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Message ID: 3418     Entry time: Fri Aug 13 01:53:12 2010
Author: Gopal 
Type: Update 
Category: Optic Stacks 
Subject: Gravity Implementation Confirmed 

Time Domain Analysis on a Driven, Damped Simple Pendulum has produced a method for implementing gravity.

COMSOL made this simple task a cryptic one: the following methods had previously failed:

  • Previous Frequency Domain testing lead to unwanted oscillations of all loads.
  • Prescribed accelerations at first seemed to create a constant gravity, but instead incorrectly constrained net acceleration to the inputted amount


1) An (approximately) impulse displacement was applied in the horizontal direction. The pendulum bob's displacement was observed for varying pendulum lengths.

2) The drive and response displacements vs. time were FFT'd to produce transfer functions.

3) The fundamental frequencies were inverted, squared, and plotted against frequency.

4) Since the graph is linear with an R^2 of over 0.99, it is reasonable to assume that gravity is properly acting as a restoration force.


Attachment 1: Pendulum_Length.png  27 kB  Uploaded Fri Aug 13 02:55:27 2010  | Hide | Hide all
Attachment 2: Pendulum_Length.png  27 kB  Uploaded Fri Aug 13 02:55:27 2010  | Hide | Hide all
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