CN115805928A - Method for informing a motor vehicle driver of a fault associated with a motor vehicle brake system - Google Patents

Abstract

The invention relates to a method for informing a driver of a motor vehicle of a fault associated with the braking system of a motor vehicle, wherein the method has the steps of: acknowledging the fault and, if the brake pedal is actuated, detecting the brake pedal Actuation information, brake pedal actuation information describes the actuation travel of the brake pedal which is covered by actuation; the braking torque information is determined by applying the fault case braking torque determination criteria to the detected brake pedal actuation information, brake The torque information describes the braking torque for at least one wheel brake, wherein the determined braking torque is less than one third of the typical braking torque if the covered actuation travel is less than one third of the maximum actuation travel , but if the maximum actuation travel has been passed, the determined braking torque information describes the maximum braking torque; and the at least one wheel brake is acted upon with the braking torque described by the determined braking torque information.

Description

Method of notifying a motor vehicle driver of a malfunction associated with a motor vehicle braking system

technical field

The invention relates to a method for notifying a driver of a motor vehicle of a fault associated with a brake system of the motor vehicle. The invention also relates to a motor vehicle which is designed to carry out such a method.

Background technique

Currently, motor vehicles typically have a braking system with at least one wheel brake associated with a wheel of the motor vehicle. The at least one wheel brake is usually actuated taking into account manual actuation of the brake pedal by the driver of the motor vehicle. In this case, the actuation can take place purely electronically, wherein the actuating device and the actuating device of the brake system are preferably mechanically decoupled from one another. In this case, the actuating device is a brake pedal and the actuating device is, for example, a wheel brake associated with at least one wheel of the motor vehicle. This type of braking system is known as brake-by-wire.

A vehicle is known from US 2018/0194353 A1, in which a mode is provided for fault situations in which a stronger brake pedal actuation is required in order to achieve the desired braking of the motor vehicle.

Contents of the invention

The object of the present invention is to provide a solution by means of which the driver of the motor vehicle is notified that a fault has occurred in the motor vehicle which can be associated with the braking system of the motor vehicle.

The object is solved by a method for notifying a driver of a motor vehicle of a fault associated with a braking system of the motor vehicle and a motor vehicle having a braking system.

The invention is based on the realization that if there is a malfunction in the motor vehicle which is related to the functioning of the brake system, it is useful to indicate this malfunction to the driver of the motor vehicle. This is the case in particular if the fault has the potential to lead to a functional deterioration of the brake system due to a subsequent fault, since this increases the probability of occurrence of a subsequent fault, for example. This is always the case, for example, when the brake system itself is still functional due to a fault that has occurred (because the backup layer of the brake system is still functional, for example), but it may only be the case when a subsequent fault occurs. Braking can also be performed with a reduced functional effect of the braking system, so that, for example, in the event of a subsequent failure, only two of the four wheels can be used with the corresponding arrangement of the braking system there. Wheel brakes apply the brakes.

Therefore, the driver is informed that there is a probability that the brake system will fail or at least partially fail in the near future. For example, a visual indication output in the motor vehicle, for example by means of a warning light and/or a warning display on a display device of the motor vehicle, is suitable for this notification to the driver of the motor vehicle. As an alternative or in addition to this, the notification can take place by means of an acoustic indication, for example by means of a warning sound which is output in the motor vehicle. However, such visual and/or acoustic indications are often not understood and/or ignored by the driver. It is therefore expedient to inform the driver of a fault in another way, for example in addition to visual and/or acoustic indications. Haptic feedback to the driver is suitable for this, which can be achieved, for example, by changing the pedal feel. The driver can then be informed, for example, that in the event of a fault the brake pedal actuation by the driver and the activation of the at least one wheel brake of the motor vehicle are changed compared to normal operation without faults. Correlation between braking torques. Haptic feedback can be achieved, for example, by initially setting a kind of idle travel. This means that, in the event of a fault, a lower brake deceleration is set in the event of a specific brake pedal actuation than in the normal, fault-free situation. Furthermore, an advantage of this warning display is that in motor vehicles no brake pedal with an active actuator is required in order to output a tactile feedback perceivable to the driver by means of the brake pedal, since the resulting The tactile feedback is only possible due to a change in the brake pedal force characteristic, ie a change in the correlation between brake pedal actuation and braking torque.

The method according to the invention serves to inform the driver of the motor vehicle of a fault associated with the braking system of the motor vehicle. A fault associated with the braking system of a motor vehicle is a fault involving the braking system, ie a fault related to the braking system. Such faults are, for example, electrical faults, such as electrical faults in the onboard electrical system of the motor vehicle, leakage of hydraulic wheel brakes of the braking system and/or overheating of at least one wheel brake of the motor vehicle at high ambient temperatures of the motor vehicle .

The brake system has a brake pedal, at least one wheel brake associated with a wheel of the motor vehicle, and a brake pedal sensor device. The at least one wheel brake can be electronically actuated taking into account manual actuation of the brake pedal. For this purpose, the position of the brake pedal is detected, for example, by means of a brake pedal sensor device when the brake pedal is manually actuated by the driver, and is provided and evaluated as corresponding brake pedal sensor data for actuating the wheel brakes. The braking system is thus a so-called brake-by-wire. The brake pedal is thus mechanically decoupled from the at least one wheel brake. The motor vehicle preferably has at least one wheel brake for each motor vehicle wheel, ie, for example, four preferably hydraulic wheel brakes in the case of four wheels of the motor vehicle. Furthermore, in addition to the four hydraulic wheel brakes, the brake system preferably has an electronic parking brake for each rear wheel of the motor vehicle, for example on each wheel of the rear wheel axle. The at least one wheel brake may alternatively be referred to as a brake actuator. Each of the wheel brakes is designed to brake the wheel of the motor vehicle associated with it when the braking torque is applied, depending on the applied braking torque. The braking system preferably has a control device by means of which the at least one wheel brake can be electronically actuated taking into account manual actuation of the brake pedal. The control unit can also be designed to evaluate the brake pedal sensor data detected by the brake pedal sensor device. The control device preferably has a processor device.

The method has the step of identifying a fault associated with a braking system of a motor vehicle. However, despite the detected fault, the brake pedal sensor system is still functional, the at least one wheel brake is still actuatable and the brake pedal is still actuatable. Therefore, the braking system can still continue to function. In this case, the active braking system may be the primary braking system of the motor vehicle, but may also be a secondary braking system and, for example, be provided as a backup level braking system in the event of a fault. A detected fault is, for example, a leak in one of the hydraulic wheel brakes, so that, for example, the wheel brake associated with at least one of the wheels of the motor vehicle is faulty and is no longer functional. If a subsequent fault now occurs, the braking system may no longer be able to brake. Thus, in this example, there is a fault associated with the braking system of the motor vehicle, in which case the driver is to be notified of the fault. Because the fault itself and, in particular, possible subsequent faults have an influence on the functioning of the braking system. The driver is therefore notified of the fault, ie a leak of one of the hydraulic wheel brakes.

If the brake pedal is actuated, ie if the driver manually actuates the brake pedal, the brake pedal actuation information is preferably detected by means of the brake pedal sensor system. The brake pedal actuation information describes the actuation path covered by the actuation of the brake pedal. The actuation travel of the brake pedal can alternatively be referred to as brake pedal actuation travel. For example, the brake pedal actuation information can be determined by evaluating the brake pedal sensor data of the brake pedal sensor device. This evaluation step can be carried out, for example, by means of a control device of the brake system, which has an evaluation algorithm for this purpose.

Furthermore, braking torque information is preferably determined, which describes the braking torque for the at least one wheel brake. The braking torque information is determined by applying a fault-case braking torque determination criterion to the detected brake pedal actuation information. The fault case braking torque determination criterion is an algorithm and/or a rule that describes the correlation between the actuation travel traveled by the brake pedal and the braking torque to be set based on this actuation travel. Determination of braking torque information, applying a fault-case braking torque determination criterion, comprising: if the actuation travel traveled is less than at least three minutes of the maximum actuation travel that can be traveled maximally when the brake pedal is actuated one, the measured braking torque is less than one-third of the typical braking torque that would be different from the criteria for determining the braking torque in the fault case and that would be obtained when the fault was not confirmed The applied normal-case braking torque determination criteria are determined in the case of the detected maneuvering information. Therefore, at least for the first third of the possible actuation travel of the brake pedal, a different relationship between actuation travel and braking torque is assumed than is assumed for the correlation provided for the normal, fault-free situation. Correlation. The dependencies provided for the normal situation without faults are stored in the normal situation braking torque determination criterion, ie are preset by the normal situation braking torque determination criterion. Fault situation The braking torque determination criterion is only applied when no normal situation exists, for example because a fault has occurred. Compared with the normal-case braking torque determination criterion, the fault-case braking torque determination criterion sets a reduction of the braking torque for small actuation travels, more precisely to a maximum third of the typical braking torque for the normal situation one. Furthermore, the reduction is limited in such a way that the reduction occurs only when the actuation value includes at most one third of the maximum actuation travel of the brake pedal. Alternatively, the maximum actuation travel can be referred to as the maximum actuation travel of the brake pedal. The maximum actuation value is predetermined by the brake pedal fixedly, ie in an unchangeable manner due to its design. As a result, at the beginning of the actuation of the brake pedal, ie in the first third of the maximum actuation travel, less strong braking occurs than in the normal situation without faults.

