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Vehicle suspension characterization

  1. Apr 15, 2010 #1
    Hi,

    I have a motor home that rocks quite a bit when entering driveways, speed bumps, etc. I've added some mods like Koni shocks & struts, rear http://www.timbren.com/" rubber springs, but was never able to quantify the improvements. Well times have changed! I got a hold of a M52223 processor demo board (with 8 12-bit adc) and purchased a MMA7260 accelerometer to take suspension measurements.

    P1060736.jpg

    I got it setup so that the processor measures the x (side to side), y (front to back) and z (up/down) axis voltages every 5 ms. The accelerometer scale factor is 800 mV/g.

    My latest project was to add a larger rear sway bar (SB). The old one is 33 mm and new is 36.5 mm diameter.

    I ran several tests. I first pushed against the side of the motor home to get it rocking. The data showed little difference between the two SB. Should the SB help against side rocking???

    My second test is to go over a speed bump at an angle. Though there are differences, they don't seem dramatic.

    KM2Ot.jpg
    KM2Offt.jpg
    Old SB

    KM6Nt.jpg
    KM6Nfft.jpg
    New SB

    The time axis in the graphs is in units of 5ms. The mark "200" = 1 second
    The second graph is a FFT of the data.

    Over all there isn't as much improvement as I expected. The shock damping also doesn't look that great.

    Here's my main question. Given the data, how does one determine the damping coefficient?

    Do you guys see anything special in these graphs? Peak to peak side movement of one g-force seems fairly high, doesn't it? Dishes fly out of the cabinet if not locked!

    Thanks for helping me understand the data.

    Navion
     
    Last edited by a moderator: Apr 25, 2017
  2. jcsd
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