying a braking distance, calculated from a reaction time and the time required for braking, on a display device (1) of a vehicle (6) in the form of a horizontal bar (8, 9), wherein a first horizontal bar (8) is displayed in a virtual representation of the vehicle (6) and other road users (7) or objects in the environment in spatial relation to each other to represent a first braking distance, wherein a second horizontal bar (9) is additionally displayed, which represents a second braking distance, in which a change in the reaction time due to detected fatigue and / or distraction of the person driving the vehicle (6) is taken into account compared to the first braking distance, wherein the two horizontal bars (8, 9) are hidden when a road user (7) ahead is detected and displayed, wherein the two horizontal bars (8, 9) are always displayed despite the road user (7) ahead.if, given a specified theoretical maximum deceleration of the vehicle ahead (7), a rear-end collision could not be prevented even with the aid of brake assist systems in the event of a sudden deceleration of the vehicle ahead.

Description

The invention relates to a method for displaying a braking distance according to the type defined in claim 1. The invention also relates to a device according to claim 10 for carrying out the method. From DE 10 2015 210 782 A1 a driver assistance system for determining the cognitive activity and level of attention of a driver of a means of transport is known. German patent application DE 10 2018 206 666 A1 discloses a method for warning a driver, whereby a driving situation signal is read in. A prediction profile represents an expected decrease in performance depending on the driving situation, and a warning tone is emitted when the current driving situation corresponds to a driving situation in a prediction profile with an expected decrease in performance. From JP 2015 - 196 403 A, a representation of a braking distance on a head-up display in the form of a graphic element is known. The determination of the braking distance takes into account the condition of the road surface as well as the driver's condition. German patent DE 10 2011 121 763 A1 discloses the display of a braking distance in the form of a horizontal bar in an extended real-time image within a vehicle. The braking distance is composed of a reaction time and a braking time, whereby the reaction time is taken into account according to the aforementioned document using fixed, predefined values. JP 2021-46079A discloses a head-up display for augmenting a braking distance represented by a hatched area on a road ahead of a vehicle. An increase in braking distance caused by driver fatigue is indicated to the vehicle user by another hatched area. The object of the present invention is to provide a method for representing a braking distance that is improved compared to the prior art, as well as a suitable device for this purpose. According to the invention, this problem is solved by a method with the features of claim 1. Advantageous embodiments and further developments of the method according to the invention are set forth in the dependent claims. Furthermore, a device according to the invention with the features of claim 10 solves the problem. In the method according to the invention, a braking distance is displayed as a horizontal bar on a vehicle's display device, similar to the prior art. This braking distance is fundamentally calculated from a reaction time and the time required for braking. In the method according to the invention, such a horizontal bar is displayed as a first horizontal bar, comparable to the horizontal bar in the prior art, but in a virtual representation of the vehicle and other road users or objects in the environment. The vehicle and the other road users or objects, as well as the first braking distance, are spatially related to each other, i.e., they show a distance corresponding to reality in the virtual representation. In the method according to the invention, a second horizontal bar is superimposed on this virtual representation of the user's own vehicle, also referred to as an ego vehicle, and other road users, in particular vehicles or objects. This second horizontal bar represents a modified braking distance, taking into account a change in the driver's reaction time compared to the first braking distance. This change in reaction time is achieved using monitoring devices and their results, which are fundamentally known from the prior art. Such monitoring devices can, in particular, detect fatigue or distraction of the driver. For example, fatigue detection systems known from the prior art monitor the fatigue of a driver based on blink rates, pupil movements, and similar indicators.If driver fatigue is detected in this way, the second, extended braking distance is displayed in the virtual representation in addition to the first. A driver can then see how much more distance is needed to brake, as they may be fatigued or distracted by other factors, such as a passenger, children in the vehicle, or similar distractions. Because this difference is visualized, the driver can assess its safety relevance and, for example, follow the vehicle ahead at a greater distance than usual in such a situation, thus increasing road safety. Furthermore, according to the inventive method, the two horizontal bars are hidden when a vehicle ahead is detected and displayed in the virtual representation.This also serves to avoid creating unnecessary distractions with the two horizontal bars and to focus attention on recognizing the vehicle ahead in the virtual display. Furthermore, it may be designed so that the two horizontal bars are always displayed, despite the presence of a vehicle ahead, if, given a predetermined theoretical maximum deceleration, a rear-end collision cannot be prevented in the event of sudden braking by the vehicle ahead, even with the aid of brake assist systems. The premise here is therefore, on the one hand, to minimize distraction