Re: Spreadsheet Analysis of Rotating Stick

[brian whatcott <inet@INTELLISYS.NET>]

At 10:58 11/27/99 -0500, Bob Carlson wrote:
> ///
> I proceeded numerically and then tested the solution in a spreadsheet.
> Calculations are shown below where t is time, q is theta, w is omega, and a
> is alpha (for lack of Greek symbols).  The spreadsheet follows this analysis.
>
> t   q   w   a
> --------------------------
> 0   qo  wo  ao
> t   q1  w1  a1
> 2t  q2  w2  a2
> 3t  q3  w3  a3
> 4t  q4  w4  a4
> .   .   .   .
> .   .   .   .
>
> Using finite element differentiation:
>
> w1 = (q2-qo)/2t
> w2 = (q3-q1)/2t
> w3 = (q4-q2)/2t
>
> a2 = (w3-w1)/2t
> a2 = (q4-2q2+qo)/4t^2
....
> Bob Carlson

I have a stray comment: what works, works.

 But in system simulation one is advised to start with the highest
difference and accumulate a sum over successive time slice values
 (rather than starting with the lowest difference and subtracting
successive values to find higher differences.)
 The former method minimizes noise contributions, the latter approach
produces increasingly erratic differences.

Here Bob seems to be subtracting a current value for velocity
from its previous value to represent acceleration.  This would
presumably be noisy if experimentally derived values were inserted?


brian whatcott <inet@intellisys.net>
Altus OK