Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Patent
1996-06-07
1998-12-29
Zanelli, Michael
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
701 94, B60K 3110
Patent
active
058549897
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention pertains to a method and an apparatus for maintaining a vehicle at a specified velocity wherein an adjusting element influences the drive system independently of the driver's command.
A method and an apparatus of this kind are known from DE-OS 29 24 391. In this document, a vehicle is maintained at a specified velocity independently of the driver's command, the velocity being limited in particular to a maximum value, by the driving of an adjusting element on the basis of the difference between a preset desired velocity and a measured actual velocity. The adjusting element then takes care of changing the velocity of the vehicle.
In the known method, the action to reduce the vehicle velocity occurs only after the specified velocity has been exceeded, because only then does a difference exist. In addition, the relationship between the extent of the change in the torque generated by the vehicle's drive system to the extent of the resulting change in the vehicle velocity is different for each vehicle, for each drive system, and for each set of driving conditions.
The known method for maintaining a vehicle at a specified velocity is therefore unsatisfactory.
It is therefore the task of the present invention to provide measures for improving the method and the apparatus for maintaining a vehicle at a specified velocity, especially with a view to comfort and accuracy.
The adjusting element used within the scope of the known method is an electrical, hydraulic, or pneumatic adjusting element, which controls a final control element such as throttle valve or an injection pump lever, which influences the torque or power of the drive system and thus affects the velocity of the vehicle. The adjusting element can be installed in the conventional mechanical linkage between the gas pedal and the final control element, or, as a part of the electronic control of the drive system, it can serve as an adjusting element of an electrical control system independent of the driver's command without any mechanical connection. Especially in the case of a pneumatic adjusting element with a control cylinder driven by a proportional valve, it is necessary to keep in mind the basic principle involved, namely, that the control cylinder requires a certain minimum or maximum pressure at the beginning of the adjusting process or when there is a change in the effective direction of the adjusting process to actuate the final control element and to increase or lower the torque of the drive unit. This behavior is referred to in the following as "dead travel" or hysteresis. The known approach does not take this into account, for which reason it is not satisfactory.
Therefore, measures are presented below by means of which it is possible to improve the way in which a specified driving velocity can be maintained even when a pneumatic adjusting element is used.
A method for limiting the rpm's of an internal combustion machine is known from DE-OS 36 18 844 in which the derivative of the engine rpm's with respect to time is used to determine the rpm-reducing signal, so that it is possible to avoid overshooting the specified maximum rpm's. This approach based on the derivative with respect to time of the engine rpm's is also used to limit the vehicle velocity. This method does not provide any measures which can be taken when the specified vehicle velocity is exceeded, nor does it provide any measures associated with a pneumatic final control element, which means that it cannot provide a satisfactory solution to the problems cited above.
ADVANTAGES OF THE INVENTION
By means of the approach according to the invention, a method and an apparatus for maintaining a vehicle at a specified velocity are made available, in which a specified velocity is maintained with improved comfort and better accuracy. In particular, it is guaranteed by the approach according to the invention that the vehicle stops accelerating as soon as it reaches the specified velocity. This leads to the advantageous effect that the specified velocity is ma
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Huber Thomas
Speck Hans-Reimer
Weber Christian
Robert & Bosch GmbH
Zanelli Michael
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