DE102021213696A1 - Procedure for accurate odometry in brake slip - Google Patents

Abstract

The invention relates to a method for determining the position of a vehicle, in particular for correcting a vehicle speed and for correcting the wheel speeds. A simplified method for slip correction of a vehicle is to be provided, which can operate with less sensor data. According to the invention, the method comprises the following steps: a) recording speed signals from the wheels and calculating the speed changes, b) low-pass filtering of the speed signals, c) limiting to speed signals with a speed change below an acceleration threshold A2, d) calculating the vehicle speed change from the speed change of the fastest of the limited ones and filtered speed signals, e) wheel slip calculation from the difference between the unfiltered speed signal and the fastest limited, filtered speed signal, f) slip distance determination if the amount of the difference is above a limit value, g) calculation of the distance actually driven by the vehicle by adding the distance traveled of all not - slipping wheels, and adding a predetermined fraction of the calculated slip distances for each non-slipping wheel, and dividing this sum by the number of non-slipping wheels.

Description

The present invention relates to a method for determining the position of a vehicle, in particular for correcting a vehicle speed and for correcting the wheel speeds.

Out of DE 199 36 710 A1 a method for determining the vehicle speed using a vehicle dynamics system (ABS, anti-lock braking system) is known. This document aims to determine wheel slip under hard braking at the level of road grip.

There are several studies and methods in the literature for determining the wheel slip of a moving vehicle on the road. In most of these methods, however, other sensors are used in addition to the wheel speed sensors, which make the system even more complex, such as B. the Inertial Measurement Unit (IMU) and/or positioning sensors (e.g. GPS, Global Positioning Satellite) to use the acceleration data to determine how much the vehicle has actually moved and to calculate the wheel revolutions measured by the wheel speed sensors compare. Relevant basics are z. B. Described in Chris C. Ward and Karl Lagnemma, "Model-Based Wheel Slip Detection for Outdoor Mobile Robots", 2007 IEEE International Conference on Robotics and Automation.

The problem of in the DE 199 36 710 A1 The approach presented is that the torque induced at the wheels during braking must be known. This signal can be determined in a brake system. However, it is usually not available in a driver assistance system (also known as ADAS=Advanced Driver Assistance System). In order to determine the braking torque from the brake pressure, information about the dimension of the brakes is required, which is only available in the braking system. In addition, this algorithm determines the vehicle speed, while it is more important to know the actual distance traveled by the vehicle. This approach therefore requires greater networking of the vehicle systems and additional sensor information and is therefore relatively complex and not suitable for every combination of driver assistance system and braking system.

In autonomous driving and in particular in automated parking, vehicle odometry is a critical and essential component to locate the vehicle in the environment, and many other components depend on its accuracy (e.g. environmental modelling, computer vision, traction control, etc .). The job of the odometry component is to use the onboard sensors (wheel speed sensors, inertial sensors, GPS, etc.) to estimate the amount of vehicle movement and rotation with the accuracy required by the user components. One of the requirements of odometry is to accurately determine the movement and rotation of the vehicle even under different environmental conditions (e.g. snow, icy roads, etc.). At the same time, it is desirable, albeit with a limited amount of sensor information (e.g. for vehicles with a basic equipment, i.e. fewer sensors) and / or in the event of failure of one or more of the additional sensors (inertial measuring devices, GPS, braking data from the braking system, etc.), a satisfactory one Position determination by the driver assistance system is possible.

A problem for reliable attitude determination from wheel speed sensors alone is the detection of wheel slip while the vehicle is slowed down either by hard braking or on low-friction roads at the limit of road grip. This phenomenon degrades the accuracy of the odometry as the wheel rotation is not realistic compared to the actual vehicle motion. As a result, one or more wheels lose traction temporarily and may move faster (under low friction) or slower (under heavy braking) than would be expected based on the vehicle's actual distance travelled.

The object of the invention is to provide a method for determining and correcting wheel slip that is as simple as possible.

