Method and control device for automatic brake regulation of a motor vehicle

Abstract

The invention relates to a method (16) and to a control device (6) for automatic brake regulation of a motor vehicle (1). The invention also relates to a correspondingly configured motor vehicle (1). In the method (16), it is determined for a braking manoeuvre in each case to be carried out whether it is a standard braking manoeuvre within predefined safety limits or an emergency braking manoeuvre. If it is an emergency braking manoeuvre, use is made of control characteristics which are predefined only for this purpose and differ from standard control characteristics predefined only for standard braking manoeuvres, in order to control the actuation of a brake device (2, 3) of the motor vehicle (1) for carrying out the braking manoeuvre.

Description

[0001] Method and control device for automatic braking control of a motor vehicle

[0002] The present invention relates to a method and a control device for automatic braking control of a motor vehicle. The invention further relates to a correspondingly configured motor vehicle.

[0003] Today, efforts are being made to support the driving of motor vehicles with assistance systems or to automate it fully or partially. Approaches to this end already exist, such as automated vehicle longitudinal control or an emergency braking function to avoid or mitigate otherwise unavoidable collisions. However, one challenge is that there are different, at least partially conflicting, objectives. For example, a relatively gentle and smooth deceleration may be desirable for maximum comfort, while the strongest and fastest possible deceleration may be optimal for maximum safety, which is also the goal.

[0004] As one approach, DE 2646288 A1 describes a load-dependent brake force control device for trailer brake systems. It includes an emergency brake valve, a relay valve, and a load-dependent brake force regulator with a brake pressure control valve. The brake pressure control valve is designed as both a relay and emergency brake valve. However, this represents a very specific application that cannot be easily generalized. DE 10 2017 209 846 B4 describes a vehicle with an adaptively overridable emergency braking system. The emergency braking system can be deactivated depending on the power output of a vehicle's engine upon manual intervention by the driver. A vehicle's speed limitation system can also be deactivated.An override threshold is specified for each of these, whereby the override threshold for deactivating the emergency braking system can be changed to the override threshold for deactivating the speed limit system if the override threshold is greater than the override threshold for deactivating the emergency braking system. This is intended to provide a way for the driver to override autonomous emergency braking by the emergency braking system by increasing the engine's power output, even if the speed limit system is actively limiting the vehicle's speed. This provides the driver with the appropriate intervention option for safety reasons.

[0005] The object of the present invention is to enable particularly comfortable and safe operation of a motor vehicle.

[0006] This object is achieved according to the invention by the subject matter of the independent patent claims. Possible embodiments and further developments of the present invention are disclosed in the dependent patent claims, in the description, and in the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

[0007] The method according to the invention can be used for automatic braking control of a motor vehicle. In other words, the method according to the invention can be used, for example, to control a braking system of the motor vehicle or an actuator for applying and releasing a brake or braking device of the motor vehicle. In one method step of the method according to the invention, it is determined for a braking maneuver currently being performed or imminently occurring whether this is a standard braking maneuver within predetermined safety limits or an emergency braking maneuver. The safety limits specified for or defining a standard braking maneuver can be specified, for example, by one or more values ​​of a corresponding safety parameter.Such a safety parameter can, for example, be a distance to an obstacle ahead in the direction of travel of the motor vehicle, a relative speed of the motor vehicle with respect to this obstacle, a deceleration necessary to avoid a collision, i.e., braking acceleration, and / or similar factors. The condition of the motor vehicle and / or environmental conditions can also be taken into account. The condition of the motor vehicle can, for example, relate to its equipment or the deceleration that is technically possible in principle or currently, for example, due to a type of tire, tire pressure, type of braking system, switching or conditioning status of the braking system, temperature of the braking system, occupancy or load of the motor vehicle, presence or absence of a trailer load, and / or similar factors.The environmental conditions may, for example, include or relate to a type or condition of a local surface being traveled on, i.e. a road surface condition or weather conditions influencing it and / or the like.

