EP0590234A1 - Method and apparatus for eliminating the inclination of a bogie with wheel units - Google Patents

Abstract

The invention relates to a method and apparatus for eliminating the inclination of a rail vehicle bogie (4, 5) which has wheel units and is provided with a plurality of individual wheels (11, 12, 21, 22). According to the invention, the detected wheel speeds (n11, n12, n21, n22) of the bogie with wheel units (4, 5) are added to one another in crisscross fashion, these total wheel speeds (ns1, ns2) which are formed are logically combined to form a total-difference actual wheel speed value (g) which represents the actual degree of inclination of the bogie (4) and this actual value (g) of the degree of inclination is adjusted to a predeterminable desired value (g') of the degree of inclination. In this way, the degree of inclination of the bogie (4, 5) with wheel units is detected and compensated without additional sensor equipment irrespective of how said inclination was caused, as a result of which optimum running behaviour in straight sections of track and in bends is achieved to the same degree. <IMAGE>

Description

The invention relates to a method and a device for eliminating an inclination of a wheel block bogie provided with a plurality of individual wheels.

Rail vehicles consist of a body and chassis. The undercarriage has two tasks: it guides the vehicle in the track channel of the track and it has to protect the body from bumps.

The tracking is ideal if the vehicle follows the middle of the track exactly. The tracking behavior of the undercarriage approaches ideal tracking, the faster deviations from the track axis are corrected.

• dem Abbau eines Querversatzes und
• dem Abbau einer Schrägstellung im Gleis.

The tracking behavior can be quickly assessed using just two variables:

• the removal of a transverse offset and
• the removal of an inclined position in the track.

Forces are required to move them sideways, a turning moment is required to remove the inclined position. The latter in turn requires forces that deliver the desired torque with a lever arm around a suitable pivot point or as a pair of forces.

Forces arise in the wheel / rail contact area that can be used for guiding. Depending on the physical effect, two fundamentally different types of forces can be distinguished.

There are frictional forces when the wheel slides transversely or longitudinally at the wheel contact point relative to the rail. The product out Relative speed and force is a loss of power. It makes itself felt as a tracking resistance and is converted into heat and wear on the wheel and rail in the wheel / rail contact. The rolling noise is also closely related.

In the essay "Aspects of Guidance", printed in the magazine "ZEV-Glas.Ann. 114 (1990), No. 1/2, pages 24 to 29, various guidance principles are presented and examined with regard to the guidance behavior.

The "wheel block" guidance principle is known from this article. In the wheel block, two individual wheels are used, which are not arranged next to each other, but one behind the other. The individual wheels arranged one behind the other prove to be almost ideal for correcting inclined positions. The inclined wheel block acts on both wheels because of the same slip angle δ equally large traction lateral forces. With regard to the pivot point, they compensate for the turning moments that result. From this point of view, the wheel block is always in an indifferent equilibrium position. From any position in the phase diagram of the wheel block, the transverse deflections and an inclination are very quickly reduced to values around zero. The wheel block removes the transverse offset as well as inclined positions with lateral profile forces and is therefore wear-free. The wheel block guidance principle would come very close to the ideal if there were no longitudinal frictional forces, as is the case with driven wheels.

A rail vehicle is known from EP 0 374 290 A1, which comprises a predeterminable number of individual wheels on both sides along the longitudinal axis of the vehicle, which can be pivoted by steering. A steering error-free steering of each individual wheel in all curve areas is achieved in that a rail profile measuring device is provided which measures the deviation of a vehicle axis from the profile of the rail and which, depending on measured deviations, generates a steering signal for each individual wheel independently of the other. This means that each individual wheel is always correctly steered in any curve position so that tracking errors can no longer occur.

When cornering, the wheel planes should ideally be tangent to the rail. Non-constrained rolling of the wheels is still only guaranteed if the rolling radii of the wheels are relatively equal to the arc lengths of the two rails. This enables a transverse offset. The necessary difference in the rolling radius due to the taper of the wheel profiles of both wheels results from the known rolling condition of the wheel set. If the necessary difference in the rolling radius is greater than the possible difference due to the wheel profile due to the track guidance, the wheels can no longer roll without constraint. This means that the wheel on the outside of the curve turns too slowly, the inside of the curve on the outside too quickly. In relation to the vertical axis, the different frictional longitudinal forces create a turning moment which turns the undercarriage, also called the bogie, out of the curve. The flange always starts up when the bogie is inclined, i.e. no longer runs parallel to the track or no longer runs tangentially to the track in curves. The counter torque can only be applied by the frictional shear forces or by a start of the wheel flange with corresponding wear.