1. a) Aufzeichnen von Geschwindigkeitssignalen der Geschwindigkeitssensoren mehrerer Räder des Fahrzeugs und Berechnen der Geschwindigkeitsänderungen für jedes Geschwindigkeitssignal,
2. b) Anwenden einer Tiefpassfilterung auf die einzelnen Geschwindigkeitssignale der Räder um Rauschen in den Signalen mit Geschwindigkeitsänderungen oberhalb einer ersten Beschleunigungsschwelle A₁ herauszufiltern und gefilterte Geschwindigkeitssignale zu erhalten,
3. c) Limitieren auf solche der gefilterten Geschwindigkeitssignale, deren Geschwindigkeitsänderung sich unterhalb einer zweiten Beschleunigungsschwelle A₂ befindet,
4. d) Berechnen der Fahrzeuggeschwindigkeitsänderung aus der Geschwindigkeitsänderung des schnellsten der limitierten und gefilterten Geschwindigkeitssignale,
5. e) Berechnen des Radschlupfes jedes Rades durch Differenzbildung zwischen den jeweiligen ungefilterten, unlimitierten Geschwindigkeitssignal und dem Geschwindigkeitssignal des schnellsten der limitierten, gefilterten Geschwindigkeitssignale,
6. f) Bestimmen, für jedes der Räder, dass das Rad schlupft, wenn der Betrag der jeweiligen in e) gebildeten Differenz über einem Grenzwert liegt, und wenn nein, Berechnen einer zurückgelegten Schlupfstrecke für jedes nicht schlupfende Rad,
7. g) Berechnen der tatsächlich gefahrenen Strecke des Fahrzeugs durch:
   • - Addieren der zurückgelegten Strecke aller Räder, die nicht als schlupfend bestimmt wurden, und
   • - Addieren eines vorgegebenen Bruchteils der berechneten Schlupfstrecken für jedes nicht als schlupfend bestimmte Rad, und
   • - Dividieren dieser Summe durch die Anzahl der nicht-schlupfenden Räder.

According to the invention, a method of the type mentioned is provided, comprising the following steps:

1. a) recording speed signals from the speed sensors of several wheels of the vehicle and calculating the speed changes for each speed signal,
2. b) applying low-pass filtering to the individual speed signals of the wheels in order to filter out noise in the signals with speed changes above a first acceleration threshold A ₁ and to obtain filtered speed signals,
3. c) Limiting to those of the filtered speed signals whose change in speed is below a second acceleration threshold A ₂ ,
4. d) calculating the vehicle speed change from the speed change the fastest of the limited and filtered speed signals,
5. e) calculating the wheel slip of each wheel by forming the difference between the respective unfiltered, unlimited speed signal and the speed signal of the fastest of the limited, filtered speed signals,
6. f) determining, for each of the wheels, that the wheel is slipping if the amount of the respective difference formed in e) is above a limit value, and if not, calculating a slip distance covered for each non-slipping wheel,
7. g) calculating the actual distance traveled by the vehicle by:
   • - summing the distance traveled of all wheels not determined to be slipping, and
   • - adding a predetermined fraction of the calculated slip distances for each wheel not determined to be slipping, and
   • - Divide this sum by the number of non-slipping wheels.

The method according to the invention aims to improve the accuracy of the vehicle odometry in a simple manner (that is to say with fewer sensors), particularly in driving situations in which the vehicle is braked at the limit of road adhesion or road adhesion is reduced for other reasons. This can be the case either with heavy braking or with low friction of the road surface (e.g. due to leaves, water, ice, etc.). The wheels can be braked into slip, meaning they rotate slower than would be expected at vehicle speed. At the same time, they are individually modulated by the anti-lock braking system (ABS). Taking into account the wheel speed of the wheels with strong slip when determining the distance covered leads to a deterioration in the accuracy of the vehicle odometry.

The solution according to the invention now proposes a simple method for identifying wheels with strong slip and for temporarily not including their associated route in the route calculation. At the same time, however, the other wheels also regularly exhibit slight slip, particularly in braking situations, which also falsifies the measured distance compared to the distance actually covered. Therefore, according to the invention, a predetermined fraction of the slip distances calculated for these wheels is added for those wheels that are not determined to be (strongly) slipping. The inventors have found that this procedure can be used to approximately determine the route actually covered with good accuracy. In contrast to the prior art, no data from the braking system or additional sensor data such as from inertial sensors or GPS are required. The method is therefore suitable both for the simplest and most cost-effective driver assistance systems possible and as redundancy for more complex systems, e.g. B. to bridge a sensor failure.

