Showing papers on "Gyroscope published in 1992"

Micromechanical tuning fork angular rate sensor.

Abstract: A, micromechanical tuning fork gyroscope is fabricated from a unitary silicon substrate utilizing etch stop diffusions and selective anisotropic etching. A silicon structure is suspended over the selectively etched pit. The silicon structure includes at least first and second vibratable structures. Each vibratable structure is energizable to vibrate laterally along an axis normal to the rotation sensitive axis. The lateral vibration of the first and second vibratable structures effects simultaneous vertical movement of at least a portion of the silicon structure upon the occurrence of angular rotation of the gyroscope about the rotation sensitive axis. The vertical movement of the silicon structure is sensed, and a voltage proportional to the movement is generated, for providing an indication of angular rate of rotation detected by the gyroscope.

Comparison of hemispherical resonator gyro and optical gyros

Abstract: The basic design of the small hemispherical resonator gyro inertial and tactical grade sensors and associated electronics is described. To reduce the cost of the electronics and maintain part per million accuracy, emphasis has been placed on digital control and processing techniques. A comparison of the ring laser gyro, fiber optic gyro, and hemispherical resonator gyro sensors shows that the latter offer lower cost, smaller size, and higher reliability than their optical counterparts. >

Electrostatically controlled micromechanical gyroscope

Abstract: An integrated electrostatically-controlled micromechanical gyroscope with a rotor encompassed within a rotor cavity and electrostatically spun within the cavity. The gyroscope includes a plurality of axial electrostatic rotor actuators above and below the rotor for controlling the axial and tilt position of the rotor within the cavity, and a plurality of radial electrostatic actuators spaced circumferentially around the rotor for controlling the radial and tilt position of the rotor within the cavity. The position of the rotor within the cavity is then resolved to determine the external forces acting on the rotor.

Fault-tolerant inertial navigation system

Abstract: Disclosed herein is a Fault-Tolerant Inertial Navigation System comprising, in a preferred embodiment, a Redundant Set of at least two Inertial Navigation Systems, from which one may identify and isolate at least one instrument within an Inertial Navigation Unit which shows substantial performance degradation. The two inertial navigation units are fully capable of performing navigational functions. Each of these inertial navigation units has a plurality of navigational instruments, including at least three linear sensors (such as accelerometers) and three angular change sensors (such as gyroscopes or ring laser gyroscopes). No two linear sensors nor any two angular change sensors of either unit are aligned colinearly. Each of the inertial navigation units produces a set of independent navigational solutions at each of their respective outputs. The independent navigational solutions of each of the navigation units are compared and any significantly degraded performance of any one linear sensor or any one angular change sensor is detected.

Principles of superfluid-helium gyroscopes.

Abstract: In this paper we describe how quantum coherence of superfluid helium provides a mechanism by which very small rotations can substantially modify the flow in a toroidal container. The specific modifications to that flow are discussed. For $^{4}\mathrm{He}$, we explain how the rotationally induced flow can be detected by monitoring the apparent phase-slip critical current. The rotational resolution is limited by stochastic processes related to the nucleation of phase slips. This type of superfluid-helium gyroscope (SHEG) is an analog of the rf superconducting quantum interference device (SQUID). We also show how the large coherence length of $^{3}\mathrm{He}$ can be utilized to lead to a rotationally induced interference pattern. Changes in this pattern can permit the detection of very small rotational motion. This type of SHEG is analogous to the dc SQUID. In appendixes, electrical circuits equivalent to the SHEG are described, as are certain constraints on rotational sensitivity imposed by external measuring devices.

Disturbance torque compensated three axis yaw control system

Abstract: A satellite attitude control system is usable in the absence of any inertial yaw attitude reference, such as a gyroscope, and in the absence of a pitch bias momentum. Both the roll-yaw rigid body dynamics and the roll-yaw orbit kinematics are modelled. Pitch and roll attitude control are conventional. The model receives inputs from a roll sensor, and roll and yaw torques from reaction wheel monitors. The model produces estimated yaw which controls the spacecraft yaw attitude. The model further produces estimates of the constant component of the disturbance torques for compensation thereof.