The invention is based on the object of specifying a method and a device for eliminating an inclined position of a wheel block bogie.

This object is achieved by the features specified in claims 1 and 2.

By linking two wheel speeds of two diagonally opposed individual wheels of the chassis to a sum signal and linking them to a sum difference actual speed value, one obtains information about the actual inclination of the bogie when driving straight ahead or cornering. This sum differential speed actual value is compared with a predetermined sum differential speed setpoint, which can be set according to a predeterminable tracking quality criterion. A control variable is generated from the control deviation between the total differential speed setpoint and actual value, which is added or subtracted to or from a drive lever setpoint or from a common braking force setpoint. This provides a setpoint for a control and regulating device or a control device of each wheel block of the driving or running gear, with which the resulting inclination of the bogie (driving or running bogie) is eliminated when cornering or driving straight ahead, thereby reducing the running properties of the bogie Chassis significantly improved.

An ideal tracking behavior is thus achieved, i.e. the wheel block bogie can be guided in the ideal track without using additional encoders. It is irrelevant whether the vehicle is driving in a curve or on a straight line. It is also irrelevant which interferences, e.g. constantly changing rail condition, which could cause skewing, because such active tracking according to the invention determines the skew indirectly via the wheel speeds and corrects them regardless of their cause.

A device according to the invention is defined by the features listed in claims 3 and 5, respectively. This device consists of adders, comparators, a sign member and a controller, which makes the structure very simple and inexpensive.

In a further embodiment of the device, an adaptation element is connected between the first comparator and the sign element, the second input of which is linked to an output of an averager. As a result, the actual sum of the differential speed is related to a chassis speed.

The higher the speed of the undercarriage and thus the vehicle speed, the better the evaluability of the total difference speed actual value. This is particularly helpful for tracking at high speeds and thus reducing wear.

The inventive method for skew detection can also be used without using the drive or braking forces. For example, it would be possible for the bogie to be rotatable relative to the car body by means of an actuating mechanism, so that a manipulated variable for such an actuating mechanism can be obtained from the actual inclination value determined as a function of a predetermined inclination setpoint value. This manipulated variable could also be used in an actuating mechanism for steering the wheel sets relative to the bogie. The special feature of the inventive method for skew detection is that its skew can be determined as a function of the speeds of the individual wheels of a bogie without using additional sensors.

Figur 1

zeigt schematisch ein angetriebenens Radblock-Drehgestell mit einem Stellmoment, den Kraftschlußlängskräften und den Querkräften, in

Figur 2

ist ein Blockschaltbild einer Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens bei einem angetriebenen Radblock-Drehgestells dargestellt, die

Figur 3

veranschaulicht ein Blockschaltbild einer Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens bei einem antriebslosen Radblock-Drehgestell und die

Figur 4

zeigt ein Blockschaltbild einer vorteilhaften Vorrichtung nach Figur 2.

To further explain the method according to the invention for eliminating an inclined position of a wheel block bogie provided with a plurality of individual wheels, reference is made to the drawing, in which several embodiments are illustrated schematically.

Figure 1

shows schematically a driven wheel block bogie with an actuating torque, the frictional longitudinal forces and the transverse forces, in

Figure 2

is a block diagram of an apparatus for performing the method according to the invention in a driven wheel block bogie, the

Figure 3

illustrates a block diagram of an apparatus for performing the method according to the invention in a non-driven wheel block bogie and the

Figure 4

shows a block diagram of an advantageous device according to FIG.

wobei

Fx..

Kraftschlußlängskräfte (Antriebskraft)

Fy..

Querkräfte

b

halber Abstand der Radaufstandspunkte

a

halber Achsabstand

R

Abrollradius

M

Stellmoment um vertikale Achse

η

Querversatz

δ

Schrägstellungwinkel

γ

Neigungswinkel des Radprofils.