[0008] A standard braking maneuver can occur during normal vehicle operation, where, for example, a collision can be avoided without exhausting the maximum deceleration, a collision probability is below a predefined probability threshold, and / or similar factors. For such a standard braking maneuver, priority can be given to, for example, comfort for the vehicle's occupants, maximizing recuperation, minimizing wear or emissions, such as brake dust or tire wear, and / or similar factors.

[0009] An emergency braking maneuver, however, may be necessary, particularly in a situation and / or during braking outside the specified safety limits. For such an emergency braking maneuver, the maximum possible deceleration can be exploited or targeted, for example. For the emergency braking maneuver, maximum deceleration or safety can therefore be prioritized over occupant comfort, recuperation, wear, and the like. Such an emergency braking maneuver may be necessary, for example, if it has been determined—for example, by a corresponding assistance system in the vehicle—that this is the only way to avoid an impending collision and / or if the corresponding collision probability is above the specified probability threshold, or similar.

[0010] In a further method step of the method according to the invention, if the braking maneuver to be performed is an emergency braking maneuver, a control characteristic predefined solely for that purpose is used to control the actuation of a braking device of the motor vehicle to execute the braking maneuver. The control characteristic predefined for emergency braking maneuvers, which can also be referred to here as emergency braking control characteristic, differs from a standard control characteristic predefined solely for standard braking maneuvers. At least the emergency braking control characteristic can, in particular, predetermine or define a specific or special dependency or characteristic curve for one or more variables of a corresponding controlled system or a corresponding control loop or a corresponding control device, such as a time constant, a dead time, and / or other control or system parameters.The standard control characteristic can accordingly comprise or define at least one different dependency or characteristic curve or at least one fixed value of one or more route or control parameters to be used only for standard braking maneuvers instead of a corresponding dependency specified for emergency braking maneuvers.

[0011] For example, depending on the type of braking maneuver to be performed, a corresponding control characteristic, such as a corresponding parameterization of a control loop or a controlled system or a control device for the braking maneuver, can be selected and used, i.e., set or activated, from several different predefined control characteristics. Thus, for an emergency braking maneuver, the brake control can be carried out according to the emergency braking control characteristic specified for that purpose, in particular only for that purpose, which can also be referred to as a safety characteristic or a safety control characteristic, and for a standard braking maneuver, the brake control can be carried out according to the standard control characteristic specified for that purpose, in particular only for that purpose, which can also be referred to as a comfort characteristic.The use of the respective control characteristic can, for example, mean or include that a corresponding control device, for example a so-called CVM longitudinal controller (CVM: Central Vehicle Management) is operated with this control characteristic, i.e. in the case of an emergency braking maneuver with the emergency braking or safety control characteristic instead of the standard or comfort control characteristic, or that for an emergency braking maneuver a controller set up according to the emergency braking or safety control characteristic is used instead of a controller set up for the standard or comfort control characteristic or the like.

[0012] As already mentioned at the beginning, with previous automatic braking systems, compromises are often made between different objectives, for example to achieve sufficient safety and sufficient comfort. However, it can be observed that the resulting braking behavior or the resulting follow-up behavior of a brake controller is not always good enough to actually avoid a collision that could have been avoided in principle, for example when the braking system is new, i.e. not yet run in or braked in and / or not yet reached the optimal operating temperature. On the other hand, a relatively long time constant of the brake controller designed as a compromise between safety and comfort can, particularly at relatively low braking torques and relatively low vehicle speeds, lead to longitudinal oscillation of the vehicle, which in turn can impair comfort or even safety.

