DE102011080033A1 - Method for determining forward- and reverse movements of e.g. motor car, involves considering correlation of measured variables for determination of direction of movement within data set by multiple successive measurements - Google Patents

Abstract

The invention relates to a method in which the direction of travel of a vehicle is determined, wherein the yaw rate of the vehicle is measured as a first measured variable and at least one further measured variable describing the lateral dynamics of the vehicle. According to the invention, the correlation of the two measured variables is considered within a data set of several consecutive measurements in order to determine the direction of travel. Furthermore, a control unit of an electronically controlled braking system is defined.

Description

The invention relates to a method according to the preamble of claim 1 and a control device according to the preamble of claim 10.

Modern vehicles are increasingly equipped with driving stability control systems and / or driver assistance systems. For the reliable operation of these systems, the knowledge of the direction of travel of the corresponding vehicle is of great importance.

One way to detect the direction of travel is to use special wheel speed sensors on at least one wheel, which can detect the direction of rotation of the wheel. However, these sensors are expensive due to the extra effort (eg, using two transducers on an encoder wheel).

The DE 10 2006 001 378 A1 discloses a method for determining the direction of travel of a vehicle, which is equipped with at least one acceleration sensor and at least one wheel encoder. The expected value generated by the signal of the wheel pulser for a physical variable representing the direction of travel, preferably the speed of the vehicle, is compared with an actual value determined from the signal of the acceleration sensor. A similar method, which detects in particular a starting operation in the reverse direction, is in the DE 10 2009 020 594 A1 described. Sensors for longitudinal acceleration are usually not present in motor vehicles, with the exception of off-road vehicles, so that a method based thereon incurs additional costs.

From the DE 10 2007 003 013 A1 are known a method and a device for detecting the direction of travel of a motor vehicle, are detected in the actual signals of at least two wheel speed sensors. Depending on the comparison of the time sequence of the actual signals with a desired signal sequence for at least one direction of travel, the direction of travel is determined. A similar procedure is used in the DE 10 2007 030 431 A1 described. For detection of the direction of travel, a reference signal sequence must be known, or information from other sensors must be used.

From the EP 1 065 507 B1 For example, a method is known for determining whether a motor vehicle is moving in a forward or reverse direction. Here, the steering wheel relative angle, the yaw rate and the vehicle speed are measured and calculated from vehicle speed and yaw rate, a forward-facing and a backward-looking steering angle. In each case, the difference between the steering wheel relative angle and forward or backward steering angle is calculated and filtered. Based on a comparison between filtered and unfiltered value of the difference between steering wheel relative angle and forward or backward steering angle forward and backward overall differences are determined. The steps are repeated and the direction of movement is determined by comparing the accumulated amounts of forward and backward total differences.

The object of the present invention is to enable a reliable detection of a forward or reverse travel of a vehicle even without the presence of cornering. Furthermore, it is desirable that the detection can be carried out with the sensors already present for driving stability control.

This object is achieved by the method according to claim 1 and the control device according to claim 10.

Thus, a method is provided in which the forward travel or reverse travel of a vehicle is determined, wherein the yaw rate of the vehicle as the first measured variable and at least one other transverse dynamics of the vehicle descriptive variable are measured simultaneously. According to the invention, the correlation of the first and the further measured variable is considered within a data set of several consecutive measurements in order to determine the direction of travel.

At the same time, it is understood here that the measurement of the first and the further measured variable has at most a minimum time offset, which is preferably at least a factor of 10 below the time offset of two successive measurements of the same measured variable.

In conventional driving stability control systems, a yaw rate sensor for measuring the yaw rate is often present, so that this first measurement can be reliably determined without additional effort. By considering a data set from several successive measurements, short-term external disturbances only negligibly affect the measured quantities. By considering the correlation of the first and the further measured variable, random fluctuations of the measured quantities can be strongly suppressed. Thus, even minor steering corrections, which makes a driver unconscious during a straight-ahead driving, for the longitudinal direction detection, d. H. the distinction between forward and reverse, appropriate information.

