Analysis of Pre-Crash Data Transferred over the Serial Data Bus and Utilized by the SDM-DS Module

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Analysis of Pre-Crash Data Transferred over the Serial Data Bus and Utilized by the SDM-DS Module

Everest, Brian / Bare, Cleve / Floyd, Donald / Nunan, Douglas

The primary function of an airbag control module is to detect crashes, discriminate and predict if a deployment is necessary, then deploy the restraint systems including airbags and where applicable, pretensioners. At General Motors (GM), the internal term for airbag control module is Sensing and Diagnostic Module (SDM). In the 1994 model year, GM introduced its SDM on some of its North American airbag-equipped vehicles. A secondary function of that SDM and all subsequent SDMs is to record crash related data. This data can include data regarding impact severity from internal accelerometers and pre-crash vehicle data from various chassis and powertrain modules. Previous researchers have addressed the accuracy of both the velocity change data, recorded by the SDM, and the pre-crash data, but the assessment of the timing of the pre-crash data has been limited to a single family of modules (Delphi SDM-G). This paper addresses the operation and performance of another family of General Motors SDMs; the SDM-DS and its utilization of the Class 2 intra module serial communication bus.A series of vehicle test maneuvers were conducted while injecting non-deployment crash pulses directly into the SDM. These tests include acceleration, braking, and mixed acceleration and braking maneuvers. Pre-crash data was recorded directly from the serial data bus using a passive monitoring tool. Vehicle dynamic data was recorded by independent on-board instrumentation. The timing of the SDM's recorded data was compared with data collected from the serial bus as well as the recorded vehicle dynamic data. Evaluation of this data provides a better understanding of the timing and asynchronous nature of the pre-crash data recorded in the SDM.