EP4263261A1

EP4263261A1 - Method for distributing a required torque for driving a vehicle with wheels

Info

Publication number: EP4263261A1
Application number: EP21839369.2A
Authority: EP
Inventors: Dirk Patrick Hofmann-Mees; Nicolai ALBRECHT; Holger Roegl; Juergen Hoenings
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-12-17
Filing date: 2021-12-13
Publication date: 2023-10-25
Also published as: CN116635281A; DE102020216118A1; WO2022128835A1

Abstract

The invention relates to a method for distributing a required torque for driving a vehicle with wheels, in which multiple wheel sets, each having at least one wheel, can be driven independently of one another to transmit drive force to the ground, said method having the following steps: determining (300) that at least one wheel of one of the multiple wheel sets is beginning to spin; determining (320), for each of the multiple wheel sets, a limit torque (M_G,max,VA, M_G,max,HA) which corresponds to a maximum drive force which can be transmitted via the respective wheel set and at which none of the wheels in the respective wheel set spins; determining a distribution of the required torque (M_A) to the multiple wheel sets such that more than the respective limit torque (M_G,max,VA, M_G,max,HA) is not applied to any of the multiple wheel sets; and initiating implementation of the determined distribution.

Description

description

title

Method for apportioning a requested torque for propelling a wheeled vehicle

The present invention relates to a method for splitting a requested torque for driving a vehicle with wheels, as well as a computing unit and a computer program for carrying it out.

Background of the Invention

In so-called hybrid vehicles, different types of drive units can be used, e.g. combustion engines and electric motors. In the so-called P4 topology, for example, an internal combustion engine can be used as a drive unit to drive one of two axles of the vehicle, while an electric machine can be used as a drive unit to drive (or, in the case of recuperation, also to brake) the other axle. With this topology, the electric machine can be used to optimize energy consumption. For example, an operating strategy can be used in software functions to calculate how the driver's desired torque should be divided between the internal combustion engine and the electric machine. It can be assumed that in hybrid operation of the vehicle, the greater part of the required torque is provided by the internal combustion engine.

Disclosure of Invention

According to the invention, a method for splitting a required torque for driving a vehicle with wheels and a computing unit and a computer program for its implementation with the features of the independent patent claims. Advantageous configurations are the subject of the dependent claims and the following description.

The invention deals with vehicles with wheels, in which several wheel subsets, each with at least one wheel, can be driven independently of one another to transmit driving force to a surface. The independent drive is achieved by means of different prime movers, which can be prime movers of different types or multiple prime movers of the same type. For example, at least one of the multiple wheel subsets can be driven by an internal combustion engine and at least one other of the multiple wheel subsets can be driven by at least one electric machine. It is also advantageous that at least two of the plurality of wheel subsets can each be driven by means of at least one electrical machine.

In general, in the vehicle, at least one of the plurality of wheel subsets may have two wheels belonging to the same vehicle axle. Such a vehicle can be, for example, a hybrid vehicle already mentioned at the outset, for example with a P4 topology, in which case one subset of wheels comprises two wheels on one axle and another subset of wheels comprises two wheels on the other axle. Each axle can be driven directly, but the wheels can also be driven separately.

Even if the invention is described below primarily with reference to a vehicle with a P4 topology, the explanations correspondingly apply generally to vehicles as mentioned above.

In such vehicles, the invention further relates to apportioning a requested torque for driving the vehicle. As already mentioned, a torque requested by a driver—or otherwise, for example by a driver assistance system—can be divided between the multiple drivable axles or generally the multiple drivable wheel subsets. Due to the property that both axles or wheel subsets are independent of However, to be able to drive nander, such a vehicle offers additional potential that has not been used in a targeted manner, as has been shown.

On a roadway or a surface with a low coefficient of friction (or adhesion coefficient) and/or with too high drive torques, one or more wheels of a driven wheel subset (e.g. axle) can exceed the traction limit due to the effective drive torque and spin. As a result, the entire driver's request is not converted into propulsion. At the same time, the vehicle behavior becomes potentially unstable, since a spinning wheel cannot transfer any forces to the lateral stability of the vehicle. For this reason, there are systems such as traction control (ASR) or, in the event of braking, the anti-lock braking system (ABS). If the wheels were spinning, intervention by the ASR would result in the torque on the spinning wheel being reduced in order to stabilize the driving situation. In this case, however, the driver's desired torque is reduced, which means that the propulsion of the vehicle is reduced.

