Apparatus and method for determining the rate of rotation of a moving body

• US 5,189,913 A
• Filed: 10/17/1991
• Issued: 03/02/1993
• Est. Priority Date: 03/14/1989
• Status: Expired due to Fees

• Current Assignee: Rafael - Armament Development Authority Ltd.
• Original Assignee: State of Israel--Ministry of Defence Armament Development Authority Rafael
• Inventors: Netzer, Ehud, Porat, Itzhak
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US07/778,255
• Time in Patent Office: 502 Days
• Field of Search: 73/505, 73/518
• US Class Current: 73/504.08
• CPC Class Codes: G01C 19/5642 using vibrating bars or beams

Abstract

An apparatus and method for determining the rate of rotation of a body rotating with an angular velocity ω about a first axis. The apparatus comprises a housing adapted to be fixed to the body so as to rotate with the angular velocity ω about the first axis and a mechanical system within the housing having more than two degrees of freedom. Electromagnetic drive coils are provided for applying a forced vibration to the mechanical system about a second axis substantially perpendicular to the first axis, thereby producing a Coriolis response along a third axis mutually perpendicular to the first and second axes, the forced vibration having a predetermined magnitude and a frequency which is constrained to lie within a predetermined range such that there is produced a coupling between the degrees of freedom whereby the magnitude of the Coriolis response is substantially insensitive to frequency. The magnitude of the Coriolis response is measured and a computing device responsive to the magnitude of the forced vibration and to the magnitude of the Coriolis response calculates the rate of rotation ω. In a preferred embodiment, the mechanical system has four degrees of freedom and comprises an inertial beam having a couple of concentrated masses or an inertial mass element coupled thereto.

Claims

1. An apparatus for determining the rate of rotation of a body rotating with an angular velocity ω

about a first axis, the apparatus comprising;

a housing adapted to be fixed to said body so as to rotate with said angular velocity ω

about the first axis;

a mechanical system within the housing having more than two degrees of freedom;

forcing means for applying a forced vibration to the mechanical system about a second axis substantially perpendicular to said first axis, thereby producing a Coriolis response along a third axis mutually perpendicular to said first and second axes, said forced vibration having a predetermined magnitude and a frequency which is constrained to lie within a predetermined range such that there is produced a coupling between said degrees of freedom whereby the magnitude of the Coriolis response is substantially insensitive to frequency;

measuring means for measuring the magnitude of the Coriolis response; and

computing means responsive to the magnitude of the forced vibration and to the magnitude of the Coriolis response for calculating the rate of rotation ω

.

2. The apparatus according to claim 1, wherein the mechanical system comprises:

a first beam having known moments of inertia about said second and third axes and fixed at one end thereof to said housing,

a first concentrated mass element coupled to a second end of said first beam and to a first end of a second beam having known moments of inertia about said second and third axes,

a second concentrated mass element coupled to a second end of the second beam, and

damping means coupled to at least one of said first and second concentrated mass elements.

3. The apparatus according to claim 1, wherein the mechanical system comprises:

a beam having known moments of inertia about said second and third axes and fixed at one end thereof to said housing,

an inertial mass element having known moments of inertia about said first, second and third axes and two linear and two angular degrees of freedom in mutually perpendicular planes, said mass element being coupled to the beam so as to introduce an axial displacement between an elastic center of the beam and a center of gravity of the mechanical system, thereby producing dynamic coupling between the linear and angular degrees of freedom of the inertial mass element whereby the magnitude of the Coriolis response is substantially insensitive to said frequency; and

damping means coupled to the inertial mass element.

4. A method for determining the rate of rotation of a body rotating with an angular velocity ω

about a first axis, the method comprising the steps of;

rotating a mechanical system having more than two degrees of freedom about said first axis at said angular velocity ω

,

applying a forced vibration to said mechanical system about a second axis substantially perpendicular to the first axis, said forced vibration having a magnitude and a frequency which is constrained to lie within a predetermined range such that there is produced a coupling between said degrees of freedom so as to produce a Coriolis response along a third axis mutually perpendicular to said first and second axes whose magnitude is substantially insensitive to said frequency,

measuring the magnitude of the Coriolis response, and

computing the rate of rotation ω

as a function of the magnitude of the forced vibration and of the magnitude of the Coriolis response.