However, in the case of a maximum actuation of the braking torque, the maximum possible braking power, ie the maximum braking torque, is achieved. The reduction of the braking torque is thus stopped at least when the maximum actuation travel is reached, since it is provided that the at least one wheel brake is acted upon with the maximum braking torque. Therefore, at least in the case of a maximum actuation travel, the fault-case braking torque determination criterion corresponds to the normal-case braking torque determination criterion.

In a final method step, the at least one wheel brake is preferably acted upon with a braking torque described by the determined braking torque information. The determined braking torque, that is to say the ascertained braking torque information, is thus actually used to actuate the wheel brakes when the fault-case braking torque determination criterion is applied. In other words, the at least one wheel brake is acted on the basis of the determined braking torque information. As a result, the motor vehicle is preferably braked.

Due to the delayed braking response at an actuation travel of less than one-third of the maximum actuation travel, the driver notices a deviation from normal in the braking response of the motor vehicle as a reaction to the actuation of the brake pedal , due to adjustment to a weaker braking torque compared to normal conditions without faults. However, if the driver does want emergency braking, for example, this continues in a customary manner, since at maximum actuation travel the maximum braking torque is determined as braking torque information, and by correspondingly applying the at least A wheel brake is implemented.

The determination of the braking torque information and the application of the at least one wheel brake on the basis of the determined braking torque information are preferably carried out by means of a control device of the brake system.

On the basis of the determined braking torque information, the driver of the motor vehicle can be reliably notified of faults associated with the braking system of the motor vehicle, since the final tactile indication is via the actuation travel of the brake pedal and the applied braking torque The changed correlation between them is realized and sensed by the driver through the sense of touch. However, it is ensured that in the event of an expected emergency braking, for example, no possibly undesired reduction of the maximum braking torque occurs in this case.

In the case of an actuation of the brake pedal that is greater than one third of the maximum actuation travel and less than the maximum actuation travel, a continuation of the braking torque information for the increased brake pedal actuation information and/or with the first third A steeper rise than one-third. However, the correlation between the braking torque information and the brake pedal actuation information preferably still remains different from the corresponding correlation according to the normal braking torque determination criterion.

In addition to the measures provided according to the invention for informing the driver by means of tactile indications, provision can also be made to output visual and/or audible indications for the corresponding malfunction in the motor vehicle. For this purpose, for example, a warning symbol can be displayed on a display device, a warning light can be activated, a voice can be output by means of a loudspeaker device in the motor vehicle and/or a warning tone can be output by means of a loudspeaker device.

According to one embodiment, it is provided that the determined braking torque information is zero if the actuation travel covered is less than one-third of the maximum actuation travel. Therefore, instead of prescribing a braking torque that is only reduced to at least one third of the typical braking torque, an idle travel can thus be permanently provided in the first third of the maximum actuation travel. In other words, in this case the motor vehicle does not react with the brakes to the actuation of the brake pedal by the driver until at least one third of the maximum actuation travel has been covered by the actuation of the brake pedal. If, for example, only a quarter of the maximum actuation travel is traversed when the brake pedal is actuated, the at least one wheel brake is not acted upon with a braking torque, that is to say the motor vehicle is not braked at all in this case . This is a particularly clear signal to the driver that something is wrong with the brake system, so that the driver can be informed particularly reliably of a fault associated with the brake system.

A further embodiment provides that an actuation speed value is determined, which describes the speed at which the brake pedal is actuated. That is, it is determined how quickly the driver actuates the brake pedal, ie within what time a certain actuation travel of the brake pedal is traversed. If the steering speed value is greater than the steering speed limit value, the normal case braking torque determination criteria apply. In the case of preferably particularly rapid actuation of the brake pedal, a greater braking force can be set for each actuation path traversed than is actually provided by the failure braking torque determination criterion for the total actuation path traversed.

This exemplary embodiment is based on the recognition that an actuation speed greater than an actuation speed limit value indicates an emergency braking situation. In such emergency braking situations, an unnecessarily long braking travel should not be provided. For this reason, in this case, instead of the fault-case braking torque determination criterion, the normal-case braking torque determination criterion provided for the fault-free normal situation is used.

Alternatively, one embodiment provides that an actuation speed value is determined, which describes the speed at which the brake pedal is actuated. That is, it is determined how quickly the driver actuates the brake pedal, ie within what time a certain actuation travel of the brake pedal is traversed. If it is confirmed here that the actuation speed value is greater than the actuation speed limit value, the intermediate case braking torque determination criterion is applied. This standard is different from the standard for determining the braking torque in fault conditions and the standard for determining the braking torque in normal conditions. Depending on the speed at which the brake pedal is actuated, there is therefore a changeover, if possible deviating from a change in the fault-case braking torque determination criterion, in particular into an intermediate-case braking torque determination criterion.

The intermediate-case braking torque determination criterion associates with each brake pedal actuation information an intermediate-case braking torque information which is greater than the braking torque information determined using the failure-case braking torque determination criterion . That is to say, a braking torque information is determined which is greater than the braking torque information determined according to the criterion for determining the braking torque in the fault case. However, this braking torque information is preferably smaller than the braking torque information according to the normal situation braking torque determination criteria. For this reason, this braking torque information is referred to as intermediate case braking torque information. Therefore, a braking torque information is provided which is between the braking torque information in the normal case and the braking torque information in the fault case. Due to the high speed of actuation of the brake pedal, an intermediate phase of the applied braking torque between the normal situation and the fault situation can be activated. This makes it possible to send a tactile indication to the driver despite the high actuation speed when the brake pedal is actuated, i.e. to inform the driver of a fault, since there are still deviations from the norm for determining the braking torque in normal situations, i.e. not using Instead of the braking torque for actuating the wheel brakes that would be used in the normal, fault-free situation, a different braking torque information, namely the intermediate case braking torque information, is used.

A particularly advantageous embodiment provides that the motor vehicle has a power supply and a drive system. The drive system has an accelerator pedal and a drive unit for longitudinally controlling the motor vehicle. The drive unit can be electronically actuated taking into account the manual actuation of the accelerator pedal. The drive unit is, for example, a motor, such as an electric motor and/or an internal combustion engine of a motor vehicle. The drive system can also have a control device, which can be referred to as a drive control device, for example, and by means of which the drive device can be controlled electronically, taking into account manual actuation of the accelerator pedal. The motor vehicle therefore has a drive system based on drive-by-wire. In other words, the accelerator pedal and the drive unit for the longitudinal control of the motor vehicle are mechanically decoupled.

A fault associated with the energy supply is now detected, wherein despite the detected fault associated with the energy supply, the at least one wheel brake and the drive system can be controlled taking into account a corresponding manual actuation. For example, an imminent failure of the power supply can be detected early, for example, with a lead time of, for example, one minute by means of a sensor device in the high-voltage battery of the motor vehicle which detects, for example, a sudden voltage drop. For example, the residual energy of the energy supply can then be inferred and thus, for example, the point in time of an expected complete or at least partial failure of the brake system due to lack of energy supply can be predicted. Failure of the braking system is a consequence of failure of the energy supply. For example, such failures are referred to as energy supply-associated failures.

If a fault associated with the energy supply is confirmed, the motor vehicle can be accelerated with the aid of the drive device when the brake pedal and subsequently the accelerator pedal of the motor vehicle are actuated, taking into account the manual actuation of the accelerator pedal in the foreseeable future. Acceleration of the motor vehicle is only allowed after a set waiting period. Sets a dead time that is active in the event of a subsequent accelerator pedal actuation after the brake pedal is released. The dead time is preferably a few seconds, eg 2 seconds, 3 seconds, 4 seconds, 5 seconds or 10 seconds. By virtue of this waiting period when an acceleration of the motor vehicle is desired after the detection of a fault associated with the energy supply, the driver of the motor vehicle is tactilely informed of the presence of a fault.

The energy supply-related faults present here are also faults related to the braking system of the motor vehicle, since the energy supply for the braking system is affected. However, the fault is considered as a special case, and the driver is therefore notified of this fault in a different manner and thus differentiated. Finally, based on the reaction of the drive system of the motor vehicle to the actuation of the accelerator pedal, the driver of the motor vehicle can be notified of a malfunction associated with the energy supply of the motor vehicle. Here, the type of notification differs from that in the above-mentioned general fault situation involving the brake system. Ultimately, the relationship between the acceleration, ie the propulsion power of the motor vehicle, and the actuation of the accelerator pedal due to a confirmed fault associated with the energy supply is changed, so that not only due to the changed reaction of the brake pedal, but also Due to the changed reaction of the motor vehicle after actuation of the accelerator pedal, the driver is made aware of motor vehicle conditions which may arise as a result of a malfunction. The driver is thus notified particularly reliably of failures associated with the energy supply, since the delayed response of the accelerator pedal is tactilely perceivable.

