In this note, a new procedure for inverting nonlinear systems is propo
sed, which presents some computational advantages when applied to flex
ible robot arms or. more generally, to mechanical structures. This pro
cedure will be presented in a general setting, for nonlinear time-vary
ing systems. An iterative algorithm is proposed which computes a smoot
h controlled invariant time-varying manifold whose mathematical proper
ties are illustrated and exploited. An application to a flexible two-l
ink manipulator illustrates the given algorithm and its computational
advantages.