Method for controlling a vehicle, drive control unit and vehicle

Abstract

The invention relates to a method for controlling a vehicle having at least one electric drive (3. I) for driving wheels (2. I), the drive control unit (10) being designed to generate a target drive torque and / or a target drive speed and to output the target drive torque and / or the target drive speed to the respective drive (3. I), the method comprising the following steps: ascertaining a vehicle speed (v1); -ascertaining an actual wheel dynamics variable which characterizes the rotational behavior of the individual wheel; ascertaining a threshold value associated with the wheel (2. I); -ascertaining a control deviation between the actual wheel dynamics variable and a threshold value, and, in the event of an inadmissible control deviation,-limiting the target drive torque and / or the target drive speed of the wheel (2. I) having the inadmissible control deviation, said target drive torque and / or the target drive speed being / are limited for the wheel (2. I) having the inadmissible control deviation, said target drive torque and / or the target drive speed being / are limited for ascertaining that the wheel (2. I) of a certain axle has different control deviations on each side. According to the invention, an external brake request signal is generated and output by the drive control unit, on the basis of which external brake request signal the service brake on the wheel (2. I) having a higher adjustment deviation is actuated, a boundary drive torque and / or a boundary drive rotational speed being determined or adjusted as a function of a brake torque applied by the actuated service brake (7. I).

Description

Technical Field

[0001] The present invention relates to a method for controlling a vehicle, a drive control unit for executing the method, and a vehicle having the drive control unit. Background Art

[0002] To ensure vehicle stability, excessive wheel slip (drive slip) caused by drive torques that are too high for a given road surface friction coefficient must be limited when driving / starting the vehicle. This limitation must be achieved in a suitable manner by applying the necessary lateral guiding forces in addition to the propulsion force. To achieve this, highly dynamic and precise limiting or definition of the drive torque achieved by the respective drive is first necessary.

[0003] In the case of wheel-specific electric drives, the drive system typically controls wheel slip only at the slipping wheel, for example by limiting the required target drive torque in a slip control loop via a drive control unit. For central drives that electrically drive the vehicle's wheels axle-by-axle, an automatic slip control (ASR) is typically implemented in an electronic brake system, controlled, for example, by a brake control unit. The brake control unit monitors the actual wheel speeds of the individual wheels and then calculates axle-specific limitations for the target drive torques for these wheels. These limitations are then sent to the drive control unit for axle-based output of the correspondingly limited target drive torques for the wheels of the respective axle. If the wheels of the axle still exhibit different slip behavior, wheel-specific braking interventions can optionally be performed using the service brakes of the electronic brake system. This is accomplished within the framework of the automatic slip control (ASR) via a slip control loop implemented in the brake control unit.

[0004] However, the dynamics of such control of a central drive using wheel-specific braking interventions is usually limited due to the control implemented in the brake control unit of the electronic brake system. In contrast, the control to a specific wheel slip in a wheel-specific electric drive is carried out directly via the drive control unit (by limiting the target drive torque) with the highest possible dynamics. Summary of the Invention

[0005] Based on this, the object of the present invention is to specify a method for controlling a vehicle, with which a safe operation of the vehicle in terms of driving dynamics can be ensured in a simple manner. The object of the present invention is also to specify a drive control unit and a vehicle.

[0006] According to the invention, this object is achieved by a method, a drive control unit and a vehicle according to the independent claims. The dependent claims describe preferred developments.

[0007] Therefore, according to the present invention, a method for controlling a vehicle is provided, the vehicle having a drive system, wherein the drive system has a drive control unit and at least one electric drive for driving the wheels of the vehicle individually or axle-specifically, wherein the drive control unit is designed to generate a target drive torque and / or a target drive speed as a function of a drive request and output these to the respective drive; and

[0008] A braking system comprising a brake control unit and service brakes for decelerating wheels of a vehicle in a wheel-specific manner, the method comprising at least the following steps:

[0009] - Read or obtain the vehicle speed of the vehicle;

[0010] - reading or determining at least one actual wheel dynamics variable, which characterizes the rotational behavior of an individual wheel;

[0011] - reading or determining the wheel-assigned threshold values ​​of the respective actual wheel dynamics variables;

[0012] - If a control deviation between an actual wheel dynamics variable of a wheel and a threshold value assigned to the same wheel is determined and an impermissible control deviation exists for a wheel driven by a drive, in particular if the threshold value for this wheel is exceeded:

[0013] - limiting the target drive torque and / or target drive speed of the electric drive which drives the wheels with an impermissible control deviation to a limit drive torque and / or a limit drive speed; and

[0014] - determining whether the impermissible control deviation of the relevant wheel differs from the control deviation of at least one other wheel on the same axle, which is driven by the same electric drive, in particular a central electric drive (central drive),

[0015] In the event that a different control deviation is detected for the wheels of a certain axle, an external brake request signal is generated by the drive control unit and output to the brake control unit. Based on the external brake request signal, the service brake is actuated at least at the wheel of the relevant axle at which the greater control deviation is present.

