Re: Solving a complicated moving geometry problem ?

[Juan Pablo Carbajal]

So it seems the ball is following a trajectory that does not depend on
the cylinder.
Hence just turn around the question: given the trajectory of the ball
(that you can solve using an ODE) where can I place a cylinder (with
your constraints) such that its surface is tangential to the
trajectory?
Another easy approach is to conde the crossing of the cylinder surface
by the ball, and the tangential condition as event functions, and add
that to your ODE solver, then search the initial conditions that
trigger the events.
Check 
https://octave.org/doc/interpreter/Matlab_002dcompatible-solvers.html#Matlab_002dcompatible-solvers
to learn how to use events.