Low noise fiber gyroscope system which includes excess noise subtraction

Abstract: A system and method for subtracting excess noise from a high sensitivity gyroscope system in which a laser diode array is focused into an Nd-doped active fiber. A resultant gyro signal is polarized, detected, and amplified. A noise signal is polarized, delayed, detected, and amplified such that the noise signal is polarized parallel to the gyro signal and delayed by a fiber delay, of a length equal to a length of a gyroscope fiber coil. The excess noise component in the amplified gyro signal is reduced by modulating the amplified noise signal with a portion of the amplified gyro signal and subtracting the amplitude-modulated noise signal from the amplified gyro signal to produce a reduced noise gyro signal.

Two-mode optical fiber accelerometer.

Abstract: A novel interferometric accelerometer is described and demonstrated by using a two-mode, elliptical-core optical fiber. A loop of fiber bends when subjected to acceleration normal to its plane, which causes a differential phase shift between the LP01 and LP11 modes. This optical phase shift is directly measured at the output of a phase-sensitive detector by using an in-fiber double-frequency conversion technique. Preliminary results indicate a scale factor of 2 rad/g, with a sensitivity and bias stability of 30 mg. Signal-processing electronics employed to measure the rotation rate in a fiber gyroscope could potentially be used to reduce short-term noise to the 1–10-μg range. Cross talk between the sensitive axis and one of the transverse axes is virtually null.

Acoustic noise reduction in the MK 49 ship's inertial navigation system (SINS)

Abstract: Sperry Marine has devised a passive structure-borne noise isolation system that reduces the noise generated by dithered ring laser gyroscopes to levels below the requirements of MIL-STD-740-2. Descriptions of some of the analytical and experimental processes required to develop this system are presented, together with structure-borne noise test results. Results show that a 47-dB structure-borne noise reduction has been achieved with a noise isolation system that is compatible with the stability and repeatability required by navigation systems. The noise reduction techniques presented have enabled Sperry Marine to develop a dithered ring laser gyroscope navigator feasible for naval applications, the MK 49. >

Fiber-optic gyroscope

Abstract: A fibre-optic gyroscope is provided herein for measuring an angular velocity of a fibre coil by propagating light beams clockwise and counterclockwise in a specified fibre coil, by detecting an intensity of an interference beam, and calculating a phase difference between a clockwise propagated beam and a counterclockwise propagated beam. The fibre-optic gyroscope includes a light source for emitting a quasi-monochromatic light beam. A photodetector is provided for detecting an intensity of the interference beam. A defined plurality of fibre paths are interconnected in a specific defined manner, with a polarizer, a first depolarizer and a second depolarizer as well as a first coupler and a second coupler being provided in specified fibre paths. The depolarizers are constructed by coupling a polarization-maintaining fibre to the front end and/or the rear end of the polarizer at a 45° inclin-ation angle between principal axes of the polarizer and the polarization-maintaining fibre. The polarization-maintaining fibre has a difference of optical paths between the quasi-monochromatic beam and the interference beam with different principal axes being longer than a coherent length of the light source.

Sensor coil for low bias fiber optic gyroscope

Abstract: A sensor coil for a fiber optic gyroscope. The coil is formed on a spool of carbon composite material or of another material whose coefficient of thermal expansion approximates that of the overlying windings of the glass optical fiber. The windings are potted in an adhesive material. Various bias effects are addressed by the coil design. The close matching of the thermal expansion characteristics of the spool and the fiber windings as well as proper selection of the coil potting material minimize the Shupe-like bias caused by thermal stress that would be otherwise exerted by a standard metallic spool. By careful selection of potting material (particularly its modulus of elasticity) vibration-induced bias, coil cracking, degradation of h-parameter and temperature-ramp bias sensitivity are also minimized.

