Method of generating a signal to indicate a curve

Details Method of generating a signal to indicate a curve Method of generating a signal to indicate a curve

1990-07-13

1992-06-23

Lall, Parshotam S.

Boots, shoes, and leggings

36442602, 303 95, 303100, B60T 872

Patent

active

051249219

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

German DS 34 21 700, to which U.S. Pat. No. 4,593,955 corresponds, discloses an anti-lock brake control system which includes sensors, an evaluation circuit and brake pressure controls. The front wheels are individually controlled, but there is a delay of the yaw torque build-up at a front wheel running on a surface with a higher.mu. (high wheel) with a start of the control, this delay slows down the pressure build-up at a front wheel running on a surface with a lower.mu. (low wheel). The purpose of this measure is to slow down the generation of yaw torques around the vertical vehicle axis on road surfaces with an asymmetric friction coefficient such that the vehicle remains under controlled operation.
This delay of yaw torque build-up, however, is disadvantageous when a vehicle passes a curve and during the then following control for two reasons. First, a vehicle which is subject to braking exhibits in the curve a rotation into the circle. Second the delay of the yaw torque build-up causes the generation of a counter-directed torque to be delayed because of the immediate full braking effect at the front wheel at the outer edge of the curve. Said publication therefore proposes to shut off the delay of the yaw torque build-up in a curve and to individually control the pressure in the wheel brakes of the front wheels. A transverse acceleration sensor is used to detect the curves.
It is disadvantageous that a transverse acceleration sensor must be used which in turn requires additional monitoring means.


SUMMARY OF THE INVENTION

Assuming that wheel speed sensors are provided for different reasons (e.g. ABS), a curve can be detected without additional sensors by measuring the speed difference of diagonally opposed wheels and generating a signal corresponding to this difference or the variation of this difference with time. When at least one of these signals exceeds a prescribed limit, a signal which indicates the curve is generated.
The so recovered curve signal can be used, for example, to shut off the delay of the yaw torque build-up, to switch slippage- and acceleration thresholds in the evaluation circuit and also to monitor the transverse acceleration sensor.
During steady speed through a curve even without braking, there is a speed difference in at least one diagonal. In a left curve, the diagonal left front wheel/right rear wheel of a rear-wheel-driven vehicle exhibits such a difference. In case of a front wheel drive vehicle, under the same conditions, it is just the opposite diagonal. In a right curve, the diagonal right front wheel/left rear wheel of a rear wheel drive vehicle exhibits the difference, while it is the opposite diagonal for a front drive vehicle.
Using only the speed difference, it is advantageous, to signal the curve detection only after the difference has been present for a certain period of time. This time varies for different types of vehicles and is on the order of several hundred milliseconds. The threshold for .DELTA.V, after which there is a difference sufficient for curve detection, also depends upon the vehicle type. It ranges in the magnitude of 1-3 km/h. It appears advantageous to set the threshold such that curve detection starts at a transverse acceleration of approximately 0.5 g.
It also turned out that during unsteady speed in a curve, there are variations in the rotational speed difference. These too can be used for curve detection. Advantageously, both signal types are used together. The above mentioned monitoring period for the speed difference can then be reduced.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram in accordance with the invention and the use of the curve detection signal for shutting down the delay of the yaw torque build-up.
FIG. 2 is additional possibility of application.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows four sensors for measuring the wheels speeds which are referenced as LF (left/front), RF (right/front), LR (left/rear) and RR (right/rear). The signals of the sensors belon

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