Method for operating a vehicle

Abstract

The invention relates to a method for operating a vehicle (1), wherein the vehicle (1) has a respective electric machine (EVA, EHA) on a front axle (VA) and on a rear axle (HA), wherein the respective electric machine (EVA, EHA) can be operated in a motor mode to drive wheels (RVA, RHA) of the axle (VA, HA) on which it is arranged, and, as a constituent part of a regenerative brake, can be operated in a generator mode for regenerative braking of the wheels (RVA, RHA) of the axle (VA, HA) on which it is arranged, and wherein the vehicle (1) has a friction brake system for braking the wheels (RVA, RHA). For this purpose, an axle force which can be applied to the respective axle (VA, HA) is determined as a force vector which consists of a positive or negative drive torque of the respective axle (VA, HA), a braking torque of the respective axle (VA, HA) that is generated by the friction brake system, and a transverse acceleration at the respective axle (VA, HA), wherein a torque distribution of a requested positive or negative total drive torque to the two axles (VA, HA) is carried out depending on the determined axle force which can be applied to the respective axle (VA, HA). According to the invention, a longitudinal force on the respective axle (VA, HA) that results from the positive or negative drive torque and the braking torque is determined by means of a wheel radius of the wheels (RVA, RHA) of the respective axle (VA, HA).

Description

[0001] 2024P01747WQ

[0002] 1

[0003] Mercedes-Benz Group AG

[0004] Procedures for operating a vehicle

[0005] The invention relates to a method for operating a vehicle according to the features of the preamble of claim 1.

[0006] As described in DE 102010 014 971 A1, a method for operating a motor vehicle with two electric drives is known from the prior art. A partial torque is assigned to each drive from a requested total torque, taking into account energy efficiency on the one hand and vehicle stability on the other. A first control unit is responsible for considering energy efficiency and specifies a range of possible partial torques for a single drive. This range is limited by a second control unit if required for driving stability. The second control unit is coupled to a yaw rate sensor, a lateral acceleration sensor, and a longitudinal acceleration sensor and is aware of the steering angle.As part of an exchange of data signals with the first control unit, the partial torques are determined with the participation of the second control unit, for which the first control unit issues control commands.

[0007] German patent application DE 10 2012 112 418 A1 describes a method for distributing a desired torque to one or two drive axles of a vehicle. The desired torque depends on a driver request. For the first drive axle, a first maximum torque value is calculated, dependent on the traction limit of the first drive axle. For the second drive axle, a second maximum torque value is calculated, also dependent on the traction limit of the second drive axle. A first portion of the desired torque, which does not exceed the first maximum value, is transferred to the first drive axle. A second portion of the desired torque, which does not exceed the second maximum value, is transferred to the second drive axle if the first portion does not correspond to the desired torque. The distribution of the desired torque between the first and second portions depends on a parameter.

[0008] From DE 102004 053 880 A1, a method for determining the maximum coefficient of friction between vehicle tires and the road surface is known. The maximum coefficient of friction is determined by determining the instantaneous slip and the instantaneous coefficient of friction and, in a plot of instantaneous coefficient of friction against instantaneous slip, intersecting a straight line through the origin and the point thus determined with a straight line parallel to the ordinate.

[0009] German patent DE 10 2012 217 772 A1 describes a method for determining the maximum coefficient of friction between a vehicle tire and a road surface. A tuple of values ​​comprising an instantaneous coefficient of friction and an instantaneous slip, and / or an instantaneous coefficient of friction and an instantaneous slip angle, is determined. Using this determined tuple of values ​​and a zero-point tuple, the slope of a straight line passing through the origin and the two tuples of values ​​is calculated. The maximum coefficient of friction is then determined based on this value and / or based on the position of the determined tuple of values ​​within two predetermined regions, defined by predefined values ​​of the quantities in the determined tuple of values.

[0010] German patent DE 102022 004615 A1 discloses a method for operating a regenerative braking system of a vehicle that has an electric motor on each axle for propulsion and regenerative braking. A maximum total regenerative braking torque is specified for the regenerative braking system, which must not be exceeded during regenerative braking. A maximum axle-specific regenerative braking torque is specified for each axle, which must not be exceeded during regenerative braking.During ferry operation of the vehicle, it is provided that if a driving situation occurs with slippage on at least one of the axles, depending on a value of a maximum torque transmitted to a road surface by this axle during this driving situation, the respective maximum axle recuperation braking torque of both axles is redefined, and that during engine operation of the respective axle, a current value of 2024P01747WQ is used.

