SOUTH BEND, Ind. – 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 testing was conducted in Michigan over the winter and there are now customer trucks using the system in the field.
Truck News 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.
“The hardware components are almost one for one,” admitted Moore. “Where we differ a lot is the logic and the way we apply it. What kind of determinations we like to make.”
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 potential 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.”
Moore said Freightliner’s ESC system will in some cases allow the vehicle to yaw a little “because you know it’s going to come back.”
The end result is a smoother intervention, he said.
“Our philosophy is you’re going to have a lot less tendency to panic a driver and have him doing things that are going to make it more difficult to anticipate,” he added.
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.
“It’s the poor man’s version of ABS,” joked Moore.
The ESC system applies as much trailer braking as necessary to stabilize the combination and keep it pointed the right direction.
Moore said Freightliner’s ESC system will slow the vehicle down to speeds the driver may think is excessive at times. It’s all to ensure he has full control of the truck before regaining speed.
“You’re going to feel it and it’s going to feel smooth,” Moore described. “It’s going to slow the vehicle down quite possibly to a point below where you think it should be. The competition doesn’t take you to that level but this is what we think is the safest way to get you out of a dangerous situation. Don’t try monkeying around with little corrections, because a big problem has happened. Go ahead and take big time control of the truck and make sure you get him completely out of it.”
In developing ESC, Meritor-WABCO quickly realized it wasn’t simply a matter of refining its European ESC system. Moore said since Europeans don’t run conventional trucks, “That would be like plugging a 110 (volt device) into a 220 (volt socket).”
Plenty of engineering went into the development of Freightliner’s new ESC system the company insists. While ESC can greatly reduce the chance of a rollover, Moore stressed no system can prevent every single rollover. That’s a point echoed by von Mayenburg, who emphasized “The truck driver will remain the key to safe heavy-duty truck operation.”
Freightliner says its new ESC system will be more expensive than Roll Advisor and Control, but insisted it will still be affordable. It will be offered on some models later this year before being rolled out across the entire line in 2006.