EP4077078A1

EP4077078A1 - Anti-lock control method and anti-lock control system for a braking system of a vehicle

Info

Publication number: EP4077078A1
Application number: EP20817282.5A
Authority: EP
Inventors: Steffen Gerlach; Alexander Rodenberg; Michael Schomburg
Original assignee: ZF CV Systems Europe BV
Current assignee: ZF CV Systems Europe BV
Priority date: 2019-12-19
Filing date: 2020-12-01
Publication date: 2022-10-26
Also published as: US20220324453A1; CN114761290A; US11970169B2; DE102019135088A1; WO2021121956A1

Abstract

The invention relates to an anti-lock control method and control system for a braking system (6) of a vehicle (1), in particular an electro-pneumatic braking system (6) of a utility vehicle (1), comprising at least the following steps: if there is a braking request signal (S1), outputting a braking control signal (S2) and building a braking pressure (pb) by means of a braking means on a wheel brake (4) of a vehicle wheel (2); measuring a rotational speed (n) of the vehicle wheel (2) to be braked and determining a wheel slip (n) of the vehicle wheel (2); in the event of a first traction criterion (K1) being fulfilled or a locking tendency of the vehicle wheel (2), actuating a wheel drive device (3) and exerting a wheel drive torque (M2) on the vehicle wheel (2) in order to increase the wheel circumferential speed (v2) and to reduce the wheel slip (s) until a second traction criterion (K2) is fulfilled. In addition, preferably the braking force introduced into the wheel brake (4), e.g. the braking pressure (pb) introduced into the wheel brake (4), is controlled in a closed-loop manner according to the wheel slip (s), in particular by releasing the brake pressure (pb) when a first traction criterion (K1) is fulfilled.

Description

Anti-lock control method and anti-lock control system for a braking system of a vehicle

The invention relates to an anti-lock control method and an anti-lock control system for a braking system of a vehicle, in particular a pneumatic braking system of a commercial vehicle.

Anti-lock control systems and anti-lock control methods serve to reduce or limit the tendency of braked vehicle wheels to lock. When braking a vehicle wheel, a brake slip occurs because a wheel peripheral speed no longer corresponds to a vehicle speed.

Here, the brake slip can be described as the relative deviation of the wheel circumferential speed of the vehicle wheel compared to a frictionally running wheel on the ground; In the following, however, the brake slip is preferably the relative deviation of the wheel circumferential speed compared to the vehicle speed, which thus enables a calculation and evaluation independently of the direct contact with the ground. In the case of a wheel rolling frictionally on the ground, the peripheral speed of the wheel corresponds to the speed of the vehicle.

When braking, the braking force transferred from the vehicle wheel to the ground initially increases with the increasing brake slip. With higher brake slip, however, a tendency to lock occurs or the frictional connection reaches the frictional connection limit, whereupon the braking force exerted by the vehicle wheel on the roadway decreases, which is also referred to as the tendency to lock or the vehicle wheel to lock. In the case of fluid-actuated, i.e. pneumatic or hydraulic brake systems, when the tendency of a vehicle wheel to lock is detected, the brake pressure of the fluid-actuated wheel brake is generally reduced or fully released in anti-lock control methods, so that the vehicle wheel is swept away from the road again in accordance with the coefficient of friction of the ground thus the brake slip is reduced. Thus, the braking force exerted on the vehicle wheel can subsequently be increased again by increasing the applied brake pressure.

Depending on the coefficient of friction, long blocking times can occur; especially on black ice or snow, the coefficient of friction can be so low that the bike is hardly driven at first. During the blocking, no transverse force or lateral force can be transmitted from the wheel, so that the driving stability is reduced and there is no cornering. Also, by releasing the pressure medium, the brake pressure actually present in the wheel brake is initially only reduced with a delay due to the inertia of the working medium. In particular special with pneumatic wheel brakes, the brake pressure in the brake chamber via the connected brake valve, z. B. an ABS valve or electropneumatic relay valve, due to the inertia only degraded with an appropriate time delay. The compressed air can only escape according to the pressure conditions and flow cross-sections, so that a certain brake pressure is still applied despite the activation to release the brake.

