New Power for Trailers

PLC4TRUCKS prediction: We will see the light March 1 IT HAS BEEN YEARS in the making, but what has been called the most expensive light bulb in history should be ready to come on March 1.

But don't expect to see much else right away. Not that the light will be blinding-it's just that the developers of the system have had to be focused on one primary purpose-to meet a federal mandate for an in-cab ABS malfunction warning lamp.

For several years now, a consortium of companies has been working to meet the National Highway Traffic Safety Administration mandate to have a warning lamp in the cab of the tractor that notifies the driver if the antilock brake system malfunctions. Initially this seemingly simple requirement seemed too much for the traditional J-560 connector that links tractors and trailers because all seven pins already were being used. Something had to be done, and the option of using two connectors instead of one was not acceptable.

The result has been PLC4TRUCKS, a computer-controlled system that allows one wire to provide power for multiple functions. Thanks to significant work by a variety of suppliers, trailer manufacturers should be able to comply when NHTSA requires the in-cab warning lamp while at the same time offering additional electronically controlled devices. But how many of the potential benefits of multiplexing will be available to trailer customers

March 1 is still uncertain. "This has to be the most expensive light bulb ever built," an ABS engineer said recently. "The amount of time that people have spent developing and testing this has been incredible. And to think how simple the task seems to be-to get a light to come on. My wife can't believe this is how I have been spending my time, and neither can a lot of other people. They think we ought to just be able to have the light come on. But we really have been trying to do more than just meet the immediate need to comply with the NHTSA mandate. We want to develop a system that will provide trailer customers with capabilities that they don't have today."

Engineers took one more step toward making that objective a reality August 8 when the Society of Automotive Engineers Powerline Carrier (PLC) Communication Task Force agreed to approve a ballot setting technical specifications.

The ballot addresses such technical issues as the message structure of the communications and its electrical characteristics. With the Communication Task Force approving the ballot, the issue moves on to the Electrical and Electronics Committee of SAE en route to becoming a recommended practice.

"Getting the ballot approved by the Task Force is significant because this is where it gets the most scrutiny," says Rick Romer, engineering manager for Meritor WABCO and chairman of the task force.

Establishing a recommended practice is important in such an area as electronic data communication-particularly one designed to be shared by multiple manufacturers.

"This has been a cooperative effort on the part of a lot of companies who have had different technologies and experiences," Romer says. "Everyone has had to compromise one way or another to agree on these standards. But it has been enjoyable to work with so many people for the good of our industry."

Passing the Tests With the March 1, 2001, deadline getting closer every day, ABS manufacturers are wrapping up testing, and at least one manufacturer has started production. The testing is being performed by a variety of companies through a combination of methods: laboratory, test track, and actual fleet service.

"We are finalizing the development of the system now," ArvinMeritor's Alan Korn said in early August. "This week has been spent verifying compatibility between our system and those of the other ABS manufacturers. We want to be sure that a tractor equipped with one brand of ABS will be able to tow a trailer that uses another manufacturer's ABS."

Some of that last minute compatibility testing involves changes that ABS manufacturers have made to their systems. If one manufacturer modifies an ABS system, others may need to verify that the alteration did not affect the compatibility between brands.

"We are aiming at a moving target," says Dave Engelbert, engineering manager for trailer products at Haldex Brake Systems. "But all ABS manufacturers are designing to the same SAE standard, so the compatibility issues have been much less than they otherwise would have been."

Compatibility is but one thing manufacturers are verifying. Signals are being checked for proper amplitude. Mechanical properties must be checked. How well do they resist vibration? Are they effectively protected against moisture? How do these computer chips stand up to extremes of heat and cold?

Temperature Range Personal computer manufacturers have warned against operating their equipment under extreme temperatures. "If you are comfortable," the advice goes, "your computer is comfortable." However, the Intellon P485 chip used in PLC4TRUCKS can operate between -40 degrees and 85 degrees C (-40 degrees and 185 degrees F), according to Intellon Corporation, manufacturer of the chip.

The most fundamental question-stopping the truck-has to be evaluated carefully. Manufacturers had to be careful that the new algorithms they were required to produce for PLC4TRUCKS resulted in a braking system that was ideally balanced-effective but not overly aggressive.

Another area to be tested involved noise-radio frequency interference and electromagnetic interference. Manufacturers wanted to make sure the signals travel only along the desired path and did not venture into areas such as the ABS modulator valves. PLC4TRUCKS had to be able to keep its own signals in the specified path while simultaneously keeping outside noise out.

"The P485 chip emits a very distinct signal," says David Harding, application engineer for Intellon Corporation, manufacturer of the computer chip that serves as the brains of the PLC4TRUCKS system. He said the amplitude and frequency of the signal does not resemble noise that typically would also be found on the line. Possible sources of noise include the vehicle's alternator, turn signals, and the fan motor.