when there is still sufficient distance to the vehicle ahead.If this distance is reduced and the braking distance is no longer sufficient to prevent an accident in the event of sudden braking by the vehicle in front, then the principle of minimal distraction is disregarded and the crossbars are displayed to generate a clear warning to the driver, so that they can react accordingly and, for example, increase the distance until the potential braking distance is sufficient again, i.e., until the crossbars are hidden again. According to a further highly advantageous embodiment of the method according to the invention, it can now also be provided that the first braking distance, represented by the first crossbar, is determined in relation to the vehicle, i.e., the ego-vehicle, depending on a class of reaction time of a person driving the vehicle, wherein this person is stored in a profile assigned to them. According to a highly advantageous further development, the class of reaction behavior can be determined, adapted, and stored in such a way that the reaction time is taken into account based on cyclical observations of the driving behavior of the respective person. For example, sensors can detect that a vehicle ahead is braking sharply because, for instance, there is a very dynamic reduction in distance. A reaction time can then be determined from the corresponding reaction of the person driving the vehicle.The reaction time is the time difference between detecting the braking of the vehicle ahead and applying the brakes. Alternatively, the sensors can detect, for example, when a traffic light changes and determine the reaction time based on the time difference between detecting the change and pressing the brake pedal. In this way, individual averaged reaction times can be determined for different people whose profiles are stored in the vehicle. These averages can then be used to customize the first bar for the driver, unlike current technology, instead of assuming a standardized reaction time. A person with a correspondingly faster reaction time, which is above average, will then be shown a correspondingly shorter braking distance than, for example, a person whose reaction time is typically always above average. The reaction time class can be adjusted depending on the context, according to a very advantageous further development of this aspect of the procedure. Such a context can include, for example, the time of day, the weather, or similar factors. If, for instance, the weather conditions are particularly difficult or it is a time of day unfavorable for road safety, such as driving at dusk, the reaction time can be increased accordingly, i.e., offset by being moved up one or two classes, depending on the context. The displayed initial braking distance is thus lengthened accordingly, indicating to the driver that they should maintain a slightly greater distance in the current situation. As already mentioned, and as is also provided for in a very advantageous further development of the method according to the invention, the second braking distance represented by the second crossbar can be determined as a function of a fatigue class determined by a fatigue assistant. Such a fatigue class can be determined, for example, by a fatigue assistant which, unlike the basic classification of a person driving a vehicle into a class based on their typical reaction time, observes the current situation. If the person is correspondingly fatigued and blinks more frequently or has longer periods of closed eyes, or the like, the second braking distance can be increased accordingly via a corresponding fatigue class in order to visualize the existing risk for the person and thus encourage them to adopt safe driving behavior. As an alternative to a fatigue class, the second braking distance, represented by the second horizontal bar, can also be determined based on a distraction class. Part of the distraction monitoring can involve checking whether, for example, a passenger or children are present in the vehicle in addition to the driver. Other aspects, such as a hands-free phone call, the volume of a sound system, or similar factors, can also be considered in these distraction assessments and lead to an upgrade or downgrade of the corresponding classes, with the associated reduction or, typically, lengthening of the reaction time. Adjusting the reaction time based on relevant profiles and / or classes—whether these are currently determined fatigue or distraction classes, or a class of typical reaction time stored for the individual—can be done rule-based using an assignment table. Depending on the class, a time interval can be read from the assignment table, by which the initial reaction time is modified to obtain a new typical reaction time for the individual, or a new temporary reaction time due to fatigue and / or distraction. This new time then forms the basis for the display of the horizontal bars in the virtual representation. The inventive method can provide that the crossbars are only displayed when the vehicle is moving at a speed above a speed threshold that separates creeping and / or maneuvering modes from driving mode. According to this particularly advantageous embodiment of the inventive method, the two crossbars are therefore only displayed when a speed has been reached at which the vehicle is actually driving and not, for example, maneuvering while parking or the like, since in such situations the display is more likely to distract from the traffic situation and thus does not promote road safety. The predefined theoretical maximum deceleration of the vehicle ahead is determined by assigning it a class based on the vehicle's sensors. For example, if a vehicle is detected, a corresponding class is assigned, depending on whether it is a passenger car, truck, or motorcycle, indicating the average maximum deceleration of such a vehicle. Typically, a motorcycle, for instance, is expected to have a much greater maximum deceleration and