[0013] These problems can be solved or at least largely avoided by the present invention by differentiating between the standard or comfort control characteristic and the emergency braking or safety characteristic for different braking maneuvers with correspondingly different situation-dependent requirements. In other words, it is proposed here to design the brake control or the corresponding controlled system or control device flexibly so that different automatic actions and controls can be carried out in different ways in different situations. In this way, depending on the situation, optimal comfort or - with a justified and desirable deprioritization of comfort in favor of safety - optimal safety can be achieved without significantly compromising safety in practice. In one possible embodiment of the present invention, the following is defined orThe control characteristic specified for emergency braking maneuvers determines a specified dependency of the controlled system dead time of the controlled system for braking control on the braking torque. This braking torque can, in particular, be the braking torque currently measured or actually applied, for example, at the start of the braking maneuver and / or during the braking maneuver. As part of the method, the current braking torque can be measured or the currently measured braking torque can be recorded as input for the braking control, i.e., a corresponding control device. To define or determine this dependency, the control characteristic can, in particular, comprise a corresponding specified characteristic curve.The dependency of the controlled system dead time on the braking torque proposed here makes it possible, for example, to take into account that the braking system may react differently depending on whether the brake pads are further or closer to the brake disc or are already in contact with it. Likewise, a control deviation can be detected particularly quickly during an emergency braking maneuver, meaning that the brake control system can react accordingly. This can enable particularly effective brake control and thus a particularly quick and safe stopping of the vehicle. In contrast, for standard braking maneuvers, for example, a always or on average longer controlled system dead time can be provided or used, which can improve comfort. The dependency proposed here can also avoid or reduce longitudinal oscillation or rocking of the vehicle, which is possible with previous brake control systems.This may result in improved controllability of the vehicle, even during an emergency braking maneuver.

[0014] In a possible refinement of the present invention, the dependency provides for a shorter controlled system dead time with a larger braking torque magnitude. The controlled system dead time can thus decrease as the braking torque magnitude increases. In other words, an inverse relationship or dependency can exist between the controlled system dead time and the braking torque magnitude, for example. This allows the oscillation or longitudinal vibration of the motor vehicle to be particularly effectively prevented or reduced.

[0015] In a further possible embodiment of the present invention, the control characteristic specified for emergency braking maneuvers defines or determines a specified dependence of a controller time constant of the corresponding controlled system or control device on a respective target deceleration for the braking maneuver. The target deceleration for the respective braking maneuver or during the respective braking maneuver can be recorded as part of the method as input for the brake control, i.e. the corresponding control device. The target deceleration can, for example, be output or provided by a corresponding assistance function, such as an AEB function (Autonomous Emergency Breaking Function) of the motor vehicle. To implement the embodiment of the present invention proposed here, the control characteristic can, in particular, comprise a corresponding characteristic curve.Due to the dependency proposed here, the brake control can react particularly quickly and at the same time particularly safely to changes during an emergency braking maneuver, which can be particularly relevant for an effective, controlled and safe stopping of the vehicle, especially given the typically greater target decelerations in an emergency braking maneuver compared to a standard braking maneuver.

[0016] In a possible further development of the present invention, the dependency provides for a lower controller time constant with a larger target deceleration. The controller time constant can therefore decrease with increasing target deceleration, so that the control system can then react more quickly or have a more pronounced control characteristic. In other words, an inverse relationship or dependency can exist between the controller time constant and the target deceleration, for example. A larger target deceleration means stronger braking. Conversely, a larger controller time constant can be set or used for smaller target decelerations, i.e., correspondingly weaker braking of the vehicle.This allows for the vehicle's longitudinal oscillation or rocking to be avoided or reduced, and for larger target decelerations, which can be particularly safety-relevant, a faster response to changes, disturbances, or control deviations can be achieved. This allows for a particularly effective and safe stopping of the vehicle during an emergency braking maneuver.

[0017] In a further possible embodiment of the present invention, the control characteristic specified for emergency braking maneuvers defines or determines a specified dependency of the controller time constant or a controller time constant on the gradient of the respective target deceleration. This controller time constant can, in particular, be the controller time constant mentioned elsewhere. The respective target deceleration can, in particular, be the target deceleration mentioned elsewhere. The gradient of the target deceleration for the respective braking maneuver or during the respective braking maneuver can be recorded as part of the method as input for the brake control, i.e., the corresponding control device or controlled system, or can be calculated, for example, based on recorded values ​​of the target deceleration during the braking maneuver, in particular in real time.The gradient of the target deceleration can be determined or ascertained, for example, by the AEB function or by the brake control, i.e., the corresponding control device. To implement the embodiment of the present invention proposed here, the control characteristic can, in particular, comprise, define, or implement a corresponding characteristic curve. The dependency proposed here allows for an automatic, appropriate response to relatively slowly changing conditions or situations, as well as to more rapidly changing conditions or situations. This can enable a particularly effective and safe stopping of the motor vehicle.

