DE102014002111B4 - Method for operating a driver assistance system and motor vehicle that supports the driver during a coasting process - Google Patents

Abstract

Method for operating a driver assistance system (28) in a motor vehicle (7) which supports the driver during a coasting process, the drive train of which can be operated in a freewheeling operating mode in which a drive motor (34) is separated from the rest of the drive train by a disconnect clutch (35), characterized in that when the driver assistance system (28) is activated, when the driver finishes actuating the accelerator pedal and at least one potential roll-out target (9) requiring deceleration of the motor vehicle (7) is determined or known, at least one measure for targeted deceleration is determined of the motor vehicle (7) comprehensive action plan, taking into account at least one effectiveness criterion related to the energy budget of the motor vehicle (7) and a target criterion related to the delay to the roll-out target (9) as well as predictive describing the path (8) to the roll-out target (9) Route data determined and for longitudinal guidance ng of the motor vehicle (7) is used, the measures being selected from a group of measures comprising at least one operation in freewheeling mode and operation in overrun mode, and the effectiveness criterion and the target criterion being used as optimization goals in an optimization method, with a determination and execution of an action plan takes place after an indication of the termination of an operation of the accelerator pedal to a driver, with a maximum permitted braking deceleration and / or a maximum permitted change in the braking deceleration being taken into account when determining the action plan, the maximum permitted braking deceleration and / or the maximum permitted change the braking deceleration before reaching the coasting target can be decreased as a function of the waiting time of the driver that has passed since the output of an instruction to terminate an operation of the accelerator pedal to a driver as the waiting time increases.

Description

The invention relates to a method for operating a driver assistance system that supports the driver during coasting in a motor vehicle, the drive train of which can be operated in a freewheeling operating mode in which a drive motor is separated from the rest of the drive train by a disconnecting clutch. The invention also relates to a motor vehicle.

In the prior art, motor vehicles are already known, the drive train of which has a freewheel operating mode (also called coasting operating mode). When the motor vehicle freewheels or coasts, the frictional connection between the gearbox and the drive motor is interrupted by a disconnect clutch, so that the motor vehicle is in an extremely efficient operating state in which it is braked by fewer frictional effects. The separating clutch can be addressed by a control device, for example a transmission control device or an engine control device, in order to be opened if necessary.

In the prior art, automatic activation of the freewheel operating mode usually takes place when the driver stops operating the accelerator pedal. There are known vehicle systems in which the driver can decide for himself whether the freewheel mode is activated after the end of the operation of the accelerator pedal, i.e. the frictional connection between the transmission and drive motor is interrupted, or whether an overrun mode, in which the disconnect clutch remains closed, is activated. For example, a special drive mode, for example an efficiency mode or a sailing mode, can be activated via a suitable operating device.

It was also proposed to make an additional decision in an internal transmission function even when the freewheel function is activated, whether the freewheel mode is actually enabled or should be blocked depending on the driving situation, for example in the case of steep gradients / inclines, high lateral acceleration, high accelerator pedal gradients and the like, where blocking the freewheeling operating mode can increase safety.

Driver assistance systems related to a coasting process have already been proposed, which can be provided independently of the availability of a free-running operating mode. Such driver assistance systems detect possible coasting destinations ahead on the route, in particular locations where the motor vehicle should have a lower speed than the current speed. For this purpose, route data is used which can come from various sources, for example from navigation data, traffic sign recognition and the like. Possible roll-out targets that contain a position with a lower target speed are, for example, town entrances, speed limits, intersections and roundabouts, inclines / declines, curves and the like.

If such a coast-down target has been recognized, taking into account route data describing the route to the coast-down target, a point in time can be determined which, if the driver stops operating the accelerator at this point in time, leads to the target speed being reached at the coast-down target becomes. If the freewheel operating mode is automatically activated when the accelerator pedal is terminated, this point in time is often significantly earlier than when the motor vehicle remains in overrun mode, in which the engine brake also acts accordingly. The driver assistance systems known in the prior art now provide for an indication to terminate an operation of the accelerator pedal, for example "foot off the accelerator", to be output to the driver at the point in time or shortly before the point in time, so that when this proposal is implemented promptly and correctly Route data, the roll-out target can be reached easily and efficiently with the target speed there. It should be noted here that such a “foot off the accelerator” instruction can often be given much earlier than a driver would stop pressing the accelerator pedal based on his personal assessment.

As already mentioned, vehicles that can run freely ("sailable"), in which the decoupling clutch between engine and transmission is opened during the coasting process, are in many cases more energetically efficient. The motor vehicle rolls significantly better and further due to reduced driving resistance. Moreover, embodiments are also known in which the drive motor of the motor vehicle, in particular an internal combustion engine, is switched off during the freewheeling operating mode.

With regard to the free-wheeling operating mode, it should be noted that the decision as to whether the free-wheeling operating mode or a coasting operating mode is selected often only depends on a setting made by the driver. With regard to variables describing the current driving situation, the decision can be changed on the transmission side if this is expedient for safety considerations. With regard to the coasting processes mentioned, the decision as to whether the free-wheeling operating mode or a coasting operating mode is active is no longer changed during the entire coasting process.

With regard to the driver assistance systems, which issue instructions to the driver to terminate an actuation of the accelerator pedal, it should be noted that the acceptance and the frequency of use of such information functions depends heavily on how the coasting behavior of the motor vehicle appears as a function of the route and driving situation. Such a purely advisory function is only accepted in the long term if the vehicle behaves as expected. This means that the driver of the motor vehicle goes into an inactive and critically observing mode after he has finished actuating the accelerator pedal. In particular, the speed profile must be such that the driver still feels comfortable and does not immediately intervene again by pressing the accelerator pedal or by braking.

In principle, two cases are conceivable in which problems can arise with driver assistance systems with an advisory function to take your foot off the accelerator. On the one hand, it could happen that the arrival speed at the position at which the target speed is to be present is even higher than the target speed. This can occur, for example, if a gradient occurs in front of the roll-out destination as a speed limit event. Then the driver, who has followed an early instruction to end the operation of the accelerator pedal, surprisingly has to carry out a braking intervention in order to correct the vehicle speed. The coasting speed can also suddenly be assessed as too high if a slower vehicle is in front of one's own motor vehicle. Here, too, the driver has to intervene himself to brake.

However, it is also possible that the speed is too low when the coasting destination is reached, so that the driver can perceive himself as a traffic obstacle. This feeling increases when another road user is following your own motor vehicle and approaches, for example.

