WO2015120872A1 - Method for operating a driver assistance system which provides assistance to the driver during a roll-over process, and motor vehicle - Google Patents

Abstract

Method for operating a driver assistance systems (28), which provides assistance to the driver during a roll-over process, in a motor vehicle (7), the drivetrain of which can be operated in a free-wheeling operating mode in which a drive engine (34) is disconnected from the rest of the drivetrain by a clutch (35), wherein when the driver assistance system (28) is activated and the driver ends activation of the accelerator pedal and at least one potential coasting destination (9) which requires deceleration of the motor vehicle (7), is determined or known, an action plan which comprises at least one measure for the targeted deceleration of the motor vehicle (7) is determined taking into account at least one effectiveness criterion relating to the energy balance of the motor vehicle (7) and a destination criterion relating to the deceleration with respect to the coasting destination (9), as well as predictive distance data describing the distance (8) to the coasting destination (9), and said action plan is used for performing longitudinal guidance of the motor vehicle (7), wherein the measures are selected from a measure group comprising at least one operation in the free-wheeling operating mode and operation in an overrun operating mode.

Description

 Method for operating a driver assistance system and motor vehicle supporting the driver during a deployment process

The invention relates to a method for operating a driver assist system assisting the driver in a coasting operation 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 separating clutch. In addition, the invention relates to a motor vehicle.

Motor vehicles have already been known in the prior art whose drive train has a freewheeling operating mode (also called a sailing operating mode). When freewheeling or sailing the motor vehicle, the frictional connection between the transmission and the drive motor is interrupted by a disconnect clutch, so that an extremely efficient operating state of the motor vehicle is given, in which this is braked by less friction effects. The separating clutch can be addressed by a control unit, such as a transmission control unit or an engine control unit, to be opened when needed.

Automatic activation of the freewheeling operation mode usually takes place in the prior art when the driver terminates an actuation of the accelerator pedal. Vehicle systems are known in which the driver can decide for himself whether the freewheeling operating mode is activated after the actuation of the accelerator pedal, ie the traction between the transmission and the drive motor is interrupted, or whether a coasting operating mode in which the disconnect clutch remains closed is activated. For example, via a suitable operating device, a special drive mode, for example an efficiency mode or a sailing mode, can be activated. It was also proposed to make an additional decision in an internal gear function even with activated coasting function, whether the freewheeling mode is actually released or should be disabled depending on the driving situation, for example in stronger gradients / gradients, high lateral acceleration, high accelerator gradient and the like where locking the freewheel mode may increase safety.

There have already been proposed a rollover-related driver assistance systems that can be provided independently of the availability of a freewheeling operation mode. Such driver assistance systems detect potential coasting targets that are lying ahead on the route, in particular, locations in which the motor vehicle should have a lower speed than the current speed. For this purpose, route data are used, which can originate from different sources, for example from navigation data, traffic sign recognition and the like. Possible coasting destinations that include a lower target position position include, for example, city entrances, speed limits, intersections and roundabouts, uphill / downhill gradients, bends, and the like.

If such a coasting target has been detected, taking into account route data describing the route up to the coasting destination, a point of time may be determined which is suitable, when the driver at that time ends the operation of the accelerator pedal, to cause the target speed to reach the coasting destination becomes. If the freewheeling mode is automatically activated at the end of the operation of the accelerator pedal, this time is often much earlier than when the motor vehicle in overrun mode, where the engine brake also acts accordingly. Known in the prior art driver assistance systems now provide, at the time or shortly before the time a message to end an operation of the accelerator pedal, for example, "foot off the gas" to issue the driver, so that in accordance timely implementation of this proposal and correct Route data with the roll-out destination the local target speed can be achieved easily and highly efficiently. It should be noted that such a "foot of the gas" indication can often be given much earlier than a driver would end the operation of the accelerator from his personal assessment.

As already mentioned, self-propelled vehicles ("sailable"), in which the separating clutch between the engine and the transmission is opened in the coasting process, are in many cases more energy-efficient.The motor vehicle rolls significantly better and further due to reduced driving resistances 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 coasting mode of operation, it should be noted that the decision as to whether the coasting mode of operation or a coasting mode is selected often depends only on a driver's attitude. With regard to quantities describing the current driving situation, the decision can be changed on the part of the drive if this is expedient for safety reasons. With regard to the aforementioned coasting events, the decision as to whether the coasting mode of operation or a coasting mode is active is not changed during the complete coasting operation.

With regard to the driver assistance systems, which output instructions for the termination of an actuation of the accelerator pedal to the driver, it should be noted that the acceptance and the frequency of use of such information functions strongly depends on how the coasting behavior of the motor vehicle is dependent on the distance and driving situation. Such a pure hint function will only be 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 critical watching mode after the completion of the operation of the accelerator pedal. In particular, the course of the speed must be such that the driver still feels comfortable and does not immediately intervene again by operating the accelerator pedal or by braking. In principle, two cases are conceivable in which problems can occur in driver assistance systems with a function to take the foot off the gas. On the one hand, it may happen that the arrival speed at the position at which the target speed is to be present is even higher than the setpoint speed. This can occur, for example, when a drop occurs before the roll-out target as a speed limit event. Then, the driver, who has followed an early warning to end the operation of the accelerator pedal, surprisingly has to apply a braking intervention to correct the vehicle speed. Also, the coasting speed may suddenly be considered too high when a slower vehicle is in front of the own motor vehicle. Again, the driver has to intervene to brake.

It is also possible, however, that the speed is too low when reaching the Ausrollziels, so that the driver may feel like a traffic obstacle. This feeling intensifies when another road user drives behind his own motor vehicle and approaches, for example.