According to a further exemplary embodiment, provision is made to actuate the drive unit and/or the at least one wheel brake after the detection of a fault associated with the energy supply in such a way that the current propulsion power of the motor vehicle is reduced. The current propulsion power is preferably reduced by a propulsion power value. The propulsion power value can be preset as a constant value. As an alternative to this, a time-dependent reduction can be provided, ie for example the propulsion power value becomes more and more increasing over time. For example, the acceleration of the motor vehicle can be reduced by, for example, automatically reducing the acceleration of the motor vehicle preset by the drive unit. Alternatively or additionally to this, the at least one wheel brake can be acted upon with a predetermined braking torque in order to actively brake the motor vehicle. As a result, the energy supply of the braking system, which may no longer be available in the near future, is reacted early in that a reduction in the speed of the motor vehicle can eventually be brought about in a simple manner due to the reduction in propulsion power. This has the result that the transition of the motor vehicle to a standstill is already facilitated before the energy supply actually wears out.

Furthermore, one embodiment provides that the at least one wheel brake is an electric parking brake, which is brought into a permanently active state after the detection of a fault based on the energy supply. The electronic parking brake is arranged, for example, at the respective rear wheel of the motor vehicle, i.e. the electronic parking brake is associated with the respective rear wheel of the motor vehicle and is designed to brake the respective rear wheel and/or hold it in a braking state middle. In the permanently active state, a permanent braking intervention is carried out by the electronic parking brake, which is maintained even in the event of a loss of the energy supply of the braking system, due to the absence of energy-supplied electronics The parking brake cannot be brought from permanently active to deactivated.

When the accelerator pedal of the motor vehicle is actuated, the motor vehicle can continue to be driven despite the permanent activation of the electronic parking brake. The motor vehicle can thus continue to accelerate, for example by actuating the accelerator pedal, but this acceleration, ie the propulsion power of the motor vehicle, is reduced in connection with actuation of the accelerator pedal compared to the normal situation in which the parking brake is not permanently activated. The degree of reduction results from the braking power of the permanently active parking brake. If the energy supply to the braking system is now indeed completely lost, for example as a consequence of a detected fault, the drive unit is also no longer supplied with energy due to the lack of energy supply to the motor vehicle, so that the motor vehicle cannot accelerate any further. However, the electronic parking brake remains permanently activated in this state, so that the motor vehicle can now be braked to a standstill, for example by means of the already activated parking brake, despite a lack of energy supply to the braking system. Measures are therefore taken in order to be able to reliably bring the motor vehicle to a standstill in the event of a real failure of the energy supply of the motor vehicle. The driver is thus not only notified of a failure involving the energy supply, but also already takes measures in the event of a real failure of the energy supply.

As an alternative or in addition to activating the electric parking brake, in the case of hydraulic wheel brakes, a locking of the brake pressure at the at least one wheel brake can be activated when the valve is closed without current. This also makes it possible to brake the motor vehicle by means of at least one wheel brake switched in this way in the event of a real wear and tear of the energy supply of the motor vehicle. Preferably, a permanent braking torque is always applied to at least two wheel brakes arranged on two different sides of the motor vehicle in the transverse direction of the motor vehicle.

According to a particularly preferred embodiment, it is provided that the motor vehicle has a drive system with: an accelerator pedal; a drive device for longitudinally controlling the motor vehicle, which is able to In the case of manual manipulation of the accelerator pedal, it is electronically controlled. Furthermore, the drive system has an accelerator pedal sensor device which is able to detect an actuation of the accelerator pedal. It is now the case that the brake pedal sensor arrangement cannot function due to a detected fault associated with the braking system of the motor vehicle. The at least one wheel brake is now acted upon with a predetermined basic braking torque. As a result of the detected defective brake pedal sensor arrangement, the motor vehicle is braked, more precisely in accordance with a defined basic braking torque. The travel speed of the motor vehicle is thus reduced by targeted braking interventions in which the at least one wheel brake is acted upon with a predetermined basic braking torque.

If the accelerator pedal is actuated in this case, that is to say preferably if the driver actuates the accelerator pedal with a predetermined basic braking torque despite acknowledging the fault, the accelerator pedal actuation information is detected. Accelerator pedal actuation information is detected by means of the accelerator pedal sensor system. The accelerator pedal actuation information describes the actuation travel of the accelerator pedal over which the accelerator pedal is actuated. Corresponding information relating to accelerator pedal actuation is therefore detected analogously to brake pedal actuation information. Then, if the detected accelerator pedal actuation information is less than the accelerator pedal actuation limit value, the at least one wheel brake is acted upon with a special-case braking torque that is less than the base braking torque. The special case braking torque may alternatively be referred to as a fault case braking torque when the brake pedal sensor arrangement is inoperative. If the accelerator pedal is only lightly actuated by the driver because the accelerator pedal actuation information is less than the accelerator pedal actuation limit value, this will lead to a retraction of the braking deceleration that has already occurred, because a braking torque that is not too high, ie The lower braking torque of the preset basic braking torque is selected. The achieved braking deceleration is thus reduced and withdrawn. Accordingly, the driver's desire to accelerate is thus translated into reduced braking of the motor vehicle compared to the braking currently taking place.

If the detected accelerator pedal actuation information is greater than or equal to the accelerator pedal actuation limit value, the acceleration information is determined by applying the fault case acceleration determination criterion to the detected accelerator pedal actuation information. The acceleration information describes the acceleration of the motor vehicle. The drive unit is actuated in such a way that the motor vehicle is accelerated according to the acceleration information. If the accelerator pedal is actuated more strongly than the accelerator pedal actuation limit value, it is provided that acceleration of the motor vehicle is possible because acceleration information is then determined. However, for this the driver has to depress the accelerator pedal significantly harder and therefore further than the driver would normally have to do if there was no malfunction of the brake pedal sensor system. In other words, the fault-case acceleration determination criterion is applied instead of the normal-case acceleration determination criterion applied in normal conditions without faults.

The error acceleration determination criterion includes an algorithm and/or a rule which relates the actuation travel traveled by the accelerator pedal to a desired acceleration, ie acceleration information. In other words, the fault case acceleration determination criterion includes an accelerator pedal actuation characteristic line for the drive system of the motor vehicle. The fault case acceleration determination criterion therefore includes a correlation between the accelerator pedal actuation travel and the acceleration of the motor vehicle.

When the accelerator pedal is actuated, it is thus possible to inform the driver of the presence of a fault due to different types of influences of the acceleration of the motor vehicle depending on the accelerator pedal actuation than in the normal situation without faults. Therefore, a special fault-specific tactile indication is provided for the driver, which indicates a fault in the motor vehicle associated with the braking system.

One embodiment provides that, taking into account the detected accelerator actuation information, the motor vehicle is not accelerated if the detected accelerator actuation information is less than the accelerator actuation limit value. In other words, the motor vehicle is only braked and not accelerated at all whenever the accelerator actuation information indicates an accelerator actuation below the accelerator actuation limit value. Thus, despite actuation of the accelerator pedal, the propulsion power of the motor vehicle is not increased in this case compared to the current propulsion power resulting from the applied base braking torque. Thus, for example, if the driver only slightly actuates the accelerator pedal, the driver then confirms that the motor vehicle is not accelerating, but that the motor vehicle is still only being braked. The driver can, for example, react to this haptic feedback by, for example, thereby stopping the driver from actuating the accelerator pedal and allowing the motor vehicle to be braked to a standstill with a predetermined basic braking torque, the at least one wheel brake This preset base braking torque has already been applied. During the braking of the motor vehicle in accordance with the applied basic braking torque, the driver can, for example, continue to steer the motor vehicle, for example by means of the steering system of the motor vehicle, and, for example, control the parking position at the road edge of the road, the motor vehicle currently driving on this road.

According to one embodiment it is provided that the measured acceleration information is smaller than the typical acceleration information which is applied when the normal situation acceleration determination criterion which is different from the fault condition acceleration determination criterion and which is applied when the fault is not confirmed is applied. Determined in the case of detected accelerator pedal actuation information. Although the accelerator pedal actuation range has been reached, which is higher than the accelerator actuation limit value and in which the vehicle continues to accelerate, it is still provided that the motor vehicle travels at a lower speed than in the normal, fault-free situation. strength acceleration. This results in the fact that the motor vehicle cannot be accelerated as if the brake pedal sensor device were active because the brake pedal sensor device is disabled. From this, it should be made clear to the driver that something is wrong with the motor vehicle, since the driver cannot achieve the acceleration to which he is accustomed. This might irritate the driver and is therefore experienced as a haptic warning. This measure thus achieves that the driver is notified of a fault associated with the brake system of the motor vehicle which involves the brake pedal sensor system.

