Showing papers on "Ring laser gyroscope published in 2001"

Principles of a three-axis vibrating gyroscope

Abstract: The principal features of a three-axis ring gyroscope are described. The equations of motion, the response to constant rates of turn, and the relationships between the modes of vibration are derived. Tuned and untuned cases are considered.

Dither system for motion sensors

Abstract: A ring laser gyroscope or other motion sensor is dithered at a first rate if a global positioning signal is available and/or when alignment is not being performed, and is dithered at a second rate if a global positioning signal is not available and/or when alignment is being performed. The second rate is greater than the first rate.

Decoupled multi-disk gyroscope

Abstract: A gyroscope system including multiple rotating or oscillating disks filters out disturbance acceleration inputs such as vibrations or jarring while detecting and measuring external angular velocity. The gyroscope disks are decoupled from a substrate to decrease the impact of external vibrations on the gyroscope operation. The gyroscope disks are rotated in opposite directions or oscillated out of phase to decrease the impact of disturbance vibrations and jarring while more accurately measuring external angular velocities applied to the system.

Micro-ring cavity gyroscope with magnetic field lock-in minimization

Abstract: The invention is a compact optical gyroscope (1) based on the Sagnac effect that combines a micro-ring cavity laser (1, 1a, 1b) comprising a magneto-optical material (1b) and a magnetic field (B)to circumvent the lock-in phenomenon at low rates of rotation. The invention also embodies novel processes for breaking lock-in using a transverse Faraday effect.

Ring laser gyro having ring resonator semiconductor lasers and driving method thereof

Abstract: A ring laser gyro includes a tapered portion in a part of an optical waveguide, a plurality of ring resonator semiconductor lasers optically independent of each other on a common plane, and a plurality of electric terminals for detecting a change in the impedances of said ring resonator semiconductor lasers. The tapered portion includes a first portion where a width of the optical waveguide is gradually widened along a direction of propagating a laser beam clockwise and a second portion where the width of the optical waveguide is gradually narrowed along the direction, and further comprising a first ring resonator semiconductor layer in which said first portion is longer than the second portion, and a second ring resonator semiconductor layer in which said second portion is longer than the first portion.

Dither control system for a ring laser gyro

Abstract: A dither control system for a laser gyro having a dither motor for dithering the laser gyro through a desired angular displacement, known as the command angle, in response to a drive signal. In order to help avoid saturation of the laser gyro, the dither control system reduces the command angle by command angle reduction data when the average drive signal applied to the dither motor exceeds a maximum drive value until the command angle reduction data reaches zero. The command angle reduction value is calculated by integrating the difference between the average drive signal and the maximum drive value.

Current control biasing to protect electrode seals

Abstract: Current control biasing of a ring laser gyroscope is employed to protect electrode seals. A frame of a ring laser gyroscope has more than one electrode attached to it. An electric field is created between the electrodes during the operation of the gyroscope, which causes ions in the frame to migrate towards a lowest electrical potential. Electrode seals are located between the electrodes and the frame. By providing a positive power supply voltage and connecting the current control to the non-ground side of the power supply, the mounting structure may be at the lowest electrical potential. The ions will then migrate towards the mounting structure, which significantly reduces migration to the electrodes.

A North-Seeker Based on the Modulation and Output of a Ring Laser Gyroscope

Abstract: A novel north-seeker with laser gyroscope is proposed by means of the characteristics that the ring laser gyroscope has a higher sensitivity for the input of angular speed. A ring laser gyroscope is vertically placed on horizontal constant-speed rotary platform and the input shaft is parallel to the platform plane. The north-seeking procedure can be carried out through measuring the northern component of earth rotational angular speed. The slope error of the platform plane caused by axis installation and system leveling can be measured by an accelerometer placed symmetrically with the north-seeker, thus the data output of the ring laser gyroscope can be compensated. At the same time a method with single-cycle plus multi-position sampling and multi-cycle repeated measuring is applied. In this way the measuring noise of the laser gyroscope is effectively inhibited, the influence of random error and system error is reduced to the maximum limit, the north-seeking accuracy of the system is improved. This system is suitable for the demands in many fields.