Piezoelectric-ceramic cylinder vibratory gyroscope

Abstract: This paper presents a piezoelectric-ceramic vibratory gyroscope with a new structure. The vibrator of this vibratory gyroscope consists of a piezoelectric-ceramic circular cylinder and no adhesion process is necessary. On its outer cylindrical surface, six elongated electrodes are formed in parallel with each other along the central axis. These electrodes are used both for poling treatment and AC excitation as well as detection. Adjustment of resonant frequencies between each of the three terminals by trimming helps eliminate any compensations of circuit constants, so that simple circuitry can be obtained. Because of its small size and simple structure, this vibratory gyroscope is expected to be used in the shake sensor for cameras and hand-held video cameras.

Quartz resonant gyroscope or quartz resonant tuning fork gyroscope

Abstract: A resonantly vibrating or tuning fork rate sensor in which a quartz beam is instrumented with electrodes in first and second regions forming respective sense and drive electrodes wherein the piezoelectric resonance affect of the quartz material between the drive electrodes is used as a tuning element for an oscillator circuit. The electrodes are driven in a balanced voltage mode and sensed in a common mode rejection differential amplifier while leads running to the electrodes along the quartz beam are placed at positions of minimal field strength for improving the signal to noise ratio of the device. The rate sensor utilizes a multi-electrode pattern in order to make such lead placement possible. The sense pattern and drive pattern may be either in one orientation with the drive electrodes proximate to the body of the quartz resonator or in a second pattern with the sense electrodes proximate to the body. Both the drive electrodes and the sense electrodes operate on the piezoelectric principal, utilizing constriction to induce vibration from the drive electrodes and sensing the current generated from piezoelectric effect resulting from the vibrational compression which occurs out of the plane of vibration during inertial rate input. Alternatively, a capacitive electrode structure may be utilized as a pick-off.

1.06 μm All-fiber Gyroscope With Noise Subtraction

Abstract: There is great interest in using fiber superfluorescent sources in fiber gyroscopes as a replacement for semiconductor superluminescent diodes (SLD's). Potential benefits include higher available power, better wavelength stability with temperature, and improved lifetime. Multicore Nd:fibers1 pumped by a laser diode array offer high output powers in a single mode core, but are susceptible to lasing due to feedback2. This type of diode laser pumped source has been successfully employed in a fiber gyroscope using a backward pumping scheme to avoid feedback3. We report a fiber gyro using a similar source, but are able to forward pump it with the use of an optical isolator. The gyro utilizes all spliced fiber components after the source fiber. Excess noise4,5 has been an issue with fiber broadband sources due to their somewhat narrower (compared to SLD's) emission spectrum. We demonstrate an intensity noise subtraction scheme which is successful in removing most of the excess noise.

Estimation and control of the attitude of a dynamic mobile robot using internal sensors

Abstract: For the control of a dynamic mobile robot, the attitude in gravity space is an important state of the robot Usually, the attitude is difficult to detect by simply using the signals from sensors For example, an external sensor contacting the ground suffers disturbances from the roughness of the ground; the integration of a gyroscope signal has the problem of drift; an inclination sensor does not indicate the direction of gravity when acceleration exists To solve these problems, we propose a control method in which the attitude of a mobile robot is estimated by an observer considering the robot dynamics and using only the information obtained by internal sensors We applied this method to a wheeled inverted pendulum as an example of a dynamic mobile robot The estimation of the attitude was made with good accuracy using the signals from the rate gyroscope and the motor encoder, and the control of stable running of the pendulum on a flat level plane worked successfully We also realized the running contro

Single-channel phase-tracker for the open-loop fiber optic gyroscope

Abstract: A simplified analog signal processing technique for the open loop fiber optic gyroscope is described which is base on the same electronic closed-loop 'phase-shift nulling' concept reported in a previous paper . The system provides a linear output from an open ioop gyro configuration over a2ic radian range in Sagnac phase shift with good linearity and relatively low noise and drift. 1. INTRODUCTION Much of the research effort on fiber optic gyros in recent years has been directed towards thedevelopment of closed loop Sagnac phase shift detection approaches [1,2]. Typically, theseapproaches involve the use of complex, high speed electronic signal processing schemes and integrated optic components to allow a precise non-reciprocal phase shift to be introduced into theSagnac interferometer to counterbalance the rotation-induced Sagnac phase shift. These systems aregenerally aimed at high precision, low drift and wide dynamic range sensing applications, such as in- ertial navigational systems. There is, however, also considerable interest in gyros for use in less-

