Method for controlling a vehicle, drive control unit and vehicle

Abstract

The invention relates to a method for controlling a vehicle comprising at least one electric drive (3.i) for driving wheels (2.i), wherein a drive control unit (10) is designed to generate a target drive torque and / or a target drive rotation speed and to output them to the relevant drive (3.i), comprising the following steps: - determining a vehicle speed (v1); - determining an actual wheel dynamics variable which characterizes the rotational behaviour of an individual wheel; - determining threshold values associated with the wheels (2.i); - determining a control deviation between the actual wheel dynamics variable and the threshold value and, if an impermissible control deviation is present: - limiting the target drive torque and / or the target drive rotation speed for the wheel (2.i) with the impermissible control deviation, wherein, if control deviations for the wheels (2.i) of a vehicle axle which are different on different sides are determined, an external brake request signal is generated and output by the drive control unit, the service brake on the wheel (2.i) with the higher control deviation being actuated on the basis of the external brake request signal, wherein the limit drive torque and / or the limit drive rotation speed are / is specified or adjusted depending on the braking torque applied by the actuated service brakes (7.i).

Description

[0001] Method for controlling a vehicle, drive control unit and vehicle

[0002] The invention relates to a method for controlling a vehicle, a drive control unit for carrying out the method and a vehicle with the drive control unit.

[0003] To ensure vehicle stability, excessive wheel slip (drive slip) resulting from excessive drive torque for the given friction coefficient of the surface must be limited when the vehicle is accelerating or moving off. This limitation must be achieved in a way that is suitable for generating not only propulsion but also the necessary lateral force. This requires a highly dynamic and precise limitation of the drive torque generated by the respective drive system.

[0004] In the case of wheel-individual electric drives, the drive at the respective slipping wheel is generally the only one capable of regulating wheel slip individually, for example, by limiting the requested target drive torque in a slip control loop by a drive control unit. For central drives that electrically drive the vehicle's wheels on each axle, traction control (ASR) is often implemented in the electronic braking 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 an axle-by-axle limit for the target drive torque of these wheels. It sends this limit to the drive control unit for axle-based output of correspondingly limited target drive torques for the wheels of the respective vehicle axle.If the wheels on this vehicle axle still exhibit different slip behavior, wheel-specific braking interventions can optionally be performed using the service brakes of the electronic braking system. This is carried out by the slip control loop implemented in the brake control unit as part of the traction control (ASR). However, the dynamics of such control for central drives using wheel-specific braking interventions are generally limited due to the control implemented in the brake control unit of the electronic braking system. In comparison, with wheel-specific electric drives, control to a specific wheel slip takes place directly via the drive control unit (by limiting the target drive torque) with the highest possible dynamics.

[0005] Based on this, the object of the present invention is to provide a method for controlling a vehicle with which safe, dynamic operation of the vehicle can be ensured in a simple manner. A further object of the invention is to provide a drive control unit and a vehicle.

[0006] The above-mentioned objects are achieved according to the invention by a method, a drive control unit, and a vehicle according to the independent claims. The subclaims describe preferred developments.

[0007] Thus, according to the invention, a method for controlling a vehicle is provided, comprising a drive system, wherein the drive system has a drive control unit and at least one electric drive for driving wheels of the vehicle individually or individually, wherein the drive control unit is designed to generate a desired drive torque and / or a desired drive speed as a function of a drive requirement and to output it to the respective drive, and a braking system, wherein the braking system has a brake control unit and service brakes for braking the wheels of the vehicle individually, comprising at least the following steps:

[0008] Reading or determining a vehicle speed;

[0009] Reading in or determining at least one actual wheel dynamics variable that characterizes the rotational behavior of an individual wheel;

[0010] Reading in or determining the threshold values ​​assigned to the wheels for the respective actual wheel dynamics variable;

[0011] Determining a control deviation between the actual wheel dynamics variable of a wheel and the threshold value assigned to the same wheel, and in the event that an inadmissible control deviation exists for the wheel driven by a drive, in particular if the threshold value for this wheel is exceeded:

[0012] Limiting the target drive torque and / or the target drive speed for the electric drive with which the wheel with the inadmissible control deviation is driven to a limit drive torque and / or a limit drive speed, and

[0013] Determining whether the inadmissible control deviation for the wheel in question differs from a control deviation for at least one other wheel on the same vehicle axle that is driven by the same electric drive, in particular a central electric drive (central drive), wherein, in the event that different control deviations are determined for the wheels of a vehicle axle on each side, an external brake request signal is generated by the drive control unit and output to the brake control unit, on the basis of which the service brake is activated at least on the wheel of the vehicle axle in question for which a higher control deviation exists, wherein the limit drive torque and / or the limit drive speed is determined or adjusted depending on the braking torque applied by the controlled service brakes,so that the combination of the braking interventions and the limitation of the drive torque results in a permissible control deviation for the respective wheel while maintaining the respective threshold value.

