Controlling the wheels - a potted history

As the automobile has evolved over the last century, one problem has plagued the development for 75 years before it was resolved – a locked front wheel cannot steer so it is essential that the front, steering wheels do not lock in emergency braking maneuvers. From the moment this was realized, anti-lock brakes became the dream of all automotive engineers endeavoring to improve handling safety substantially and, above all, to retain the vehicle’s steerability during emergency braking. The automotive industry was just entering the era of mass production in 1920 when work began on anti-lock brakes but the road to success proved long and difficult. It was not before 1978 that ABS became available in large-scale production cars when Mercedes Benz developed the first-generation anti-lock braking system. Perhaps even more significant has been the rapid development of additional systems based on the knowledge gained in developing ABS. Building upon ABS, acceleration skid control (ASR, start of large-scale production in 1981) was developed to control the interplay of the longitudinal forces between tires and road surface not only under braking but, for the first time, also under acceleration by acting upon both the brakes and the engine torque. This was followed by the automatic locking differential (1985) and the innovative permanent four-wheel drive 4MATIC (1985). What all these systems have in common is the recording and limiting of wheel slip by means of advanced micro-electronics and hydraulics with the aim of improving the so-called longitudinal dynamics of a motor vehicle. The ABS signals are equally used by the Brake Assist (BAS, 1996), the revolutionary Electronic Stability Program (ESP, 1995) and the electrohydraulic Sensotronic Brake Control system (SBC, 2001). It’s an interesting read to see how the forces of human engenuity overcame the obstacles along the way.

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