In the context of the present invention, it is now proposed to end the situation of a spinning wheel by purposefully distributing the requested torque to the several wheel subsets (e.g. axles) that can be driven independently of one another, but nevertheless to implement the requested torque as far as possible. It goes without saying that such a division of the requested torque also includes an adjustment or modification of an already existing division.

To this end, the following steps are carried out, for example by an executing computing unit such as an engine or drive control unit. It is determined that at least one wheel of one of the plurality of wheel subsets is beginning to spin or is already spinning. There are various preferred options for this, which will be explained in more detail later. Furthermore, a limit torque is determined for each of the several wheel subsets, which corresponds to a maximum drive force that can be transmitted via the respective wheel subset, at which no wheel of the respective wheel subset spins. Based on this, the requested torque is then divided among the several wheel subsets determined in such a way that none of the multiple wheel subsets is more than the respective limit torque. The split of the requested torque determined in this way is then implemented or caused to be implemented. This can be done, for example, by appropriate control signals to the drive units and/or a gear.

In this way, a state of a spinning wheel is advantageously eliminated, but the requested torque is nevertheless implemented as far as possible, namely by reducing the torque for the subset of wheels in which the wheel is spinning, but increasing it for another subset of wheels . Determining the distribution of the requested torque over the multiple wheel subsets therefore preferably includes reducing a torque assigned to the wheel subset with the spinning wheel by a differential torque at least up to the limit torque of this wheel subset, and increasing a torque assigned to at least one of the other wheel subsets by the Differential torque, but preferably per wheel subset at most up to the respective limit torque. This also includes the case where only one subset of wheels (the one with the spinning wheel) was previously assigned a torque, but not others.

At this point it should also be noted that the splitting of the requested torque in such a way that the limit torque is not exceeded at any of the wheel subsets reliably eliminates the state of spinning wheels. Under certain circumstances, this can mean that the full, requested torque cannot actually be implemented; however, this case is limited as far as possible.

The respective limit torque is determined in particular on the basis of an effective normal force on the respective wheel subset (e.g. axle), a dynamic wheel radius and a coefficient of adhesion between the wheels and the ground or roadway, which is determined at a point in time before, in particular immediately before, the spin or the incipient spinning of the at least one wheel is present, determined. The coefficient of adhesion is preferably based on the at this point in time (i.e. the point in time before the detection of the Spin) determined via the respective subset of wheels maximum transferrable drive force and the effective normal force on the respective subset of wheels. The dynamic wheel radius (or wheel radius) corresponds to an effective radius of the wheel during driving. This is obtained by rolling a wheel once completely (360° rotation) on the road and measuring the distance covered. This distance corresponds to the rolling circumference. This allows the dynamic wheel radius to be calculated by dividing the rolling circumference by two Pi (the background here is that the wheel radius is not the same everywhere due to the load on the wheel).

The underlying idea here is that the driving force that can be transferred to the road via a wheel or a subset of wheels is determined by the coefficient of adhesion and the normal force currently acting on the wheel or subset of wheels, i.e. the force acting perpendicularly to the road. The current or effective normal force results from the weight of the vehicle, proportionately for the wheel subset in question, and possibly a current incline of the roadway or a moment on the wheels, which results from an acceleration of the vehicle that affects the center of gravity of the vehicle acts and thus causes the vehicle to tilt (be it longitudinally or laterally). With the coefficient of adhesion, it must be ensured that the value used applies at a point in time when the straight wheel is not (yet) spinning. Then it can be assumed that the coefficient of adhesion for the current combination of wheel and road surface is at its maximum. For a more detailed explanation of this, reference is also made to the description of the figures, in particular the depiction of the adhesion coefficient as a function of the slip.

It should also be taken into account here that in this way a coefficient of adhesion is required from a point in time which lies before the point in time at which the wheel spins or begins to spin and the adaptation of the distribution of the requested torque takes place. A dead time element can be used for this purpose, with which the coefficient of adhesion is passed on with a delay or which delays the force/torque values used to calculate the coefficient of adhesion. The goal is to use the to use values that were present at a point in time (t-dead time). This is intended to ensure that the point in time immediately before the traction limit is exceeded is reflected in the calculation of the coefficient of friction. The point in time can be a definable time (eg between 0 and 1000 ms, but in practice this usually depends on the type of detection; a fixed time or threshold or a speed-dependent time can be used) before the spin is detected lie. It goes without saying that in general there can be a delay in the transmission or even a temporary storage of the coefficient of adhesion.

