Manufacturers May Blend Braking Systems as Autonomous Technologies Gain Interest
This story appears in the June 20 print edition of Transport Topics.
The growth of technological systems used in autonomous vehicles in the United States, such as adaptive cruise control and self-steering, could speed the adoption of electronic braking system technology, which sends an electronic control signal to activate brakes. But how the systems are used in the United States likely will be different than the electronic braking systems that are widely used in Europe, brake manufacturers said.
In the United States, manufacturers could take more of a hybrid approach — combining air brake and anti-lock braking technology with features from electronically controlled braking systems.
“More and more features that are in today’s electronic braking systems are becoming part of conventional anti-lock braking systems,” said Richard Beyer, vice president of engineering, research and development for Bendix Commercial Vehicle Systems, based in Elyria, Ohio. “As the evolution continues, the functional lines between electronically controlled braking systems and conventional ABS will get closer.”
Mary Aufdemberg, director of product marketing for Freightliner Trucks, a unit of Daimler Trucks North America, said that with the advent of ABS, electronic stability control, adaptive cruise control and collision avoidance systems, electronic braking system technology is being used in situations that don’t require driver input.
“Thus, vehicles are increasingly using electronic braking systems when the input does not come directly from the driver’s foot,” she said. The systems can be initiated by specific modules, such as the radar control module or the stability control module, sending a direct electrical connection to the individual brake valves on the respective axles, she added.
Freightliner used electronically controlled braking systems, often called brake-by-wire, in its autonomous Inspiration Truck, which was introduced last year in Nevada.
“The vehicle represents a true brake-by-wire, steer-by-wire vehicle,” Aufdemberg said. “However, even with the Inspiration Truck, a driver is able to initiate a braking event with the foot pedal, which utilizes an air braking system, not an electronic braking system.”
Aufdemberg said today’s Freightliner Class 8 tractors use standard air brakes, and she does not see this changing.
“For a driver-activated braking event, the industry will continue to rely on air brakes,” she said.
Jon Morrison, president of Wabco’s Americas business unit, said many autonomous vehicle requirements in North America can be accomplished with anti- lock braking systems.
“Things like autonomous emergency braking requires us to make adaptations to the control methodologies,” he said. “With electronic braking systems, you’re going to get a bit more precision, but an anti-lock braking system can do it.”
Wabco, which has U.S. headquarters in Rochester Hills, Michigan, launched electronic braking systems in Europe in 1996.
“It has been widely used in Europe due to an imbalance issue between the tractor and the trailer and the need for greater brake control,” Morrison said. “In the U.S., the truck and trailer combinations tend to be more balanced and don’t require as much specific braking control as the European combinations.”
In the United States, a trailer makes up two-fifths of the actual braking of the whole vehicle, whereas in Europe, it is three-fifths, Bendix’s Beyer said. As a result, the United States has less need for the type of connection used in Europe.
Nevertheless, benefits are associated with an electronically controlled braking system, including better overall braking performance, brake balance and response and brake system prognosis. The systems also provide a platform for other technologies, such as stability control, said Dave Engelbert, chief engineer for Haldex, a brake manufacturer based in Kansas City, Missouri.
In addition, there are “inherent things you can do with the electronics that, at least with our current ABS 121 systems, you can’t do on our vehicles,” said Mike Hasinec, vice president of maintenance support at Penske Truck Leasing, based in Reading, Pennsylvania. Penske ranks No. 14 on the Transport Topics Top 50 list of the largest logistics companies in North America.
Scott Perry, vice president of supply management and global fuel products at Ryder System Inc., said switching the control to electronic braking increases the responsiveness and connectivity.
“The roll stability control, fraction control are things the analog braking system can help with. It is just that the electronic braking systems take it up a level. It is like an anti-lock braking system on steroids,” Perry said.
That translates into how much force can be applied before the system locks up, he said.
“I haven’t found that it is materially different, it is just a little better,” he said, adding that the drivability when brakes are applied is slightly increased with electronic braking systems. “The ability to steer through a safety event is greater.”
