Traction control system including setpoint slip adjustment

Details Traction control system including setpoint slip adjustment Traction control system including setpoint slip adjustment

2003-03-25

2004-12-07

Jeanglaude, Gertrude A. (Department: 3661)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

Indication or control of braking, acceleration, or deceleration

C701S070000, C701S083000, C701S090000, C303S133000, C303S167000, C180S244000

Reexamination Certificate

active

06829529

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for traction control and a corresponding traction control system.
BACKGROUND INFORMATION
When a motor vehicle is accelerated on a road surface having different adhesive friction values between the right and left sides of the vehicle (&mgr;-split), and when making a hill start in particular, the spinning of the drive wheels may result in critical driving situations. By reducing the engine torque, and also by a braking intervention if necessary, the traction control system (TCS) attempts to maintain the vehicle in a stable range and improve traction.
The TCS may be set in such a manner that the vehicle does not roll back if at all possible even when making a hill start on a road surface having different adhesive friction values between the right and left sides of the vehicle (&mgr;-split), even if the driver gives too little gas. The engine torque specified by the TCS in the initial phase of a standing start, the engine torque pre-control value, may be configured for a gradient of 15% and more and is correspondingly high. A relatively high engine speed and a correspondingly high slip threshold are required for the low-&mgr; wheel (driven wheel with low adhesive friction value) to apply this high engine torque pre-control value. If the spinning low-&mgr; wheel is braked too strongly, the engine will not reach the rotational speeds at which the required torque may be generated.
As a result of the controller adjustment made, the engine torque and tire slip are only optimally adjusted for the extreme situation used as a basis, e.g., a 15% grade. However, at a lower gradient and on a level road surface in particular, more engine torque is generated than would actually be necessary to accelerate the vehicle appropriately. Of course, the unnecessarily high engine speeds and the excessive spin of the low-&mgr; wheel reduce driving comfort. At a higher gradient (more than 15%), however, too little engine torque is applied so that the vehicle may roll back briefly.
SUMMARY OF THE INVENTION
The exemplary embodiment and/or method of the present invention provides a traction control system and a corresponding method, during which the engine speed set during a standing start is adapted to the instantaneous gradient.
The exemplary embodiment and/or method of the present invention determines the engine speed which is actually needed for starting off the vehicle and is present with an engine torque actually needed for starting off (the actually required engine torque is the torque that is exercised at the time of driving off or when exceeding a low speed threshold). A new setpoint slip value for the low-&mgr; wheel is then calculated from the engine speed actually needed. The setpoint slip is finally reduced or increased abruptly from the specified setpoint slip pre-control value to the newly calculated setpoint slip value.
Analyzing the engine speed actually needed may allow adjustment of the setpoint slip optimally to the instantaneous requirement and consequently increase driving comfort significantly. When starting off on grades of less than 15%, excessive engine roar may be prevented. On steeper gradients, however, the engine speed may be corrected upward in order to obtain adequate acceleration even on steeper gradients.
The engine torque actually needed may be determined from the point in time at which the vehicle starts to move or exceeds a specified speed threshold.
According to an exemplary embodiment of the present invention, the engine speed actually required is read out from a set of speed/torque characteristic curves stored in the system.
After the setpoint slip is abruptly reduced or increased, the setpoint slip for the low-&mgr; wheel may be reduced linearly.
In addition to the braking torque regulation, the TCS may intervene in the vehicle operation through an engine torque regulation.


REFERENCES:
patent: 6542806 (2003-04-01), Suhre et al.
patent: 6587774 (2003-07-01), Hessmert et al.
patent: 6658343 (2003-12-01), Koch et al.
patent: 6659568 (2003-12-01), Wandel
patent: 2003/0167116 (2003-09-01), Andreas

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