WO2000003901A1

WO2000003901A1 - Method and device for detecting the critical driving states in vehicles which are being driven

Info

Publication number: WO2000003901A1
Application number: PCT/EP1999/005081
Authority: WO
Inventors: Jürgen WOYWOD; Ralph Gronau; Dieter Burkhard; Hans Georg Ihrig; Lothar Kienle
Original assignee: Continental Teves Ag & Co. Ohg
Priority date: 1998-07-16
Filing date: 1999-07-16
Publication date: 2000-01-27

Abstract

The aim of the invention is to detect critical driving situations in vehicles which comprise a measured value sensor located on at least one wheel with which a change in distance between the measured value sensor and the measured value transmitter can be detected. To this end, the invention provides that values based on changes in distance are continuously detected by the measured value sensor during driving operation. In addition, the values are compared with corresponding reference values, and parameters which permit the determination of the existence of a tendency to overturn are inferred from the comparison of the temporarily stored values with the reference values.

Description

Method and device for determining critical driving conditions in vehicles in operation

The invention relates to a method and a device for determining critical driving situations in vehicles in driving operation according to the preamble of claim 1 and claim 8.

For vehicles with a high center of gravity and / or narrow track width, e.g. Trucks, lorries, buses, minibuses and off-road vehicles, it is known that there is a risk of tipping when cornering with a large roll. For example, in the book "Fundamentals of vehicle dynamics", TD Gillespie, Society of Automotive Engineers, Inc., Warrendale 1992, Chapter 9, pages 309-333, to which full reference is made in the present context, are various models for so-called rollover accidents described. Starting with a quasi-stationary model for a rigid vehicle, through a quasi-stationary model for a sprung vehicle, to dynamic models, taking into account roll natural frequencies, conditions for existing tipping risks are specified.

More recently it has been shown that passenger cars can also swing up to the side until they tip over. Such a risk of tipping is significantly increased by improper loading, for example extremely one-sided or on the vehicle roof, because the location of the Center of gravity of the vehicle is shifted upwards or to one side. In addition, vehicles that are designed as passenger cars with a relatively high center of gravity, such as the new vehicle class of the so-called "vans", are increasingly being approved.

In order to be able to effectively avoid such a critical operating state, it would be desirable

to be able to detect a critical situation, and

to be able to take suitable countermeasures upon detection.

In conventional control systems, for example the applicant's ESP system (= Electronic Stability Program), characteristic vehicle dynamics, which are indicative of critical driving situations, include the lateral acceleration or the temporal change in the lateral acceleration. For example, from German published patent application DE-A 196 32 943 "Method for operating a motor vehicle with braking stabilizing interventions", Daimler-Benz Aktiengesellschaft, a corresponding method for operating a motor vehicle with braking stabilizing interventions is described, in which the only one for the tendency to tip over the longitudinal axis of the vehicle indicative driving dynamics parameter, the lateral acceleration is used. An associated, predeterminable tilt prevention threshold value is provided for the lateral acceleration. When cornering, the vehicle is kept on track by the lateral forces acting on the tire contact patch on the road. Most of these lateral forces are applied by the wheels or tires on the outside of the curve. If the lateral acceleration occurring when cornering is above the anti-tipping threshold, one or more wheels are activated by activating a corresponding one Brake intervention converted into a state of high brake slip, which significantly reduces the lateral force that can be transmitted by the tires. As a result, the wheels on the outside of the curve can no longer withstand the transverse acceleration acting on them, which may mean an increase in the radius of the path, but at the same time the tipping moment is reduced and the vehicle is prevented from tipping about its longitudinal axis.

In the published patent application DE-A 197 46 889 "Vehicle motion control system", Aisin Seiki K.K. et al., a system for increasing the lateral stability of a motor vehicle when cornering is described, in which a tilt detection unit for detecting a tilting movement of a normal axis of the vehicle to its vertical axis and a curve determination unit for determining a cornering state of the vehicle are provided. To calculate the vehicle tilting movement or the vehicle tilting, either the height difference between the right and left side of the vehicle or the lateral acceleration of the vehicle is recorded in order to determine the roll angle between the vehicle horizontal and the roadway horizontal. A linearity between the lateral acceleration aq and the vehicle tilt characterized by a roll angle gamma is taken as a basis. If the inclination detection device detects a risk of tipping, braking the front wheel on the outside of the bend generates a counteracting yaw moment.