With traditional braking systems, if a driver tries to brake and steer at the same time, “it can exacerbate the lockup process and the skidding,” he said, noting the anti-lock braking helps but the electronic braking system “does it even better.”
Ryder’s Supply Chain Solutions business unit ranks No. 13 on the Transport Topics Top 100 list of the largest for-hire carriers in the United States and Canada.
C.R. England Inc., a refrigerated carrier based in Salt Lake City, has invested in safety technology that uses electronic connections to the braking system.
“With adaptive cruise control and collision avoidance, there is radar in the front bumper that will tell the vehicle to apply the brakes or to take the accelerator off,” said Doug Kading, vice president of maintenance for C.R. England, which ranks No. 23 on the for-hire TT100.
Wabco’s Morrison told Transport Topics that having the electronic control on the wheel end could result in less brake and lining wear because not all brakes are activated in the same way. A hybrid approach or simpler system also would result in fewer air supply lines, which can provide a slight weight savings, he said.
Fewer air supply lines have other benefits as well. “There are quite a few air lines on a Class 8 tractor, and you have all of these opportunities for air leaks with these connections. It is a pretty high out-of-service item when people go through the scales,” Penske’s Hasinec said.
Fleets said they welcome the safety improvements electronically controlled braking systems could provide. The adaptive load-sensing capabilities of ECBS can sense how heavily or lightly the vehicle is loaded and what type of application pressure is necessary to stop the vehicle completely, Hasinec said. In addition, response time is improved because electronic signals travel faster than air, he said.
Perry said the responsiveness of an electronic system versus a pneumatic system is a fraction of a second better. “Whenever you have fractions of seconds to respond, any improvement is [an] additional safety factor,” he said. “You can see where the electronic braking systems would play a role if we’re going to be taking an additional incremental step forward making the stopping distance shorter.”
Ross Froat, manager of engineering and information technology programs for the Technology & Maintenance Council of American Trucking Associations, said electronically controlled braking systems also could result in weight savings by removing the air tanks, compressor and the gauges.
“You’re taking stress relief off of the engine. Fuel savings could also come from it, and it could cut emissions,” he said, adding that these systems could help manufacturers meet greenhouse-gas requirements.
Engelbert told TT that weight savings could increase if current regulations — which require a backup pneumatic braking system if a major electrical malfunction occurred — were eliminated.
The need to lay electronic braking technology over the top of pneumatic systems adds costs for carriers, Kading said. “Because electronic braking control isn’t regulated and mandatory yet, if you use it as a carrier, you have to lay it over the top of an existing air braking system at an additional cost. Responsible carriers do it, but it is another thing that makes the playing field not quite as level.”
Ultimately, the cost performance curve is what will drive adoption of electronically controlled braking systems in the United States, Beyer said. “Do you need enough of those features to warrant the additional cost of putting it on the vehicle? Fleets don’t want to pay for features they’re getting that they don’t need,” he said.
An anti-lock brake solution is about two-thirds of the cost of an electronic solution, Beyer said. “In the end, there is no panacea. Electronic braking systems have more capability than a standard anti-lock braking system, but if you look at the ABS today, it probably does 50% of the functions of electronic brake systems.”
Costs would depend on how the equipment manufacturers approach the vehicle layout, Morrison said. “For the business case, you do get some incremental improvement, but from a cost perspective, anti-lock brake systems work fine and there is no reason to change,” he said.
Meanwhile, as ECBS technology and its features grow in the United States, a need will arise to improve and increase training for service technicians because the equipment will have more functionality, Morrison said.
But training on new technology can be a challenge, Hasinec said.
“Technicians have to wrap their heads around how it works,” he said. “Then you have to get the proper tooling and the right diagnostic software. There are growing pains the first few years a new technology comes out on a chassis.”
Wabco has worked to ensure there is not a material difference in the components required for an anti-lock or electronic braking system, Morrison said.
