Showing papers on "Ring laser gyroscope published in 2011"

Measuring Gravito-magnetic Effects by Multi Ring-Laser Gyroscope

Abstract: SUMMARY We propose an under-ground experiment to detect the general relativistic effects due to the curvature of space-time around the Earth (de Sitter effect) and to rotation of the planet (dragging of the inertial frames or Lense-Thirring effect). It is based on the comparison between the IERS value of the Earth rotation vector and corresponding measurements obtained by a tri-axial laser detector of rotation. The proposed detector consists of six large ring-lasers arranged along three orthogonal axes. In about two years of data taking, the 1% sensitivity required for the measurement of the Lense-Thirring drag can be reached with square rings of 6 $m$ side, assuming a shot noise limited sensitivity ($ 20 prad/s/\sqrt{Hz}$). The multi-gyros system, composed of rings whose planes are perpendicular to one or the other of three orthogonal axes, can be built in several ways. Here, we consider cubic and octahedron structures. The symmetries of the proposed configurations provide mathematical relations that can be used to study the stability of the scale factors, the relative orientations or the ring-laser planes, very important to get rid of systematics in long-term measurements, which are required in order to determine the relativistic effects.

How to detect the Chandler and the annual wobble of the Earth with a large ring laser gyroscope.

Abstract: We demonstrate a $16\text{ }\text{ }{\mathrm{m}}^{2}$ helium-neon ring laser gyroscope with sufficient sensitivity and stability to directly detect the Chandler wobble of the rotating Earth. The successful detection of both the Chandler and the annual wobble is verified by comparing the time series of the ring laser measurements against the ``C04 series'' of Earth rotation data from the International Earth Rotation and Reference System Service.

Foucault pendulum on a chip: angle measuring silicon MEMS gyroscope

Abstract: We report detailed characterization of a vacuum sealed angle measuring silicon MEMS gyroscope The new gyroscope utilizes completely symmetric, dynamically balanced quadruple mass architecture, which provides a unique combination of maximized quality (Q) factors and isotropy of both the resonant frequency and the damping The vacuum sealed SOI prototype with a 2 kHz operational frequency demonstrated virtually identical X- and Y-mode Q-factors of 11 million Due to the stiffness and damping symmetry, and very low dissipation, the gyroscope can be instrumented for direct angle measurements with fundamentally unlimited rotation range and bandwidth Experimental characterization of the mode-matched gyroscope operated in whole-angle mode confirmed linear response in excess of ±450 °/s range and 100 Hz bandwidth (limited by the setup), eliminating both bandwidth and range constraints of conventional MEMS rate gyroscopes

Design, analysis and experiment of a novel ring vibratory gyroscope

Abstract: This work presents the design, analysis, simulation and experiment of a novel ring vibratory gyroscope based on piezoelectric effect. The gyroscope has a simple millimeter-scale resonator which comprises of a metallic structure and eight piezoelectric elements. The piezoelectric elements attached to the metallic structure excite the primary mode of the resonator, sense the second mode caused by Coriolis force and output signal proportional to input angular velocity. A theoretical analysis on the proposed gyroscope is performed using the AMM method and DM method for the forced vibration solution of active mode and sense mode with the inclusion of the Coriolis force coupling. The sensitivity of the gyroscope and its dependence on some geometry parameters are obtained. The working principle is validated by using FEM simulation. The metallic structure of the prototypal gyroscope was machined by precision turning and electrical charge technologies, as a result, the adherence process of the piezoelectric elements is simplified and the positioning precision is improved, which ensures the high axial symmetry of the resonator. A prototypal gyroscope is selected for practical experiments. The natural frequencies of active mode and sense mode of the prototype are close, the frequency split is 0.06 Hz, and the quality factor is approximately 5000 in atmosphere. Therefore, the gyroscope can work properly without a vacuum package. A control circuit was specially designed to activate the resonator and readout the angular velocity signal. The performance of the gyroscope is characterized on a precision rate table. The experimentally obtained scale factor is 65.5 mV/°/s, the nonlinearity is 1323 ppm in range of ±150°/s, the angle random walk is about 0.05°/h1/2, and the zero-bias instability is about 1.5°/h at room temperature. There is a good linear relation between the sensing voltage and the angular velocity, suggesting that the novel ring vibratory gyroscope is a good candidate for low and medium rotation speed measurements.

A mode-matched 0.9 MHZ single proof-mass dual-axis gyroscope

Abstract: This paper reports on the design, fabrication, and characterization of a high-frequency single proof-mass dual-axis gyroscope. The hollow-disk pitch-and-roll resonant gyroscope has electrostatically tunable in-plane and out-of-plane resonance modes to enable mode-matched operation at ∼ 0.9MHz in the presence of process non-idealities such as thickness variations of the SOI wafer. A prototype device demonstrates x- and yaxis rate sensitivity of 127µV/deg/sec and 214µV/deg/sec, respectively. High quality factors (Q) of ∼ 10,000 are observed in vacuum for the in-plane drive and out-of-plane sense resonance modes. The device is implemented using a revised version of the HARPSS™ process, thereby enabling a single-chip tri-axial implementation when integrated with a yaw disk gyroscope.