[0014] This advantageously recognizes that additional braking on one of the wheels of a vehicle axle can be accompanied by increased drive torque on another wheel of the same vehicle axle. This is because the additional braking reduces the limitation of the drive effect, which, in the case of central drives, is noticeable by an increase in the drive effect on the other, non-braked wheel. Overall, propulsion is thus increased while simultaneously maintaining the threshold values ​​for the rotational behavior of the wheels.

[0015] Preferably, it is further provided that at least one actual wheel dynamics variable is determined or read in: an actual slip of the respective wheel and / or an actual rotational speed of the respective wheel or of the respective drive and / or an actual speed of the respective wheel or of the respective drive.

[0016] In this way, the rotational behavior of each wheel can be observed in different ways, with the brake control unit and / or the drive control unit being able to determine these variables and easily provide them for further processing. Dual determination and provision also advantageously allows for plausibility checks of the values.

[0017] Preferably, it is further provided that the actual wheel speeds of the respective wheel are determined or read as the actual wheel dynamics variable, with the actual wheel speeds being measured via a wheel speed sensor on the respective wheel and / or via a speed sensor behind the side outputs of a differential on the respective vehicle axle. This allows the rotational behavior of the wheels to be determined in the form of wheel speeds in different ways, with double detection also allowing plausibility checks. The respective actual wheel dynamics variable can then be determined or calculated from the wheel speeds.

[0018] Preferably, it is further provided that the following is determined or read in as a threshold value for the respective wheel: a slip threshold value and / or a speed threshold value and / or a speed threshold value.

[0019] Depending on which actual wheel dynamics variable is being considered, a respective threshold value can also be assigned, the exceedance of which can then be checked for each individual wheel in order to detect an inadmissible deviation in the wheel rotation behavior.

[0020] It is preferably further provided that the actual wheel dynamics variable for the respective wheel is determined or read in by the drive control unit and / or by the brake control unit and / or the threshold values ​​for the respective wheel are determined in the drive control unit and / or in the brake control unit. Consequently, the determination of the rotational behavior of the wheels can be recorded and the threshold values ​​can be set in the drive system itself, which minimizes the transmission paths and thus makes the control, i.e. the limitation of the drive power and the setting of the wheel-individual braking effect, faster, since this control is carried out in the drive system or the drive control unit. Since the braking system orHowever, if the brake control unit sets threshold values ​​for the self-determined wheel rotation behavior, for example, for stability control and other braking functions within the braking system, these determined actual values ​​and threshold values ​​can also be transferred to the drive control unit, thereby saving additional computing and processing effort. Furthermore, plausibility checks can be performed by comparing a rotation behavior or threshold value determined by the drive system with that of the braking system.

[0021] Preferably, it can further be provided that the limit drive torque and / or the limit drive speed is set or adjusted as a function of the braking torque applied by the controlled service brakes in such a way that, due to the limitation of the target drive torque and / or the target drive speed for the drive with which the wheel with the impermissible control deviation is driven, in combination with the application of the braking torque to the same wheel, the actual wheel dynamics variable of the respective wheel falls below the threshold value again and / or a permissible control deviation is again established for the respective wheel. Advantageously, a braking effect and a driving effect are therefore applied to one wheel, which together ensure permissible rotational behavior of the respective wheel, so that optimal propulsion is achieved simultaneously for this driving effect alone at the other wheel of the same vehicle axle.

[0022] Preferably, it is further provided that the brake request signal is 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 fast data transmission, so that in the event of a braking effect being applied, a quick and reliable intervention at the respective wheel is achieved. Preferably, it is further provided that, in the event that an impermissible control deviation exists for the wheel driven by a drive, the target drive torque and / or the target drive speed for the drive with which the wheel with the impermissible control deviation is driven is first limited to a limit drive torque and / or a limit drive speed. Subsequently, in the event that different control deviations are determined for the wheels of a vehicle axle,an external brake request signal is generated by the drive control unit and output to the brake control unit, on the basis of which the service brake is activated at least on the wheel of the relevant vehicle axle for which a higher control deviation exists, whereupon the limit drive torque and / or the limit drive speed is then adjusted depending on the braking torque applied by the controlled service brakes.

