Fully balanced micro-machined inertial sensor
View Patent ↗The improvement includes an outer proof mass having a corresponding center of mass; and an inner proof mass having a corresponding center of mass, where the corresponding centers of mass of the outer proof mass and the inner proof mass are approximately co-located. Thus, a double Foucault pendulum is essentially provided in a micromachined gyroscope.
1. A vibratory structure gyroscope comprising: an outer proof mass having a corresponding center of mass; an inner proof mass having a corresponding center of mass, where the corresponding centers of mass of the outer proof mass and the inner proof mass are approximately co-located; a plurality of electrodes coupled to the inner and outer proof masses; and a plurality of shuttles coupled to the inner and outer proof masses, where the outer proof mass and the inner proof mass are vibrated along a first axis of translational motion and sense Coriolis forces along a second axis of the translational motion in the presence of an angular velocity around a third axis, wherein the first axis and the second axis are in-plane and the third axis is out-of-plane; and wherein the plurality of shuttles are configured to permit vibrational movements of the inner and outer proof masses along the first axis and prevents vibrational movement of the inner and outer proof masses in any other direction.
2. The vibratory structure gyroscope of claim 1 , where the inner proof mass is nested within the outer proof mass.
3. The vibratory structure gyroscope of claim 1 , where the inner proof mass is in the shape of a rectangular prism and the outer proof mass is in the shape of a frame; where the inner proof mass is in the shape of a disk and outer mass is in the shape of a ring; where both the inner proof mass and the outer proof mass are in the shape of a frame; where both the inner and outer proof masses are in the shape of rings; or where the inner and outer proof masses are in the shape of multiple concentric rings coupled to each other through spokes.
4. The vibratory structure gyroscope of claim 1 , further comprising: actuators which vibrate the inner and outer proof masses in anti-phase translational motion; or actuators which vibrate the inner and outer proof masses in a higher order Wineglass or Lame mode.
5. The vibratory structure gyroscope of claim 1 , further comprising actuators which vibrate the inner and outer proof masses in synchronicity.
6. The vibratory structure gyroscope of claim 5 , further comprising a flexural connection between inner and outer proof masses and where the synchronization of the vibratory motion is accomplished by the flexural connection between the inner and outer proof masses.
7. The vibratory structure gyroscope of claim 6 , further comprising means for utilizing a closed loop algorithm acting on the inner and outer proof masses to synchronize the vibratory motion.
8. The vibratory structure gyroscope of claim 1 , further comprising: means for vibrating the inner and outer proof masses in an anti-phase linear vibratory motion with approximately equal inertial forces, such that a net force generated due to the vibratory motion is approximately zero; means for vibrating the inner and outer proof masses in an in-phase linear vibratory motion such that a net force generated due to the vibratory motion is non-zero; means for vibrating the inner and outer proof masses in an anti-phase torsional vibratory motion with approximately equal rotational inertia, such that a net torque generated due to the vibratory motion is approximately zero; means for vibrating the inner and outer proof masses in an in-phase torsional vibratory motion such that a net torque generated due to the vibratory motion is non-zero; means for sensing a linear motion of the inner and outer proof masses along x, y or z axis to measure angular velocity of the gyroscope along the x, y or z axis; means for sensing a linear motion along x, y or z axis to measure a linear acceleration of the gyroscope along the x, y or z axis; means for sensing a torsional motion along x, y or z axis of the inner and outer proof masses to measure an angular velocity of the gyroscope along the x, y or z axis; or means for sensing a torsional motion along x, y, z axis to generate a timing reference signal.
9. The vibratory structure gyroscope of claim 1 , where the gyroscope is anchored to the inner proof mass; where the gyroscope is anchored to the outer proof mass; or where the gyroscope is anchored to both the inner and outer proof masses.
10. The vibratory structure gyroscope of claim 1 , further comprising: parallel plate electrodes located on the inner and outer proof masses, which parallel plate electrodes are used to drive and sense a vibratory motion of the inner and outer proof masses through electrostatic transduction; or comb finger electrodes located on the inner and outer proof masses, which comb finger electrodes are used to drive and sense a vibratory motion through electrostatic transduction.
11. The vibratory structure gyroscope of claim 1 , further comprising a pressure membrane and a mechanical element coupled to the pressure membrane to measure pressure in addition to inertial forces.
12. The vibratory structure gyroscope of claim 11 , further comprising a source of current coupled to the mechanical element making the mechanical element sensitive to magnetic fields, changing vibration amplitude, phase or frequency of the inner and outer proof masses in the presence of magnetic fields.