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      05-26-2010, 12:13 AM   #55
JAJ
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Drives: 2014 Shelby GT500
Join Date: Apr 2008
Location: Vancouver, BC

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Quote:
Originally Posted by JAJ View Post
OK, so it's four months or so later and it's time for an update. I've had a load of fun figuring out how to use accelerometers to measure suspension motion. ...

[1] - After an extensive session of data gathering in early March, I finally have what I think will be usable data from the stock suspension.

...

[2] The next phase is to set the dampers. I don't have a working electronic system yet, so for the moment I'm going to follow the instructions Koni publishes for setting up double-adjustable dampers in their racing catalog.

...

[3] When I have data that allows me to produce a picture of the suspension motion, I'll post it.
First point - are we there yet? Yes, we are.

Second point - see my suspension calibration post from Friday May 21, 2010.

Third point - see my other two posts from tonight, May 25, 2010.

Sensor calibration is the biggest challenge. I've written (Basic) software to compute the timing of two independent but simlar sensor data streams precisely, resample (anti-alias) the datasets to a common timebase, physically calibrate and remove sensor offset at the sensor itself, then again in the post-processing, and finally do the geometry to project the raw 3D data onto a pure vertical axis.

Each stage of integration, after all this care in getting clean data, still requires manual data selection and strictly controlled de-trending to provide useful and believable output.

In the end, rather than measuring the damper or spring motions, I ended up actually measuring the hub as it's driven up-and-down by the tire and seeing how its motion drives through the suspension to move the chassis up and down.