[0023] Therefore, the drive power is first reduced to "defuse" the impermissible rotational behavior. Only then is the braking effect on the respective wheel built up, and the drive power is increased again by adjusting the limit drive torque or the limit drive speed. This means that the faster control loop in the drive control unit is used first to correct the unsafe condition, and only then is the slower control loop in the brake control unit activated. The safe condition, i.e., permissible rotational behavior, is given higher priority than improved propulsion.

[0024] In principle, however, it would also be possible to first control the respective service brake individually on each side and only then or at the same time limit the drive power by limiting the target drive torque or the target drive speed.

[0025] According to the invention, a drive control unit for a vehicle is also provided, in particular for carrying out the method according to the invention, with input interfaces and output interfaces, 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 to output it to at least one electric drive of the vehicle via the output interfaces, wherein the drive control unit is further designed to: determine a vehicle speed of the vehicle or read it in via the input interface; at least one actual wheel dynamics variable that characterizes the rotational behavior of an individual wheel of the vehicle,to determine or read in via the input interface; to determine threshold values ​​assigned to the wheels for the respective actual wheel dynamics variable or read them in via the input interface; to determine a control deviation between the actual wheel dynamics variable of a wheel and the threshold value assigned to the same wheel, and in the event that an inadmissible control deviation exists for the wheel driven by a drive, in particular if the threshold value for this wheel is exceeded: to limit the generated and output target drive torque and / or the generated and output target drive speed for the drive with which the wheel with the inadmissible control deviation is driven to a limit drive torque and / or a limit drive speed, and to determine whether the inadmissible control deviation for the wheel in question differs from a control deviation for at least one other wheel on the same vehicle axle,which is driven by the same drive, wherein the drive control unit is designed to generate an external brake request signal and output it via the output interface in the event that different control deviations are determined for the wheels of a vehicle axle on each side, such that on this basis a service brake can be activated at least on that wheel of the vehicle axle in question for which a higher control deviation exists, wherein the drive control unit is designed to set or adapt the limit drive torque and / or the limit drive speed depending on the braking torque applied by the controlled service brakes.

[0026] Preferably, it is additionally provided that the drive control unit is configured to control electric drives on the individual wheels in a wheel-specific drive mode, and in an axle-specific drive mode, which is preferred for the method according to the invention, to control at least one electric drive that jointly drives the wheels of at least one vehicle axle. Thus, the drive control unit can be operated accordingly in different modes.

[0027] The invention is explained in more detail below with reference to the accompanying drawings. They show:

[0028] Fig. 1 a, 1 b a schematic view of a vehicle; and

[0029] Fig. 2 is a flow chart of the method according to the invention.

[0030] Figure 1 a shows a vehicle 1 with wheels 2.i (i = 1, 2, 3, 4), where each wheel 2.i can be driven individually via an electric drive 3.i (i = 1, 2, 3, 4), for example via an electric motor. Fig. 1 b, on the other hand, shows a vehicle 1 in which the wheels 2.i of only one vehicle axle FA, here the rear axle HA as an example, are driven jointly via a central electric drive 3.0 (central drive), distributed via a differential 6. In a comparable way, an electric drive (not shown) assigned to the front axle VA can also be provided. Depending on the type of drive, the vehicle 1 or the wheels 2.i can be electrically driven individually for each wheel or individually for each axle.

[0031] In such a 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, which generates drive control signals S3.i (i=0,1,2,3,4) and outputs them via an output interface 12 to the respective drives 3.i in order to accelerate the vehicle 1 according to a manually or automatically specified drive requirement AD on a roadway 4. In the drive control signals S3.i, desired drive torques M3S.i and / or desired drive speeds N3S.i for the respective i. electric drive 3.i can be encoded, which the latter then implements accordingly for each wheel or axle. The drive control unit 10 further comprises one or more input interfaces 11, via which

[0032] - a vehicle speed v1 of vehicle 1 relative to the roadway 4, and

[0033] - Actual wheel speeds N2l.i of the individual wheels 2.i, and / or

[0034] - Actual wheel circumferential speeds v2l.i of the individual wheels 2.i, and / or

[0035] - Actual drive speeds N3l.i of the individual drives 3.i can be read in. Accordingly, information about the speed of the entire vehicle 1 is read in, and additionally, information about the rotational behavior or drive behavior of the individual wheels 2.i is read in for each wheel or axle.