Furthermore, it can be provided that a pre-accelerator actuation limit value is set which is smaller than the accelerator actuation limit value. When the accelerator pedal actuation information is between the pre-accelerator actuation limit value and the accelerator pedal actuation limit value, it is provided that the at least one wheel brake is neither acted upon with a predetermined braking torque nor the drive unit is actuated such that The motor vehicle accelerates with acceleration information greater than zero. Instead, the motor vehicle can, for example, merely continue to roll, so that the motor vehicle brakes, for example due to friction, preferably without the action of a braking system. A free travel for the accelerator pedal is thus provided. The free travel is an additional tactile indication for the driver, since the driver cannot accelerate the motor vehicle despite actuating the accelerator pedal.

Furthermore, an embodiment provides that after the accelerator pedal has been actuated, the at least one wheel brake is acted upon with a predetermined additional braking torque which is greater than the basic braking torque. If it is thus detected that the brake pedal sensor system is not functioning, the at least one wheel brake is initially acted upon with a basic braking torque. If the accelerator pedal is subsequently actuated, the at least one wheel brake will be acted upon with an additional braking torque after said actuation of the accelerator pedal instead of reapplying the at least one wheel brake with a basic braking torque. Since the additional braking torque is greater than the basic braking torque, a stronger braking deceleration of the motor vehicle is now achieved than was previously achieved by applying the basic braking torque.

This exemplary embodiment is based on the knowledge that it should be clearly made clear to the driver that further acceleration of the motor vehicle is practically meaningless in the current situation. Since the driver has already confirmed that he can accelerate the motor vehicle further, for example by actuating the accelerator pedal of the motor vehicle correspondingly strongly, the driver now clearly understands that this is practically meaningless in that the presetting corresponds to the basic braking torque. Ratio of increased additional braking torque. As soon as the accelerator pedal is no longer actuated, the braking of the motor vehicle is automatically reinforced. In this way, the motor vehicle can be decelerated more strongly after, for example, a previous re-acceleration using the determined acceleration information. Through the increased additional braking torque compared to the basic braking torque (with which the at least one wheel brake is acted upon), it should be clear to the driver that the braking system is no longer fully functional and that the driver Motor vehicles should be brought to a standstill if possible.

Furthermore, an embodiment is configured such that, if the accelerator pedal is manipulated again and the accelerator pedal manipulation information detected at the time of the renewed manipulation is greater than or equal to the accelerator pedal manipulation limit value, when applying the repeated situation acceleration determination criterion to the detected Acceleration information is measured repeatedly in the case of accelerator pedal manipulation information. The repeated case acceleration information describes the acceleration of the motor vehicle which is lower than the acceleration determined when the fault case acceleration determination criterion is applied. The drive unit is actuated in such a way that the motor vehicle is accelerated according to the repetitive situation acceleration information. The possible propulsion power in the event of a further acceleration request by the driver is therefore reduced compared to the previous propulsion power which was still possible at the first acceleration request. This reduction always occurs when the driver has actuated the actuation pedal once and actuated the accelerator pedal a second time after recognizing the non-functional brake pedal sensor system. The repeated case acceleration determination criterion is a rule or an algorithm that is applied at the second actuation of the accelerator pedal.

It is achieved that with each further actuation of the accelerator pedal, only a decreasing acceleration of the motor vehicle is permitted. The driver is thus to be informed that further acceleration of the motor vehicle is practically pointless due to a fault in the motor vehicle. However, it is still possible for the driver to be able to steer the motor vehicle, for example, towards a parking lot or the edge of the road without having to be forced to stop beforehand.

It can also be provided that, in one embodiment, a retraction speed value is determined, which describes the speed at which the actuation of the accelerator pedal is retracted. Thus, for example, it is determined at what time and by how much the accelerator actuation travel the driver has taken off his foot from the accelerator pedal. This can be detected by means of the accelerator pedal sensor system. If the retraction speed value is greater than the retraction speed limit value, the at least one wheel brake is acted upon with a retraction braking torque that is greater than the base braking torque. This makes it possible, when the accelerator pedal is released quickly, to set a greater deceleration of the motor vehicle than would be provided by the base braking torque without actuation of the accelerator pedal. In other words, if the driver releases his foot from the accelerator pedal for a short time, ie quickly, the driver can express a desire to brake without having to actuate the brake pedal. In the event of a brake pedal sensor device being inoperative, the retraction speed of the actuation of the accelerator pedal can bring about a faster braking of the motor vehicle, so that despite the brake pedal sensor device being inoperative, the driver still You can continue to operate the braking system.

It can also be provided that, if the electric parking brake of the motor vehicle is already activated, at least one wheel brake that is not an electric parking brake is additionally acted upon with a parking brake-related braking torque that is greater than the basic braking torque. This additional braking torque can, for example, brake the motor vehicle to a standstill. By actuating the electric parking brake, the motor vehicle can be brought to a standstill even though the brake pedal sensor system is disabled and the brake pedal is therefore not actuated.

A preferred embodiment provides that the motor vehicle has an ambient sensor system. At least one surrounding of the area in front of the motor vehicle is detected by means of the surroundings sensor device, which is designed, for example, as a front camera of the motor vehicle. The surroundings sensor device thus detects at least sensor data describing at least one surroundings of the area in front of the motor vehicle. The sensor data are, for example, camera data, ie static and/or moving image data.

Obstacles in the surroundings of the area ahead are determined by applying an obstacle detection criterion to the detected sensor data. Obstacles can be, for example, buildings, road infrastructure elements such as traffic signs and/or traffic lights, other road users and/or pedestrians. The obstacle detection criteria include rules and/or algorithms by means of which obstacles in the sensor data can be detected and identified. For this purpose, the obstacle detection standard can use image processing methods, for example.

If an obstacle has been detected, the at least one wheel brake is acted upon with an obstacle-case braking torque that is greater than the basic braking torque. Therefore, if an obstacle is detected in the area ahead, a higher deceleration of the motor vehicle is set than would be set substantially if no obstacle was detected. In this way, for example, emergency braking up to a standstill can be achieved, ie an immediate emergency stop of the motor vehicle can be carried out due to the detection of an obstacle. In this case, the obstacle situation braking torque is, for example, the maximum braking torque of the motor vehicle. As a result, a braking torque can be preset according to the situation, so that a failure of the brake pedal sensor system can be reacted according to the situation.

A second aspect of the invention relates to a method for informing a driver of a motor vehicle of a fault associated with an energy supply of the motor vehicle. A motor vehicle has: an energy supply; a braking system with a brake pedal and at least one wheel brake associated with one wheel of the motor vehicle, which wheel brake can and a drive system with a brake pedal and a drive device for longitudinal control of the motor vehicle which can be controlled taking into account manual actuation of the accelerator pedal. The method has the step of acknowledging a fault associated with the energy supply, wherein despite the fault being detected, the at least one wheel brake and the drive unit are still able to actuation; and if the brake pedal and subsequently the accelerator pedal of the motor vehicle are actuated, taking into account the manual actuation of the accelerator pedal, the actuation by means of the actuation is only permitted after a preset waiting period The device accelerates the motor vehicle.

With regard to the second aspect, in an advantageous embodiment it can be provided that, after a fault associated with the energy supply has been identified, the drive device and/or the at least one wheel brake are actuated in such a way that the mechanical The current propulsion power of the train.

Furthermore, with regard to the second aspect, it can be provided that the at least one wheel brake is an electronic parking brake which is brought into a permanently active state after a fault associated with the energy supply has been detected, wherein , the motor vehicle can continue to be driven by actuating the accelerator pedal despite the permanent activation of the electronic parking brake.

A third aspect of the invention relates to a method for informing a driver of a motor vehicle about a non-functional brake pedal sensor arrangement of the brake system of the motor vehicle. The motor vehicle has a braking system having: a brake pedal; at least one wheel brake associated with one wheel of the motor vehicle, said wheel brake being able to operate in consideration of manual actuation of the brake pedal are electronically steered; and the brake pedal sensor unit. The motor vehicle also has a drive system with: a brake pedal; a drive device for longitudinal control of the motor vehicle, which can be electronically actuated taking into account manual actuation of the accelerator pedal; and Accelerator pedal sensor unit. A fault associated with a braking system of a motor vehicle is identified. Due to the identified fault, the brake pedal sensor unit is inoperative.

The method includes applying the at least one wheel brake with a predetermined base braking torque. If the accelerator pedal is actuated, accelerator pedal actuation information is detected by means of the accelerator pedal sensor system, which describes the actuation path of the accelerator pedal covered by the actuation. If the detected accelerator pedal actuation information is smaller than the accelerator pedal actuation limit value, the at least one wheel brake is acted upon with a special case braking torque which is smaller than the basic braking torque. If the detected accelerator pedal actuation information is greater than or equal to the accelerator pedal actuation limit value, determining acceleration information describing the acceleration of the motor vehicle, applying a failure case acceleration determination criterion to the detected accelerator pedal actuation information, And the drive unit is actuated in such a way that the motor vehicle is accelerated according to the acceleration information.

An embodiment of the third aspect provides that, taking into account the detected accelerator actuation information, no acceleration of the motor vehicle takes place if the detected accelerator actuation information is smaller than the accelerator actuation limit value.

In addition, the determined acceleration information can be smaller than typical acceleration information, which applies to the detected acceleration criteria different from the fault-case acceleration determination criteria and which is applied when the fault is not confirmed. Determined in the case of accelerator pedal actuation information.

