Manufacturers Standardize on Link For Truck, Trailer Communication

TRAILER MANUFACTURERS have joined truck manufacturers in a move intended to ensure that future tractors and trailers will be able to communicate with one another.

The Truck Trailer Manufacturers Association board of directors voted to recommend the use of the Intellon P485 computer chip to handle tractor-trailer communications. The chip will make it possible to send a trailer ABS malfunction signal from the trailer to the cab of the tractor, fulfilling the National Highway Traffic Safety Administration (NHTSA) mandate that will become effective March 2001. Perhaps more importantly, however, it will clear the way for a wide range of other electrically powered devices to be mounted on trailers-without requiring a change in the standard seven-pin connector.

While the TTMA board simply recommended the use of a specific computer chip for tractor-trailer communications, the action strengthens the position of PLC4TRUCKS in its effort to become the tractor-trailer communications standard. The system, one of four that are competing for use on trucks and trailers, is the only one that uses the Intellon chip.

The TTMA decision, combined with a previous endorsement by the Truck Manufacturers Association (TMA), means that PLC4TRUCKS is well on its way to be coming the de facto standard.

Other industry groups, particularly the American Trucking Associations and The Maintenance Council, also are weighing the merits of the different systems. TMC scheduled a major session on the subject for its summer meeting June 22-24.

Trailers of Babel The ultimate objective of these industry groups is to make sure that any tractor and trailer will be able to communicate when connected. A universally accepted standard is essential if the trucking industry is to avoid having a diesel-powered Tower of Babel in its future.

"The recommendation is our attempt to make sure that tractors and trailers will be able to talk to one another," explains Dick Bowling, TTMA president. "Our engineering committee evaluated the presentations of all suppliers. None of the four are compatible with the other. To mix and match tractors and trailers, the systems have to be the same. We recommend the P485 chip because of its ability to handle future needs and the fact that it utilizes current Society of Automotive Engineers protocol."

The TTMA board did not endorse PLC4TRUCKS specifically. "It was the chip and its protocol that was important," Bowling says. "Our recommendation does not restrict suppliers from doing anything. But we must have compatibility between tractors and trailers. That's why we recommended the use of a particular chip, rather than endorse a specific system."

Choosing a System TMA, however, was more specific. It recommended the multiplexing technology of PLC4TRUCKS as the method for providing two-way data communication between tractors and trailers. TMA is the trade association for the manufacturers of medium and heavy trucks. Members include Ford, Freightliner, General Motors Corporation, Mack Trucks, Navistar International Transportation Corp, PACCAR, and Volvo Trucks North America.

"This was a lengthy process," says Bill Leasure, TMA executive director. "Our electronics committee spent a great deal of time evaluating the options. We could have dealt with this issue simply by filling the immediate need to illuminate an in-cab ABS warning light, but we didn't think it was necessary to go through this procedure a second time. As truck manufacturers, we decided to select a system that meets the needs of fleets now and in the future.

"We found ourselves in the unusual position of having to recommend one system if the tractor to trailer electrical connection is to remain generally compatible-regardless of vehicle make."

NHTSA requires manufacturers to have an in-cab ABS malfunction lamp in place by March 1, 2001. While NHTSA does not specify how this is to be done, trailer customers have "mandated" that the signal travel through the existing seven-pin connector.

In response to the issue, TMA made several recommendations. Among the topics:

* Communication technology. TMA recommends the use of the communications techniques provided by the P485 chip developed by Intellon Corporation. The association believes the P485 chip has the highest data throughput among available technologies. This enables it to meet short-term needs as well as anticipated needs for tractor-trailer communications. Another plus is that PLC4TRUCKS uses the same message structure and content already defined in the Society of Automotive Engineers (SAE) Recommended Practices J1708 and J1587.

* Communication circuit. TMA recommends that the ABS malfunction signal travel on the same circuit as the one delivering continuous power to the ABS. While proponents of other technologies had reasons for using other circuits, TMA believes impedance is less of a problem when the ABS circuit is used.

* Initial architecture. TMA wants the communications capabilities to be integrated into the ABS tractor and trailer electronic control units (ECUs). Leasure says having the chips inside the ECUs reduces costs. Having everything inside the ECU also improves accountability. TMA also recommends that the trailer ABS control unit send the malfunction signal to the tractor ABS control unit. The tractor ECU then would send the signal to the in-cab lamp. The bulb-check function that NHTSA specified also would be handled by the tractor ECU.

* Electrical performance. The system should comply with SAE J5524R100 and SAE J1113/41 (Class 5) which establish limits for radiated emission from vehicles and conduct radiation in vehicles.

Consorting the Consortium As is the case with the other technologies being considered, PLC4TRUCKS will enable manufacturers to comply with NHTSA's requirements of an in-cab malfunction lamp-using a single J560 connector.

The system is the result of efforts from a wide range of companies. Included in the PLC4TRUCKS consortium that has been led by Freightliner Corporation are Wabash National, Meritor WABCO, Cummins Engine, AlliedSignal Truck Brake Systems, Parasof Computing Solutions, Vansco, Eaton Corporation, Midland-Grau, Dialight, Federal Mogul, Phillips Industries, Qualcomm, Kysor Medallion, Thermo King, Highway Master, Air-Weigh, Vehicle Monitor Corporation, and Intellon Corporation.

Production of the chips is on schedule, according to Kurt Kyvik, director of marketing communications for Intellon Corporation. The company began shipping the P485 chips to ABS manufacturers June 1. ABS manufacturers are scheduled to integrate the chips into their products in time for testing this winter. If that timetable holds, PLC4TRUCKS will have two winters of testing before the March 2001 implementation date.

TMA is not alone in its recommendation of the system. Ryder announced its support of PLC4TRUCKS. "As an end user, Ryder is taking this leadership position to help establish a much-needed industry standard," the company announced. "We are confident the PLC4TRUCKS technology will meet applicable regulatory requirements without the need for an additional connector, that it ensures compatibility between tractor and trailer, that it allows sufficient time for testing to validate the technology, and it meets projected tractor-trailer communication needs."

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