Although in general z. B. the controlled braking force or the brake pressure can be adjusted by an axle load determination. In particular at a low coefficient of friction, however, a long locking time of the wheels can occur despite the axle load determination, since the braking force applied by the wheel brake to the vehicle cannot be transmitted as braking force exerted on the ground. In particular in the case of driven axles, which generally have a higher mass and a higher moment of inertia, the blocking time can thus be correspondingly long.

The invention is therefore based on the object of creating an anti-lock control method and an anti-lock control system which enable a high level of safety and good controllability of the vehicle with little effort.

This object is achieved by an anti-lock control method and an anti-lock control system according to the independent claims. The subclaims describe preferred developments. Furthermore, a driving tool is provided with the anti-lock control system according to the invention.

The anti-lock control method according to the invention can in particular be carried out with or using the anti-lock control system according to the invention; the anti-lock control system according to the invention is designed in particular to carry out the anti-lock control method according to the invention.

The invention is based on the idea of not only releasing the brake pressure when detecting the tendency to block or when the frictional connection limit is reached in order to enable a passive increase in the peripheral speed of the wheel through friction on the ground, but rather to actively drive the vehicle wheel in this phase, so that it gets back up to higher wheel speeds more quickly and thus reduces wheel slip. Thus, a wheel drive is preferably activated as a function of a first criterion when it is detected that the force slip limit has been reached or a tendency to lock. In the case of an electric wheel drive, for example, this can be a wheel hub motor, which enables rapid responsiveness in order to enable rapid acceleration in these control phases as well. Thus, the active wheel drive can take place in addition to releasing the brake pressure. In principle, however, the brake pressure can be fully or partially maintained if, for. B. due to the existing conditions, a change in the wheel pressure is recognized as too sluggish and would therefore take place with too great a time delay. Thus, in principle, z. B. only the wheel speed can be increased by active drive to reduce the brake slip.

Thus, with relatively little effort, especially already existing wheel hub motors, and a corresponding control, the tendency to lock can be limited in time and reduced in order to subsequently be able to increase the brake pressure again and achieve a higher braking force exerted by the vehicle wheel on the ground.

As a wheel brake, on the one hand, a pressure fluid-operated wheel brake, but also z. B. be a retarder brake vorgese hen as a wear-free brake. If at a retarder brake z. B. it is recognized that the braking force can not be varied quickly enough, z. B. the anti-lock control can be carried out entirely or completely by controlling the Radan drive.

Thus, according to the invention, the control of a drive on a vehicle wheel or an axle is advantageously included in the ABS control.

The control of the wheel drive can take place in accordance with the control of the wheel brakes or the applied braking force. As an alternative to this, the active wheel drive can also only be used to compensate for the braking force still exerted due to the inertia of the system.

In principle, the invention can be used with any pressure medium-actuated brake system, ie with a pneumatic or electropneumatic tables or with a hydraulic or electrohydraulic brake system.

The invention is explained below with reference to the accompanying drawings of some embodiments. Show it:

1 shows a schematic representation of a vehicle with an anti-lock control system according to an embodiment of the invention;

2 shows a diagram with the time representation of relevant parameters of an anti-lock control method in a conventional anti-lock control method;

3 shows a diagram corresponding to FIG. 2 of an anti-lock control method according to an embodiment of the invention;

4 shows a flow diagram of a method according to the invention.

Figure 1 shows a schematic representation of a vehicle 1 with an electric vehicle drive and four wheels 2, which are each driven via an electric wheel hub motor 3 as part of the electric vehicle drive, the electric wheel hub motor 3 being an individual wheel drive and advantageously also a recuperation, ie motor - Braking with recovery of part of the kinetic energy as electrical energy, allows. The electric vehicle drive can in principle be designed with or without a transmission. In principle, a hybrid drive with an internal combustion engine and additional wheel hub motors 3 can also be provided. The vehicle is in particular a utility vehicle. The vehicle can be a trailer vehicle.