Furthermore, the embodiment of the third aspect may be configured such that, after the accelerator pedal is manipulated, the at least one wheel brake is loaded with a preset additional braking torque greater than the basic braking torque.

In addition, if the accelerator pedal is manipulated again and the accelerator pedal manipulation information detected at the time of the renewed manipulation is greater than or equal to the accelerator pedal manipulation limit value, when applying the repetitive situation acceleration determination criterion to the detected accelerator pedal manipulation information In case of repeated case acceleration information is determined, which describes an acceleration of the motor vehicle which is less than the acceleration determined when the fault case acceleration determination criterion is applied, and the drive unit is actuated in this way, The motor vehicle is accelerated according to the acceleration information of the repetitive situation.

According to an embodiment of the third aspect, a retraction speed value may be determined, said retraction speed value describing the speed of retraction of said accelerator pedal actuation, and if said retraction speed value is greater than a withdrawal speed limit value, then The at least one wheel brake is acted upon with a retraction braking torque that is greater than the base braking torque.

The motor vehicle can have a surroundings sensor device and sensor data describing at least one surroundings of the area in front of the motor vehicle can be detected by means of the surroundings sensor device, wherein after applying an obstacle detection criterion to the detected sensor Obstacles in the surroundings of the front area are detected without data, and if the obstacles are detected, the at least one wheel brake is acted upon with an obstacle-specific braking torque that is greater than the base braking torque.

Another aspect of the invention relates to a motor vehicle according to the invention. The motor vehicle is designed to carry out the method described above according to one of the other aspects, one of the exemplary embodiments and/or a combination of several exemplary embodiments. The exemplary embodiments described in connection with the method according to the invention and their advantages are correspondingly applicable to the motor vehicle according to the invention as long as they can be used. Motor vehicles are, for example, passenger cars, trucks, buses or motorcycles.

The invention also includes combinations of features of the described embodiments.

Description of drawings

Embodiments of the present invention are described below. to this end:

Figure 1 shows a schematic diagram of a motor vehicle;

2 shows a schematic diagram of a signal flow diagram of a method for informing a driver of a motor vehicle of a fault associated with a braking system of the motor vehicle;

3 is a schematic diagram of the relationship between brake pedal manipulation information and braking torque information;

Fig. 4 schematically shows a signal flow diagram according to other method steps of the method of Fig. 2;

5 shows a schematic illustration of a signal flow diagram of a method for informing a driver of a motor vehicle of a fault associated with an energy supply of the motor vehicle;

6 shows a schematic illustration of a signal flow diagram of a method for informing a driver of a motor vehicle of a non-functioning brake pedal sensor arrangement;

FIG. 7 shows a schematic diagram of the relationship between accelerator pedal actuation information and braking torque information or acceleration information.

Fig. 8 schematically shows a signal flow diagram of the method steps for determining the acceleration information of repeated cases;

FIG. 9 schematically shows a signal flow diagram of the method steps for determining the retraction braking torque;

FIG. 10 schematically shows a signal flow diagram of the method steps for determining the braking torque in the event of an obstacle;

FIG. 11 shows a schematic diagram of the relationship between the energy content of the energy supply of a motor vehicle and the driving power or braking torque information.

Detailed ways

The embodiments explained below are preferred embodiments of the present invention. In the exemplary embodiments described, the components described are each individual features of the invention which are to be considered independently of one another, which also expand the invention independently of one another and are therefore also intended individually or in combination with the ones shown Different combinations are considered as part of the invention. Furthermore, the described exemplary embodiments can also be supplemented by other features of the invention that have already been described.

In the figures, functionally identical elements are provided with the same reference symbols.

A motor vehicle 1 is depicted in FIG. 1 . Motor vehicle 1 has a brake system which includes a brake pedal 2 . Brake pedal 2 can be manually actuated by the driver of motor vehicle 1 . Motor vehicle 1 has four wheels 3 , more precisely two front wheels and two rear wheels. At least one wheel brake 4 of a braking system is associated with each of the wheels 3 of the motor vehicle 1 . Preferably, two wheel brakes 4 , more precisely a hydraulic brake and an electric parking brake, are respectively associated with the two rear wheels 3 . Motor vehicle 1 has at least one of wheel brakes 4 , wherein the motor vehicle has a total of six wheel brakes 4 in the example shown here. Taking into account the manual actuation of brake pedal 2 , the corresponding wheel brakes 4 can be electronically actuated. The braking system of the motor vehicle 1 is thus a brake-by-wire braking system.

A control device 5 is associated with the braking system, which is designed to act upon the individual wheel brakes 4 with a predetermined braking torque. To detect the actuation of brake pedal 2 , the brake system has a brake pedal sensor device 6 . Control unit 5 is supplied with data from brake pedal sensor system 6 . The control device 5 is designed to actuate the wheel brakes 4 . The control device 5 can be a computing device and in particular have a processor device.

Motor vehicle 1 has an accelerator pedal 7 . Strictly speaking, motor vehicle 1 has a drive system with an accelerator pedal 7 and a drive device 8 for longitudinal control of motor vehicle 1 . Taking account of the manual actuation of the accelerator pedal 7 , the drive device 8 can be electronically actuated. Motor vehicle 1 therefore has a drive-by-wire drive system.

The drive system has a drive control device 9 which is designed to actuate the drive device 8 . The drive control device 9 is designed to evaluate the actuation of the accelerator pedal 7 and to control the drive device 8 taking into account the manual actuation of the accelerator pedal 7 . The drive device 8 is, for example, an electric motor or an internal combustion engine.

The drive system also has an accelerator pedal sensor system 10 which is designed to detect an actuation of the accelerator pedal 7 and transmit the corresponding detected data to the drive control device 9 so that the drive control device can take into account In the case of manual actuation of accelerator pedal 7 , drive unit 8 is actuated electronically.

Motor vehicle 1 has an energy supply 11 . The energy supply 11 is designed to supply at least the braking system and the drive system with electrical energy. If motor vehicle 1 is an electric vehicle or a hybrid vehicle, energy supply 11 is, for example, a battery, for example a high-voltage battery.

Motor vehicle 1 has a surroundings sensor device 39 by means of which at least one surroundings 40 in the area in front of motor vehicle 1 can be detected.

FIG. 2 depicts method steps of a method for notifying the driver of motor vehicle 1 of a fault 12 associated with the braking system of motor vehicle 1 . In method step S1 , it is detected that a fault 12 is associated with the braking system of motor vehicle 1 . Despite the detection of the fault 12 , the brake pedal sensor system 6 is still functional, the at least one wheel brake 4 is still actuatable and the brake pedal 2 is still actuatable. For example, fault 12 is a leakage of hydraulic fluid of a hydraulic brake as wheel brake 4 . Despite this leak, for example at least one wheel brake 4 associated with a wheel 3 of the motor vehicle 1 , for example an electric parking brake or another hydraulic brake which is not affected by the leak, is still actuatable.

In method step S2 , brake pedal actuation information 13 can be detected by means of brake pedal sensor device 6 . Brake pedal actuation information 13 describes the actuation travel covered by the actuation of brake pedal 2 . Finally, brake pedal actuation information 13 describes how strongly the driver is actuating brake pedal 2 .

In method step S3 , a fault-case braking torque determination criterion 14 can be applied to detected brake pedal actuation information 13 , wherein braking torque information 15 is determined. Braking torque information 15 describes a braking torque for the at least one wheel brake 4 of motor vehicle 1 . In a further method step S4 , the at least one wheel brake 4 can be acted upon with the braking torque described by the determined braking torque information 15 . Method steps S3 and S4 are preferably carried out by means of the control device 5 of the brake system.

FIG. 3 shows a diagram in which brake pedal actuation information 13 is plotted on the x-axis and brake torque information 15 is plotted on the y-axis arranged perpendicularly to the x-axis. When fault case braking torque determination criterion 14 is applied in method step S3 , braking torque information 15 , which is specified as curve 14 according to the solid line, is associated with corresponding brake pedal actuation information 13 . In contrast, the course of the braking torque information 15 , which was determined using the normal-case braking torque determination criterion 17 , is also depicted by a solid line as a curve 17 . If fault 12 is not acknowledged, the normal-case braking torque determination criterion always applies. These two standards are different from each other.

The braking torque information 15 determined when applying the fault-case braking torque determination criterion 14 is characterized in that if the actuation travel traveled is less than at least three minutes of the maximum actuation travel 16 that can be traveled maximally when the brake pedal 2 is actuated One 19, the determined braking torque is less than one-third 19 of the typical braking torque. A typical braking torque is the braking torque determined when applying the normal-case braking torque determination criterion 17 to the detected braking torque information 15 . In the first third 19 of the maximum actuation travel 16 as brake pedal actuation information 13 , the correspondingly determined braking torque information 15 is therefore at maximum represented using the normal-case braking torque determination criterion 17 one-third of the corresponding value of the curve 19 .

