How To Translate Steer, etc From EDR to vehicle responses

Decided this might be a good time to add a specific topic on Electronic Data Recorders (EDR) and/or Crash Data Recorders (CDR)
MSI
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How To Translate Steer, etc From EDR to vehicle responses

Post by MSI »

From INCR forum
  • Q: I would like to be able to translate a steer angle as shown on the CDR report to the change in the heading angle from the original forward that would occur if the steering wheel were held in that position. Can someone help me understand how this might be done. I can use an exemplar vehicle to do whatever tests might be necessary, but if there is an analytical methodology I'd like to understand that first
A; First taking a look at straight forward approximations using simplified equations is a good start. As mentioned in the INCR forum thread and there are several others (i may post up some in a separate link next week, rattle my cage if interested)

I also recommend an excellent sophisticated analytical methodology which is to plug all the information from the EDR/CRD report into a simulation program and work to match each of the measurement points with the simulation program and then you have a much better understanding (and/or check on the simplified technique)

We have used this technique on a lot of EDR/CDR Report data for pre-impact and crash environment for live cases and for research.
Best cases are when we have information from BOTH vehicles...talk about additional pieces of the crash reconstruction puzzle.
Obviously my unbiased opinion (:-) is that the best simulation program out there is msmac3D

The main steps to use msmac3D to accomplish this task is...
  1. Assemble vehicle information
    • loading? make/model/year to check source for vehicle specs (setup loads specs but always double check)
  2. Assemble scene information as in slope/pitch variations of the terrain
    • Which can and will affect steer and braking responses
  3. Digitize the output for the EDR data, first pre-impact(if available) and then the collision EDR (if available)
    • steer, yaw, accel lateral, longitudinal etc so can be read by a spreadsheet program (Excel, etc)
  4. Set up the msmac3D(<-video How To link) simulation and input the steer and braking input tables to same as digitized data
  5. Run the msmac3D simulation
  6. Compare the simulation time history results with the EDR information
    • All variables in msmac3D are output in CSV format so you can easily open (with Excel, etc) and plot the data to compare with EDR/CDR
    • With Excel you simply link to the output file and visually compare the time history charts
  7. Make adjustments to vehicle drag and/or steer to provide a better match
    • The CDR/EDR points are every 0.5, 0.1 or .01 sec increments
      • The simulation is computed every 0.001 sec (and output in any increment!)
    • Matching is a straightforward process
      • Iterate msmac3D to get as good a match as you can
    • Then for the vehicle crash information also do the same
    • Allow vehicles to impact and do the same on comparison of X,Y accelerations, Yaw pitch rates and angles (of available) x,y during collision
    • msmac3D calculates collision forces every millisecond,
Once you get a match of the measured data you have an accurate representation of the pre (and collision) event and an ability to look at the whole picture (with simulation videos etc)
i will post up a sample next week (it's the weekend!)
But relatively straight forward and easy to do.
stay tuned!

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