  Suspended resonant optical cavities are basic building blocks for several
experimental devices. An important issue is the control strategy required to
bring them in the resonant or slightly detuned configuration needed for their
operation, the so-called \textit{ locking} procedure. This can be obtained with
a feedback strategy, but the error signal needed is tipically available only
when the cavity is near the resonance with a precision of the order $\Delta
L\simeq\lambda_{\ell}{\cal F}^{-1}$, where ${\cal F}$ is the cavity finesse and
$\lambda_{\ell}$ is the laser's wavelength. When the mirrors are freely
swinging the locking can be attempted only in the short time windows when this
condition is verifyed. Tipically this means that the procedure must be repeated
several times, and that large forces must be applied. In this paper we describe
a different strategy, which tries to take advantage by the fact that the
dynamics of the mirrors is known at least in an approximate way. We argue that
the locking procedure considered can be more efficient compared with the naive
one, with a reduced needed maximal feedback. Finally we discuss possible
generalizations and we point to future investigations.
