The invention relates to a mechanical structure which provides motion in six degrees of freedom, which comprises: (a) a main plate; (b) a base; (c) at least three supporting structures, each comprising a lower, bridge-like section supported by the base, and an upper section connected to said bridge section and to said main plate, wherein: (I) said bridge-like structure comprising two supporting plates, two intermediate plates, and one middle plate, all being serially connected one to another by means of four transversal hinges; (II) each pair of said supporting plates being slidable in linear displacement parallel to the base; (III) said upper section comprising two plates, a lower plate connected to said middle plate by means of a hinge transversal to said lower plate but longitudinal with respect to said middle plate, and an upper plate connected to said lower plate by means of a longitudinal hinge and to said main plate by means of a transversal hinge; (d) At least six linear motors connected each to a corresponding supporting plate, for applying a force thereon in order to effect a linear displacement of said plate; and (e) control means for determining the linear displacement of each linear motor.