WO2008113533A2

WO2008113533A2 - Method for determining a change in direction of travel of a vehicle and control module therefor

Info

Publication number: WO2008113533A2
Application number: PCT/EP2008/002097
Authority: WO
Inventors: Nicolas Jecker; Oliver Eckstein
Original assignee: Valeo Schalter Und Sensoren Gmbh
Priority date: 2007-03-17
Filing date: 2008-07-09
Publication date: 2008-09-25
Also published as: WO2008113533A3; WO2008113533A9

Abstract

The invention relates to a method for determining a change in the direction of travel of a vehicle using a longitudinal acceleration signal and speed information based on wheel pulse signals, said method comprising the following steps: the standstill of the vehicle is determined from the speed information; the associated longitudinal acceleration value is determined when the vehicle is at a standstill, and stored as an acceleration reference value; a pre-defined speed threshold value is reached after the standstill, and the direction of travel of the vehicle is then determined from the current longitudinal acceleration signal in relation to the acceleration reference value. The invention also relates to a control module for carrying out said method.

Description

Title: Procedure for determining a

Change of direction of a vehicle and control module for this

description

The invention relates to a method for determining a direction of travel change of a vehicle and a control module for this.

The determination of the direction of travel of a vehicle is essential for modern vehicle systems. In particular, in collision warning systems, the direction of travel of the vehicle is decisive in order to drive the vehicle against obstacles to prevent or warn the driver in time.

Elaborate vehicles provide wheel pulse sensors, which can determine the direction of rotation of the wheels via a double head. For this purpose, a rotating encoder is provided on the rotating wheel, or on a rotor rotatably coupled to the wheel. This pulse generator is sequentially detected by the two adjacently arranged sensors of the double-head sensor. Knowing which head first detects the pulse generator, it can be deduced the direction of rotation of the wheel, and thus the direction of travel of the vehicle.

Simpler vehicle systems do not provide such sophisticated wheel pulse sensors with a dual head. To control a brake system, especially in ABS systems, it is sufficient to determine the rotational speed of the wheel, without requiring the direction of rotation.

The present invention is based on the object, the

Direction of travel of a vehicle to determine which no

Provides double-head sensors, with which the direction of travel can be deduced.

This object is achieved by a method having the features of claim 1. Such a method thus uses a longitudinal acceleration signal of a longitudinal acceleration sensor and a Speed information resulting from wheel pulse signals of a preferably single-head sensor. From the Radimpulssignalen, or due to the time interval between two signals, although it can be deduced the speed of the vehicle, but not the direction of travel of the vehicle. In order nevertheless to be able to determine the direction of travel of the vehicle reliably, the method according to the invention provides the following steps:

From the speed information, the stoppage of the vehicle is first determined. If no, Radimpulssignale generated or are no such Radimpulssignale before, can be deduced the stoppage of the vehicle. When the vehicle is stationary, the longitudinal acceleration value is then determined. The longitudinal acceleration value depends on the relative position of the vehicle to a horizontal plane. For example, if the vehicle is on a slope, it is

Longitudinal acceleration value due to gravitational force not zero. The longitudinal acceleration value at standstill of the vehicle is then stored as the acceleration reference value.

If the vehicle starts from a standstill and a predefined speed threshold value is reached via the wheel pulse signals, then the actual longitudinal acceleration signal relative to the acceleration reference value, or from its directional deviation, becomes Direction of travel of the vehicle determined. The use of the speed information resulting from the wheel pulses has the advantage that it is very accurate, especially at very low speeds. Even if speed information available from other speed measuring devices of the vehicle should be available, these are usually very inaccurate, especially at very low speeds. The fact that the respectively current longitudinal acceleration signal is considered relative to the acceleration reference value, the relative to a horizontal plane position of the vehicle is taken into account or does not distort the measurement result.

Overall, one arrives at a comparatively inexpensive, but nevertheless very reliable method for determining the direction of travel or a change of direction of a vehicle.

The predefined speed threshold value can in particular be stored as a fixed quantity and, in the case of motor vehicles, is preferably in the range from 0.2 to 0.8 km / h and advantageously in the range at 0.4 km / h.

The predefined speed threshold value can be selected such that a speed information stored on a vehicle bus system still indicates the value zero. In motor vehicles speed information is usually stored on a vehicle bus system, However, this is very inaccurate at very low speeds of the vehicle. This speed information usually indicates values above a speed of about 0.7 km / h. In this respect, it is advantageous if the predetermined speed threshold value according to the method according to the invention is below this value, namely in particular at 0.4 km / h.

The acceleration reference value is advantageously determined only when the vehicle is a predetermined period. In this way it can be ensured that a vibration behavior of the longitudinal acceleration signal does not distort the acceleration reference value. In general, a period of about 100 msec to 500 msec, and in particular in the range of 300 msec is sufficient.

Furthermore, it can be provided that the

Acceleration reference value is reset to "indeterminate" when the vehicle is traveling in one direction for a predetermined period of time and / or exceeding a predetermined speed. Resetting to indefinite has the advantage that a once defined acceleration reference value is not used again in a later standstill of the vehicle, in which the vehicle can take another relative to a horizontal plane relative position. Of the

Consequently, the acceleration reference value is then redetermined at each standstill. The method is of course very advantageous if the Radimpulssignale and the longitudinal acceleration signal are stored on a bus system of the vehicle. Since modern vehicles have wheel pulse signal sensors, in particular in the context of brake systems, this information is regularly available on vehicle bus systems. Furthermore, modern vehicles provide longitudinal acceleration sensors, which can be accommodated in particular in sensor clusters, together with other sensors, such as a lateral acceleration sensor and a yaw sensor. These sensor clusters are used in particular in vehicle stability systems. Relevant information is usually also stored on vehicle bus systems.

