PLC4TRUCKS Hits A Snag

Plans for trailer data network threatened as deadline nears.It seems like a relatively minor technical issue - light a warning light in a tractor cab if a trailer's ABS system fails. For a variety of reasons, some technical and some competitive, a federal safety requirement mandating such a light has turned into a major headache for vehicle manufacturers and their ABS suppliers. And now the agency

Plans for trailer data network threatened as deadline nears.

It seems like a relatively minor technical issue - light a warning light in a tractor cab if a trailer's ABS system fails. For a variety of reasons, some technical and some competitive, a federal safety requirement mandating such a light has turned into a major headache for vehicle manufacturers and their ABS suppliers. And now the agency responsible for enforcing that regulation says that if the industry doesn't come up with a workable plan very soon, it will impose a solution in time to meet a March 1, 2001, deadline.

While the warning light issue may seem like a supplier problem, fleets are the ones that will ultimately have to live with and pay for whatever solution is devised. And as simple as it may seem, bringing trailer ABS diagnostic information into a tractor cab involves some complex technological issues that will have a major impact on future trailer development and fleet productivity. A quick fix or misstep at this stage could have serious implications for fleet operations for years to come.

Initially, the National Highway Transportation Safety Administration (NHTSA) ordered trailer makers to equip trailers with ABS and provide in-cab warning lights by March 1, 1995. At the urging of the industry, NHTSA pushed the trailer ABS requirement back three years. Recognizing the technical hurdles of "lighting the light," the agency further postponed the in-cab warning light portion of the rule until March 1, 2001, in order to let the industry come up with a plan that would satisfy both suppliers and truck users.

A year ago it looked like the industry had come up with a plan everyone could support, and work was begun developing the hardware and software needed to meet the federal ABS light requirement. More importantly, the consensus plan, called PLC4TRUCKS, also promised to lay the groundwork for a data communications network linking the tractor and trailer through the existing 7-pin J560 connector.

In the near term, such a network would make it possible to control powered trailer accessories from the cab, including lights, door locks, liftgates, reefers, and even axle sliders and other suspension components. Further out, a standardized tractor/trailer data network would lead to an era of "smart" trailers and facilitate the move to electronic braking systems.

The plan was devised by a consortium of industry suppliers led by Freightliner and including Meritor-WABCO, Eaton Corp., AlliedSignal, Qualcomm, Air-Weigh, Midland-Grau, HighwayMaster, Mack Trucks, and others. In simplified terms, PLC4TRUCKS overlays a spread-spectrum communications signal on the ignition-switched constant power "blue line" in the trailer's wiring harness, the same line that is now used as the primary power for the trailer's ABS. The information is carried in the familiar J1587/J1708 format, which is the SAE data bus standard now used on all heavy-duty trucks.

Initially, a chip built into the trailer ABS control unit would convert any malfunction signal into a J1587 message and transmit it via spread spectrum to the blue line. The message travels through the standard 7-pin connector to the trailer where it is "read" by a second chip on the tractor's ABS control unit.

Failure messages are relayed to the in-dash warning light via a dedicated wire, and other trailer ABS diagnostic messages are forwarded to the tractor's J1708 data bus so they can be read by diagnostic tools attached to the tractor's data-bus link. Working with pending patents held by Vehicle Enhancement Systems Inc. (VES), Intellon Corp. is developing the specialized chips and software.

A development timetable, considered extremely tight by ABS and trailer makers, called for initial prototypes to be ready for tests during the 1998-99 winter months, and prototypes for vehicle testing to follow the next winter. That would give equipment makers just enough time to put the system into production before the March 1, 2001, deadline. The project met the first deadline, although just barely, and ABS manufacturers were able to demonstrate prototypes at the annual TMC meeting in March.

Working on a parallel track, SAE established a task force to set standards for the new network just as it had for J1708/1587 and the newer J1939 protocols. More importantly, the task force was asked to establish a mechanism for administering those standards, which would ensure that it remained an open system that could be used by everyone. That task force has been meeting, and up until last month, was making good progress.

While PLC4TRUCKS offers the potential for two-way communication between the tractor and the trailer, the first-generation system is only capable of sending ABS-related messages from the trailer to the tractor. It will not be able to turn on backup lights or other trailer accessories that currently rely on the blue line for switched power, nor will it be able to monitor or communicate data from other trailer systems such as on-board scales or cargo sensors. And that's where the project hit its first serious problem.

A few proprietary systems that do offer two-way trailer control and communications over the same blue line are already on the market. Qualcomm uses the line for its tethered TrailerTRACS monitoring system, while Air-Weigh uses it to communicate with its on-board scale system. Air-Weigh has also developed a two-way system called WireLink for controlling trailer accessories from the cab, and the same system is being marketed by Hendrickson Suspension Systems under the name Control Link.

PLC4TRUCKS was supposed to co-exist with these proprietary systems, but the prototype testing last winter turned up conflicts. As the name implies, the spread-spectrum communications used by PLC4TRUCKS spreads its data transmissions over a wide range of bandwidth frequencies allocated for this type of communications. The other systems use narrow portions of that same allocated bandwidth, and in essence they prevent the PLC4TRUCKS system from finding the "quiet time" it needs to send its data in the J1587 format. In other words, PLC4TRUCKS as it is now configured will not operate if one of these other systems is present.

Air-Weigh and Hendrickson have both publicly raised objections to the current PLC4TRUCKS system, and, in fact, Air-Weigh president Martin Ambros has presented his objections to staff engineers at NHTSA. In addition to the conflicts with the Air-Weigh system, Ambros told NHTSA that future "smart trailer" developments would be difficult if PLC4TRUCKS was allowed to use the entire bandwidth, especially if that spread-spectrum format was tied to J1587/J1708 protocols.

In mid-May, Paul Menig, director of electrical/electronic engineering at Freightliner and founding member of the PLC consortium, met with Air-Weigh and offered seven possible solutions to the co-existence problem. Both Menig and Ambros told FLEET OWNER that the meeting was productive and that they believed the problems of co-existence could be solved.

As for bandwidth allocation on the trailer's blue line and use of the J1587/ J1708 protocols, Menig says those issues would be best handled by the proposed SAE committee. That's where the second, and potentially more serious, problem has arisen.

As this story was being written, SAE withdrew its official sanction for the next PLC task force meeting and indicated that legal considerations concerning Intellon/VES patent and intellectual property rights might prevent it from setting and administering standards for PLC4TRUCKS. Although another technical group such as TMC might be willing to serve as a standards setter and administrator, the 2001 deadline is approaching fast.

Menig says he has discussed the situation with organization officials and is sending them documentation on earlier meetings that had addressed those legal questions. With a draft of the standards already completed, Menig hopes the organization will take those earlier deliberations and the urgency presented by the NHTSA deadline into consideration and give the project an official go-ahead.

However, if SAE sticks to its current position, there is no formal process for dealing with the objections raised by Air-Weigh and others, which places the entire PLC4TRUCKS project in jeopardy.

Officially, NHTSA staff engineer Jim Britell says the agency has no formal policy other than "we want a solution" to the ABS warning lamp issue.

However, others within the rulemaking department of NHTSA indicate that they are keeping an eye on the clock. While no decisions have yet been made, the agency is "fully aware that the industry is having problems, and (the industry should be) fully aware that we may have to take the option we considered in 1995 and impose a solution," says one source within NHTSA. "We may be forced to pick the best technology based on the information we have. And be assured, we won't wait until 2001 to do that."

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