Skid control for cars of future. Braking by computer

There is a bitter cold wind blowing across the ice-covered lake, a reminder that spring comes late this close to the Arctic Circle. But that is precisely why this group of a dozen or so test drivers, engineers, and computer programmers are willing to call this tiny Swedish hamlet their home during what most would call the worst months of the year. The six-foot-thick field of ice that is their ``office'' is the perfect place to test the latest developments in anti-skid brake systems.

``You cannot find a better place to do your testing,'' explains Hans Koch, a general manager with the German auto component manufacturer Teves, a division of ITT Automotive. ``You cannot get the same effect indoors. The ice just isn't the same.''

While that may seem a curious reason to go to all the trouble of creating a huge test facility on a frozen lake, the quality of the ice here, and the long period available for winter testing, are essential. Teves engineers want to be sure their designs will work in ``real world'' situations.

Almost hidden behind the tall snowdrifts stands a row of parked cars, a cross section of European and American vehicles, including some, such as the Chrysler TC two-seat sports coupe, which have not yet come to market. Two of the cars pull out from the pack and begin to race down a long straightaway of smooth, blue ice. Suddenly, the drivers jam on their brakes. The car on the left begins a frantic, uncontrolled spin, like a skater out of control, coming to a stop only when it plows into a snowbank. Surprisingly, the other car keeps rolling along a straight line, slowly coming to a safe stop.

Otherwise identical, there is a big difference between the two vehicles: The European-model Ford Sierra on the right is equipped with an anti-skid brake system, commonly referred to as ABS.

The basic concept of ABS is to prevent a car from losing control during braking, particularly on wet or icy road surfaces; and it does that in much the same way a good driver will pump the brakes to maintain control. Tiny sensors monitor each tire, and when an on-board microprocessor determines that one is about to spin or lock up, it rapidly pulses the brake pressure to that wheel, maintaining control even if the vehicle is turning.

Though ABS systems have been in use on commercial aircraft for several decades, they have only recently been introduced on passenger cars. From 5 to 10 percent of the cars sold in Europe this year will be equipped with ABS, along with 1 to 2 percent of the vehicles sold in North America.

``By the mid-1990s ... I think ABS will probably at least be optional on every car produced in ... North America, Japan, and Europe,'' says Ralph Reins, president of ITT Automotive, which, through Teves, has become one of the world leaders in ABS production.

ITT-Teves isn't alone, however. At least a dozen manufacturers have entered the ABS market, or plan to soon, including such major component suppliers as Bosch, of West Germany; Lucas-Girling, Britain; and the Delco-Moraine division of the General Motors Corporation. GM president Robert Stempel recently indicated his belief that ABS could be a standard feature on all GM vehicles by 1995.

What may be the final arbiter of ABS penetration is price. Today, such systems are standard features on only a few high-priced luxury cars, such as Ford's Merkur Scorpio, the BMW 735, and Honda's Acura Legend Coupe. They are $1,000 options on a few other vehicles, such as the Cadillac Eldorado.

Teves hopes to trim that price to about $450 by 1990, and ``we've got future developments we're calling $100 ABS,'' says Tom Chambers, program manager of anti-lock brakes at Delco-Moraine.

Anti-skid brakes are likely to be just the beginning of a whole new realm of electronic traction systems. Already in testing is a related development known as traction control, something described as ``a poor man's four-wheel drive.''

The Teves version, for example, adds just one additional component to the Mark IV anti-lock brake system. Instead of using the brakes to stop the car in a straight line, traction control uses the brakes, and a connection to the throttle, to allow the car to accelerate in a straight line, even on icy or sandy roads.

The capabilities of traction control were clearly illustrated at ITT's Arvidsjar test track. A BMW 325e was parked halfway up a steep, ice-covered hill. A reporter was asked to drive the car up over the slope, but no matter what he tried, the vehicle kept slipping backward. The reporter then switched on the traction control, and with virtually no effort the same BMW smoothly pulled forward.

Traction control does not work as well as four-wheel drive in off-road conditions, but it is a cheaper option - about $100, versus $500 to $2,000. It also adds less vehicle weight and uses less fuel.