The method is primarily aimed at four-wheeled vehicles such as passenger cars, but can in principle also be used for vehicles with a different number of wheels. References to the front wheels / rear wheels are therefore to be understood as illustrative and not restrictive.

The method is preferably carried out iteratively at fixed time intervals, e.g. B. every 5-20 ms, which can also correspond to the sampling rate of the wheel speed sensors. At least the previously measured speed value of the respective wheel is used for the calculation of speed changes/accelerations.

First, in step b), the wheel speed signals are filtered in order to reduce the measurement noise. The time constant of the filter is chosen in such a way that unphysically high speed changes are filtered out, but speed changes that could be related to wheel slip are retained. As a result, the method can be made considerably more reliable.

In the next step c), the filtered speed signals whose speed change is below a second acceleration threshold A ₂ are limited (limited). This occurs because a typical road vehicle cannot decelerate or accelerate more than a certain amount of acceleration. If the wheel speed is changing more rapidly, this must be due to wheel slip (where the filtering has already removed potential signal noise). In the following, limited speed signals are therefore speed signals that are below the second acceleration threshold.

In step d), the fastest wheel is searched for among the filtered and limited speed signals. This is the wheel with the least amount of slip and is the best choice for determining actual vehicle speed.

In e) it is calculated how large the wheel slip of each wheel is by forming the difference between the respective unfiltered, unlimited speed signal and the speed signal of the fastest of the limited, filtered speed signals.

Finally, in step f) it is determined for each of the wheels that the wheel is slipping if the amount of the respective difference formed in e) is above a limit value, and if not, a slip distance covered is calculated for each non-slipping wheel. This ensures that no signal noise or small deviations in the wheel speeds are identified as relevant slip, but only slip of a relevant magnitude. As described above, the wheels determined to be non-slip also regularly exhibit slight slip (especially in braking situations).

Finally, using the data determined in the previous steps, in step g) the actual distance traveled by the vehicle is calculated by adding the distance traveled for all wheels not determined to be slipping and adding a predetermined fraction of the calculated slip distances for each wheel not determined to be slipping wheel, and dividing this sum by the number of non-slipping wheels. The inventors have found that the actual distance traveled by the vehicle can be approximated fairly accurately by calculating a corrected average of the distance traveled for all non-slipping wheels which are (at least in some situations, more on that later) a fraction of the calculated slipping distances of the non-slipping wheels is included. The heavily slipping wheels are therefore not included in the calculation and at the same time a correction for the slight slippage of the other wheels (not determined as slipping) is calculated.

It is preferred if in step g) the specified fraction of the calculated slip distances is between 4% and 20%, preferably between 7% and 15%, particularly preferably about 8%. If the vehicle is braked but none of the wheels are slipping, this is an indication that the grip level has not been reached. However, hard braking slip can still occur, which is still below the grip level. This slippage can already affect the accuracy of vehicle odometry since the wheels are already turning slower than the vehicle is moving. Here "high friction" is assumed and a linear characteristic of the corresponding µ-slip curve is used. The µ-slip curve of the current road friction cannot be selected, since in general neither the road surface nor the braking force is known. However, for simplification, a linear characteristic can be assumed and slip becomes a linear function of deceleration. Roughly approximated, the slip at 10 m/s ² is about 8% and at 5 m/s ² 4% with these simplifying assumptions. If one of the wheels is slipping, the grip level limit should be reached. If 10 m/s ² is assumed to be the maximum practical braking acceleration, this results in a predetermined fraction of about 8% for the slip correction. This slip is added to the individual wheel displacements of the non-slipping wheels. However, an improvement in the odometry can also be achieved in a broader range of parameters.

In the context of this application, "about" z. B. be understood that a deviation of ± 10% from the stated value should still be included.

Preferably, after step c), the following steps are performed: c1) determining that a wheel is braked if the speed of a filtered and limited speed signal decreases, and c2) determining that the vehicle is braked if more in step c1). when two wheels were determined to be braked. If the wheel speed gets slower and slower in the subsequent time steps of the algorithm, the wheel is considered to be braked. If at least two wheels slow down, the entire vehicle is deemed to have braked. In the following, this is important in order to recognize and differentiate between wheel spin when accelerating and brake slip.

