Abstract: A tuning fork gyroscope design where at least one proof mass is supported above a substrate. At least one drive electrode is also supported above the substrate adjacent the proof mass. Typically, the proof mass and the drive electrode include interleaved electrode fingers. A sense plate or shield electrode on the substrate beneath the proof mass extends completely under the extent of the electrode fingers of proof mass.

Abstract: A force compensated comb drive for a microelectromechanical system includes a MEMS mechanism for providing an output signal representative of a physical quantity; a comb drive for actuating the MEMS mechanism; a comb drive circuit for providing a drive signal to the comb drive for developing a predetermined displacement applied by the comb drive to the MEMS mechanism; an automatic gain control responsive to a change in the force to provide a correction signal to the comb drive circuit to maintain the predetermined motion; and a compensation device responsive to the correction signal for adjusting the output signal of the MEMS mechanism to compensate for errors in the output signal due to a change in the predetermined force.

Abstract: An integrated inertial stellar attitude sensor for an aerospace vehicle includes a star camera system, a gyroscope system, a controller system for synchronously integrating an output of said star camera system and an output of said gyroscope system into a stream of data, and a flight computer responsive to said stream of data for determining from the star camera system output and the gyroscope system output the attitude of the aerospace vehicle.

Abstract: A method for reducing errors in a tuning fork gyroscope includes determining a first distance, gt, between an upper sense plate and a proof mass and a second distance, gb, between a lower sense plate and the proof mass. The method further includes applying a first voltage, Vt, to the upper sense plate and a second voltage, Vb, to the lower sense plate, wherein the ratio of the first voltage and the second voltage is a function of the first distance and the second distance.

Abstract: A compact navigation system for a rover is provided. The navigation system includes a housing configured to be transported by the rover; a gimbal system having two or more gimbals that includes at least an outer gimbal connected to the housing and an inner gimbal nested in and connected to the outer gimbal; a solid state three-axis gyro assembly mounted on the inner gimbal; a solid state three-axis accelerometer assembly mounted on the inner gimbal; a gyro logic circuit responsive to the three-axis gyro assembly for producing an inertial angular rate about each gyro input axis; an accelerometer logic circuit responsive to the three-axis accelerometer assembly for producing a non-gravitational acceleration along each accelerometer input axis; and a processor responsive to the gyro logic circuits and the accelerometer logic circuits for determining the attitude and the position of the housing to provide for long term accuracy of the attitude and the position for navigation of the rover.

Abstract: A tuning fork gyroscope typically including at least one proof mass with an upper sense plate disposed above the proof mass and a lower sense plate disposed below the proof mass and means for sensing changes in the nominal gaps between the sense plate and the proof mass and for outputting a signal indicative of the gyroscope angular rate.

Abstract: An integrated inertial stellar attitude sensor for an aerospace vehicle includes a star camera system, a gyroscope system, a controller system for synchronously integrating an output of said star camera system and an output of said gyroscope system into a stream of data, and a flight computer responsive to said stream of data for determining from the star camera system output and the gyroscope system output the attitude of the aerospace vehicle.

Abstract: A tuning fork gyroscope typically including at least one proof mass with an upper sense plate disposed above the proof mass and a lower sense plate disposed below the proof mass and means for sensing changes in the nominal gaps between the sense plate and the proof mass and for outputting a signal indicative of the gyroscope angular rate.

Abstract: A control system for a tuning fork gyroscope uses motor frequency to control motor amplitude. The tuning fork gyroscope has a drive signal input and an output signal from which motor frequency is determined. A phase/frequency detector generates an error signal by comparing the actual oscillation phase of the output signal with the phase of a reference signal from a crystal controlled frequency synthesizer. The error signal is filtered in a feedback loop control to reduce phase detector ripple. The output of the loop controller is then used to determine the appropriate drive signal to drive the error signal to a constant and maintain a predetermined oscillation frequency.

Abstract: Trenches which reduce or eliminate force and sensitivity associated with proof mass motion normal to the substrate as a result of voltage transients is disclosed. The trenches provide increased separation between interleaved comb electrodes and the substrate, and thereby also reduce the comb lift to drive ratio. The trenches are typically formed directly below the interleaved comb electrodes, but may also be formed below other suspended portions. Trench depth is from 6-10 microns and provides a comb electrode to substrate separation of approximately 8.5-12.5 microns.

Abstract: A micromechanical tuning fork gyroscope having two center electrodes is disclosed. The two center electrodes are excited with bias potentials of opposite polarity. The oppositely biased center electrodes provide electrical symmetry across the gyroscope and thereby reduce charge transients and sensitivity to vertical translation. Currents injected directly into the proof masses are equal and opposite and thus cancel. Motor lift forces acting on the proof masses and interleaved electrodes are equal, and hence the proof masses move in pure translation, thereby reducing in-phase bias. Further, any pure translation normal to the plane of the gyroscope does effect sense axis output signals.

Abstract: Micromachined, thermally insensitive silicon resonators are provided having accuracy equivalent or superior to that of quartz resonators, and are fabricated from a micromechanical, silicon-on-glass process. In one embodiment, such a resonator is realized using a tuning fork gyroscope. Radiation-hard precision voltage references (PVRs) are enabled using the silicon resonators. Thermal sensitivity is reduced relative to that of a silicon-on-silicon process oscillator, providing a thermal sensitivity comparable to that of a quartz oscillator. By employing a micromechanical device based upon a tuning fork gyroscope, resonators are made from either or both of the gyro drive and sense axes. A resonator constructed as an oscillator loop whose resonant frequency is compared to a frequency standard provides a bias voltage as a reference voltage.

Abstract: A tuning fork gyroscope has an in-plane position sensitive pick-off to which an AC or AC+DC bias is applied. Intermodulation is exploited to produce beat-notes between the applied frequency and the motor frequency at amplitudes proportional to motor amplitude, but unaffected by error sources such as spurious substrate charge accumulation. The beat-notes are used to control motor amplitude without the effects of charge accumulation.