ATSUGI, Japan – Nissan Motor Co. Ltd. currently is reviewing its electronic-control-unit strategy, with the aim of possibly switching to a new, less-centralized format.
No timeframe is given for the revised ECU game plan, although a senior research official warns that increased software requirements coupled with shorter lead times are creating problems for engineers.
The strategy shift would mark a reversal of sorts from the one Nissan launched in 2001, when it began to consolidate multiple functions in a standard body control module (BCM) used throughout its lineup.
“Software volume has become too large,” says Toshimi Abo, deputy general manager of Nissan’s Electronics and Power Electronics Group. “Splitting of ECUs results in substantial cost increases.”
By splitting, Abo refers to Nissan’s practice of differentiating its standard BCM and customizing its functions by model and platform.
“If we had more time to develop each model, we could handle the increased software requirements,” he says. “But as things stand today, when we send specifications to our suppliers, they find themselves under great pressure to meet shorter lead times.”
Having the BCMs dedicated to more narrow functions and designing more of them – perhaps one for each platform – could lessen cost and programming requirements, according to Abo. But the jury is still out, and the research executive offers no timeframe for any decisions.
When Nissan first launched its BCM unit, it controlled such things as lighting, wipers, door locks and mirror positioning. Since then, the auto maker has added functions such as intelligent keyless entry, engine immobilization and a push-button starter.
In fact, Nissan’s latest BCM supplied by Calsonic Corp., its main supplier, controls 50 functions, including 10 related to door locks, 12 for various warning systems and 11 for lighting.
Not included are functions for the power windows, electric seats, airbags and the climate-control system. These are controlled separately by dedicated ECUs and, according to Abo, may or may not be included in a future module, depending on whether Nissan continues consolidating functions or instead opts for greater decentralization.
“It depends on a number of factors,” he explains, “including location of actuators. For instance, if they are in the engine compartment, (they might not be suitable) for the BCM.”
Even if an ECU is tied to a sensor measuring acceleration, such as an airbag ECU, it still might not be suitable for integration, Abo says.
“While (Nissan’s) airbag ECU supplier may be good at integrating an acceleration sensor, it may not be good at integrating this ECU with other sensors.”
Calsonic Kansei supplies all Nissan BCMs except those for ‘D-segment’ cars, such as the Altima, Skyline, Cima and GT-R. Calsonic Kansei modules also are on Infiniti models, including the G and M series.
For D-segment cars, the supplier is Continental AG, which took over the business when it acquired Siemens VDO last December.
A separate underhood switching module controls driver information and multimedia functions. That unit is supplied by Yazaki Corp.
Abo says the primary reason for integrating ECUs into modules is to reduce wiring, and that could be a driver should Nissan decide to stick with its current ECU setup. While pre-BCM and post-BCM comparisons are difficult because of the expansion of functions, Abo says the 2001 Micra cut an estimated 100 wires.
Nissan’s Fuga model, which is sold as the Infiniti M45 in the U.S, employs about 50 ECUs. This compares with 65-80 for Toyota Motor Corp.’s top luxury sedan, the LS460.
In addition to Nissan compact and midsize cars, Calsonic BCMs now are employed by Suzuki Motor Corp. for the Escudo, Swift, SX4 and Splash.