A major problem with driver assistance systems with such advisory functions is that ultimately the point in time at which the driver actually stops operating the accelerator pedal can hardly be predicted. For example, if a driver waits several seconds before reacting to a "foot off the gas" message, the coasting strategy determined there and subsequently implemented can no longer be successfully implemented and in particular leads to excessive speed at the coasting target. With today's driver assistance systems, without an advisory function, no support for the driver is given or can be implemented.

DE 10 2011 083 013 A1 describes a driver assistance system which determines the earliest possible point in time to start a coasting process and a latest possible point in time to start a braking process and selects the specific point in time for outputting a message to the driver to start a coasting process individually for the driver. This is intended to ensure better acceptance of the driver assistance system. However, one problem with the driver assistance system there is that, as already mentioned, drivers often start a coasting process much too late in order to reach the coasting target at the desired speed in the continuous free-wheeling operating mode or coasting operating mode. It is therefore necessary there to brake specifically to the target speed after the coasting process has been completed. However, this does not make sufficient use of the efficiency options provided by coasting processes.

The invention is therefore based on the object of creating a function for a driver assistance system which supports the driver during a coasting process and which enables the greatest possible use of the coasting process with high acceptance by the driver.

DE 10 2012 213 321 A1 relates to a method and a device for operating a vehicle, with an actual vehicle speed during coasting of the vehicle in order to reach a route position of a route that is still to be driven at a desired speed that is less than a vehicle speed at the start of coasting a vehicle target speed is compared and is carried out depending on the comparison of an action. A pre-calculation is carried out which describes a desired vehicle speed coasting curve, compliance with which is monitored. To readjust the speed, it is possible to switch to a freewheel operating mode or an overrun operating mode; other examples mentioned are recuperation using a generator and switching between gears.

DE 10 2010 023 198 A1 relates to a device and a method for controlling the driving behavior of a vehicle when approaching a stopping point. There a detection device should determine the distance between the vehicle and the stopping point, after which, taking into account at least the current vehicle speed, a rolling distance to the stopping point is determined from which a sailing operation should be enabled, so that the motor vehicle still comes to a standstill. A lowering of the energy consumption with comfortable driving behavior is to be achieved by using the sailing mode on the last section and thus a low-speed rotating drive is avoided.

DE 10 2011 082 337 A1 relates to a method for controlling energy conversion processes in a vehicle, the control of the energy conversion process being able to be modified or switched off if a disadvantageous interaction with the detected movement of a following road user is recognized.

DE 10 2010 048 323 A1 discloses a driver assistance system and a corresponding operating method for displaying or notifying a fuel-saving situation in order to reduce the fuel consumption of a motor vehicle. A driving recommendation for reducing the fuel consumption of the motor vehicle is determined by determining at least one consumption-relevant road property of a road on the upcoming route of the motor vehicle, the consumption-relevant road property influencing the fuel consumption of the motor vehicle. The driving recommendation is communicated to the driver in such a way that, based on its presentation over future development over time, it is suitable for increasing acceptance by the vehicle driver and making the functionality of the driver assistance system plausible.

To achieve this object, the features of claim 1 are provided according to the invention in a method of the type mentioned at the beginning.

In most cases it will be the case that the roll-out target includes a position at which the motor vehicle should have a lower setpoint speed than the current speed. Such coasting targets, derived for example from digital map data of a navigation system and / or sensor data, for example traffic sign recognition, can include, for example, the start of a route at a reduced permitted speed, for example a corresponding traffic sign or a town entrance, a curve that has to be driven through more slowly, a roundabout , an intersection, a steep slope and the like. Whenever such a coasting target is present or can be determined, the driver assistance system reacts immediately to the termination of the actuation of the accelerator pedal by the driver. The method according to the invention therefore initially works independently of an advisory function, which may be discussed in more detail below, and therefore supports the driver, albeit in a modified manner, if necessary, i.e. even when he takes his foot off the accelerator without prior advice the actuation of the accelerator pedal is terminated in order to achieve improved energy efficiency and an improved achievement of the target speed at the coasting target, i.e. the position contained. The proposed driver assistance system therefore also makes it possible to support the driver if he has not requested any information.

This is advantageously implemented in that a specific operating strategy of the motor vehicle is selected, which is mapped by the action plan comprising measures for decelerating the motor vehicle. In other words, the method according to the invention determines a predictive coasting operating strategy for freewheeling vehicles that does not, as is customary in the prior art, simply select either the coasting operating mode or the coasting operating mode and maintain it until the coasting target, but measures to switch between several contains operating states related to the longitudinal guidance of the motor vehicle, for example can switch between a freewheeling operating mode and a coasting operating mode, so that the highest possible efficiency and the most accurate possible achievement of the target speed are made possible. The effectiveness criterion, which relates to the energy efficiency of the motor vehicle, and the target criterion, which relates in particular to the target speed at the position described by the roll-out target, therefore represent the optimization goals in an optimization process for determining the measures which, what in Will be discussed in more detail below, for example, can be taken into account in a weighted manner in a cost function. The optimization process for determining the measures in the action plan therefore uses the predictive route data in order to achieve the highest possible energy efficiency and a delay that comes as close as possible to the target speed.

It should be pointed out that the route data represent a static description of the route ahead to the roll-out destination, in particular that it may contain its course, inclines, slopes, road surface and the like. A dynamic description of the preceding path to the coasting destination can also be taken into account particularly preferably within the scope of the present invention, which will be discussed in greater detail below. As already mentioned, predictive route data are mostly derived from digital map data of a navigation system of the motor vehicle, but can also contain information derived from sensor data from environment sensors of the motor vehicle. The predictive route data can also have already been used to determine the roll-out destination.

In addition to the predictive route data, ego data describing the current operation of the motor vehicle are of course also used taken into account, for example, its current speed already mentioned and the properties of the motor vehicle, which can be mapped, for example, in a dynamic model of the motor vehicle to be used when determining the action plan.

In this case, the dynamic model of the motor vehicle provides the option of determining how strong the braking deceleration is in various operating states of the motor vehicle, for certain properties of the route ahead, for example in the pure freewheeling operating mode of the drive train and with various gear stages engaged in the overrun mode of the drive train. Such dynamic models are already known in the prior art and do not have to be presented in more detail here. When braking deceleration is mentioned in the context of the present invention, this refers to any effects that slow the motor vehicle, therefore not exclusively to braking interventions, but also, for example, to deceleration effects and the like triggered by recuperation.

