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De Facto Black Boxes

Big Brother issues notwithstanding, just what are the engineering and cost consequences of the National Highway Traffic Safety Administration’s recent proposal requiring the installation of event data recorders (EDRs) in all vehicles?

Big Brother issues notwithstanding, just what are the engineering and cost consequences of the National Highway Traffic Safety Administration’s recent proposal requiring the installation of event data recorders (EDRs) in all vehicles? According to Scott Morell, engineering manager, Restraint Systems Group, Siemens VDO Automotive Corp. (Auburn Hills, MI; http://usa.siemensvdo.com) a lot of the hardware and software needed are already in place in the form of electronic control units for air bag modules. Though their primary purpose is to determine whether or not air bags should be deployed, the increasing sophistication and interconnection of vehicle electronics have made the modules de facto EDRs. Morell says that as unified protocols like the CAN bus are being used in vehicles to tie systems together, the air bag module can now access information from sensors throughout a vehicle (e.g., steering wheel angle, brake application force, and throttle position). When combined with data from built-in accelerometers, the modules can record all of the pre- and post-crash data likely to be required by NHTSA, without forcing OEMs to install dedicated EDRs. The potential sticking point according to Morell is power. Siemens’ current air bag modules include a capacitor that provides 150 milliseconds of reserve power so that the unit can continue to record if the battery is disconnected. NHTSA wants a six-second energy reserve. Providing that will mean a lot more capacitors which would potentially bulk up the module to the point that it becomes hard to package. —KEW