The determination of the distribution of the requested torque over the plurality of wheel subsets is preferably carried out repeatedly or continuously according to one of the following criteria. The split may be determined so long as it is determined (or determined) that at least one wheel is spinning. However, the division can also be determined for a predetermined period of time from the first determination that at least one wheel is spinning. A combination is also conceivable, such that the division is determined as long as it is determined (or ascertained) that at least one wheel is spinning and then continues for a predetermined period of time. The criterion to be used can, for example, be defined for a certain type of vehicle, but it is also conceivable that it could be adjusted or selected depending on the situation, so that a flexible and optimal reaction can be made.

The predetermined period of time can be specified in particular according to one of the following criteria.

- as a fixed value,

- depending on a wheel speed of the wheel subset at which the wheel spins or starts to spin (in the case of a wheel subset with only one wheel, the wheel speed corresponds to the speed of the wheel, in the case of several wheels in a wheel subset, e.g. the mean value such as the arithmetic mean, conceivable is e.g. also the maximum of the wheel speeds of this wheel subset),

- depending on the limit torque of the partial wheel quantity at which the wheel spins, or - Depending on a history of adjustments made to the current distribution (for example, it can be provided that the distribution is adjusted the longer the more interventions were made in a specific period of the past).

This period of time can also be specified for a specific vehicle type, for example, but it is also conceivable that it could be adjusted or selected depending on the situation, so that the response can be flexible and as optimal as possible. Ultimately, it can be achieved that a state of spinning wheels is not immediately reached again.

It should also be noted that in the solution described here, too, the torque that is allocated to the wheel subsets or axles for conversion can be or can be additionally limited by an ASR system if an existing ASR system is required and available. In such a constellation, the limitation by the ASR system would be active, for example, until the wheel or wheels no longer spin. It is then also conceivable that as part of the torque limitation by the ASR system, the proposed adjustment of the distribution is suspended and meanwhile, for example, another type of redistribution of the torque to the wheel subsets or axles takes place, for example to further stabilize the driving situation. After a certain time, you can then, for example, return to the proposed solution.

The function improves the overall propulsion of the vehicle and at the same time reduces the need for stabilizing interventions (e.g. by the ASR). Since the intervention reacts as required to the situation of spinning wheels and at the level of the necessary torque limitation, an energy-optimal intervention can be shown in the example of axle hybrids: The torque is only redistributed at the level at which it is necessary to overcome the situation of spinning wheels and Provision of propulsion is necessary.

The limit torque can be determined in various preferred ways. For example, information about the maximum force that can be transmitted via the respective wheel subset can be obtained or received (eg from an executing computing unit). This information can, for example, Include value of the maximum force that can be transmitted via the respective wheel subset or also a value of the limit torque. The limit torque is thus determined externally here, for example by another computing unit (for example in an ASR system). However, information for determining an effective normal force on the respective subset of wheels and/or information for a dynamic wheel radius and/or information for a coefficient of friction between the wheels and the roadway and/or information for determining the coefficient of friction can also be received (e.g. from an executing computing unit). The limit torque is thus determined internally (in the executing processing unit) from the received values. The information received or read in can then include, for example, sensor data or signals from other computing units.

The spinning of the at least one wheel of one of the several wheel subsets is preferably determined if a wheel speed of this one wheel subset deviates more than a threshold value from an associated reference value, the associated reference value preferably being determined from a wheel speed of at least one of the other wheel subsets. In the case of a subset of wheels with only one wheel, the wheel speed then corresponds to the speed of the wheel; in the case of several wheels in a subset of wheels, on the other hand, it preferably corresponds to a mean value, e.g. the arithmetic mean. As soon as there is a significant speed difference between the wheel subsets (e.g. between the front and rear axles), experience has shown that it can be assumed for certain that the faster rotating wheels have exceeded the traction limit between the tires and the road in driving driving conditions.

Likewise, the spinning of the at least one wheel of one of the several wheel subsets can be determined if a slip of the at least one wheel or an average slip of this one wheel subset deviates from an associated reference value, with the slip or the average slip preferably using a wheel speed of the at least one wheel or of this one wheel subset and a speed of the vehicle determined independently of this wheel speed (eg via GPS). Of the Slip is a dimensionless description of wheel speed related to vehicle speed.