The method according to the invention thus focuses on the actual point in time at which the actuation of the accelerator pedal is ended and selects the best coasting operating strategy for this point in time, which is described by the action plan. For this purpose, in addition to the two already mentioned settings of operating states in the group of measures, other measures influencing the deceleration of the motor vehicle can also be provided in the group of measures.

In this case, a preferred embodiment of the present invention provides that a further group of measures comprising an adaptation of a recuperation stage and / or a change in a gear stage of a transmission of the motor vehicle and / or a braking intervention using a braking system of the motor vehicle is used. It should already be pointed out at this point that an actual braking intervention, as a measure that is least accepted by the driver, should be avoided as far as possible, for example it can be rated as extremely bad in an optimization process. In order to reduce the speed of the motor vehicle, certain measures which increase or decrease the delay can therefore be used in the action plan, which measures are defined by a group of measures. One of these measures, which is possible in any case, is the automatic change between the freewheeling operating mode and the overrun operating mode of the drive train by closing or opening the disconnect clutch. If the design of the separating clutch allows this, a sliding separating clutch for producing intermediate states is also conceivable within the scope of the present invention. Other measures for influencing the braking deceleration of the motor vehicle include, for example, switching between different gear stages of the transmission of the motor vehicle, so that the drag torque (engine brake) is increased or decreased. In motor vehicles with an electrified drive, for example a belt starter generator and / or an electric drive motor, an increase and / or decrease in the generator deceleration torque can also lead to a suitable adjustment of the braking deceleration, i.e. a change in the recuperation settings. Finally, it is also conceivable as a measure to control an automatically controllable brake system to carry out a braking process. This last possible measure is less preferred, however, since it is a general goal of the delay regulation and the determination of the action plan that the delay interventions are only perceived as slightly corrective, so that on the one hand the driver does not feel patronized / disturbed, on the other hand also There is no expectation that the driver assistance system will always brake hard enough and reliably to actually reach the target speed, which is not always sensible, especially when the coasting process is initiated late by the driver stopping to press the accelerator pedal. The permission to use braking interventions with a brake system can also be linked to an advisory function, so that, for example, as a measure, the control of the braking system of the motor vehicle to carry out a braking intervention can only be permitted if the driver provides a prompt to terminate the operation of the accelerator pedal followed within a predetermined time, for example 2 seconds, after issuing the notice.

1. a) Automatischer Wechsel vom Freilaufbetriebsmodus in den Schubbetriebsmodus (gleiche Schaltstufe) durch Schließen der Trennkupplung. Auf diese Weise erhöht sich das Schleppmoment.
2. b) Automatische Rückschaltung um eine oder zwei Schaltstufen im Schubbetriebsmodus, so dass eine (weitere) Erhöhung des Schleppmoments auftritt.
3. c) Erhöhung des generatorischen Verzögerungsmoment, mithin Anpassung der Rekuperationsstufe in der Schub-Rekuperation.
4. d) Zuletzt eine aktive Betätigung eines automatisch ansteuerbaren Bremssystems des Kraftfahrzeugs, um einen Bremseingriff zu realisieren.

For the two cases mentioned, in which problems occur with simple and remaining in freewheeling operating mode or overrun operating mode for the entire coasting operation, namely arriving too quickly at the coasting target or arriving too slowly at the coasting target, this means that to reduce the speed, for example In order to arrive at the beginning of a town more slowly or not to roll up too quickly onto a vehicle in front, the following delay-increasing measures or combinations thereof can be taken:

1. a) Automatic change from the freewheel operating mode to the overrun operating mode (same switching stage) by closing the separating clutch. This increases the drag torque.
2. b) Automatic downshift by one or two gear steps in overrun mode, so that a (further) increase in drag torque occurs.
3. c) Increase of the regenerative deceleration torque, therefore adaptation of the recuperation level in the overrun recuperation.
4. d) Finally, an active actuation of an automatically controllable braking system of the motor vehicle in order to implement a braking intervention.

Corresponding measures can also be taken in the second case, when the motor vehicle threatens to arrive too slowly at the coasting destination. For example, it is conceivable to switch back from the overrun operating mode to the freewheeling operating mode, so that the drag delay is reduced. Corrective measures of this kind are useful, for example, if they cause gradients or inclines, and it is also useful, as will be discussed in more detail below, to switch from overrun mode to freewheel mode as soon as the lower target speed is reached, and then with the least possible delay to be able to continue rolling as long as possible.

In general, it can be provided that the at least one measure assigned to a measure execution time in the action plan relates to a change in the operating state of the motor vehicle with respect to the longitudinal guidance. For the sake of explanation, it is pointed out that the two operating modes mentioned, that is, the freewheeling operating mode and the overrun operating mode, relate to the drive train of the motor vehicle, while the operating state of the motor vehicle itself is generally defined with regard to the longitudinal guidance. It therefore also includes the control of systems outside the drive train, for example a brake system and the like. In addition, in an operating state of the motor vehicle with regard to the longitudinal guidance, a distinction must also be made between different engaged shift stages in the overrun mode.

The action plan defined in this way therefore contains a chronological sequence of measures that are carried out at certain points in time to carry out the measures, in order to enable the most energy-efficient coasting process possible while achieving the target speed at the coasting target as precisely as possible. At this point it should be pointed out again that the target criterion ultimately also represents a kind of comfort criterion, since the setpoint speed at the roll-out target can often be achieved with sufficiently strong deceleration interventions, but possibly not only the efficiency, but also the driver's need for comfort with regard to the Acceptance of the driver assistance system can stand in the way.

According to the invention, the driver assistance system is combined with a function for outputting a note to terminate an operation of the accelerator pedal to a driver, so that it can therefore be provided that a determination and execution of an action plan after or without output of a note to terminate an operation of the accelerator pedal takes place to a driver, wherein the invention relates to the case of the output of information. Nevertheless, it can generally be provided that the method preferably provides for a determination and execution of an action plan both when the driver terminates the actuation of the accelerator pedal after a warning and without such a warning. The execution of the function for determining and executing the action plan after outputting a message to terminate an operation of the accelerator pedal to a driver is to be understood in such a way that the reaction of the driver, i.e. the termination of the operation of the accelerator pedal, within a predetermined time after the The message must be output, for example within 1.5-3, preferably 2, seconds, the invention providing for the waiting time since the message was output, at least before the roll-out target, to be recorded and taken into account when determining the action plan.