[0018] In a possible further development of the present invention, the dependency provides for a lower controller time constant with a greater absolute value of the target deceleration gradient. The controller time constant can therefore decrease as the absolute value of the target deceleration gradient increases. In other words, an inverse relationship can exist between the controller time constant and the gradient of the target deceleration or the absolute value of the gradient of the target deceleration. The dependency proposed here enables the brake control to react particularly quickly to faster changes in the target deceleration, which can be particularly relevant for safety, while unnecessarily hectic reacting to slower changes in the target deceleration, which could potentially lead to uncontrolled behavior or rocking or longitudinal oscillation of the motor vehicle, can be avoided or reduced.

[0019] In a further possible embodiment of the present invention, a predetermined fixed value is used for the(s) controlled system dead time and / or for the(s) controller time constant for standard braking maneuvers. This controlled system dead time and / or controller time constant can in particular be the controlled system dead time or controller time constant mentioned elsewhere. Thus, if it is determined that the respective braking maneuver is a standard braking maneuver, no dependency or characteristic curve is used for the controlled system dead time and / or the controller time constant, but rather the respective fixed, predetermined value is used in the braking control. The braking control is then carried out using the controlled system dead time and / or controller time constant that is constant according to the respective predetermined value.The respective fixed value for the controlled system dead time and / or the controller time constant can, for example, be specified, contained, or defined in the standard or comfort characteristic specified for standard braking maneuvers. The embodiment of the present invention proposed here can enable particularly simple implementation and execution of the brake control for standard braking maneuvers. Since such standard braking maneuvers are typically less safety-critical than emergency braking maneuvers—for example, due to lower target decelerations and lower target deceleration gradients—a comfortable and safe stopping or braking of the motor vehicle during a standard braking maneuver can also be achieved with a fixed value for the controlled system dead time and / or the controller time constant, according to a finding underlying the present invention.

[0020] The present invention also relates to a control device for a motor vehicle for automatically controlling a braking device of the respective motor vehicle. The control device according to the invention is designed to carry out the method according to the invention. The control device according to the invention can be designed, for example, as a control unit, as a control circuit, as a controller implemented in software and / or hardware, or the like. The control device according to the invention can, for example, be or comprise an electronic circuit which implements or maps the method steps, sequences, or processes described in connection with the method according to the invention. Likewise, the control device according to the invention can, for example, comprise a processor device, for example a microchip, microcontroller, microprocessor, or the like, and a data memory.An operating or computer program executable by the processor device for executing or applying the corresponding method can then be stored in this data memory, which program encodes or implements at least some of the method steps, sequences, or processes described in connection with the method according to the invention. The control device according to the invention can, in particular, be the control device or controlled system mentioned in connection with the method according to the invention or correspond to it.

[0021] The present invention also relates to a motor vehicle having an automatically actuated braking device or braking system and a control device according to the invention coupled thereto. The motor vehicle according to the invention can, in particular, be the motor vehicle mentioned in connection with the method according to the invention and / or in connection with the control device according to the invention or correspond to it. Accordingly, the motor vehicle according to the invention can have some or all of the properties or features mentioned in these contexts, such as the CVM longitudinal controller, the AEB function, and / or the like.

[0022] Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned in the description, as well as the features and combinations of features shown subsequently in the description of the figures and / or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0023] The drawing shows:

[0024] Fig. 1 is a partial schematic representation of a motor vehicle equipped with a control device for automatic brake control with different control characteristics; and

[0025] Fig. 2 shows an exemplary schematic flow chart for a method for a corresponding brake control.

