DE3825639C2 - Device for stabilizing motor vehicles when cornering - Google Patents

Description

The invention relates to a device for stabilizing of motor vehicles when cornering according to the preamble of Claim 1.

Such devices are used in motor vehicle construction, to irregular driving behavior such. B. determine slipping and counteract this by acting on the brakes.

US 3 910 647 shows such a device for controlled Reduction of brake pressures in the front and rear brake cylinders of a motor vehicle to prevent it from slipping when braking avoid. For this purpose, there is a steering lock sensor on the motor vehicle and three microwave Doppler radar sensors. The front Doppler sensors detect the true or actual forward and Cross speed, the rear sensor is the actual cross speed. The rear brake pressure is determined by a calculation or Control unit controlled, reduced by a fixed amount, if the rear actual transverse speed is greater than that Actual forward speed is. The front brake pressure will also reduced if the deviation of the measured from the lateral speed calculated from forward speed and steering angle is greater than the forward speed.

However, these measures are almost fully effective developed sliding or spinning process, because at a beginning Slipping away the rear cross speed and the front Drift are less than the forward speed. Moreover are not including the withdrawal of the driving force Slip control still influencing the steering angle and the single wheel drive or braking forces provided.

From DE 36 25 392 A1 a control system is known with which avoid skidding and / or drifting of a motor vehicle shall be. It uses a steering angle sensor as well as one Fiber gyroscope as an inertial sensor for measuring the angular velocity  of the vehicle around the vertical axis. Does this differ from the Angular velocity, which from the measured with the tachometer, d. H. apparent forward speed and the measured Steering angle has been calculated, the Vehicle detected. This is done by selective braking and / or accelerating and / or correcting the steering angle counteracted at least one wheel, so that its target and Actual rotational speeds are essentially the same.

Failed due to use of apparent forward speed this calculation method obviously if already one Slipping etc. has occurred. Due to lack of facilities is also one that works when driving straight ahead and cornering Slip and anti-lock control not possible.

DE 36 06 797 A1 deals with the same task. Here requires a special control system besides the sensors for wheel rotation, Forward speed and steering angle are additional Sensors for the rotational speed around the vertical axis, for the lateral accelerations (accelerometers) and for the Axle loads and a Doppler radar only for the actual forward speed. To measure the lateral acceleration an accelerometer is needed. These measured values become derives a special criterion that is slowed down when it occurs or the engine torque is reduced. However, it will neither the actual transverse speed nor the steering angle influenced.

Despite the high sensor effort, this is also an optimized one Regulation when the vehicle slides already fully developed not possible.

Another device is known from DE 35 45 715 A1, which is the steering angle and the apparent forward speed used and in a computing unit a target speed difference the front wheels are calculated to get this inside a tolerance range by means of brakes or engine power  correct accordingly and close the vehicle in front keep exceeding stable driving conditions. An interference the steering angle is not provided. Alternative configurations calculate for all-wheel drive vehicles with slip control instead the lateral acceleration and the apparent yaw rate and compare them with the measured values of acceleration or yaw rate sensors.

This facility also fails because of the use of the apparent Speed when slipping has already occurred.

Laser Doppler sensors are also known per se. In DE 38 04 750 C1 is e.g. B. a method for the remote detection of Vehicle speeds described. Here is a laser Doppler sensor used for speed measurement; this is however not arranged in the vehicle itself, but by operated from a remote, fixed measuring station and serves a completely different task, namely monitoring the prescribed maximum speeds.

Starting from the device for the controlled reduction of the Brake pressures in the front and rear brake cylinders of a motor vehicle According to US 3 910 647, the invention has therefore Tasked to create a facility that would drift automatically recognize from the lane and use the measured actual speed, d. H. true above-ground speed can largely reduce. The driver's intention following a lane chosen by him should be recognized and driving errors or unfavorable road conditions as possible Getting corrected. This should make emergency situations easier to manage and the driving direction desired by the driver in almost be stabilized in all realistic road situations. By weighing the requirements for optimal function unrealistic, fictional situations as well as real ones the required outlay on equipment should be as small as possible being held.  

This task is carried out with the characterizing features of the claim 1 solved. Advantageous further developments are in the subclaims and configurations shown.