[0016] In this case, a limit drive torque and / or a limit drive speed is determined or adjusted as a function of the braking torque applied by the actuated service brake, so that subsequently, by a combination of braking intervention and limitation of the drive torque, the control deviation of the respective wheel is brought back into the permissible range and the respective threshold value is observed.

[0017] This advantageously recognizes that an additional braking action at one wheel of an axle can be accompanied by an increase in the drive torque at another wheel of the same axle. This is because the additional braking action reduces the limitation of the drive action, which in a central drive can manifest as an increase in the drive action at the other, unbraked wheel. Overall, this increases the propulsion force while maintaining threshold values ​​for the wheel's rotational behavior.

[0018] Preferably, it is also provided that: knowing or reading

[0019] - the actual slip of the respective wheels, and / or

[0020] - the actual rotational speed of the respective wheels or the respective drives, and / or

[0021] - the actual speed of the respective wheels or the respective drives,

[0022] as at least one actual wheel dynamics variable.

[0023] In this way, the rotational behavior of the respective wheels can be taken into account in different ways, wherein the brake control unit and / or the drive control unit can determine these variables and make them available in a simple manner for further processing. The dual determination and provision can also advantageously allow the values ​​to be checked for plausibility.

[0024] Preferably, provision is also made for the actual wheel speed of the respective wheel to be determined or read out as the actual wheel dynamics variable, wherein the actual wheel speed is measured by a wheel speed sensor at the respective wheel and / or by a speed sensor located on each axle downstream of the output of the differential on each side. This allows the rotational behavior of the wheel in the form of the wheel speed to be determined in various ways, wherein a plausibility check can also be performed due to the double detection. Subsequently, the respective actual wheel dynamics variable can also be determined or calculated based on the wheel speed.

[0025] Preferably, it is also provided that: knowing or reading

[0026] - Slip threshold, and / or

[0027] - Speed ​​threshold, and / or

[0028] - speed threshold,

[0029] as the threshold for the respective wheels.

[0030] Depending on which actual wheel dynamics variable is taken into account, a respective threshold value can therefore also be assigned, which can then be checked for each individual wheel to determine whether the threshold value is exceeded, in order to be able to detect inadmissible deviations in the wheel rotational behavior.

[0031] Preferably, provision is also made for the actual wheel dynamics parameters of the respective wheels to be determined or read out by the drive control unit and / or the brake control unit, and / or for threshold values ​​for the respective wheels to be determined in the drive control unit and / or the brake control unit. Thus, the determination of the wheel rotational behavior can be detected and the threshold values ​​determined in the drive system itself. This minimizes transmission paths and thereby speeds up the regulation of the drive power, i.e., the limitation, and the determination of the wheel-specific braking effect, since this regulation is performed in the drive system or the drive control unit. However, since the brake system or the brake control unit determines threshold values ​​for its own determined wheel rotational behavior (e.g., for stability control and other braking functions within the brake system), these determined actual values ​​and threshold values ​​can also be transferred to the drive control unit, thereby saving additional computational and processing effort. Furthermore, a plausibility check can be performed by comparing the rotational behavior or threshold values ​​determined by the drive system with the rotational behavior or threshold values ​​determined by the brake system.

[0032] Preferably, provision can also be made for determining or adjusting a limit drive torque and / or a limit drive speed as a function of the braking torque applied by the actuated service brake, such that, due to the limitation of the target drive torque and / or target drive speed of the drive driving the wheel with the impermissible control deviation in combination with the braking torque applied to the same wheel, the actual wheel dynamics of the respective wheel falls below a threshold value again and / or the permissible control deviation of the respective wheel reappears. Advantageously, a braking action and a driving action are thus applied to one wheel, which together ensure a permissible rotational behavior of the respective wheel, so that, at the same time, an optimal propulsion force is generated solely by the driving action at the other wheel on the same axle.

[0033] Preferably, provision is also made for the brake request signal to be transmitted from the drive control unit to the brake control unit via a data connection, in particular a CAN data bus. This ensures robust and rapid data transmission, allowing for rapid and safe intervention at the respective wheel in response to the intended braking action.

[0034] Preferably, it is further provided that in the event of an impermissible control deviation of a wheel driven by the drive,

[0035] First, the target drive torque and / or target drive speed of the drive that drives the wheels with an impermissible control deviation is limited to a limit drive torque and / or a limit drive speed; and

[0036] Then, in the case where it is known that the wheels of the axle have different adjustment deviations on each side, an external brake request signal is generated by the drive control unit and output to the brake control unit. Based on the external brake request signal, the service brake at least at the wheel of the relevant axle with the higher adjustment deviation is actuated. Then, depending on the braking torque applied by the actuated service brake, the limit drive torque and / or the limit drive speed is adjusted.