Integrated optic gyro with one Bragg transducer

Abstract: A laser gyroscope is provided that utilizes a single frequency shifter (34c) in the form of a Bragg cell, to adjust the frequencies of counter-rotating optical signals in a thin film waveguide (20) to achieve resonance along the optical path encountered by each of the signals. The system also utilizes two voltage to frequency convertors (30, 32), each of which outputs an RF signal to a respective frequency shifter. Each voltage to frequency convertor is modulated by a modulation signal that includes a DC component and an RF signal. The single frequency shifter approach results in fewer required components for proper operation of the thin film laser gyroscope. Redundant back-up components can be added to the gyroscope to guard against the event of a component failure. Alternately, the laser gyroscope is inherently more tolerable of low fabrication yield because of the redundancies.

Distribution, stability, bifurcations and catastrophe of steady rotation of a symmetric heavy gyroscope with viscous- liquid-filled cavity

Abstract: The number, the angles of orientation and the stability in Rumyantsev-Movchan's sense of oblique steady rotations of a symmetric heavy gyroscope with a cavity completely filled with a uniform viscous liquid, possessing a fixed point O on its symmetric axis, are given for various values of the parameters. By taking the square of the upright component of the angular momentum M2 as a control parameter, three types of bifurcation diagrams of the steady rotations, two types of jumps and two kinds of local catastrophes, one being the symmetric reduced cusp type and the other being of the symmetric reduced butterfly type, are obtained. By taking account of the M2-damping owing to the moment of unavoidable faint friction, two different modes for the gyroscope, initially in a stable quasi-steady upright rotation with a nutation angle θ3 equal to zero, to topple over are found.

Fiber-optic gyroscope for measuring velocity of an object

Abstract: A fiber-optic gyroscope having a single mode fiber coil for sensing the rotation suffers from drift or fluctuation of scale factor of the output signals owing to spontaneous rotation of polarization of beams propagated in the fiber coil. Thus, two depolarizers are required in front of and at the back of the polarizer to avoid the fluctuation. The depolarizer of prior art consists of two birefringent materials twistedly connected with each other at an about 45° inclination angle between the principal axes of one and the principal axes of the other. A conventional fiber-type depolarizer has two polarization maintaining fibers connected together. A new, simplified depolarizer is proposed. The depolarizer is built by gluing a polarization maintaining fiber to an end of the polarizer with an about 45° inclination angle between the principal axes of the fiber and the principal axes of the polarizer. The depolarizer allows us to dispense with one polarization maintaining fiber and spare the operation for connecting fibers by once.

Comparison of wideband inertial line-of-sight stabilization reference mechanizations

Abstract: One subsystem critical to the performance of a precision electro-optical line-of-sight (LOS) pointing system is a wide-band inertial stabilization reference. This paper compares, in terms of relative performance of LOS stabilization in the presence of vehicle jitter, three inertial LOS stabilization reference mechanizations for space-based optical systems. The three mechanizations are: an inertially stabilized platform, the Inertial Pseudo-Star Reference Unit (IPSRU) under development at Draper Laboratory; a device called the Optical Reference Gyro (ORG), also developed at Draper Laboratory; and a strapdown wide-band inertial sensor assembly. Each of the three stabilization reference mechanizations generates a collimated alignment beam that is injected into the entrance aperture of the optical system. In the stabilized platform mechanization, the alignment beam emanates from a platform inertially stabilized from vehicle jitter in two axes, and thus the alignment beam becomes a jitter- stabilized pseudo-star. An alignment loop closed around the pseudo-star image and a steering mirror in the optical path stabilizes the LOS against vehicle jitter. The ORG alignment beam projects from the gyro rotor, which is decoupled from case motion and is effectively inertially stabilized. The ORG spin-speed noise is compensated with phase-lock technology. In the strapdown mechanization, the alignment beam source is hard-mounted to the vehicle. Inertial measurement of the local vehicle motion is fed forward, open loop, to a steering mirror in the optical path to compensate for alignment beam jitter.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Test results of Honeywell's first-generation high-performance interferometric fiber optic gyroscope