An essential problem in driver assistance systems with such information functions is that ultimately the point in time at which the driver actually stops the operation of the accelerator pedal is scarcely predestinable. For example, if a driver waits several seconds before responding to a "foot-from-gas" alert, the coasting strategy identified and subsequently implemented there can no longer be successfully implemented and, in particular, result in too high a speed at the coast target An information function is not given or can be realized by the driver in today's driver assistance systems.

DE 10 2011 083 013 A1 describes a driver assistance system, which determines an earliest possible time to start a coasting process, and the latest possible time to start a braking process, and the concrete time for issuing an indication to the Driver to start a coasting, driver-individual chooses. Thus, a better acceptance of the driver assistance system should be ensured. However, a problem of the driver assistance system there is that drivers, as already mentioned, often begin a coasting process significantly too late, in order to achieve the coasting target with the setpoint speed desired there in the continuous coasting operating mode or coasting operating mode. Therefore, it is necessary there after the completion of the coasting process to brake specifically to the target speed. However, this does not adequately exploit the efficiency possibilities due to coasting processes.

The invention is therefore an object of the invention to provide a function for the driver during a Ausrollvorgang supportive driver assistance system that allows maximum benefit of Ausrollvorgangs with high acceptance by the driver.

To solve this problem, it is provided according to the invention in an activated driver assistance system, when the driver stops an operation of the accelerator and at least one potential, a deceleration of the motor vehicle required Ausrollziel is determined or known, at least one measure to. specific delay plan of the motor vehicle comprehensive action plan, taking into account at least one on the energy balance of the motor vehicle related effectiveness criterion and on the delay to the Ausrollziel related target criterion and from the way to the Ausrollziel descriptive predictive track data determined and used for longitudinal guidance of the motor vehicle, the Measures are selected from at least one operation of the drive train in the freewheeling operation mode and an operation of the drive train in a coasting mode comprehensive action group.

In this case, in most cases, it will be the case that the coasting target comprises a position at which the motor vehicle should have a lower target speed than the current speed. Such, for example, from digital map data of a navigation system and / or sensor data, For example, a traffic sign recognition, derived Ausrollziele may include, for example, the beginning of a reduced speed route, for example, a corresponding road sign or a city entrance, a curve that must be traversed 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 a termination of the operation of the accelerator pedal by the driver. Consequently, the method according to the invention initially works independently of any one, as will be discussed in greater detail below, an indication function that assists the driver, albeit possibly in a modified manner, ie even if he takes his foot off the gas without a previous notice the operation of the accelerator pedal is terminated in order to achieve an improved energy efficiency and an improved achievement of the target speed at the coasting target, thus the position contained. The proposed driver assistance system thus also makes it possible to assist the driver if he has not requested any instructions.

This is advantageously realized in that a specific operating strategy of the motor vehicle is selected, which is represented by the measures for delaying the motor vehicle comprehensive action plan. In other words, the method according to the invention determines a predictive coasting operating strategy for free-running motor vehicles, which does not simply either selectively set the free running mode or the overrun operating mode and maintain it to the coasting target, as is usual in the prior art, but rather measures contains for switching between several related to the longitudinal guidance of the motor vehicle operating conditions, for example, so can switch between a freewheeling operation mode and a coasting mode, so that the highest possible efficiency and the most accurate reaching the target speed are 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 coasting target, therefore set the optimization goals in an optimization tion procedure, which, as will be described in more detail below, can be taken into account, for example, weighted in a cost function. The optimization method for determining the measures of the action plan therefore utilizes the predictive route data in order to achieve the highest possible energy efficiency and a delay as close as possible to the setpoint speed.

It should be noted that the route data represent a static description of the previous path to Ausrollziel, so in particular may include the course, gradients, gradients, road surface and the like. In the context of the present invention, a dynamic description of the preceding path to the coasting target can also be considered with particular preference, which will be discussed in more detail below. As already mentioned, predicted route data are usually derived from digital map data of a navigation system of the motor vehicle, but may also contain information derived from sensor data from environment sensors of the motor vehicle. The predictive trail data may also have already served to determine the coast target.

In addition to the predictive route data, of course, also the current operation of the motor vehicle descriptive Egodaten be considered, for example, its already mentioned current speed and the properties of the motor vehicle, which can be mapped, for example, in a to be used in the determination of the action plan dynamic model of the motor vehicle.

The dynamics model of the motor vehicle in this case provides the ability to determine for certain characteristics of the route ahead, how strong the braking deceleration is in different operating states of the motor vehicle, for example, in the pure freewheeling mode of the drive train and at different engaged shift stages of a transmission in the overrun mode of the drive train. Such dynamics models are already known in the art and need not be detailed here. If a braking deceleration is mentioned in the context of the present invention, this refers to any effects which slow the motor vehicle, thus not exclusively to brake interventions, but also, for example, to deceleration-induced deceleration effects and the like.