[0037] Therefore, the drive power is first withdrawn to "eliminate" the impermissible rotational behavior. Only then is the braking action applied to the respective wheels, and the drive power is restored by setting a limit drive torque or limit drive speed. Thus, the faster control loop in the drive control unit is first used to eliminate the unsafe state, and only then is the slower control loop in the brake control unit activated. Therefore, the safe state, i.e., the permissible rotational behavior, takes priority over better propulsion.

[0038] However, it is also possible in principle to first carry out a side-specific actuation of the respective service brake and only thereafter or simultaneously to carry out a limitation of the drive power by limiting the target drive torque or the target drive speed.

[0039] According to the present invention, a drive control unit for a vehicle is also provided, in particular for carrying out the method according to the present invention, the drive control unit having an input interface and an output interface, wherein the drive control unit is designed to generate a target drive torque and / or a target drive speed as a function of a drive request and output them via the output interface to at least one electric drive of the vehicle, wherein the drive control unit is further designed to:

[0040] - knowing or reading the vehicle speed of the vehicle via an input interface;

[0041] - determining or reading via an input interface at least one actual wheel dynamics variable which characterizes the rotational behavior of an individual wheel of the vehicle;

[0042] - determining or reading out via an input interface the wheel-assigned threshold value of the respective actual wheel dynamics variable;

[0043] - If a control deviation between an actual wheel dynamics variable of a wheel and a threshold value assigned to the same wheel is determined and an impermissible control deviation exists for a wheel driven by a drive, in particular if the threshold value for this wheel is exceeded:

[0044] - limiting the target drive torque and / or target drive speed generated and output by the drive which drives the wheels with an impermissible control deviation to a limit drive torque and / or a limit drive speed; and

[0045] - determining whether the impermissible control deviation of the relevant wheel differs from the control deviation of at least one other wheel on the same axle, which is driven by the same drive,

[0046] The drive control unit is designed to, upon detection of different control deviations on the wheels of a certain axle, generate an external brake request signal and output the external brake request signal via the output interface, so that based on the external brake request signal, the service brake of at least the wheel of the relevant axle with the higher control deviation can be actuated.

[0047] The drive control unit is designed to determine or adjust a limit drive torque and / or a limit drive speed as a function of a braking torque applied by the actuated service brake.

[0048] Preferably, it is additionally provided that: the drive control unit is designed as follows:

[0049] - Controlling the electric drive at each wheel in wheel-specific drive modes; and

[0050] - In an axle-specific drive mode preferred for the method according to the invention, at least one electric drive of the wheels of at least one axle that jointly drive the vehicle is actuated. This allows the drive control unit to be operated in correspondingly different modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention is described in more detail below with reference to the accompanying drawings, wherein:

[0052] Figure 1a 、 Figure 1b A schematic diagram of a vehicle is shown; and

[0053] Figure 2 A flow chart of the method according to the invention is shown. DETAILED DESCRIPTION

[0054] Figure 1a A vehicle 1 is shown with wheels 2.i (i=1, 2, 3, 4), wherein each wheel 2.i can be driven individually via an electric drive 3.i (i=1, 2, 3, 4), for example by an electric motor. Figure 1bA vehicle 1 is shown in which the wheels 2.i of only one axle FA (here, by way of example, the rear axle HA) are jointly driven via a central electric drive 3.0 (central drive), with the power distributed via a differential 6. Similarly, an electric drive (not shown) assigned to the front axle VA can also be provided. Thus, depending on the drive mode, the vehicle 1 or the wheels 2.i can be electrically driven on a wheel-by-wheel or axle-by-axle basis.

[0055] In this vehicle 1 , the respective drives 3.i (i=0, 1, 2, 3, 4) are electrically controlled by a central drive control unit 10 of a drive system 9 . To this end, the central drive control unit generates drive control signals S3.i (i=0, 1, 2, 3, 4) and outputs them to the respective drives 3.i via an output interface 12 in order to accelerate vehicle 1 in lane 4 in accordance with a manually or automatically specified drive request AD. The target drive torque M3S.i and / or target drive speed N3S.i for the respective i-th electric drive 3.i can be encoded in the drive control signal S3.i, which then implements these target drive torques and / or target drive speeds accordingly, wheel-specifically or axle-specifically.

[0056] The drive control unit 10 also has one or more input interfaces 11, through which the

[0057] - vehicle speed v1 of vehicle 1 relative to lane 4, and

[0058] - the actual wheel speed N2I.i of each wheel 2.i, and / or

[0059] - the actual wheel circumferential speed v2I.i of each wheel 2.i, and / or

[0060] The actual drive speed N3I.i of the individual drives 3.i is thus read out at once about the speed of the entire vehicle 1 and, in addition, wheel-specific or axle-specific information about the rotational or driving behavior of the individual wheels 2.i is read out.