Nevertheless, it should be noted that the number of insurance claims that cause the above-mentioned vehicles to tip over is constantly increasing. In particular, it is often necessary to determine whether there is a product liability case. An important area of application is the detection of a not overturning, ie when the vehicle gets stuck on an obstacle and thereby rolls over. In this type of accident, it is important to find out whether the accident occurred only by tipping over on a stable circular drive (despite stable cornering forces), or by slipping and then tipping, for example on a curb.

Already known tachographs provide only an inadequate part of the information required for the above assessment.

From DE-OS 44 42 355, to which reference is made in its entirety in the present context, it is also known that in certain driving maneuvers, for example when driving quickly through tight bends, the dynamic forces that occur can lead to a temporary deformation of axle parts. Such a driving condition can thus be characterized on the basis of these forces. From this publication it is further known that a suitable measure for the elastic axis deformation offers the thickness of an air gap between the measuring sensor (sensor) and the measuring sensor (encoder) of a tachometer. Sensory devices for detecting wheel speeds generally consist of an incremental encoder that is mechanically connected to the rotating part and a sensor that scans this encoder. Ferromagnetic gears, toothed rings and ferromagnetic perforated disks are mostly used as encoders. Such a sensor with equipment for detecting the air gap is adjusted so that the dynamic ranges of elastic axis deformation and change in the amplitude of the sinusoidal input signal match sufficiently. Then there is a reproducible relationship between dynamic deformation of axle parts and the change in the input signal, which is to be used in combination with measured individual speeds as a yaw rate meter or for a plausibility check. This dynamic signal change is superimposed on the function of the speed measurement and does not lead to falsification of these two measured variables, which can be decoded together in the electronic controller.

It is therefore the object of the present invention to provide a method and a device for detecting a critical driving situation of a vehicle which is in driving operation, which allow the situations in question to be sensed and assessed with little effort.

This object is achieved in the method according to the invention in that during driving operation with the transducer values based on changes in distance between the transducer and the transducer are continuously recorded, in that the values are compared with corresponding reference values, and in that the values and the reference values are compared is based on parameters for the existence of a tendency of the vehicle to tip over.

The values of the change in distance and / or the parameters which are detected in this way are advantageously temporarily stored in a memory. The temporarily stored values are compared with corresponding reference values, so that the existence of the critical driving situation can be concluded from the comparison of the temporarily stored values and / or from the compared parameters. With the intermediate storage of the values and / or the parameters, the Recognition of a tipping that does not occur "on road" or has already occurred. This detection is particularly necessary for insurance reasons, since in such situations even a tip-over prevention function can no longer stabilize the vehicle and the vehicle manufacturer must therefore provide evidence that the tip-over prevention function has not malfunctioned (product liability).

Within the scope of the invention, a device is also proposed in which a sensor for continuously recording values of a change in distance between the sensor and the sensor measured during driving operation, means for comparing the values with corresponding reference values and means for evaluating the results the comparison of the values and the reference values based on parameters for the presence of a tendency of the vehicle to tip over are provided.

Compared to the prior art, the invention is distinguished in particular by the following advantages. On the one hand, the technical implementation of the invention does not require any additional sensors and is therefore associated with only relatively low additional costs. In addition, the stored values enable reproducible detection and detection of critical driving situations that can cause the vehicle to tip over. The lift-off sensor system also proposed in the context of the invention works in particular independently of the actual center of gravity of the vehicle. In addition, the proposed concept enables a sensation differentiating between a left and a right curve.

The further details of the invention will now be described below with reference to drawings. Show in detail 1 shows a section through a vehicle axle, in which an ABS wheel sensor prepared in accordance with the invention and EEPROM is provided for the intermediate storage of the sensor signals;

2a-d typical signal curves of a sensor according to the invention, measured on the front axle of a vehicle when driving through a curve with the stages straight ahead driving 2a, cornering 2b, cornering with lifting wheel 2c, straight ahead driving 2d;

3 is an illustration of reference bands with constant speed characteristics according to the invention;

Fig. 4 shows a driving situation shortly before a rollover (rollover) that is not "on road".