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

Here, a preferred embodiment of the present invention provides that a further adaptation of a Rekuperationsstufe and / or changing a switching stage of a transmission of the motor vehicle and / or a braking system of the motor vehicle using braking intervention comprehensive set of measures is used. It should be noted at this point that an actual braking intervention should be avoided as far as possible by the driver least accepted measure, for example, can be assessed as extremely poor in an optimization process. In order to reduce the speed of the motor vehicle, it is thus possible to use certain deceleration-increasing or deceleration-reducing measures in the action plan, which are defined by a group of measures. One of these measures, which is possible in any case, is the automatic changeover between the freewheeling operation mode and the thrust operating mode of the drive train by closing or opening the separating clutch. If the design of the separating clutch permits this, a slipping separating clutch for producing intermediate states within the scope of the present invention is also conceivable. Other measures to influence the braking deceleration of the motor vehicle include, for example, the conversion switch between different switching stages of the transmission of the motor vehicle, so that an increase or decrease in the drag torque (engine brake) follows. In motor vehicles with an electrified drive, such as a belt starter generator and / or an electric drive motor, an increase and / or decrease of the regenerative deceleration torque can lead to a suitable adjustment of the deceleration, thus changing the Rekuperationeinstellungen. Finally, as a measure also conceivable to control an automatically controllable braking system for performing a braking operation. However, this last possible measure is less preferred, since it is a general objective of the delay regulation and the identification of the action plan that the delay interventions are only perceived as slightly correcting, so that on the one hand the driver does not feel patronized / disturbed, on the other hand There is no expectation that the driver assistance system always decelerates sufficiently and reliably in order to actually reach the setpoint speed, which is not always possible in a sensible manner, especially when the coasting process is initiated late by the driver's termination of the accelerator pedal. The permission to use brake interventions with a brake system can also be coupled to an advisory function, so that, for example, a measure of the braking system of the motor vehicle for performing a braking intervention can only be allowed if the driver an indication to end the operation of the accelerator in time within a predetermined time, for example 2 seconds, following the indication.

For the two cases mentioned, where in simple and remaining in the freewheeling operation or overrun operating mode for the entire coasting process operating problems occurring problems, namely arrive too fast at the coasting or arrive too slowly at the coasting, this means that to reduce the speed, for example in order to arrive slower at the beginning of a town or not to roll up too fast onto a preceding vehicle, the following deceleration measures or combinations thereof may be made:

a) Automatic change from the freewheeling operation mode to the overrun operating mode (same switching stage) by closing the separating clutch. In this way, the drag torque increases.

b) Automatic downshift by one or two shift stages in coasting mode, so that a (further) increase in the drag torque occurs.

c) Increasing the regenerative deceleration torque, thus adaptation of the recuperation stage in the thrust recuperation.

d) Finally, an active actuation of an automatically controllable braking system of the motor vehicle in order to realize a braking intervention.

Also in the second case, so if the motor vehicle threatens to arrive too slowly at the coasting, appropriate measures can be carried out. For example, it is conceivable to switch back from the overrun mode to the free-wheeling mode, so that the drag delay is reduced. Such corrective measures are useful, for example, if this causes inclines or gradients, and it is also useful, as will be discussed in greater detail, to switch from the overrun mode to the free-wheeling mode as soon as the lower setpoint 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 of the operating state of the motor vehicle with respect to the longitudinal guide. It should be noted that the two operating modes mentioned, ie the freewheeling operation 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 respect to the longitudinal guide. It therefore also includes the control of systems outside the drive train, for example a brake system. tems and the like. In addition, in the case of an operating state of the motor vehicle with respect to the longitudinal guide, it is also possible to distinguish between different engaged shift stages in the overrun operating mode.

The action plan thus defined thus contains a chronological sequence of measures which are carried out at specific measures execution times in order to enable the most energy-efficient coasting operation with as accurate as possible achievement of the target speed at the coasting target. It should be pointed out again at this point that the target criterion ultimately represents a kind of comfort criterion, as over sufficiently strong deceleration the target speed at the coasting is often quite achievable, but possibly not only the efficiency, but also the comfort need of the driver in terms of Can oppose acceptance of the driver assistance system.

As already mentioned, the driver assistance system can certainly be combined with a function for outputting an instruction for ending an actuation of the accelerator pedal to a driver, so that provision can then be made for a determination and execution of an action plan after or without an output of an indication Termination of an operation of the accelerator pedal to a driver takes place. This is emphasized on the one hand again that the inventive method preferably provides for a determination and execution of an action plan both when the driver stops the operation of the accelerator pedal after a note, as well as without such an indication. In this case, the execution of the function for determining and implementing the action plan after issuing an instruction to end an operation of the accelerator pedal to a driver is to be understood that the driver's reaction, ie the termination of the operation of the accelerator pedal within a predetermined time after the Issue of the hint must be made, for example, within 1, 5 - 3, preferably 2, seconds, and it is also conceivable to record the waiting time since the notice, at least before the roll-out, and taken into account in the determination of the action plan. Nevertheless, it may be advantageous if the function for determining and implementing the action plan also takes into account whether an indication preceded within the predetermined time, so that a particularly preferred embodiment of the present invention provides that when determining the action plan, a maximum allowable Brake delay and / or a maximum allowable change in braking deceleration are taken into account when determining an action plan without a previous issue of a notice to end an operation of the accelerator pedal to a driver lower maximum allowable braking delay and / or change the braking deceleration and / or a limited A set of measures, in particular a set of measures limited in terms of delay options, is used as within a predetermined time after the note has been given. This distinction contemplates that upon issuing an indication to end actuation of the accelerator pedal and corresponding response to it, the driver is aware that the driver assistance system now launches a function to identify and execute the action plan, so that in this context also stronger ones from the Driver clearly noticeable and due to the knowledge of the hint rather tolerated braking delays / other interventions may be allowed. If the function for determining and implementing the action plan which provides the method according to the invention is carried out "spontaneously", ie 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 deceleration In this case, of course, even after being a comfort function, low values for the maximum permitted braking deceleration and / or the maximum permitted change in braking deceleration can be used, as already mentioned To realize weak braking decelerations that are still below the delays of other longitudinal driver assistance systems, such as ACC systems, are therefore known to many drivers and are rated as automatic braking as uncritical permitted braking delays can have values in Range of 1, 5 - 2 m / s ² are used. As far as a reduction of the set of measures is concerned, the active use of the braking system may be limited, for example, to cases where the driver reacts within the predetermined time to an instruction to end the operation of the accelerator pedal.