[0061] The vehicle speed v1 can be provided, for example, by the brake control unit 20 of the electronic brake system 15 (EBS), which determines the vehicle speed in any manner. The actual wheel speed N2I.i of the i-th wheel 2.i can be measured by the wheel speed sensor 5.i at the i-th wheel 2.i, and the actual drive speed N3I.i of the i-th electric drive 3.i can be measured by an incremental encoder or a resolver within the respective i-th drive 3.i. It is assumed here that the actual wheel speed N2I.i of the i-th wheel 2.i corresponds to the actual drive speed N3I.i of the i-th drive 3.i that drives the i-th wheel 2.i, or that there is a fixed relationship such that the actual wheel speed N2I.i of the respective wheel 2.i can be derived from the actual drive speed N3I.i of the drive 3.i assigned to the wheel 2.i by a fixed relationship, such as a transmission ratio constant. Alternatively, in accordance with Figure 1b In the embodiment of , the actual wheel speed N2I.i of the i-th wheel 2.i can also be measured by speed sensors 8, which are arranged behind the output ends on each side of the differential 6.

[0062] The actual wheel speeds N2I.i of the individual wheels 2.i and / or the actual wheel circumferential speeds v2I.i that can be calculated therefrom are typically already available within the framework of the control system, in particular the ABS control system, performed in the brake control unit 20 and can be transmitted, for example, via a corresponding data connection 15, such as a CAN bus 15a, to the central drive control unit 10. However, in addition to the brake control unit 20, the drive control unit 10 can also be directly connected to the wheel speed sensors 5.i at the individual wheels 2.i in a signal-conducting manner, for example via a Y-connector, and receive the actual wheel speeds N2I.i itself (analog / digital).

[0063] Using this structure, Figure 2 The method for controlling the vehicle 1 shown by way of example in FIG. 1 can be implemented as follows:

[0064] In a first step ST1 , the vehicle speed v1 is first read, and in a second step ST2 , the wheel-specific (slip-affected) rotational or driving behavior of the individual wheels 2 . i is read, wherein for this purpose, as described above,

[0065] - in the wheel-specific drive mode AR, reading out or determining the actual drive speed N3I.i of the drive 3.i and / or the actual drive speed v3I.i which can be calculated therefrom, and / or

[0066] - in axle-specific drive mode AA (central drive), reading out or determining the actual wheel speed N2I.i and / or the actual wheel circumferential speed v2I.i of the individual wheels 2.i,

[0067] As actual wheel dynamics variables GI.i relating to the i-th wheel 2.i, in the case of a wheel-specific drive mode AR, the actual wheel speeds N2I.i and / or actual wheel circumferential speeds v2I.i of the individual wheels 2.i can be used as redundancy or to supplement the plausibility check, which actual wheel speeds and / or actual wheel circumferential speeds are identical or have a defined constant relationship between them.

[0068] Regardless of drive mode AA or AR, the actual slip s2I.i of each wheel 2.i can also be determined as a further actual wheel dynamics variable GI.i. The actual slip s2I.i of each wheel 2.i is generated, for example as a percentage or an absolute value, as a function of the actual wheel speed N2I.i of the respective wheel 2.i (or the actual drive speed N3I.i of the respective drive 3.i) and the vehicle speed v1. The actual slip s2I.i represents the speed difference between the road speed (vehicle speed v1) and the actual wheel circumferential speed v2I.i of the respective wheel 2.i, which is derived from the actual wheel speed N2I.i and can also be derived from the actual drive speed v3I.i of the respective drive 3.i of the respective wheel 2.i.

[0069] In a third step ST3, a threshold value Ti is read or determined for each wheel 2.i, wherein the threshold value can be a slip threshold value s2T.i and / or a rotational speed threshold value NT.i and / or a speed threshold value vT.i. In this case, these threshold values ​​Ti; s2T.i; NT.i, vT.i indicate: With respect to the running aspects of the vehicle 1 with no problems in terms of driving dynamics,

[0070] - the actual slip s2I.i (slip threshold s2T.i) of the i-th wheel 2.i or

[0071] - what is the actual wheel speed N2I.i of the i-th wheel 2.i or what is the actual drive speed N3I.i (speed threshold value NT.i) of the i-th drive 3.i at the i-th wheel 2.i or

[0072] - the actual wheel circumferential speed v2I.i of the i-th wheel 2.i or the actual drive speed v3I.i of the i-th drive 3.i of the i-th wheel 2.i (speed threshold vT.i)

[0073] is permitted, although this may also depend on the circumstances.

[0074] The respective threshold values ​​Ti; s2T.i; NT.i, vT.i can be determined by the drive control unit 10 itself or by the brake control unit 20, for example, within the framework of a stability control implemented therein. The brake control unit 20 then transmits the respective threshold values ​​Ti; s2T.i; NT.i, vT.i to the drive control unit 10 via a data connection 15 (e.g., a CAN bus 15a) and the respective input interface 11.

