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      06-18-2008, 09:29 AM   #31
lucid
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Drives: E30 M3; Expedition
Join Date: Apr 2007
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Quote:
Originally Posted by swamp2 View Post
Yes the EDC system is probably "aware of" the spring constant, but the system is going to be robust to changes in spring rate, damping and ride height, virtually guaranteed.
Quote:
Originally Posted by jm1234 View Post
Perhaps I should be more clear, I think it is fair and valid to conclude that the "system is going to be robust to changes in spring rate" (it is actually guaranteed because even stock spring have some variability) but you do so without attempting to put bounds on the statement.
A specific spring rate is most likely not hardcoded in the control algorithm. Moreover, there might not even be an algorithm, but merely a lookup table of some kind that matches measured acceleration data to predetermined damper settings. That might explain the “robustness” of the system althought an algorithm can be robust as well, but will be more precise by definition. However, I would refrain from making educated guesses on how robust the system is exactly. Any such educated guess would have to have solid technical justification to avoid constituting a mere hypothesis or lead to trial and error engineering.

Having said that, the funny thing is, even BMW must be using a good deal of trial and error engineering when sorting out the suspension systems (hence the thousands of hours spent testing the car on the ring, etc). The range of inputs and behaviors are too complex to model comprehensively. I saw a documentary on one of the F1 teams trying to work through suspension issues they were having. They crunched numbers endlessly and could not explain the telemetry data. Then they hired a suspension “guru”, flew him to site, and the guy poured over the data for a couple of days and finally figured out what was wrong, but he was working from the data and not the model. Well, I guess one can argue that they had a crappy model...
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