Determining the limit torque preferably includes obtaining information that the at least one wheel is spinning, or obtaining information about wheel speed values and/or information about a speed of the vehicle. As with the limit torque, wheel spin can be determined externally or internally (e.g. in an executing processing unit).

A computing unit according to the invention, e.g. a control unit of a motor vehicle, is set up, in particular in terms of programming, to carry out a method according to the invention.

The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is advantageous because this causes particularly low costs, especially if an executing control device is also used for other tasks and is therefore available anyway. Suitable data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard drives, flash memories, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and refinements of the invention result from the description and the attached drawing.

The invention is shown schematically in the drawing using an exemplary embodiment and is described below with reference to the drawing.

Brief description of the drawings FIG. 1 schematically shows a vehicle in which a method according to the invention can be carried out.

FIGS. 2 and 3 schematically show a sequence of a method according to the invention in a preferred embodiment.

FIG. 4 schematically shows a diagram of the adhesion coefficient to explain the invention.

embodiment(s) of the invention

FIG. 1 shows a vehicle 100 in which a method according to the invention can be carried out. The vehicle 100 has, for example, four wheels 112, 114, 122, 124, which are assigned to two axles or vehicle axles 110, 120. According to the invention, the wheels 112 and 114 form a wheel subset, as do the wheels 122 and 124. The two axles 110, 120 and the corresponding wheel subsets 112, 114 and 122, 124 can be driven independently of one another. However, it should be emphasized that the invention can also be used with more than two axles, i.e. three or more axles that can be driven independently of one another (e.g. in trucks or the like).

For this purpose, an internal combustion engine 130 is provided as a drive unit for the axle 110 , which is supplied with fuel via a tank 136 and which is connected to a differential 116 of the axle 110 via a clutch 132 and a transmission 134 . An electric machine 140 is provided as a drive unit for axle 120 , which is supplied with electrical energy or controlled via a battery 144 and an inverter 142 and is connected to a differential 126 of axle 120 . In addition, a computing unit 150 embodied as a control unit is provided, which is used, for example, to control internal combustion engine 130 and electric machine 140 and thus, in particular, to correspondingly implement a requested torque.

The vehicle 100 shown thus has a so-called P4 topology by way of example. This is characterized by the fact that the two drive units, the two Axles 110, 120 of the vehicle can mechanically drive independently. This represents a typical implementation of a hybrid vehicle in which, for example, an electrified rear axle (axle 120) and a front axle (axle 110) driven by an internal combustion engine are provided.

The following description deals with this variant in particular. Equivalent situations are conceivable with other types of drive and other combinations of drive types (e.g. electrified front axle, combustion engine rear axle), but also, for example, two electrically driven axles or a wheel-specific drive. Analogously, the method can also be applied to a number of driven axles that differs from two.

In the figures 2 and 3, a sequence of a method according to the invention is shown schematically in a preferred embodiment. As already mentioned, this should be done using the example of a hybrid vehicle in P4 topology, and in particular also starting from the case that the initial split of the requested torque is such that the front axle is allocated 100%.

Figure 2 shows an exemplary embodiment in which in a block 200 an excess torque (i.e. a proportion of torque that exceeds a value that can be transmitted to the ground) from the front axle (index VA) as the first partial wheel quantity to the rear axle (index HA) is transmitted as the second wheel subset. For this purpose, FIG. 2 shows how a requested torque MA—this can be requested, for example, by a driver or a driver assistance system—to a value between an upper limit torque Mc,max, A for the front axle and a lower limit torque Mc. min.vA for the front axle is limited. The upper limit torque corresponds to a maximum drive force that can be transmitted via the respective subset of wheels, at which no wheel of the respective subset of wheels spins. The lower limit torque can be provided, for example, to prevent wheels from locking, but is no longer relevant when the vehicle is accelerating (positive drive torque). In purely physical terms, the lower limit torque means an inverted upper limit torque. The same The coefficient of adhesion works both when accelerating and when braking (neg. torque, recuperation with an electric machine). In this way, a target torque M _SO H,VA can be obtained that corresponds to a portion of the requested torque MA that is to be implemented on the front axle. This is also fed to a subtraction from the desired torque MA in order to calculate the surplus M'SOII.HA ZU to be distributed to the rear axle HA.