[0075] Next, in a fourth step ST4, at time t, a wheel-specific (in the wheel-specific drive mode AR) or axle-specific (in the axle-specific drive mode AA) control deviation dA, namely a slip control deviation dsA and / or a speed control deviation dNA and / or a velocity control deviation dvA, is determined. The control deviation dA indicates, wheel-specifically or axle-specifically, a difference between the respective actual wheel dynamics variable GI.i and a threshold value Ti for the same variable.

[0076] The slip control deviation dsA therefore indicates the difference (wheel-specific) between the actual slip s2I.i of the respective wheel 2.i and the respective slip threshold value s2T.i, or the difference (axle-specific) between the actual slip s2I.i of the wheels 2.i of the respective axle FA (usually the higher actual slip s2I.i (“Select High”) or the average value of the wheels 2.i of the respective axle FA) and the respective slip threshold value s2T.i of these wheels 2.i (e.g. “Select High” or the average value). Correspondingly, the speed control deviation dNA indicates the difference (wheel-specific) between the actual wheel speed N2I.i of the respective wheel 2.i or the actual drive speed N3I.i of the respective drive 3.i and the respective speed threshold value NT.i, or indicates the difference (axle-specific) between the actual wheel speed N2I.i of the wheel 2.i or the actual drive speed N3I.i of the drive 3.i of the respective axle FA (e.g. "high selection" or average value) and the respective speed threshold value NT.i (e.g. "high selection" or average value) of these wheels 2.i. Correspondingly, the speed control deviation dvA indicates the difference (wheel-specific) between the actual wheel circumferential speed v2I.i of the respective wheel 2.i or the actual drive speed v3I.i of the respective drive 3.i and the respective speed threshold value vT.i, or indicates the difference (axle-specific) between the actual wheel circumferential speed v2I.i of the wheel 2.i or the actual drive speed v3I.i of the drive 3.i of the respective axle FA (e.g. "high selection" or average value) and the respective speed threshold value vT.i (e.g. "high selection" or average value) of these wheels 2.i.

[0077] If an impermissible control deviation dA is detected, i.e., a slip control deviation dsA and / or a speed control deviation dNA and / or a velocity control deviation dvA of at least one wheel 2.i, which manifests itself, for example, as an exceeding of respective threshold values ​​Ti; s2T.i; NT.i, vT.i, then in a fifth step ST5, the drive 3.i of the at least one wheel 2.i is controlled so that a predetermined limit drive torque M3G or a predetermined limit drive speed N3G is not exceeded. Thus, for each wheel 2.i experiencing excessive slip, the target drive torque M3S.i and / or target drive speed N3S.i, as transmitted by the respective drive control signal S3.i, is limited. This limitation is applied wheel-by-wheel in the wheel-specific drive mode AR, and correspondingly, axle-by-axle in the axle-specific drive mode AA.

[0078] By limiting the target drive torque M3S.i and / or target drive speed N3S.i of the relevant drive 3.i, the actual slip s2I.i, actual wheel speed N2I.i, actual drive speed N3I.i, actual wheel circumferential speed v2I.i, or actual drive speed v3I.i at the respectively affected wheel 2.i or drive 3.i is correspondingly also limited or set such that the permissible slip control deviation dsA and / or speed control deviation dNA and / or speed control deviation dvA is restored. As a result, the respective wheel 2.i experiencing drive slip is "caught" again.

[0079] In the case of axle-specific drive mode AA, in substep ST5a, the actual wheel speeds N2I.i provided by the wheel speed sensors 5.i are used to additionally monitor whether the rotational behavior of the respective wheels 2.i differs from one another before or after the aforementioned limitation of the target drive torque M3S.i and / or the target drive speed N3S.i of the relevant central electric drive 3.0 and the relevant axle FA. For example, if an impermissible control deviation dA (or a different control deviation dA from one another) is detected in the respective actual wheel dynamics variables GI.i before or after the aforementioned limitation of the target drive torque M3S.i and / or the target drive speed N3S.i of the wheels 2.i of the driven axle FA, then the drive control unit 10 generates an (external) brake request signal SB and outputs it to the brake control unit 10 via the output interface 12, for example, via the serial data connection 15, in particular the CAN bus 15a.

[0080] The side-specific activation of the service brakes 7.i of vehicle 1 is then encoded in the brake request signal SB. Braking request signal SB is generated as a function of the currently existing control deviation dA of the respective actual wheel dynamics variable GI.i of the associated wheel 2.i of the respective axle FA, so that a specific target brake pressure pS is applied to the service brake 7.i assigned to the wheel 2.i in order to generate a specific braking torque MB.i at the wheel 2.i. The target brake pressure pS or the resulting braking torque MB.i is determined such that the respective threshold value Ti for the wheel 2.i is maintained while limiting the target drive torque M3S.i and / or the target drive speed N3S.i of the associated central electric drive 3.0.