In the vehicle 1, an electropneumatic brake system 6 is provided, advantageously as an electronic brake system (EBS), the one central brake control device 10 and for each vehicle wheel 2 a pressure medium-actuated - here pneumatic - wheel brake 4, wheel speed sensors 5 for measuring the wheel speeds n of the individual vehicle wheels 2 and for outputting wheel speed signals to the central brake control device 10, and generally a valve device for the pressure medium-actuated wheel brakes 4. According to the simplified representation in Figure 1, an electropneumatic valve device 9 is provided for each vehicle wheel 2, which is controlled by the central brake control device 10 via brake control signals S2 and can in particular be designed with an electropneumatic relay valve and ABS valves, which each time control a brake pressure pb to the respective vehicle wheel 2. Furthermore, the electropneumatic brake system 6 has pneumatic components (not shown here), in particular a special compressed air supply, and further pneumatic and possibly electro-pneumatic valves.

The central brake control device 10 can determine the axle loads of the axles from e.g. additionally provided axle load sensors or from the braking behavior over several braking operations and adjust the brake pressure pb to be set via the brake control signals S2 accordingly.

The vehicle 1 has a drive control device 12 and the electric wheel hub motors 3 as the drive device 8. Vehicle 1 also has components, not shown here, such as a battery and corresponding further elements. The central brake control device 10 and the central drive control device 12 are in data exchange with one another, as shown in FIG. 1; they can also be designed inte grated.

When a brake request signal S1 is input by, for example, the driver or an autonomous vehicle system such as a stability system such as FDR, ESP, a distance maintenance system such as ACC or an accident avoidance system, the central brake control device 10 starts a braking system. Process by outputting brake control signals S2 which, in the case of an EBS, are output to the wheel brakes 4, for example to electropneumatic relay valves for pneumatic control of the analog brake pressure pb. The wheel speeds n of the individual vehicle wheels 2 are determined via the respective wheel speed sensors 5 in order to carry out ABS regulation in the central brake control device 10.

With the ABS control, the respective wheel circumferential speed v2 is determined directly from the determined wheel speeds n, and from this a wheel circumferential acceleration is determined through time derivative, which represents a wheel circumferential deceleration in the case of a negative value. The wheel circumferential speed v2 is advantageously compared with an ABS reference speed vref, which is determined in a manner known per se over a longer period of time from the wheel speeds n and serves as a reference variable for the vehicle speed v1, which is generally not exactly known. A slip s of each individual vehicle wheel 2 can accordingly be determined from the difference.

Each vehicle wheel 2 can be driven independently of the other vehicle wheels 2 by the wheel hub motors 3. In the embodiment shown, the central drive control device 12 also sends drive control signals S3 to the respective wheel hub motors 3.

During braking, wheel slip s of the individual vehicle wheels 2 occurs, which depends in particular on the coefficient of friction m. With a lower coefficient of friction m, longer blocking times At of the individual vehicle wheels 2 can occur despite the axle load determination, since the braking force FB1 set in the individual wheel brakes 4 cannot be transferred to the road.

When a tendency to lock of a vehicle wheel 2 is determined, the central brake control device 10 regulates an anti-lock control method in order to keep the locking times At small. FIG. 2 shows a time sequence of a conventional anti-lock control method, which in principle can also be set in the brake system 6. At a point in time t0, a brake pressure pb is input into the respective wheel brake 4 via a brake control signal S2, so that the wheel speed n and thus also the wheel circumferential speed v2 decrease. When the wheel brake 4 is actuated, a basically permissible wheel slip s begins immediately, ie a wheel circumferential speed v2 shown in dashed lines in FIG. 2 drops compared to a vehicle speed v1 shown as a solid line. Correspondingly, a braking force FB2 transmitted from the vehicle wheel 2 to the road, which is shown in FIG. 2 as a dash-dotted line, increases and thus approaches a theoretically possible braking force FBth. The wheel slip s subsequently increases in such a way that the maximum of the transmitted braking force FB2 is reached at time t1 and the transmitted braking force FB2 subsequently decreases as the wheel slip increases, ie there is a tendency to lock or the vehicle wheel 2 is already locked. The central brake control device 10 detects this behavior via the measured wheel speeds n and releases the brake pressure in whole or in part with the conventional ABS, ie the brake control signal S2 reduces the set braking force FB1 by venting the wheel brake 4.