The unlimited setpoint torque M'SOII.HA for the rear axle then results accordingly, which—as far as possible—should be implemented there. As for the front axle, this is then limited to a value between an upper limit torque Mc,max,HA and possibly a lower limit torque Mc,min.HA for the rear axle. A setpoint torque Msoii.HA for driving the rear axle is then obtained in this way.

The two target torques can then be converted according to step 210, i.e. transmitted to the drive units as target values.

In this way, therefore, there follows a redistribution of that portion of the driver's request that cannot be transmitted by one of the axles, and possibly a limitation to the maximum torque that can be transmitted. The portion of the torque that cannot be implemented on the front axle due to the limitation is specified for the rear axle as the target torque and is limited by the limit torques of the rear axle.

In a further variant it would be conceivable that a certain distribution of the drive torque to the axles is already specified (eg due to a hybrid operating strategy). Based on this distribution, the torque setpoints (of both axes) are then limited, which leads to a redistribution of the requested torque to the other axis, to the extent that the limit torque is exceeded on one of the axes and not yet on the other axis is reached. FIG. 3 now shows how these two (upper) limit torques MG,max,vA for the front axle and MG,max,HA for the rear axle can be determined. As already mentioned, these limit torques correspond to those driving forces that can be transmitted to the roadway or the ground at the maximum on the relevant axle.

The proposed method includes determining a state of spinning wheels, e.g. using the difference An of the mean values from the wheel speeds (left/right) of the front axle nvA and rear axle HHA. These mean values can be determined, for example, in a block 300 from the individual wheel speeds—denoted here by ni. This difference An is also referred to below as the axle speed difference.

This detection or this determination 300 activates the calculation of the currently maximum transmissible torque on the axle with the spinning wheel/wheels. The calculation of the maximum transferable torque requires the calculation of the maximum effective coefficient of adhesion between the wheels and the road. For this purpose, it is checked in an (optional) block 312, for example, whether a current speed is below a threshold VA. For example, it may be desirable to redistribute torque only in a low speed range, e.g., because wheel spin is not normally expected at high speeds.

If this is answered in the affirmative in block 312, after a possibly short delay 314, a calculation 320 of the limit torques can take place. However, this query can also be omitted.

The calculation 320 of the limit torques is to be explained below. In this regard, reference is also made to FIG. 4, which shows a schematic diagram of the coefficient of adhesion p to explain the invention. This shows the relationship between the slip s of the tire or wheel and the coefficient of adhesion p, which is achieved during power transmission. A slip of 0% describes a rolling, non-driven wheel, while a slip of 100% means a spinning wheel when the vehicle is stationary describes. In principle, there is always slip in a driven wheel.

The curve i applies to dry asphalt, the curve V2 to wet asphalt and the curve V3 to loose ground such as gravel. The curves for solid road surfaces (Vi, V2) each have a clear maximum (at just over 20% slip) and show a reduction in the coefficient of adhesion with increasing slip. Within the scope of the proposed method, the state of the maximum mentioned here should ultimately be “captured” by using the occurrence of the axle speed difference as a signal.

As soon as there is a significant speed difference between the front and rear axles, it can be taken for granted that the faster rotating wheels have exceeded the traction limit between the tires and the road. In addition, it can be assumed that the tire converts the maximum drive torque into a drive force that accelerates the vehicle immediately before exceeding the traction limit (i.e. before spinning).

The proposed method aims to determine the coefficient of adhesion p by changing the following relationship of the maximum transferrable driving force Fmax through friction between the tires or wheels and the road.

^F ^ = F ' ^F z -

Here, F _max is the maximum transferrable drive force and Fz is the normal force acting between the tire or wheel and the road surface. The aim is to calculate the driving force and the normal force immediately before the axle speed difference occurs on the axle whose wheels are spinning due to the driving torque. The calculation of the coefficient of adhesion p is then as follows: .. > max

^F1z '

The current drive force FAntr can be calculated from the drive torque /ntr at the wheel via the radius of the tire - the dynamic wheel radius rd _yn is used here. The drive torque / ntr is typically already modeled or calculated within the drive software. At the wheel, the drive torque /ntr is divided into a portion _Mwheel , which results in a driving force, and a further portion Mro t, which is used for the rotary acceleration of the components of the drive train. The latter can be determined mathematically, see also block 340. To do this, it is necessary to determine the angular acceleration dco/dt of the wheels and to know the mass moments of inertia Jrot of the drive train. The portion M _ro t of the drive torque that is used for the rotational acceleration of the components of the drive train can be calculated as follows. ebskraft FAntr then results as follows:

The normal force Fz is variable due to the longitudinal acceleration of the vehicle and the incline of the road, so it can be divided into a static part z.stat (e.g. weight part, in particular static wheel load from weight distribution and incline of the road) and a variable (particularly acceleration-dependent) part A z It can be divided up, cf. block 330. It can be calculated using vehicle parameters and vehicle state variables, denoted here generally by P, and the current longitudinal acceleration a, which also includes a possible roadway incline.