Nonetheless, it can be advantageous if, in the function for determining and executing the action plan, it is also taken into account whether a notification preceded within the predetermined time. The present invention provides that when determining the action plan, a maximum permitted braking deceleration and / or a maximum permitted change in the braking deceleration are taken into account. If cases with and without notice are considered, it can be provided that, when an action plan is determined without a prior output of a notice to terminate an actuation of the accelerator pedal to a driver, a lower maximum permitted braking delay and / or change in the braking delay and / or a restricted group of measures , in particular a group of measures restricted with regard to the delay options, is used as being within a predetermined time after the notification has been given. This distinction takes into account that after the output of a message to end the operation of the accelerator pedal and the corresponding reaction to it, the driver is aware that the driver assistance system is now starting a function for determining and executing the action plan, so that in this context stronger, from Driver clearly noticeable and rather tolerated due to the knowledge of the information Braking delays / other interventions can be allowed. If the function for determining and executing the action plan provided by the method according to the invention is carried out "spontaneously", i.e. outside the predetermined time after the notification has been given, the driver may not be aware of the intervention of the driver assistance system, so that with a reduced braking delay or a reduced group of measures can be worked on. Of course, since it is a comfort function, low values for the maximum permitted braking deceleration and / or the maximum permitted change in the braking deceleration can also be set overall, as already mentioned, in order to achieve rather soft and weak braking decelerations that are still below of the delays of other longitudinal driver assistance systems, for example ACC systems, are therefore known to many drivers and are rated as uncritical as automatic braking. For the maximum permitted braking decelerations, values in the range of 1.5 - 2 m / s ^{2 can be} set. As far as a reduction in the group of measures is concerned, the active use of the brake system can be limited, for example, to cases in which the driver reacts to an indication to terminate the actuation of the accelerator pedal within the predetermined time.

The invention provides that the maximum permitted braking deceleration and / or the maximum permitted change in the braking deceleration before reaching the coasting target is decreased as a function of the waiting time of the driver since the output of a message to terminate an operation of the accelerator pedal to a driver with increasing waiting time, In addition, the group of measures can be restricted as a function of the waiting time as the waiting time increases, in particular until the roll-out target is reached or until the predetermined time. This means that the later the driver follows the "foot off the gas" instruction, the lower the applicable braking deceleration or the more likely measures from the group of measures, such as a braking intervention, will be omitted. Embodiments are also conceivable in which, when the actuation of the accelerator pedal is terminated only shortly before the destination, a braking deceleration that is barely noticeable or no longer at all is implemented; In combination with different ways of determining the action plan within or after a predetermined time after the message has been issued, a steady transition can also be created, which means that when the predetermined time is reached, the lower maximum braking deceleration and / or change in the braking deceleration or reaches the restricted group of measures that are to be used after the predetermined time has elapsed, i.e. regardless of the notice. In this way, the driver is advantageously rewarded with sufficiently strong deceleration interventions if he ends the operation of the accelerator pedal early. For the driver who takes off the accelerator late, that is, after a long waiting time, a learning effect occurs, namely that prompt compliance with the instruction leads to prioritization of the target criterion that increases comfort. If the driver ends the actuation of the accelerator pedal early after an indication of the termination of an actuation of the accelerator pedal, he does not need to carry out his own corrective braking, since this is carried out by the driver assistance system for him.

In the same context, i.e. when using a maximum permitted braking deceleration and / or a maximum permitted change in the braking deceleration, a further expedient embodiment of the present invention provides that within a predetermined time after the output of a note to terminate an operation of the accelerator pedal to a Driver-triggered determination of an action plan if, within the maximum permitted braking deceleration and / or the maximum permitted change in the braking deceleration, a target speed at the coasting target, in particular the position, cannot be achieved, information in this regard, in particular a request to take over driving, is issued to the driver . In this way, a warning function is implemented that always kicks in when a target speed is not reached, so that, for example, an optical and / or acoustic request to take over the driver can be issued, which stimulates the driver to apply the necessary braking deceleration to reach the target speed make yourself. Of course, other possible outputs of information are also conceivable, for example notices of the type “Caution! Start of town ahead! Reduce speed! ”And the like.

The timely reaction of the driver to an indication to terminate the actuation of the accelerator pedal within a predetermined time or his waiting time can also have an influence on the weighting of the effectiveness criterion and the target criterion within the scope of the present invention. For example, an expedient further embodiment provides that when the operation of the accelerator pedal is terminated within or a predetermined time after a notification to terminate an operation of the accelerator pedal to a driver, the action plan is determined with greater weighting of the target criterion and otherwise with greater weighting of the effectiveness criterion he follows. The idea on which this is based is that, when taking into account the advice to terminate an operation of the accelerator pedal, the driver assumes that the target speed will also be reached at the coasting target, which means that a higher weighting can be given to it than in another case. However, if the driver takes his foot off the accelerator independently within the meaning of the invention, he may have assessed the situation differently and / or has not yet recognized the coasting target himself. In both cases, the driver does not expect the driver assistance system to reach the target speed at the coasting target, whereby in the first-mentioned case a learning effect can also occur if the driver recognizes that the target speed is not required to achieve a speed if the accelerator is released late maximum efficiency. Nonetheless, in such cases it is also expedient and sensible to increase the efficiency of the motor vehicle with regard to energy, so that the effectiveness criterion will be given greater consideration in the implementation of the action plan. Of course, it is also expediently conceivable in this context to select the weighting of the criteria as a function of a waiting time of the driver or the waiting time of the driver that has elapsed since the output of an instruction to terminate an operation of the accelerator pedal to a driver in order to implement a configuration in which the Learning effect of the driver described above in this regard can occur.

An expedient further development of the invention provides that at least one operating device is used which allows an independent activation of the instruction to terminate an operation of the accelerator pedal to a driver and the function for determining and executing the action plan. In principle, the two functions of the driver assistance system discussed here, i.e. the output of the information and the determination and implementation of the action plan, can be implemented and implemented completely independently of one another. Correspondingly, a driver can also be given the option to activate both functions independently of one another. For example, in a menu of a man-machine interface, on the one hand, a function “Advice foot off accelerator” and a function “Freewheel assistant” can be selected separately.

However, it can also be expedient in the sense of a recommendation if the function for determining and executing the action plan is automatically activated when the driver activates the instruction to terminate an operation of the accelerator pedal to a driver. The driver can of course be free to deactivate the function for determining and executing the action plan again, but it is clearly conveyed that it is useful to also have suitable operating strategies determined fully automatically. Embodiments are also conceivable within the scope of the present invention in which the function for determining and executing the action plan is inevitably activated when the function for outputting a message to terminate an operation of the accelerator pedal to a driver is activated.