Known types of vehicles with anti-lock control systems are equipped with wheel sensors to record the wheel turning behavior. An example of such a wheel sensor will now be explained in more detail with reference to the sectional drawing shown in FIG. 1. These known sensors generally consist of a sensor wheel 10, 11 (measuring sensor) assigned to the wheel or magnetizable surface zones provided in the rubber of the tire and a measuring sensor 12, 13 (hereinafter referred to as "sensor") mounted at a small fixed distance for each individual wheel. which picks up the pulses generated by the sensor wheel and forwards them to a computing unit 14 (evaluation circuit). The speed of rotation of the wheel is in a fixed ratio to the pulse train measured in the sensor (frequency Measurement). The distance d of the sensor wheel and sensor (hereinafter referred to as "air gap") for each wheel based on tolerances influences the amplitude of the signal. In the case of, for example, an inductive coupling between the sensor wheel and the sensor, there is a fixed dependence of the signal amplitude of the induced signal on the rotational speed of the wheel.

If such a wheel is subjected to a transverse force (lateral force), this leads to an air gap change between the sensor and the sensor wheel (FIG. 1). The air gap now influences the useful signal emitted by the sensor in such a way that a narrowing air gap generates a larger signal amplitude (voltage, field), whereas a larger air gap results in a drop in the signal strength. This effect is used here in order to be able to sense transverse forces acting on the wheel via corresponding signal strength curves without a lateral force sensor.

The data recorded by means of the wheel sensor 12 13 are fed to a memory element 15, preferably a buffer memory. This buffer memory can be designed, for example, as EPROM (Erasable Programmable Read Only Memory) or as EEPROM (Electronically Erasable Programmable Read Only Memory). As a transit memory, it enables the continuous recording of sensor data, for example the data obtained over a period of preferably approximately one minute, but at least one second, whereby the data measured within the last minute is made available in the event of an accident.

Based on the sensor data stored in the EEPROM, even after an accident, it can still be clearly determined whether the accident occurred due to slipping and tipping over a curb or whether other causes were responsible.

When cornering with increasing speed, and thus also increasing lateral acceleration, the lateral force introduced increases continuously on the outer wheels due to the frictional forces (cornering forces) between the tires and the road surface, since in this case the road torque points to the vehicle (arrow 24). In the same situation, however, the lateral forces on the inner wheels initially increase, with the road moment pointing away from the vehicle (arrow 25), thus signaling cornering. However, the lateral forces drop again at a certain lateral acceleration, since the wheel then lifts and the lateral forces become zero. The characteristic course of the transverse forces mentioned thus makes it possible overall to differentiate between "curve detection" and "lift detection".

FIGS. 2a-d show the signal situations on the front axle of a front-wheel drive vehicle when driving through a narrow left curve with a sensor arrangement, as is shown schematically in FIG. For the sake of simplicity, it is assumed that the driving speed is relatively high when driving and is not reduced. It goes without saying that the signal curve when driving with increasing speed leads to an increase in amplitude and a rising frequency until the phase of almost constant speed shown in FIG. 2a is reached on the left and right wheels. The situation before the curve, the straight-ahead drive, is shown in FIG. 2a, in which the amplitude values on the left wheel tachometer L and on right wheel tachometer R are approximately the same height at constant speed. When driving through the left-hand curve, under quasi-steady-state considerations, values according to FIG. 2b result, according to which the amplitude on the left tachometer increases by dL and decreases on the right tachometer by dR. If the lateral force introduced on the outer wheels rises continuously, this leads to an increase in the amplitude according to FIG. 2c on the left-hand wheel on the inside of the curve, with an arrangement of the wheel sensors shown in FIG. 2c, due to a narrowing air gap until the wheel then lifts off. This leads to a maximum air gap d between the sensor and the sensor. The wheel-specific amplitude drops sharply by lifting dL. This drop or the characteristic change in the signal curve of the signal amplitude on the inner wheel serves to detect the lifting of the wheel. The wheel-specific amplitude of the outer right wheel decreases due to the lateral force introduced, since the road moment pointing towards the vehicle in the arrangement of the wheel sensors shown schematically in FIG.

