ABS valuable for interacting with new safety systems
Feb 1, 2004 12:00 PM
ARVINMERITOR'S Charlie Schott discussed rollovers and how they continue to pose a risk for tank trailers. However, he pointed out that research has produced several safety options for tractors, such as an automatic traction control and roll stability control.
A cruise control system for tractors is under development that will adjust speed and apply brakes, based on the distance of the vehicle in front.
A tractor stability enhancement is important because it can help prevent rollovers. Although there are not a large number of rollovers reported, he noted that when they do happen they are costly.
Stability systems for tractors are ABS based and detect wheel speed, and control the engine throttle retarder, drive axle, brakes and trailer axle brakes.
“The more sophisticated the system is, the more controls there are,” he said.
An automatic traction control system notifies the driver that a lower center of gravity is needed, or to reduce speed in order to avoid a rollover. Trailers without ABS brakes can be modulated from the tractor so they don't lock up if they aren't ABS.
“We're measuring the lateral force on the tractor,” he said. We're looking at vehicle speed, engine torque. We take these things into consideration to get a calculated figure on where the vehicle is to determine if there is a risk of rollover.”
The system reduces engine torque, applies retarder, if the engine has one, and applies brakes. “The intention is to get speed down as quickly as possible,” he said.
Once the vehicle is out of the situation, the tractor and trailer movement returns to normal. Because of the early warning, the driver only feels the transition as the engine changes.
Another value of the early warning system is that it conditions drivers so that they will begin to anticipate when they should slow down. “It's an aid to the driver, just like ABS is, but the driver is still the most important part of that combination vehicle.”
As for systems designed for trailers, he said they can work independently of the tractor, if necessary.
Some of the systems that detect the trailer load can only work with an air ride suspension, not spring suspensions, he said.
As the trailer starts to lean, one side measures the force and will apply quick brake pulses to inside the wheels. The driver sees a quick deceleration, then brakes are applied to wheels on the other side of the trailer. When the situation improves, the system back out for the driver to take over.
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