Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1998-06-12
2001-10-16
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C709S241000
Reexamination Certificate
active
06304807
ABSTRACT:
BACKGROUND OF THE INVENTION
1 Field of the Invention
The invention relates to a method for determining the yaw velocity of a vehicle, in particular for adaptive driving-speed control, from wheel speeds measured by wheel-speed sensors on a right and a left non-driven wheel, wherein the yaw velocity of the vehicle is determined from a comparison of the measurements of the right wheel speed and the left wheel speed.
A system for controlling the driving stability of a motor vehicle is known from German Patent DE 44 36 162 C1, corresponding to U.S. patent application Ser. No. 08/837,241, filed Apr. 10, 1997. In that system, a control device is supplied not only with the wheel speeds measured by sensors, in order to control the brake pressure applied to the individual wheels on the basis thereof, but the control device also receives further signals from a steering-angle sensor and a yaw-velocity sensor, in order to keep the driving condition of the motor vehicle stable. In that context, it is also known to determine the yaw velocity, that is to say the rotation of the vehicle about the vertical axis, not in a sensor but instead by computation and specifically, for example, from the wheel speeds of the two front or rear wheels, or from the steering-wheel angle and a wheel speed.
Mathematical derivations for the steering-wheel angle, the yaw velocity and further functions in the case of driving a vehicle steadily in a circle at a constant radius with a constant driving speed are presented in a publication entitled “Dynamik der Kraftfahrzeuge”[Motor Vehicle Dynamics] by M. Mitschke, Vol. C, Fahrverhalten [Handling], 2nd Ed., Springer-Verlag, pp. 31-39. The functions are determined on one hand from vehicle data, such as mass m and wheelbase, l and on the other hand from steering data, such as steering angle and steering ratio. Those derivations also disclose the combination of a series of vehicle and steering data into a “characteristic driving speed” v
ch
. It is often not possible to determine the yaw velocity with the high accuracy often desired by using the equations given in the literature. Indeed, the tire pressure as well as the tire wear may vary on the different wheels. Furthermore, the handling may be affected by crosswind and by steering-angle corrections, for example in the case of a cambered road.
If it is desired to determine even low yaw velocities with high accuracy, then that is usually performed with yaw-velocity sensors as have been developed for aircraft navigation. Sensors of that type are expensive and are also sensitive to temperature, usually exhibiting a temperature drift of up to 1°/s.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for determining the yaw velocity of a vehicle, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known methods of this general type and which calculates the yaw velocity of a vehicle with high accuracy from wheel speeds.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for determining a yaw velocity of a vehicle, in particular for an adaptive driving-speed control, which comprises measuring wheel speeds with wheel-speed sensors on a right and a left non-driven wheel; determining a yaw velocity of the vehicle from a comparison of the measurements of the right wheel speed v
r
and the left wheel speed v
1
; and correcting the wheel speeds v
r
and v
l
, by calculating a correction factor q=v
rs
/v
ls
when the vehicle is driving in a straight line and using the correction factor q to correct a ratio v
r
/v
l
between the right and left wheel speeds, where v
rs
and v
ls
are the wheel speeds when driving in a straight line.
According to the invention, the wheel speeds measured by wheel-speed sensors for the two monitored unpowered or non-driven driven wheels, that is to say the left and right front wheels in the case of rear-wheel drive, are corrected by a correction factor which is determined when the vehicle is driving in a straight line and which is therefore capable of eliminating different tire pressures, different tire wear, steering angle due to a cambered road, crosswind and other factors. The yaw velocity can therefore be calculated very accurately.
With the method according to the invention, it is advantageously possible to carry out adaptive driving-speed control. In this case, a distance sensor determines the speed and the distance of a vehicle from the vehicle driving in front. In order to establish whether or not another vehicle is in one's own lane, that is to say in conjunction with passing maneuvers and lane changing, lane prediction must be carried out. For that purpose it is necessary to have the yaw velocity of one's own vehicle. In order to achieve good lane prediction, the yaw velocity must be determined to about +/−0.2°/s, since under normal driving conditions on the highway, only small yaw velocities of from +5°/s to −5/s occur, and the maximum is about +/−20°/s.
In this context, the invention provides a cost-efficient solution, since the wheel-speed sensors which are in any case provided for antilock protection deliver the measurements for calculating the yaw velocity and the correction factor.
In accordance with another mode of the invention, there is provided a method which comprises calculating the yaw velocity as a function of the determined wheel speed v and a characteristic driving speed v
ch
from a ratio v/(1+(v/(v/
ch
)
2
), and multiplying the ratio by a correction term (v
r
/v
l
−q)/(v
r
/v
l
+q)
In accordance with a further mode of the invention, there is provided a method which comprises determining the correction factor q when a particular driving speed is exceeded and for a steering angle of approximately zero.
In accordance with an added mode of the invention, there is provided a method which comprises filtering the correction factor q with a low-pass filter.
In accordance with a concomitant mode of the invention, there is provided a method which comprises continuously determining a difference in the yaw velocity due to a steering angle and due to the wheel speeds, and when the difference exceeds a predetermined amount, following up the correction factor q by shortening a time constant of the low-pass filter before increasing it again slowly to a maximum value after a new correction factor has been determined.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for determining the yaw velocity of a vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
REFERENCES:
patent: 4042059 (1977-08-01), Bertolasi
patent: 5190111 (1993-03-01), Young et al.
patent: 5456641 (1995-10-01), Sawase
patent: 5479811 (1996-01-01), Baumann et al.
patent: 5670716 (1997-09-01), Tamasho et al.
patent: 5725067 (1998-03-01), Ikeda et al.
patent: 5857160 (1999-01-01), Dickinson et al.
patent: 5857754 (1999-01-01), Fukami et al.
patent: 44 36 162 C 1 (1996-03-01), None
Japanese Patent Abstract No. 07291154 A (Tsukasa), dated Nov. 7, 1995.
Hoppstock Reiner
Kirchberger Andreas
Cuchlinski Jr. William A.
Greenberg Laurence A.
Lerner Herbert L.
Marc-Coleman Marhe Y.
Siemens Aktiengesellschaft AG
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