DE3825639A1 - Anti-skid system for motor vehicles - Google Patents

Abstract

The invention relates to an anti-skid system for motor vehicles, having sensor systems and servo systems for brakes, wheels, drive and steering, which has at least one double sensor which operates with a semiconductor laser and heterodyne reception and looks obliquely downwards towards the ground. A control unit uses the Doppler frequency and assistance from the other sensor signals to determine lateral sliding, wheelslip etc. of the motor vehicle and emits correspondingly counteracting signals to the servosystem. <IMAGE>

Description

The invention relates to an anti-slip system (AGS) for power vehicles with a servo system for drives, brakes and steering and a sensor system for measuring the speeds of wheels and Drives according to the preamble of claim 1.

Such systems are used in motor vehicle construction as anti-lock systems (ABS) and successfully used for slip control. Restores the sensor blocking or spinning when braking or accelerating Wheels fixed, the control unit gives the appropriate correction signals to the brakes or drives to this irregular behavior counteract.

However, these systems are unable to break out sideways, Drifting or sliding out of the steering lock and possibly Driving speed prescribed, i.e. lane desired by the driver and to counteract this irregular behavior. Also the Previously known slip control methods are based on the sudden spinning individual drive wheels are limited and fail in the long term Slipping on smooth roads despite "soulful" accelerating.

In addition, these methods show poor control behavior. The size the deviation from the setpoint is not proportional as a controlled variable applies, but a "yes-no" rule is used, e.g. just distinguishes between full and missing brake pressure. A "soulful" and therefore optimal regulation is not possible.

The published patent application DE 36 12 550 describes a motor vehicle Fixed, working with laser measuring device described the Laser beam emits in the cross-street direction and that from the streets receives and evaluates the surface of the reflected laser beam. this device however, is also unable to make irregular driving movements determine and correct, but recognizes the road condition in order determine their need for repair.  

The publication Eu-OS 02 49 264 describes a sensor and servo system for motor vehicles in which a sensor has a lateral acceleration of the vehicle measures and initiates countermeasures. This procedure too is unable to detect lateral drift or wheel slip and settle, but just tries the vehicle suspension system to optimize.

The invention has therefore set itself the task of eliminating these disadvantages and creating an anti-slip system (AGS) that automatically detect a lateral drift from the lane and him with an opti mized control, such as a proportional-integral control , ie counteract "feeling full". Also, the "not abrupt" spinning or a longer lasting slippage not far above the actual driving speed as well as an emerging blocking of the wheels - ie even before the wheels are fully blocked - should be automatically recognized and eliminated with an optimized control. The driver's intention to follow a lane chosen by him should be recognized and driving errors or unfavorable road conditions should be corrected as best as possible. This should make emergency situations easier to control and stabilize the direction of travel desired by the driver in almost all realistic driving situations. By weighing the requirements for optimal function in unrealistic, fictitious situations as well as in real-life situations, the required outlay on equipment should be kept as low as possible.

This task is accomplished by the measures set out in the claims solved reliably and effectively, being in the subclaims Developments and refinements are shown. The invention is in several exemplary embodiments in the description below and in explained the figures of the drawing. Show it:

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 having a motor vehicle with a Doppler sensor, the sen viewing direction components along and across the direction of travel, the VEK of true forward speed and true lateral velocity toriell located composing true velocity vector of the motor vehicle in the road plane and the steering angle,

Fig. Prescribed 3 is a plan view of a motor vehicle having a steering angle and vehicle speed by, regular traffic lane and a lateral drift resulting from the true lane,

Fig. 4 is a vector diagram of the regular and true vehicle speed, as well as their components 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, one or more of the motor vehicle 10 , for example on its underside, rear axle or engine compartment, are working with semiconductor laser 40 and superposition reception, in their measuring direction 51 with a narrowly focused laser beam 45 at an angle down to the floor 1 with rich tion components 51 a , b longitudinal and transverse Doppler sensors 30 , 30 a arranged and connected to the control unit 22 according to FIG. 5. This evaluates in subunit 22 a for Doppler analysis and speed evaluation the Doppler frequencies ( FIGS. 7 and 8) of the Doppler sensors 30 , 30 a ( FIG. 6) resulting from the movement of the vehicle 10 in the direction of travel and transversely thereto and compares them with the setpoints for the regular lane 55 determined by the sensor system 21 from the speeds of the wheels 11 and the steering angle 50 ( FIG. 3). If a lateral drift 54 b ( FIG. 4) is determined from the regular lane 55 or a slip 54 a , ie spinning of the wheels 11 , the control unit 22 emits corresponding correction signals to the servo system 20 of the motor vehicle 10 to determine the deviation of the true lane 56 from the regular lane 55 desired by the driver. Lateral drift 54 b and slip 54 a are thus the undesirable speed components to be corrected, through which the regular vector of the vehicle speed 52 desired by the driver is transformed into the true speed vector 53 , ie the actual ground speed is transformed.

