iTECH: Data Capacity Expansion
Powerful Telematics Drive Next Leap Forward for Truck Electronics
The rise of onboard diagnostics related to emissions controls is a major cause of increased demand for communications capacity on trucks, DeGrant said. The U.S. Environmental Protection Agency and the California Air Resources Board insist that trucks be equipped with sensors to monitor diesel emissions so the vehicles are in compliance with antipollution rules. Those sensors must then deliver their findings — via J1939 — either to an in-cab computer or the engine control module. With the proper electrical hookups for communications it can run the length of one or two trailers, for a maximum length of 40 meters, or about 133 feet, he said.
It is these systems, plus fleets’ increased use of telematics, that are pushing the industry to the shift to the higher capacity data bus, said Dan Fuglewicz, director of automotive and embedded technology for Xata Inc., Eden Prairie, Minn., which develops software for the trucking industry.
“Users want all types of real-time data from their truck — operational data, fault data, safety system data, driver data,” he said. “They use this data to better manage and control their operations and costs, and they require as much data, as fast as they can get it. It’s actually the telematics users — fleet managers, maintenance managers, technicians, and even drivers — who are driving data capacity.”
A key question for manufacturers is how to equip trucks to handle all that data.
Navistar Inc., Lisle, Ill., which makes International trucks, has been involved in research being done by SAE International, formerly the Society of Automotive Engineers, on advancements to the J1939 bus, said Eric Swenson, the truck maker’s manager of vehicle requirements. He said SAE has published “data bus topology,” or guidance, on the move to 500 kBd.
DeGrant has been following the SAE’s work, and believes truck makers have two options: doubling the capacity of a single wire or running two 250 kBd wires in parallel. DeGrant said he prefers the twin option, one data bus dedicated to critical communication, such as braking, and the other set aside for more ordinary data.
Jong says that while a dual 250 kBd bus strategy can work in the short-term, it won’t take long for the industry to outgrow the 250 kBd standard.
“At the rate new, sophisticated features are being added to the powertrain and active safety systems, the ‘mission critical’ J1939 250 kBd bus for ABS and powertrain will still reach its critical state in the near future,” he said. “The long-term strategy for meeting increased customer demands on energy efficiency and safety . . . is to increase the ‘mission critical’ J1939 bus to 500 kBd. In the long run, this, combined with a separate J1939 250 kBd ‘nonmission-critical’ bus, will allow room for future growth while ensuring reliability.”
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