[0081] Therefore, wheels 2.i of axle FA with excessive drive force are no longer "caught up" solely by limiting the target drive torque M3S.i and / or target drive speed N3S.i of the associated central electric drive 3.0, but are additionally "caught up" by side-specific deceleration of the respective wheel 2.i. This results in the target drive torque M3S.i and / or target drive speed N3S.i of the associated central electric drive 3.0 being limited less strictly, since a portion of the impermissible rotational behavior of wheel 2.i is corrected by the respective service brake 7.i.

[0082] Therefore, the limit drive torque M3G or limit drive speed N3G of the central electric drive 3.0 can be selected higher in coordination with the braking request signal SB or the target brake pressure pS or the resulting braking torque MB.i, either initially (if braking torque MB.i is already active) or during subsequent adjustments (if braking torque MB.i is only established later). For the central drive, this results in the other wheel 2.i of the axle FA being driven with a higher target drive torque M3S.i (than in the absence of braking intervention) (due to less stringent restrictions). This allows the other wheel 2.i of the axle FA (which does not have an impermissible control deviation dA or has a lower impermissible control deviation dA relative to the other wheel 2.i) to continue to transmit a high drive torque. This improves the propulsion of the vehicle 1, particularly under µ-split conditions, i.e., when different friction coefficients occur on each side of the roadway 4.

[0083] Therefore, in sub-step ST5a, it is preferably generally provided that, under the μ-split condition, which can be identified by the different rotational behavior of the respective sides, the wheel 2.i of the axle FA with the lower control deviation dA is "recaptured" (threshold value Ti is again adhered to) solely by limiting the target drive torque M3S.i and / or target drive speed N3S.i of the associated central electric drive 3.0. Subsequently, the other wheel 2.i of this axle FA with the higher control deviation dA is additionally "recaptured" by the described side-specific braking intervention.

[0084] In summary, therefore, the limit drive torque M3G or limit drive speed N3G of central electric drive 3.0 is determined in coordination with the brake request signal SB or target brake pressure pS or the resulting braking torque MB.i of the respective wheel 2.i, so that the greatest possible propulsion force can be achieved for wheels 2.i of axle FA with a low control deviation dA (or no control deviation at all). The following possibilities are particularly conceivable for this implementation:

[0085] Upon detecting side-by-side differing rotational behavior or a side-by-side differing control deviation dA for the individual wheels 2.i of the axle FA, the drive control unit 10 first generates and outputs a braking request signal SB to individually decelerate the wheels 2.i of the axle FA with the greater control deviation dA. Only then is the driving behavior limited, or a limit driving torque M3G or a limit driving speed N3G determined as a function of the then-acting braking torque MB.i. Due to the generally low dynamics of brake control circuits, limiting the driving behavior and, thereby, eliminating the impermissible control deviation dA, is delayed.

[0086] To optimize this, the driving behavior can initially be limited, or a limit driving torque M3G or limit driving speed N3G can be determined, depending on the existing control deviation dA (e.g., "high selection"). This can be achieved with very high control dynamics. This limitation can then be subsequently adjusted during the subsequent or simultaneous establishment of the target brake pressure pS or the resulting braking torque MB.i for the respective wheel 2.i with the higher control deviation dA. This limitation is thus removed, which has the advantage that the impermissible control deviation dA is first corrected with high dynamics, and the propulsion force is subsequently optimized during the more slowly implemented superimposed brake control.

[0087] In this way, via the brake control unit 10 and with the aid of the wheel-specifically acting service brakes 7.i, a superimposed (slower) slip control loop can be activated, which supplements the highly dynamic slip control loop supported by the drive control unit 10 and the limitation of the target drive torque M3S.i and / or the target drive speed N3S.i, in order to improve performance even in the non-wheel-specific, axle-specific drive mode AA.

[0088] List of reference numerals (part of the specification)

[0089] 1 vehicle

[0090] 2.i wheels (i=1, 2, 3, 4)

[0091] 3.i Electric drive (i=0, 1, 2, 3, 4)

[0092] 4 lanes

[0093] 5.i Wheel speed sensor at 2.i on the i-th wheel (i=1, 2, 3, 4)

[0094] 6 Differential

[0095] 7.i Service brake at wheel 2.i at i

[0096] 8 Speed ​​sensor

[0097] 9 Drive system

[0098] 10 Drive control unit

[0099] 11 Input Interface

[0100] 12 output ports

[0101] 15 Braking System

[0102] 20 Brake control unit

[0103] AA Axle-specific drive modes

[0104] AD driver request

[0105] AR wheel-specific drive modes

[0106] dA regulation deviation

[0107] dNA speed regulation deviation

[0108] dvA Speed ​​regulation deviation

[0109] dsA slip adjustment deviation

[0110] FA Axles

[0111] GI.i Actual wheel dynamics parameter of the i-th wheel 2.i (i=1, 2, 3, 4)

