WO2008003530A1 - Method and device for determining the direction of travel of a vehicle - Google Patents

Abstract

The invention relates to a method for determining the direction of travel of a vehicle and a corresponding device. According to the invention, a rapid and reliable method and corresponding device for recognising the direction of travel of a vehicle can be achieved, wherein at least two wheel rotational speeds are analysed to determine the wheel speeds ( <SUB>V</SUB>

Description

Method and device for determining the direction of travel of a vehicle

The present invention relates to a method for determining the direction of travel of a vehicle and to a corresponding device.

According to known from the prior art method for determining the direction of travel of a vehicle is based on an i.d.R. continuously measuring a yaw rate, the behavior of the yaw rate is usually compared with a reference value calculated from the values of the wheel speeds. If the yaw rates differ by a factor of -1, the vehicle detects reversing. If the measured and calculated yaw rate differs by a factor of +1, that is, not at all, forward travel is detected. However, the reliable detection of the factor +1 or -1 is only possible with a certain time delay, which depends essentially on a respective driven curve radius. A secure detection can thus take any length, when the vehicle is driving straight ahead.

It is therefore an object of the present invention to provide a fast and reliable method and a corresponding device for detecting a direction of travel of a vehicle.

This object is solved by the features of the independent claims. Advantageous developments are the subject of the respective dependent claims.

According to the invention, a method for determining the direction of travel of a vehicle is characterized in that at least two wheel speeds correlated with a slow acceleration sensor or, alternatively, a pitch rate sensor are analyzed to output conditions on the basis of which Direction of travel decision is made according to a state diagram.

Accordingly, a device for determining the direction of travel of a vehicle is characterized in that at least two wheel speed sensors and a slow acceleration sensor or alternatively a pitch rate sensor are connected to a correlation logic, the logic for determining a direction of travel by evaluating from the Ausgangssigna- len derived or specific conditions based on a stored in the logic state diagram is formed.

In one embodiment of the invention, it is preferred that the acceleration sensor is arranged to measure a positive value at an acceleration directed in the vehicle longitudinal direction. In an alternative embodiment of the invention, it is preferred that the pitch rate sensor is arranged so that it assumes a positive value when nodding forward.

A basis for the decision making about the direction of travel is a state diagram in which it is only allowed to change between the states on the basis of well-defined conditions. The allowed vehicle states are

• +1, which indicates a forward-directed trip,

• 0, which indicates an undefined state (standstill) and

• -1, which indicates a return-oriented trip.

mit den vorhandenen Raddrehzahlen y , V₂ und einer aus den Raddrehzahlen erhaltenen Referenzgeschwindigkeit γ^j des Fahrzeugs. Die Große der Referenzgeschwin- digkeit y| des Fahrzeugs zu einem j-ten Zeitschritt ist zu nutzen, wenn alle Rader blockieren und somit einen falschlichen Stillstand vortauschen. Das Fahrzeug beginnt sich genau dann an einem j-ten Zeitschritt zu bewegen, wenn die Bedingung

gegenüber einem vorangehenden Zeitpunkt j-1 erfüllt ist. Für diesen Zeitpunkt j wird eine erste zeitliche Ableitung der angemessen gefilterten Langsbeschleunigung a_x ausgewertet. Dabei kann zur Rauschunterdruckung ein Filter erster Ordnung verwendet werden. Ist genau in diesem Zeitpunkt die erste zeitliche Ableitung der so behandelten Langsbeschleunigung a_x

positiv, dann erfahrt das Fahrzeug einen Beschleunigungsimpuls in die Vorwartsrichtung, was auf eine anschließende Vor- wartsfahrt schließen lasst. Ist der Beschleunigungsimpuls zu diesem Zeitpunkt negativ, dann liegt eine ruckwartsgerichtete Fahrtrichtungsanderung vor.A fundamental feature of a method according to the invention is that a transition from 0 to +1 or -1 occurs precisely when the vehicle is just starting to move. This limit is given by the fact that a minimum measurable speed y is exceeded. For this purpose, a vehicle speed to be compared at a j-th time step is defined by