The invention, in the following also called Anti-Slip System (AGS) is in several Exemplary embodiments in the following description and in explained to the figures. It shows  

Fig. 1 is a side view of an automobile incorporating Doppler sensors, together with their respective directions of view or laser beams,

Fig. 2 is a plan view of the actual velocity vector of a motor vehicle with a Doppler sensor whose line of sight component and transversely having longitudinally to the direction of travel, the from actual forward speed and actual lateral speed vectorially composing itself of the motor vehicle in the road plane and the steering angle,

Shows a plan view prescribed. 3 of a motor vehicle with a steering angle and vehicle speed by, regular or target lane and a lateral drift resulting from the true or actual lane,

Fig. 4 is a vector diagram of target and actual vehicle speed and the components thereof transversely and longitudinally to the direction of travel,

Fig. 5 is a block diagram of the anti-slip system,

Fig. 6 is a block diagram of a laser working in the Homodynbetrieb Doppler sensor,

Fig. 7 shows the waveform of a Doppler sensor in incipient lateral drift,

Fig. 8 shows the waveform of a Doppler sensor, the onset of slippage.

As shown in FIGS. 1 and 2, 10 , z. B. on its underside, rear axle or engine compartment one or more with semiconductor laser 40 and superposition reception working in their measuring direction 51 with a narrowly focused laser beam 45 obliquely down to the floor 1 with directional components 51 a, b along and transverse to the direction of view Doppler sensors 30, 30 a arranged and connected to the control unit 22 according to FIG. 5. This evaluates in the computing unit 22 b for Doppler analysis and velocity analysis resulting from the movement of the vehicle 10 in the direction of travel and transversely thereto, the resulting Doppler frequencies (Figs. 7 and 8) of the or of Doppler sensors 30, 30 a (Fig. 6) and compares them with the target values of the components 52 a, b of the target vehicle speed 52 for the target lane 55 determined from the rotational speeds of the wheels 11 and steering lock 50 by the sensor system 21 ( FIG. 3). If a lateral drift 54 b ( FIG. 4) from the target lane 55 or a slip 54 a is detected, that is to say if the wheels 11 spin, the control unit 22 emits corresponding correction signals to the servo system 20 of the motor vehicle 10 in order to detect the deviation of the actual To minimize lane 56 from the regular desired lane 55 desired by the driver. Lateral drift 54 b and slip 54 a are thus the undesirable speed components to be corrected, by means of which the regular vector of the target vehicle speed 52 desired by the driver is transformed into the actual vehicle speed vector 53 , ie the actual above-ground speed 53 .

Doppler sensors for speed measurement, which are operated with lasers and in superimposed reception, are known per se (see P 38 04 750 and P 37 02 742 from the same inventor, US Pat. No. 4,696,568). In principle, lasers of any wavelength can be used if their frequency stability, ie their coherence length, is sufficient for the reception of superimposition. For the intended use, however, small sensor dimensions and a water-permeable laser wavelength are advantageous, the latter in order to achieve a z. B. water layer moving through the wind to be able to measure the solid surface of the carriageway 1 . Both requirements are met in an almost ideal way by semiconductor lasers, e.g. B. GaAlAs laser diodes met.

However, semiconductor lasers have hardly been used in practice because the previous applications measuring distances of at least a few meters demanded while using semiconductor lasers because of their short Only achieve coherence lengths of measuring distances up to the decimeter range let. However, it has been found that some types of the some time in high numbers for laser turntables (compact disc) etc. produced continuously emitting GaAlAs semiconductor lasers are also suitable for measuring distances in the range of 1 m and thus the Order of magnitude of the application according to the invention.

In the embodiment of the Doppler sensor 30 shown in FIG. 6, the polarized radiation of the semiconductor laser 40 is first of all transmitted through the focusing optics 41 , e.g. B. a gradient index lens (SELFOC lens) bundled. The laser radiation 45 passes through the Brewster plate 42 and the λ / 4 plate 43 and is directed in the measuring direction 51 by the transmitting / receiving optics 44 and the location on the floor 1 to be measured. In order to determine the measuring direction as precisely as possible, the laser beam 45 is focused on the ground. The laser light 45 a scattered back from this is collected by the transmitting / receiving optics 44 , has undergone a total rotation of the polarization direction by 90 ° after the second pass through the λ / 4 plate 43 and arrives via the Brewster plate 42 and the converging lens 47 the detector 48 . A small part 45 b of the emitted laser radiation 45 is on a suitable surface, for. B. on a surface 44 a of the transmitting / receiving optics 44 , which is designed to be partially reflective, reflects and reaches the local oscillator laser beam 45 b as the received laser light 45 a also on the detector 48 . By superimposing the two beams 45 a, 45 b, the sum frequency and the difference frequency f, which are not of interest here, are produced at the detector 48 . Because of the Doppler effect, the latter is proportional to the amount of the relative speed v between the sensor 30 and the appropriate area, ie thus also the actual speed 52 of the vehicle 10 on the road 1, including any lateral drift, according to the formula

f = (2v / λ) cos α.