[0112] HA rear axle

[0113] M3S.i Target driving torque of the i-th drive 3.i (i=0, 1, 2, 3, 4)

[0114] MB.i Braking torque at the i-th wheel (i=1, 2, 3, 4)

[0115] N2I.i Actual wheel speed of the i-th wheel 2.i (i=1, 2, 3, 4)

[0116] N3S.i Target drive speed of the i-th driver 3.i (i=0, 1, 2, 3, 4)

[0117] N3I. Actual drive speed of the i-th drive 3.i (i=1, 2, 3, 4)

[0118] NT.i Speed ​​threshold of the i-th wheel 2.i

[0119] pS Target brake pressure

[0120] s2I.i Actual slip of the i-th wheel 2.i

[0121] s2T.i is the slip threshold of the i-th wheel 2.i

[0122] S3.i drive control signal (i=0, 1, 2, 3, 4)

[0123] Ti is the threshold value of wheel 2.i of the i-th wheel

[0124] VA front axle

[0125] v1 vehicle speed

[0126] v2I.i Actual wheel circumferential velocity of the i-th wheel 2.i (i=1, 2, 3, 4)

[0127] v3I.i Actual driving speed of the i-th driver 2.i (i=1, 2, 3, 4)

[0128] vT.i Speed ​​threshold of the i-th wheel 2.i

Claims

1. A method for controlling a vehicle (1), said vehicle having: Drive system (9), wherein The drive system (9) comprises a drive control unit (10) and at least one electric drive (3.i) for driving the wheels (2.i) of the vehicle (1) individually or axle-specifically, wherein the drive control unit (10) is designed to generate a target drive torque (M3S.i) and / or a target drive speed (N3S.i) as a function of a drive request (AD) and output these to the respective drive (3.i); and A braking system (15), wherein the braking system (15) comprises a brake control unit (20) and service brakes (7.i) for wheel-specific deceleration of wheels (2.i) of the vehicle (1), the method comprising at least the following steps: - reading or obtaining the vehicle speed (v1) of the vehicle (1) (ST1); - reading or determining at least one actual wheel dynamics variable (GI.i) which characterizes the rotational behavior (ST2) of an individual wheel (2.i); - reading or determining the threshold value (Ti) assigned to the wheel (2.i) of the respective actual wheel dynamics variable (GI.i) (ST3); - if a control deviation (dA) between an actual wheel dynamics variable (GI.i) of a wheel (2.i) and a threshold value (Ti) assigned to the same wheel (2.i) is determined (ST4) and an impermissible control deviation (dA) exists for a wheel (2.i) driven by a drive (3.i), in particular if the threshold value (Ti) of this wheel (2.i) is exceeded: - limiting the target drive torque (M3S.i) and / or target drive speed (N3S.i) of the drive (3.i) driving the wheel (2.i) with the impermissible control deviation (dA) to a limit drive torque (M3G) and / or a limit drive speed (N3G) (ST5); and - determining whether the impermissible control deviation (dA) of the relevant wheel (2.i) differs from the control deviation (dA) of at least one other wheel (2.i) on the same axle (FA) driven by the same drive (3.i) (ST5a), In the case where it is known that the wheels (2.i) of a certain axle (FA) have different adjustment deviations (dA) on each side, an external brake request signal (SB) is generated by the drive control unit (10) and the external brake request signal is output to the brake control unit (20), and based on the external brake request signal, the service brake (7.i) at least at the wheel (2.i) of the relevant axle (FA) with the higher adjustment deviation (dA) is actuated, In this case, the limit drive torque (M3G) and / or the limit drive speed (N3G) is determined or adjusted as a function of the braking torque (MB.i) applied by the actuated service brake (7.i).

2. The method according to claim 1, characterized in that To know or read: - the actual slip (s2I.i) of the respective wheel (2.i), and / or - the actual speed (N2I.i, N3I.i) of the respective wheel (2.i) or the respective drive (3.i), and / or - the actual speed (v2I.i, v3I.i) of the respective wheel (2.i) or the respective drive (3.i), As the actual wheel dynamics parameter (GI.i).

3. The method according to claim 2, characterized in that The actual wheel speed (N2I.i) of the respective wheel (2.i) is determined or read as an actual wheel dynamics variable (GI.i), wherein the actual wheel speed (2NI.i) is measured by a wheel speed sensor (5.i) at the respective wheel (2.i) or by a speed sensor (8) downstream of the output on each side of the differential (6).

4. The method according to any one of the preceding claims, characterized in that To know or read: - Slip threshold (sS.i), and / or - Speed ​​threshold (NS.i), and / or - velocity threshold (vT.i), as the threshold value (Ti) for the respective wheel (2.i).

5. The method according to any one of the preceding claims, characterized in that The actual wheel dynamics variables (GI.i) of the respective wheels (2.i) are determined or read out by the drive control unit (10) and / or by the brake control unit (20).