Alternatively, the determination that the vehicle is being braked is made by information obtained from the brake system. The information can be obtained directly or indirectly from the braking system. For example, the activation of the vehicle's brake light switch or the information about a measured brake pressure above a limit value, which is generated by the brake pedal or a braking assistance function, can be evaluated.

• h) Berechnen der tatsächlich gefahrenen Strecke des Fahrzeugs durch:
  • - Addieren der zurückgelegten Strecke aller limitierten Räder, und
  • - Dividieren dieser Summe durch die Anzahl aller limitierten Räder.

In one embodiment, steps e), f) and g) will only be performed if it has been determined that the vehicle is being braked, and in a otherwise

• h) calculating the actual distance traveled by the vehicle by:
  • - adding up the distance traveled by all limited bikes, and
  • - Divide this sum by the number of all limited bikes.

If a braking situation is detected, the method according to the invention is carried out as described in steps eg). However, if no clear braking situation is determined (e.g. slip when accelerating or slip of the wheels in general due to poor road grip), it has been found that it is most advantageous to only calculate those wheels whose speed change is above the second acceleration threshold calculated from the distance actually traveled by the vehicle and not to undertake any additional slip correction as in step g).

• a1) Aufzeichnen eines Hinterachsen-Geschwindigkeitssignals in der Mitte einer Fahrzeug-Hinterachse sowie mindestens eines Einschlagwinkels der Vorderräder,
• a2) Berechnen eines normierten Geschwindigkeitssignals für jedes der Räder aus den gemessenen Geschwindigkeitssignalen und dem Hinterachsen-Geschwindigkeitssignal sowie mindestens einem Einschlagwinkel der Vorderräder, sodass Unterschiede in der gefahrenen Strecke der Räder aufgrund einer Kurvenfahrt des Fahrzeugs reduziert werden.

According to step a), standardized speed signals of the wheels are preferably used in the entire method, which are calculated as follows from the measured speed signals of the wheels:

• a1) recording a rear axle speed signal in the center of a vehicle rear axle and at least one steering angle of the front wheels,
• a2) Calculating a normalized speed signal for each of the wheels from the measured speed signals and the rear axle speed signal and at least one steering angle of the front wheels, so that differences in the distance traveled by the wheels due to cornering of the vehicle are reduced.

While the vehicle is cornering, the wheel speeds are different because the wheels are turning on different radii of the curve. The wheel on the outside of the curve spins faster than the wheel on the inside of the curve. If this is not corrected, wheel slip could be incorrectly detected. For this reason, the wheel speed of the individual wheels is normalized to the corresponding speed at the center of the rear axle. Corrections of this kind to the wheel speeds in curves are known in principle to those skilled in the art and can be carried out in various ways (with varying degrees of accuracy). This is explained in detail with reference to 2 explained in more detail later. However, this embodiment synergistically improves the accuracy of the method according to the invention, since the detection of slip is much more reliable if this source of wheel speed difference is eliminated (or reduced).

In one embodiment, the low-pass filtering uses a PT1 filter, which preferably has a time constant T of 0.05 s<T<0.01 s, particularly preferably about T=0.02 s. A PT1 filter (also called a PT1 element) is known in control engineering as a simple low-pass filter and is completely sufficient for the relatively coarse noise filtering required here for filtering out extremely fast changes in speed, which can practically only be attributed to noise.

The first acceleration threshold A ₁ is preferably in the range of 50 m/s ² <A ₁ <200 m/s ² , particularly preferably around 100 m/s ² . The fact that speed changes above such a first acceleration threshold A ₁ are filtered out is to be understood here and also more generally in such a way that, for example, such high-frequency signal components are suppressed by at least 10 db, preferably by at least 20 db, particularly preferably by at least 30 db, by the low-pass filtering for frequency components is, which correspond to changes in speed above the first acceleration threshold A ₁ .

It is preferred if the second acceleration threshold A ₂ is in the range of 8 m/s ² <A ₂ <12 m/s ² , particularly preferably around 10 m/s ² . Accelerations that a car can carry out with full road grip usually end in this range, and higher accelerations of a wheel are therefore usually due to slippage of the corresponding wheel.