Here λ is the laser wavelength and α is the angle between the direction of the overall movement and the laser beam 45 .

In order to be able to measure not only the amount, but also the sign, ie the direction of the speed, one usually generates during heterodyne reception by means of a z. B. acousto-optical modulator and one of these driving oscillators of the frequency f₀ a frequency offset between the transmit and local oscillator beam 45, 45 b. There is a Doppler shift of

f = f₀ ± (2v / λ) cos α,

the plus sign refers to a movement of the appropriate place on the Doppler sensor 30, 30 a.

In both cases, a measured variable in analog form is available as a control variable Available so that optimized, for. B. Proportional-integral control loops can be used to correct driving errors.

However, the additional effort of the modulator and oscillator is not necessary, and the measurement of the direction of speed does not have to be dispensed with if one proceeds as follows: The double sensor 30 intended for measuring the lateral drift receives a gaze component 51 a in the direction of travel, that is to say it does not only look back Side, but also diagonally forward or backward. The angle α is chosen so large that the speed resulting from the driving speed 52 is even greater than the possible lateral drift 54 b and all other possible disturbing influences. This can be safely achieved in almost all driving conditions that occur in reality, including emergency situations. The measured Doppler frequency thus almost always remains above a minimum while driving, so that practically no ambiguity can occur.

As Fig. 5 shows, the control unit 22 in known manner with the elements of the sensor system 21, namely, the sensors for measuring the rotational speeds of the wheels 23 ad and drives (engine, transmission, drive shafts, tachometer, etc.) and the gas and brake pedal pressure 24, 24 a and the sensor 25 of the steering lock 50 and one or more Doppler sensors 30, 30 a connected, the signals of which it processes. It also controls the elements of the servo system 20 , namely the servo elements or actuators for brakes 26 a-d, possibly gears or wheel drives 27 a-d, motor power 27 e and steering 28 . The control unit 22 contains several computing units with certain highlighted functions, namely the computing unit 22 b for Doppler analysis and speed evaluation, the computing unit 22 c for vibration analysis and the computing unit 22 d for self-calibration and function test. A further arithmetic unit 22 a with memory calculated from the measured steering lock 50 and the target vehicle speed 52, a predetermined by the driver target lane 55, and thus the target lateral velocity 52 b and serves to perform the various calculations, the storage of the required algorithms, physical Models, system parameters, measurement results etc., the control of the various interfaces and the entire process control. The control unit 22 can thus recognize the intention of the driver and, as will be explained in more detail below, determine the occurrence of emergency situations such as lateral drift 54 b, slip 54 a and impending blocking and counteract them with corresponding correction signals to the servo system 20 .

The computing unit 22 b for Doppler analysis and speed evaluation determines the actual vehicle speed 53 , that is to say the actual above-ground speed of the vehicle 10 with respect to the ground 1 . For this purpose, the signals of the Doppler sensors 30, 30 a a frequency measuring device, for. B. a frequency or spectrum analyzer or a filter bank. In the case of firm ground 1 , that is to say generally only a single Doppler frequency per Doppler sensor 30, 30 a, which is measured very precisely. From this, the computing unit 22 b calculates the various components 53 a, 53 b of the actual vehicle speed 53 with respect to the ground 1 with the computing unit 22 a according to formula (1), taking the required directional angles from the memory of the computing unit 22 a.

The curvature of the lane 55 taken by the driver is an interference which the side-looking Doppler sensor 30 cannot initially distinguish from a lateral drift. However, the curvature depends on the steering angle 50 and is modified by the chassis, if necessary, in accordance with the vehicle speed 52 and the centrifugal forces resulting therefrom. According to the invention, the control unit 22 or its computing unit 22 b for Doppler analysis and speed evaluation takes this previously known relationship into account, ie calculates as drift 54 b the difference between the transverse speed 53 b corresponding to the Doppler frequency f and the setpoint values resulting from the curvature of the lane and the vehicle speed 52 Lateral speed 52 b.