[0011] 3. The drive torque transmitted to the road surface for each axle is used to calculate a value for the maximum axle recuperation braking torque for both axles, and if the calculated value is greater than the currently specified maximum axle recuperation braking torque, the specification of the maximum axle recuperation braking torque is increased to the calculated value.

[0012] The generic document DE 102016214 925 A1 discloses a method for operating a motor vehicle with two drive wheels on one axle, wherein each drive wheel can be driven by an individual drive unit. The drive units of an axle are controlled as a function of the difference between the longitudinal forces transmitted to the road surface at the drive wheels of the axle.

[0013] The invention is based on the objective of providing a method for operating a vehicle that is improved compared to the prior art.

[0014] The problem is solved according to the invention by a method for operating a vehicle with the features of claim 1.

[0015] Advantageous embodiments of the invention are the subject of the dependent claims.

[0016] A vehicle has an electric motor on each of its front and rear axles. Each electric motor can be operated in motor mode to drive the wheels of the axle on which it is located, and as part of a regenerative braking system, it can be operated in generator mode to recuperate braking energy for the wheels of the axle on which it is located. The vehicle also has a friction braking system, in particular a hydraulic system, for braking the wheels. The friction braking system includes, in particular, a wheel brake on each wheel, for example, a disc brake or drum brake.

[0017] In a method according to the invention for operating the vehicle, in particular in an ongoing ferry operation of the vehicle, a deployable axle force of the respective axle is determined as a force vector, which consists of a positive or negative drive torque of the respective axle, a braking torque of the respective axle generated by the friction brake system and a lateral acceleration at the respective 2024P01747WQ

[0018] 4

[0019] The axle consists of these physical quantities. The negative drive torque is also referred to as recuperation torque.

[0020] According to the invention, a longitudinal force resulting from the positive or negative drive torque and the braking torque is determined at the respective axle using the wheel radius of the wheels of that axle, particularly for use in the force vector. The longitudinal force is, in particular, a force in the direction of a longitudinal axis of the vehicle. The wheel radius of the wheels of the respective axle is, for example, predetermined or is determined from a calculated or predetermined rolling circumference of the wheels of the respective axle.

[0021] It is specifically intended that a torque distribution of a positive or negative total drive torque, requested, for example, by a driver and / or a driver assistance system, is carried out between the two axles depending on the determined available axle load of the respective axle. The driver assistance system is, for example, an adaptive cruise control system or a system for carrying out automated, especially highly automated, or autonomous ferry operation.

[0022] The permissible axle load is determined continuously, especially continuously during ferry operation of the vehicle.

[0023] Advantageously, the lateral acceleration at the respective axle, particularly for use in the force vector, is converted into a lateral force at the respective axle. The lateral force is, in particular, a force acting in the direction of a transverse axis of the vehicle. The lateral acceleration at the respective axle is converted into the lateral force at the respective axle, in particular by means of a predetermined unladen weight of the vehicle and a predetermined static weight distribution on the front and rear axles. The unladen weight of the vehicle, in particular without optional equipment but including a predetermined driver weight of, for example, 75 kg and a predetermined fuel tank weight, is known, i.e., predetermined, and is stored, for example, in the vehicle's software, in particular in a control unit designed and configured to carry out the method. The static weight distribution on the front axle and 2024P01747WQ

[0024] 5

[0025] The rear axle is also advantageously predetermined or known. It is, or is set, for example, by means of one or more parameters.

[0026] Taking lateral acceleration, and thus the lateral force at each axle, into account is particularly advantageous because the positive or negative drive torque (i.e., recuperation torque) that can be applied to each axle changes depending on the driving situation. If the lateral acceleration increases while cornering, the potential for positive or negative drive force (i.e., longitudinal force) that can be applied to the respective axle decreases. Conversely, if the lateral acceleration is reduced, the potential for positive or negative drive force (i.e., longitudinal force) that can be applied to the respective axle increases.

[0027] The described method, in particular the described calculation method for determining the forces that can be applied to the axles and thus the wheel forces, advantageously enables a continuous calculation of the possible forces that can be applied to each driven axle. The method is also applicable regardless of whether the vehicle is an all-wheel drive vehicle or a two-wheel drive vehicle, or whether the vehicle is an all-wheel drive vehicle where it is possible to drive only one axle or both axles.