The invention also relates to a driver assistance system that is set up to carry out a method according to one of the above embodiments. For this purpose, the driver assistance system can include corresponding software or firmware, which carries out such a method when it is executed. However, it is also conceivable to integrate an application-specific integrated circuit into the driver assistance system, which is set up to carry out the method according to the invention.

The characteristics, features and advantages of the present invention described above, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in connection with the drawings.

• 1 ein beispielhaftes Flussdiagramm eines erfindungsgemäßen Verfahrens,
• 2 eine schematische Darstellung der Radgeschwindigkeitskorrektur bei Kurvenfahrt.

Show it:

• 1 an exemplary flowchart of a method according to the invention,
• 2 a schematic representation of the wheel speed correction when cornering.

In 1 an embodiment of a method according to the invention is shown. When a time step (call, iteration, etc.) of the method is started, one runs first for each wheel Loop starting at step 100 and ending at step 140 until the loop is completed for all wheels.

In step 100, the speed signal of the associated speed sensor is recorded for the respective wheel.

In step 110, a rear axle speed signal is then recorded in the center of a vehicle rear axle and at least one steering angle of the front wheels, and a normalized speed signal for the wheel is calculated from the measured speed signal and the rear axle speed signal and at least one steering angle of the front wheels, so that differences in the traveled distance of the wheels can be reduced due to cornering of the vehicle.

In step 120, low-pass filtering is applied to the single normalized wheel speed signal to filter out noise in the signal with speed changes above a first acceleration threshold A ₁ (e.g. 100 m/s ² ) and obtain a filtered (normalized) speed signal.

In step 130, the filtered speed signals are limited to those whose speed change is below a second acceleration threshold A ₂ (eg 10 m/s ² ).

In step 140 it is determined that a wheel is braked if the speed of the filtered and limited speed signal is decreasing. A comparison is made here with at least one previous speed value of the same wheel in order to calculate the change in speed for the corresponding wheel from the time profile of the speed signal. Wheels whose speed change is above A ₂ are therefore not determined as being braked.

When the 100-140 loop is completed for all wheels, in step 150 the fastest wheel is searched for among the normalized and filtered speed signals. Here too, in step 160, a limitation is made to those wheels whose speed change is below A ₂ . Then, in step 170, the vehicle acceleration (or deceleration) is calculated from the velocity change of the fastest of the limited, filtered, and normalized wheels, since this regularly best represents the actual acceleration of the vehicle.

In step 180 it is then determined that the vehicle as a whole is decelerating if more than two wheels were determined to be braking in step 140 of the respective loop.

From 190 to 240/250, a loop runs over all wheels again, which mainly differs in whether it was determined in step 180 whether the vehicle is braking or not. If it was not determined that the vehicle is braking, then in step 200 for all limited wheels (speed change <A ₂ ) to calculate the distance actually driven by the vehicle, the distance of the respective wheel resulting from the filtered and normalized wheel speed is added and in step 260 divided by the number of these limited wheels to calculate an average actual distance traveled by the vehicle (excluding wheelspin).

If, on the other hand, it is determined in step 180 that the vehicle is braking, a correction is made in loop 190 to 240/250 in order to take account of the slip contributions to the distance traveled in the event of heavy braking. In step 210, the wheel slip is then determined for each wheel by forming the difference between the respective unfiltered (but normalized) speed signal and the speed signal of the fastest of the limited, filtered (and normalized) speed signals.

In step 220 it is then determined, for each of the wheels, that the wheel is slipping if the amount of the respective difference formed in step 210 is above a limit value.

In step 230, a distinction is then made for each wheel as to whether it was determined as slipping in step 220 and, if not, the entire wheel travel distance is calculated from the normalized and filtered wheel speed and added to calculate the actually traveled distance of the vehicle. Then, for each wheel not determined to be slipping, a predetermined fraction (e.g., 8%) of the slip distance calculated for that wheel (in step 210) is further added to calculate the vehicle's actual travel distance. The sum of wheel travel contributions thus obtained is then divided by the number of non-slipping wheels in step 260 to calculate an average actual distance traveled by the vehicle (with reduced inclusion of the slipping wheels).