Alternatively or at longer predetermined times in combination may be provided when using a maximum allowable braking deceleration and / or a maximum allowable change in braking deceleration that the maximum allowable braking deceleration and / or the maximum allowable change in deceleration before reaching the coasting target in dependence the output of a notice to end an operation of the accelerator pedal to a driver past waiting time of the driver with increasing waiting time are lowered and / or the set of measures depending on the waiting time is limited with increasing waiting time, in particular until reaching the coasting target or until the predetermined time. This means that the later the driver follows the "foot-from-gas" instruction, the lower the applicable braking deceleration or the sooner measures fall away from the set of measures, for example a braking intervention Completion of the operation of the accelerator pedal just before the target a barely noticeable or no braking deceleration is more realized, in combination with different ways of determining the action plan within or after a predetermined time after issuing the hint, a steady transition can be created that is, when the predetermined time is reached, exactly the lower maximum braking deceleration and / or change of the braking deceleration or the restricted set of measures is to be used, which are to be used after the predetermined time has elapsed, that is to say independently of the reference Driver by adequate strong deceleration interventions will reward you if you stop pressing the accelerator early. For the late-driver, ie after a long wait, the driver, who is accelerating from the gas, experiences a learning effect, namely that a timely adherence to the instruction leads to a comfort-enhancing prioritization of the target criterion. The driver ends the operation of the accelerator early after an indication to end an operation of the accelerator pedal, he does not need to perform their own correction braking, as this performs the driver assistance system for him.

In the same context, ie when using a maximum allowable braking deceleration and / or a maximum allowable change in braking deceleration, provides a further advantageous embodiment of the present invention, that within a predetermined time after issuing a notice to end an operation of the accelerator to a Driver triggered determination of an action plan, if within the maximum allowed braking deceleration and / or the maximum allowed change in braking deceleration a target speed at the coasting target, in particular the position can not be achieved, an output of this information, in particular a Fahrübernahmeaufforderung to the driver , In this way, a warning function is realized, which always starts when a target speed is not reached, so that, for example, a visual and / or acoustic Fahrübernahmeaufforderung can be issued, which stimulates the driver, the necessary braking deceleration to reach the target speed to produce yourself. Of course, other possible releases of information are also conceivable, for example notes of the type "Attention! Beginning of town ahead! Reduce speed! "And the like.

The timely response of the driver to an indication of the end of operation of the accelerator pedal within a predetermined time or its waiting time may also have an influence on the weighting of the effectiveness criterion and the target criterion in the context of the present invention. Thus, an expedient further embodiment provides that at a termination of the operation of the accelerator pedal within or a predetermined time after an indication to end an operation of the accelerator to a driver, the determination of the action plan under stronger weighting of the target criterion and otherwise under greater weighting of the effectiveness criterion he follows. The underlying idea is that, taking into account the advice to stop operating the gas Pedals the driver rather assumes that the target speed at the Ausrollziel is also achieved, this can therefore be given a higher weighting than in another case. However, if the driver independently takes his foot off the gas pedal in the sense 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 to the driver assistance system is not expected to reach the target speed at the Ausrollziel, in the former case, a learning effect may occur when the driver recognizes that the target speed at a late gas takeoff not to achieve a maximum efficiency. Nevertheless, it is appropriate and useful in such cases to increase the efficiency of the motor vehicle with regard to energy, so that here the effectiveness criterion will find greater consideration in the implementation of the action plan. Of course, it is also conceivable in this context to choose the weighting of the criteria depending on one or the since the issue of an indication for the termination of an operation of the accelerator pedal to a driver past waiting time of the driver to realize an embodiment in which above described in this regard learning effect of the driver can occur.

An expedient development of the invention provides that at least one operating device, which allows an independent activation of the indication for the termination of an operation of the accelerator pedal to a driver and the function for determining and executing the action plan, is used. In principle, the two functions of the driver assistance system discussed here, ie the output of the hint and the determination and execution of the action plan, can be implemented and implemented completely independently of one another. Accordingly, a driver can also be released independently of the activation of both functions. For example, in a menu of a human-machine interface, on the one hand, a function "footer off gas" and a function "freewheeling assistant" can be selected separately. However, in the sense of a recommendation, it may also be useful if the function for determining and executing the action plan is automatically activated when the driver is informed of the end of an operation of the accelerator pedal to a driver. Of course, the driver may be free to deactivate the function for determining and executing the action plan, but it is clearly conveyed that it is expedient to have suitable operating strategies also 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 without driver's choice is inevitably activated upon activation of the function for outputting an instruction for ending an actuation of the accelerator pedal to a driver.

Preferably, in an execution of an action plan without prior issuance of an instruction to end an operation of the accelerator pedal to a driver, no and / or another status indication of the driver assistance system can be issued as in a determination and execution of an action plan within or a predetermined time after issuing an indication to terminate an operation of the accelerator pedal to a driver. Overall, it is expedient, at least after giving an indication for the termination of an operation of the accelerator pedal to a driver and timely reaction of the driver within the predetermined time to clearly indicate that the function has been activated to identify and execute the action plan and just an action plan is performed. For this purpose, for example, a corresponding symbol can light up and / or a hint symbol of the instruction for completing an actuation of the accelerator pedal can be supplemented or modified. When performing the function for determining and executing the action plan without issuing an indication or after elapse of the predetermined time after issuing an indication, it is possible, on the one hand, not to visualize the activity of the function to the driver, in particular if their intervention possibilities were described as described above are anyway reduced and they bring little noticeable to the driver mainly an increase in the efficiency of the energy balance. Conceivable However, it is also preferred, in any case in the discussed different parameterization of the function depending on the indication, to use a different status display compared to the execution of the function for determining and implementing the action plan after the indication has been given, so that the driver also recognizes the different parameterizations , If an infinite adaptation of criteria for determining the action plan is provided in dependence on a time that has elapsed since the reference, it is of course also conceivable to reproduce 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, the vehicle is switched to a coasting operating mode, in particular when the coasting target is reached. When the lower target speed is reached, for example, a town sign, a speed limit sign, or the like, and the predictive distance data indicates that it is reasonable to keep the target speed after the coast target, it is possible to switch from the coast mode to the coast mode to continue with as little delay as possible Of course, such a measure at the coast down target may be made dependent on the particular type of coast down target, for example, not performed at a roundabout.Similar aspects may also avoid some such switching to the coasting mode at the coast down destination. wherein, for example, switching to the freewheeling operating mode can only be carried out if no closely preceding further road user has been detected, and the like However, rubbing mode of the drive train may also be useful if, for example, a greater gradient that would have accelerated the motor vehicle is completed 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 So not only static properties of the way to the Ausrollziel writing track data used, but it is also the current driving situation taken into account, hence the dynamic description of the way to Ausrollziel, which of course may affect the motor vehicle following road users. In this way, it is therefore also possible to react appropriately to transient influences, which further increases the flexibility of the method according to the invention and the driver's acceptance as well as safety and comfort.