The sketch of a bogie 4 shown in FIG. 1 serves to explain the forces and lever arms acting on the bogie 4. This bogie 4 is not equipped with two conventional wheel sets (rigid axles) but with four individual wheels 11, 12, 21 and 22. Each individual wheel 11, 12, 21 and 22 is driven by a motor via a gear, the gear and a motor not being shown for reasons of clarity. The actuating torque M is decisive for the position of the trolley 4 in the track. This moment, which is related to the vertical axis through the pivot, results in:

$\text{M = (Fx12 + Fx22-Fx11-Fx21) b + (Fy12 + Fy21-Fy11-Fy22) a,}$

in which

Fx ..

Longitudinal force (driving force)

Fy ..

Lateral forces

b

half the distance between the wheel contact points

a

half the center distance

R

Roll radius

M

Actuating torque around the vertical axis

η

Cross offset

δ

Tilt angle

γ

Tilt angle of the wheel profile.

The transverse forces Fyij depend on the weight of the vehicle to be absorbed by the wheel, the angle of inclination of the wheel profile at the respective contact point, the position of the bogie in relation to the longitudinal axis of the track and the sliding angle of the wheel / rail. When the wheel set is displaced transversely in the track, the lateral forces essentially only change when the angle of inclination of the wheel profile changes. With the proposed wheel profile, however, this angle is constant in the possible running range. As a result, the lateral forces remain constant and are the same size on all wheels as long as there is no contact with the wheel flange. The lateral forces in the specified moment equation thus cancel each other out. The longitudinal frictional forces Fxij are the driving forces of the vehicle and can be actively influenced via the control device. The simplified calculation equation for the actuating torque is sufficient for further consideration:

$\text{M = b (Fx12 + Fx22-Fx11-Fx21).}$

The respective force Fxij is positive if the wheel circumferential speed at the wheel contact point is greater than the vehicle speed. Accordingly, the force becomes zero at the same speed or negative if the wheel peripheral speed is less than the vehicle speed. Longitudinal forces are always to be seen in connection with a wheel / rail slip.

If the bogie 4 and thus the wheels 11, 12, 21 and 22 are moved obliquely to the wheel plane at an angle δ, then they slide with a transverse slip relative to the rail. The relative movement is countered by a force-fit side force Fy caused by the wheel / rail force-fit. This leads to undesirable friction, which is converted into heat, wear and noise. The inclination can even lead to the flange turning and will only thereby preventing a turning moment M from occurring when the bogie 4 is deflected obliquely about the vertical axis, which causes a return movement into a position parallel to the direction of travel or parallel to the track, ie the inclined position δ becomes zero again.

A transverse offset η alone produces neither wear nor noise and is therefore without any disadvantages in terms of tracking. Due to the taper of the wheel profiles, however, there are different rolling radii and, depending on the drive concept selected, differences arise in the longitudinal force forces, which creates a turning moment M.

A start of the wheel flange can only be prevented by the fact that, once the wheel set or bogie has been deflected, an actuating torque is generated which causes a return movement to the central position.

FIG. 2 shows a block diagram of a device for carrying out the method according to the invention for eliminating an inclined position of a chassis 4 provided with a plurality of individual wheels 11, 12, 21 and 22, also called a driven bogie. A drive motor is assigned to each individual wheel 11, 12, 21 and 22, which is not shown in more detail for reasons of clarity. In this chassis 4, the individual wheels 11, 12, 21 and 22 are fed in blocks. For this purpose, the traction motors of the individual wheels 11 and 21 are fed by a first actuator, for example a converter, in particular a pulse converter, and the traction motors of the individual wheels 12 and 22 are fed by a second actuator, for example a converter, in particular in the pulse converter. These converters are also not shown in detail for reasons of clarity. There is thus the possibility of operating the left wheel block 1 with a different torque and speed than the right wheel block 2, which is particularly advantageous for non-constrained cornering.

The drive torques m * 1 and m * 2 of the left and right-hand motors are set to approximately the same size with the aid of two control and regulating devices 6 and 8. If one impresses exactly the same motor torques m * 1 and m * 2 on both sides of the bogie 4 by means of these two control and regulating devices 6 and 8, the theoretical assumption of the same rolling radii on all four wheels 11, 12 should be assumed , 21 and 22 expect the bogie 4 to run straight ahead.

