I have to simulate a set of DAE's. Therefore I have to reduce the index for this problem:
$ (ms+mb)*\ddot z + mb*ls* \ddot \phi s + mb*lg* \ddot \phi b = -(ms+mb)*g - \lambda2$ $ (mb*ls)*\ddot z + (Js+mb*ls^2)* \ddot \phi s + (mb*ls*lg)* \ddot \phi b = cp*(\phi b - \phi s)-mb*ls*g - hs*\lambda1-rs*\lambda2$
$ (mb*lg)*\ddot z + (mb*ls*lg)* \ddot \phi s + (Jb +mb*lg^2)* \ddot \phi b = cp*(\phi b - \phi s)-mb*lg*g$
$0 = (rs-ro) - h*phi$
$0 = \dot z +rs* \dot \phi s$
m -->mass; J --> intertia; r ---> radius; h --> height; l --> lenght; cp --> spring constant; g -->gravitation constant; $\lambda$ --> constraint forces; $\phi$--> rodation and $z$ -->vertical translation.
Could anyone explain how index-reduction works - would be great.