In this case, for example, further road users, in particular the motor vehicle immediately following and / or driving ahead road users, and / or the current weather conditions and / or the current road condition descriptive driving situation data can be used and / or the driving situation data from current sensor data from environment sensors of the motor vehicle and / or from about a vehicle-to-X communication, in particular a motor vehicle-to-vehicle communication, received communication data are determined. Such dynamic driving situation data and their determination are already known in principle in the prior art and, in the context of the present invention, capture transient effects and properties of the route which 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 considered with regard to the coasting targets. Thus, a Ausrollziel may well be given by a leading vehicle or generally a leading road user, which moves at a slower speed (the target speed) than the own motor vehicle. Such a dynamic Ausrollziel would then have reached the target speed at a safe distance from the other road users. However, such an advanced road user can also result in a special design of the action plan for a stationary coasting target, if, for example, stronger delays are initially required so as not to drive too close to the vehicle in front, where may then be switched to the freewheeling operation mode, if necessary, in order to keep the speed of the leading road user possible long and effectively, as far as the energy balance is concerned.

Also, driving situation data on the current weather conditions and the current road condition represent useful additional knowledge in the determination of an action plan. For example, if the road is currently smooth, can be expected with a lower achievable delay of the motor vehicle; Wind influences and the like can also be relevant.

In this connection, it is particularly expedient if the action plan is cyclically re-determined and / or adapted dynamically on the basis of the driving situation data, whereby the currently determined action plan is carried out and / or at a deviation from a currently determined action plan from the previous action plan On the basis of the current driving situation data can not be determined current action plan information in this regard, in particular a Fahrübernahmeaufforderung is issued to the driver. Constant monitoring of whether the action plan still leads to the desired goals is extremely useful for a variety of reasons. On the one hand, a deviation of the route data from the reality can lead to unexpected speed changes, so that a constant monitoring and, if necessary, adaptation of the action plan, for example, allows corrective measures. Such corrective measures may be useful, for example, when the speed of the own motor vehicle drops unexpectedly sharply during the coasting process, for example due to inaccuracies in the route data, regarding inclines or inclines and / or because estimated vehicle-dependent driving resistances were misjudged. In order to detect such deviations, it is possible, for example, to monitor whether a target speed profile underlying the action plan also corresponds to the actual speed profile of the motor vehicle. Continuous monitoring and dynamic updating of the action plan also proves to be particularly useful when new information becomes known, for example a driving road user is detected for the first time and the like, which may also result in an adaptation of the action plan if this road user (clearly) slower than your own car.

It is also such cases where it can mainly occur that for the current driving situation data no action plan or at least no sensible action plan can be more determined within the framework conditions for its determination, or in other words that a coasting process does not make any further meaningful operation of the motor vehicle represents. If, for example, an extremely slow-moving further road user is detected, which would have to be braked considerably more than permitted for the determination and implementation of the action plan, it may be provided to inform the driver and, in particular, to issue a drive-over request that clearly informs the driver Note that, for example, would have to be braked more. Even so, the safety provided by the driver assistance system can be further increased. In particular, with regard to a slow or decelerating front vehicle, there may also be a kind of combination with a distance warning, which can then also output the driving-acceptance request.

The driving situation data can also be used meaningfully in other ways, for example, when an indication for the termination of an operation of the accelerator pedal is to be output to a driver. Then, in an expedient embodiment of the invention, it may be provided that the output of the indication is suppressed or delayed when a background criterion evaluating the driving situation data and having a further traffic participant close behind the own motor vehicle is met. It has been shown that many drivers get an uncomfortable feeling if, during or before the start of a sensible coasting operation, a vehicle following immediately behind them starts up tightly seems or the like. Then the driver of the motor vehicle can interpret this coasting process as a kind of traffic obstruction, which in an operation without driver assistance system often leads to a coasting process being initiated significantly later or not at all. To illustrate this, in such cases, which are defined in accordance with the Hintermannkriterium, an output of the hint to end the operation of the accelerator pedal also suppressed or at least delayed.

It can be provided that to meet the Hintermannkriteriums a threshold exceeding relative speed of the own motor vehicle to the immediately following road users and / or a threshold below the distance to the immediately following road users present. 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 Hintermannkriterium. Thus, it can be decided whether the following road user ascends too close and / or approaches at high speed. Incidentally, it is particularly useful in this context if the threshold values are adapted as a function of the driving situation data and / or the route data. For 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 on the right lane of a freeway, he or she may assume that the following road user will simply evade and overtake on the left lane, so this may have little effect on his intentions regarding the coasting process. Another case is when the motor vehicle is in the left lane of a highway, wants to roll on a speed limit and another vehicle approaches from behind. These 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 drivetrain operable in a freewheeling operating mode and a driver assistance system assisting the driver during a coasting process with a control device designed to carry out the method according to the invention. All statements relating to the method according to the invention can be analogously transferred to the motor vehicle according to the invention, with which therefore the already mentioned advantages can also be achieved.