A tracking control 10 is superimposed on the torque control of these traction motors of the individual wheels 11, 12, 21 and 22 of the undercarriage 4 which are fed in blocks of blocks, whereby an inclined position is recognized at any arc radius and by suitable control interventions on the traction motors of the individual wheels 11, 12, 21 and 22 which are fed in blocks of blocks the frictional longitudinal forces are controlled so that a return movement from the determined inclination takes place.

This superimposed tracking control 10 consists of two adders 14 and 16 on the input side, which are linked on the output side to a first comparator 18. The adder 14 sums the wheel speeds n11 and n22 of two diagonally opposite individual wheels 11 and 22 of the chassis 4, the adder 16 sums the wheel speeds n12 and n21 of the other two diagonally opposite single wheels 12 and 21 of this chassis 4. At the output of adder 14 there is a first total speed ns1 and at the output of adder 16 there is a second total speed ns2. By means of the following first comparator 18, a total difference rotational speed actual value g is formed, which represents a measure of the inclination of the running gear 4 in the track. Thus, the total difference speed actual value g is also referred to as the actual inclination value g. The output of the first comparator 18 is provided with a sign element 20, which gives the ascertained sum difference speed actual value g or the inclined actual value g with a sign s provides. This sign s is equal to +1 when driving backwards, braking forwards (with a negative drive lever setpoint m *) and -1 when driving forward, backwards braking (with a positive drive lever setpoint m *). This signed inclined actual value sg is fed to a first further adder 24, at the second input of which an inclined nominal value g * is present. So that the determined inclination of the running gear 4 in the track can be reversed, the determined inclination actual value g must normally be set to zero. In this case, therefore, the slanted setpoint g * is zero. A manipulated variable Δm * is generated from the sum signal present at the further adder 24 by means of a controller 26, in particular a proportional-integral-differential controller (PID controller). This manipulated variable Δm * is fed to an adder 28 and a subtractor 30, at the first inputs of which there is a drive lever setpoint m *, also called a torque setpoint. The output of the adder 28 is with the control and regulating device 8 for the actuator of the motors of the individual wheels 12 and 22 of the right wheel block 2 and the output of the subtractor 30 is with the control and regulating device 6 for the actuator of the motors of the individual wheels 11 and 21 of the left wheel block 1 connected. At the output of the adder 28 or the subtractor 30 there is a torque setpoint m * 2 or m * 1, which changes the frictional longitudinal forces via the converter in such a way that the motors of the individual wheels 12 and 22 of the right wheel block 2 are slightly more and the motors of the individual wheels 11 and 21 of the left wheel block 1 make a little less torque. This creates a turning moment that counteracts the inclined position, whereby the bogie 4 rotates out of the inclined position until it has again reached the ideal guidance parallel to the track. If this state is reached, the actual inclination value g is zero and the control process is ended.

gleich einem vorgebbaren Schrägstellungs-Sollwert g* ist. Im Normalfall ist dieser vorgebbare Schrägstellungs-Sollwert g* gleich Null, er kann jedoch auch von Null verschieden sein (Optimierung).By linking the four speeds of the individual wheels of the undercarriage 4 according to the invention, one is recognized Inclination without additional encoders using a track quality criterion according to the invention. The ideal track is given when the four wheel speeds are cross-linked according to the track quality criterion according to the invention

$\text{g = (n12 + n21) - (n11 + n22) (track quality criterion)}$

is equal to a predefinable inclination setpoint g *. Normally, this predeterminable inclination setpoint g * is zero, but it can also be different from zero (optimization).

Let us assume that the bogie 4 is rotated clockwise in relation to the track direction, as in Figure 1, i.e. the inclination angle δ is positive. The rolling radii of the diagonally opposite wheels 12 and 21 are therefore larger than those of the other diagonally opposite wheels 11 and 22. The measured engine speeds n11, n12, n21 and n22 are linked according to the tracking quality criterion. An actual inclination value g less than zero is obtained. With a bogie 4 rotated counterclockwise, the actual inclination value g would be greater than zero. As already mentioned, depending on this determined actual inclination value g, a turning moment is generated on the bogie 4, which counteracts the inclination.

The higher the speed and thus the vehicle speed n, the better the evaluation of the actual inclination value g. This is particularly helpful for tracking at high speeds and thus reducing wear.

The track quality criterion applies to any arc radius r, since the speed difference between the inner wheel block and the outer wheel block stands out due to the diagonal addition of the speeds.