Expediently, the further variable describing the lateral dynamics of the vehicle is proportional to the steering angle or the transverse acceleration or the wheel speed difference of two co-axial vehicle wheels. With achsgleichen wheels here means that the considered wheels are preferably each left and right front or left and right rear wheels of the vehicle, or have a negligible longitudinal offset between the axes of rotation. The sizes mentioned are measured by means of many already existing sensors, so that no additional costs. Steering angle, lateral acceleration and wheel speed difference are independent when driving through a curve from a forward or reverse direction. In contrast, the sign of the yaw angular velocity when passing through the same curve changes depending on whether it is in the forward or reverse direction. Thus, a distinction between forward or reverse travel can be made from consideration of the correlation between yaw angular velocity and one of the other measured quantities. If more than one of the aforementioned measured variables are measured, in particular a redundant calculation of the correlation coefficients takes place, as a result of which plausibility considerations and thus a further increased reliability of a longitudinal direction detection are made possible.

The size of the data set, that is to say the number of successive measurements, is preferably determined as a function of the amount of yaw angle acceleration. An adaptive choice of the size of the data set ensures optimal longitudinal direction recognition under the respective driving conditions.

For each data set, the average, in particular arithmetic mean, of the first measured variable and the mean, in particular arithmetic mean, of the further measured variable and the deviations of the individual measurements of the first and the further measured variable from the respective mean values are preferably calculated. Averaging reduces random fluctuations of the measured quantities.

Particularly preferably, the correlation coefficient between the deviations of the two measured variables is calculated. The correlation coefficient, also referred to as the correlation coefficient, quantifies the relationship between the two measured variables and can be evaluated with a reasonable computational effort.

Most preferably, forward travel is determined when the magnitude of the correlation coefficient exceeds a first threshold and the correlation coefficient is positive when counterclockwise rotation corresponds to positive yaw angular velocity and the further magnitude is positive at a left turn.

Since two uncorrelated quantities have a correlation coefficient of nearly zero, the presence of a correlation between the two measured quantities is checked by comparing the magnitude of the correlation coefficient with a suitably selected threshold value. Then, with appropriate choice of the sign convention, a forward or reverse drive can be reliably detected.

Still more preferably, a reverse drive is determined when the magnitude of the correlation coefficient exceeds a first threshold and the correlation coefficient is negative provided that a counterclockwise rotation corresponds to a positive yaw angular velocity and the further measured is positive at a left turn.

It is advantageous if the determined direction of travel is made plausible on the basis of information on actuation of a drive coupling and / or vehicle speed. By additionally using independent information, the reliability of the recognition can be further increased.

It is particularly advantageous to accept a change in the direction of travel as plausible only if the vehicle speed has fallen below a speed limit value in a predetermined period of time before determining the direction of travel change, and in particular an actuation of the drive clutch has been detected.

If the vehicle has information on the engaged gear, they can also be used for plausibility. A reverse drive can then be conveniently detected by the correlation coefficient when exceeding a particularly small limit for the amount of the correlation coefficient when no gear or reverse gear is engaged. Furthermore, it is advantageous if, after an actuation of the drive clutch with a first gear or reverse gear engaged or in the disengaged state, a change in direction is detected when a particularly small limit value for the amount of the correlation coefficient is exceeded.

The invention further relates to a control device of an electronically controlled brake system of a motor vehicle, which performs a method according to at least one of the preceding claims.

Further preferred embodiments will become apparent from the subclaims and the following description of an embodiment with reference to figures.

Show it

1 a vehicle suitable for carrying out the method according to the invention,

2 a schematic of a method for detecting a forward or reverse drive in a curve, and

3 a scheme of the method according to the invention for detecting a forward or backward drive even when driving straight ahead.

1 shows a schematic representation of a motor vehicle 1 , which is suitable for carrying out the method according to the invention. It has a drive motor 2 driving at least a part of the wheels of the vehicle, a steering wheel 3 , a brake pedal 4 , which with a tandem master cylinder (THZ) 13 is connected, and four individually controllable wheel brakes 10a - 10d on. The inventive method is also feasible if only a part of the vehicle wheels is driven. In addition to or as an alternative to hydraulic friction brakes, electromechanically actuated friction brakes can also be used as wheel brakes on one, several or all wheels. According to an alternative embodiment of the invention, the vehicle has an electric drive, and the braking torque on at least one wheel is generated at least partially by the electric machine (s) operated as a generator.

