Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1999-06-14
2001-03-20
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C180S197000, C303S171000
Reexamination Certificate
active
06205392
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of determining a vehicle deceleration or acceleration.
BACKGROUND OF THE INVENTION
To determine the deceleration or acceleration of a vehicle, it is known in the art to employ acceleration sensors which have an inertia element that is displaced from an inactive position when acceleration or deceleration occurs.
An object of the present invention is to determine a vehicle deceleration or acceleration at any time and in all driving situations without additional sensors by way of wheel sensor signals alone.
SUMMARY OF THE INVENTION
In order that a prevailing vehicle deceleration or acceleration can reliably be determined by way of wheel sensor signals, the wheel sensor signals to be taken into account must satisfy defined requirements. These requirements include that the wheel or the wheels whose circumferential speed is made the basis of determination of a vehicle deceleration or acceleration do not greatly differ from the vehicle speed. The wheels must not exhibit excessive acceleration or deceleration values and must have a sufficient adhesion with the road surface.
Filtering the deceleration or acceleration values obtained smoothens unplausible peak values.
One indication that a vehicle wheel behaves approximately like the entire vehicle in terms of its speed is that this wheel is not subjected to a brake pressure control operation, i.e., does not exhibit excessive slip. If, however, all wheels undergo slip control or any other brake pressure control operations, it is possible as an auxiliary means to select those wheels which are in a pressure increase phase again after a slip control operation. Such a pressure increase phase indicates that the wheel concerned no longer has a locking tendency and obviously has a sufficient adhesion.
During braking with brake slip control, when all wheels undergo slip control, a second type of calculation which, due to the occurring braking, always applies to deceleration only, can additionally be performed in parallel to the above-described type of calculation of a vehicle deceleration or acceleration. A single wheel is chosen which exceeds a defined deceleration threshold. Pairs of values which are made up of the point of time and instantaneous single wheel speed are produced, and a speed gradient is calculated in each case from two such pairs of values. The pairs of values may of course originate from different wheels.
The first value of vehicle deceleration or acceleration determined can develop from averaging the vehicle deceleration or acceleration determined by the first type of calculation, and the gradient.
In the further course of performing the second type of calculation, there can be carried out a time filtering operation with the vehicle deceleration or acceleration values previously calculated in this way so that the averaging with the value of the first type of calculation becomes unnecessary.
To produce gradients, preferably such points of time are determined where the current gradient has an extreme value. The result is quasi a smoothened speed curve so that the vehicle deceleration does not make unplausible jumps. Such jumps typically occur only with the single wheel speeds because these pass through different phases during slip control. This has little signifying value for the vehicle deceleration, however.
It is advisable for the same reason not to position the points of time for the pairing of values too close to one another because the single wheel speeds may possibly have major discrepancies in time. That is to say, a minimum distance between the selected moments will also smoothen the curve of the vehicle deceleration.
If none of the wheels satisfy the criteria for being chosen for the above-mentioned types of calculation, the last determined value of vehicle deceleration can be maintained for the time being until a new value can be found.
This way, it is ensured at any time that a calculated value for the vehicle deceleration or acceleration prevails which is very close to reality.
This offers a number of advantages. For example, knowing the present vehicle deceleration or acceleration permits an infinitely variable and permanent evaluation of the road surface friction coefficients during brake pressure control, traction slip control or also yaw torque control in order to improve the control quality. The respective control can be adjusted better to the present driving situation by selecting respectively appropriate algorithms. Brake pressure increase and decrease may be better adapted to the actual friction coefficient which is easier to determine. Special road surface conditions, such as different friction coefficients on the left and right vehicle sides, or abrupt changes in friction coefficients can be detected more quickly. The slip of the individual wheels can also be calculated better. The determined vehicle deceleration can also be taken into account as the basis of an alternative determination of a vehicle reference speed.
A more detailed explanation of the idea of the present invention will now be presented by way of the description of an embodiment for determining the vehicle deceleration during brake slip control.
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Search Report of the German Patent Office for Application 19642122.5.
Dornseiff Manfred
Lehmer Ronald
Woywod Jurgen
Continental Teves AG & Co. oHG
Nguyen Tan
Rader & Fishman & Grauer, PLLC
Tran Dalena
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