6. The method according to any one of the preceding claims, characterized in that A threshold value (Ti) for the respective wheel (2.i) is determined in the drive control unit (10) and / or in the brake control unit (20).

7. The method according to any one of the preceding claims, characterized in that The limit drive torque (M3G) and / or the limit drive speed (N3G) are determined or adjusted as a function of the braking torque (MB.i) applied by the actuated service brake (7.i) so that, due to the limitation of the target drive torque (M3S.i) and / or the target drive speed (N3S.i) of the drive (3.i) driving the wheel (2.i) with the inadmissible control deviation (dA) in combination with the braking torque (MB.i) applied to the same wheel (2.i), the actual wheel dynamics variable (GI.i) of the respective wheel (2.i) falls below the threshold value (Ti) again and / or the admissible control deviation (dA) of the respective wheel (2.i) reappears.

8. The method according to any one of the preceding claims, characterized in that The brake request signal (SB) is transmitted from the drive control unit (10) to the brake control unit (20) via a data connection (15), in particular a CAN data bus (15a).

9. The method according to any one of the preceding claims, characterized in that In the event of an inadmissible control deviation (dA) of the wheel (2.i) driven by the drive (3.i), First, the target drive torque (M3S.i) and / or the target drive speed (N3S.i) of the drive (3.i) driving the wheel (2.i) with the impermissible control deviation (dA) is limited to a limit drive torque (M3G) and / or a limit drive speed (N3G) (ST5), and Then, in the case where it is known that the wheels (2.i) of a certain axle (FA) have different adjustment deviations (dA) on each side, an external braking request signal (SB) is generated by the drive control unit (10) and the external braking request signal is output to the brake control unit (20), based on the external braking request signal, at least the service brake (7.i) at the wheel (2.i) of the relevant axle (FA) with the higher adjustment deviation (dA) is actuated, and then, depending on the braking torque (MB.i) applied by the actuated service brake (7.i), the limit driving torque (M3G) and / or the limit driving speed (N3G) are adjusted.

10. A drive control unit (10) for a vehicle (1), in particular for carrying out the method according to any one of the preceding claims, the drive control unit having an input interface (11) and an output interface (12), wherein: The drive control unit (10) is designed to generate a target drive torque (M3S.i) and / or a target drive speed (N3S.i) as a function of a drive request (AD) and output it to at least one electric drive (3.i) of the vehicle (1) via the output interface (12), wherein the drive control unit (10) is further designed to: - knowing or reading the vehicle speed (v1) of the vehicle (1) via the input interface (11); - determining or reading at least one actual wheel dynamics variable (GI.i) via the input interface (11), which characterizes the rotational behavior of an individual wheel (2.i) of the vehicle (1); - determining or reading out via the input interface (11) a threshold value (Ti) of the respective actual wheel dynamics variable (GI.i) assigned to the wheel (2.i); - if a control deviation (dA) between an actual wheel dynamics variable (GI.i) of a wheel (2.i) and a threshold value (Ti) assigned to the same wheel (2.i) is known and an inadmissible control deviation (dA) exists for a wheel (2.i) driven by a drive (3.i), in particular if the threshold value (Ti) for this wheel (2.i) is exceeded: - limiting the generated and outputted target drive torque (M3S.i) and / or the generated and outputted target drive speed (N3S.i) of the drive (3.i) which drives the wheels (2.i) with an impermissible control deviation (dA) to a limit drive torque (M3G) and / or a limit drive speed (N3G); and - determining whether the impermissible control deviation (dA) of the relevant wheel (2.i) differs from the control deviation (dA) of at least one other wheel (2.i) on the same axle (FA) driven by the same drive (3.i), The drive control unit (10) is designed to generate an external braking request signal (SB) and output the external braking request signal via the output interface (12) when it is learned that the wheels (2.i) of a certain axle (FA) have different adjustment deviations (dA) on each side, so that based on the external braking request signal, the service brake (7.i) at least at the wheel (2.i) of the relevant axle (FA) with the higher adjustment deviation (dA) can be controlled. The drive control unit (10) is designed to determine or adjust the limit drive torque (M3G) and / or the limit drive speed (N3G) as a function of the braking torque (MB.i) applied by the actuated service brake (7.i).

11. The drive control unit (10) according to claim 10, characterized in that The drive control unit (10) is designed to: - actuating the electric drive (3.i) at each wheel (2.i) in a wheel-specific drive mode (AR); and - in an axle-specific drive mode (AA), actuating at least one electric drive (3.i) that jointly drives wheels (2.i) of at least one axle (FA) of the vehicle (1).

12. A vehicle (1) having wheels (2.i), a drive control unit (10) according to claim 10 or 11, and a brake control unit (20) connected thereto in a signal-conducting manner, for carrying out the method according to claim 1.

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