Autoregressive analysis for the detection of earthquakes with a ring laser gyroscope

Abstract: The second-order autoregressive AR(2) model is used to analyze rotational data for seismic events captured by a large ring laser gyroscope. Both the Sagnac frequency and linewidth estimates obtained from this model sense the rotational components of seismic waves. An event of magnitude ML = 6.5 at a distance of D = 5.4° from a large ring laser gyroscope operating at its quantum limit is used to compare the AR(2) model with the previous analytical phase angle method of analysis. The frequency, linewidth and analytic phase angle data each satisfactorily estimate the rotation magnitude. The direct detection of rotational motion in the P wave coda is observed, demonstrating the conversion to transverse S wave polarizations by the local geology.

Ring laser and method for driving a ring laser

Abstract: A ring laser of the present invention includes multiple ring resonators with different optical path lengths, wherein at least part of the multiple ring resonators is optically coupled, and a propagating direction of laser light propagating in the ring resonators is not reversed by the coupling.

Systematic calibration for inertial instruments errors in laser gyro strapdown inertial navigation system

Abstract: Presents the Kalman filtering calibration approach developed to calibrate inertial instrument errors in a laser gyro SINS using systematic measurements from the six position test on a fixed base, which includes estimating both laser gyro′s random drift errors and coupled error parameters in SINS system from systematic measurements from fixed based test by Kalman filter and comparing filtering results of two different position test and processing estimates of coupled error parameters and then computing calibration values of other inertial instrument errors and points out that the Kalman filtering calibration approach is simple and the test can be easily implemented using only a manual three axis orientation rotating table at high precision, and the advantages of the Kalman calibration approach being insensitive to both measurement noise and environment disturbance and being of high precision demonstrates both the feasibility and validity of the new calibration approach.

Beat frequencies in a ring laser gyro with its refractive index over unity

Abstract: A frequency shift Δf during rotation in a ring laser gyro with its refractive index of unity was already well known. However, when the refractive index nr is over unity, several expressions for a beat frequency such as 2Δf∝nr, nr0, nr−1, and nr−2 were proposed. In this article, a beat frequency in a uniformly rotating ring laser gyro with nr>1 is calculated using nonrelativistic, special relativistic, and general relativistic theories. To the first order, all the results obtained from these theories show a common beat frequency, which is proportional to the refractive index nr, as far as the dispersion is neglected. When the dispersion is considered, the beat frequency is in proportion to nr0[1−(rΩ/λ0)2(dnr/df)2]−1, where f is a frequency of a laser beam, λ0 is a wavelength of a laser beam when the ring laser stands still, and nr0 is a refractive index at λ0. If nr0=1−(rΩ/λ0)2(dnr/df)2 is satisfied, the beat frequency seems to be independent of the refractive index.

Ring laser gyroscope with offset aperture

Abstract: A ring laser gyroscope (RLG) employs an offset aperture for attenuating undesired modes of laser propagation therein. The RLG includes a block having a ring laser cavity containing a lasing gas, the cavity being substantially in the shape of a polygon having at least three sides and at least three vertices formed by the intersection of sides of the polygonal cavity. At least three mirrors are provided, equal in number to the number of vertices and positioned at the vertices to create a resonant ring laser having a polygonal ring path in the shape of the polygon. An aperture is provided in the ring laser cavity for attenuating undesired modes of laser propagation in the polygonal ring path of the laser. The aperture has an axis that is horizontally offset from a central axis of the polygonal ring path of the laser.

Ring laser gyro with optically independent semiconductor ring lasers

Abstract: A semiconductor ring laser gyro comprising two or more ring lasers, the ring lasers being optically independent of each other, is characterized in that a change in beat frequency with respect to a change in angular velocity of a first ring laser is opposite to that of a second ring laser, and angular velocity of rotation of the gyro is detected by a signal representing a difference between a first beat frequency generated by the first ring laser and a second beat frequency generated by the second ring laser.

High temperature electrode seal in a ring laser gyro

Abstract: A ring laser gyro having a high temperature seal. The ring laser gyro includes a laser block of known construction having a closed loop passage formed within the block in the shape of a polygon. Mirrors positioned at the intersection of each side of the polygon-shaped closed loop passage create an optical closed loop path through passage. A lasing gas is sealed within the closed loop passage, and electrodes mounted to the block and in fluid communication with the passage create at least one laser that traverses the optical closed loop path in the passage. The electrodes are mounted on the laser block with a high temperature seal comprising a washer having a low coefficient of thermal expansion and an optical bond between the washer and the laser block. In a preferred embodiment, the laser block and the washer are formed from the same material to ensure that these structures expand at substantially the same rate when the ring laser gyro is used in a high temperature application.