The chassis vibrations, which result from the road conditions and driving behavior, exert a further disturbing influence. The viewing directions 51 of the Doppler sensors 30, 30 a thus oscillate briefly again and again around their desired directions, so that the measuring distances to street 1 also vary. The Doppler sensors 30, 30 a are thus simulated in regular driving situations without drift and slip speed changes.

However, this interference is also taken into account in several ways. FIG. 7 shows as a solid line the time course of the Doppler frequency of the side-facing Doppler sensor 30 and the speed v corresponding to formula (1) for a situation in which a sudden impact on the roadway causes the chassis to oscillate (strongly damped). For simplicity's sake, the course drawn relates qualitatively to straight-ahead driving and constant vehicle speed without drift, slipping or locking of the wheels. First, the Doppler sensor 30 delivers a constant Doppler frequency, which is not equal to zero due to its gaze component 51 a in the direction of travel and is proportional to the vehicle speed 52 . After a large deviation due to the impact acting at time t 1 (e.g. transverse channel), the Doppler frequency oscillates back to the original value in a manner determined by the suspension and damping of the chassis.

The dashed curve in FIG. 7 describes the same situation, but in which the lane impact initiates a lateral drift 54 b of the vehicle 10 . With the straight-ahead drive assumed for the sake of simplicity, this could be done on a smooth road with a bank; this sideways drift occurs far more frequently when cornering. The above-described course of the Doppler frequency now changes due to an increasing lateral drift speed 54 b, which vectorially adds to the forward speed 53 a. After the chassis vibration has subsided at t₂, there remains a shift in the Doppler frequency which corresponds to the lateral drift velocity 54 b (assumed here as constant).

To this suspension vibrations to be recognized as such and to separate optionally a drift 54b of the chassis vibrations, analyzes the arithmetic unit 22c for vibration analysis of the control unit 22 the time course of the measured Doppler frequency with the aid of the known vibration characteristics of the landing gear and determines the drift 54 b. It then outputs to the servo system 20 this drift 54 b counteracting correction signals, ie it reduces the drive power, changes the steering angle 50 etc.

The speed changes simulated by chassis vibrations are separated by one of the usual mathematical methods for curve adaptation, with which the measured curve of the Doppler frequency is represented by the sum of two theoretical curve curves. The first is the one that arises arithmetically using a physical model from a road impact of certain strength and the characteristic chassis properties. The second is the one that was not caused by chassis vibrations, but by real changes in speed, i.e. drift 54 b. The parameters to be adjusted are therefore essentially the type and strength of the lane impact as well as the real speed change sought. These too can be represented by a physical model, the vehicle-specific characteristic parameters are determined in vehicle tests and how the characteristic vibration properties of the running gear in the memory of the computer unit 22 a are stored.

Another interference causes a z. B. wind moving water layer on the Doppler sensors 30, 30 a appropriate places of the ground. 1 Here, the spectrum analyzer of the computing unit 22 b generally simultaneously two different doppler frequencies determined, namely the desired regular Doppler frequency of the base 1 and the unwanted Doppler frequency of the moving water surface. The wind-ruffled water surface reflects a laser intensity that is low in the mean time, but varies very quickly due to reflection, with high peak values, while the bottom 1 uses Lambert scattering to scatter back a slightly modulated laser intensity whose temporal behavior approximates that immediately before the wind-moving puddle of water, reducing its intensity and is modulated by the varying extinction in cloudy water. The timing of the two Doppler frequencies is also different. While the Doppler frequency corresponding to the bottom 1 changes only relatively slowly and in a similar way as in front of the puddle of water, that of the wave-shaped water surface varies significantly more.

The computing unit 22 b uses these properties to differentiate between regular, ie searched and undesired Doppler frequency. For this purpose, the spectrum analyzer of the computing unit 22 b assigns the corresponding laser intensities to the two Doppler frequencies found. Their variation in time is stored in the memory of the computing unit 22 a, analyzed by the processing unit 22 a and associated with the two physical effects by means of the above-described criteria. By arranging an acceleration sensor 29 a on the vehicle 10 and comparing its signals with the time derivative of the two Doppler frequencies by the control unit 22 , this detects with even greater probability the Doppler frequency assigned to the ground 1 , since these differ in the same way as the measured values of the acceleration sensor 29 a behaves.