[0028] In the described solution, the lateral forces on the axles and, advantageously, slippage are also taken into account when determining the applicable axle force for each axle, particularly on a continuous basis. This solution allows for improved and more variable control of an electric drive comprising the two electric machines, also known as an electric drive train. The described solution not only allows for better adjustment of drive forces and / or drive torques and recuperation forces and torques, but also enables more dynamic control and redistribution of the torque distribution between the two axles.For this purpose, in particular a current driving situation in the currently carried out ferry operation and a possible transferable axle force of the respective axle, in particular in the form of current wheel forces of the wheels of the respective axle, in particular a sum of these wheel forces of the respective axle, also taking into account lateral forces and in particular also slip, is determined and taken into account in a drive strategy for controlling the electric drive train, in particular the two electric machines, in order to adjust the torque distribution accordingly.

[0029] From a vehicle dynamics perspective, the described solution enables variable torque distribution during drive and recuperation operation, i.e., in positive and negative drive modes. Advantageously, the torque distribution adapts to the prevailing road conditions, particularly the coefficient of friction, as well as the vehicle dynamics. Specifically, it is designed that torque redistribution to the other axle only occurs when the determined values ​​are exceeded, especially the determined maximum permissible axle force on the respective axle.

[0030] On a high-friction road surface, this means, for example, that an efficient distribution of positive and negative drive torques to the axles, and thus to the wheels, can always be achieved. This is because the determined values, i.e., in particular the determined transferable axle force at each axle, either remain at a predetermined initial value, i.e., reach it, so that no restriction of the positive and negative drive torques per axle is necessary, or are so large that they do not lead to a redistribution of the drive torques. Therefore, from a vehicle dynamics perspective, there is no reason for torque redistribution, and the most efficient torque distribution can always be implemented.

[0031] On a low-friction road surface, however, this means that, from a driving dynamics perspective, all-wheel drive torque distribution is requested as soon as the determined values, i.e., in particular the determined axle load at each axle, are exceeded. This ensures a stable driving condition early on, as all-wheel drive is requested, which advantageously prevents these values ​​from being exceeded. This prevents a single driven axle from being subjected to the entire drive torque. The drive force is distributed to both axles, taking into account the determined values, i.e., in particular the determined axle load at each axle. In total, this allows for higher positive and negative drive torques to be applied than would be possible in single-axle operation, i.e., when drive torque is applied to only one axle.If the total required drive torque exceeds the sum of the determined values ​​per axle, i.e., in particular the sum of the determined applicable axle forces on the axles, the total drive torque is advantageously distributed between the two driven axles using a 50:50 distribution in the case of recuperation and a 33:67 distribution in the case of driven operation, particularly until a technically permissible maximum torque per axle is reached. Thereafter, the drive torque is advantageously increased only on the axle that still has available torque capacity.

[0032] The described solution does not reduce the torque, but merely distributes the requested total drive torque between the two driven axles or changes this torque distribution.

[0033] In particular, due to the described relationships, one embodiment provides that if the permissible axle force of one of the two axes would be exceeded by applying a positive or negative drive torque, the remaining portion of the positive or negative drive torque that cannot be applied to this axle is applied to the other axle.

[0034] In particular, due to the described relationships, one embodiment provides that if the total positive or negative drive torque required for placement via the two axes exceeds the sum of the positive or negative drive torques that can be placed on the axes according to the determined placeable axle force of the respective axle, both axes are first subjected to a positive or negative drive torque equally until the placeable axle force determined for the respective axle is reached on one of the two axes, and then the positive or negative drive torque on the other axle is further increased, in particular until the placeable axle force determined for this axle is also reached there, if this occurs.

[0035] The calculation of maximum drive force also takes place in vehicles with only one driven axle, but of course, only for that axle. By continuously calculating the torque, even in vehicles with only one driven axle, the switching and transmission of the available torque to the electric motor can be managed, thus enabling this to be implemented for the single driven axle. A torque distribution between the front and rear axles is irrelevant in this case, as there is only one driven axle in the vehicle. Therefore, torque distribution between the front and rear axles remains the domain of vehicles with two driven axles, such as all-wheel drive (AWD) or 4WD vehicles.