If the maximum actuation travel distance 16 is traversed when the brake pedal 2 is actuated, then the determined braking torque information 15 assumes the maximum braking torque 18 . The maximum braking torque 18 is the maximum braking torque with which the at least one wheel brake 4 can be acted upon. The two curves depicted here intersect at least at this point, that is, at the maximum actuation travel distance 16 at the maximum braking torque 18 , to be more precise when the fault case braking torque determination criterion 14 is applied. The curve 14 of , intersects the curve 17 determined using the normal-case braking torque determination criterion 17 .

In the second or third third of the brake pedal actuation information 13, the determined braking torque information 15 is preferably increased, wherein, for example, initially in the second third, for example, with The third third is an increase of the weaker boost compared to the set braking torque information 15 .

In FIG. 3 , an alternative course of the determined braking torque information 15 is depicted as a curve 14 ′ by dashed lines. This trend is determined using an alternative fault-case braking torque determination criterion 14 ′, wherein the alternative fault-case braking torque determination criterion 14 ′ differs from the fault-case braking torque determination criterion 14 . In the depicted example for the curve 14 ′, the determined braking torque information 15 is zero in the first third 19 of the maximum actuation travel 16 , ie in this region despite the actuation of the brake pedal No braking of motor vehicle 1 takes place in . For example, in the second and third thirds of the maximum actuation travel 16, a steeper rise of the determined braking torque information 15 is provided, wherein the maximum braking is reached again at the maximum actuation travel 16. Power moment 18.

Further method steps S5 to S8 are depicted in FIG. 4 . In method step S5 , in particular an actuation speed value 20 is determined. For this purpose, for example, a corresponding temporal evaluation of the brake pedal actuation information 13 can be carried out by means of the control device 5 . Actuation speed value 20 describes the speed of actuation of brake pedal 2 . It can then be checked in method step S6 whether the determined actuation speed value 20 is greater than the actuation speed limit value 21 . If this is the case, in method step S7 the normal situation braking torque determination criterion 17 can be applied to the detected brake pedal actuation information 13 so that the second power plant braking torque information 15 and then according to method step S4 The at least one wheel brake 4 is applied. Alternatively, method step S8 may be carried out, according to which intermediate case braking torque determination criterion 22 is applied to detected brake pedal actuation information 13 , wherein braking torque information 15 is determined. An intermediate case braking torque determination criterion 22 associates with each brake pedal actuation information 13 a braking torque information 15 which can alternatively be referred to as an intermediate case braking torque determination criterion and is greater than the Braking torque information 15 determined in the case of a dynamic torque determination criterion 14 . Method step S4 can then be carried out again, namely applying the at least one wheel brake 4 as a function of the braking torque information 15 .

FIG. 5 shows a possible method in addition to or as an alternative to the method described above, in which a fault 12 ′ associated with energy supply 11 of motor vehicle 1 is detected in method step S1 ′. Despite the detection of a fault 12 ′ associated with the energy supply 11 , the at least one wheel brake 4 and the drive unit 8 can be actuated taking into account a corresponding manual actuation of the pedal. This means that not only brake pedal 2 but also brake pedal sensor device 6 as well as accelerator pedal 7 and accelerator pedal sensor device 10 continue to function. However, there is a fault 12 ′ which concerns at least the current or future energy supply 11 of the braking system as well as the drive system with electrical energy.

The actuation of brake pedal 2 can be observed in method step S9 . The accelerator pedal 7 is then preferably actuated in procedural step S10 , followed by a wait, in particular in procedural step S11 , for a waiting period 23 . The waiting period 23 may alternatively be referred to as a dead time. Only when waiting period 23 has been waited, in particular in method step S12 , motor vehicle 1 is accelerated by means of drive unit 8 taking into account manual actuation of accelerator pedal 7 . A permissible delay in the acceleration of motor vehicle 1 thus occurs despite the actuation of accelerator pedal 7 . After method step S1 ′, ie after detection of fault 12 ′ associated with energy supply 11 or after method step S12 , current propulsion power 24 is reduced. This is achieved by correspondingly actuating drive unit 8 and/or at least one wheel brake 4 . Ultimately, the speed of motor vehicle 1 is thus reduced.

After method step S1 ′ and/or method step S12 , it can also be provided in method step S14 that the electric parking brake as wheel brake 4 is permanently activated. The electronic parking brake is preferably arranged on one of the rear wheels 3 of the motor vehicle 1 . This leads to the fact that in the event of failure of the energy supply part 11 , braking is continued with the permanently activated parking brake, since the parking brake remains active despite the failure of, for example, the drive unit 8 and other elements of the braking system. status. Motor vehicle 1 can thus be braked to a standstill, for example after energy supply 11 has actually failed.

Additional or alternative method steps S1 ″ and S15 to S20 are depicted in FIG. 6 . In this case, in method step S1 ″, a fault 12 ″ is detected, due to which the brake pedal sensor system 6 cannot function. In a subsequent method step S15 , the at least one wheel brake 4 is acted upon with a predetermined basic braking torque 25 . If accelerator pedal 7 is now actuated, for example by the driver, accelerator pedal actuation information 26 is detected by means of accelerator pedal sensor device 10 in method step S16 . Accelerator pedal actuation information 26 describes the actuation path covered by the actuation of accelerator pedal 7 . It is then checked in method step S17 whether detected accelerator pedal actuation information 26 is smaller than accelerator pedal actuation limit value 27 . If this is the case, the at least one wheel brake 4 is preferably acted upon in a method step S18 with a special case braking torque 28 which is lower than the basic braking torque 25 . This results in weakened braking of motor vehicle 1 . At the same time, however, motor vehicle 1 is not accelerated further, since motor vehicle 1 is not accelerated in this case taking into account detected accelerator pedal actuation information 26 .

If detected accelerator pedal actuation information 26 is greater than or equal to accelerator pedal actuation limit value 27 , fault case acceleration determination criterion 29 may be applied to detected accelerator pedal actuation information 26 in method step S19 . Here, acceleration information 30 is measured. This describes the acceleration of motor vehicle 1 . In method step S20 , in particular drive unit 8 is actuated in such a way that motor vehicle 1 is accelerated according to acceleration information 30 .

FIG. 7 depicts a graph in which the accelerator pedal actuation information 26 is given on the x-axis, and the braking torque information 15 is given on the downward-pointing y-axis and on the upward-pointing y-axis. Acceleration information 30 is given. The curve 29 of the accelerator actuation information 26 , which is determined when the fault-case acceleration determination criterion 29 is applied, is plotted here with a solid line in the case of the preset braking torque information 15 . In the non-faulty situation and using the normal-case acceleration determination criterion 31 , the acceleration of the motor vehicle 1 increases, ie the acceleration information 30 increases as the accelerator pedal actuation information 26 increases, as shown as curve 31 .

Using the fault-case acceleration determination criterion 29 , the at least one wheel brake 4 is initially purely acted on with the base braking torque 25 , if the accelerator pedal 7 has not yet been actuated. As soon as the accelerator pedal 7 is actuated until the accelerator pedal actuation limit value 27 is reached, the motor vehicle 1 is not yet accelerated, but the motor vehicle is braked further, ie a specific braking torque information 15 greater than zero is respectively preset. This corresponds to a corresponding special case braking torque 28 . The motor vehicle 1 is accelerated only when the accelerator pedal actuation information 26 is greater than or equal to the accelerator pedal actuation limit value 27 , wherein the acceleration is lower than with the same accelerator pedal actuation information 26 when applying the normal-case acceleration determination criterion 31 acceleration.

FIG. 7 also depicts a pre-accelerator pedal actuation limit value 32 which is located before the accelerator pedal actuation limit value 27 and after reaching this pre-accelerator pedal actuation limit value despite greater accelerator pedal actuation The information 26 neither presets braking, that is, does not preset braking torque information 15 greater than zero, nor preset acceleration information 30 greater than zero. A free travel can thus be provided between the pre-accelerator actuation limit value 32 and the accelerator actuation limit value 27 .

If, after actuation of the accelerator pedal 7 , a situation occurs in which neither the brake pedal 2 nor the accelerator pedal 7 is actuated, the base braking torque 25 is increased up to the additional braking torque 33 . After the accelerator pedal 7 has been actuated, the at least one wheel brake 4 is thus acted upon with a predetermined additional braking torque 33 which is greater than the basic braking torque 25 . The corresponding course when the accelerator pedal 7 is then actuated again is depicted as a dotted line as a curve 29 ′, this being determined using an alternatively designed fault case acceleration determination criterion 29 ′. If the accelerator pedal actuation information 26 is now reconfirmed so large that it is greater than or equal to the accelerator pedal actuation limit value 27 , then in the case of repeated case acceleration determination criteria 34 for the detected accelerator pedal actuation information 26 2 Plant acceleration information 30 which is less than the acceleration determined when the fault-case acceleration determination criterion 29 is applied.

