Robert Boschgmbh

John Gatza

John Y Liu

Carlos Atoche

Carlos Atoche-Juarez

Sam Totonji

Michael Lindemann

Claus Beyer

Method and device for controlling the braking action of at least one wheel brake of a four-wheel-drive motor vehicle having at least one rear axle and one front axle. A first rpm signal representing the speeds of rotation of the front-axle wheels and a second rpm signal representing the speeds of rotation of the rear-axle wheels are detected. The difference between the first and second rpm signals is then determined, and braking action is controlled as a function of the difference that has been determined.

Method and device for controlling a braking action of at least one wheel brake of a four-wheel-drive motor vehicle

Under conditions which indicate all wheels are unstable, all have been in pressure decrease for a long time, and the vehicle reference velocity has been continuously negatively corrected for a long time, recovery are flags set on all wheels. If all recovery flags are set and four wheel drive axle oscillations are present and the reference velocity has not been in negative correction for too long, the gradient of the vehicle reference velocity is limited to a fixed lesser slope. If one or more recovery flags are set, other measures can be taken, including flattening of the vehicle reference velocity through gradual additions to the calculated vehicle acceleration, and giving longer pressure holds and delaying pressure increase. The recovery flag is reset separately on each wheel only when that specific wheel becomes completely stable. The presence of four wheel drive axle oscillations is determined based on the difference between the sum of the speeds of the front wheels and the sum of the speeds of the rear wheels. This difference is also filtered to determine whether or not the vehicle is in four wheel drive.

ABS control for a four wheel drive vehicle experiencing axle oscillations

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Linden, MI, United States of America

John Gatza