These wheel-specific signal profiles are determined on each wheel of a vehicle, preferably having two axles and four wheels, and an evaluation of all wheel-specific parameters (comparison of the values with the reference values) and / or patterns indicates the tendency of the vehicle to tip over. A plausibility check can be carried out by evaluating preferably all, but at least of two wheel-specific signal curves, for example of a front wheel to the corresponding rear wheel, if the vehicle has vehicle-specific tipping properties. For example, B. due to vehicle-specific tilting properties the rear wheel in front of the front wheel and the individual signal curve senses the lifting of the front wheel, the countermeasures to be initiated are limited in their effect and / or further signal curves from other wheels, for example from the wheel arranged on the same axle, are used for evaluation. If a tendency to tip over is detected, countermeasures acting on the brakes are initiated.

FIG. 2d shows the state after passing the curve when the vehicle has been prevented from tipping due to the determined tendency to tip and the countermeasures initiated and the original amplitude state is restored. The relations dL / 1 and -dR / R are variables for the dynamic vehicle load and are evaluated by the electronic controller.

The signal profiles described above are dependent on the change in the distance between the sensor and the sensor, which changes due to the construction with the arrangement of the wheel sensors on the vehicle. For example, According to an embodiment not shown, the transducers are arranged opposite the transducers below the vehicle axis, so that the lifting of the inner wheel leads to a reduction in the air gap d. The amplitude rises sharply. This sudden increase in amplitude, which is dependent on the arrangement of the wheel sensors, then serves to detect the lifting of the wheel.

FIG. 3 shows three characteristic curves 16, 17, 19 for the constant (limit) speeds 5 km / h and 200 km / h and the speed 50 km / h above the air gap (abscissa) and the voltage (ordinate) of the sensor signal. As the air gap becomes smaller, ie with increasing lateral force, the voltage of the sensor signal increases. The sensor signal strengths are greater at higher speeds, at lower speeds smaller. The air gap for a wheel is indicated by d on the abscissa. Since the distance d (FIG. 1) between the transducer and the transducer, the sensor sensitivity and the like already has tolerances in quasi-steady-state viewing, which lead to further differences in each wheel when viewed dynamically due to the chassis properties of the vehicles and the like, a reference value or reference band becomes (eg 26) with the course identified by 21 or 22 or 23, for example, during a shear-free driving operation, which takes into account all wheel-specific operating states. In the case mentioned in FIG. 2c, the road gap on the left wheel, which points away from the vehicle, results in a reduction in the air gap d1 and thus a steady increase in the sensor signal strength Ul until the wheel is lifted off. The transverse forces introduced into the wheel become zero, the increasing air gap d2 leads to a characteristic drop in signal strength U2 at the moment of lifting, which cannot occur in uncritical situations (FIG. 3).

A computing unit 14 compares the values with the reference values or reference bands 26 and now assesses the parameters and / or patterns obtained in the comparison of the individual wheels with regard to a possible risk of tipping. The critical driving situation is recognized on the basis of threshold values or by comparative pattern recognition and braked on one or more wheels.

In order to calibrate the signal strengths individually for each wheel, taking into account the current operating conditions, i.e. to determine them individually for each wheel without lateral force, according to an advantageous embodiment of the invention, a signal strength reference or a signal strength reference band is determined with each ignition run and / or the existing ones Signal strength references or a signal strength reference bands updated. For example, the straight-ahead travel information (free of lateral force) provided by the tire tolerance comparison can be used to record reference values or reference bands (FIG. 3) and to create a corresponding characteristic curve.

If the parameters and / or patterns show “rollover” patterns as a function of the recorded reference values or reference bands, appropriate countermeasures to prevent tipping are initiated by an influencing unit 18. With regard to these countermeasures, full reference is made to the patent applications DE 198 30 189.8 and DE 198 30 190.1, which have been filed with the German Patent Office but have not yet been published.