[0036] The vehicle speed v1 can, for example, be provided by a brake control unit 20 of the electronic braking system 15 (EBS), which determines it in any desired way. The actual wheel speed N2l.i of the i. wheel 2.i can be measured via a wheel speed sensor 5.i on the i. wheel 2.i, and the actual drive speeds N3l.i of the i. electric drive 3.i can be measured via an incremental encoder or via a resolver within the respective i. drive 3.i. It is assumed that the actual wheel speeds N2l.i of the i. wheel 2.i correspond to the actual drive speeds N3l.i of the i. drive 3.i that drives the i. Wheel 2.i drives, or a fixed relationship exists, so that the actual wheel speeds N2l.i of the respective wheel 2.i can be derived from the actual drive speeds N3l.i of the drive 3.i assigned to this wheel 2.i via a fixed relationship, e.g., a gear ratio constant. Alternatively, the actual wheel speeds N2l.i of the i. wheel 2.ii in the embodiment according to Fig. 1 b also by speed sensors 8, which are arranged side by side behind outputs of the differential 6.

[0037] The actual wheel speeds N2l.i and / or the actual wheel circumferential speeds v2l.i of the individual wheels 2.i that can be calculated from them are normally already available within the framework of a control system implemented in the brake control unit 20, in particular ABS control, and can be transmitted to the central drive control unit 10, for example, via a corresponding data connection 15, for example a CAN bus 15a. 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 on the individual wheels 2.i, for example via a Y-connector, and receive the actual wheel speeds N2l.i itself (analog / digitally) via these connections.

[0038] With this structure, the method for controlling the vehicle 1 shown as an example in Fig. 2 can be implemented as follows:

[0039] In a first step ST1, the vehicle speed v1 is read in and in a second step ST2 the wheel-individual (slip-affected) rotational behavior or drive behavior of the individual wheels 2.i, whereby for this purpose the actual wheel dynamics variables Gl.i relating to the i. wheel 2.i, for the wheel-individual drive type AR the actual drive speeds N3l.i and / or the actual drive speeds v3l.i of the drives 3.i that can be calculated therefrom and / or for the axle-individual drive type AA (central drive) the actual wheel speeds N2l.i and / or the actual wheel circumferential speeds v2l.i of the individual wheels 2.i are read in or determined, as described above. In the case of the wheel-individual drive type AR, the actual wheel speeds N2l.i and / or the actual wheel circumferential speeds v2l.i of the individual wheels 2.i, which are the same or between which there is a fixed, constant relationship, can be used as redundancy or for plausibility purposes.

[0040] As further actual wheel dynamics variables Gl.i, the actual slip s2l.i for the individual wheels 2.i can also be determined, regardless of the drive type AA, AR. The actual slip s2l.i for the respective wheel 2.i is obtained, for example, as a percentage or as an absolute value from the actual wheel speeds N2l.i for the respective wheel 2.i (or the actual drive speeds N3l.i for the respective drive 3.i) and the vehicle speed v1. The actual slip s2l.i characterizes the speed difference between the road speed (vehicle speed v1) and the actual wheel circumferential speed v2l.i of the respective wheel 2.i, which results from the actual wheel speeds N2l.i and which can also be derived from the actual drive speed v3l.i for the respective drive 3.i of the respective wheel 2.i.

[0041] In a third step ST3, a threshold value Ti is read or determined for each wheel 2.i, which can be a slip threshold value s2T.i and / or a speed threshold value NT.i and / or a speed threshold value vT.i. These threshold values ​​Ti; s2T.i; NT.i, vT.i indicate

[0042] - which actual slip s2l.i for the i. wheel 2.i (slip threshold s2T.i) or

[0043] - which actual wheel speed N2l.i for the i. wheel 2.i or actual drive speed N3l.i for the i. drive 3.i on the i. wheel 2.i (speed threshold NT.i) or

[0044] - which actual wheel circumferential speeds v2l.i for the i. wheel 2.i or actual drive speed v3l.i for the i. drive 3.i of the i. wheel 2.i (speed threshold value vT.i) are permissible with regard to a dynamically unproblematic operation of vehicle 1, whereby this may also depend on the situation.

[0045] The respective threshold value 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, as part of the stability control implemented therein. The brake control unit 20 then transmits the respective threshold value Ti; s2T.i; NT.i, vT.i to the drive control unit 10 via the data connection 15, for example, the CAN bus 15a, and the respective input interface 11.

