This article presents a procedure for improving the transient response of a boundarycontrolled non-linear flexible elastic beam through a feed-forward action. It is shown that it is possible to obtain a formal analytic solution of an infinite-dimensional linear system, which approximates the non-linear dynamics, under time-varying boundary conditions in terms of the free vibration modes of the structure, whose calculation is a relatively easy task. The feed-forward action is then obtained by inverting the relationship between input and output variables. A numerical example is presented and some simulation results are discussed.