However, the compressed air can only escape in accordance with the pressure conditions and flow cross-sections, so that initially a corresponding braking force FB1 continues to be exerted on the vehicle wheel 2. Only when the braking force FB1 exerted on the vehicle wheel 2 has been reduced almost completely is the vehicle wheel 2 released sufficiently so that it is taken along and accelerated again via contact with the roadway - according to the coefficient of friction m - so that its wheel circumferential speed v2 decreases increases again at time t2, and here again vehicle speed v1 is reached at time t4. In contrast, the braking force FB2 transmitted to road 2 is correspondingly delayed in time and still falls at time t2, reached at time t3 a minimum or the value zero and subsequently increases again, so that the maximum transmitted braking force FB2 is then reached again at a point in time t1.

Since the braking force reduction is thus delayed, the vehicle wheel 2 only starts up again when the applied braking force FB1 has been reduced almost completely, so that the braking force can then be built up again. Thus, the theoretical braking force FBth cannot be applied over the entire period, even with a high coefficient of friction m.

FIG. 3 shows an anti-lock control method provided according to the invention with integration of the wheel drive, which is provided as an alternative to the ABS control method shown in FIG. 2 without an active wheel drive. According to the invention, it is basically possible to switch between the two ABS control methods of FIGS. 2 and 3; however, only the ABS control method with active wheel drive shown in FIG. 3 is advantageously used. During the braking process, the wheel hub motor 3 is switched on via a drive control signal S3, especially in phases with a tendency to lock, in order to quickly bring the vehicle wheel 2 back to a higher wheel speed n or wheel circumferential speed v2.

According to FIG. 3, the braking process begins again at time t0, in which a corresponding brake control signal S2 is output and the brake pressure pb in the wheel brake 4 is increased, so that the set braking force FB1 - not shown here - increases accordingly. Thus, the braking force FB2 transmitted to the roadway also increases, and the wheel circumferential speed v2 or the rotational speed n decreases as the braking effect begins.

In this case, a tendency of vehicle wheel 2 to lock is checked, e.g. by a first adhesion criterion K1, which

- According to a training described further here, the achievement of a indicates the first frictional connection limit ksg1 or the lower frictional connection limit and, for example, compares the determined wheel slip s with a first slip limit value sg1; ie first adhesion criterion K1: s> ^? sg1.

According to another embodiment, the first traction criterion K1 can also evaluate a tendency to lock of the vehicle wheel 2, for example as a comparison of the wheel circumference deceleration, ie the time derivative dv2 / dt of the wheel circumferential speed v2, with a deceleration limit value a2-ref; ie first adhesion criterion K1: | dv2 / dt | > ^? | a2-ref |.

According to FIG. 3, the first frictional connection criterion K1 is fulfilled at time t1, i.e. the wheel slip s becomes too great, so that a tendency to lock begins. Thus, the wheel hub motor 3 is controlled via a drive control signal S3 and, according to FIG. 3, is driven by a drive torque M2. Thus, according to FIG. 3 - in comparison to FIG. 2 - the blocking time At between times t1 and t2, ie At = t2-t1, can be kept small or even completely prevented, and in particular also the time span t3-t1, in which no braking force FB2 can be transmitted can be kept low.

Thus, the vehicle wheel 2 tending to lock is applied with the drive torque M2 so that it does not lock while the brake pressure pb and thus also the braking force FB1 exerted by the inertia of the working medium on the vehicle wheel 2 is still reduced. The braking force FB1 still pending on the vehicle wheel is thus compensated for by the drive torque M2, so that the vehicle wheel f2 accelerates more quickly and again reaches the vehicle speed v1 earlier at time t4, i.e. v2 = v1.

FIG. 3 again shows an idealized curve here by way of example, since in principle the vehicle speed v1, for example, cannot be reached in the control method either. Thus, in Figure 3 there is a periodic connection of the drive torque M2 during the anti-lock control method. If the brake pressure pb and thus the applied braking force FB1 is sufficiently reduced, the drive torque M2 is switched off and the brake pressure pb is increased again based on the reaction of the vehicle wheel 2.

Thus, shorter control phases are generated and, in particular, the braking force FB2 exerted, which is applied to the road by vehicle wheel 2, is increased overall on the one hand and is also kept relatively constant over time, as can be seen in FIG. 3.