Preferably, when executing an action plan without prior output of a notice to terminate an actuation of the accelerator pedal to a driver, no and / or a different status display of the driver assistance system can be output than when an action plan is determined and executed within or a predetermined time after output of a notice to terminate an operation of the accelerator pedal to a driver. Overall, it is expedient, at least after giving a message to a driver to terminate an operation of the accelerator pedal and promptly reacting by the driver within the predetermined time, to clearly indicate that the function for determining and executing the action plan has been activated and currently an action plan is performed. For this purpose, for example, a corresponding symbol can light up and / or a reference symbol for the instruction to terminate an actuation of the accelerator pedal can be added or modified. When performing the function for determining and executing the action plan without outputting a notice or after the predetermined time has elapsed after outputting a notice, it is possible, on the one hand, not to visualize the activity of the function for the driver, in particular if it is possible to intervene as described , are reduced anyway and they are barely noticeable for the driver and mainly entail an increase in the efficiency of the energy balance. However, it is also conceivable, preferably at least in the case of the different parameterization of the function discussed, depending on the notification, to use a different status display compared to the implementation of the function for determining and executing the action plan after giving a notification, so that the driver can also use the different parameterizations recognizes. If a stepless adaptation of criteria for determining the action plan is provided as a function of a time that has passed since the indication, it is of course also conceivable to reflect this in a symbol or the like.

As already mentioned, a preferred embodiment of the invention provides that an action plan is determined in which, after a coasting operating mode, a switch is made to a free-running operating mode, in particular when the coasting target is reached. If the lower target speed has been reached, for example a place name sign, a speed limit sign or the like, and the predictive route data indicate that it makes sense to maintain the target speed after the coasting destination, it is possible to switch from overrun mode to free-wheeling mode in order to achieve the lowest possible delay if possible to be able to continue rolling for a long time ("sailing"). Of course, such a measure at the roll-out target can be made dependent on the specific type of the roll-out target, for example not carried out at a roundabout. Dynamic aspects can also avoid some such switchings into the free-wheeling operating mode at the coasting destination, with, for example, switching to the free-wheeling operating mode only being able to be carried out if no other road users driving close ahead was detected and the like. Switching from the overrun mode to the free-running mode of the drive train can, however, also be expedient if, for example, a steep downhill gradient that would have accelerated the motor vehicle has ended and the like.

A particularly preferred embodiment of the present invention provides that the action plan is determined taking into account driving situation data describing the current driving situation. In this case, not only route data that write static properties of the route to the roll-out destination are used, but the current driving situation is also taken into account, i.e. the dynamic description of the route to the roll-out destination, which of course can also affect road users following the vehicle. In this way, it is also possible to react appropriately to temporary influences, which further increases the flexibility of the method according to the invention and the acceptance by the driver as well as safety and comfort.

For example, other road users, in particular road users immediately following and / or driving ahead of the motor vehicle, and / or driving situation data describing the current weather conditions and / or the current roadway condition can be used and / or the driving situation data from current sensor data from environment sensors of the motor vehicle and / or from via a motor vehicle-to-X communication, in particular a motor vehicle-to-motor vehicle communication, received communication data can be determined. Such dynamic driving situation data and their determination are already known in principle in the prior art and, within the scope of the present invention, record temporary effects and properties of the path that characterize the current driving situation.

It should be emphasized at this point that the driving situation data describing the current driving situation can also be taken into account with regard to the coasting targets. Thus, a roll-out destination can also be given by a vehicle driving ahead or generally a road user driving ahead who is moving at a slower speed (the setpoint speed) than his own motor vehicle. Such a dynamic roll-out goal would then be to have reached the target speed within a safe distance from the other road user. Such a road user driving ahead can, however, also result in a special design of the action plan for a stationary roll-out target, for example if initially stronger delays are required in order not to drive too close to the vehicle ahead, after which it is possible to switch to the free-wheeling operating mode, if necessary To be able to maintain the speed of the road user in front as long as possible and effectively in terms of energy consumption.

Driving situation data about the current weather conditions and the current state of the roadway also represent useful additional knowledge when determining an action plan. For example, if the road is currently slippery, a lower achievable deceleration of the motor vehicle can be expected; Wind influences and the like can also be relevant.

It is particularly expedient in this context if the action plan is recalculated cyclically and / or is dynamically adapted in its execution based on the driving situation data, with the currently determined action plan being carried out if a currently determined action plan deviates from the previous action plan and / or in a information in this regard, in particular a request to take over the driver, is output to the driver based on the current driving situation data, which cannot be determined. Continuous monitoring of whether the action plan is still achieving the desired goals is extremely useful for a number of reasons. On the one hand, even a deviation of the route data from reality can lead to unexpected changes in speed occurring, so that constant monitoring and, if necessary, adaptation of the action plan allows for example corrective measures. Corrective measures of this kind can be useful, for example, if the speed of one's own motor vehicle drops unexpectedly sharply during coasting, for example due to inaccuracies in the route data regarding uphill or downhill gradients and / or because estimated vehicle-dependent driving resistances were incorrectly estimated. In order to detect such deviations, it is possible, for example, to monitor whether a setpoint speed profile on which the action plan is based also corresponds to the actual speed profile of the motor vehicle.

Constant monitoring and dynamic updating of the action plan has also proven to be the case particularly useful when new information becomes known, for example a road user driving ahead is recorded for the first time and the like, which can also result in an adjustment of the action plan if this road user is (significantly) slower than your own motor vehicle.

It is also such cases in which it can mainly occur that no action plan or at least no meaningful action plan can be determined for the current driving situation data within the framework of the boundary conditions for its determination, or in other words, that a coasting process does not make any further meaningful operation of the motor vehicle. If, for example, another road user driving extremely slowly is detected who would have to be braked much more strongly than is permitted for the determination and implementation of the action plan, provision can be made to inform the driver of this and in particular to issue a request to take over the driver, which clearly indicates to the driver Indicates that, for example, you would have to brake harder. The safety offered by the driver assistance system can also be further increased in this way. In particular, with regard to a slow or decelerating vehicle in front, there can also be a kind of combination with a distance warning device, which can then also output the request to take over driving.