The same applies to the transverse offset η of the bogie 4: A pure transverse offset η from the middle of the track does not affect the guidance. With a transverse offset η to the right, for example, the speeds n11 and n21 of the left wheel block 1 increase, while the speeds n12 and n22 of the right wheel block 2 decrease. Similar to cornering, the speed differences stand out as desired due to the diagonal addition of the speeds in the track quality criterion. The track quality criterion also provides the correct result here g.

FIG. 3 shows a block diagram of a device for carrying out the method according to the invention for eliminating an inclined position of a drive 5 provided with a plurality of individual wheels 11, 12, 21 and 22, also called a bogie or a non-powered bogie. Each individual wheel 11, 12, 21 and 22 is assigned a speed measuring device, as in FIG. 2, which is not shown in detail for reasons of clarity. In addition, each wheel block 1 or 2 is assigned a braking device, which are also not shown in detail. These braking devices are operated by means of control devices 7 and 9. The control device 7 acts on the braking device of the individual wheels 11 and 21 of the left wheel block 1 and the control device 9 on the braking device of the individual wheels 21 and 22 of the right wheel block 2. The control devices 7 and 9 are each supplied with a braking torque m * _B 1 and m * _B 2, which are each the same as a common braking force setpoint m * _B when the bogie 5 has ideal tracking behavior. A track control 10 according to FIG. 2 is superimposed on this brake control. Depending on the measured wheel speeds n11, n12, n21 and n22, this tracking control 10 generates an actual inclination value g, which is regulated to a predetermined inclination setpoint value g * (normally zero), in which a braking manipulated variable Δm * _B on the one hand added to the braking force torque m * _B 2 of a wheel block 2 and on the other hand subtracted from the braking force torque m * _B 1 of the other wheel block 1. The sign S of the sign member 20 is equal to +1 when driving forward (in the direction of the arrow) and -1 when driving backwards (against the direction of the arrow). Otherwise, this tracking control 10 functions in exactly the same way as with a motor bogie 4 according to FIG. 2.

If the vehicle is in the "driving" or "coasting" state, the necessary turning moment for a bogie can be achieved by lightly "braking" the corresponding wheel block 1 or 2. The tracking control 10 is independent of the braking system. The braking system can be based on any physical principles, as long as each wheel block 1 and 2 has its own braking device.

In principle, this tracking method can also be used if only a single wheel is braked on each side of the bogie.

The principle can also be applied to motor bogies if the electric drive unit has failed and the mechanical brake (replacement brake) is activated instead.

FIG. 4 shows a block diagram of an advantageous embodiment of the device according to FIGS. 2 and 3. The difference from the device according to FIG. 2 is that an adaptation element 32 is connected between this first comparator 18 and the sign element 20, the second input of which has an output an averager 34 is linked. The determined wheel speeds n11, n12, n21 and n22 are present at the first inputs of this mean value generator 34 and the numerical value of the number a of the individual wheels 11, 12, 21 and 22 of the chassis 4 is present at the second input. This averager 34 sums up the upcoming wheel speeds n11, n12, n21 and n22 and divides this sum by the number a of the individual wheels 11, 12, 21 and 22 of the Chassis 4, so that a chassis speed n is present at the output. The determined actual inclination value g is related to the chassis speed n by means of the adaptation element 32. As a result, the superimposed tracking control 10 becomes independent of the speed of the bogie 4.

The superimposed tracking control 10, also called active tracking, enables without additional sensors, such as Joint angle encoder, optimal running behavior in straight lines and in bends alike. An inclination of the bogie 4 or 5 can practically always be recognized and corrected, regardless of how this is caused. For example, a tilting of the bogie 4 as a result of one-sided sliding and spinning processes can be detected and corrected.

Different wheel diameters between the right and left side of the bogie 4 or 5 are irrelevant. The wheel diameters on each side must be the same, but this is guaranteed by the parallel connection of the traction motors.

This active guidance is an ideal solution to the guidance problem. The rolling condition is always fulfilled. The bogie 4 or 5 can be guided in the ideal track without additional encoders. It is irrelevant whether the vehicle is driving in a curve or on a straight line. It is also irrelevant which interferences, e.g. constantly changing rail conditions, which could cause skewing, because the active tracking determines the skew and corrects it regardless of its cause.