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 measurements and a water-permeable laser wavelength are advantageous, the latter in order to be able to measure the solid subsurface of the roadway 1 through a layer of water moved by the wind, for example. Both requirements are met in an almost ideal way by semiconductor lasers, for example GaAlAs laser diodes.

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 bundled by the focusing optics 41 , for example a gradient index lens (SELFOC lens). The laser radiation 45 passes through the Brewster plate 42 and the λ / 4 plate 43 and is directed by the transmitting / receiving optics 44 in the measuring direction 51 to the point to be measured on the floor 1 . 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 of the emitted laser radiation 45 is reflected on a suitable surface, for example on a surface 44 a of the transmitting / receiving optics 44 , which is designed to be partially reflective, and also arrives as a local oscillator laser beam 45 b like the received laser light 45 a 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, that is to say 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, a heterodyne reception is usually generated by means of, for example, an acousto-optical modulator and an oscillator of frequency f ₀ that drives it, a frequency offset between the transmit and local oscillator beam . There is a Doppler shift of

f = f ₀ + (2v / λ ) cos α ,

the plus sign refers to a movement of the appropriate location 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, e.g. Proportional-integral control loops can be used to correct driving errors.

The additional effort of modulator and oscillator is not neces sary, and the measurement of the speed direction does not have to be dispensed with if one proceeds as follows: The Doppler sensor 30 intended for measuring the lateral drift receives a gaze component 51 a in the direction of travel, ie it does not only look to the side, but also diagonally to the front or back. The angle .alpha. Is chosen just so large that the speed amount 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 a known manner with the elements of the sensor system 21, namely, the sensors for measuring the rotational speeds of wheels (23 a - d) and drives (engine, transmission, to drive shafts, tachometers etc. ) and the gas and brake pedal pressure 24 , 24 a and the sensor 25 of the steering lock 50 and one or more Dopp lersensoren 30 , 30 a connected, the signals 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 sub-units with certain highlighted functions, namely the sub-unit 22 a for Doppler analysis and speed evaluation, the sub-unit 22 b for vibration analysis and the sub-unit 22 c for self-calibration and function test. Another sub-unit, the computing unit 22 d with memory, is used to carry out the various calculations, to store the required algorithms, physical models, system parameters, measurement results, etc., to control the various interfaces and to control the entire sequence. 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 this with corresponding correction signals to the servo system 20 .

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

The curvature of the lane 55 taken by the driver is an interference factor, 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 if necessary in accordance with the driving speed 52 and the resulting centrifugal forces from the chassis. According to the invention, the control unit 22 or its subunit 22 a 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 regular transverse speed 52 b resulting from the curvature of the lane.

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 speed changes even in regular driving situations without drift and slip.

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 road impact puts the chassis in a (strongly damped) vibration. For the sake of simplicity, the graph drawn relates qualitatively to straight-ahead driving and constant driving speed without drifting, slipping or locking 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 driving speed 52 . After a large deviation due to the impact acting at time t ₁ (eg 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 take place on a smooth road with a bank; this lateral 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 undercarriage vibration has decayed at t _{2, there} remains a shift in the Doppler frequency which corresponds to the lateral drift speed 54 b (assumed here to be constant).

To this suspension vibrations to be recognized as such and, optionally, a drift 54 b to separate from the chassis vibrations, analyzes the subunit 22 b 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 processes for curve fitting, with which the measured Doppler frequency is represented by the sum of two theoretical 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 matched are 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, it will averages the vehicle-specific characteristic parameter in vehicle tests and are stored as the characteristic vibration properties of the running gear in the memory of the computing unit 22 d.

A further disturbing effect is caused by a layer of water moved by the wind, for example, on the points of the floor 1 that are appropriate for the Doppler sensors 30 , 30 a . Here, the spectrum analyzer of subunit 22 a generally detects two different Doppler frequencies at the same time, namely the desired regular Doppler frequency of the bottom 1 and the undesired Doppler frequency of the moving water surface. The wind-ruffled water surface reflects a laser intensity that is low on average, but changes very quickly due to reflection, with high peak values, while the bottom 1 uses Lambert scattering to scatter a slightly modulated laser intensity whose behavior over time approximates that immediately before the wind-moving puddle of water, whereby its intensity reduced and 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 manner similar to that in front of the puddle of water, that of the wave-shaped moving water surface varies significantly more.

