42-volt hangs by a wire

Automotive Design & Production, Sept, 2003

Ever wonder what was behind all of the Hype and hoopla surrounding the move to 42-volt systems? Many have suggested BMW's adoption and abandonment of electromagnetic valve actuation caused its Internet-like rise and fall, but there appears to be more to the story than that.

"Early in its development," says Colin Carter, sales director, ZF Lenksysteme GmbH, a joint venture between Bosch and ZF, "there was an expectation that the industry could move quickly toward the adoption of a full steer-by-wire system. but there proved to be a number of hurdles that prevented this from happening. "Among those were the obvious legal concerns--legislation requires a physical link between the steering wheel and the road wheels--and the cost associated with developing the accessory sensors and actuators. Relying on aerospace technology, where fly-by-wire systems are common, proved to be unworkable since there were no low-cost, highly robust pieces that could be adapted to automotive use.

"What surprised a number of people"--says Carter in a tone that left the words, "who should have known better" understood but unspoken--"were the high redundancy costs. Providing three separate systems capable of handling the steering function at a moment's notice added complexity and enormous cost. A dramatic price breakthrough would be necessary to make steer-by-wire feasible, and it just wasn't available in the late 1990s." As late as September 2001, ZF Lenksysteme expected steer-by-wire to be in series production by 2005, but OEM reevaluations have pushed that target back by a decade: "We don't expect to see steer-by-wire in production before 2010 though we are moving in that direction step-by-step." When it does arrive, he says, it will arrive on a fop-end luxury vehicle and be paired with a brake-by-wire system. The dynamic "by-wire" units can then be joined together to create an active safety and stability system with capabilities beyond what is available today.

And what of 42 volts? "There's still a need for a stable 42-volt system as an enabling technology for the various by-wire technologies," says Carter. And the costs associated with its development and deployment would best be served by pairing multiple 42-volt systems together in one vehicle.--CAS