Acoustic gyrometer

#The present invention relates to an acoustic gyrometer comprising a cavity filled with a fluid, means for exciting a first acoustic resonance mode of said cavity, and means for measuring at least a second acoustic resonance mode of said cavity, induced by Coriolis forces when the cavity is subjected to at least one rotation to be measured, said rotation occuring around an axis of rotation.

#Such a gyrometer, mounted on a moving body, makes it possible to measure the rotational speeds of this moving body around one or several reference axes.

#A gyrometer of the type defined above has already been introduced and is described in the French Pat. No. 2 554 225. In this patent, the cavity has the form of a right-angled parallelepiped and is disposed so that two of its faces parallel to each other are perpendicular to the axis of the rotation to be measured. The first resonance mode, namely the mode excited by the excitation means, is a mode in which the particulate acoustic velocities are all parallel and orthogonal to the axis of rotation. The second resonance mode, namely the one induced by Coriolis forces, is of the same type, i.e. whose particulate acoustic velocities are all parallel, but the direction of the velocities of the induced mode is orthogonal to the direction of the velocities of the excitation mode. In order that such a gyrometer functions with good performance, it is important that a certain number of conditions be satisfied. These conditions are more especially the following:

#This invention shall be better understood by referring to the following description of the preferred embodiment of the gyrometer of the invention, as well as to the annexed drawings in which:

#FIG. 1 shows a perspective view of the cavity of the gyrometer of the invention,

#FIG. 2 shows a cutaway view of the cavity in the xOy plane of FIG. 1,

#By referring to FIG. 1, an acoustic gyrometer for measuring the speed of rotation 2 around an axis Ox is now described.

#The gyrometer includes a cavity 1 which here is a standard flattened ellipsoid of revolution, namely obtained by the rotation of an ellipse 10 around its small axis.

#As shown in FIG. 2, which is a cutaway view of the cavity 1 in the xOy plane, O being the center of the ellipse and Oy an axis perpendicular at O to the axis Ox of the rotation 2 to be measured, the small axis of ellipse 10 extends along axis Ox and its length is H, whilst the large axis of ellipse 10 extends along axis Oy in FIG. 2, and has a length of D.