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Science Forum Index » Nonlinear Science Forum » Double Pendulum Simulation
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Message |
| Guest |
 Posted: Tue Jul 25, 2006 3:26 am |
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Hi
I am trying to numerically integrate the equations of motion
of a double pendulum in 3 dimensions driven by external torques.
They are a set of 4 second-order
differential equations which can be written in vector form as
M(q) q'' + C(q,q') q' + N(q) = F
where M(q) is the mass matrix and F is the vector of (known) input
torques. I
am integrating to obtain q(t)
I tried using different Matlab ode solvers for this problem - ode45,
ode113, ode15s and ode23tb. They all give different results. I am
trying to integrate over 60 secs, sampled at 0.2 sec. The solutions
given by different solvers begin to diverge after 5-10 sec. They are
all set at the same relative tolerance levels.
All solvers give the same solution if there are no external forces
present or if the external forces are very small - of the order of
0.0005 Nm for pendulum masses of 1kg each .
I do not have an analytical form for the solution. So I don't know
which solver to trust - and I am not sure why this is happening. Is
there any particular solver of choice for nonlinear systems of
equations or for the equations of motion of rigid body systems.
I would really appreciate any suggestions/clarifications on this
problem.
Thanks |
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