In the case of longitudinal dynamic considerations, there are the following influencing variables: The incline angle of the road influences the proportion of the weight force acting in the direction of the normal force of the wheels.

In addition, the gradient angle results in a force component of the weight force, which acts in the longitudinal direction of the vehicle due to the gradient. This changes the distribution of weight between the front and rear axles.

The third influence results from longitudinal acceleration (braking/driving), which leads to a dynamic change in the distribution of weight between the front and rear axles. To put it simply, this causes the vehicle to become lighter at the front and heavier at the rear (i.e. pitch backwards) with positive acceleration. The reverse is the case with negative acceleration, in which case the vehicle pitches forward. This is triggered by a lever arm between the center of gravity and the road (with height h). This creates a moment that causes the vehicle to pitch either forward or backward. Longitudinal acceleration can be caused by an incline or by propulsion with one of the prime movers (corresponds to the derivative of the vehicle speed). This can also be seen from the following formula.

The dynamic or effective normal force FZ. A = Fz,stat + AFz for the front axle is calculated as follows:

The necessary measured variables {m for the mass of the vehicle, Z for the wheelbase, l _h for the distance from the vehicle’s center of mass to the rear axle, h for the vertical distance from the vehicle’s center of mass to the roadway and g for the gravitational constant) to take into account the incline a of the roadway and the longitudinal acceleration «of the vehicle eg provided by the ESP control unit. The same applies to the rear axle, FZ, HA.

Due to the fact that the state of spinning wheels can be detected but is delayed in relation to the state of the maximum transmitted driving force, the signals of the driving force and the normal force are delayed in the function by dead time elements 350, 352, 354. through the Application of the time constant makes it possible to set the time interval between the occurrence of the maximum drive force and the detection of the axle speed difference as a dead time. The dead time typically depends on several of several factors, eg the time delay between measurement of the wheel speeds and reception in the control unit. In addition, the wheel speeds are usually also filtered somewhat, which means an additional delay. There is also a delay because the state of spinning wheels can only be reliably detected when the axle speed difference exceeds a sufficiently high threshold value (to avoid false alarms). A typical range of values would be between 0 and 500 ms, for example.

As explained above, the coefficient of adhesion p is calculated as the quotient of the delayed driving force and the delayed normal force. The limit torques for the front and rear axles can then be determined from the calculated coefficient of adhesion p, the normal force that is currently occurring and the dynamic radius rd _yn . It is assumed here that the coefficient of adhesion p determined on the basis of the spinning wheels also acts for at least a short time on the wheels that are not spinning and also when the normal axle forces have changed. This assumption can definitely be made for regular journeys and vehicle and road conditions. By multiplying the normal axle force and the dynamic radius of the tire, the calculated coefficient of adhesion results in a limit torque for both axles, especially for the one that is not spinning.

Instead of the axle speed difference, the slip could be used as an input variable for triggering the function, as already mentioned at the beginning. Slip is a dimensionless description of wheel speed related to vehicle speed. As a result, a speed-independent slip threshold could be used to detect wheel spin.

The use of the slip as an input value usually requires that a plausible speed signal is available, which is calculated from a source other than the wheel speeds. If this possibility does not exist, the Threshold of the axle speed difference for the detection of spinning wheels are implemented with a speed dependency.

Claims

Expectations

1 . Method for dividing a requested torque for driving a vehicle (100) with wheels, wherein several wheel subsets (112, 114; 122, 124), each with at least one wheel for transmitting driving force to a ground, can be driven independently of one another, with the following steps:

determining (300) that at least one wheel of one of the plurality of wheel subsets is beginning to spin,

Determining (320), for each of the plurality of wheel subsets, a limit torque (Mc.max.vA, MG,max,HA), which corresponds to a maximum drive force that can be transmitted via the respective wheel subset, at which no wheel of the respective wheel subset spins,

Determining (200) a distribution of the requested torque (MA) to the plurality of wheel subsets (112, 114; 122, 124) in such a way that no more than the respective limit torque (M _G ,max, A, M _G ,max,HA) is present, and

causing a conversion (210) of the determined partition.