therefore a much shorter braking distance than a passenger car or, especially, a truck, which has a correspondingly longer braking distance. The device according to the invention for carrying out the method in one of the embodiments described above now comprises a display device and at least one monitoring means. The monitoring means is designed to detect fatigue and / or distraction of the person driving the vehicle. It can, for example, be an interior camera that observes the person accordingly. Alternatively or additionally, however, other monitoring means are also conceivable, for example, areas of the steering wheel that measure the electrical properties of the skin, microphones that detect the ambient noise level, or the like. The display unit is now configured to overlay the first braking distance onto a virtual representation of the vehicle (the ego-vehicle) and other road users or objects in spatial relation to each other, in the form of a first horizontal bar. It is further configured to overlay a second braking distance onto a second horizontal bar. This second braking distance takes into account the increased reaction time resulting from distraction and / or fatigue detected by the monitoring system. This allows for a virtual representation within the vehicle, as described above. Further advantageous embodiments of the method and the device according to the invention will also become apparent from the exemplary embodiment, which is described in more detail below with reference to the figure. The only accompanying Fig. 1 shows a device according to the invention, as it can be arranged in the interior of a vehicle. In the illustration of Fig. 1, a display device 1, for example in the form of a rectangular screen, can be seen. Above the display device 1, an interior camera 2 is shown as a monitoring device for detecting the fatigue of a person driving the vehicle (not shown). Both the display device 1 and the monitoring device in the form of the interior camera 2 are coupled to each other via electronics 3. A so-called horizon image is displayed on the display device 1. A road 4 and a horizon 5 are visible. On the road 4, the driver's own vehicle 6, which is also referred to as the ego vehicle 6 and is marked here, for example, by cross-hatching, is shown in a virtual representation.In a real-world representation within a vehicle, a different color scheme is typically chosen for the ego-vehicle than for other road users, instead of such hatching. In the illustration of Fig. 1, another vehicle 7 is depicted as a further road user on the road 4 in the direction of travel F in front of the ego-vehicle 6. A first crossbar 8 and a second crossbar 9 are superimposed in the virtual representation in the direction of travel F in front of the ego-vehicle 6. These two crossbars 8, 9 indicate a first and a second braking distance of the ego-vehicle 6. The first braking distance, which is represented by the first crossbar 8 as seen from the ego-vehicle 6, is ideally based on the average reaction time of a person driving the ego-vehicle 6, which was determined in the past through cyclical observation and is stored in a profile of the person.Longer-term adaptation can occur, for example, if the average reaction time of that person increases accordingly, for example due to increasing age or the like, so that these values ​​are updated in the profile. In addition to the first braking distance, represented by the first crossbar 8, a second crossbar 9 is shown to represent a second braking distance. This second braking distance, represented by the second crossbar 9, is typically somewhat longer than the first. This is because the reaction time used to determine the second braking distance is not the average reaction time determined for the individual, as with the first braking distance. Instead, the reaction time underlying this second braking distance has been extended because the interior camera 2, and possibly other monitoring devices not shown here, have detected a distraction or fatigue in the person driving the vehicle 6. Such distraction or fatigue can be detected, for example, by a fatigue detection system, which is a fundamental technology known in the prior art.In this case, the fatigue assistant determines a fatigue class, based on which the reaction time is extended, for example, using a table. Such fatigue assistants, which are already installed in many vehicles, also recommend taking a break or similar action if the level of fatigue becomes too high. For the implementation shown here, the fatigue assistant is important insofar as it takes the extended reaction time due to fatigue into account when calculating the second braking distance and displaying it with the second bar 9. A person driving vehicle 6 now recognizes that, due to fatigue or distractions such as a passenger, children in the vehicle, loud music, or similar factors, they will need more time to brake in an emergency.The person driving vehicle 6 can then sensibly increase their distance to the vehicle 7 driving ahead in order to achieve greater road safety. In practice, it is advisable to display the two crossbars 8 and 9 only when either no vehicle 7 ahead is visible, thus avoiding unnecessary distraction from the vehicle 7 ahead, or additionally—and this is crucial for the effect—the crossbars should also be displayed when it becomes apparent that the braking distance is no longer sufficient to decelerate should the vehicle 7 ahead brake suddenly. In this case, the displayed crossbars 8 and 9 serve as an immediate warning to the person driving vehicle 6, thus drawing their attention to the distance that should be increased. In the illustration of Fig. 1, the particularly relevant case was chosen where the initial braking distance, indicated by the first crossbar 8, is still sufficient to brake in an emergency.However, the braking distance displayed by the second crossbar, which is more realistic due to distraction and / or fatigue, would no longer be sufficient.