The driving situation data can also be used expediently in other ways, for example when an instruction to terminate an actuation of the accelerator pedal is to be output to a driver. Then, in an expedient embodiment of the invention, it can be provided that the output of the information is suppressed or delayed when a criterion from behind that evaluates the driving situation data and relates to another road user located close behind one's own motor vehicle is met. It has been shown that many drivers get an uncomfortable feeling if, during or before the start of a meaningful coasting process, a vehicle immediately following appears to be driving up close or the like. The driver of the motor vehicle can then perceive this coasting process as a type of traffic obstacle, which in operation without a driver assistance system often leads to a coasting down process being initiated significantly later or not at all. In order to map this, in those cases which are correspondingly defined by the behind-the-scenes criterion, output of the instruction to terminate the actuation of the accelerator pedal can also be suppressed or at least delayed.

It can be provided that, in order to meet the behind-the-scenes criterion, there is a relative speed of one's own motor vehicle that exceeds a threshold value to the immediately following road user and / or a distance to the immediately following road user that is below a threshold value. The question of whether a following road user can have a psychological effect on the driver of the motor vehicle can therefore be parameterized on the basis of the relative speed and / or the distance in order to obtain the criterion behind the man. This can be used to decide whether the following road user is driving too closely and / or is approaching at high speed. In this context, it is also particularly expedient if the threshold values are adapted as a function of the driving situation data and / or the route data. Because in different driving situations there are often different reactions of the driver to the following road users, which can be mapped by a corresponding dependency of the threshold values. For example, if the driver is in the right lane of a freeway, he could assume that the road user following behind will simply switch to the left lane and overtake, so that this should have little effect on his intentions with regard to the coasting process. Another case is when the motor vehicle is in the left lane of a freeway, wants to coast to a speed limit and another vehicle is approaching from behind. This and similar constellations can therefore be taken into account accordingly.

In addition to the method, the present invention also relates to a motor vehicle comprising a drive train that can be operated in a freewheeling operating mode and a driver assistance system that supports the driver during coasting and has a control unit designed to carry out the method according to the invention. All statements relating to the method according to the invention can be applied analogously to the motor vehicle according to the invention, with which the advantages already mentioned can also be achieved.

• 1 einen Ablaufplan des erfindungsgemäßen Verfahrens,
• 2 eine Möglichkeit zur Aktivierung von Funktionen eines Fahrerassistenzsystems,
• 3 eine beispielhafte Verkehrssituation,
• 4 eine Illustration eines Aktionsplans mit zugeordnetem Geschwindigkeitsverlauf und
• 5 ein erfindungsgemäßes Kraftfahrzeug.

Further advantages and details of the present invention emerge from the exemplary embodiments described below and with reference to the drawing. Show:

• 1 a flow chart of the method according to the invention,
• 2 a possibility to activate functions of a driver assistance system,
• 3 an exemplary traffic situation,
• 4th an illustration of an action plan with an assigned speed profile and
• 5 a motor vehicle according to the invention.

1 shows the flow chart of a method according to the invention for operating a driver assistance system that is intended to support the driver during coasting processes. In the present case, this driver assistance system has two functions that can basically be implemented independently of one another 1 , 2 on, taking the function 2 relates to the output of an instruction to terminate an actuation of an accelerator pedal of the motor vehicle to a driver with regard to a coasting target. The function 1 Determining and implementing an action plan involves determining a suitable operating strategy as soon as a coasting process actually begins. Of course, both functions 1 , 2 use the same algorithms and / or also exchange data, but in the present exemplary embodiment they can be activated and deactivated independently of one another by an operator, such as the output shown as an example 3 shows a man-machine interface of the motor vehicle. There are the functions 1 , 2 designated as F1 and F2, each with a checkbox 4th , 5 which can be used to activate and deactivate the respective function. In the sense of a recommendation, if the driver uses the information function 2 activated the function too 1 automatically activated to determine and implement the action plan; the driver can, however, click on the corresponding checkbox 4th switch off again if in doubt.

Since functions for outputting an instruction to terminate the actuation of an accelerator pedal to a driver are already known in principle in the prior art, the function should be referred to 2 In the present case, the function should not be discussed in more detail 1 to determine and carry out the action plan, which represents the core of the invention, are explained in more detail. However, it is with regard to the hint function 2 noted that this can also have a special feature, namely that if a traffic participant following his own motor vehicle is detected, whose driving situation data meet a behind-the-scenes criterion, the output of a message is suppressed or at least delayed. The rear man criterion evaluates the relative speed between one's own motor vehicle and the immediately following road user as well as the distance to this, whereby corresponding threshold values for fulfilling the rear man criterion can depend on the overall driving situation.

As for the function 1 , in which an optimal operating strategy for the coasting process is to be determined, is concerned in one step S1 first of all it is checked whether a coasting process is taking place at all, which means that it is detected whether the actuation of the accelerator pedal has ended. If this is the case, it becomes apparent regardless of the fact that a message is given by the function 2 , checks whether there is a coasting target with regard to which the coasting process could be carried out. On the one hand, and in the majority of cases, stationary coasting targets are conceivable, which are characterized by a position at which the motor vehicle should have a lower target speed than the current speed of the motor vehicle. Typical examples are town entrances, speed limits, curves, intersections, roundabouts and the like. The method according to the invention can, however, also be applied to dynamic coasting goals, for example coasting with regard to a vehicle traveling ahead at a slower setpoint speed.

Only if in step S2 a roll-out target has also been determined with the step S3 proceeded.

The step S3 concerns the parameterization of the in step S4 following determination of the action plan depending on whether at most a predetermined time before the detection of the termination of the operation of the power pedal in step S1 an indication by the function 2 was output as indicated by the arrow 6th is indicated.

In this regard, it should first be noted that in the present exemplary embodiment, the action plan is determined as a chronological sequence of measures that relate to a change in the operating state of the motor vehicle with regard to the longitudinal guidance, the measures being selected from a group of measures that basically activate operation of the drive train of the Motor vehicle in freewheeling mode, activation of an operation of the drive train in overrun mode, adaptation of a recuperation stage, changing a gear stage of a transmission of the motor vehicle and a braking intervention using a braking system of the motor vehicle. The freewheel operating mode means that a separating clutch is opened, which couples the drive motor to the rest of the drive train, so that there is no drag torque (or at least a reduced drag torque). Such a freewheeling operation is often referred to as sailing. If the separating clutch is closed, there is a higher drag torque due to the so-called engine brake.

The determination of the action plan, specifically the measures, is further restricted by the fact that the longitudinal guidance interventions to be carried out should be as comfortable as possible and should disturb the driver as little as possible. So one is a maximum permitted braking deceleration and a maximum permitted change in braking deceleration are provided, which should be taken into account when determining the action plan.

