Patent ID: 7900512
Filing Date: 2011-03-08
Classification: G01C

Abstract:
1. An angular rate sensor, of which operations are in a three-dimensional coordinate system consisting of x, y, and z-orthogonal directions, based on a first and a second elastic acoustic wave propagating along the x and y-directions, respectively, in an elastic material on which a Coriolis force acts in response to a rotary motion of the angular rate sensor about the x-direction, comprising: a supporting member having a surface extending on an x-y plane created by the x and y directions, respectively, in the coordinate system, and having a surface portion at least including the surface of the supporting member for serving as the elastic material; a plurality of perturbation masses disposed over the supporting member within a predetermined region of the surface of the supporting member and arranged with a periodicity of one half of a wavelength of the first elastic acoustic wave so as to vibrate in a z-direction being perpendicular to the x-y plane; a film disposed over the surface of the supporting member so as to enclose the predetermined area on which the plurality of the perturbation masses are formed, the film having an upper and a lower surface which are parallel to the x-y plane and being made of piezoelectric material; a driving transducer disposed over the film for driving the first elastic acoustic wave caused along the x-direction, the first elastic acoustic wave having a predetermined wavelength in the elastic material including the film made of the piezoelectric material and the surface of the supporting member, wherein the plurality of the perturbation masses vibrate in the z-direction coherently with the first elastic wave, the driving transducer being in alignment with the predetermined area along the x-direction on the x-y plane so that the plurality of the perturbation masses are displaced by the Coriolis force for generating the second elastic acoustic wave along the y-direction in the elastic material; and a detecting transducer disposed over the upper surface of the film and arranged such that the predetermined area is adjacent to the detecting transducer and is in alignment along the y-direction on the x-y plane, for detecting the second elastic acoustic wave, and for providing an output indicative of the second elastic acoustic wave generated by the Coriolis force as a function of an angular rate of the rotary motion of the angular rate sensor itself.