CDR Proces
Culling data from the airbag module’s
control unit (ACM)
Crash data are stored as a part of the EDR memory module in the control unit of the airbag module (ACM). This EDR module typically records max. 5 seconds before a traffic accident and then max. 5 seconds of the course of the traffic accident. The crash data are stored only in the case when the ACM evaluates the situation as critical and releases airbags. At this moment the accident is stored at a 200Hz frequency in the EDR memory. Taking data from the ACM module is a relatively difficult process in the case of a totally damaged vehicle. In the event the vehicle has functioning electronic circuits it is possible to obtain the data through the ODB connector. With the help of the CDR unit the data are retrieved and recorded on the accident protocol. This accident protocol contains a lot of data. Every manufacturer puts a different extent of data into the EDR. However, according to American Act 563, at least these data are always entered:
  • Delta-V, 0-250ms, every 10ms
  • maximal Delta-V, 0-300ms
  • maximal Delta-V in timeline, 0-300ms
  • vehicle speed, 5 seconds, 2 values for a second
  • engine speed, 5 seconds, 2 values for a second
  • braking ON/OFF, 5 seconds, 2 values for a second
  • ignition cycle in the time of the crash
  • ignition cycle, the data download time
  • condition of seat belts – driver (fastened seat belt, unfastened seat belt)
  • airbag condition indicator (on/off)
  • activating of the airbag module, time until activation (driver, passenger)
  • more values in the EDR memory, number of event (numbering of EDR storage events)
  • time between Event 1 and Event 2
  • status of EDR data downloading (downloaded complete without errors – yes/no)

Scheme of airbag module’s control unit
(Toyota Prius) Toytoa-ACM