Further advantages and details of the present invention will become apparent from the embodiments described below and with reference to the drawing. Showing:

1 is a flowchart of the method according to the invention,

2 a possibility for activating functions of a driver assistance system,

3 shows an exemplary traffic situation,

Fig. 4 is an illustration of an action plan with associated speed history and

5 shows a motor vehicle according to the invention.

1 shows the flowchart of a method according to the invention for operating a driver assistance system intended to assist the driver during coasting operations. In the present case, this driver assistance system has two functions 1, 2 that can basically be implemented independently of one another, wherein the function 2 relates to the output of an indication for the termination of an actuation of an accelerator pedal of the motor vehicle to a driver with regard to a coasting target. Function 1, which identifies and implements an action plan, concerns the identification of an appropriate operational strategy as soon as a coasting process actually begins. Of course, NEN the two functions 1, 2 use the same algorithms and / or exchange data, but in the present embodiment by an operator independently activated and deactivated, as shown by way of example output 3 shows a human-machine interface of the motor vehicle. There are the functions 1, 2 referred to as F1 and F2, each with a checkbox 4, 5 shown, via which the respective function can be activated and deactivated. In the sense of a recommendation, if the driver activates the notification function 2, the function 1 for determining and implementing the action plan is automatically activated as well; However, the driver can turn it off by clicking on the corresponding checkbox 4 in case of doubt. ,

After functions for outputting an indication for the termination of the operation of an accelerator pedal to a driver in the prior art are already known in principle, should not be discussed in more detail in the present function 2, but it is the function 1 for determining and implementing the action plan, the Core of the invention is illustrated in more detail. However, it should be noted with regard to the hint function 2 that this too may have a special feature, namely that when a road user following the own motor vehicle is detected whose driving situation data fulfill a Hintermann criterion, the output of an indication is suppressed or at least delayed. The Hintermannkriterium evaluates the relative speed between the own motor vehicle and the immediately following road users and the distance to this, with corresponding thresholds to fulfill the Hintermannkriteriums of the overall driving situation may be dependent.

As for the function 1 in which an optimum operation strategy for the coasting operation is to be detected, it is first checked in a step S1 whether there is any coasting operation, that is, it is detected whether there is an end of the operation of the accelerator pedal. If this is the case, it is checked, independently of the gift of a hint by the function 2, whether there is a coasting target, with regard to which the rolling process could be done. Here, on the one hand and in the majority fixed stationary rolling goals 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 include town entrances, speed limits, bends, intersections, roundabouts, and the like. However, the method according to the invention can also be applied to dynamic coasting targets, for example rolling out with regard to a vehicle driving ahead at a slower setpoint speed.

Only if a coasting target has also been determined in step S2, then step S3 is continued.

The step S3 relates to the parameterization of the following determination of the action plan in step S4 depending on whether at most a predetermined time before the detection of the termination of the operation of the force pedal in step S1 an indication was issued by the function 2, as indicated by the arrow. 6 is hinted at.

It should first be noted that in the present embodiment, the action plan as a time sequence of measures that affect a change in the operating state of the motor vehicle with respect to the longitudinal guidance is determined, the measures are selected from a set of measures that basically activation of operation of the powertrain of the Motor vehicle in the freewheeling operation mode, an activation of an operation of the drive train in a coasting mode, an adjustment of a Rekuperationsstufe, changing a shift stage of a transmission of the motor vehicle and a brake system of the motor vehicle utilizing brake engagement. The free-running mode means that a disconnect clutch is opened, which couples the drive motor to the rest of the drivetrain, so that no drag torque (or at least a reduced drag torque) is given. Such a freewheeling operation is often referred to as sailing. Is the separating clutch concluded, there is a higher drag torque through the so-called engine brake.

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

Now, if the completion of the operation of the accelerator pedal and thus the initiation of the coasting within a predetermined time after the presentation of an instruction to end the operation of the accelerator pedal to the driver, so in a first parameterization, a higher maximum allowable braking deceleration and a higher maximum allowable change The braking delay is set and the entire set of measures is available when the action plan is determined. However, if the start of the coasting process takes place without prior notification of an indication, in particular after expiration of the predetermined time, which may be, for example, two seconds, a different parameterization for determining the action plan is selected in which, for example, the braking intervention is omitted as a measure and a lower maximum allowed Braking delay and a lower maximum allowable change in the braking deceleration are provided.

However, these are not the only parameterizations made in step S3 of determining the action plan in step S4, after its determination also takes into account an efficiency criterion related to the energy balance of the motor vehicle and a target criterion related to the deceleration to the coasting target. The goal criterion and the effectiveness criterion should be optimized as part of an optimization process. The criteria mentioned enter into the optimization process with different weighting, for example a cost function. In step S3, if the coasting operation has started within the predetermined time after the indication of the indication, then Target criterion is rated higher than the effectiveness criterion, since the driver expects after the indication the most accurate reaching the target speed at the coasting target. If the coasting process without sufficient temporal proximity to the hint or the hint function is even disabled, the effectiveness criterion is rated significantly higher, it is therefore more emphasis on energy efficiency during operation of the motor vehicle during the Ausrollvorgangs.