The individual method steps already apparent from FIG. 7 are described in detail in FIG. 8 . In method step S21 , accelerator pedal 7 is actuated again after accelerator pedal 7 has been actuated for the first time. In this case, newly detected accelerator actuation information 26 ′ is determined by means of accelerator sensor system 10 . It is then preferably checked in method step S22 whether the newly detected accelerator pedal actuation information 26 ′ is smaller than the accelerator pedal actuation limit value 27 . If this is the case, a special case braking torque 28 which is smaller than the basic braking torque 25 and the additional braking torque 33 can be determined in method step S23 .

If it is confirmed in method step S22 that the newly detected accelerator pedal actuation information 26 ′ is greater than or equal to the accelerator pedal actuation limit value 27 , then in method step S24 the repeated case acceleration determination criterion 34 can be applied to the newly detected accelerator pedal actuation information 26 ', and the repeated case acceleration information 35 is measured here. Then, preferably in method step S25 , an acceleration of motor vehicle 1 , ie a corresponding actuation of drive unit 8 , takes place on the basis of repetitive acceleration information 35 . In this case, the repeated case acceleration information 35 replaces the acceleration information 30 determined when the accelerator pedal 7 was actuated for the first time. As an alternative to repeating the expression of the case acceleration information 35 , this can be referred to as the acceleration information 30 when the accelerator pedal 7 is actuated for the second time.

Method steps S26 to S28 are depicted in FIG. 9 , which, for example, can directly follow method step S20 , but can also follow method step S23 or S25 . In method step S26 , in particular a retraction speed value 36 is determined, which describes in particular the speed at which the actuation of accelerator pedal 7 is retracted. In method step S27 it can be checked whether the retraction speed value 36 is greater than the retraction speed limit value 37 . If this is the case, the at least one wheel brake 4 is preferably acted upon in a method step S28 with a retraction braking torque 38 which is greater than the base braking torque 25 . Intensified braking is thereby achieved, ie the applied braking torque is increased in dependence on the braking torque information 15 . If the check is negative in method step S27 , for example, the method can be terminated, or method step S26 can be executed again.

Method steps S29 to S32 are depicted in FIG. 10 , which may, for example, follow method steps S20 , S23 , S25 and/or S28 . According to method step S29 , sensor data 41 are recorded by means of surroundings sensor device 39 of motor vehicle 1 , which describe at least surroundings 40 of the area in front of motor vehicle 1 . In method step S30 , obstacle detection criteria 42 are then preferably applied to detected sensor data 41 . In method step S31 , obstacles 43 in surroundings 40 of the area ahead can then be detected and identified. If, for example, no obstacle 43 has been detected in method step S31 , method step S29 can be carried out again, or alternatively the method can be terminated. If an obstacle 43 is detected, the at least one wheel brake 4 can be acted upon in a method step S32 with an obstacle-case braking torque 44 which is greater than the basic braking torque 25 . In the event of an obstacle, stronger braking of motor vehicle 1 is thus achieved independently of the actuation of accelerator pedal 7 .

FIG. 11 shows a diagram in which an energy content 45 of an energy supply 11 , for example a high-voltage battery of the motor vehicle 1 , is plotted on the x-axis. Both the driving power 46 and the braking torque information 15 are plotted on the y-axis. Furthermore, driving power 46 is depicted as a solid line as a function of energy content 45 , the line having three regions. Driving power 46 initially increases linearly in a first range between zero energy content 45 and maximum energy content 47 , then extends continuously in a second range, and then rises abruptly to the level of a third range. The second area describes sufficient residual energy 48 to supply the braking system and drive system of motor vehicle 1 with energy. A critical energy region is located in the first region, which is referred to as the critical state 49 . A maximum energy content 47 is provided in the third region. It is clear that there is always a high driving power 46 in the region with sufficient residual energy 48 and in the adjoining region with the greatest energy content 47 . However, the driving performance continues to decrease in the first range of the critical state 49 . From the beginning of the first range, the electronic parking brake can be transferred, for example, to a permanently active state, wherein firstly the acceleration of the motor vehicle 1 can continue to be set because, for example, despite the critical state 49 of the energy supply part 11, the drive system can still continue 8 provides energy. However, as soon as the energy content 45 has reached zero, as depicted here with a dotted line, braking torque information 15 is obtained from the active parking brake, so that the motor vehicle 1 can be braked.

Overall, these examples show a method for actuating a braking system at backup level. In order to be able to provide a tactile feedback, ie a tactile feedback, to the brake pedal 2 without its own feedback actuator, a relatively wide free travel is provided. This means that in the case of a fault, ie when a fault 12 occurs, a lower braking deceleration is set with the same pedal actuation of the brake pedal 2 than in the case of no fault. This is accomplished by applying the failure-case braking torque determination criterion 14 and the reduction of the braking torque information 15 selected in FIG. 3 for the first third 19 of the maximum actuation travel 16 instead of the normal-case braking torque determination criterion 17 accomplish. This approach corresponds in part to failure modes or failure diagrams of brake control systems, in which, in the event of an electronic failure, the driver first has to go through an idle travel before he can brake with the hydraulic back-up level. In an advantageous manner, a rolling deceleration of the vehicle can still be achieved with maximum pedal actuation, ie when the maximum actuation travel 16 is reached, ie a maximum braking torque 18 for applying the at least one wheel brake 4 is then preset . Thus, for example, emergency braking situations and unnecessarily long braking travels can be prevented. It is not important here whether the critical fault state exists due to a fault 12 in the driver's brake detection or a fault in the brake actuator or a fault at the wheel brakes 4 themselves.

In a brake-by-wire braking system, a fault 12 ′ in the energy supply 11 also leads to an at least partial failure of the braking system. What is critical here is in particular the complete loss of the energy supply 11 and the degradation of the energy supply 11 (it no longer enables normal braking). In these cases, early intervention is imperative. It is advantageous here that by clever monitoring of the energy supply 11, for example by measuring the cell voltages in the battery as energy supply 11, the failure of the energy supply 11 can be detected with a small lead time of, for example, one minute. Completely ineffective. If the energy supply 11 is particularly critical, further upgrading steps can be taken in order to prevent, for example, an unbraked, uncontrollable motor vehicle 1: reduction of the propulsion power 24; reduction of the driving speed by targeted braking interventions ; produce a permanent braking intervention that is maintained even in the event of a loss of the voltage supply, ie the energy supply 11 (for example, when the valve is closed without current, by using electric parking brake or lock the brake pressure in the wheel brake 4); display a fault 12' in the energy supply part 11 in such a way that, after braking, the propulsion force can only be adjusted with a delay, that is, by releasing the brake and actuating The dead time in the form of a preset waiting period 23 is adjusted when accelerating the pedal 7 . In the event of a fault, the possibility of simultaneous activation of the drive unit 8 and the at least one wheel brake 4 is very limited. As a result, in the event of a sudden voltage drop, ie in the event of a complete failure of the energy supply 11 , the braking force on the wheel on which the at least one activated wheel brake 4 is arranged is maintained. The failure of energy supply 11 is particularly noteworthy if at the same time the steering system of motor vehicle 1 is no longer functional. This is the case, for example, in steer-by-wire vehicles in which further steering of the motor vehicle, ie lateral guidance of the motor vehicle 1 , can no longer be steered in the event of a complete failure of the energy supply 11 . It is therefore important to stop the motor vehicle 1 in good time in this situation. In this case, therefore, it makes sense to bring motor vehicle 1 to a standstill in a targeted manner.

A failure of the brake pedal sensor system 6 is, however, unlikely, since a redundant voltage supply, signal detection and evaluation is usually provided for the electric brake pedal 2 . However, it is still conceivable that the brake pedal sensor device 6 and thus the sensing of the driver's desire to brake fail. Therefore, an additional backup level for detecting the driver's desire to brake is expedient. If it is now assumed that the detection of the driver's desire to brake via the brake pedal 2 is completely disabled, a minimum deceleration can be achieved by the brake system without actuating the accelerator pedal 7 by using the basic braking torque 25 And the at least one wheel brake 4 is acted upon with a basic braking torque. If the driver then actuates the accelerator pedal 7 , this leads to a retraction of the braking deceleration in the case of a small actuation, that is to say, the at least one wheel brakes4. In the event of a stronger maneuver, however, motor vehicle 1 then accelerates, that is to say fault-case acceleration determination criterion 29 is applied and acceleration information 30 is determined. Due to the reduced braking performance, the acceleration or propulsion force can be reduced in turn. If the driver of the motor vehicle 1 accepts this type of operation of the motor vehicle 1, the deceleration, ie the basic braking torque 25, can be increased after the first acceleration, or more precisely to the additional braking torque 33, by This can present a noticeable deceleration to the driver. When the accelerator pedal 7 is released particularly quickly, a greater deceleration can also be set, that is to say, the retraction braking torque 38 can be selected and braked with the retraction braking torque 38 . The deceleration can also be increased if the driver activates the electric parking brake when the brake pedal 2 fails. Eventually, this can happen up to full deceleration. If an obstacle 43 is detected in the area ahead via a surroundings detection device, such as a front radar or a camera, ie by means of the surroundings sensor device 39 , a higher deceleration can also be set, that is to say with an obstacle braking torque. 44 applies the at least one wheel brake 4 .