[0046] In a fourth step ST4, a wheel-specific (for wheel-specific drive type AR) or axle-specific (for axle-specific drive type AA) control deviation dA, i.e., a slip control deviation dsA and / or speed control deviation dNA and / or velocity control deviation dvA, is determined over time t. The control deviation dA indicates the difference between the respective actual wheel dynamics variable Gl.i and the threshold value Ti of the same variable, for each wheel or axle.

[0047] The slip control deviation dsA therefore indicates the difference between the actual slip s2l.i of the respective wheel 2.i and the respective slip threshold value s2T.i (wheel-individual) or between the actual slip s2l.i of the wheels 2.i of the respective vehicle axle FA (usually the higher actual slip s2l.i of the wheels 2.i of the respective vehicle axle FA (“Select-High”) or as an average value) and the respective slip threshold values ​​s2T.i for these wheels 2.i (e.g. “Select-High” or as an average value) (axle-individual). The speed control deviation dNA accordingly indicates the difference between the actual wheel speeds N2l.i of the respective wheel 2.i or the actual drive speeds N3I.I for the respective drive 3.i and the respective speed threshold value NT.i (wheel-individual) or between the actual wheel speeds N2l.i of the wheels 2.i or the actual drive speeds N3l.i of the drives 3.i of the respective vehicle axle FA (e.g."Select-High" or as an average value) and the respective speed threshold values ​​NT.i for these wheels 2.i (e.g. "Select-High" or as an average value) (axle-individual). The speed control deviation dvA accordingly indicates the difference between the actual wheel circumferential speeds v2l.i of the respective wheel 2.i or the actual drive speeds v3l.i for the respective drive 3.i and the respective speed threshold value vT.i (wheel-individual) or between the actual wheel circumferential speeds v2l.i of the wheels 2.i or the actual drive speed v3l.i of the drives 3.i of the respective vehicle axle FA (e.g. "Select-High" or as an average value) and the respective speed threshold values ​​vT.i for these wheels 2.i (e.g. "Select-High" or as an average value) (axle-individual).

[0048] If an inadmissible control deviation dA, i.e. slip control deviation dsA and / or speed control deviation dNA and / or velocity control deviation dvA is determined for at least one wheel 2.i, which results, for example, in the respective threshold values ​​Ti; s2T.i; NT.i, vT.i being exceeded, the drives 3.i of this at least one wheel 2.i are controlled in a fifth step ST5 with no more than a specified limit drive torque M3G or with no more than a specified limit drive speed N3G. For the wheels 2.i slipping excessively, the target drive torques M3S.i and / or target drive speeds N3S.i transmitted via the respective drive control signal S3.i are therefore limited. With the wheel-specific drive type AR, this limitation is applied wheel by wheel and with the axle-specific drive type AA, it is applied axle by axle.

[0049] By limiting the target drive torques M3S.i and / or target drive speeds N3S.i for the respective drives 3.i, the actual slip s2l.i or the actual wheel speed N2l.i or the actual drive speed N3l.i or the actual wheel circumferential speed v2l.i or the actual drive speed v3l.i at the respective affected wheels 2.i or drives 3.i are also limited accordingly or adjusted in such a way that a permissible slip control deviation dsA and / or speed control deviation dNA and / or speed control deviation dvA is again achieved. The respective wheel 2.i experiencing drive slip is thus "caught" again.

[0050] In the case of an axle-specific drive type AA, in a sub-step ST5a, the actual wheel speeds N2l.i provided by the wheel speed sensors 5.i are additionally monitored to determine whether, before or after the above-mentioned limitation of the target drive torques M3S.i and / or target drive speeds N3S.i for the relevant central electric drive 3.0 and the relevant vehicle axle FA, there are different rotational behaviors of the respective wheels 2.i on each side. For example, it is determined that before or after the above-mentioned limitation of the target drive torques M3S.i and / or target drive speeds N3S.i, an inadmissible control deviation dA for the respective actual wheel dynamics variable G l only exists for one wheel 2.i of this driven vehicle axle FA.i is present (or side-by-side different control deviations dA), an (external) brake request signal SB is generated by the drive control unit 10 and output 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.

[0051] The brake request signal SB then encodes a side-specific control of service brakes 7.i of vehicle 1. The brake request signal SB is generated as a function of the then existing control deviation dA of the respective actual wheel dynamics variable Gl.i for the respective wheel 2.i of the respective vehicle axle FA in such a way that a service brake 7.i assigned to this wheel 2.i is subjected to a specific target brake pressure pS in order to generate a specific braking torque MB.i at this wheel 2.i. The target brake pressure pS or the resulting braking torque MB.i are set in such a way that the respective threshold value Ti for this wheel 2.i is again maintained in conjunction with the limitation of the target drive torques M3S.i and / or target drive speeds N3S.i for the respective central electric drive 3.0.

