Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-09-21
2003-06-17
Nguyen, Thu (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
Reexamination Certificate
active
06580995
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and a device for recognizing cornering, especially over-steered cornering, and for stabilizing a vehicle in case of over-steered cornering.
BACKGROUND OF THE INVENTION
A cornering maneuver can be recognized by different sensors, for example, steering angle sensors or transverse acceleration sensors, but the additional expenditure for the sensors also increases the expenditure for the cabling, the costs and the failure probability. Thus, there are applications in which it is desirable that cornering be detected without additional sensors. By the way, it is often difficult to recognize over-steered cornering, which is understood as a cornering maneuver in which the vehicle turns into a curve around its vertical axis to an extent exceeding the extent that would be necessary or, more generally speaking, in which a vehicle drives to the outer side of the curve with its tail. In the extreme case, we are talking about a swerving car in the broadest sense of the word. The present invention considers in particular also the extreme cases in which an over-steering exists only to a relatively small extent, for example, at the beginning of the vehicle's swerving. It is difficult to recognize an over-steered cornering maneuver just in these cases so that the over-steered behavior is increasing slowly until finally the vehicle is completely unstable. Conventional methods for recognizing over-steered cornering are not very useful due to the limited transverse dynamics in the limit range, so that the response thresholds for stabilizing interventions are not reached. Thus, a stabilizing brake intervention, which in principle would be possible, is omitted due to the lacking or delayed recognition of the over-steered cornering maneuver.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide methods and devices for recognizing cornering, especially over-steered cornering, as well as for stabilizing a vehicle during an unstable cornering maneuver, which are sensitive, reliable and manage without additional expenditure for sensors, if necessary.
Before describing single embodiments of the invention, basic relations of a vehicle in which the present invention can be applied are illustrated with regard to FIG.
1
and FIG.
2
.
FIG. 1
schematically shows a vehicle. Reference numerals
101
to
104
are the wheels of the vehicle, reference numeral
101
being the left front wheel, reference numeral
102
the right front wheel, reference numeral
103
the right rear wheel and reference numeral
104
the left rear wheel. Reference numeral
105
is the front axle, reference numeral
106
the rear axle. Reference numerals
111
to
114
are the wheel sensors detecting the wheel speed of the single wheels, particularly the rotating speed. Reference numerals
121
to
124
symbolize the wheel brakes. The output signals of the wheel sensors
111
to
114
are transmitted to a control
130
. Furthermore, the control can also receive signals of additional sensors
115
to
117
. In addition, the control
130
produces output signals
131
with which the longitudinal dynamics and/or the transverse dynamics of the vehicle can be influenced. Thus, they produce in particular signals for the wheel brakes
121
to
124
in order to adjust the brake pressure. In addition, signals can be produced which influence the driving torque and, if necessary, also the automatic transmission.
If a vehicle drives around a comer transverse forces (with regard to the longitudinal axis of the vehicle) have to be produced counteracting on the one hand to the centrifugal force resulting from cornering, and on the other hand to the moment of inertia of the vehicle itself during steering. The wheels transmit these forces to the vehicle. If the vehicle is stable the transverse forces resulting from this process can be transmitted by means of the static friction between roadway and tire. If the vehicle is unstable and in particular if it is over-steered, the transverse forces that are actually necessary are bigger than the forces that can be transmitted due to the static friction between roadway and wheels.
FIG. 2
describes the case that might appear in an over-steered left-hand curve. In
FIG. 2
, the left front wheel is shown. The same reference numerals as in
FIG. 1
indicate the same components. Reference numeral
111
is the wheel sensor, reference numeral
111
a
is a marking disc which follows the wheel
101
and helps determining the rotating speed of the wheel
101
. The speed of the wheel (and vehicle as described below) on the roadway is marked Vf. It is not oriented parallel to the wheel plane (vertical to the wheel axis) but extends at an angle, &agr;, to the wheel plane.
FIG. 2
shows the case of a wheel that is not braked. In this case, it can be assumed that the speed of the wheel in the wheel plane (vertical to the wheel axis) corresponds to the speed component of the wheel on the roadway (because the wheel can freely roll). As a result, the vehicle speed, Vf, can be determined from the vectorial addition of the longitudinal component, Vl, and the transverse component, Vq. More specifically, if there is a difference between the vehicle speed Vf and the longitudinal component, Vl (detected by the wheel sensors), then the difference can be attributed to a transverse component, Vq. This is valid both for the vectorial approach as also for the approach by the absolute amount.
Furthermore, it was established that during each cornering (i.e. ultimately also if a cornering maneuver is considered as stable) there is a transverse component—even if it is small—so that during each cornering, whether stable or over-steered, a transverse component is produced. Thus, a speed difference between the vehicle speed, Vf, and the longitudinal component, Vl (slip). The slip (difference between vehicle speed, Vf, and longitudinal component, Vl, or the difference between their absolute amounts) can be produced on different wheels, according to the driving situation.
According to the present invention, cornering is determined with reference to several slip values on several vehicle wheels. Also, an over-steered cornering maneuver can be determined with reference to several slip values on several vehicle wheels. According to the present invention, over-steered cornering can also be determined with reference to the transverse accelerations of the vehicle axles. According to another aspect of the present invention, over-steered cornering can be determined in a particularly reliable way if the determination based on the wheel slip values and the determination based on the transverse accelerations of the axles are combined with each other. If over-steered cornering has been detected, according to the present invention one or more measures supporting stability can be taken.
In the following single embodiments of the invention are described on the basis of the figures, whereby:
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patent: 1
Batistic Ivica
Schmidt Holger
Continental Teves AG & Co. oHG
Nguyen Thu
Rader & Fishman & Grauer, PLLC
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