Acceleration Severity Index
Acceleration Severity Index
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The ASI value is calculated from 3 acceleration time histories using the following fomula; |
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| Where : | ax,ay,az |
are the X,Y,Z accelerations of the vehicle:
- for the 1998 calculation (BS EN 1317-1:1998) they are averaged over a 50ms moving interval. - for the 2010 calculation (BS EN 1317-1:2010) they are passed through a four-pole phaseless Butterworth filter with a 13Hz cut-off frequency. |
| xl,yl,zl | are acceleration limits xl = 12g yl = 9g zl = 10g. | |
The acceleration input curves should be in units of g. If the input curves are in any other unit a conversion factor can be input to convert back to g.
When selecting input curves it is assumed that the X curve is numerically the first curve (the one with the lowest id) of the ones selected and the Z curve is the last. If they are in a different order then the acceleration limits can be modified to reflect the different order. For more information on ASI see BS EN 1317-1.
NOTE: For the BS EN 1317-1:2010 calculation T/His assumes the curves have been filtered through a Class 180 filter and padded with +/-0.5seconds of data as per the specification.