The subunit 22 a uses these properties to differentiate between regular, ie searched and unwanted Doppler frequency. For this purpose, the spectrum analyzer of subunit 22 a assigns the corresponding laser intensities to the two Doppler frequencies found. Their variation in time is stored in the memory d of the arithmetic unit 22, analyzed by the computing unit 22 d 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 , the latter recognizes 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 on, for example, sandy soil at time t ₁ and slip 54 a initiated thereby. The control unit 22 recognizes that the speed 52 a calculated from the speeds of drives and wheels is greater than the true forward speed 53 a measured with the Doppler sensor 30 . It interprets the difference as slip 54 a and transmits 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 also advantageously replaces the anti-blocking systems that have been used up to now. 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 is thus corrected even before the actual blockage. In contrast to the previous ABS systems, no "yes-no" regulation, ie intermittent full braking, that is intermittent blocking, is used again. Rather, according to the invention, a continuous control signal, which is optimized, for example, by an integral-proportional control loop, is emitted analogously in one of the slip control systems described. 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 lock 50 . The target speeds of the individual wheels 11 are thus determined by the true forward speed 53 a and the steering angle 50 . The deviations of the individual wheel speeds caused by slip 54 a or the beginning of blocking of the wheels 11 are therefore advantageously not blanket, but 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 goes without saying that the exact recording of all the variables describing the driving state, ie the true speed vector 53 with the components that form it, true forward speed 53 a , true transverse speed 53 b from cornering and lateral drift 54 b , any vertical speed and the roll, yaw, and pitch position of the chassis and the associated angular momentum in principle requires an inertial system with a correspondingly large effort.

However, such a complete measuring system is not considered necessary for the purpose of correcting irregular driving conditions. A measurement 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 one 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 system 29 for the chassis vibrations. Suitable for this purpose are, for example, mechanical or electrical, directly or indirectly length-measuring sensors or Doppler sensors of the type described above. All conceivable emergency situations can thus be adequately detected and thus optimally effective correction signals can be generated.

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

• - An exact recording of the disturbance variable is not necessary to generate fully sufficient correction signals. If 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 at the same time and are only measured qualitatively, the slip 54 a or blocking of the wheels 11 reacts very quickly to corresponding correction signals, for example reducing or switching off thrust or reducing braking force, so that very soon only the drift 54 b will remain 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 .

Another embodiment provides for the absence of slip measurement, the arrangement of the Doppler sensor 30 on the rear axle 12 of the motor vehicle 10 only with viewing direction 51 b transverse to the direction of travel. 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 have a certain margin of tolerance see 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 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 sub-unit 22 c for self-calibration and function test, which is automatically activated at larger intervals, for example at the start of each new journey by the computing unit 22 d . 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 occurs as each frequency measurement very precisely, for example by means of a in the sub unit 22 a frequency contained or spectrum analyzer, the influence of the sensor line of sight direction of the desired measured value is obtained directly by comparison with the measured values of the sensor system 21, that the sensors for the speeds of wheels and drives as well as 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 water-permeable laser wave length, the laser 40 used here is initially not eye-safe in principle. However, this is the case in the application provided here because of the low transmission power in practice with overlay reception and a short measuring range. A suitable safety circuit is nevertheless recommended for overriding safety reasons. It is therefore provided that the control unit 22 or its computing unit 22 d only switches the laser 40 on when the ignition of the motor vehicle 10 is switched on and 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 with little effort on the smoothest, arbitrary road, 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 as well as 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 (16)