In an embodiment modified from FIG. 3, the brake pressure pb and thus the applied braking force FB1 can also be maintained during the ABS control process, so that only the electric drive, i.e. here the wheel hub motor 3 controlled via the drive control signal S3, does the anti-lock control takes over. As a result, further time can be saved, since the electric drive can react significantly faster or more agile to the acceleration or deceleration of the vehicle than the pressure medium or working medium.

Thus, according to the invention, in particular between these three anti-lock control methods, ie the anti-lock control method without additional electrical drive according to FIG. 2, the anti-lock control method with electrical drive and control of the applied braking force FB1 according to FIG Compared to Figure 3 modified anti-lock control method with control of the drive torque M2 and without control of the braking force, can be switched, for example according to a switchover criterion K3, for example as a function of the coefficient of friction and / or the axle load. The braking process can be initiated as a driver braking process by inputting a driver braking signal S1 and / or by an autonomous braking system, for example by stability control, by braking individual vehicle wheels 2 when instability is detected as an electronic stability program, and also correspondingly with the autonomous braking system, for example a distance regulation or an accident avoidance procedure.

On the vehicle 1, for example, wheel hub motors 3 or another drive can also be provided on only one of the axles, so that only this axle according to FIG. 3 is controlled with an integrated wheel drive and the other axle is not driven and thus the conventional ABS - Control method according to Figure 2 is regulated.

According to Figure 1, the central brake control device 10 can be formed separately from the central drive control device 12, with a data connection, for. B. via a CAN bus. As an alternative to this, these two brake control devices 10, 12 can also be designed in combination.

Correspondingly, traction control can also be exercised by the two data-linked brake control devices or a combined brake control device 10, 12.

Instead of the pneumatic wheel brakes 4, a hydraulic brake system with hydraulic wheel brakes 4 can also be provided. Furthermore, a retarder can also be provided as the vehicle brakes, d. H. that the wear-free exercise of a braking effect takes place via a drive train, z. B. an internal combustion engine.

The method according to the invention is explained as follows with reference to the flow chart in FIG. 4:

After the start in step StO, a braking request signal S1 is present in step St1, e.g. B. due to a driver braking or also due to an autonomous system, e.g. B. a stability program such as ESC or FDR for selective braking of individual vehicle wheels 2, a distance maintenance system (ACC) or an accident avoidance system or a system for reducing the severity of an accident.

In step St2, the central brake control device 10 then outputs the brake control signal S2, d. H. here as an electrical control signal that is controlled via the valve device 9 as an analog pneumatic brake pressure pb to the wheel brake 4 of the relevant vehicle wheel 2, the pneumatic brake pressure pb corresponding to the desired braking force FB1 to be set in order to brake the vehicle wheel 2 accordingly.

During step St2, and also continuously thereafter, according to step St3, the wheel speed n of the vehicle wheel 2 is continuously determined via the speed sensor 5 and a wheel speed signal is output to the central control device 10.

In step St4, the central brake control device 10 determines an ABS reference speed (vref) from, in particular, a temporal behavior of all wheel speeds n of all vehicle wheels 2. Trailer vehicle as vehicle 1 also receive signals about a driving speed of the towing vehicle. In principle, however, ABS control systems can also autonomously form an ABS reference speed vref from the wheel speeds n alone through long-term temporal averaging and integration, which thus reproduces the vehicle speed v1. The central brake control device 10 also determines the wheel slip s of the vehicle wheels 2.

According to decision step St5, a check is made on the basis of the first frictional connection criterion K1 whether a frictional connection limit has been reached or whether the braked vehicle wheel 2 has a tendency to block. The criterion K1 can in particular correspond to a comparison of the determined wheel slip s with an upper slip limit value sg1, ie

K1: s> ^? sg1. According to another embodiment, the criterion K1 can be determined by comparing the wheel circumference deceleration, ie the time derivative dv2 / dt of the wheel circumferential speed v2, with a deceleration limit value a2-ref, ie based on the absolute values (oh ne Sign) by comparison:

K1: | dv2 / dt | > ^? | a2-ref |. For example, a2-ref = -15m / s ² . The delay limit value a2-ref is typically negative.

The first frictional connection criterion K1 defines the start of the anti-lock control method.

If K1 is not met, the method is reset according to branch n1, in particular before step St3. If, however, there is already a sufficient tendency to lock or the frictional connection limit has been reached, the anti-lock control method is subsequently started as an active intervention in accordance with branch y1 from step St6.