[0036] In one embodiment, the electric machine of each axle is coupled to the wheels of that axle via a transmission, for example a two-speed transmission, during both driving and regenerative braking. It is particularly provided that such a transmission is arranged on each axle; that is, a transmission is arranged on the front axle through which the electric machine located on the front axle is connected to the wheels of the front axle during both driving and regenerative braking, and a transmission is arranged on the rear axle through which the electric machine located on the rear axle is connected to the wheels of the rear axle during both driving and regenerative braking.

[0037] The described solution allows downshifting operations due to high desired torque requirements, i.e., due to high requested, especially positive, total drive torques, to be actively avoided if the determined values, i.e., in particular the determined deployable axle force at the respective axle, indicate that a maximum possible drive torque of the currently engaged higher gear, for example 2nd gear, is sufficient for the prevailing road and, in particular, friction coefficient conditions.

[0038] If the determined values, i.e., in particular the determined deployable axle force on the respective axle, indicate that the desired torque, i.e., the requested, in particular positive, total drive torque, cannot be provided by the currently engaged high gear, for example 2nd gear, the downshifting process can be enabled and the best possible gear for acceleration is selected.

[0039] In particular, due to the relationships described, it is therefore specifically intended that downshifting to a lower gear is prevented if the maximum possible drive torque of the currently engaged gear is sufficient to achieve the determined applicable axle force of the respective axle and / or if a maximum possible drive torque of the lower gear is greater than the determined applicable axle force of the respective axle.

[0040] The gears are also referred to as gear stages or transmission stages. As mentioned above, each transmission has, for example, two gears.

[0041] For example, it is intended that the axle force determined for the respective axle and / or the resulting positive and negative drive torque of the electric machine of the respective axle is provided directly, in particular by the control unit, for example via a CAN bus or another data transmission connection, thereby enabling its consideration in the control of the electric machine.

[0042] As soon as the drive torques provided by the control unit are exceeded by the respective electric motor, the electric motor can, for example, proactively activate speed control for wheel slip control. This allows for early intervention in case of impending wheel failure, i.e., an imminent loss of traction of the respective wheel to the road surface, since target speeds provided by a vehicle dynamics control system, such as ESP (Electronic Stability Program), do not need to be exceeded before a speed controller of the electric drivetrain is activated.

[0043] Additionally, once the torque thresholds are exceeded—that is, the drive torques resulting from the determined applicable axle force—a torque build-up gradient can be limited to smoothly approach physical slip thresholds. This prevents physical latencies, such as those caused by drivetrain overrun, from occurring in the first place, as the speed controller already knows that the slip thresholds will soon be exceeded.

[0044] In particular, due to the described relationships, in one embodiment the respective electric machine activates a speed control for wheel slip control when the determined permissible axle force of this axle is exceeded by applying a positive or negative drive torque to the axle of this electric machine. In another embodiment, once the determined permissible axle force of the respective axle is exceeded, the torque build-up gradient on this axle is limited to a predetermined gradient value.

[0045] Exemplary embodiments of the invention are explained in more detail below with reference to a drawing.

[0046] This shows:

[0047] Fig. 1 schematically shows a vehicle.

[0048] Figure 1 shows a schematic representation of a vehicle 1 with a front axle VA and a rear axle HA. An electric machine EVA, EHA is arranged on each of the front axles VA and HA. The wheels RVA, RHA of the respective axles VA and HA can be driven by the respective electric machine EVA, EHA in motor mode and can be braked recuperatively in generator mode. Furthermore, the wheels RVA, RHA can also be braked by means of a friction braking system of the vehicle 1, in particular a hydraulic system.

[0049] The vehicle 1 further comprises a control unit 2, which is specifically designed and equipped to control the electric machines EVA, EHA, in particular with regard to carrying out the motor operation for driving the vehicle 1 and the generator operation for recuperating braking of the vehicle 1. For example, the control unit 2 is also designed and equipped to control the friction brake system.

[0050] The control unit 2 is specifically designed and configured to carry out a procedure for operating the vehicle 1 described below. For this purpose, the control unit 2 is, in addition to the two electric machines EVA, EHA and advantageously the friction brake system, also coupled to other components of the vehicle 1, for example, to control units of a traction control system and / or a vehicle dynamics control system and / or an anti-lock braking system and / or a steering system, and / or to sensors of the vehicle 1.

[0051] 11 in particular with sensors used by the traction control system and / or the vehicle dynamics control system and / or the anti-lock braking system and / or the steering system.