For the detection of driving dynamic conditions are a steering wheel angle sensor 12 for measuring the steering angle δ, four wheel speed sensors 9a - 9d for measuring the rotational speeds V _{i of} the individual wheels, a lateral acceleration sensor 5 for measuring the lateral acceleration a _Lat , a yaw rate sensor 6 for measuring the yaw angular velocity Ψ. and at least one pressure sensor 14 for the measurement of the brake pressure generated by brake pedal and THZ p exist. In this case, the pressure sensor 14 be replaced by a Pedalweg- or pedal force sensor, if the auxiliary pressure source is arranged such that a brake pressure built up by the driver of the auxiliary pressure source is indistinguishable or an electromechanical brake actuator is used with known relationship between pedal position and braking torque. The signals from the wheel sensors are sent to an electronic control unit (ECU) 7 supplied, which determines the vehicle speed V _Ref based on predetermined criteria from the Raddrehgeschwindigkeiten V _i .

The electronic control unit (ECU) 7 receives the data of the above-described as well as possibly existing further sensors and controls the hydraulic unit (HCU) 8th to allow a driver independent of a structure or a modulation of the brake pressure in the individual wheel brakes. In addition, the current of drive motor 2 generated driving torque and the torque desired by the driver determined. These may also be indirectly determined variables, which are derived, for example, from an engine map and the electronic control unit 7 via an interface 11 , z. B. a CAN or FlexRay bus from the engine control unit, not shown.

The driving behavior of the motor vehicle 1 is significantly influenced by the suspension design, among other things, wheel load distribution, elasticity of the suspension and tire properties determine the self-steering behavior. In certain driving situations, which are characterized by a predetermined, desired radius of curvature and the coefficient of friction between the tire and the road, there may be a loss of driving stability, the driver's desired steering behavior can not be achieved with the given suspension design. With the existing sensors, the driver's request can be detected and the realization can be checked by the vehicle. Preferably, the tendency to loss of stability is already detected.

This finds z. For example, a regulation of the yaw angular velocity takes place on the basis of a vehicle model in order to avoid a spin of the vehicle. For a suitable function of the control algorithms or of driver assistance systems, it is necessary to know the direction of travel of the vehicle.

This recognition of the reversing of a two-lane vehicle can be based on known relationships between different measured or determined variables:
In a first variant, the differences of the wheel speeds of the wheels on an axis with the yaw rate also called yaw rate Ψ. compared to the vehicle. Yaw rate or yaw rate is understood to mean the time change of the yaw angle around the vertical axis through the center of gravity of the vehicle. The sign of the difference in the wheel speeds is the same for forward and reverse. On the other hand, the sign of the yaw rate Ψ changes. but depending on the direction of travel.

The following discussion uses a Cartesian right-handed coordinate system, where it is assumed that when moving in the Direction "counterclockwise" the yaw rate Ψ. is positive. Then in a left turn the yaw rate Ψ. positive in forward travel (Ψ.> 0) and negative in reverse (Ψ. <0), while in a right-hander the yaw rate Ψ. negative for forward travel (Ψ. <0) and positive for reverse travel (Ψ.> 0).

On the other hand, in a left-hand turn both the forward and the reverse drive, the speed V _{L of} the left-hand (inboard) wheel is smaller than that of the right-hand wheel: V _L - V _R <0

Correspondingly, in a right turn, the right wheel speed V _{R is} smaller than that of the left wheel both in forward and in reverse: V _L - V _R > 0

In 2 FIG. 12 is a schematic of a method of detecting forward or reverse travel based on the relationships discussed above during cornering. FIG.

At the beginning, in step 20 the wheel speeds V _L and V _{R of} the left and right wheels on a vehicle axle and the yaw rate Ψ. measured.

Subsequently, in step 21 calculates the difference Δ = V _L -V _{R of} the left and right wheel speeds.

When in step 22 it is found that the amount of the difference | Δ | does not exceed a predetermined limit δ ₁ , the steps become 20 to 22 repeated.

If the condition | Δ | > δ _{1 is} satisfied, is in step 23 checks whether the amount of yaw rate exceeds a given limit, | Ψ. | > δ ₂ . If this is not the case, then the steps become 20 to 23 repeated.