The object mentioned at the outset is also achieved by a control module which can be connected to a vehicle bus system for carrying out the method according to the invention, the control module, during operation, determining the respectively current speed information from wheel pulses stored on the vehicle bus system and reading out the respective longitudinal acceleration value from the vehicle bus system.

Further advantages and details of the invention will become apparent from the following description, with reference to which the embodiment of the invention shown in the figures is described and explained in more detail.

Show it: Figure 1 is a schematic representation of a control module for carrying out the method according to the invention; and

Figure 2 shows several signal sizes over time.

FIG. 1 shows a control module 10 with which the direction of travel of a vehicle can be determined. The control module 10 is connected to a bus system 12. It reads from the bus system 12 on the one hand Radimpulssignale R and on the other hand, a longitudinal acceleration signal L from. From the frequency of the Radimpulssignale, or from the time intervals of the adjacent Radimpulssignalen the control module 10 determines the vehicle speed, especially at very low vehicle speeds less than 2 to 3 km / h. From the thus determined vehicle speed and the longitudinal acceleration signal L, the control module 10 determines the direction of travel FR. This output signal FR of the control module 10 is supplied to a higher-level control module 12, the other input variables, which are exemplified with E2 and E3, also supplied.

The operation of the control module 10 will be described with reference to FIG 2. FIG. 2 shows, on the one hand, the vehicle speed V _R determined in module 10 on the basis of the wheel pulse signals. As can be seen from FIG. 2, this value v _{R is} at higher speeds relatively unstable. At low vehicle speeds, in the range of less than 2 km / h, this size is very accurate.

Furthermore, FIG. 2 shows the vehicle speed v _B present on the bus, which is very accurate at higher speeds. However, it is clear from FIG. 2 that this speed v _{B is} very inaccurate at very low vehicle speeds and at a value of about 0.7 km / h at time t -1 drops to zero at a value of about 0.7 km / h and only at a speed of 0 , 7 km / h of the vehicle at all indicates a measured value.

Furthermore, FIG. 2 shows the longitudinal acceleration signal L, which oscillates strongly when the vehicle is decelerating.

2, the acceleration reference value B _{R is} reproduced, which initially assumes a value of zero or indefinite and then makes a jump in the central region of the diagram t2. As a further waveform, the direction of travel FR is shown.

As becomes clear from FIG. 2, this oscillates

Longitudinal acceleration signal L when braking the vehicle. In the period to, the vehicle comes to a standstill because v _R assumes the value zero. Since the longitudinal acceleration signal L via a swinging out over a certain period of time, the value L only assumes a constant value in the region of the time ti. This value L is dependent on the relative position of the vehicle to a horizontal plane. Since the longitudinal acceleration signal regularly oscillates within a time period of less than 300 msec, the actual longitudinal acceleration value L is stored as acceleration reference value B _R in module 10 at t ₂ > t ₀ + (ti -t ₀ ) at a time t ₂ .

If the vehicle drives at the time t ₃ , the speed v _{R increases} from the time t ₃ . If the speed v _{R reaches} a predetermined threshold value S, the longitudinal acceleration signal L is considered at this time tή, in particular in which direction the longitudinal acceleration signal L deflects. From this, it is possible to deduce the direction of travel FR, wherein in the diagram shown in FIG. 2 a change in direction takes place according to the signal FR at the time tή.

In order to ensure that the acceleration reference value B _{R is} not used again at the next standstill of the vehicle, it can advantageously be reset to zero or indefinitely after reaching a vehicle speed or after a predetermined travel time.

Claims

claims

A method of detecting a change of direction of a vehicle using a longitudinal acceleration signal (L) and a wheel pulse signals (R) resulting

Velocity information (v _R ) according to the following steps:

- determine the standstill of the vehicle from the speed information;

- determine the associated longitudinal acceleration value (L) at standstill of the vehicle and deposit it as an acceleration reference value (B _R );

- If a predetermined speed threshold (S) is reached after standstill, then the direction of travel (FR) of the vehicle is determined from the relative to the acceleration reference value (B _R ) current longitudinal acceleration signal (L).

2. The method according to claim 1, characterized in that the predetermined speed threshold value (S) is stored as a fixed size.

3. The method according to claim 1 or 2, characterized in that the predetermined speed threshold value (S) is selected so that one on a vehicle bus system stored speed information (v _B ) still indicates the value zero.

4. The method of claim 1, 2 or 3, characterized in that the acceleration reference value (B _R ) is determined only when the vehicle is a predetermined period (ti - to).

5. The method according to at least one of the preceding claims, characterized in that the acceleration reference value (B _R ) is reset to indefinite when the vehicle is traveling in a direction for a predetermined period and / or exceeds a predetermined speed.

6. The method according to at least one of the preceding claims, characterized in that the Radimpulssignale (R) and the longitudinal acceleration signal (L) are deposited on a bus system (12) of the vehicle.

7. To a vehicle bus system (12) connectable control module (10) for performing the method according to at least one of the preceding claims, which determines in operation from stored on the vehicle bus system (12) wheel pulses (R) the respective current speed information (V _R ) and the respective longitudinal acceleration value (L) from the vehicle bus system (12) reads out.