After the determination of the action plan has been parameterized in this way, in step S4 the first determination follows. Here, as mentioned, an optimization method is used which aims at the highest possible efficiency with regard to the energy balance (effectiveness criterion) and the most accurate achievement of the target speed at the coasting target (target criterion). The maximum permissible braking deceleration and the maximum permissible change in braking deceleration are specified as boundary conditions; In addition, some measures are generally rated as poor, in particular the implementation of a braking intervention with the brake system, which should be avoided as possible. In order to find the most suitable operating strategy in the form of the action plan in the context of the optimization method, in addition to the current operating state, in particular the current speed, ego data concerning the motor vehicle, route data containing a static description of the route up to the coasting destination and the current driving situation will be described Driving situation data, ie a dynamic description of transient events along the way, considered. The dynamic behavior of the motor vehicle, in particular the deceleration behavior, is mapped via a dynamics model of the motor vehicle which is also used The gradient data can be from digital map data of a navigation system of the motor vehicle and optionally from sensor data of environmental data of the motor vehicle, for example sensor data from Environment sensors of the motor vehicle, such as a traffic sign recognition are determined.

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

This input information as well as a possible action plan determined in step S4 are to be illustrated by FIGS. 3 and 4 in more detail.

There, a motor vehicle 7 according to the invention is shown on a route 8, for example a country road. The Ausrollziel 9 is presently marked by a city sign 10 entrance to a city. The distance and the course of the route 8 to there is described by the route data as well as an on-trail slope 11 and an on-slope 14. The driving situation data includes information about a preceding road user 13 and the motor vehicle 7 following road users 14. Furthermore, it is included in the driving situation data that currently a strong wind blows from the rear, characterized by the arrow 15, and possibly special conditions of the road, such as moisture and / or smoothness.

4 illustrates a possible action plan for this route 8 and an associated speed course 16 from the current speed 17 of the motor vehicle 7 to the set speed 18 at the coasting destination 9.

At a point in time 19 (the current time), the action plan begins with a first measure, in which the drive train of the motor vehicle 7 is switched to the freewheeling operating mode. In this, it first rolls along the level track and climbs in the region 20 under speed decrease the slope 11 until the variable slope 12 is reached. in the Freewheel operation mode of the drive train threatens the motor vehicle 7 now again to accelerate, which is why at a time 21, the drive train is switched as a further measure in the overrun mode, initially without a change in the switching stage of the transmission of the motor vehicle 7. At time 22, the slope is stronger, so that a switching stage is switched back in the transmission, which is another measure. After the gradient is a little stronger, at a time 23, the recuperation is increased in order to continue to maintain a certain delay of the motor vehicle 7. The slope 12 is completed at time 24 and the drive train of the motor vehicle 7 is switched in a further measure back to the freewheeling operation mode, in which the motor vehicle 7 further rolls on the coasting target 9. After the speed of the motor vehicle has to be reduced still further, however, the drive train is again switched to overrun operating mode at a time 25, a shift upshifted and the recuperation reduced again in order to obtain a desired brake deceleration such that At a time 26 when reaching the coasting target 9, the target speed 18 is reached. In addition, at time 26, as the last measure of the action plan, the powertrain will be switched back to idle mode.

It can be seen that at all measures times 19, 21, 22, 23, 24, 25 and 26, the operating state of the motor vehicle 7 changes with respect to the longitudinal guide.

The implementation of the action plan begins in step S5, although, step S6, whose further validity is constantly monitored in response to current Fahrsi- tuationsdaten and the current speed of the motor vehicle 7. If an unexpected effect occurs, for example an excessive deceleration of the motor vehicle due to the gradient 11, after it was not exactly contained in the route data, the action plan can be correspondingly changed by dynamic adaptation so that the setpoint speed 18 is obtained as accurately as possible , Another example of any necessary adaptation of the Action Plan is: when the driving situation data describe that the motor vehicle 7 threatens to drive onto the slower road user 13. Then it may be necessary to first adapt the speed of the motor vehicle 7 to that of the road user 13.

If a meaningful Ausrollvorgang impossible, for example, because the speed can not be sufficiently reduced within the boundary conditions, too slow a speed at Ausrollziel 9 threatens or in any case to maintain the overall safety a driving engagement of the driver itself is required, this is the driver by issuing a corresponding information, in particular a Fahrübernahmeaufforderung communicated. This is not shown in greater detail in FIG. 1 for the sake of clarity. In this way, even with changes in the known driving situation through the dynamic monitoring and adaptation of the action plan in step S6, the most effective possible operation or the achievement of the target speed 18 at the coasting target 9 is ensured.

In step S7 it is then checked whether the coasting target 9 has been reached. If not, the execution of the possibly updated action plan is continued in step S5, cf. Arrow 27.

Otherwise, the procedure continues again with step S1 and checks whether a new coasting process has been initiated.

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

During the execution of an action plan, this can be communicated to the driver by means of a corresponding status display, wherein in the present exemplary embodiment different status displays are used depending on whether or not an indication is answered within the predetermined time. In the second case also embodiments are conceivable in which then no status display. The status display can as an extension of a symbol used to output the hint.

Finally, FIG. 5 shows a schematic diagram of the motor vehicle 7 according to the invention. This has the driver assistance system 28 for assisting the driver in a coasting process, which can implement the functions 1 and 2 by means of a control device 29, which is designed to carry out the method according to the invention. In order to obtain the required data, the control unit 29 is connected via a bus system, such as a CAN bus or a Flex-Ray bus, with other vehicle systems, which are shown only partially here. Thus, the motor vehicle also has a navigation system 30 with digital map data, a motor vehicle-to-X communication device 31 and environment sensors 32.

