Apparatus for measuring rotation rates with acoustic waves
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorHerbert J. Shaw
Life of this patent
Estimating the term…
Abstract
A measuring apparatus for determining the rotational velocity of a solid erical or cylindrical object by propagating an acoustic wave through the object. The inward face of the surface of the object is used to reflect the wave, thereby causing it to make multiple transits through the object. Multiple transits provide a large time factor which allows the apparatus to achieve a high degree of sensitivity in measuring small rate changes and low rotation rates.
Claims8
An apparatus for measuring the rotation rate of a spherical object of an isotropic material about axes passing through its center comprising:
- a. means for exciting an acoustic wave at a first point on the surface of said object;
- b. means for sensing the arrival of said acoustic wave on the surface of said object at a second point diametrically opposite to said exciting means, said exciting means and said sensing means being spaced apart from said object;
- c. means for measuring the transit time required for said acoustic wave excited at said first point to propagate through said object to said second point;
- and
- d. means for computing said rotation rate as a function of said transit time according to the formula
- .theta. = (2/T) cos.sup.-1 (vT/d)
- where .theta. is said rotation rate, T is said transit time, v is the acoustic velocity of propagation of said acoustic wave through said object, and d is the diameter of said object.
An apparatus for measuring the rotation rate of a spherical object of an isotropic material about axes passing through its center comprising:
- a. means for exciting an acoustic wave at a first point on the surface of said object;
- b. means for sensing the arrival of said acoustic wave on the surface of said object at a second point fixed relative to said exciting means, said exciting means and sensing means being spaced apart from said object;
- c. means for measuring the transit time required for said acoustic wave excited at said first point to propagate through said object ot said second point;
- d. means for computing said rotation rate as a function of said transit time;
- and
- a fluid surrounding said object, the acoustic impedance of said isotropic material being sufficiently greater than the acoustic impedance of said fluid to enable said acoustic wave to be inwardly reflected upon its impingement upon the inner surface of said object such that said acoustic wave is multiply reflected within said object such that said rotation rate of said object as computed by said computing means is a function of the transit time required by said acoustic wave to propagate through said object N times.
Dependencies are inferred from the claim text.