The described method for eliminating an inclined position of a chassis 4 described at the outset can also be applied to bogies whose traction motors are each fed by a converter. In addition, the method described can also be applied to bogies which can be rotated relative to the car body by means of an adjusting mechanism are arranged. Furthermore, this described method can be applied to a bogie in which the wheels thereof can be rotated relative to the bogie by means of an adjusting mechanism.

Claims (7)

Method for eliminating an inclined position of a chassis (4) of a rail vehicle provided with a plurality of individual wheels (11, 12, 21, 22), the traction motors of which are fed in blocks by means of two control and regulating devices (6, 8), the wheel speeds (n11 , n12, n21, n22) two wheel speeds (n11, n22 or n12, n21) of two diagonally opposite individual wheels (11, 22 or 12, 21) of the chassis (4) are summed up to a total speed (ns1, ns2) , of which a sum difference actual value (g) is formed, which is compared depending on a direction signal (S) with a sum difference speed setpoint (g *), whereby depending on the control difference generated, a manipulated variable (Δm *) is generated by Adding or subtracting a drive lever setpoint (m *) forms a torque setpoint (m * 1 or m * 2) for each wheel block (1 or 2). Method for eliminating an inclined position of a running gear (5) of a rail vehicle provided with a plurality of individual wheels (11, 12, 21, 22), the braking devices of which are controlled by wheel blocks by means of two control devices (7, 9), the wheel speeds (n11, n12, n21, n22) each two wheel speeds (n11, n22 or n12, n21) of two diagonally opposite individual wheels (11,22 or 12,21) of the drive (5) are summed up to a total speed (ns1, ns2), of which A sum difference actual value (g) is formed, which is compared depending on a direction signal (S) with a sum difference speed setpoint (g *), whereby depending on the control difference generated, a manipulated variable (Δm * _B ) is generated, which by addition or Subtraction of a common braking force setpoint (m * _B ) forms a braking force setpoint (m * _B 1 or m * _B 2) for each wheel block (1 or 2). Method according to Claim 1 or 2, in which the sum difference actual value (g) is related to a chassis speed (n), this chassis speed (n) being divided from the sum of the wheel speeds (n11, n12, n21, n22) is determined by the number (a) of the wheels (11, 12, 21, 22). Apparatus for carrying out the method according to claim 1 for a chassis (4) of a rail vehicle provided with a plurality of individual wheels (11, 12, 21, 22), the traction motors of which are fed by means of two control and regulating devices (6, 8) consisting of two wheel blocks Adders (14, 16), each with two measured wheel speeds (n11, n22 or  n21, n12) of two diagonally opposed single wheels (11, 22 or  Add 12,21) of the undercarriage (4) to a total speed (ns1, ns2), these adders (14, 16) being linked on the output side to a first comparator (18) which on the output side has an input of a sign element (20) a further adder (24) is linked, at the other input of which a summation differential speed setpoint (g *) is present, the output of this further adder (24) being connected via a controller (26) to an adder (28) and a subtractor (30) is at the first inputs of which a drive lever setpoint (m *) is present and the outputs of which are each linked to a control and regulating device (6, 8) of the chassis (4). Device for carrying out the method according to claim 2 for a running gear (5) of a rail vehicle provided with a plurality of individual wheels (11, 12, 21, 22), the braking devices of which are controlled by wheel blocks by means of two control devices (7, 9), consisting of two adders (14 , 16), each adding two measured wheel speeds (n11, n22 or n21, n12) of two diagonally opposed individual wheels (11, 22 or 12, 21) of the drive (5) to a total speed (ns1, ns2), these Adder (14, 16) on the output side are linked to a first comparator (18), which on the output side is linked via a sign element (20) to an input of a further adder (24), at the other input of which a summation differential speed setpoint (g *) is present, the output of this further adder (24) being connected via a controller (26) to an adder (28) and a subtractor (30), at the first inputs of which there is a common braking force setpoint (m * _B ) and the outputs of which are linked to a control device (7, 9) of the drive (5). Apparatus according to claim 3 or 5, in which an adaptation element (32) is connected between the first comparator (18) and the sign element (20), the second input of which is linked to an output of an averager (34). Apparatus according to claim 6, in which the measured wheel speeds (n11, 12, n21, n22) at the first inputs of the averager (34) and the number (a) of the individual wheels (11, 12, 21, 22) of the chassis at the second input (4 or 5) are pending.

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