Freightliner is launching a new electronic stability control (ESC) system that can greatly reduce the risk of rollovers, say company officials.
The new ESC system was developed jointly with Meritor-WABCO and is based on Freightliner’s Roll Advisor and Control system. It will compete with the Bendix ESC system already on the market and will be rolled out this fall with full production underway in early 2006.
“ESC holds significant potential to reduce accidents,” says Michael von Mayenburg, Freightliner senior vice-president of engineering and technology.
Comprehensive winter testing was conducted in Michigan and there are now customer trucks using the system in the field.
Motortruck recently had the chance to test the new system at Freightliner’s South Bend, Ind. proving grounds. Driver Scott Smith explained “When we go through the (tight, high speed) turn it will sense the high lateral acceleration and it will de-fuel the engine, apply the engine brake, apply the services brakes and bring it down to a safe lateral acceleration level where it doesn’t sense there’s a potential for rollover.”
The test truck we were in was equipped with an electronic braking system (EBS), however Smith said it operated in much the same way an ABS ESC system would.
While bobtailing, we accelerated to a high rate of speed and Smith suddenly veered to the left in a maneuver that I thought would surely end in disaster. But the system intervened as he promised it would and kept the rubber on the ground — much to my relief!
Freightliner engineer Tony Moore said there are fundamental differences between the Meritor-WABCO system and Bendix’s existing ESC system.
Moore explained Freightliner’s ESC system takes control from the driver more gradually than the Bendix system and then it maintains control longer — sometimes bringing the vehicle to a complete stop.
“Our philosophy is that when a stability system has to activate, the vehicle is in trouble. The driver has done something he shouldn’t have done. He’s made some kind of mistake and at that point in time, we’re not going to give him a chance to make a second mistake, we’re going to take control of this now,” Moore explained
Because a driver instinctively reacts to a rollover situation by turning the wheel, Freightliner’s ESC system attempts not to over-correct on his behalf.
“We do it gradually because you can get into a situation where you’re actually pulsing the vehicle back and forth” as the driver and ESC system try to correct each other, Moore said. “The driver will act, the system will act, the driver will act the system will act…that’s not really a speedy way to get out of this situation. You don’t want the driver to have to go through that type of experience.”
Freightliner’s system also works a lot with the trailer, the company said.
“One of the things that will help stabilize the vehicle is to pull it from the rear so we will apply the trailer brakes,” Moore said.
While the ESC system is only installed on the truck, it has the ability to detect whether or not the trailer is equipped with ABS brakes. If it isn’t, the ESC system will pulse the trailer brakes to avoid lockup.