with the existing wheel speeds y, V ₂ and a reference speed γ ^{j of} the vehicle obtained from the wheel speeds. The magnitude of the reference velocity y | of the vehicle at a j-th time step is to be used if all the wheels block and thus interchange a false standstill. The vehicle begins to move at a j-th time step if and only if the condition

is satisfied with respect to a previous time j-1. For this time j, a first time derivative of the appropriately filtered longitudinal acceleration a _{x is} evaluated. In this case, a filter of the first order can be used for noise suppression. Is exactly at this time the first time derivative of the thus treated longitudinal acceleration a _x

positively, then the vehicle experiences an acceleration impulse in the forward direction, which suggests a subsequent forward drive. If the acceleration pulse is negative at this time, then there is a reverse direction change in direction.

An important advantage of this method over those which analyze the longitudinal acceleration is that the temporally derived slow acceleration signal is independent of existing offsets and gravitational contributions. Alternatively, it is possible to conclude a subsequent forward drive, or reverse drive, if in the j th time step defined above the pitch rate (Q ^{j is} negative or positive.

If the acceleration pulse or the pitch rate is not sufficiently pronounced to be able to make a decision, then a prior art method cited above, used to perform an additional plausibility check for a transition from 0 to +1 or -1.

In the following, the secure detection in an embodiment of the invention using the yaw rate signal is to be expressed in that the measured yaw rate φ ^es either against the calculated Gxerrate φ or the negative of the

CaIc. Meas calculated yaw rate -Q) is convergent _2, ie, Q} _Z -> + CO ^aC • The yaw rate may be calculated from the wheel speeds of a shaft and / or optionally a steering wheel angle detected in one embodiment of the invention with its own sensor.

A transition from +1 or -1 back to 0 occurs when the

Vehicle again comes to a stop, ie whenever the Bool.statmnt ^{J J} ung ΛV / ^J max <VV mm successful ^J t.

A direct transition between the states +1 and -1 can occur if the detected state appears implausible. Such a transition may occur when the vehicle makes a spin-induced directional change without stalling.

oder wenn die gemessene Gierrate gegen die berechnete Gierra- te konvergiert,In one embodiment of the invention, the transition from -1 to +1 is made when the wheel speeds reflect a vehicle speed that is greater than the maximum possible reverse vehicle speed of the vehicle,

or when the measured yaw rate converges to the calculated yaw rate,

Mca CaIc ω _z - ^> + co _z •

und zugleich die Fahrzeuggeschwindigkeit kleiner als die maximal mögliche Ruckwartsfahrtgeschwindigkeit ist, 'ref ^;v_ref A transition from +1 to -1 occurs when the measured yaw rate converges to the negative of the calculated yaw rate

and at the same time the vehicle speed is less than the maximum possible return travel speed, 'ref ^; v _ref

In this way, a method according to the invention makes it possible to reliably and quickly recognize a respective driving direction state, irrespective of a particular driving situation. Since many wheel speed sensors indicate only the amount, but not the direction of the speed of a wheel, the additional information obtained is of great interest for all functions that depend on the current direction of travel. A delay in detection is given only by the filter used to calculate the derivative of slow acceleration with noise cancellation. This time delay is erfmdungsgemaß in a range of only 100 ms to 500 ms, even when using standard sensors. Furthermore, spin-induced directional changes of the vehicle in question can be detected.

Further features and advantages of the invention will be given below with description of an exemplary embodiment with reference to the figure of the drawing. In the

Drawing shows the figure a complete state diagram of a method according to the invention. Within this state diagram, the major players involved, which are only partially referred directly to corresponding sensors within a vehicle as their output signals, are shown per decision with respective conditions.

As is known from the prior art, the permitted vehicle states are here also • +1, for a forward-oriented journey,

• 0, for an undefined state (standstill) and

• -1, for a backward ride.