[0026] Existing vehicles and vehicle assistance systems may already have implemented, for example, longitudinal vehicle control as well as a frontal protection function for automatically decelerating or stopping the vehicle when there is a risk of collision. In this case, for example, a corresponding function or assistance device can determine and output or specify a deceleration suitable or to be applied to avoid or mitigate a collision in the event of an impending frontal collision. A corresponding controller can then convert or transfer this deceleration into a suitable, i.e. corresponding, braking torque in order to compensate for any disturbances or interference as quickly as possible. To date, however, brake control has typically not differentiated between different situations or requirements; instead, a uniform control characteristic has been used. It has been shown that this can improve the follow-up behavior of the brake control for safety-critical braking orEmergency braking is not always good enough to actually avoid a collision that could have been avoided in principle, or to mitigate it with maximum effectiveness and safety. Furthermore, it may not achieve optimal comfort during standard braking maneuvers that are not or less safety-critical.

[0027] These problems can have several causes, such as a lack of differentiation between a standard or comfort characteristic for standard braking maneuvers and a safety characteristic for emergency braking maneuvers. Furthermore, a control system dead time designed for comfort may be too long for emergency braking maneuvers or safety-critical situations, so that control deviations from maximum safety may be detected too late. Likewise, relatively high values ​​of a controller's time constant can lead to longitudinal oscillation of the vehicle, especially at relatively low braking torques and relatively low vehicle speeds.

[0028] These problems can be countered by appropriately adapted brake control. For this purpose, Fig. 1 shows a partial schematic representation of a motor vehicle 1 with a braking device 2. This braking device 2 can, for example, comprise a brake disc and brake pads that can be brought into contact with it for braking. Likewise, the braking device 2 can, for example, comprise a sensor for determining or measuring a currently applied braking torque. The motor vehicle 1 also has at least one brake actuator 3, for example as part of the braking device 2 or coupled thereto. The at least one brake actuator 3 can be automatically controlled or regulated in order to actuate and release the braking device 2 in a correspondingly controlled manner. The motor vehicle 1 also has an environmental sensor system 4 and an assistance system 5 for supporting or at least partially automatically carrying out a longitudinal control of the motor vehicle 1.

[0029] In addition, the motor vehicle 1 is equipped with a control device 6. This control device 6 is designed for automatic brake control, i.e., for the controlled activation of the brake actuator 3. For this purpose, the control device 6 comprises, for example, an interface 7, a processor 8, and a data memory 9. Via the interface 7, for example, a deceleration to be set determined or requested by the assistance system 5, a current braking torque, an indication as to whether a braking maneuver to be performed is to be classified or performed as a comfort or standard braking maneuver or as a safety or emergency braking maneuver, and / or the like can be recorded.

[0030] At least one control system or control logic can be implemented in the control device 6, which is indicated here as an example and in part. A respective actual braking torque 10 can be detected therein and used as an input variable. A safety trigger 11 and the respectively requested target deceleration 12 can serve as further input variables. The safety trigger 11 can indicate or be activated if the braking maneuver to be executed is an emergency braking maneuver, i.e., a braking maneuver to be executed with a corresponding safety control characteristic. Furthermore, the control system can comprise a plurality of predetermined characteristic curve modules 13, combination or calculation modules 14 and / or the like. This then makes it possible, for example, to determine at least one control parameter 15, such as a controller dead time and / or a controller time constant, which can then be used for braking control.The characteristic curve modules 13 can, for example, specify or implement predetermined characteristic curves for a dependency of the controller time constant on the target deceleration 12 and on the gradient of the target deceleration 12 as well as a dependency of the controlled system dead time on the measured actual braking torque 10 and / or the like.

[0031] The control device 6 can implement both a comfort or standard control characteristic for standard braking maneuvers and a safety or emergency braking control characteristic for emergency braking maneuvers, which can be differently data-based, for example with regard to the controller time constant and the control system dead time.