List of reference signs

1 motor vehicle

2 brake pedal

3 wheels

4 wheel brakes

5 control equipment

6 Brake pedal sensor unit

7 accelerator pedal

8 drive equipment

9 drive control equipment

10 accelerator pedal sensor unit

11 Energy supply parts

12, 12', 12'' failure

13 Brake pedal actuation information

14 Criteria for Determination of Braking Torque in Fault Conditions

15 Braking torque information

16 Maximum operating stroke

17 Standards for determining braking torque under normal conditions

18 Maximum braking torque

19 first third

20 Manipulation speed value

21 Control speed limit value

22 Determination criteria for intermediate braking torque

23 waiting time

24 propulsion power

25 Base braking torque

26, 26' accelerator pedal operation information

27 Accelerator pedal actuation limit value

28 Braking torque in special cases

29 Acceleration Determination Criteria for Fault Conditions

30 Acceleration Information

31 Determination standard of acceleration under normal conditions

32 Pre-accelerator pedal actuation limit value

33 Additional braking torque

34 Determination criteria for acceleration in repetitive situations

35 Repeat case acceleration information

36 Retracement speed value

37 Retraction speed limit value

38 Retraction braking torque

39 Surroundings sensor unit

40 Surroundings

41 Sensor data

42 Obstacle recognition standard

43 obstacles

44 Braking torque in case of obstacles

45 energy content

46 driving power

47 Maximum energy content

48 remaining energy

49 critical state

S1-S32 Method steps

S1', S1'' Method steps.

Claims (15)

1. A method for informing a driver of a motor vehicle (1) of a fault (12) associated with a braking system of the motor vehicle (1), wherein the braking system has: a brake pedal (2); at least one wheel brake (4) associated with a wheel (3) of said motor vehicle (1), said wheel brake being capable of taking into account manual actuation of said brake pedal (2) is electronically actuated; and a brake pedal sensor device (6), wherein the method has the steps of: - acknowledging (S1) a fault (12) associated with the braking system of said motor vehicle (1), wherein the brake pedal sensor device (6) is still functional despite the acknowledging of the fault (12), so said at least one wheel brake (4) is still operable, and said brake pedal (2) is still operable; and - if the brake pedal (2) is actuated, • Detection (S2) of brake pedal actuation information (13) by means of the brake pedal sensor device (6), which describes the actuation path of the brake pedal (2) which is covered by the actuation ; • Determination (S3) of braking torque information (15) with the application of the fault-case braking torque determination criterion (14) to detected brake pedal actuation information (13), which describes the braking torque information for the The braking torque of the at least one wheel brake (4), wherein, if the actuating stroke covered is less than at least one-third of the maximum actuating stroke (16) that can be traversed when the brake pedal (2) is actuated ( 19), then the measured braking torque is less than one-third (19) of the typical braking torque that will be different from the fault condition braking torque determination criteria (14) and at The normal situation braking torque determination criterion (17) applied when the fault (12) is not confirmed is determined when it is applied to the detected brake pedal actuation information (13), but if the maximum actuation stroke ( 16), the determined braking torque information (15) describes the maximum braking torque (18) with which the at least one wheel brake (4) can be loaded; and • Applying (S4) the at least one wheel brake (4) with a braking torque described by the determined braking torque information (15). 2. The method according to claim 1, wherein the determined braking torque information (15) is zero if the actuation travel traveled is less than one-third (19) of the maximum actuation travel (16) . 3. The method according to any one of the preceding claims, wherein an actuation speed value (20) is determined (S5) describing the speed of actuation of the brake pedal (2), and if the If said control speed value (20) is greater than the control speed limit value (21) (S6), then apply (S7) normal situation braking torque determination criteria (17). 4. The method according to any one of claims 1 or 2, wherein an actuation speed value (20) is determined (S5) describing the speed of actuation of the brake pedal (2), and If the actuation speed value (20) is greater than the actuation speed limit value (21) (S6), the intermediate case braking torque determination criterion (22) is applied for each brake pedal actuation The information (13) is associated (S8) with an intermediate case braking torque information which is greater than the measured braking torque information ( 15). 5. The method according to any one of the preceding claims, wherein the motor vehicle (1) has an energy supply (11) and a drive system with an accelerator pedal (7) and for longitudinal controlling a drive unit (8) of the motor vehicle (1), which drive unit can be electronically actuated taking into account manual actuation of the accelerator pedal (7), wherein - Acknowledging (S1') a fault (12') associated with said energy supply (11), wherein said at least one wheel brake (4) and said drive device (8) are still actuatable taking into account the corresponding manual actuation; and - if the brake pedal (2) and subsequently the accelerator pedal (7) of the motor vehicle (1) is actuated (S9, S10), taking into account the manual actuation of the accelerator pedal (7) Consequently, acceleration of the motor vehicle (1) by means of the drive unit (8) is permitted (S11, S12) only after a predetermined waiting period (23). 6. The method according to claim 5, wherein the drive device (8) and/or the at least one Wheel brakes (4) such that the current propulsion power (24) of the motor vehicle (1) is reduced (S13). 7. The method according to any one of claims 5 or 6, wherein the at least one wheel brake (4) is an electric parking brake which, in connection with the energy supply (11 ) associated faults (12') are then brought to a permanently active state, wherein the motor vehicle (1) is able to Continue to be driven (S14). 8. The method according to any one of the preceding claims, wherein the motor vehicle (1) has a drive system with: an accelerator pedal (7); for longitudinally controlling the motor vehicle ( 1) a drive device (8), which can be electronically actuated taking into account the manual actuation of the accelerator pedal (7); and an accelerator pedal sensor device (10), and since the identified and the A fault (12'') associated with the brake system of the motor vehicle (1), the brake pedal sensor device (6) is inoperative (S1''), wherein - loading (S15) the at least one wheel brake (4) with a preset basic braking torque (25); - if the accelerator pedal is actuated, • detecting (S16) accelerator pedal actuation information (26) by means of the accelerator pedal sensor device (10), said accelerator pedal actuation information describing the actuation travel of the accelerator pedal (7) as a result of the actuation; • If the detected accelerator pedal manipulation information (26) is less than the accelerator pedal manipulation limit value (27) (S17), apply (S18) the at least one wheel brake (4) with a special case braking torque (28), so The above-mentioned special case braking torque is less than the basic braking torque (25); • If the detected accelerator pedal manipulation information (26) is greater than or equal to the accelerator pedal manipulation limit value (27) (S17), after applying the fault condition acceleration determination criterion (29) to the detected accelerator pedal manipulation information (26) determine (S19) acceleration information (30) describing the acceleration of the motor vehicle (1), and operate (S20) the drive device (8) in such a way that the motor vehicle (1) according to the acceleration Information (30) accelerated. 9. The method according to claim 8, wherein, if the detected accelerator pedal manipulation information (26) is smaller than the accelerator pedal manipulation limit value (27), when considering the detected accelerator pedal manipulation information (26) The acceleration of the motor vehicle (1) does not take place in the case of 10. The method according to any one of claims 8 or 9, wherein the measured acceleration information (30) is smaller than the typical acceleration information (30) which is to be compared with the fault condition acceleration The normal-case acceleration determination criterion (17), which differs from the determination criterion (14) and which is applied when the fault (12) has not been detected, is determined in the case of the detected accelerator pedal actuation information (13). 11. The method according to any one of claims 8 to 10, wherein, after actuating the accelerator pedal (7), with a preset additional braking torque ( 33) Applying said at least one wheel brake (4). 12. The method according to claim 11, wherein if the accelerator pedal (7) is re-operated (S21) and the accelerator pedal manipulation information (26') detected at the re-manipulation is greater than or equal to the accelerator pedal manipulation limit value (27) (S22), the repetitive situation acceleration information (35) is then determined (S24) while applying the repetitive situation acceleration determination criterion (34) to said detected accelerator pedal actuation information (26'), The repeated case acceleration information describes an acceleration of the motor vehicle (1) which is less than the acceleration determined when the fault case acceleration determination criterion (14) is applied, and the drive unit is actuated (S25) in this way (8), causing the motor vehicle (1) to accelerate according to the acceleration information (35) of the repeated situation. 13. The method according to any one of claims 8 to 11, wherein a retraction velocity value (36) is determined (S26) which describes the retraction of the actuation of the accelerator pedal (7) speed, and if the retraction speed value (36) is greater than the retraction speed limit value (37) (S27), load ( S28) The at least one wheel brake (4). 14. The method according to any one of claims 8 to 13, wherein the motor vehicle (1) has a surroundings sensor device (39) and the vehicle is described by means of the surroundings sensor device detection (S29). Sensor data (41) of at least one surrounding environment (40) of the area in front of the motor vehicle (1), wherein the determination ( S30) an obstacle (43) in the surrounding environment (40) of the front area, and if the obstacle (43) is detected (S31), then with an obstacle greater than the basic braking moment (25) A situational braking torque (44) acts (S32) the at least one wheel brake (4). 15. A motor vehicle (1) having a braking system, wherein the motor vehicle (1) is designed to carry out the method as claimed in any one of the preceding claims.

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