The same Doppler sensor 30 can now also be used for the approximate determination of a slip 54 a or spinning of the wheels 11 . Fig. 8 shows the time course of the Doppler frequency and the corresponding speed - again for the sake of simplicity for driving straight ahead without lateral drift - when suddenly accelerating to z. B. sandy soil at the time t₁ and thereby initiated slip 54 a. The control unit 22 recognizes that the speed 52 a calculated from the speeds of drives and wheels is greater than the actual forward speed 53 a measured with the Doppler sensor 30 . It interprets the difference as slip 54 a and outputs correction signals counteracting this slip to the servo system 20 , ie it reduces the drive power, the drive torques of the individual wheels 11, etc.

Such an anti-slip system (AGS) also replaces the previously common anti-lock systems (ABS) in an advantageous manner. For this purpose, the control unit 22 , just as in the case of the slip control, compares the actual forward speed 52 a with the speed derived from the rotational speeds of the wheels and, if appropriate, emits corresponding correction signals to the servo elements of the braking system 26 a-d. An emerging blockage of the wheels is thus treated in a completely analogous manner to the slip control described above as slip with the opposite sign and thus corrected even before the actual blockage. In contrast to the previous ABS systems, no "yes-no" regulation, ie intermittent full braking, is used as intermittent blocking. Rather, according to the invention, a continuous, for. B. output by an integral proportional control loop optimized control signal. This reduces the braking distance required compared to a vehicle equipped with ABS.

When correcting slip 54 a and the beginning of blocking, the control unit 22 takes into account that, under normal driving behavior, the speeds of the individual wheels 11 are almost the same size and are only slightly modified by the steering angle 50 . The target speeds of the individual wheels 11 are thus determined by the actual forward speed 53 a and the steering angle 50 . The deviations in the individual wheel speeds resulting from slip 54 a or the beginning of blocking of the wheels 11 are therefore advantageously not generally corrected, but instead are corrected by individual correction signals to the servo elements for drives 27 a-d or brakes 26 a-d of the individual wheels 11 .

It is understood that the exact detection of all the driving condition descriptive variables, that is, the actual speed vector 53 with the forming it components of the actual forward speed 53a, the actual lateral speed 53 b of cornering and the lateral drift 54 b, any vertical velocity and the roll - In principle, an inertial system with a correspondingly large effort requires the yaw and pitch position of the chassis and the associated angular momentum.

However, such a complete measuring system is not considered necessary for the purpose of correcting irregular driving conditions. A measuring system reduced to the essential requirements for the correction of drift 54 b and slip 54 a or blocking requires, in addition to the servo and sensor systems 20, 21 and the control unit 22 , only two Doppler sensors 30, 30 a to determine the approximated current speed vector of the Vehicle 10 or its projection 53 onto the road 1 and three sensors for the position of the underside of the motor vehicle 10 relative to the floor 1 , ie a sensor 29 for the chassis vibrations. Suitable for this are, for. B. mechanical or electrical, directly or indirectly length-measuring sensors or Doppler sensors of the type described above. All conceivable emergency situations can be detected sufficiently well and thus optimally effective correction signals are generated.

However, in order to further reduce the effort required, the invention also uses the following findings:

• - An exact recording of the disturbance variable is not necessary to generate fully sufficient correction signals. If the drift 54 b or slip 54 a or the braking force when blocking falls below a certain value, then, due to the transition from sliding friction to static friction, regular driving behavior suddenly occurs again.
• - In many emergency situations, only one of the two irregular ones occurs Driving behavior. The chassis vibrations are often also small.  
• - Even if drift 54 b, slip 54 a or blocking and chassis vibrations occur simultaneously and are only measured qualitatively, the slip 54 a or blocking of the wheels 11 reacts very quickly to corresponding correction signals, e.g. B. thrust reduction or shutdown or braking force reduction, so that very soon only the drift 54 b remains as a disturbance variable.

In all of these cases, however, the arrangement of a single Doppler sensor 30 described above is sufficient to supply practically all the necessary measurement signals to the control unit 22 for generating effective correction signals to the servo system 20 of the motor vehicle 10 .

A further exemplary embodiment provides for the arrangement of the Doppler sensor 30 on the rear axle 12 of the motor vehicle 10 only with a viewing direction 51 b transverse to the direction of travel, without any slip measurement. As a result, the case of the onset of the drift 54 b or skid movement on the rear axle 12 , which is particularly important in some vehicle types, is optimally recorded. The direction of the measured drift 54 b is derived by the control unit 22 from the steering angle 50 causing it or, in the case of ongoing drift 54 b, from its previous direction, rate of change, etc.