Claims

Method for displaying a braking distance, calculated from a reaction time and a time required for braking, on a display device (1) of a vehicle (6) in the form of a horizontal bar (8, 9), wherein a first horizontal bar (8) is displayed in a virtual representation of the vehicle (6) and other road users (7) or objects in the environment in spatial relation to each other to represent a first braking distance, wherein a second horizontal bar (9) is additionally displayed, which represents a second braking distance, in which a change in the reaction time due to detected fatigue and / or distraction of the person driving the vehicle (6) is taken into account compared to the first braking distance, wherein the two horizontal bars (8, 9) are hidden when a road user (7) ahead is detected and displayed, wherein the two horizontal bars (8, 9) are always displayed despite the road user (7) ahead.if, given a specified theoretical maximum deceleration of the vehicle ahead (7), a rear-end collision could not be prevented even with the aid of brake assist systems in the event of a sudden deceleration of the vehicle ahead. Method according to claim 1, characterized in that the first braking distance represented by the first crossbar (8) in relation to the vehicle (6) is determined as a function of a class of reaction time of a person driving the vehicle (6), which is stored in a profile assigned to the person. Method according to claim 2, characterized in that the reaction time class is determined, adapted and stored based on cyclical observations of the driving behavior of the respective person. Method according to claim 2 or 3, characterized in that the class is adapted depending on the context. Method according to one of claims 1 to 4, characterized in that the second braking distance represented by the second crossbar (9) is determined as a function of a fatigue class determined by a fatigue assistant. Method according to one of claims 1 to 5, characterized in that the second braking distance represented by the second crossbar (9) is determined depending on a distraction class which is determined on the basis of the number of passengers, the volume in the interior of the vehicle (6), an ongoing telephone call or the like. Method according to one of claims 2 to 6, characterized in that the reaction time is adjusted according to profiles and / or classes in a rule-based manner using an assignment table. Method according to one of claims 1 to 7, characterized in that the two crossbars (8, 9) are only displayed when the vehicle (6) is moving at a vehicle speed above a speed threshold which separates a creeping and / or shunting operation from a driving operation. Method according to claims 1 to 8, characterized in that the predetermined theoretical maximum deceleration of the preceding road user (7) is predetermined on the basis of a class into which the preceding road user (7) is classified with the aid of the sensors of the vehicle (6). Device configured for carrying out a method according to one of claims 1 to 9, comprising: a display device (1) configured to display the first braking distance in a virtual representation of the vehicle (6) and the other road users (7) or objects in spatial relation to each other in the form of a first crossbar (8), at least a monitoring means (2) for detecting fatigue and / or distraction of the person driving the vehicle (6);wherein the display device (1) is further configured to display the second braking distance, which takes into account a longer reaction time based on the distraction and / or fatigue detected by the monitoring means (2), in the form of a second horizontal bar (9), wherein the display device is configured to hide the two horizontal bars (8, 9) when a road user (7) ahead is detected and displayed, wherein the display device always displays the two horizontal bars (8, 9) despite the road user (7) ahead if, at a given theoretical maximum deceleration of the road user (7) ahead, a rear-end collision could not be prevented in the event of a sudden deceleration of the road user ahead even with the help of brake assist systems.

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