Process for influencing the parameters of a car's...

Details Process for influencing the parameters of a car's... Process for influencing the parameters of a car's...

1999-05-06

2001-11-27

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

C701S071000, C701S083000, C030S010001, C030S010001

Reexamination Certificate

active

06324460

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method of influencing driving dynamics parameters.
A method of this type is disclosed in WO-A 86/07321. This publication refers to adjusting a brake slip value during controlled braking of a vehicle wheel where the coefficient of friction Ti in the longitudinal direction is close to the maximum attainable value, on the one hand, and a sufficient coefficient of friction in the transverse direction is available, on the other hand. This slip value is below the value at which the coefficient of friction in the longitudinal direction is at its maximum. While the frictional value/brake slip curve &lgr;(&mgr;) has the gradient 0 at the maximum coefficient of friction in the longitudinal direction, &lgr;(&mgr;) adopts positive gradients at the slip value to be adjusted. Beside the advantage of higher cornering forces, the prior art concept provides the possibility of definedly limiting yaw torques occurring on the vehicle during controlled braking and, thus, improving the ability to govern the vehicle. To this end, gradient values on the frictional value-slip curve are aimed at in brake pressure control, which are e.g. made responsive to the steering angle or other actual driving conditions. The precondition for this control is that the wheel sensors for ascertaining the individual rotational speeds are in a state of operation. In a road vehicle equipped with four wheel sensors, it cannot be expected that all four wheel sensors stay intact for the total useful life of the vehicle. Upon failure of a wheel sensor, however, a control of the above type is not possible because the brake slip of the respective wheel cannot be ascertained. Usually, brake slip control is disconnected in such cases.
An object of the present invention is to provide a method of the type mentioned hereinabove which provides sort of an emergency function for the control even if at least one wheel sensor is defective.
SUMMARY OF THE INVENTION
This object is achieved by applying, upon malfunction of a wheel sensor, a two-operation-point control on the frictional-value-over-slip curve to the wheel concerned, wherein the operating points on the curve are independent of the rotational speed of the wheel concerned.
The present invention is not limited to vehicles which are equipped with a brake system for brake pressure control on each individual wheel for purposes of brake slip control, traction slip control, or yaw torque control, but is also applicable to vehicles which include a system of distribution of drive torques to each individual wheel. The principle of the present invention is that the method is limited to two operating points on the frictional-value-over-slip curve which are not selected in dependence on the rotational speed of the wheel concerned but rather in dependence on other driving dynamics parameters.
The simplest choice for the first operating point is a longitudinal slip of zero. This means that no drive torques or deceleration torques act upon the wheel concerned. Thus, neither the drive motor nor the brake system acts upon the wheel concerned in this operating point.
This operating point is appropriate for driving situations where the objective is to transmit great cornering forces because the transmission of maximum cornering force is possible at a minimum longitudinal slip.
The second operating point can be determined by a defined deceleration torque or a defined drive torque which is generated by the respective arrangement according to predetermined conditions. It depends on outer circumstances which slip value the controlled wheel adopts.
Most simply, the second operating point is determined by a drive or deceleration device transmitting the maximum possible torque.
Admittedly, the maximum transmittable cornering force is very low at this second operating point, but the frictional value in the longitudinal direction is only slightly below its maximum. Thus, a great amount of longitudinal forces can be transmitted at this second operating point.
Depending on whether, in a determined driving situation, it is the task of the wheel whose wheel sensor has failed to predominantly transmit longitudinal forces or lateral forces, a selection is made between the second and the first operating point.
The idea of the present invention will now be explained in detail by way of the description of a drawing in two Figures.


REFERENCES:
patent: 3874743 (1975-04-01), Fleischer
patent: 5862503 (1999-01-01), Eckert et al.
patent: 6035251 (2000-03-01), Hac et al.
patent: 6122584 (2000-09-01), Lin et al.
patent: 4 130 370 (1992-03-01), None
patent: 4 333 281 (1993-09-01), None
patent: 4 419 650 (1995-07-01), None
patent: 2 158 533 (1985-11-01), None
patent: 86/07321 (1986-12-01), None
patent: 93/01074 (1993-01-01), None
patent: 93/05991 (1993-04-01), None
patent: 94/12377 (1994-06-01), None
patent: 95/04674 (1995-02-01), None
patent: 95/13946 (1995-05-01), None

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