Ford Takes Control of Tight Curves
Curve Control technology keeps drivers on track by controlling the brake and throttle
Automotive engineers have saved countless lives by making up for drivers' slow reflexes and wandering minds with such systems as antilock braking, electronic stability control, and adaptive cruise control. This December, when the 2011 Ford Explorer gets pride of place in dealer showrooms, engineers will go even further.
This sport utility vehicle boasts new technology aimed at yet another common driver failing: taking curves too quickly. The revamped Explorer will feature Ford's proprietary Curve Control technology, which senses when a vehicle is going too fast to turn safely and temporarily takes control of the throttle and the brakes.
According to the U.S. National Highway Traffic Safety Administration, there are roughly 50 000 accidents in the United States each year that are the direct result of drivers losing control on curves. In 2009, such crashes killed more than 17 000 people.
The new technology combined with Ford's existing stability controls "provides a significant advantage over existing stability systems," says Saied Taheri, an expert in intelligent transportation at Virginia Tech, in Blacksburg, who did not work on the technology's development. Such systems are changing the nature of driving, says Taheri. "We're headed toward autonomous driving, and each of these systems—Curve Control, adaptive cruise control—is a step toward that."
Curve Control is a new wrinkle applied to Ford's existing AdvanceTrac System with Roll Stability Control, which the automaker developed a decade ago in response to a series of rollovers that occurred with Explorers outfitted with incompatible tires. AdvanceTrac uses accelerometers and gyroscopes to keep careful track of the vehicle's response to changes in momentum that would cause it to roll onto its side. These sensors—plus those that monitor the steering wheel angle, the speed of each wheel, and the engine torque—offer updates 100 times per second on the vehicle's performance to a system that brakes or spins each wheel independently to keep the car from skidding or rolling.
According to Dan Eisele, head of the Ford engineering team that developed Curve Control, the new system uses AdvanceTrac's sensors to determine whether the rate at which the vehicle is moving laterally is in sync with the driver's intent. Eisele explains that the rate of movement around the vertical axis, or yaw rate, for a vehicle entering a highway exit ramp with a 30-meter turning radius should be somewhere between 27 and 30 degrees per second. But a driver, having decelerated from over 110 kilometers per hour and feeling confident that he can guide the vehicle through the curve at, say, 70 km/h, can turn the steering wheel as far as it will go and still fail to get the yaw rate beyond about 20 degrees. The result: The vehicle ends up as many as three lane widths away from the driver's intended course.
Curve Control closes the gap between the driver's intent and the car's motion by cutting power to the engine and, as a last resort, applying the brakes to decelerate the vehicle by as much as 4.4 meters per second (16 km/h) per second.
Ford says it plans to make Curve Control a standard feature on nearly all of its SUVs, light trucks, and vans by 2015.
This article originally appeared in print as "Ford Executes Perfect Turns".