It is certainly advantageous to provide a certain margin of tolerance within which the correction signals are either completely suppressed or only be shown to the driver. Also one requested by the driver complete or partial override of the automatic correction is without further feasible.

The sensors, in particular the only Doppler sensor 30 of the special exemplary embodiment, can be installed in a simple manner, ie with simple mechanical and electrical interfaces. Manual adjustment and calibration of the sensors are not necessary. The control unit 22 instead contains a computing unit 22 d for self-calibration and function test, which automatically at larger intervals, for. B. is activated at the start of each new journey by the computing unit 22 a. It first checks whether there is regular driving behavior, which is usually the case at the start of the journey, and then calibrates the sensor signals. Since the measurement of the Doppler frequency, like any frequency measurement, is very precise, e.g. B. by means of a frequency or spectrum analyzer contained in the computing unit 22 b, the influence of the sensor line of sight on the measured value is obtained directly by comparison with the measured values of the sensor system 21 , that is, the sensors for the speeds of wheels and drives and for the steering angle . The vibration behavior of the chassis is also checked and the system constants required for its analysis recalibrated. If the calibrated values remain within a specified range, this is evaluated as a partial function test. This is completed by customary electronic self-tests and an evaluation of the laser power received in order to obtain information about possible contamination of the sensor optics 44 despite suitable protective measures.

Due to the requirement for a laser wavelength that is permeable to water, the laser 40 used here is initially not principally eye-safe. However, this is the case in practice in the application envisaged here because of the low transmission power with overlay reception and a short measuring range. A suitable safety circuit is nevertheless recommended for overriding safety reasons. It is therefore contemplated that the control unit 22 or its processing unit 22 a the laser 40 will switch on when the ignition of the motor vehicle 10 is turned on and the 1st gear is engaged.

Through the measures disclosed above, an anti-slip system for motor vehicles (AGS) is created that recognizes the driver's intentions without great effort on the smoothest, arbitrary road surface, intervenes correctively in the event of lateral drift or spinning wheels with optimized control characteristics and thus a general one Directional stabilization of the vehicle and control of emergency situations. The precisely measured actual ground speed and the acceleration of the vehicle measured with the acceleration sensor 29 a can moreover advantageously be used in an on-board navigation system and thus significantly improve its accuracy.

Claims (14)

1. Device for stabilizing motor vehicles when cornering, with

• - a servo unit for brakes,
• an arrangement of sensors for measuring the steering angle,
• an automatic control unit, connected to the servo unit and the arrangement of the sensors, for controlling the servo unit to correct irregular driving conditions,
• at least one Doppler sensor looking obliquely downwards onto the roadway, which is directed transversely to the longitudinal axis of the vehicle and detects the actual transverse speed,
  characterized in that
• a) the servo unit ( 20 ) for brakes ( 26 a-d) also the drives ( 27 a-e) and the steering ( 28 ) are assigned,
• b) the arrangement of sensors ( 21 ) for measuring the steering angle ( 25 ) is also assigned sensors for measuring the rotational speeds of wheels and drives ( 23 a-e),
• c) the Doppler sensor ( 30 ) is a laser Doppler sensor with a narrowly focused laser beam ( 45 ),
• d) in the control unit ( 22 ) a first computing unit ( 22 a) is provided, which from the measured steering angle ( 50 ) and from the target vehicle speed ( 52 ) a target lane ( 55 ) predetermined by the driver and thus the target transverse speed ( 52 b) calculated,
• e) in the control unit ( 22 ) a second computing unit ( 22 b) is provided for evaluating the signals of the Doppler sensor ( 30 ), which determines the actual transverse speed ( 53 b), the values of which depend on the value of the target transverse speed ( 52 b ) subtracts, and
• f) the control unit ( 22 ) calculates counter-correction signals from this difference of the drift ( 54 b) and outputs them to the servo unit ( 20 ).