1. Anti-slip system (AGS) for motor vehicles with a servo system for drives, steering and brakes, a sensor system for measuring the speed of wheels and drives and a control unit connected to both systems, characterized in that on the motor vehicle ( 10 ) the Doppler sensor ( 30 , 30 a ) is arranged so that the steering lock ( 50 ) is also provided by the sensor system ( 21 ) and at least one working with laser ( 40 ) and overlay reception, with narrowly focused laser beam ( 45 ) looks obliquely downwards towards the floor ( 1 ). detected, monitored by the control unit ( 22 ) and can be influenced by this by the servo system ( 20 ), that the control unit ( 22 ) in their computing unit ( 22 d ) from the steering lock ( 50 ) and from the regular vehicle speed ( 52 ) correct curvature of the regular lane ( 55 ) and thus the regular transverse speed component ( 52 b ) calculated when cornering that the control unit ( 22 ) by means of its subunit ( 22 a ) for Doppler analysis and speed evaluation from the signals of the Doppler sensor ( 30 ) which looks almost transversely to the direction of travel, determines the true transverse speed ( 53 b ), this value ( 53 b ) from the regular transverse speed ( 52 b ) subtracts and interprets the difference as a lateral drift ( 54 b ) from the regular lane ( 55 ), and that the control unit ( 22 ) transmits to the servo system ( 20 ) of the vehicle ( 10 ) this drift ( 54 b ) counteracting correction signals. 2. AGS according to claim 1, characterized in that the control unit ( 22 ) from the signals of a with a directional component ( 51 a ) looking in the direction of travel Doppler sensor ( 30 , 30 a ) the true forward speed ( 53 a ) and from it and out regular steering wheel turns resulting from the steering lock ( 50 ), from which the values determined with the sensors ( 23 a - d ) for single wheel turns are deducted, the differences are interpreted as slip ( 54 a ) or locking of the wheels ( 11 ) and for the individual wheels ( 11 ) emits correction signals counteracting this slip ( 54 a ) or blocking individually to the servo system ( 20 ) of the vehicle ( 10 ). 3. AGS according to claims 1 and 2, characterized in that a single Doppler sensor ( 30 ) is used for the approximate determination of lateral drift ( 54 b ) and slip ( 54 a ) or blocking, the direction of view ( 51 ) obliquely downwards Components in the direction of travel ( 51 a ) and transverse to it ( 51 b ). 4. AGS according to claims 1 to 3, characterized in that the computing unit ( 22 d ) with memory for the control unit ( 22 ) and its other subunits ( 22 a , b , c ) performs the required calculations, the required algorithms, physical Models, system parameters, measurement results etc. as well as the sequence control are saved and the interfaces between the control unit ( 22 ), the sensor system ( 21 ) and the servo system ( 20 ) are controlled. 5. AGS according to claims 1 to 4, characterized in that the control unit ( 22 ) with its subunit ( 22 b ) for vibration analysis saves the time profile of the measured Doppler frequency in the memory of the computer unit ( 22 d ), analyzes and as the sum of two curves calculated, namely the Doppler frequency curve resulting from chassis vibrations and the Doppler resulting from drift ( 54 b ) or slip ( 54 a ) or blocking, the characteristic parameters of the physical models of chassis vibrations, drift ( 54 b ), slip ( 54 a ) and blocking are stored in the memory of the computing unit ( 22 d ). 6. AGS according to claims 1 to 5, 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 fed to correct the measured Doppler frequencies. 7. AGS according to claims 1 to 6, characterized in that the Doppler sensor ( 30 ) is operated in homodyne reception. 8. AGS according to claims 1 to 7, characterized in that the Doppler sensor ( 30 ) which looks almost transversely to the direction of travel has an opposite small directional component ( 51 a ) in the direction of travel, which, however, is chosen to be so large that the in almost all realistic driving conditions the Doppler frequency originating from the driving speed ( 52 ) is greater than the Doppler frequency originating from chassis vibrations and lateral drift ( 54 b ). 9. AGS according to claims 1 to 7, characterized in that the Doppler sensor ( 30 ) is arranged on the rear axle ( 12 ) of the motor vehicle ( 10 ), that it has only one viewing component ( 51 b ) exactly transverse to the direction of travel, and that the control unit (22) the direction of the measured drift is derived (54 b) from the direction of the steering lock (50) and from the previously stored in the memory of the computing unit (22 d) course of the measured drift (54 b). 10. AGS according to claims 1 to 9, characterized in that the control unit ( 22 ) contains a subunit ( 22 c ) for self-calibration and function test, which is automatically activated at greater intervals and with regular driving behavior by the computing unit ( 22 d ). 11. AGS according to claims 1 to 10, characterized in that the subunit ( 22 a ) for Doppler analysis and speed evaluation has a frequency measuring device such as a spectrum analyzer, filter bank, etc. 12. AGS according to claims 1 to 11, characterized in that a sufficiently frequency-stable laser with a wavelength permeable to water, in particular a continuously emitting GaAlAs semiconductor laser, is used as the laser ( 40 ). 13. AGS according to claims 1 to 12, characterized in that when two Doppler frequencies occur at the same time in a Doppler sensor ( 30 ), the subunit ( 22 a ) shows the temporal profiles of the reception intensities associated with the two Doppler frequencies in the memory of the computing unit ( 22 d ) stores, and that the computing unit ( 22 d ) uses a physical model to identify one of the two Doppler frequencies as that which corresponds to the true vehicle speed ( 53 ) relative to the ground ( 1 ). 14. AGS according to claims 1 to 13, 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 ) than that of true vehicle speed ( 53 ) corresponding Doppler frequency identified, the time derivative of which behave in the same way as the measured values of the acceleration sensor ( 29 a ). 15. AGS according to claims 1 to 14, characterized in that the control unit ( 22 ) by its computing unit ( 22 d ) turns on the laser ( 40 ) only when the ignition of the motor vehicle ( 10 ) is switched on and the 1st gear is engaged is. 16. AGS according to claims 1 to 15, characterized in that the measured true vehicle speed ( 53 ) and optionally the signals measured by the acceleration sensor ( 29 a ) are fed to an on-board navigation system.