Guidance system for horizontal drilling

Abstract: The invention relates to horizontal directional drilling systems (14), in particularly guidance systems therefore. Such guidance systems, according to the invention comprise at least one of the sensors: fiber optic gyroscope, ring laser gyroscope (18, 20, 21), micro-electro-mechanical system and rate sensor (25). A microcontroller (9) is present for receiving and processing data from sensors at the drill head. The microcontroller comprises neural fuzzy control logic for processing the data from the sensors at the drill head. Data from the microcontroller (9) are sent to a surface based computer via radio-waves. The user interface in the computer (4) displays azimuth, tilt, and inclination angles of the drill head on the display device. The use of fiber optic gyroscopes and ring laser gyroscopes allows the display of true North and actual and desired tracks on the display device. Means are present for determining a reliability figure for data dependent on integrated signals from rate sensors and such reliability figures are displayed on the display device.

Electrode design to extend sputter life of a ring laser gyroscope

Abstract: A gas discharge tube such as a ring laser gyroscope includes a block. A cathode has an inwardly extending foot that engages the block. Additionally, or alternatively, an insulator is arranged to inhibit shorting between plasma in the block and a flange of the cathode.

Laser gyro with optical fibre ring

Abstract: A gyro designed by laser and optical fibre techniques is disclosed for measuring the angle speed of rotation. An optical gain medium, for example, rare-earth doped optical fibre, and a single-mode optical fibre are used to make two rings, which are overlapped and then matched with a semiconductor laser device to form a ring-shaped optical fibre laser device. A beat frequency is generated between the clockwise and the anticlockwise laser beams from two optical fibre rings and used to measure the angle speed. Its advantages are high accuracy, simple structure and convenient application.

Ring laser gyro

Abstract: A semiconductor ring laser gyro comprising two or more ring lasers, the ring lasers being optically independent of each other, is characterized in that a change in beat frequency with respect to a change in angular velocity of a first ring laser is opposite to that of a second ring laser, and angular velocity of rotation of the gyro is detected by a signal representing a difference between a first beat frequency generated by the first ring laser and a second beat frequency generated by the second ring laser.

Analysis of the Two-Frequency Coning Motion with SDINS

Abstract: The ring laser gyro(RLG) has been used extensively in strapdown inertial navigation system(SDINS) because of the apparent advantages of having wide dynamic range, digital output and high accuracy. The dithered RLG system has dynamic motion at sensor level, caused by the dithering motion to overcome the lock-in threshold. In this case, the attitude error is produced by not only the true coning of the vehicle motion but also the pseudo coning of the sensor motion. This paper describes the definition of the two-frequency coning motion and its noncommutativity error to reject the pseudo coning error produced by the sensor motion such as the dithered RLG. The simulation results are presented to minimize the two-frequency coning error.

Semiconductor laser gyro

Abstract: PROBLEM TO BE SOLVED: To provide a semiconductor laser gyro of a reduced size without sacrificing measurement accuracy. SOLUTION: A multiply encirclement ring resonator 22 constituted by plural encirclement optical paths (waveguide) different in their sizes is formed on a semiconductor substrate 21, a voltage is impressed to a carrier injection electrode 23 provided on the resonator 22 to be laser-oscillated, and a frequency difference between clock-wise and anticlock-wise rotational oscillation modes is found as voltage change from a voltage detecting terminal 24 or a beam multiplexing prism 25 and a photoreceiver 26 so as to measure rotational angular velocity applied from an outside.

System and method for laser cavity length control

Abstract: A system and method for controlling the cavity length of a ring laser gyroscope to properly tune the resonant wavelengths of the ring laser gyroscope during moments when experiencing sudden shocks or high g force accelerations. The system controls the position of a movable mirror in the laser cavity of the gyroscope to control the length of the laser cavity. The system measures the acceleration experienced by the laser cavity, wherein the position of the movable mirror is adjusted to counteract the effects of the acceleration on the movable mirror in a real-time response to the measured acceleration. By adjusting the position of the movable mirror, the resonant wavelengths propagating in the ring laser gyroscope will be maintained at their desired intensity and continue to lase even after experiencing this acceleration. The system may further include a control servo-loop for providing additional cavity length control in order to maintain the desired intensity of the wavelengths propagating within the gyroscope.