The method now proceeds in the following steps: 1. Recording of the existing wheel speeds yj jh, γ ₉ , .... from the corresponding sensors at a time step j; 2. Computational determination of a reference speed y ^{J of} the vehicle from the wheel speeds γ ^J , y ^J _? ....;

3. Determining a maximum value γ ^J ≡ max (y ^J L yl y ^J ₇ , ...) from

the series of received wheel speeds γ | , y ₇ , .... 4. decision as to whether a minimum measurable speed Y has been exceeded by the maximum speed γ ^J defined above of the vehicle;

5. If yes, then examine whether the vehicle has started to move, that is, _\ Vτraax < _\ Vrmin < _\ Vτmax 6. If yes, then determine the time derivative of the appropriately filtered slow acceleration a _x for time j when

7. Assignment of the result of the filtered time derivative of the longitudinal acceleration a _x

+1: Advance driving under conditions mentioned at the beginning, summary in the figure;

-1: reversing under conditions mentioned above, summary in the figure, and 0: undefined condition, if

* a _x Signal not clearly evaluable, then plausibility test by another known method, or

* a respective maximum value of all existing speeds is below the threshold value ^J t, ie vV max < _V V mm and a standing of the

Vehicle can be accepted.

8. Yaw rate ₍ JQ calculate and with measured yaw rate

Mcas

Q _{) z} compare, continue this evaluation if in the preceding time step j-1 the result was -1 and now j max Meas CaIc v _re f ^> v _rcf ^or ω _z - ^> + ω _z ^or in the preceding time step j-1 the result +1 j max Mcas Ca! cv _ref ^< v _ref ^and ω _z - ^> -G) ₂ ^•

Under these conditions, direct change is made from a state -1 to +1 from a preceding time step j-1 to a current time step j and vice versa.

9. Start result output to a driver assistance system or similar superordinate unit and method for new time step.

The method described above with reference to the drawing of the drawing allows a respective direction of travel status to be reliably detected independently of a respective driving situation and comparatively quickly at a time delay of approximately 100 ms to 500 ms caused by the filtering in step 6.

Claims

claims 1. A method for determining the direction of travel of a vehicle, characterized in that at least two wheel speeds for determining wheel speeds (V ₁ 'V ₂ ' • • ■ ^ evaluated, correlated and with a sensor a slow acceleration (a _x ) or alternatively a Pitch rate at a time step (j) are measured and these bigs are analyzed together to output conditions on the basis of which a heading decision is made according to a state diagram. 2. The method according to claim 1, characterized in that a maximum value (x Vr ¹ max ≡max ( ^v v v ^J re, f ViMV;, ...)) and a reference speed (y ^J ) of the vehicle from the series of received wheel speeds (yj, y, ....). 3. Method according to the preceding claim, characterized in that the method is only continued if a minimally measurable velocity (y,) is determined by the maximum velocity speed (y ^J ) of the vehicle has been exceeded. 4. The method according to any one of the preceding claims, d a d u c h e c e n e z e c h e n e that by Comparison with a temporal precursor value (y) and a minimum velocity (y) due to a g leichung ^{J J J} sbeziehung (

) is examined, whether the vehicle has begun to move. 5. The method according to any one of the preceding claims, characterized in that for the time (j) a first time derivative of the appropriately filtered slow acceleration (a _x ) is evaluated. 6. Method according to one of the preceding claims, characterized in that a yaw rate

) Are calculated from the wheel speeds, the yaw rate (Q j, Q _j) are compared in a convergence. Method according to the preceding claim, characterized in that a direct change from a state -1 to +1 from a preceding time step (j-1) to a current time step (j) is carried out, if in the preceding time step (j-1) the result was -1 and now j max Meas CaIc v _rC f ^> v _rcf ^or ω _z -> + OJz ^■ 8. The method according to claim 6, characterized in that a di- correct change from a state +1 to -1 from a preceding time step (j-1) to a current time step (j) is performed if in the preceding time step (3-I) the result was +1 and now holds

9. Device for determining the direction of travel of a vehicle, characterized in that at least two wheel speed sensors and a slow acceleration sensor or alternatively a pitch rate sensor are connected to a correlation logic, wherein the correlation logic for determining a driving direction πchtung evaluated from the output signals of said Sensors derived or determined conditions based on a stored in the logic state diagram is formed. 10. Device according to the preceding claim, characterized in that the acceleration sensor is arranged so that it measures a positive value at a vehicle longitudinal acceleration directed and / or the pitch rate sensor is arranged so that it assumes a positive value when nodding forward.