Speaking at Mentor Graphics IESF Detroit conference earlier this month, Paul Hansen, editor and publisher of The Hansen Report on Automotive Electronics (http://www.hansenreport.com) addressed four topics that strongly influence what electrical distribution systems will look like in the coming years.
They are the German initiative to develop a 48-volt bus architecture and 48-volt components, a German initiative to rally support for a partial network solution, the ongoing integration of body electronics, and the effect of high copper prices on electrical distribution systems.
Hansen said BMW, Mercedes, Audi, Volkswagen and Porsche are promoting a 48-volt initiative to support large numbers of mild hybrid vehicles with stop/start systems, and next-generation chassis control. Higher voltage power supplies are needed for emergency situations, when braking, steering, and ESC systems must work simultaneously.
“Mild hybrid vehicles will benefit from 48-volts because with a 12-volt battery system, braking energy recuperation is limited to about two kilowatts,” Hansen told IESF attendees. “With a 48-volt starter alternator and battery you can improve this to eight kilowatts, and thus reduce fuel consumption in the whole vehicle.”
German Five automakers are also promoting partial networking technology for plug-in hybrids and electric vehicles. Industry standards are needed for a system that wakes up only the components required for charging, which then go back to sleep once charging is completed. Hansen said that without partial networking the vehicle’s ECUs would quickly exceed their specified operating life. According to Porsche, partial networking will require development of a new CAN transceiver.
Hansen said the number of body controller I/Os has grown as high as 100 discrete input channels and 250 discrete output channels in the past decade. Sixteen-bit microcontrollers with 256 kilobytes of memory have given way to 32-bit devices with a megabyte or two. He noted that the number of body controllers and their placement greatly affects the cost and weight of the vehicle’s wiring harness.
Electrical/electronic architecture tools, such as Mentor Graphics’ Capital suite, are helping carmakers optimize wiring harnesses and body control electronics, and that is leading to more integration, in Hansen’s view. Citing Delphi research, Hansen said a typical vehicle might have 40 computing centers. “If you can take that down to eight or ten, you can take out 25% to 30% of the cost,” he said. Bosch reports that carmakers are moving to either one or two body control modules (BCM) and are adding intelligence to switch inputs and actuators that communicate with the BCM. “OEMs (original equipment manufacturers) need fewer feature-dependent separate boxes that may only be used in low volumes,” Hansen said.
Hansen said the price of copper has nearly tripled since December 2008 and carmakers are working to minimize the amount of copper used in wiring harnesses. They are optimizing harness architectures, and where possible, reducing the cross section of each wire. They are also replacing copper conductors with conductors made entirely or in part from aluminum. Hansen noted that aluminum cables are 40% lighter than their copper equivalents and raw aluminum costs one-fourth as much as copper; however, since aluminum is not as good a conductor, aluminum cable must be 1.6 times larger in cross section than copper cable to maintain the same conductivity. Considering this disadvantage, carmakers and suppliers are focusing on the largest cables, which will have the greatest impact.