The antilock braking system (ABS) fitted to modern passenger vehicles is intended to provide reliable and efficient braking under critical road conditions or in emergency situations. Thus, ABS-equipped vehicles should remain steerable and maintain directional stability in the event of emergency braking. The ABS on vehicles operates on the principle of detection of brake lockup and release of the lockup to prevent an uncontrollable skid developing on sealed roads. However, on gravel roads or snow-covered roads braking distances can be reduced if brake lockup occurs and a wedge of gravel or snow is allowed to form in front of the wheels. The intervention of ABS prevents the wedge from forming to any significant degree, thereby extending the braking distance. An investigation was carried out of a method of discriminating between sealed and unsealed road surfaces in which a signal can be developed so that an alternative ABS algorithm can be applied specifically for gravel-covered surfaces. An attempt was made to identify and measure the buildup of gravel in front of the wheel directly, using an infrared distance-measurement sensor. Initial tests have shown that the system can provide a signal to the ABS, which will allow a timely response to enable intervention in the activation of the algorithms in the ABS. This paper is also available on CD-ROM (see C 30152 CD-ROM).
Abstract