2. The method of claim 1, wherein determining the allocation of the requested torque (MA) to the plurality of wheel subsets comprises:

Reducing one of the wheel subsets with the spinning wheel assigned torque by a differential torque at least up to the limit torque (Mc.max.vA, Mc.max.HA) of this wheel subset, and increasing at least one of the other wheel subsets assigned torque by the differential torque, preferably but for each wheel subset at most up to the respective limit torque (Mc,max, A, Mc,max,HA). Method according to claim 1 or 2, wherein the respective limit torque (MG,max,vA, MG,max,HA) based on an effective normal force (FZ.VA, FZ,HA) on the respective wheel subset, a dynamic wheel radius (rd _yn ) and a coefficient of adhesion (p) between the wheels and the ground, which is present at a point in time before, in particular immediately before, recognizing the beginning of the spinning of the at least one wheel. Method according to claim 3, wherein the adhesion coefficient (p) is determined based on the maximum drive force that can be transmitted at this point in time via the respective subset of wheels and the effective normal force (FZ.VA, FZ.HA) on the respective subset of wheels. Method according to one of the preceding claims, wherein the determination (200) of the allocation of the requested torque (MA) to the plurality of wheel subsets is carried out repeatedly or continuously according to one of the following criteria: as long as it is determined that at least one wheel begins to spin, for a predetermined period of time from initially determining that at least one wheel is beginning to spin for as long as determining that at least one wheel is beginning to spin and thereafter for a predetermined period of time. Method according to Claim 5, in which the predetermined time period is specified according to one of the following criteria: as a fixed value, depending on a wheel speed (nvA, HHA) of the wheel subset at which the wheel begins to spin, depending on the limit torque (Mc .max A, Mc,max,HA) the wheel fraction at which the wheel begins to spin, depending on a history of adjustments made to the current split. Method according to one of the preceding claims, wherein the determining (320) of the limit torque (Mc.max.vA, Mc,max,HA) comprises: Obtaining information on the maximum force that can be transmitted via the respective subset of wheels, or

Obtaining information for determining an effective normal force (FZ.VA, FZ.HA) on the respective wheel subset and/or information about a dynamic wheel radius (rd _yn ) and/or information about a coefficient of adhesion (p) between the wheels and the ground and /or information on determining the coefficient of adhesion.

8. The method according to any one of the preceding claims, wherein the beginning of the spinning of the at least one wheel of the one of the several wheel subsets is determined when a wheel speed of this one wheel subset deviates from an associated reference value by more than a threshold value, the associated reference value preferably consisting of a Wheel speed at least one of the other wheel subsets is determined.

9. The method according to any one of the preceding claims, wherein the beginning of the spinning of the at least one wheel of the one of the plurality of wheel subsets is determined when a slip (S) of the at least one wheel or an average slip of this one wheel subset deviates from an associated reference value, wherein the slip or the average slip is preferably determined using a wheel speed of the at least one wheel or this one wheel subset and a speed of the vehicle determined independently of this wheel speed.

The method of any preceding claim, wherein determining (300) that at least one wheel begins to spin comprises:

Obtaining information that the at least one wheel is beginning to spin, or

Obtaining information on wheel speed values (ni) and/or information on a speed of the vehicle.

11. The method according to any one of the preceding claims, wherein at least one of the plurality of wheel subsets has two wheels belonging to the same vehicle axle. - 22 - Method according to one of the preceding claims, wherein at least one of the plurality of wheel subsets can be driven by means of an internal combustion engine (130) and at least one other of the plurality of wheel subsets can be driven by means of at least one electric machine (140), and/or wherein at least two of the plurality of wheel subsets are each can be driven by at least one electrical machine. Method according to one of the preceding claims, wherein the determination (200) of the distribution of the requested torque (MA) to the plurality of wheel subsets such that no more than the respective limit torque is present at any of the plurality of wheel subsets, taking into account a torque limitation which is imposed by a Traction control system is specified, includes. Arithmetic unit (150) which is set up to carry out all method steps of a method according to one of the preceding claims. Computer program which causes a processing unit (150) to carry out all method steps of a method according to one of Claims 1 to 13 when it is executed on the processing unit (150). Machine-readable storage medium with a computer program according to claim 15 stored thereon.