Hi All,
To convert acceleration to displacement for
impact of a projectile, I am trying to perform a double integration of
the signal. The acceleration data is acquired as a 1D array at 20 kHz,
with the Integral X(t) used to obtain the displacement. To validate the
results of this, I used Excel to fit a 6th degree polynomial to the
acceleration data, and mathematically integrated the polynomical
equation twice to get the displacement (integration constants found
from initial condiditons: at t=0, v = 3.63; x = 0. I am confident that
this Excel calculation is correct as the velocity profile matched the
approach and rebound velocities of the projectile (as measured
independently by high speed footage).
To replicate this
in LV (for future automated calculation, Excel method is
time-intensive), I used the Integral x(t) function twice. However
wiring the value of 3.63 to the initial condition input of the first
instance of Integral x(t) did not produce the expected results as
calculated by Excel, with the first integration starting at 0 rather
than 3.63. By trail and error, a value of ~440000 wired to the initial
condition produced similar results as Excel, although I can't figure
out the relationship between 3.63 and 440000.
I realise
that I can replicate the Excel work by fitting a polynomial in LV and
integrating this equation, however I wish to integrate the actual data
rather than the polynomial approximation. I know that this is possible,
and I think it's either due to some manipulation of 3.63 to get 4400000
(is it something to do with the equation in Integral x(t) help menu y[i] = (1/6) sum(x[j-1] + 4x[j] + x[j+1])?) or else due to the inappropriate use of Integral x(t).
Can someone help me with this, if possible explaining how to arrive the value of 440000 from 3.63. Thanks.
Fiachra
Message Edited by FiachraC on 10-30-2009 11:06 AM
