In 1986, Mercedes launched the 4MATIC four-wheel drive system on a test ground in Rovaniemi, Finland, alongside two other, equally important vehicle dynamics components: the automatic locking differential (ASD) and acceleration skid control (ASR), which used the sensory technology made available through the anti-lock braking system (ABS), first introduced by the German maker in 1978. In a press release for the Frankfurt International Motor Show (IAA) in 1985 the company wrote: “State-of-the-art automotive mechanics and hydraulics combined with intelligent electronics now open up perspectives in the field of traction control systems that go far beyond conventional traction systems currently available. Three stepped electronically controlled automatic systems, tuned to meet various requirements, represent both the result and content of the Mercedes-Benz vehicle dynamics concept, which sets new standards in the relationship between the human and the vehicle – automatic locking differential (ASD), acceleration skid control (ASR) [and] Mercedes-Benz 4MATIC”.
Benefitting from advanced microelectronics and hydraulics for that era, the systems were able to record and limit wheel slip, thus improving the so-called longitudinal dynamics of the motor vehicle.
The first generation of 4MATIC had three selectable settings, two differential locks and self-regulating electronics. Unlike today’s variants, it was a non-permanent system, so there was a delay until all wheels were engaged. Still, it was a big step ahead in terms of stability and traction compared to rear-wheel driven Mercedes models.
The automatic locking differential (ASD) was an electro-hydraulic system, capable of measuring the speed difference between driven and non-driven wheels through a control unit. If necessary, it was able to lock the differential 100 percent to improve traction, essentially serving as a start-off assistant. It was replaced with an all-electronic acceleration skid control in the 90s.
By controlling the interplay of longitudinal forces between the tires and road surface, the acceleration skid control (ASR) limited wheel spin and the lateral sliding of the vehicle. Its main purpose was to help start-offs done on very slippery surfaces, like ice, snow or gravel.
According to another excerpt from the original press release, “the unique benefit of this Mercedes-Benz development is that they minimize the possibilities of incorrect or impaired human reactions. The recognition, decision-making and response are objectively accurate, timely and quicker than those of a human being – moreover they do not tire or distract the driver, nor mislead him into inappropriate action”.
By Csaba Daradics
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