Subsequently, in step 24 checked whether the wheel speed difference Δ has a positive or a negative sign, that is, whether there is a right or a left turn.

If the sign of Δ is positive, in step 25 considered the sign of the yaw rate.

Applies Ψ. > 0 so will step in 26 a reverse drive and a right turn detected and / or output.

If, on the other hand, Ψ. <0 is, so in step 27 a forward drive and a right turn detected and / or output.

If the sign of Δ is negative, in step 28 checked the sign of the yaw rate.

Applies Ψ. > 0 so will step in 29 a forward drive and a left turn detected and / or output.

If, on the other hand, Ψ. <0 is, so in step 30 a reversing and a left turn detected and / or output.

Of course, the verification of the conditions can also be carried out in a different order.

An alternative embodiment of the method described above is based on a measurement of the lateral acceleration and is therefore feasible if the vehicle has a lateral acceleration sensor. In a change from the forward to the reverse or vice versa, the sign of the lateral acceleration a _Lat does not change. Thus, when it is agreed that the lateral acceleration a _{Lat has} a positive sign in a right turn, the sign of the lateral acceleration in a left turn is negative in both the forward and the reverse drive. This allows a distinction of reverse and forward driving according to the basis 2 explained method. Here, instead of the wheel speeds in step 20 measured the lateral acceleration, whereupon step 21 can be omitted. Accordingly, in step 22 checks if the lateral acceleration exceeds a minimum amount and in step 24 considered the sign of the lateral acceleration. Thus, if a _Lat > 0 and Ψ. > 0 a forward-traversed left turn are detected, for the other cases, a detection is carried out accordingly. In principle, the method can be applied on the basis of any further measured variable whose sign depends on a right or left turn, but not on a forward or reverse drive.

The methods considered so far have the disadvantage that a cornering is required for recognition of the longitudinal direction.

In 3 is a preferred embodiment of the method according to the invention shown schematically, which can also distinguish a forward from a reverse drive during a straight ahead.

First, in step 31 the wheel speeds V _{Li of} the left and V _{Ri of} the right wheel on a vehicle axle and the yaw rate ψ _i measured.

Subsequently, in step 32 calculates the difference Δ _i = V _Li - V _{Ri of} the rotational speed of the left and right axis-same wheel.

The measurements and calculation of the steps 31 and 32 be repeated until the review in step 33 results in that a set of N yaw rates and wheel speed differences was obtained. Between the individual measurements are preferably short time intervals .DELTA.t constant duration.

Innerhalb eines Datensatzes erfolgt eine Änderung der Gierrate von:

According to a preferred embodiment of the invention, a data record has a constant length N. An alternative preferred embodiment of the invention selects the length of a data set adaptively as a function of yaw rate ψ. _i and yaw acceleration

Within a data set, the yaw rate changes from:

For constant time intervals you get:

In order to avoid errors due to an excessive yaw rate, the condition ΔΨ. << Ψ. be met, limiting the maximum length of a record:

gewählt, indem z. B. die Messung beendet wird, wenn diese einen vorgegebenen Schwellenwert überschreitet.Thus, the length of a data set may be determined by considering the instantaneous change in yaw rate

chosen by z. B. the measurement is terminated when it exceeds a predetermined threshold.

Once a record has been captured, done in step 34 the calculation of the mean values of yaw rate and wheel speed difference:

Subsequently, in step 35 the correlation coefficient R _ΔΨ between the deviations from yaw rate of a data point to the mean value or wheel speed difference of a data point to the mean value is calculated:

When in step 36 it is determined that the amount of R _ΔΨ does not exceed a predetermined threshold value δ ₃ , so that there is no detectable correlation, a data set is again measured.

If the data record for a direction detection because of | R _ΔΨ | > δ ₃ is used in step 37 checked the sign.

If the sign of the correlation coefficient is positive (R _ΔΨ > 0), in step 38 detected on reverse.

Otherwise (R _Δψ <0) will be in step 39 detected on forward drive.

If the vehicle is equipped with a lateral acceleration _sensor , alternatively or additionally, the correlation coefficient R _aΨ between a _Lat and Ψ. be used for the direction of travel detection, the algorithm off 3 is adjusted accordingly.