[0052] An overdriven wheel 2.i of a vehicle axle FA is therefore no longer "caught" solely by limiting the target drive torques M3S.i and / or target drive speeds N3S.i for the relevant central electric drive 3.0, but additionally by braking the respective wheel 2.i on each side. This means that the limitation of the target drive torques M3S.i and / or target drive speeds N3S.i for the relevant central electric drive 3.0 no longer has to be as severe, since part of the impermissible rotational behavior of a wheel 2.i is corrected via the respective service brake 7.i.

[0053] The limit drive torque M3G or the limit drive speed N3G for the central electric drive 3.0 can therefore be selected higher in coordination with the brake request signal SB or the target brake pressure pS or the resulting brake torque MB.i, either initially (when a brake torque MB.i is already in effect) or in a subsequent adjustment (when the brake torque MB.i is only subsequently applied). With a central drive, this results in the other wheel 2.i of this vehicle axle FA being driven with a higher target drive torque M3S.i (compared to the case without braking intervention) (due to the less severe limitation). It is therefore possible that a high drive torque can still be transmitted via the other wheel 2.i for which there is no impermissible control deviation dA or a lower impermissible control deviation dA than the other wheel 2.i of the vehicle axle FA.This improves the propulsion of the vehicle 1, particularly under p-split conditions, ie when different friction values ​​occur on the road surface 4 on each side.

[0054] Preferably, in sub-step ST5a, it is generally provided that under p-split conditions, which can be detected by a side-by-side different rotational behavior, the wheel 2.i of a vehicle axle FA for which the lower control deviation dA exists is "caught" again only by limiting the target drive torques M3S.i and / or target drive speeds N3S.i for the relevant central electric drive 3.0 (threshold Ti is again maintained). The other wheel 2.i of this vehicle axle FA with the higher control deviation dA is then additionally "caught" again by a side-specific braking intervention as described.

[0055] In summary, the limit drive torque M3G or the limit drive speed N3G for the central electric drive 3.0 is set in coordination with the brake request signal SB or the target brake pressure pS or the resulting brake torque MB.i for the respective wheel 2.i in such a way that the greatest possible propulsion is enabled for the wheel 2.i of a vehicle axle FA with the lower (or no) control deviation dA. The following options are particularly conceivable for implementation:

[0056] If a side-by-side different rotational behavior of the respective wheels 2.i of a vehicle axle FA is detected, or if a side-by-side different control deviation dA is present, the brake request signal SB is first generated and output by the drive control unit 10 in order to achieve individual braking on the wheel 2.i of a vehicle axle FA with the higher control deviation dA. Only subsequently does a limitation of the drive behavior take place, or a determination of the limit drive torque M3G or the limit drive speed N3G takes place depending on the then-acting brake torque MB.i. Since the brake control loop is normally less dynamic, the limitation of the drive behavior and thus the elimination of the impermissible control deviation dA is delayed.

[0057] To optimize this, the drive behavior can first be limited or the limit drive torque M3G or the limit drive speed N3G can be defined depending on the existing control deviation dA (e.g. "Select-High"), which can be done with very high control dynamics. This limitation can then be subsequently adjusted when the target brake pressure pS or the resulting brake torque MB.i for the respective wheel 2.i with the higher control deviation dA is built up subsequently or simultaneously. The limitation is thus removed, which has the advantage that the inadmissible control deviation dA is initially corrected highly dynamically and then the propulsion is optimized in a higher-level brake control, which occurs somewhat more slowly.

[0058] In this way, a superimposed (slower) slip control loop can be accessed via the brake control unit 10 and the wheel-individually acting service brakes 7.i, which supplements the highly dynamic slip control loop underlying the drive control unit 10 and the limitation of the target drive torques M3S.i and / or target drive speeds N3S.i in order to improve performance even with a non-wheel-individually axle-individually drive type AA. Reference symbol (part of the description)

[0059] I Vehicle

[0060] 2.1 Wheels (i=1,2,3,4)

[0061] 3.1 electric drive (i=0,1,2,3,4)

[0062] 4 lane

[0063] 5.1 Wheel speed sensor on the i. Wheel 2.i (i=1,2,3,4)

