Timing and Synchronization of the Event Data Recorded by the Electronic Control Modules of Commercial Motor Vehicles - DDEC V
It is well recognized that Heavy Vehicle Event Data Recorder (HVEDR) technology has been incorporated in the Electronic Control Modules (ECMs) on many on-highway commercial motor vehicles. The dynamic time-series data recorded by these HVEDRs typically include vehicle speed, engine speed, brake and clutch pedal status, and accelerator pedal position. With specific respect to Detroit Diesel ECMs, data are recorded surrounding certain events at a rate of 1.0 Hz. In this research, controlled testing was conducted to determine the time differences between the values being generated by the sourcing sensors and the interpreted data being broadcast on the vehicle's SAE J1939 controller area network (CAN). To accomplish this, raw sensor data as provided to the ECM was monitored, as were the subsequent J1939 CAN transmissions from the ECM.
The use of Heavy Vehicle Event Data Recorders (HVEDRs) in collision analysis has been recognized in past research. Numerous publications have been presented illustrating data accuracy both in normal operating conditions as well as under emergency braking conditions [1,2,3]. To date, the bulk of this research has focused on HVEDRs incorporated into the Electronic Control Modules (ECMs) employed by various manufacturers to monitor and control engine operation. Oftentimes, data associated with engine diagnostic faults include vehicle speed and driver input parameters that are later used in a collision analysis. In addition to the ECM, other electronic control systems may store data associated with fault conditions. For example, the Antilock Braking System (ABS) Electronic Control Unit (ECU), which is tasked with electronically controlling brake application air pressure to reduce wheel lockup, is such a unit that has the ability to store diagnostic information.
It has been recognized that Event Data Recorder (EDR) technology incorporated into the Electronic Control Modules (ECMs) of on-highway heavy truck engines can be a benefit to motor vehicle collision investigation and reconstruction [1,2,3,4,5,6,7]. Such beneficial features include the snapshots recorded by many Caterpillar engines. These snapshots, which are triggered by engine faults, operator input, or by what is called a “Quick Stop,” record engine operation and parameters surrounding the event. Past research has reported that while snapshot data are accurate, the documented event time may be off by 24 hours in some ECMs, notwithstanding the module's clock settings being correct . Furthermore, other research has suggested that some modules may report the time interval between data points at approximately two times the actual duration .