This will be in step 31 instead of the wheel speeds, the lateral acceleration a _Lat measured, whereupon step 32 can be omitted. step 34 includes accordingly the Averaging of lateral acceleration a _lat . In the following steps, the correlation coefficient R _aΨ between lateral acceleration a _Lat and yaw rate Ψ. calculated (step 35 ), checked for a sufficient correlation (step 36 ), and then recognized on the basis of the sign of the correlation coefficient on reverse (R _aΨ > δ ₃ ) or forward _drive (R _aΨ ← δ ₃ ).

In the presence of a steering angle sensor, the further possibility for detecting a reverse _{drive is} a correlation coefficient R _αΨ between steering angle α and yaw rate Ψ. to use. Here are the steps in 3 adjusted accordingly. Of course, the order of the individual steps (if appropriate) can be changed.

A further increase in the reliability of the longitudinal direction can be achieved by calculating the correlation coefficient between yaw rate and more than a second measured variable. Are z. For example, if the correlation coefficient between the yaw rate and the steering angle and the correlation coefficient between the yaw rate and the lateral acceleration are calculated, they can be checked for consistent results. If all three mentioned correlation coefficients are calculated, a forward or reverse drive can be detected in a "majority decision".

Another possibility for plausibility checks is when information about the clutch actuation is available. This information can be viewed along with vehicle speed information to detect a change in direction of travel. Such a plausibility check is based on the context that a change in the direction of travel from the forward to the reverse or vice versa occurs only at low vehicle speed and in particular after a clutch actuation.

If information about the engaged gear and in particular the clutch operation are available, they can also be used for plausibility considerations. So z. Example, provided that a longitudinal direction change, in particular after a clutch operation may occur when the first gear, no gear or reverse gear was engaged.

Of course, one or more of the measured quantities under consideration may also be suitably filtered to further increase the reliability of forward / reverse detection.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• DE 102006001378 A1 [0004]
• DE 102009020594 A1 [0004]
• DE 102007003013 A1 [0005]
• DE 102007030431 A1 [0005]
• EP 1065507 B1 [0006]

Claims (10)

A method in which the forward travel or reverse travel of a vehicle is determined, wherein the yaw rate of the vehicle as the first measured variable and at least one further transverse dynamics of the vehicle descriptive variable are measured simultaneously, characterized in that for determining the direction of travel within a record of several successive Measurements the correlation of the first and the other measured variable is considered. A method according to claim 1, characterized in that the further describing the lateral dynamics of the vehicle size is proportional to the steering angle or the lateral acceleration or the wheel speed difference of two coaxial vehicle wheels. A method according to claim 1 or 2, characterized in that the size of the data set, that is, the number of consecutive measurements, is determined in dependence on the amount of yaw angular acceleration. Method according to at least one of claims 1 to 3, characterized in that for each data set the average, in particular arithmetic mean, of the first measured variable and the mean of the further measured variable and the deviations of the individual measurements of the first and the further measured variable from the respective mean values calculated become. A method according to claim 4, characterized in that the correlation coefficient between the deviations of the two measured variables is calculated. A method according to claim 5, characterized in that a forward drive is determined when the amount of the correlation coefficient exceeds a first threshold and the correlation coefficient is positive, when a counterclockwise rotation corresponds to a positive yaw angular velocity and the further measured variable is positive in a left turn. A method according to claim 6, characterized in that a reverse drive is determined when the amount of the correlation coefficient exceeds a first threshold and the correlation coefficient is negative when a counterclockwise rotation corresponds to a positive yaw angular velocity and the further measurand is positive in a left turn. Method according to at least one of the preceding claims, characterized in that the determined direction of travel is checked for plausibility on the basis of information on actuation of a drive coupling and / or vehicle speed. A method according to claim 8, characterized in that a change in the direction of travel is only accepted as plausible if the vehicle speed has fallen below a speed limit in a predetermined period of time before determining the direction of travel change and in particular an actuation of the drive clutch has been detected. Control unit of an electronically controlled braking system of a motor vehicle, characterized in that it carries out a method according to at least one of the preceding claims.

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