According to the above-mentioned embodiments, the applied braking force FB1 can be kept completely or partially constant from step St6 and the tendency to lock can be achieved solely by regulating the activated drive torque M2.

According to the alternative embodiment, both moments, d. H. the drive torque M2 and the braking torque or the set braking force FB1, regulated by, according to step St6, when the blocking tendency is detected, on the one hand, the braking force FB1 applied is reduced by first reducing the braking pressure pb applied to the wheel brake 4, e.g. B. by venting the wheel brake 4.

Furthermore, the drive torque M2 is introduced or a previously existing drive torque M2 is increased in order to drive the vehicle in this situation. to accelerate bike 2 so that it regains traction with the road. The wheel speed n is continuously determined as described above. Here, the wheel drive torque M2 can be changed as a function of the wheel slip s, in particular with an increase in the wheel drive torque M2 with increased wheel slip s and vice versa.

According to step St7, when it is determined that the lower frictional connection limit has been reached or the tendency to lock is again low, since the vehicle wheel 2 was again accelerated to a sufficient value close to the vehicle speed, a second frictional connection criterion K2 is met, which, for example, indicates that an upper frictional connection limit ksg2 has been reached, which is the same as or different from the lower (first) frictional connection limit ksg1, and the method is thus reset according to branch y2.

List of reference symbols (part of the description)

1 vehicle, especially commercial vehicle

2 vehicle wheel

3 wheel hub motor

4 wheel brake, in particular pneumatic brake 6 electropneumatic brake system, in particular EBS

7 Anti-lock brake control system

8 electric drive system

9 electro-pneumatic valve device

10 central brake control device 12 central drive control device a2-ref deceleration limit value

FB1 applied to the vehicle wheel 2 braking force

FB2 braking force exerted on the ground

FBth theoretically possible braking force

K1 first frictional connection criterion, reaching a first frictional connection limit

K2 second frictional connection criterion, reaching a second frictional connection limit, equal to or different from the first frictional connection limit

K3 switchover criterion ksg1 lower (first) frictional connection limit ksg2 upper (second) frictional connection limit

M2 wheel drive torque n wheel speed pb brake pressure s wheel slip

S1 brake request signal 52 Brake control signal

53 drive control signal sg1 slip limit value t1 point in time at which the maximum of the transmitted braking force FB2 is reached t2 point in time at which the wheel circumferential speed v2 increases again t3 point in time at which the transmitted braking force to road 2 increases again

Braking force FB2 reaches a minimum or the value zero at t4 point in time at which vehicle speed v1 is reached again.

At blocking time, time between t1 and t2 v1 vehicle speed v2 wheel circumferential speed dv2 / dt wheel circumferential deceleration vref reference speed of the ABS, measure for the vehicle speed v1

Claims

1.Anti-lock control method for a brake system (6) of a vehicle (1), in particular an electro-pneumatic brake system (6) of a commercial vehicle (1) or hydraulic brake system, with at least the following steps: when a brake request signal (S1) is present

Output of a brake control signal (S2) and

Build-up of a brake pressure (pb) by means of a braking device on a wheel brake (4) of a vehicle wheel (2) (St1, tO),

Measurement of a wheel speed (n) of the vehicle to be braked wheel (2) (St3) and

Determination of a wheel slip (s) and / or the wheel circumferential speed (v2) of the vehicle wheel (2) (St4), if a first adhesion criterion (K1) is met

Control of a wheel drive device (3) and exertion of a wheel drive torque (M2) on the vehicle wheel (2) to increase the wheel peripheral speed (v2) and to reduce the wheel slip (s) until a second frictional connection criterion is met ( K2).

2. Anti-lock control method according to claim 1, characterized in that when the second frictional connection criterion (K2) is met, in particular reduced or no tendency to lock, the wheel drive torque (M2) is reduced, preferably switched off.

3. Anti-lock control method according to one of the preceding claims, characterized in that a wheel drive device (3), for example an electric wheel hub motor (3), is controlled to exert a wheel drive torque (M2) on the vehicle wheel (2).

4. Anti-lock control method according to claim 3, characterized in that the wheel drive device (3) can be operated in a recuperation mode for at least partial recovery of kinetic energy.