2. Device according to claim 1, characterized in that

• a) the Doppler sensor ( 30 ) is also directed with a direction component ( 51 a) in the direction of travel and detects the actual forward speed ( 53 a),
• b) sensors ( 23 a-d) are provided for measuring the actual speeds of the wheels,
• c) the control unit ( 22 ) determines the actual forward speed ( 53 a) from the signals of the Doppler sensor ( 30 ), and from this and the measured steering angle ( 50 ) determines the desired individual wheel speeds, of which those with the sensors ( 23 ad) for subtracts the actual individual wheel speeds and interprets the differences as the respective slip ( 54 a) of the wheels ( 11 ), and
• d) the control unit ( 22 ) calculates correction signals for the individual wheels ( 11 ) which counteract the respective slip ( 54 a) and outputs them to the servo unit ( 20 ).

3. Device according to at least one of claims 1 or 2, characterized in that the first computing unit ( 22 a) for the control unit ( 22 ) and the second computing unit ( 22 b) performs the required calculations, the required algorithms, physical models, system parameters , Measurement results etc. as well as the sequence control stores and controls interfaces between the control unit ( 22 ), the arrangement of sensors ( 21 ) and the servo unit ( 20 ). 4. Device according to at least one of claims 1 to 3, characterized in that the control unit ( 22 ) with a third computing unit ( 22 c) stores the time profile of the measured Doppler frequency in the memory of the first computing unit ( 22 a), analyzes and as a sum calculated two curves, namely the Doppler frequency curve resulting from chassis vibrations and the drift ( 54 b) and / or slip ( 54 a), the characteristic parameters of the physical models of chassis vibrations, drift ( 54 b) and / or slip ( 54 a) are stored in the memory of the first computing unit ( 22 a). 5. Device according to at least one of claims 1 to 4, characterized in that an additional chassis sensor system ( 29 ) for measuring the chassis vibrations is arranged on the motor vehicle ( 10 ), and that the control unit ( 22 ) whose signals are supplied for correcting the measured Doppler frequencies . 6. Device according to at least one of claims 1 to 5, characterized in that the Doppler sensor ( 30 ) is operated in homodyne reception. 7. Device according to at least one of claims 4 to 6, characterized in that the direction component pointing in the direction of travel ( 51 a) is chosen so large that the Doppler frequency originating from the driving speed ( 52 ) is greater than that of the chassis vibrations and the lateral Drift ( 54 b) resulting Doppler frequency. 8. Device according to at least one of claims 3 to 6, characterized in that the Doppler sensor ( 30 ) on the rear axle ( 12 ) of the motor vehicle ( 10 ) is arranged and that the control unit ( 22 ) the direction of the measured drift ( 54 b) derived from the direction of the steering lock ( 50 ) and from the previous course of the measured drift ( 54 b) stored in the memory of the first computing unit ( 22 a). 9. Device according to at least one of claims 1 to 8, characterized in that the control unit ( 22 ) contains a fourth computing unit for self-calibration and function test, which is automatically activated at greater intervals during regular driving behavior by the first computing unit ( 22 a). 10. The device according to at least one of claims 1 to 9, characterized in that the second computing unit ( 22 b) for evaluating the signals of the Doppler sensor ( 30 ) has a frequency measuring device such as a spectrum analyzer, filter bank, etc. 11. The device according to at least one of claims 1 to 10, characterized in that a sufficiently frequency-stable laser is used as the laser ( 40 ), the radiation in water is little attenuated, in particular a continuously emitting GaAlAs semiconductor laser is used. 12. The device according to at least one of claims 1 to 11, characterized in that when two Doppler frequencies occur at the same time in a Doppler sensor ( 30 ), the second arithmetic unit ( 22 b) the temporal profiles of the reception intensities associated with the two Doppler frequencies in the memory of the first arithmetic unit ( 22nd a) stores, and that the first arithmetic unit ( 22 a) uses a physical model to identify one of the two Doppler frequencies as that which corresponds to the actual vehicle speed ( 53 ). 13. The device according to at least one of claims 1 to 11, characterized in that an acceleration sensor ( 29 a) is arranged on the vehicle ( 10 ), and that when two Doppler frequencies occur at the same time in a Doppler sensor ( 30 ), the control unit ( 22 ) as the Doppler frequency corresponding to the actual vehicle speed ( 53 ) is identified, the time derivative of which behaves in the same way as the measured values of the acceleration sensor ( 29 a). 14. The device according to at least one of claims 1 to 13, characterized in that the control unit ( 22 ) by its first computing unit ( 22 a) turns on the laser ( 40 ) only when the ignition of the motor vehicle ( 10 ) is switched on and the 1st Gear is engaged.