This report proposes a new frictional condition estimation technique to detect the tire friction approaching to its limit based on the wheel resonance phenomenon and a new braking force maximization control technique.
The slip of one vehicle on an expressway often causes a multiple collision accident which catches a lot of vehicles.

Within the tire frictional limit, the characteristic of slippery roads is almost the same as that of dry asphalt roads. This causes a driver to miss the danger and fail to restrain the increase of the speed. This seems to be in the background of many slip-accidents.
Through the investigation of such a background, we have found that the wheel speed vibrations with a specific frequency change as the tire friction approaches to its limit.

This vibration phenomenon was verified by analysis and experiment.
Next, using this phenomenon, we have continued a technique to detect a frictional condition before the tire friction reaches its limit, realizing the control method to maintain a maximum friction condition without exceeding a frictional limit.

Lastly, the effectiveness of the principle of this technique was confirmed using experimental equipment .
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