Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication
Reexamination Certificate
2001-04-13
2002-08-20
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
C701S038000, C701S072000
Reexamination Certificate
active
06438464
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to vehicle stability control, and more particularly relates to a method and a device for detecting the risk of rollover in vehicles which are equipped with a driving stability control system.
BACKGROUND OF THE INVENTION
It has been known for long that in vehicles having a high center of gravity and/or a small tread width, for example trucks, track trailer units, buses, small buses, and off-road vehicles, there is a rollover risk during cornering with a major roll motion. Various models for rollover accidents are described on pages 309 to 333, chapter 9, of the book “Fundamentals of Vehicle Dynamics”, by T. D. Gillespie, Society of Automotive Engineers, Inc., Warrendale 1992, which is referred to in full extent in the present context. Starting with a quasi-stationary model for a rigid vehicle by way of a quasi-stationary model for a sprung vehicle up to dynamic models in consideration of inherent roll frequencies, conditions for existing rollover hazards are indicated.
However, it has been found more recently that lateral motions of passenger vehicles may also build up until the vehicle rolls over. Such a risk of rollover is considerably increased by improper loading, e.g. extremely on one side or on the vehicle roof, because the center of gravity of the mass of the vehicle is shifted upwards or to one side. In addition, it is that more frequently vehicles are registered in recent times which are designed as passenger cars with a relatively high center of gravity, for example, the new vehicle class of the so-called “vans”.
To explain the physical driving conditions underlying rollover,
FIG. 2
a
shows a schematic rear view of a vehicle
210
standing on a roadway
200
. Reference numerals
103
and
104
designate the wheels of the rear axle. It is assumed that the vehicle is in a left turn, thus would move to the left in a projection to the drawing plane. The circular travel of the vehicle produces a centrifugal force Z=mw×&ohgr;2×r=m×v2:r, wherein m is the vehicle mass, &ohgr; the angular velocity during circular travel, v the vehicle speed and r the radius of the circular travel. The acting centrifugal force Z which can be represented as a product aq×m, with aq being the transverse acceleration, can be assumed to act on the center of gravity S of the vehicle. The center of gravity S is disposed roughly centrically between the wheels and at a height h above the roadway. Acting on the center of gravity S is also the weight force G=m×g, wherein g is the gravitational acceleration. As long as the vehicle drives on the desired circle (aq=v2:r applies then), i.e., as long as the cornering forces F on the four wheels (roughly corresponding to F=&mgr;×G, wherein &mgr; is the coefficient of friction between tires and roadway) equals the centrifugal force Z, the above-mentioned centrifugal forces will develop according to the above equation. It may happen then that the vehicle will roll over the outside wheel due to an unfavorable torque distribution. This will principally happen when G×b:2<Z×h applies, wherein h is the height of the center of gravity S above the roadway
200
and b:2 is roughly half the tread width of the vehicle. The above inequation is a first approximation of the torque equilibrium about the point P. When the outwards turning torque Z×h is greater than the inwards turning torque G×b:2, the vehicle will roll over outwards. This risk is encountered especially with vehicles having a small tread width (b:2) and a comparatively great height and, thus, a high center of gravity (high value of a), e.g. caused by a roof load
220
on the vehicle
210
.
To effectively avoid a like operating condition, it is necessary to
detect a critical situation, especially a driving condition with a critical transverse acceleration, and
take appropriate countermeasures following the detection.
In conventional driving dynamics control systems, for example, the ESP system (Electronic Stability Program) by the applicant, driving dynamics parameters, among others the transverse acceleration, the time variation of the transverse acceleration, or the tire slip angle, are provided as driving dynamics parameters which are indicative of the tendency of vehicle rollover about the longitudinal axis of the vehicle. A corresponding method for the operation of a vehicle with brake interventions that stabilize driving is e.g. described in German published patent application DE-A 196 32 943 “Method for the operation of an automotive vehicle with brake interventions that stabilize driving”Daimler-Benz Aktiengesellschaft, wherein the transverse acceleration is taken into consideration as the only driving-dynamics parameter indicative of the vehicle's tendency to rollover about the longitudinal vehicle axis. An associated predefinable rollover prevention threshold value is provided for the transverse acceleration.
During cornering, the vehicle is kept to track by the transverse forces which act at the tire tread surfaces on the roadway. The largest part of these transverse forces is produced by the curve-outward wheels or tires. When the transverse acceleration which occurs during cornering exceeds the rollover prevention threshold value, the curve-outward wheels will adopt a condition of high brake slip caused by activation of a corresponding brake intervention, with the result that the transverse force that can be transmitted by the tires is considerably reduced. Consequently, the curve-outward wheels can no longer withstand the transverse acceleration acting upon them (which will possibly increase the sideslip angle and turn the vehicle front end or the vehicle rear end slightly in the direction of the transverse acceleration torque). However, simultaneously, the rollover torque is reduced and rollover of the vehicle about its longitudinal axis prevented. In addition to this, the above-mentioned publication discloses an embodiment wherein the time variation of the transverse acceleration is taken into account as an indicative driving-dynamics parameter.
In published patent application DE-A 197 46 889 “Vehicle Motions Control System”, by Aisin Seiki K.K. et al, a system for increasing the lateral stability of an automotive vehicle during cornering is described wherein there is provision of a rollover detection unit for detecting a rollover motion of a normal axle of the vehicle with respect to the vehicle's vertical axis and a cornering determining unit for determining a cornering condition of the vehicle. To calculate the vehicle rollover motion or the vehicle rollover, either the difference in height between the right and the left vehicle side or the transverse acceleration of the vehicle is detected to establish the roll angle between the horizontal vehicle line and the horizontal roadway line. A linearity between the transverse acceleration aq and the vehicle rollover designated by a roll angle gamma is made the basis. When the inclination detection device detects a rollover risk, a countersteering yaw torque is produced by slowing down the curve-outward front wheel.
As has been described hereinabove though, the allowed transverse acceleration and the allowed roll angle depend on the center of gravity of the vehicle, especially the height of the vehicle center of gravity.
The known methods and systems for detecting the vehicle inclination or the roll angle, on the one hand, include the shortcoming that they require additional sensor means, for example, in the event of an inclination detection device with quantities that determine the difference in level between the right and the left vehicle sides, or that they depend on current vehicle characteristics such as the load condition or the center of gravity of the entire vehicle and, consequently, are subject to the requirement of constantly updating the basic vehicle data.
In view of the above, an object of the present invention is to provide a method and a device which overcome the above-m
Burkhard Dieter
Gronau Ralph
Ihrig Hans Georg
Kienle Lothar
Woywod Jürgen
Continental Teves AG & Co. oHG
Cuchlinski Jr. William A.
Pipala Edward
Rader & Fishman & Grauer, PLLC
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