5. Anti-lock control method according to one of the preceding claims, characterized in that the wheel drive torque (M2) is changed as a function of the wheel slip (s), in particular while increasing the wheel drive torque (M2) with increased wheel slip (s) and reduction of the wheel drive torque (M2) with reduced wheel slip (s)

6. Anti-lock control method according to one of the preceding claims, characterized in that the braking force (FB1) input into the wheel brake (4), for example the brake pressure (pb) input into the wheel brake (4), as a function of the wheel slip (s) is regulated.

7. Anti-lock control method according to claim 6, characterized in that when the first frictional connection criterion (K1) is met, e.g. when a lower frictional connection limit (Ksg1) is reached, the brake pressure (pb) is released, e.g. B. by venting the pneumatic wheel brake (3) via a Ventileinrich device (9), and when the second frictional connection criterion (K2) is met, e.g. reaching an upper frictional connection limit (Ksg2), the brake pressure (pb) is increased again, e.g. by Open the valve device (9).

8. Anti-lock control method according to claim 6 or claim 7, characterized in that the change in the drive torque (M2) and the change in the set braking force (FB1), in particular the controlled brake pressure (pb), are combined or synchronized.

9. Anti-lock control method according to one of claims 1 to 5, characterized in that only the input drive torque (M2) is controlled and the set braking force (FB1) is kept constant.

10. Anti-lock control method according to one of the preceding claims, characterized in that in the first frictional connection criterion (K1) the determined wheel slip (s) is compared with a first slip limit value (sg1) and the first frictional connection criterion (K1) is fulfilled when the determined wheel slip (s) exceeds the first slip limit value (sg1), and / or a tendency to lock of the vehicle wheel (2) is assessed and the first traction criterion (K1) is met if the tendency to lock of the vehicle wheel ( 2) is higher than a predefined limit value of the blocking tendency of the vehicle wheel (2), in particular in that in the first frictional connection criterion (K1) a wheel circumferential deceleration (dv2 / dt) formed by the temporal derivation of the wheel circumferential speed (v2) with a Deceleration limit value (a2-ref) is compared and the first traction criterion is met when the wheel circumferential deceleration (dv2 / dt) exceeds the deceleration limit value (a2-ref).

11.Antiblockier-control method according to one of the preceding claims, characterized in that, depending on a switching criterion (K3) between tween the anti-lock control under control of the wheel drive device (3) and exercise of a wheel drive torque (M2) and an anti-lock Control is switched without wheel drive.

12. Anti-lock control system (7) for anti-lock control of a vehicle wheel (2), the anti-lock control system (7) having the following: a central brake control device (10), a wheel brake (4) for exerting a controlled braking force (FB1 ) on the vehicle wheel (2) depending on one of the zentra len control device (10) output brake control signal (S2), a speed sensor (5) for measuring a speed (n) of the vehicle wheel (2) and output of a speed signal (n) to the brake control device (10), a wheel drive device (3) for receiving a drive control signal (s3) and exerting a wheel drive torque (M2) on the vehicle wheel (2), the central brake control device (10) from at least the determined wheel speed signals ( n) and an ABS reference speed (vref) formed from a temporal behavior, a wheel slip (s) is determined and evaluated, and when a first adhesion criterion (K1) or a tendency to lock of the vehicle wheel (2) is met, the wheel drive device (3 ) controls to exercise a wheel drive torque (M2), to reduce the wheel slip (s).

13. Anti-lock control system (7) according to claim 12, characterized in that it further comprises a central drive control device (12) for Ansteue tion of the wheel drive devices (3) of several vehicle wheels (2) with drive control signals (s3) , wherein the central drive control device (12) is in data connection or integrated with the central brake control device (10).

14. Anti-lock control system (7) according to claim 12 or 13, characterized in that the wheel drive device (3) is designed electrically, in particular as a wheel hub motor (3), preferably with recuperation.

15. Anti-lock control system (7) according to one of claims 12 to 14, characterized in that a pneumatic brake system, in particular an EBS with electropneumatic valve devices (9), is provided for controlling a pneumatic brake pressure (pb) in the wheel brakes (4) as a function of the brake control signal (S2) from the brake control device (10).