In addition, the operating states of the motor vehicle 7 with respect to the longitudinal guide can be produced via the control unit 29, in particular also via other control devices, not shown in detail. There is therefore a connection via the vehicle bus to the gear 33, the drive motor 34, the disconnect clutch 35 and the brake system 36. The separating clutch 35, the gear 33 and the drive motor 34 form part of the drive train of the motor vehicle. 7

Claims

P A T E N T A N S P R E C H E Method for operating a driver assistance system (28) assisting the driver during a coasting process in a motor vehicle (7) whose drive train is operable in a freewheeling operating mode in which a drive motor (34) is separated from the rest of the drive train by a separating clutch (35), characterized, in that, when the driver assistance system (28) is activated, when the driver terminates an actuation of the accelerator pedal and at least one potential deceleration target (9) requiring deceleration of the motor vehicle (7) is determined or known, at least one measure for the targeted deceleration of the motor vehicle (28) 7) comprehensive action plan taking into account at least one on the energy balance of the motor vehicle (7) related and a determined on the delay to the coasting target (9) target criterion as well as from the way (8) to the coast target (9) describing predictive track data determined and is used for longitudinal guidance of the motor vehicle (7), wherein the measures are selected from a group of measures comprising at least one operation in the freewheeling operation mode and operation in a coasting operating mode. Method according to claim 1, characterized, in that the coasting target (9) comprises a position at which the motor vehicle (7) is to have a lower target speed (18) than the current speed (17) of the motor vehicle (7). Method according to claim 1 or 2, characterized, in that a further adaptation of a recuperation stage and / or changing of a switching stage of a transmission (33) of the motor vehicle Vehicle (7) and / or a brake system (36) of the motor vehicle (7) using braking intervention comprehensive set of measures is used. 4. The method according to any one of the preceding claims,  characterized,  the at least one measure associated with an action execution time point (19, 21, 22, 23, 24, 25, 26) in the action plan relates to a change of the operating state of the motor vehicle (7) with respect to the longitudinal guidance. 5. The method according to any one of the preceding claims,  characterized,  that an identification and execution of an action plan after or without an output of an indication for the termination of an operation of the accelerator pedal to a driver. 6. The method according to claim 5,  characterized, that a maximum allowable deceleration and / or a maximum allowed deceleration delay is taken into account in the determination of the action plan, wherein a lower maximum allowed deceleration and / or determination of an action plan without prior issuance of an accelerator depression instruction to a driver or a change in braking deceleration and / or a restricted set of measures, in particular a set of measures limited with respect to the deceleration possibilities, is used within a predetermined time after the indication has been given, and / or the maximum permitted deceleration and / or the maximum permitted deceleration change is reached before reaching of the coasting target depending on since the issue of an indication to end an operation of the accelerator pedal to a driver past waiting time of the driver with increasing waiting time are lowered and / or the measures gr up pe is limited depending on the waiting time mi rising waiting time. 7. The method according to claim 5 or 6,  characterized,  in determining the action plan, the or a maximum allowable deceleration and / or a maximum allowable deceleration change delay are considered, wherein in a predetermined time after issuing an indication to stop an operation of the accelerator pedal to a driver triggered determination of an action plan then if, within the maximum permitted braking deceleration and / or the maximum permitted change in the braking deceleration, a target speed (18) at the coasting target (9), in particular the position, can not be achieved, an output of relevant information, in particular a driving pickup request, is made to a driver , 8. The method according to any one of claims 5 to 7,  characterized,  that upon termination of the operation of the accelerator pedal within or a predetermined time after an indication to end an operation of the accelerator pedal to a driver, the determination of the action plan is carried out with greater weighting of the target criterion and otherwise under greater weighting of the effectiveness criterion. 9. The method according to any one of claims 5 to 8,  characterized,  in that at least one operating device which permits independent activation of the instruction for the termination of an operation of the accelerator pedal to a driver and the function (1) for the determination and execution of the action plan is used. 10. The method according to claim 9, characterized, in that the function (1) for determining and executing the action plan is automatically activated when the driver (2) activates the instruction for ending an actuation of the accelerator pedal to a driver. 11. The method according to any one of claims 5 to 10,  characterized,  that in an execution of an action plan without prior issuance of an instruction to end an operation of the accelerator to a driver no and / or another status display of the driver assistance system (28) is issued as in a determination and execution of an action plan within or a predetermined time after issue an indication to end an operation of the accelerator pedal to a driver. 12. The method according to any one of the preceding claims,  characterized,  that an action plan is determined in which is switched to a coasting mode in a freewheeling operation mode, in particular with reaching the coasting target (9). 13. The method according to any one of the preceding claims,  characterized,  that the action plan is determined taking into account driving situation data describing the current driving situation. 14. The method according to claim 13,  characterized, that further road users (13, 14), in particular motor vehicle (7) immediately following and / or leading road users (13, 14), and / or the current weather conditions and / or the current road condition descriptive driving situation data are used and / or the driving situation data from current sensor data from environment sensors (32) of the motor vehicle (7) and / or from communication data received via a vehicle-to-X communication is determined. 15. The method according to claim 13 or 14,  characterized,  the action plan is cyclically re-determined and / or adapted dynamically on the basis of the driving situation data, the action plan currently being determined being carried out in the event of a deviation of a currently determined action plan from the previous action plan and / or a current action plan that can not be determined on the basis of the current driving situation data information relating thereto, in particular a driving-over request, is issued to the driver. 16. The method according to any one of claims 13 to 15,  characterized,  that when an indication to end an operation of the accelerator pedal is to be output to a driver, the output of the indication is suppressed or delayed, when the driving situation data evaluating, a close behind the own motor vehicle (7) located further road users (14) concerning Hintermannkriterium is satisfied. 17. The method according to claim 16,  characterized,  in that a relative speed of the own motor vehicle (7) to the immediately following road user (14) exceeding a threshold value and / or a distance below the threshold to the immediately following road user (14) are present for meeting the background criterion. 18. The method according to claim 15, characterized, the threshold values are adjusted as a function of the driving situation data and / or the route data. 19. motor vehicle (7) comprising a drivetrain operable in a freewheeling operation mode and a driver assistance system (28) assisting the driver in a coasting operation with a control device (29) designed to carry out a method according to one of the preceding claims.