If the actuation of the accelerator pedal is now terminated and the coasting process is initiated within a predetermined time after the driver has been given a message to terminate the actuation of the accelerator pedal, a higher maximum permitted braking deceleration and a higher maximum permitted change are set in a first parameterization the braking delay is set and the entire group of measures is available when determining the action plan. However, if the coasting process begins without prior notification, in particular after the predetermined time has elapsed, which can be two seconds, for example, another parameterization is selected to determine the action plan in which, for example, the braking intervention is omitted as a measure and a lower maximum allowed Braking delay and a lower maximum permissible change in the braking delay are provided.

However, these aren't the only ones in step S3 parameterizations made to determine the action plan in step S4 , after an effectiveness criterion related to the energy budget of the motor vehicle and a target criterion related to the delay to the coasting target are also taken into account when it is determined. The goal criterion and the effectiveness criterion should be optimized in the context of an optimization process. The criteria mentioned are included in the optimization process, for example a cost function, with different weighting. In step S3 It is now the case that if the coasting process was started within the predetermined time after the notification was given, the target criterion is rated higher than the effectiveness criterion, since the driver expects the target speed to be reached as precisely as possible at the coasting target after the notification. If the coasting process takes place without sufficient temporal proximity to the notification or if the notification function is even deactivated, the effectiveness criterion is rated significantly higher, and more value is therefore placed on the energy efficiency when operating the motor vehicle during the coasting process.

After the determination of the action plan has been parameterized in this way, step follows S4 its first investigation. Here, as mentioned, an optimization method is used that aims at the highest possible efficiency with regard to the energy budget (effectiveness criterion) and the most precise possible achievement of the target speed at the coasting target (target criterion). The maximum permissible braking deceleration and the maximum permissible change in the braking deceleration are managed as boundary conditions; In addition, some measures are generally rated as worse, in particular the implementation of a braking intervention with the brake system, which should be avoided as far as possible. In order to find the most suitable operating strategy in the form of the action plan as part of the optimization process, in addition to the current operating status, in particular the current speed, ego data relating to the motor vehicle are used, which contain a static description of the route to the roll-out destination and which describe the current driving situation Driving situation data, i.e. a dynamic description of temporary events along the way, is taken into account. The dynamic behavior of the motor vehicle, in particular the deceleration behavior, is mapped via a dynamic model of the motor vehicle, which is also used. The route data relate to data that changes over time, if only extremely slowly, about the route ahead to the roll-out destination, in particular the route, inclines, slopes, assigned traffic rules and the like. The route data can be determined from digital map data of a navigation system of the motor vehicle and optionally from sensor data from environment data of the motor vehicle, for example sensor data from environment sensors of the motor vehicle, for example traffic sign recognition.

The driving situation data, which can also be determined from sensor data from the environment sensors, but also from communication data from the vehicle-to-X communication, relate to the description of other road users, in particular road users who are following and driving ahead of the vehicle, the current weather conditions and the current state of the road.

This input information as well as a possible in step S4 identified action plan should by the 3 and 4th be illustrated in more detail.

There is a motor vehicle according to the invention 7th on a route 8th , for example a country road shown. The roll-out goal 9 is present by a place name sign 10 marked entrance to a city. The distance and the course of the route 8th up to that point is described by the route data in the same way as an incline on the way 11 and a downhill gradient along the way 12 . The driving situation data contain information about a road user driving ahead 13 as well as one of the motor vehicle 7th following road users 14th . The driving situation data also contain the fact that a strong wind is currently blowing from behind, indicated by the arrow 15th , as possibly special conditions of the road surface, for example wetness and / or slipperiness.

4th illustrates a possible action plan for this route 8th as well as an associated speed curve 16 from the current speed 17th of the motor vehicle 7th to the target speed 18th at the roll-out target 9 .

At a time 19th (the current point in time) the action plan begins with a first measure in which the drive train of the motor vehicle 7th is switched to the free-running mode. In this it first rolls along the level route and climbs in the area 20th the gradient under the decrease in speed 11 until the variable slope 12 is achieved. The motor vehicle is threatened when the drive train is in freewheeling mode 7th now accelerating again, which is why at a time 21st the drive train is switched to the overrun mode as a further measure, initially without changing the gear stage of the transmission of the motor vehicle 7th . At the time 22nd however, if the gradient is steeper, one gear step in the transmission is downshifted, which is a further measure. After the gradient becomes a little stronger, at a point in time 23 The recuperation is also increased in order to continue a certain deceleration of the motor vehicle 7th to maintain. The slope 12 is at the time 24 ended and the drive train of the motor vehicle 7th is switched back to the freewheeling operating mode in a further measure, in which the motor vehicle 7th continue to the roll-out target 9 rolling towards. After the speed of the motor vehicle is to be reduced even further, at a point in time 25th however, once again as part of a further measure, the drive train is switched to the overrun mode, shifted up one gear step and the recuperation is reduced again in order to obtain a desired braking deceleration in such a way that at one point in time 26th upon reaching the roll-out target 9 the target speed 18th is reached. Also point in time 26th the drive train is switched back to the freewheel operating mode as the last measure of the action plan.

Obviously, this applies at all points in time 19th , 21st , 22nd , 23 , 24 , 25th and 26th the operating state of the motor vehicle 7th changes with respect to the longitudinal guide.

The implementation of the action plan begins at step S5 , however, step S6 , its further validity constantly depending on current driving situation data and the current speed of the motor vehicle 7th is monitored. If an unexpected effect occurs, for example the motor vehicle decelerating too much due to the incline 11 After this was not exactly contained in the route data, the action plan can be changed accordingly by dynamic adaptation, so that the target speed is as accurate as possible 18th is obtained. Another example of a possibly necessary adaptation of the action plan is when the driving situation data describe the motor vehicle 7th on the slower road user 13 threatens to open up. It may then be necessary to first determine the speed of the motor vehicle 7th to that of the road user 13 adapt.

If a sensible coasting process becomes impossible, for example because the speed cannot be reduced sufficiently within the boundary conditions, the speed at the coasting target is too slow 9 if there is a threat or, in any case, the driver himself has to intervene to maintain overall safety, the driver is informed of this by outputting appropriate information, in particular a request to take over the driver. For the sake of clarity, this is in 1 not shown in detail. In this way, even if the known driving situation changes, the dynamic monitoring and adaptation of the action plan in step S6 furthermore, the most effective possible operation or reaching the target speed 18th at the roll-out target 9 ensured.

In step S7 it is then checked whether the roll-out target 9 is reached. If not, the implementation of the possibly updated action plan in step S5 continued, cf. arrow 27 .

Otherwise go back to step S1 continued and checked whether a new roll-out process has been initiated.