Working Out the Bugs The system has proved sound from the standpoint of such mechanical factors as temperature and vibration resistance, ABS manufacturers report. Software issues have been the biggest obstacles they have had to overcome.

Software, of course, is the messages the computer chips use for instructions. In the case of PLC4TRUCKS, chips from different manufacturers must communicate with one another. To simplify the overall system, ABS manufacturers are integrating the PLC4TRUCKS into the circuit boards of the electronic control modules that regulate the ABS. The manufacturers have been responsible for developing the software that enables their chips to talk to the PLC4TRUCKS chip.

"That has been the point of the entire game-to be able to communicate over the data bus," Engelbert says. "So many variables are involved in making it work. Success or failure may depend on something as basic as how the circuit board is arranged."

Those involved in the development of PLC4TRUCKS now consist of 23 truck, trailer, and technology companies.

ABS manufacturers generally are gearing up to start production late this fall. However, Bendix began shipping ABS with integrated PLC4TRUCKS in early August. Initial production will be strictly ABS equipment capable of lighting the light. Subsequent versions will include greater capabilities such as the ability to turn on trailer dome lights, door ajar lights, and other electrical features.

"We may introduce these one at a time, or we may release them in batches," says Jack Pohl, with AlliedSignal Truck Brake Systems. "Our primary concern right now is to meet the requirements of the regulation."

Other ABS manufacturers are waiting later in the year to begin production. This will allow them to fill the supply pipeline in time for the mandated deadline.

"We will be ready for the deadline, but we don't plan to produce PLC4TRUCKS units earlier than necessary," one ABS manufacturer says. "Some of the more progressive fleets may order early, but there will be an added cost that most customers would prefer not to pay."

Getting What You Want While the ABS manufacturers will have systems in place to "light the light," it was uncertain to what extent other multiplexing options will be available precisely on March 1. Even more unclear was what price the customer would be willing to pay.

"It's going to be driven by the customers," says David Kemp, vice-president of engineering for Dorsey Trailers. Dorsey and Wabash National are the two trailer manufacturer members of the PLC4TRUCKS consortium. "The system has potential, especially for brake monitoring and delivering information regarding refrigerated trailers. How much of that will go into trailers depends on the customer and what makes economic sense to him."

A multiplexing system such as PLC4TRUCKS makes a wide range of features possible for trailer customers. Haldex, for example, will offer a premium ABS package that will include two channels: a monitoring channel and a control channel. The monitoring channel will include warnings for low air reservoir, low tire pressure, trailer overload, temperature, door ajar, brake lining wear, and rollover. The control channel will regulate dump valves, belly dump valves, lift axles, dome lights, backup spotlights, backup alarms, loading lamps, anti-dock walk, and reset to ride.

Other manufacturers also will offer options to go along with the required ABS warning lamp.

"If customers want these feature sets, they will be able to order them from the factory," Pohl says.

Aftermarket Applications Even though a trailer has left the manufacturing plant with a certain configuration, ABS manufacturers say that it can be reconfigured later.

"Our system will drive a relay," says Eaton's Rick Youngblood. "If you want to add a device, tap into the relay. Data for dozens of things can be communicated, either as part of the ABS or through an independent system. Tire pressure, brake wear, and a lot of other possibilities will be introduced at a pace that the market demands them."

ABS manufacturers see aftermarket applications for PLC4TRUCKS. For example, should customers want to add electronic options to existing trailers, they will be able to do so. The key is the availability of inputs and outputs on the ABS electronic control module. If a tap is available, getting the system to accommodate the aftermarket electronic device will involve downloading software.

"You will be able to use existing tools such as a personal computer or handheld diagnostic tools," Pohl says. "Downloading the software from a PC will require a cable that has a parallel port connection on one end and a six- or nine-pin connector on the other. Our system also can be programmed through the J-560 connector. While we offer the ability to reprogram the electronic control module either through a data port or the J-560, we think the J-560 eventually will be the most popular way."

Trailer manufacturers, trailer dealers, and customers could reprogram the ECMs. "We are including that in our ABS training school," Youngblood says. "Eaton has 150 people in the field service department. Those interested in learning more about reprogramming the system should contact a field service representative."

Another aftermarket application of PLC4TRUCKS is the replacement of parts. ABS manufacturers point out that from the outside, today's system looks the same as one that is equipped with PLC4TRUCKS. Through the use of interchangeable parts, it is possible to make today's ABS upgradeable to PLC4TRUCKS.

"Users of today's units will get PLC4TRUCKS as replacement units," Engelbert says. "Trailers that were built between 1998 and 2001 (when ABS was mandatory but PLC4TRUCKS was not available) will regain the functionality of their auxiliary circuit."

The concept of electronic communication between tractors and trailers opens up a wide range of options that can make trailers safer and more productive. However, some of those involved in developing the initial standard technology for getting the ABS warning lamp to function question whether PLC4TRUCKS will be able to handle the demands of more sophisticated electronic products that will be designed for trailers. Perhaps the most demanding-and obviously the one with the greatest safety ramifications-is electronic braking. The 9600 baud rate of PLC4TRUCKS may not be fast enough for the time-sensitive data associated with electronic braking.