[0052] The procedure for operating vehicle 1 provides in particular that, especially in a currently carried out ferry operation of vehicle 1, a deployable axle force of the respective axle VA, HA is determined as a force vector, which consists of a positive or negative drive torque of the respective axle VA, HA, a braking torque generated by the friction brake system of the respective axle VA, HA and a lateral acceleration at the respective axle VA, HA.

[0053] The deployable axle force is determined in particular continuously, especially continuously during ferry operation of vehicle 1.

[0054] It is specifically intended that a moment distribution of a requested positive or negative total drive torque on the two axles VA, HA is carried out depending on the determined deployable axle force of the respective axle VA, HA.

[0055] It is specifically intended that a longitudinal force resulting from the positive or negative drive torque and the braking torque at the respective axle VA, HA is determined by means of the wheel radius of the wheels RVA, RHA of the respective axle VA, HA. The wheel radius of the wheels RVA, RHA of the respective axle VA, HA is, for example, predefined or is determined from a determined or predefined rolling circumference of the wheels RVA, RHA of the respective axle VA, HA.

[0056] It is specifically provided that the lateral acceleration at the respective front axle (VA) and rear axle (HA) is converted into a lateral force at the respective axle (VA) and rear axle (HA), in particular by means of a predetermined unladen weight of the vehicle 1 and by means of a predetermined static weight distribution on the front axle (VA) and the rear axle (HA). The unladen weight of the vehicle 1, in particular without optional equipment but including a predetermined driver weight of, for example, 75 kg and a predetermined fuel tank weight, is known, i.e., predetermined, and is stored, for example, in software of the vehicle 1, in particular in the control unit 2. The static weight distribution on the front axle (VA) and rear axle (HA) is advantageously also predetermined or known. It is or is set, for example, by means of one or more parameters. 2024P01747WQ

[0057] 12

[0058] Considering lateral acceleration and thus the lateral force at each axle (front axle, rear axle) is particularly advantageous because the positive or negative drive torque that can be applied to each axle changes depending on the driving situation. If the lateral acceleration increases during cornering, the potential for positive or negative drive force (i.e., longitudinal force) that can be applied to each axle decreases. Conversely, if the lateral acceleration is reduced, the potential for positive or negative drive force (i.e., longitudinal force) that can be applied to each axle increases.

[0059] From a vehicle dynamics perspective, the described solution enables variable torque distribution during drive and recuperation operation, i.e., in positive and negative drive modes. The torque distribution advantageously adapts to the prevailing road conditions, particularly the coefficient of friction, as well as the vehicle dynamics. Specifically, it is designed that a torque redistribution to the other axle (front or rear) is only implemented if the determined values ​​are exceeded, i.e., in particular, the determined transferable axle force at the respective front or rear axle.

[0060] On a high-friction road surface, this means, for example, that an efficient distribution of positive and negative drive torques to the front and rear axles, and thus to the front and rear wheels, can always be achieved. This is because the determined values, i.e., in particular the determined transferable axle force at each front and rear axle, either remain at a predetermined initial value, i.e., reach it, so that no restriction of the positive and negative drive torques per axle is necessary, or are so large that they do not lead to a redistribution of the drive torques. Therefore, from a vehicle dynamics perspective, there is no reason for torque redistribution, and the most efficient torque distribution can always be implemented.

[0061] On a low-friction road surface, however, this means that, from a driving dynamics perspective, all-wheel drive torque distribution is requested as soon as the determined values, i.e., in particular the determined available axle load at each axle (front and rear axle), are exceeded. This ensures a stable driving condition early on, as all-wheel drive is requested, which advantageously prevents these values ​​from being exceeded. This prevents a single driven axle (front or rear axle) from being subjected to the entire drive torque. The drive force is distributed to both axles (front and rear axle) taking into account the determined values, i.e., in particular the determined available axle load at each axle (front and rear axle). In total, this allows for higher positive and negative drive torques to be applied than would be possible in single-axle operation, i.e., when drive torque is applied to only one axle (front or rear axle).If the total required drive torque exceeds the sum of the determined values ​​per axle (front axle, rear axle), i.e., in particular the sum of the determined available axle forces on the front axle (front axle, rear axle), the total drive torque is advantageously distributed between the two driven axles (front axle, rear axle) using a 50:50 distribution in the case of recuperation and a 33:67 distribution in the case of driven operation, in particular until a technically permissible maximum torque per axle (front axle, rear axle) is reached. Thereafter, the drive torque is advantageously increased only on the axle (front axle, rear axle) that still has available torque capacity.