[0064] 6 Differential

[0065] 7.1 Service brake on the i. wheel 2.i

[0066] 8 Speed ​​sensor

[0067] 9 Drive system

[0068] 10 Drive control unit

[0069] II Input interface

[0070] 12 Output interface

[0071] 15 Braking system

[0072] 20 Brake control unit

[0073] AA axle-specific drive type

[0074] AD drive requirement

[0075] AR wheel-specific drive type dA control deviation dNA speed control deviation dvA speed control deviation dsA slip control deviation

[0076] FA vehicle axle

[0077] Eq.i Actual wheel dynamics value for the i. wheel 2.i (i=1,2,3,4)

[0078] HA rear axle

[0079] M3S.i Target drive torque for the i. drive 3.i (i=0, 1, 2, 3, 4)

[0080] MB.i braking torque at the i. Wheel (i=1,2,3,4)

[0081] N2l.i Actual wheel speed of the i. Wheel 2.i (i=1,2,3,4)

[0082] N3S.i Target input speed for the i. drive 3.i (i=0, 1, 2, 3, 4)

[0083] N3l.i Actual input speed of the i. drive 3.i (i=1,2,3,4)

[0084] NT.i Speed ​​threshold for the i. wheel 2.i pS Target brake pressure s2l.i Actual slip of the i. wheel 2.i s2T.i Slip threshold for the i. wheel 2.1

[0085] S3.I Drive control signal (i=0,1,2,3,4)

[0086] Ti threshold value for the i. wheel 2.i

[0087] VA front axle v1 vehicle speed v2l.i actual wheel circumferential speed of the i. wheel 2.i (i=1,2,3,4) v3l.i actual drive speed of the i. drive 2.i (i=1,2,3,4) vT.i speed threshold for the i. wheel 2.i

Claims

Patent claims 1. A method for controlling a vehicle (1), comprising a drive system (9), wherein the drive system (9) has a drive control unit (10) and at least one electric drive (3.i) for driving wheels (2.i) of the vehicle (1) individually or individually, wherein the drive control unit (10) is designed to generate a desired drive torque (M3S.i) and / or a desired drive speed (N3S.i) depending on a drive request (AD) and to output it to the respective drive (3.i), and a braking system (15), wherein the braking system (15) has a brake control unit (20) and service brakes (7.i) for braking the wheels (2.i) of the vehicle (1) individually, comprising at least the following steps: Reading in or determining a vehicle speed (v1) of the vehicle (1) (ST1); Reading in or determining at least one actual wheel dynamics variable (Eq.i) that characterizes the rotational behavior of an individual wheel (2.i) (ST2); Reading in or determining the threshold values ​​(Ti) assigned to the wheels (2.i) for the respective actual wheel dynamics variable (Gl.i) (ST3); Determining a control deviation (dA) between the actual wheel dynamics variable (Gl.i) of a wheel (2.i) and the threshold value (Ti) assigned to the same wheel (2.i) (ST4), and in the event that an inadmissible control deviation (dA) exists for the 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 target drive torque (M3S.i) and / or the target drive speed (N3S.i) for the drive (3.i) with which the wheel (2.i) is driven with the inadmissible control deviation (dA) to a limit drive torque (M3G) and / or a limit drive speed (N3G) (ST5), and Determining whether the inadmissible control deviation (dA) for the wheel (2.i) in question differs from a control deviation (dA) for at least one other wheel (2.i) on the same vehicle axle (FA) that is driven by the same drive (3.i) (ST5a), wherein, in the event that different control deviations (dA) are determined for the wheels (2.i) of a vehicle axle (FA), an external brake request signal (SB) is generated by the drive control unit (10) and output to the brake control unit (20), on the basis of which the service brake (7.1) is controlled at least at that wheel (2.i) of the relevant vehicle axle (FA) for which a higher control deviation (dA) exists, wherein 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 controlled service brakes (7.i).

2. Method according to claim 1, characterized in that the following is determined or read in as the actual wheel dynamics variable (Gl.i): an actual slip (s2l.i) of the respective wheel (2.i) and / or an actual speed (N2l.i, N3l.i) of the respective wheel (2.i) or of the respective drive (3.i) and / or an actual speed (v2l.i, v3l.i) of the respective wheel (2.i) or of the respective drive (3.i).

3. Method according to claim 2, characterized in that actual wheel speeds (N2l.i) of the respective wheel (2.i) are determined or read in as the actual wheel dynamics variable (Gl.i), wherein the actual wheel speeds (2N li) are determined via a wheel speed sensor (5.1) at the respective wheel (2.i) or via a speed sensor (8) behind side outputs of a differential (6).