Abstract: Honeywell's first-generation, high-performance interferometric fiber-optic gyroscope (IFOG) was tested along with sensor electronics over a limited static and dynamic temperature environment. This serrodyne closed-loop IFOG consisting of polarization-maintaining fiber components and a LiNbO3 phase modulator has simultaneously achieved inertial-grade requirements for bias stability, bias repeatability, bias temperature sensitivity, bias temperature-rate sensitivity, random noise, and scale-factor error over the tested temperature range.

On the interesting behavior of a gimbal-mounted gyroscope

Abstract: The behavior of a gyroscope mounted in frictionless gimbal bearings when the outer ring is constrained to rotate at a constant rate is examined. The resulting motion of the rotor axis is described, accounted for by an elementary argument followed by a more complete treatment. The behavior of the rotor in an unusual parameter regime is also discussed. The equations of motion for a motor‐driven rotor are obtained and compared with the frictionless case.

Ambulance with position stabilised stretcher support platform - that is continuously adjusted by motors responding to gyroscope coupled sensors to maintain horizontal position

Abstract: The hospital ambulance has a stretcher support (12) that is mounted on a platform that can be continuously adjusted in X and Y axes to maintain a level surface as the vehicle passes over undulations and along inclined surfaces. The platform has a pair of coupled electric motors built into a central unit (23), with end motor relating to a single axis. The commands for the motors are based upon absolute angular measurements (E) that are obtained by sensors responding to frame movements relative to a stable gyroscope. The spinning gyroscope inertia remains in a constant position and provides a stable point of reference. ADVANTAGE - Allows ambulance stretcher support to remain horizontal.

Gravity vector estimation from integrated GPS/strapdown IMU data

Abstract: The Air Force is planning to launch a helium-filled balloon possessing a payload of an inertial ring laser gyro strapdown system and a 3-antenna, minimum 12-channel, dual-frequency GPS receiver. A ground-fixed, single-antenna GPS receiver will be centrally placed beneath the balloon’s trajectory, allowing for differential mode GPS tracking. The inertial measurement unit’s (IMU’s) accelerometers will measure the total kinematic accelerations in the body frame. These will be transformed to local (n,e,d) navigation frame components using the integrated attitude of the balloon obtained from the IMU’s gyroscopes. GPS-determined accelerations will reflect total inertial accelerations, which can easily be expressed in the navigation frame. Differencing the two sets will thus yield the desired gravitational accelerations. An elaborate covariance study was conducted involving a 36-state, 43-noise-process open-loop Kalman filter. Using conservative initial IMU and GPS error source values, the covariance study suggests that estimation of all three components of balloon-borne gravity vectors to an accuracy of 5 mGa1 (1 mGa1 = 10~5 m/s2) is feasible using “within reach” electronic and engineering capabilities. Leveling uncertainties are the main contributors to the overall gravity vector estimation error budget.

Measuring arrangement useful for controlling the attitude of a three-axis stabilized satellite, corresponding evaluation process, regulating system and process

Abstract: A measurement arrangement is useful for controlling the attitude of a three-axis stabilized satellite equipped with sun-sensors for determining the orientation of the sun (sun vector) with respect to a satellite-fixed coordinate system, as well as with speed gyroscopes for detecting components of the satellite speed of rotation vector φ. It is necessary that the measurement range of the sun-sensors cover the round angle in a preselectable plane (for example XY plane) and perpendicularly thereto a limited angular range of maximum ±α2max on both sides of the plane. In a ddition, only an integrating speed gyroscope carrying out measurements in a single measurement axis that encloses with the plane an angle of at least (π/2) - α2max should be provided. Also disclosed are an evaluation process for determining the satellite speed of rotation, as well as the satellite deviation with respect to a direction of reference, a regulating system for carrying out attitude control maneuvers using the measurement arrangement and the evaluation process, and a corresponding regulating process.