[0062] The described solution does not reduce the torque, but merely distributes the requested total drive torque between the two driven axles VA and HA, or changes this torque distribution.

[0063] In particular, due to the described relationships, one embodiment provides that if the transferable axle force of one of the two axes VA, HA would be exceeded by applying a positive or negative drive torque, the remaining portion of the positive or negative drive torque that cannot be transferred to this axle VA, HA is applied to the other axle VA, HA.

[0064] Particularly due to the described relationships, one embodiment provides that if the total positive or negative drive torque required for lowering via the two axles VA, HA exceeds the sum of the positive or negative drive torques that can be lowered on the axles VA, HA according to the determined lowering axle force of the respective axle VA, HA, both axles VA, HA are initially supplied with a positive or negative drive torque evenly until the lowering axle force determined for the respective axle VA, HA is reached on one of the two axles VA, HA, and then the positive or negative drive torque on the other axle HA, VA is further increased, in particular until the lowering axle force determined for this axle VA, HA is also reached there, if this occurs.

[0065] In one embodiment, the electric machine EVA, EHA of the respective axle VA, HA is coupled to the wheels RVA, RHA of the respective axle VA, HA via a transmission (not shown), for example a two-speed transmission, during the driving and recuperating braking of the wheels RVA, RHA of the respective axle VA, HA.

[0066] A calculation of the maximum drive force also takes place in vehicles 1 with only one driven axle (VA, HA), naturally only for that driven axle. Through the continuous calculation of the torques, even in vehicles 1 with only one driven axle (VA, HA), the switching and transmission of the available torques to the electric motor (EVA, EHA) can be carried out, so that this can also be implemented for the single driven axle (VA, HA). A torque distribution between the front axle (VA) and rear axle (HA) is irrelevant here, since there is only one driven axle (VA, HA) in vehicle 1. Therefore, the torque distribution between the front axle (VA) and rear axle (HA) remains reserved for vehicles 1 with two driven axles (VA, HA), for example, in so-called all-wheel drive (AWD) or 4WD vehicles.

[0067] The described solution allows downshifting operations due to high desired torque requirements, i.e., due to high requested, especially positive, total drive torques, to be actively avoided if the determined values, i.e., in particular the determined deployable axle force at the respective axle VA, HA, indicate that a maximum possible drive torque of the currently engaged higher gear, for example 2nd gear, is sufficient for the prevailing road and, in particular, friction coefficient conditions.

[0068] If the determined values, i.e., in particular the determined deployable axle force at the respective axle VA, HA, indicate that the desired torque, i.e., the requested, in particular positive, total drive torque, cannot be provided by the currently engaged high gear, for example 2nd gear, the downshifting process can be enabled and the best possible gear for acceleration is selected.

[0069] In particular, due to the relationships described, it is therefore specifically intended that downshifting to a lower gear, for example to 1st gear, is prevented if the maximum possible drive torque of the currently engaged gear is sufficient to achieve the determined applicable axle force of the respective axle VA, HA and / or if a maximum possible drive torque of the lower gear, for example 1st gear, is greater than the determined applicable axle force of the respective axle VA, HA.

[0070] For example, it is intended that the applicable axle force determined for the respective axle VA, HA and / or the resulting positive and negative drive torque of the electric machine EVA, EHA of the respective axle VA, HA is provided directly, in particular by the

[0071] Control unit 2, for example via a CAN bus, which allows its consideration in the control of the electric machine EVA, EHA.

[0072] As soon as the drive torques provided by control unit 2 are exceeded by the respective electric machine EVA, EHA, the electric machine EVA, EHA can, for example, proactively activate speed control for wheel slip control. This allows for early intervention in case of impending wheel failure, since target speeds provided by a vehicle dynamics control system do not need to be exceeded before a speed controller of the electric drivetrain is activated.

[0073] Additionally, once the torque thresholds are exceeded—that is, once the drive torques resulting from the determined applicable axle force are exceeded—a torque build-up gradient can be limited to smoothly approach physical slip thresholds. This prevents physical latencies, such as those caused by the drivetrain overrun, from occurring in the first place, as the speed controller already knows that the slip thresholds will soon be exceeded. In particular, due to the relationships described, in one embodiment, the respective electric machine EVA, EHA activates speed control for wheel slip control when the determined applicable axle force of axle VA, HA is exceeded by applying a positive or negative drive torque to this electric machine EVA, EHA.

