TROY, Mich. – Forget the stopping power of S-cam brakes controlled by air. Meritor Automotive has seen the future of braking systems – and that future is lightweight, electronic and fully integrated into the vehicle’s operating system.
Within a decade, that could mean more automated braking, and by 2015, Meritor plans to have a “super-efficient” stopping system that reaches far beyond what most truckers think of as brakes today.
“It is safe to say that the accelerated pace of change in stopping systems will result in some exciting innovations in the next few years,” said Walter Frankiewicz, vice-president and general manager, worldwide braking systems, during a recent presentation to the trade press. “Ten years from now the system is going to be a lot different from what it is today.”
Although much of this new technology already exists, Frankiewicz was quick to add that the industry has a long way to go in terms of acceptance before the “super-efficient” stopping system is a reality.
An element that should have no problem gaining acceptance is lightweight brake components. Frankiewicz said that lightweight drums currently account for 20 per cent of the North American market, but Meritor expects that level of penetration to “increase significantly” over the next several years. Toward that end, Meritor plans to double production of its SteelLite drum to meet demand.
“What we are experiencing now is good news for the customer, in that slightly higher priced lightweight drums quickly pay for themselves in terms of increased safety and reliability,” he said.
In addition, Frankiewicz announced that Meritor plans to put a new lightweight hub, called the DaytonLite Hub, into production later this year. Made of ductile iron, the DaytonLite design incorporates improved casting and machining to achieve a hub that is 20 per cent lighter than a standard ductile iron hub and 50 per cent stronger than aluminum hubs.
Given the increasing pressure on truck operators to lower operating costs, Frankiewicz believes lightweight brake and wheel components will soon overcome the cost/benefit barrier.
“These lightweight components together add up to more than 300 lb. of weight savings on the typical tractor-trailer combination,” he said. “The cost savings for a typical tractor-trailer combination in a year amounts to over $2,000, easily justifying the expense.”
Air-disc brakes are another braking technology that already exists, but there are still hurdles to acceptance, Frankiewicz said. Air-disc brakes have, in fact, been available for heavy-duty trucks for more than 20 years and they are widely accepted in Europe, where drum designs are more expensive.
“In Europe, OEMs have been developers of proprietary drum brake design in the past. That meant the incremental cost of air disc brakes was not that significant and could easily justify a move from drum brakes.” He said. “In the U.S., on the other hand, the cost/performance gap is much wider. OEMs depend on independent suppliers, like Meritor, for brake design. And the high volume of standard brake design means the cost of utilizing that style is lower.”
Frankiewicz pointed out that there are, in fact, many differences between the European and North American markets that have hampered the adoption of air-disc brakes on this side of the Atlantic. Among them: vehicle weight ratings are different, as are axle ratings; North American vehicles tend to be smaller and travel a lot farther on average; European cities are more crowded, with narrow roads and tighter turns; and fleets tend to drive the North American market, while OEMs drive the European market. “And our road conditions are a hell of a lot worse,” he said.
Ultimately, however, Frankiewicz believes that the inherent performance advantages of air-disc brakes will lead to their adoption for many heavy truck applications in North America. And their use will likely be driven by more stringent federal brake performance standards that will bring stopping distances for trucks more in line with stopping distances for passenger vehicles, he said. Currently, the federally mandated stopping distance for heavy-duty commercial vehicles in the U.S. is 355 feet. For cars it is 194 feet.
(Canadian brake regulations largely mirror those in the U.S.)
But another problem dogging air-disc brake technology is the “non-compatibility” issue that exists between tractors with disc brakes that are matched with trailers with drum brakes. When you couple a disc-braked tractor that has new tires, with a drum-braked trailer with worn tires, there is a greater potential for jackknifes. At the very least, the disc brakes in such a situation tend to wear out more quickly than they should, because they’re handling more than their share of the stopping power.
The key to solving this problem, according to Paul Johnston, Meritor’s director of engineering, will come with the advent of more advanced electronic braking systems, or EBS.
“EBS will be able to sense what is happening on the tractor and the trailer during a stop, then modify what it can control in that system to compensate for those variations between the tractor and the trailer,” Johnston said. “EBS will become a major enabler for air-disc brakes in the next seven to 10 years.”
EBS systems are currently available in North America as an option on Freightliner Century S/T trucks. Johnston said he expects to see more fleets spec’ EBS over the next two to five years and that trucks with “more demanding braking requirements” — like fuel tankers and intra-city tractor trailer combinations — will be the first to move to the new technology. “Acceptance in North America will be slow until the payback to the fleets can be demonstrated,” he said.
In addition to enabling the adoption of air-disc brakes, EBS will also usher in a new era of maintenance “prognostics”, Johnston said. Rather than conducting visual inspections to detect worn or faulty brake mechanisms, EBS will use electronic sensors to predict when brakes need servicing.
“A proximity sensor in the foundation brake will detect performance changes and determine when service is required, based on the conditions it is seeing and recording,” Johnston said. “The goal is to eliminate the need for the visual inspections of commercial vehicles by evolving from simple brake diagnostics to a foolproof system of electronic prognostics.”
Indeed, the next generation of electronic technologies for trucks will enable braking systems to achieve something Meritor calls “orchestrated slowing and stopping”. At the core of this approach is a concept called “multiplexed electronics architecture”, which is essentially a local area network, or LAN, that links all of the various control systems on the vehicle.
“Multiplexing allows the sharing of common data from various sensors on the vehicle, and allows for the distribution of control signals to the various sub-systems,” said Denny Sandberg, Meritor’s newly appointed president and general manager of Meritor Wabco Vehicle Control Systems. “A common data bus runs the length of the vehicle and the various sensors all tap into it. Perhaps dozens of sensors send data into the bus: engine RPM, wheel speed, yaw rate, steer angle, even infrared sensors detect objects around the vehicle.”
A central on-board computer constantly monitors the information coming from the bus, and then instantly chooses the most efficient and stable means of slowing or stopping the vehicle given the outside conditions, whether or not the brake pedal is applied by the driver, Sandberg said.
“It might mean shifting to a lower gear. It might mean modulating an engine or driveline retarder. It might mean reducing the engine RPM, or it might mean applying the foundation brakes,” he said. “All of these options, or combination of options, are what we are referring to when we talk about orchestrated slowing and stopping.”
Before any of this can happen, however, a general acceptance of EBS as the way of the future needs to occur. “It’s no secret that the only way EBS can be used today is in a redundant configur
ation with a conventional (air) system as back-up,” notes Sandberg. “That automatically tends to make it too expensive and too complex for the majority of users … The technologies of tomorrow will need to prove their worth.”
Adds Johnston: “These technologies will evolve in an evolutionary, rather than revolutionary, kind of way.” n
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