In 2 a vehicle 1 with wheels 2, 3, 4, 5 is shown schematically from above in order to explain a possible way of correcting the wheel speed when cornering as described in step 110. As can be seen, the wheels 2, 3, 4, 5 cover different travel paths when cornering and therefore also have different travel paths Speeds, all of which differ from vehicle speed.

To correct the wheel speeds, a virtual front wheel angle α _c , ie the wheel angle of a virtual central wheel 6 , is determined from the steering wheel angle, ie the current steering wheel position. For this purpose, this determination uses a characteristic conversion curve, since the gear ratio depends on the steering wheel angle. In this case, the transmission ratio is greater for smaller steering wheel angles than for large steering wheel angles.

The wheel angles α _FR , α _FL of the two front wheels 2, 4 are now calculated from this virtual front wheel angle α _c together with the track width of the rear axle tw _rear and the wheelbase W, using the formula $${\mathrm{a}}_i={\text{tan}}^{-1}\left(\frac{1}{\frac{1}{\text{tan}\left(\left|a_c\right|\right)}\pm \frac{t{w}_{\mathrm{right}ea\mathrm{right}}}{W\cdot 2}}\right)$$

The plus sign applies to the front wheels and the minus sign to the rear wheels. The indices FL (front left), FR (front right), RL (rear left) and RR (rear right) each refer to one of the wheels 2, 3, 4, 5.

$${\kappa }_{FR}=\frac{\text{sin }{\alpha }_{FR}}{W}$$

$${\kappa }_{RL}=\frac{\text{tan }{\alpha }_{FL}}{W}$$

$${\kappa }_{RR}=\frac{\text{tan }{\alpha }_{FR}}{W}$$

$${\kappa }_C=\frac{\text{tan }{\alpha }_C}{W}$$

From these angles, the curvatures k _FL , k _FR , _' k _RL , k _RR , x _C of the individual movement paths of the wheels 2, 3, 4, 5 and the virtual movement path of the central wheel 6 can be calculated with: $$k_{fL}=\frac{\text{sin}{a}_{fL}}{W}$$

$$k_{fR}=\frac{\text{sin}{a}_{fR}}{W}$$

$$k_{RL}=\frac{\text{tan}{a}_{fL}}{W}$$

$$k_{RR}=\frac{\text{tan}{a}_{fR}}{W}$$

$$k_C=\frac{\text{tan}{a}_C}{W}$$

$$k_{FR}=\frac{{\kappa }_{FR}}{{\kappa }_C}$$

$$K_{RL}=\frac{{\kappa }_{RL}}{{\kappa }_C}$$

$$k_{RR}=\frac{{\kappa }_{RR}}{{\kappa }_C}$$

Curve factors k _i can now be calculated from this, which result from: $$k_{fL}=\frac{k_{fL}}{k_C}$$

$$k_{fR}=\frac{k_{fR}}{k_C}$$

$$K_{RL}=\frac{k_{RL}}{k_C}$$

$$k_{RR}=\frac{k_{RR}}{k_C}$$

The curve factors k _i indicate conversion factors with which the angular speeds ω _i of the individual wheels 2 , 3 , 4 , 5 are converted to a corresponding angular speed of the virtual central wheel 6 . As a result, the differences in the angular velocities that can be attributed to cornering are calculated out of the measured values.

$$v_{whl,norm,FR}=k_{FR}\cdot v_{whl,FR}$$

$$v_{whl,norm,RL}=k_{RL}\cdot v_{whl,RL}$$

$$v_{whl,norm,RR}=k_{RR}\cdot v_{whl,RR}$$

From this, the wheel speeds v _whl,norm,i normalized to the reference point result from the measured wheel speeds v _whl,i via: $$v_{wHl,nO\mathrm{right}m,fL}=k_{fL}\cdot v_{wHl,fL}$$

$$v_{wHl,nO\mathrm{right}m,fR}=k_{fR}\cdot v_{wHl,fR}$$

$$v_{wHl,nO\mathrm{right}m,RL}=k_{RL}\cdot v_{wHl,RL}$$

$$v_{wHl,nO\mathrm{right}m,RR}=k_{RR}\cdot v_{wHl,RR}$$

Although the present invention has been illustrated and described in detail by preferred embodiments, it is not limited by the disclosed examples.