[0074] In one embodiment, once the determined permissible axial force of the respective axis VA, HA is exceeded, the moment build-up gradient on this axis VA, HA is limited to a predetermined gradient value.

[0075] Reference symbol list

[0076] 1 vehicle

[0077] 2 Control unit

[0078] EVA, EHA electric machine

[0079] Rear axle

[0080] VA front axle

[0081] RVA, RHA wheel

Claims

2024P01747WQ 18 Mercedes-Benz Group AG Patent claims 1. Method for operating a vehicle (1), wherein the vehicle (1) has an electric machine (EVA, EHA) on a front axle (VA) and on a rear axle (HA), wherein the respective electric The machine (EVA, EHA) is operable in motor mode for driving wheels (RVA, RHA) of the axle (VA, HA) on which it is arranged, and as part of a recuperative brake in generator mode for recuperating braking of the wheels (RVA, RHA) of the axle (VA, HA) on which it is arranged, and wherein the vehicle (1) has a friction brake system for braking the wheels (RVA, RHA), wherein a deployable axle force of the respective axle (VA, HA) is determined as a force vector consisting of a positive or negative drive torque of the respective axle (VA, HA), a braking torque of the respective axle (VA, HA) generated by the friction brake system, and a lateral acceleration at the respective axle (VA, HA), wherein a torque distribution of a requested positive or negative total drive torque to the two axles (VA, HA) is carried out depending on the determined deployable axle force of the respective axle (VA, HA), characterized in thatthat a longitudinal force resulting from the positive or negative drive torque and the braking torque at the respective axle (VA, HA) is determined by means of a wheel radius of the wheels (RVA, RHA) of the respective axle (VA, HA).

2. Method according to claim 1, characterized in that the deployable axle force is continuously determined. 2024P01747WQ 19 3. Method according to claim 1 or 2, characterized in that the wheel radius of the wheels (RVA, RHA) of the respective axle (VA, HA) is predetermined or is determined from a determined or predetermined rolling circumference of the wheels (RVA, RHA) of the respective axle (VA, HA).

4. Method according to one of the preceding claims, characterized in that the lateral acceleration at the respective axle (VA, HA) is controlled by means of a predetermined unladen weight of the vehicle (1) and by means of a predetermined static weight distribution on the front axle (VA) and on the The force on the rear axle (HA) is converted into a lateral force on the respective axle (VA, HA).

5. Method according to one of the preceding claims, characterized in that if the permissible axle force of one of the two axles (VA, HA) would be exceeded by applying a positive or negative drive torque, the remaining portion of the positive or negative drive torque that cannot be applied to this axle (VA, HA) is applied to the other axle (VA, HA).

6. Method according to one of the preceding claims, characterized in that when the total positive or negative drive torque required for placement via the two axles (VA, HA) exceeds the sum of the positive or negative drive torques that can be applied to the axles (VA, HA) according to the determined applicable axle force of the respective axle (VA, HA), both axles (VA, HA) are first uniformly supplied with a positive or negative drive torque until the applicable axle force determined for the respective axle (VA, HA) is reached on one of the two axles (VA, HA), and then the positive or negative drive torque on the other axle (HA, VA) is further increased.

7. Method according to one of the preceding claims, characterized in that the electric machine (EVA, EHA) of the respective axle (VA, HA) is coupled to the wheels (RVA, RHA) of the respective axle (VA, HA) via a transmission during the driving and recuperating braking of the wheels (RVA, RHA) of the respective axle (VA, HA), wherein downshifting to a lower gear is prevented if a maximum possible drive torque of a currently engaged gear is sufficient to achieve the determined deployable axle force of the respective axle (VA, HA) and / or if a maximum possible drive torque of the lower gear is greater than the determined deployable axle force of the respective axle (VA, HA).

8. Method according to one of the preceding claims, characterized in that a speed control for wheel slip control is activated by the respective electric machine (EVA, EHA) when the pressure is applied to the The determined dropable axle force of this axle (VA, HA) is exceeded when the axle (VA, HA) of this electric machine (EVA, EHA) has a positive or negative drive torque.

9. Method according to claim 8, characterized in that, from the point at which the determined permissible axial force of the respective axis (VA, HA) is exceeded, a moment build-up gradient on this axis (VA, HA) is limited to a predetermined gradient value.

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