[0032] For further illustration, Fig. 2 shows an exemplary schematic flow chart for a corresponding method for automatic brake control of the motor vehicle 1. In a method step S1, the motor vehicle 1 can be put into operation and, for example, a condition monitoring system, for example for continuous or regular monitoring or measurement of the actual braking torque 10, can be activated.

[0033] During operation of the motor vehicle 1, the assistance system 5 can then provide a braking maneuver and determine the corresponding target deceleration 12.

[0034] In a method step S2, this target deceleration 12 can be detected by the control device 6.

[0035] In a method step S3a, it can be determined or detected, for example by the assistance system 5 or the control device 6, whether the respective braking maneuver should be executed as a standard braking maneuver, i.e., with comfort or standard control characteristics, or as an emergency braking maneuver, i.e., with safety or emergency braking characteristics. In a method step S3b, the control device 6 can determine a corresponding braking torque based on the detected target deceleration 12.

[0036] In a method step S4, the control device 6 can select or set the control characteristic to be used for the respective braking maneuver. In a method step S5, the control device 6 can actuate or control the braking device 2 or the brake actuator 3 to carry out the respective braking maneuver according to the selected or set control characteristic until the braking maneuver is completed. The braking maneuver can be completed, for example, when the motor vehicle 1 is stopped, i.e., its speed is reduced to zero, when the assistance system 5 signals the end of the braking maneuver, or the like.

[0037] Overall, the examples described demonstrate how CVM longitudinal control of a vehicle can be implemented with safety characteristics when limitations are present.

[0038] 1 motor vehicle

[0039] 2 braking device

[0040] 3 Brake actuator

[0041] 4 Environmental sensors

[0042] 5 Assistance system

[0043] 6 Control device

[0044] 7 Interface

[0045] 8 processor

[0046] 9 Data storage

[0047] 10 Actual braking torque

[0048] 11 Safety triggers

[0049] 12 Target deceleration

[0050] 13 Characteristic curve module

[0051] 14 Calculation module

[0052] 15 control parameters

[0053] 16 Schedule

[0054] S1-S5 process steps

Claims

Patent claims 1. Method (16) for an automatic brake control of a motor vehicle (1), wherein each - to determine whether a braking maneuver to be performed is a standard braking maneuver within specified safety limits or an emergency braking maneuver, - if it is an emergency braking maneuver, a control characteristic specified only for this purpose, which differs from a standard control characteristic specified only for standard braking maneuvers, is used to control the actuation of a braking device of the motor vehicle (1) to carry out the braking maneuver.

2. Method (16) according to claim 1 , characterized in that the control characteristic specified for emergency braking maneuvers determines a dependence (13) of the control section dead time on the braking torque (10).

3. Method (16) according to claim 2, characterized in that the dependency (13) provides for a lower control loop dead time with a larger absolute braking torque (10).

4. Method (16) according to one of the preceding claims, characterized in that the control characteristic specified for emergency braking maneuvers determines a dependence (13) of a controller time constant on a respective target deceleration (12).

5. Method (16) according to claim 4, characterized in that the dependency (13) provides for a lower controller time constant with a larger target delay (12) in magnitude. Method (16) according to any one of the preceding claims, characterized in that the control characteristic specified for emergency braking maneuvers determines a dependency (13) of a controller time constant on the gradient of a respective target deceleration (12). Method (16) according to claim 6, characterized in that the dependency (13) provides for a lower controller time constant when the gradient of the target deceleration (12) is larger in magnitude. Method (16) according to any one of the preceding claims, characterized in that a predetermined fixed value for a control loop dead time and / or a controller time constant is used for standard braking maneuvers. Control device (6) for a motor vehicle (1) for automatically controlling a braking device (2, 3), wherein the control device (6) is configured to execute a method (16) according to any one of the preceding claims.Motor vehicle (1) comprising an automatically actuated braking device (2, 3) and a control device (6) coupled thereto according to claim 9.

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