EBS Holds Potential Electronic braking systems (EBS) are one area that holds potential benefits for fleets, according to ArvinMeritor's Paul Johnston.

"Even though the concept and early versions of EBS have already been introduced, it does represent a pending revolution in braking because it brings an entirely new level of sophistication to the stopping system," Johnston says. "EBS will be a major enabler for air disc brakes within the next seven to ten years, primarily because it will help resolve the tractor-trailer compatibility issue. EBS also will provide the ability to predict when the brakes need to be serviced, taking onboard diagnostics to the next level. In effect, it is going from diagnostics to prognostics."

ArvinMeritor's Denny Sandberg cites other advantages of multiplexed electronic braking systems, including a dramatic drop in the number of wires, smaller harness bundles, substantial reduction in weight compared with conventional air brake systems, fewer moving parts, easier diagnostics, and service.

"Maintenance or potential service needs could be identified earlier, possibly while the vehicle is in operation," Sandberg says. "Above all, the greatest impact will be on the overall wear and tear of a vehicle and the improved performance and safety aspects that come with it."

ArvinMeritor currently has programs in place to develop EBS for disc and drum brakes.

"The goal is to eliminate the need for visual/manual inspections and to speed in-service inspections of commercial vehicles by evolving from simple brake diagnostics to a foolproof system of electronic prognostics," Johnston says. "The technology to accomplish this exists today. We expect to introduce a prognostics-based diagnostic system in Europe within three years. A North American introduction will not be far behind."

A New Standard Long term, many in the industry see the need for a multiplexing system beyond PLC4TRUCKS.

"There are bandwidth issues and gateway issues," says Martin Ambros, president of Air-Weigh, a manufacturer of on-board scales and multiplexing systems. "The truck bus already is loaded between 75% and 80% of capacity. We have a sea of opportunities but an hourglass data bus."

When the ABS lamp issue first was proposed, many concluded that the J-560 connector would have to be replaced or supplemented by a second connector or other communication systems such as radio frequency.

"Those issues are again being considered as we evaluate more powerful communication systems," Romer says. "It does not mean that we will have to add a second connector, but that is one of the options."

While future technology may replace PLC4TRUCKS, the system is expected to serve the industry for years to come. In much the same way that the industry wanted to preserve the J-560 connector, it will want to preserve compatibility with PLC4TRUCKS.

"The work we have gone through has been incredible," an ABS engineer concludes. "But this is only the beginning."

FOR many of us, the "black box" of vehicle electronics is a Pandora's box-one we have no idea what we will find when we open it.

Even though PLC4TRUCKS has been written about repeatedly, some of the mystery may still remain. But in just a few months, it will be standard on every truck trailer manufactured; so a working knowledge of the system may not be a bad idea.

Much like a telephone, PLC4TRUCKS uses a wire to connect the sender of the message with the receiver of the message. In this case, the wire is the auxiliary circuit (the "blue wire") that links the tractor and trailer via the standard J-560 tractor-trailer electrical connector. And like a telephone, both the sender and receiver must have a "handset" that sends the messages along the wire and receives incoming messages.

We can identify voices on the telephone because they have a tone and pitch that we know. The same holds

true for PLC4TRUCKS. The system uses a computer chip that sends a signal or "chirp" that can be recognized or understood. The signal travels from the computer chip that is included in the ABS controller. When the receiver on the tractor identifies the signal, it responds. In the case of PLC4TRUCKS, the response is one of only two things-turn the light on or turn it off.

But that is just the beginning. ABS and other manufacturers have developed systems that can control other devices. The number of these devices is limited to the number of inputs and outputs (places to plug in wires) on the controller. Just as a single radio can play multiple radio stations, a single controller can identify the frequency of incoming chirps. When it does, it responds as it has been programmed to do-monitoring brake lining wear, turning on a dome light in a trailer, letting the driver know a door is open, or a variety of other functions.

Each device takes turns communicating. The communications protocol (the "language" that the computer chips speak) includes a signal that detects when the communication line is idle. If the device detects a busy signal, it waits to communicate until the line is available. Engineers serving on the Society of Automotive Engineers Powerline Carrier Communication Task Force have addressed the issue of conflicts between devices. Different devices are assigned priorities. If a lower-priority device tries to use the line at the same time as a higher priority device, the lower priority device must wait until the line is no longer busy.

PLC4TRUCKS will make a variety of new trailer options possible.

"There are all kinds of possibilities," says Jim Hofstetter, vice-president of engineering for Great Dane Trailers. "A lot of them have real potential, especially those related to brakes, suspensions, and refrigeration units. Of course, each will have an added cost associated with them. The trailer customer will have to weigh the value and the cost in deciding which of these options to buy."

Hide comments

Comments

  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
Publish