4. Method according to one of the preceding claims, characterized in that the following is determined or read in as the threshold value (Ti) for the respective wheel (2.i): a slip threshold value (sS.i) and / or a speed threshold value (NS.i) and / or a speed threshold value (vT.i).

5. Method according to one of the preceding claims, characterized in that the actual wheel dynamics variable (Gl.i) for the respective wheel (2.i) is determined or read in by the drive control unit (10) and / or by the brake control unit (20).

6. Method according to one of the preceding claims, characterized in that the 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. Method according to one of the preceding claims, characterized in that 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 controlled service brakes (7.i) in such a way that, due to the limitation of the target drive torque (M3S.i) and / or the target drive speed (N3S.i) for the drive (3.i) with which the wheel (2.i) is driven with the impermissible control deviation (dA), in combination with the application of the braking torque (MB.i) to the same wheel (2.i), the actual wheel dynamics variable (Gl.i) of the respective wheel (2.i) falls below the threshold value (Ti) again and / or a permissible control deviation (dA) is again established for the respective wheel (2.i).

8. Method according to 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. Method according to one of the preceding claims, characterized in that, in the event that an impermissible control deviation (dA) exists for the wheel (2.i) driven by a drive (3.i), firstly the target drive torque (M3S.i) and / or the target drive speed (N3S.i) for that drive (3.i) with which the wheel (2.i) with the impermissible control deviation (dA) is driven is limited to a limit drive torque (M3G) and / or a limit drive speed (N3G) (ST5), and then, in the event that different control deviations (dA) are determined for the wheels (2.i) of a vehicle axle (FA), an external brake request signal (SB) is generated by the drive control unit (10) and output to the brake control unit (20), on the basis of which the service brake (7.i) is applied at least on that wheel (2.i) the relevant vehicle axle (FA) is controlled for which a higher control deviation (dA) exists, whereupon the limit drive torque (M3G) and / or the limit drive speed (N3G) is adjusted as a function of the braking torque (MB.i) applied by the controlled service brakes (7.i).

10. Drive control unit (10) for a vehicle (1), in particular for carrying out a method according to one of the preceding claims, with input interfaces (11) and output interfaces (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 to output it to at least one electric drive (3.i) of the vehicle (1) via the output interfaces (12), wherein the drive control unit (10) is further designed to: determine a vehicle speed (v1) of the vehicle (1) or read it in via the input interface (11); determine at least one actual wheel dynamics variable (Gl.i) that characterizes the rotational behavior of an individual wheel (2.i) of the vehicle (1) or read it in via the input interface (11); threshold values ​​(Ti) assigned to the wheels (2.i) for the respective actual wheel dynamics variable (Eq.i) to determine or read in via the input interface (11); to determine a control deviation (dA) between the actual wheel dynamics variable (Gl.i) of a wheel (2.i) and the threshold value (Ti) assigned to the same wheel (2.i), and in the event that an inadmissible control deviation (dA) exists for the wheel (2.i) driven by a drive (3.i), in particular if the threshold value (Ti) for this wheel (2.i) is exceeded: to limit the generated and output target drive torque (M3S.i) and / or the generated and output target drive speed (N3S.i) for that drive (3.i) with which the wheel (2.i) is driven with the inadmissible control deviation (dA) to a limit drive torque (M3G) and / or a limit drive speed (N3G), and to determine whether the inadmissible control deviation (dA) for the wheel (2.i) in question differs from a control deviation (dA) for at least one further wheel (2.i) on the same vehicle axle (FA) which is driven by the same drive (3.i), wherein the drive control unit (10) is designed, in the event that side-by-side different control deviations (dA) are determined for the wheels (2.i) of a vehicle axle (FA), to generate an external brake request signal (SB) and to output it via the output interface (12) in such a way that, on the basis of this signal, a service brake (7.i) can be controlled at least on that wheel (2.i) of the relevant vehicle axle (FA) for which a higher control deviation is detected. (dA), wherein the drive control unit (10) is designed to set or adapt the limit drive torque (M3G) and / or the limit drive speed (N3G) as a function of the braking torque (MB.i) applied by the controlled service brakes (7.i).

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

12. Vehicle (1) with wheels (2.i), a drive control unit (10) according to one of claims 10 or 11 and a brake control unit (20) connected thereto in a signal-conducting manner for carrying out a method according to one of claims 1 to 9.

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