Another field of application of the invention is the detection of a tipping that does not occur "on road" or has already occurred. If the vehicle "gets stuck" on an obstacle and overturns, this can be recognized by an abrupt, disproportionate signal curve. FIG. 4 shows the extreme signal value formation due to the transverse force curve. As shown, the amplitude increases continuously with increasing frequency (increasing speed) (26) and then changes to a steady course (27) when driving straight ahead (constant speed). If, after entering a curve with a decreasing amplitude (28) but constant speed and thus frequency of the signal value formation, the wheel "sticks" to an obstacle, an abrupt disproportionate increase in lateral force occurs, which is caused by the suddenly increasing distance between the measuring sensors 12 , 13 and the sensors 10, 11 is detected. The amplitude suddenly drops (29). This Detection is particularly necessary for insurance reasons, because in such situations a tipping prevention function can no longer stabilize the vehicle and therefore the vehicle manufacturer must provide proof that the tipping detection and its influencing device have not malfunctioned (product liability).

Claims

claims

1. A method for determining critical driving situations in vehicles which are in driving operation and which have on at least one wheel a measuring sensor which interacts with a sensor, by means of which measured values representing the driving behavior of the vehicle can be detected, characterized in that

that values which are based on changes in the distance between the measuring sensor and the measuring sensor are continuously recorded during driving operation with the measuring sensor,

that the values are compared with corresponding reference values, and

that conclusions are drawn from the comparison of the values and the reference values for the presence of a tendency of the vehicle to tip over.

2. The method according to claim 1, characterized in that the detected values of the change in distance and / or the parameters are temporarily stored in a memory.

3. The method according to claim 1 or 2, characterized in that the values of the change in distance are converted into state variables correlating with the change in distance and these are compared with corresponding reference values of the state variables.

4. The method according to any one of claims 1 to 3, characterized in that the reference values of the changes in distance during a shear-free driving operation are obtained as a function of the speed.

5. The method according to one or more of claims 1 to 4, characterized in that the comparison of the stored values and reference values is carried out by means of a pattern recognition.

6. The method according to any one of claims 1 to 4, characterized in that the comparison of the values with the reference values by means of pattern recognition and / or parameters on each wheel is carried out individually and concludes that the vehicle tends to tip over by evaluating all wheel-specific patterns and / or parameters becomes.

7. The method according to one or more of claims 1 to 6, characterized in that during a cornering of the vehicle, the tendency to tip over takes place on the basis of a wheel lift-off detection.

8. Device for determining critical driving situations in vehicles in driving operation, which have at least one wheel with a sensor (10, 11) interacting with a sensor (12, 13), by means of which the driving behavior of the vehicle can be measured, characterized by a measured value sensor (12, 13) for continuously recording values of a change in distance (d) measured between the measured value sensor (12, 13) and the measured value transmitter (10, 11) during driving,

Means (14) for comparing the values with corresponding reference values,

Means (14) for evaluating the results from the comparison of the values and the reference values based on parameters for the presence of a tendency of the vehicle to tip over.

9. The device according to claim 8, characterized by storage means (15) for temporarily storing the detected values of the change in distance and / or the parameters.

10. The device according to claim 8 and 9, characterized by a computing unit for recording reference values of the changes in distance during a shear-free driving operation depending on the speed.

11. The device according to claim 8 to 10, characterized by a computing unit for performing the comparison of the stored values and the reference values based on a pattern recognition.

12. The device according to one of claims 8 to 11, characterized by a computing unit for comparing the values with the reference values by means of pattern recognition and / or parameters on a wheel-by-wheel basis on each wheel and the evaluation of all wheel-specific patterns and / or parameters on a tendency of the vehicle to tip over.

13. The device according to one or more of claims 8 to 12, characterized in that the transducer provided on at least one wheel is a speed sensor having an air gap.

14. The device according to one or more of claims 8 to 13, characterized in that a buffer memory or a transit memory is provided as the storage means for temporarily storing the detected values of the change in distance and / or the parameters.