A solid state vibrational gyroscope

Abstract: A solid state vibrational gyroscope comprises a resonator bell 21 having piezoelectric drive transducers 1a and 1b aligned with antinodes of a natural mode of vibration of the resonator bell. This is achieved by either constructing the resonator bell such that it is deliberately out of balance so that the antinodes are aligned with the transducers 1a, 1b, or alternatively by balancing the resonator bell such that the antinodes of the natural mode of vibrations always corresponds to the position of the drive transducer regardless of its location. The invention further provides for balancing the fully assembled resonator bell using the drivers 1a, 1b and sensors 2a, and 2b in the balancing process.

Determining inertial errors from navigation-in-place data

Abstract: To validate the self-calibration performance of a missile system's inertial navigation system (INS), an inertial error estimator (IEE) and a calibration procedure were developed and tested. The IEE was developed using a least squares fit of navigation-in-place data to calculate the accelerometer biases, the gyroscope biases, and the axis misalignments. It was found that the estimation error due to highly correlated regression functions decreases with navigation time. A tradeoff study was performed to select the optimum navigation-in-place time allowed for determining the estimation of the inertial errors. Once the optimum navigation time was determined, an INS calibration procedure incorporating the IEE was developed. The calibration procedure was validated by applying corrections for the inertial errors to the INS, and then navigating in place to show a reduced position error profile. Test results showing the outcome of the INS calibration procedure are included. >

Performance Improvement of a Dynamically Tuned Gyroscope Using an Input Compensator

Abstract: An improved rebalance loop of a dynamically tuned gyroscope that has annexed an input compensator to the conventional rebalance loop is proposed in this paper. The input compensator is a simple estimator of input rates to the gyro, which is to be subtracted from torquing command. The improved rebalance loop significantly reduces transient torquing error, which allows higher gain and wider bandwidth loop as well as smaller tilt angle over transient state. Thus, it contributes to the accuracy improvement and widening dynamic range of the gyroscope. It is also shown that the stability robustness of the rebalance loop combined with the input compensator can be recovered by adjusting the bandwidth of the input compensator. Closed-loop frequency response analysis shows an improvement of the rebalance loop with the use of the input compensator, compared with a conventional one, in that the ratio between input and output torque has unity magnitude as well as low phase shift in wider range. The improved rebalance loop has been fabricated with analog devices and connected to a real gyroscope. The experiment result is compared with that of simulation. Both of them have demonstrated that the responses of output torque and rotor's tilt angle are considerably improved.

Vibration Damping Mechanisms with Gyroscopic Moment

Abstract: Damping mechanisms based on gyroscopic moments are studied and their characteristics are compared with conventional mechanisms. A generalized form of Schlick's gyroscope is theoretically analyzed, and an optimal design method is derived. The stabilizing effect is compared with the rotational dynamic vibration absorber. It turns out that the effect of the passive gyroscopic stabilizer depends on the rotating speed of the gyroscope; thus the stabilizer has no essential limitation by the inertial moment such as there is with the rotational dynamic vibration absorber. The gimbal movement of the CMG (control moment gyroscope) is directly controlled with an actuator, thus it can be used as a fully active vibration control mechanism. The single-gimbal CMG is compared with the RW (reaction wheel) with respect to the damping efficiency for impulsive disturbances. Experiments with a single-gimbal CMG for a Pendulum are carried out and the results prove the efficiency.

Sagnac-type optical fiber gyroscope having depolarizers of differing lengths

Abstract: A sagnac-type fiber optic gyroscope in which depolarizers are connected to both ends of the fiber coil and are then connected with the outputs of a 3×3 directional coupler.