DE19846425A1 - Procedure for determining the radius of the curve - Google Patents

Abstract

The invention relates to a method for determining the curve radius of lanes, the difference in wheel speed of at least two vehicle wheels being measured and the yaw rate of the vehicle and thus the curve radius being determined therefrom. DOLLAR A The invention is therefore based on the object of providing a method for determining the radius of the curve, which works much more precisely with simple means which are self-sufficient for the vehicle and which can simultaneously take into account different influencing factors. DOLLAR A The object on which the invention is based is achieved in a method of the type mentioned in the introduction in that for each wheel a constant wheel angle (phi¶0¶), that on each wheel via the wheel angle (phi¶0¶) the total period over this wheel angle (phi¶0¶) is measured, that the total period of the wheels of a pair of wheels of an axle is related to each other and that the cross-slip and thus the curve radius (R) is determined from the ratio of the total period.

Description

The invention relates to a method for determining the curve radius of lanes, the difference in wheel speed of at least two non-driven Vehicle wheels measured and from this the yaw rate of the vehicle and thus the Curve radius is determined.

When driving on curves, the driver of the motor vehicle regulates the Driving speed taking into account the radius of the curve Road surface conditions and weather conditions. Are increasing modern motor vehicles, however, with speed control systems and also with Navigation systems equipped so that it is desirable to have accurate information to get about the course and condition of the road. This information can then as further parameters the cruise control system or the Navigation system will be provided. For example, a Comparison of the course of the road with the saved map, so that the Accuracy of the navigation system is significantly improved.

The goal here is to help the driver of the motor vehicle operate it as far as possible possible to relieve pressure and thus also to increase traffic safety.

DE 197 49 306 A1 describes a method for predictive determination of the Driving corridor of a motor vehicle for an automatic distance warning system is known become. The curve radius is the difference between the wheel speeds measured by at least two vehicle wheels. Because the wheel speed of the Vehicle wheels are not only dependent on the speed driven, but also from other influencing factors such as wheel slip or Road surface condition, the curve radius determined according to this method only provides an approximate value.  

The invention is therefore based on the object of a method for determining the To create curve radius that is essential with simple and vehicle-self-sufficient means works more precisely and takes into account different influencing factors at the same time can be.

The problem underlying the invention is in a method of the beginning mentioned type in that a constant wheel angle is specified for each wheel is that on each wheel over the wheel angle the total period of the wheel pulses This wheel angle is used to measure that the total period of the wheels is one Wheel pair an axis is related to each other and that from the Ratio of the total period of the cross slip and thus the curve radius is determined.

Further embodiments of the invention emerge from the subclaims.

With this easy to implement method, the curve radius or the Determine road curvature with very good accuracy without additional external Tools are needed.

The easiest way to set the constant wheel angle is to specify a constant one Determine the number of speed impulses, since vehicles with ABS or ASR anyway over Have pulse generators on all wheels.

To increase the accuracy of the measurement, it is advantageous if, for example, before every measurement or at predetermined intervals an offset adjustment of all Measured times is made by using the ratio of measured times an average is formed. This offset adjustment is useful to by lane differences, different road conditions or also by Compensate tolerances due to tire differences. The mean is a measure of the error and can then be taken into account when calculating the curve radius.

To the influence of acceleration processes of the motor vehicle as a source of error to exclude, it is still appropriate if the start of the time measurement to the Wheels of a pair of wheels is synchronized.  

The invention is described below using an exemplary embodiment with reference to drawings explained in more detail.

Fig. 1 shows this, schematically, a pair of wheels of a motor vehicle when driving on a curve having a radius R along a path?. The wheel pair is at a constant distance A from one another.

To determine the curve radius R, it must first be assumed that each wheel is over has a pulse generator, not shown, so that a constant wheel angle ϕ can be specified, which is the same size for each wheel. It can do that simply take place that a constant number of speed pulses and thus the wheel angle ϕ is specified.

For freely rotating non-driven wheels, the translational speed v ₁ , v _{2 of} the wheels applies the following relationship

The curve radius R can be calculated using the following formula:

The simplification for the curve radius R applies because of the following relationships:

It is assumed that

R <250 m

and A ≦ 2 m.

The following applies to the angular velocity of each wheel:

where Δϕ _{0 is} a fixed angle and Δt _i indicates the time for the wheel rotation by the angle Δϕ ₀ .

Is used for the ratio of the current measuring radii

and for the ratio of the current measuring times

set, the following results for the reciprocal curve radius:

When driving straight ahead:

This means:

Τ ₀ is determined simply by averaging:

τ ₀ = mw10 '(τ)

Measuring principle

There is a synchronized measurement of the time .DELTA.t ₁ , .DELTA.t ₂ for a predetermined wheel angle or a predetermined number of speed pulses for both wheels on one axle, so that the time ratio

can be determined ( Fig. 2).

According to Formula 8, the current curve radius is:

The following applies for τ ₀ :

τ ₀ = τ (R → ∞) ≈ mw (τ)

The curve radius A determined in the manner described above can now on-board computers are made available.  

Reference list

ARheel distance of a wheel axle
R curve radius
v ₁

Speed wheel

1

v ₂

Speed wheel

2nd

Ω the distance traveled by the vehicle
r ₁

Radius wheel

1

r ₂

Radius wheel

2nd

Ω Angular velocity of the vehicle
ω ₁

Angular velocity wheel

1

ω ₂

Angular velocity wheel

2nd

l ₀

Wheel angle
Δl ₀

fixed wheel angle
Δt _i

Time for wheel rotation by Δl ₀

t _1.2

Time to turn the wheel
ξRelationship of the current wheel radii
Ratio of the current measuring times

Claims (5)

1. A method for determining the radius of curvature of lanes, wherein the difference in the wheel speed of at least two vehicle wheels is measured and the yaw rate of the vehicle and thus the radius of the curve is determined therefrom, characterized in that a constant wheel angle is specified for each wheel, that on each wheel Using the wheel angle, the total period is measured via this wheel angle, that the total period of the wheels of a wheel pair of an axle is related to each other and that the cross-slip and thus the curve radius is determined from the ratio of the total period. 2. The method according to claim 1, characterized in that the constant Wheel angle determined by specifying a constant number of speed pulses becomes. 3. The method according to claim 1 and 2, characterized in that a Offset adjustment of the times measured on all wheels is carried out by an average is formed over the ratio of the measured times. 4. The method according to claim 3, characterized in that the offset adjustment in predetermined time intervals is made. 5. The method according to any one of claims 1 to 4, characterized in that the Start of time measurement on the wheels of a pair of wheels is synchronized.