Semiconductor device, semiconductor laser, gyro and its operation method

Abstract: PROBLEM TO BE SOLVED: To provide a gyro and its operation method capable of lowering a coupling loss generated when laser light is introduced into a light detector and a noise caused by returning light to a laser from external reflection points. SOLUTION: The gyro has a ring resonance type semiconductor laser where lights circumferentially transmit mutually reversely to each other, terminals detecting beat signal and a ring shape active layer.

Study on dynamic characteristic of a novel silicon micromachined gyroscope

Abstract: A novel silicon micromachined gyroscope were presented The device structure which we called "fence gyro" consists of a proof mass with bars linked up to substrate by suspend springs The dynamic characteristic of the prototype of the novel micromachined gyroscope was analyzed By the means of differential capacitance signal modulated and demodulated, the frequency behaviour of the drive and detection modes of micromachined gyroscope were measured As the proof mass used as the movable electrodes is parallel to the plane of fixed driving and sensing electrodes, there is only slide film damping in the driving and sensing mode The calculated results shown that the gyroscope has the almost same Q factor of the detection mode and drive mode at atmospheric pressure, which is in order of 100 Under the electrostatic excitation in the drive mode, the frequency behaviour of the detection mode was measured The experiment result shows that the drive and sense mode resonant frequencies are 460 Hz and 5496 Hz respectively, and the Q factor of the drive and sense are 1025 and 1065 respectively at atmospheric pressure The experiment result also shows that the micromachined gyroscope exhibits resonance at the resonance frequency of the drive and detection mode without inputting angular rate as mechanical couple

Research on rate-bias system of laser gyro

Abstract: From the view of system, the paper analyzes some special problems of rate bias laser gyro The problems include modulation and demodulation of the output of rate bias triple axis laser gyro, the choice principle of the biased rate, rotating back acceleration of rate bias platform and the rotating back position's effect, etc In addition, through comparing between two plans of navigation, the paper puts forward a plan named ‘navigation project based on rate bias platform’ which is able to increase the accuracy of navigation system or reduce the design demand The article builds a series of basic design criteria of rate bias laser navigation system, providing certain reference for the system design

On the Sagnac Effect in Wave Propagation

Abstract: According to the classical propagation model, the Sagnac effect is due to the movement of receiver during wave propagation. Based on this, we derive the GPS (global positioning system) Sagnac pseudorange correction, the Sagnac effect in interferometry, and the Doppler frequency shift. Then, we examine these formulas with the propagation experiments associated with the Sagnac effect, particularly the reference frame of the receiver velocity and the influences of earth's rotational and orbital motions. Thereby, it is found that the propagation of electromagnetic wave in these experiments is in accord with the classical model with the propagation frame being stationary in an ECI (earth-centered inertial) frame.

Analysis of reflectivity for a beveled corner mirror in semiconductor ring lasers

Abstract: A semiconductor ring laser is expected to be used as a tiny ring laser gyro with low power consumption, which is suitable for mobile systems. However, its corner mirrors may be beveled due to its fabrication processes. Therefore, in this paper, reflectivities of beveled corner mirrors in the semiconductor ring laser are examined. In the analysis here, a guided fundamental mode is expanded into plane waves, and thus vertical confinement of the guided mode is completely incorporated. It is revealed that there is an optimum guiding layer thickness of approximately 0.3 /spl mu/m to minimize mirror losses in the beveled mirrors. Also, facet reflectivities of equilateral n-polygon shaped ring lasers with beveled mirrors are studied, and it is found that a large n leads to a low threshold current.

Ring laser gyroscope

Abstract: Ring laser gyroscope semiconductor structures and methods for making such structures are provided. The integrated structure includes a substrate (1200) on which a beam splitter region (1220), a waveguide (1290), a photodetector (1295), and preferably a laser (1298) are provided. An integrated circuit (1299) for processing data generated by the photodetector can also be included. By detecting the fringe pattern with an array of photosensitive elements, the data can be fit to a mathematical model of the interference pattern. The fit is then used to determine one or more rotational parameters.