Reference List

100

Step

110

Step

120

Step

130

Step

140

Step

150

Step

160

Step

170

Step

180

Step

190

Step

200

Step

210

Step

220

Step

230

Step

240

Step

250

Step

260

Step

A1

first acceleration threshold

A2

second acceleration threshold

T

time constant

1

vehicle

2

wheel

3

wheel

4

wheel

5

wheel

6

virtual wheel

W

center distance

αFL

angle

αFR

angle

αC

angle

twrear

Rear axle track width

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 19936710 A1 [0002, 0004]

Claims (10)

Method for determining the position of a vehicle (1), in particular for correcting a vehicle speed and for correcting the wheel speeds, comprising the following steps: a) recording speed signals from the speed sensors of a plurality of wheels (2, 3, 4, 5) of the vehicle (1) and calculating of the speed changes for each speed signal, b) applying low-pass filtering to the individual speed signals of the wheels (2, 3, 4, 5) in order to filter out noise in the signals with speed changes above a first acceleration threshold A ₁ and to obtain filtered speed signals, c) limiting to those of the filtered speed signals whose speed change is below a second acceleration threshold A ₂ , d) calculating the vehicle speed change from the speed change of the fastest of the limited and filtered speed signals, e) calculating the wheel slip of each wheel (2, 3, 4, 5) by subtraction between the respective unfiltered speed signal and the speed signal of the fastest of the limited, filtered speed signals, f) determining, for each of the wheels (2, 3, 4, 5), that the wheel (2, 3, 4, 5) is slipping if the The amount of the respective difference formed in e) is above a limit value, and if not, calculating a slip distance covered for each non-slip wheel (2, 3, 4, 5), g) calculating the distance actually traveled by the vehicle (1) by: - adding up the distance traveled for all wheels (2, 3, 4, 5) not determined to be slipping, and - adding a predetermined fraction of the calculated slip distances for each wheel (2, 3, 4, 5) not determined to be slipping, and - dividing this sum by the number of non-slipping wheels (2, 3, 4, 5). procedure after claim 1 , wherein in step g) the predetermined fraction of the calculated slip distances is between 4% and 20%, preferably between 7% and 15%, particularly preferably about 8%. procedure after claim 1 or 2 , wherein after step c), the following steps are performed: c1) determining that a wheel (2, 3, 4, 5) is braked if the speed of a filtered and limited speed signal decreases, and c2) determining that the vehicle (1) braking is applied if more than two wheels (2, 3, 4, 5) were determined to be braked in step c1). A method according to any one of the preceding claims, wherein the determination that the vehicle (1) is being braked is made by information obtained from the braking system. A method as claimed in any one of the preceding claims, wherein steps e), f) and g) are performed only if it has been determined that the vehicle (1) is being braked, and in a otherwise h) calculating the distance actually traveled by the vehicle (1) by: - adding up the distance traveled by all limited bikes, and - Divide this sum by the number of all limited bikes. Method according to one of the preceding claims, wherein after step a) normalized speed signals of the wheels (2, 3, 4, 5) are used throughout the method, which are calculated as follows from the measured speed signals of the wheels (2, 3, 4, 5). : a1) recording a rear axle speed signal in the center of a vehicle rear axle and at least one steering angle (α _FL , α _FR ) of the front wheels (2, 4), a2) calculating a normalized speed signal for each of the wheels (2, 3, 4 , 5) from the measured speed signals and the rear axle speed signal as well as at least one steering angle (α _FL , α _FR ) of the front wheels (2, 4), so that differences in the distance traveled by the wheels (2, 3, 4, 5) due to a Cornering of the vehicle (1) can be reduced. Method according to one of the preceding claims, wherein the low-pass filtering uses a PT1 filter, which preferably has a time constant T with 0.05 s < T < 0.01 s, particularly preferably about T = 0.02 s. Method according to one of the preceding claims, wherein the first acceleration threshold A ₁ is in the range 50 m/s ² < A ₁ < 200 m/s ² , particularly preferably around 100 m/s ² . Method according to one of the preceding claims, wherein the second acceleration threshold A ₂ is in the range 8 m/s ² < A ₂ < 12 m/s ² , particularly preferably around 10 m/s ² . Driver assistance system that is set up to carry out a method according to any one of the preceding claims.

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