Boots – shoes – and leggings
Patent
1992-12-31
1993-10-19
Black, Thomas G.
Boots, shoes, and leggings
303 95, 303103, 303105, B60T 832
Patent
active
052551946
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
When a vehicle, during braking without anti-lock control, starts skidding laterally with the wheels locked, the direction of movement of the gravity center which was present before the beginning of the skidding generally does not change since locked wheels cannot transfer lateral forces. A vehicle without ABS reacts in the same way when it starts skidding without braking because it has exceeded the dynamic limits of driving and the driver then applies the brakes during the skidding such that the wheels lock.
ABS prevents lateral skidding during braking as long as the dynamic limits of driving (e.g. excessive curve speed) are not surpassed. If the brakes are applied during skidding or if skidding occurs during a controlled braking, the wheels are able to further transmit lateral guidance because of the anti-lock control system. Unless the yaw angle speed or the angle of fishtailing of the vehicle are too great, the driver is able to keep the desired course depending on the handling properties of the vehicle. If the speed of the yaw angle or fishtailing angle exceed certain limits, even the well-trained driver is no longer able to control the skidding.
Because of the kinematics of skidding, the effective circumferential force of the wheels is also reduced with an increasing fishtailing. The ABS control, hence, assumes an apparent instability caused by a pressure surplus. The resulting pressure reduction causes the lateral guidance of the front axle to increase which, depending on the selected steering angle, results in an uncontrollable change of the driving direction. This further increases the skidding.
SUMMARY OF THE INVENTION
In order to avoid such a critical driving situation, an effective measure is a forceful braking, particularly locking, of the front wheels (brought into high slippage) after an unmistakable sensing of lateral skidding, which in turn maintains the vehicle in driving direction, i.e. maintains the direction of movement of the center of gravity of the vehicle. An additional support is changing the braking force at the rear wheels. A practical possibility is that the ABS acting on the rear wheels is at least partially shut down during skid detection. The following shows possibilities of how to sense lateral skidding. The obvious discrepancy during skidding between a high alleged vehicle deceleration and the pressure reduction time, which is high relative to the total time, can be used for sensing the skidding when an appropriate threshold value is selected.
A possible starting point is forming the quotient of the sum of the differences of reduction and build-up time at the front and rear axle, and the total time T of the current control procedure, as expressed in the following equation: ##EQU1## If SLQ reaches a prescribed threshold, this is used for detection of the skidding situation. Practical driving test showed that the difference of SLQ with respect to different roads is particularly clear, particularly on roads which permit a rapid build-up of lateral guidance and, hence, must be considered as being critical for skidding. This ensures an unmistakable sensing of the driving situation, particularly when the wheel curves characteristic for skidding are incorporated as a decisive criterion.
Another possibility of detecting lateral skidding is provided by the signals of analog acceleration sensors which describe the kinematic curve in both longitudinal and transverse direction of the vehicle. The analog signal as well as the differentiated form respective thereof can be used for sensing. Moreover, in connection with the following equation: ##EQU2## (aq: transverse acceleration; v.sub.F : vehicle speed; t.sub.1, t.sub.2 : control times( a skidding threshold is indicated when a prescribed threshold value S is exceeded (.vertline.S.sub.W .vertline..gtoreq.S).
Provided the signals of the steering angle .delta., .delta. can be supplied, the functional relationship of the yaw angle .beta.(t, .delta., .delta.) with .delta. and .delta. can be used and the follow
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Demel Herbert
Muller Elmar
Schaufelberger Rolf
Black Thomas G.
Park Collin W.
Robert & Bosch GmbH
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