It should also be noted at this point that the sequence of steps S1 and S2 can also be swapped if necessary.

While an action plan is being carried out, this can be communicated to the driver by means of a corresponding status display, with different status displays being used in the present exemplary embodiment depending on whether or not a message is responded to within the predetermined time. In the second-mentioned case, embodiments are also conceivable in which there is then no status display. The status display can be implemented as an extension of a symbol that is used to output the message.

5 finally shows a schematic diagram of the motor vehicle according to the invention 7th . This is indicated by the driver assistance system 28 to support the driver during a coasting process, which is carried out by means of a control unit 29 , which is designed to carry out the method according to the invention, the functions 1 and 2 can realize. To get the data you need, the control unit is 29 Connected via a bus system, for example a CAN bus or a Flex-Ray bus, to other vehicle systems that are only partially shown here. The motor vehicle also has a navigation system 30th with digital map data, a motor vehicle-to-X communication device 31 and environment sensors 32 on.

Via the control unit 29 can also, in particular via other control devices not shown here, the operating states of the motor vehicle 7th be established with respect to the longitudinal guide, there is therefore a connection to the transmission via the vehicle bus 33 , the drive motor 34 , the disconnect clutch 35 and the braking system 36 . The disconnect clutch 35 , The gear 33 and the drive motor 34 form part of the drive train of the motor vehicle 7th .

Claims (17)

Method for operating a driver assistance system (28) in a motor vehicle (7) which supports the driver during a coasting process, the drive train of which can be operated in a freewheeling operating mode in which a drive motor (34) is separated from the rest of the drive train by a disconnect clutch (35), characterized in that when the driver assistance system (28) is activated, when the driver finishes actuating the accelerator pedal and at least one potential roll-out target (9) requiring deceleration of the motor vehicle (7) is determined or known, at least one measure for targeted deceleration is determined of the motor vehicle (7) comprehensive action plan, taking into account at least one effectiveness criterion related to the energy budget of the motor vehicle (7) and a target criterion related to the delay to the roll-out target (9) as well as predictive describing the path (8) to the roll-out target (9) Route data determined and for longitudinal guidance ung the motor vehicle (7) is used, the measures being selected from a group of measures comprising at least one operation in freewheeling mode and operation in overrun mode, and the effectiveness criterion and the target criterion being used as optimization goals in an optimization process, with a determination and execution of an action plan takes place after an indication of the termination of an operation of the accelerator pedal to a driver, with a maximum permitted braking deceleration and / or a maximum permitted change in the braking deceleration being taken into account when determining the action plan, the maximum permitted braking deceleration and / or the maximum permitted change the braking delay before reaching the coasting target can be decreased as a function of the waiting time of the driver that has passed since the output of an instruction to terminate an actuation of the accelerator pedal to a driver as the waiting time increases. Procedure according to Claim 1 , characterized in that the roll-out target (9) comprises a position at which the motor vehicle (7) should have a lower target speed (18) than the current speed (17) of the motor vehicle (7). Procedure according to Claim 1 or 2 , characterized in that a further adaptation of a recuperation stage and / or a change in a gear stage of a transmission (33) of the motor vehicle (7) and / or a braking intervention using a braking system (36) of the motor vehicle (7) is used. Method according to one of the preceding claims, characterized in that the at least one measure assigned to a measure execution time (19, 21, 22, 23, 24, 25, 26) in the action plan relates to a change in the operating state of the motor vehicle (7) with respect to the longitudinal guidance. Method according to one of the preceding claims, characterized in that the group of measures is restricted as a function of the waiting time as the waiting time increases. The method according to any one of the preceding claims, characterized in that if within a predetermined time after issuing an instruction to terminate an operation of the accelerator pedal to a driver triggered determination of an action plan if within the maximum permitted braking deceleration and / or the maximum permitted change in the braking deceleration a setpoint speed (18) at the roll-out target (9), in particular the position, cannot be reached, information in this regard, in particular a request to take over driving, is output to a driver. Method according to one of the preceding claims, characterized in that when the actuation of the accelerator pedal is terminated within the or a predetermined time after a notification to terminate an actuation of the accelerator pedal to a driver, the determination of the action plan with greater weighting of the target criterion and otherwise with greater weighting of the effectiveness criterion. Method according to one of the preceding claims, characterized in that at least one operating device, which is an independent Activation of the notice for ending an operation of the accelerator pedal to a driver and the function (1) for determining and executing the action plan is used. Procedure according to Claim 8 , characterized in that when the driver activates the function (2) for outputting the instruction to terminate an operation of the accelerator pedal to a driver, the function (1) for determining and executing the action plan is automatically activated. Method according to one of the preceding claims, characterized in that an action plan is determined in which, after a coasting operating mode, a switch is made to a free-running operating mode, in particular when the coasting target (9) is reached. Method according to one of the preceding claims, characterized in that the action plan is determined taking into account driving situation data describing the current driving situation. Procedure according to Claim 11 , characterized in that further road users (13, 14), in particular the motor vehicle (7) directly following and / or driving ahead road users (13, 14), and / or driving situation data describing the current weather conditions and / or the current road condition are used and / or the driving situation data is determined from current sensor data from environment sensors (32) of the motor vehicle (7) and / or from communication data received via a motor vehicle-to-X communication. Procedure according to Claim 11 or 12 , characterized in that the action plan is re-determined cyclically and / or is dynamically adapted when it is executed on the basis of the driving situation data, with the currently determined action plan being carried out if a currently determined action plan deviates from the previous action plan and / or in the case of one based on the current driving situation data A current action plan that cannot be determined, a related information, in particular a driver takeover request, is issued to the driver. Method according to one of the Claims 11 to 13 , characterized in that, when a message about the termination of an operation of the accelerator pedal is to be output to a driver, the output of the message is suppressed or delayed if another road user (who is evaluating the driving situation data) and who is located close behind his own motor vehicle (7) ( 14) the relevant rear man criterion is met. Procedure according to Claim 14 , characterized in that in order to meet the behind-the-scenes criterion there is a relative speed of one's own motor vehicle (7) exceeding a threshold value to the immediately following road user (14) and / or a distance below a threshold value from the immediately following road user (14). Procedure according to Claim 13 , characterized in that the threshold values are adapted as a function of the driving situation data and / or the route data. Motor vehicle (7), comprising a drive train that can be operated in a freewheeling operating mode and a driver assistance system (28) which supports the driver during coasting and has a control device (29) designed to carry out a method according to one of the preceding claims.

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