A 1.82 m^2 ring laser gyroscope for nano-rotational motion sensing

Abstract: We present a fully active-controlled He-Ne ring laser gyroscope, operating in square cavity 1.35 m in side. The apparatus is designed to provide a very low mechanical and thermal drift of the ring cavity geometry and is conceived to be operative in two different orientations of the laser plane, in order to detect rotations around the vertical or the horizontal direction. Since June 2010 the system is active inside the Virgo interferometer central area with the aim of performing high sensitivity measurements of environmental rotational noise. So far, continuous not attempted operation of the gyroscope has been longer than 30 days. The main characteristics of the laser, the active remote-controlled stabilization systems and the data acquisition techniques are presented. An off-line data processing, supported by a simple model of the sensor, is shown to improve the effective long term stability. A rotational sensitivity at the level of ten nanoradiants per squareroot of Hz below 1 Hz, very close to the required specification for the improvement of the Virgo suspension control system, is demonstrated for the configuration where the laser plane is horizontal.

Chirped area coupled resonator optical waveguide gyroscope

Abstract: We study the transmission of an optical field through a rotating coupled resonator optical waveguide (CROW) in which the size of the ring resonators changes from one ring to the next. We focus on symmetric integer wavelength chirps of the circumference of the rings relative to the central ring in the array. The transfer matrix method is used to obtain the transmission as a function of the inertial rotation rate Ω resulting from the Sagnac effect. Chirping increases the slope of the oscillations in the transmission as a function of Ω, which can be exploited to further enhance the rotation sensitivity beyond that of a CROW with uniform resonators.

Rotation Sensitivity of Gyroscopes Based on Distributed-Coupling Loop Resonators

Abstract: This paper reports a theoretical study of a recently proposed coupled-resonator optical waveguide (CROW) gyroscope consisting of a Sagnac interferometer in which light is coupled between adjacent loops in the coil. Simulations show that after optimization, this gyroscope is less sensitive to rotation than a conventional resonant fiber-optic gyroscope (RFOG) made of a single loop. Instead, the sensitivity decreases as the number of loops is increased. The fundamental reason is that in both types of sensors, the sensitivity is proportional to the group delay, and the maximum achievable group delay is limited in the same manner by loss. In addition, this CROW gyroscope utilizes multiple resonators instead of one, so it is much harder to stabilize against external perturbations. The RFOG still stands as the ideal candidate for a compact resonant gyroscope.

Theoretical description and design of a fast-light enhanced helium-neon ring-laser gyroscope

Abstract: We describe an enhanced rotation sensor involving an active helium-neon (HeNe) ring laser coupled to a passive enhancement resonator, which has been named a fast-light-enhanced HeNe ring-laser gyroscope (RLG). Theoretical rotation sensitivity enhancements as large as two orders of magnitude are presented. The physical effect responsible for the increased rotational sensitivity is the anomalous dispersion of the enhancement resonator, which produces a larger beat frequency as compared to a standard HeNe ring-laser gyroscope (RLG) as the laser cavity is rotated. We present the layout of the fast-light enhanced HeNe RLG, and we provide the theoretical modeling of the enhanced rotational sensitivity. A design is presented for the red HeNe (632.8 nm). The beat frequency is calculated with respect to rotation rate, which defines the useful range of operation for this highly sensitive RLG. Considerations for practical issues including laser-mirror reflectivity precision, unsaturated laser gain, and cavity-length stability are discussed.

Positioning device and method of coal mining machine in full-mechanized mining face

Abstract: The invention provides a positioning device and method of a coal mining machine in a full-mechanized mining face, and belongs to an autonomous positioning device and method of the coal mining machine. The positioning device of the coal mining machine is installed in a machine body, and comprises a rubber vibration damping base, a triaxial laser gyroscope, a triaxial optical fiber accelerometer, a positioning device microprocessing unit, and a positioning device anti-explosion shell , wherein the positioning device anti-explosion shell is connected above the rubber vibration damping base, and the triaxial laser gyroscope, the triaxial optical fiber accelerometer and the positioning device microprocessing unit are installed in a shell consisting of the rubber vibration damping base and the positioning device anti-explosion shell. Real-time acceleration values in three directions are measured by using the triaxial optical fiber accelerometer, and real-time angular velocities in the three directions are measured by using the triaxial laser gyroscope; thus, data of a sensor is sampled to a DSP (Digital Signal Processor) to determine the initial velocity and position, and the displacement and angular deflection of the coal mining machine along the three directions are obtained through an integral operation. The positioning device has the advantages of compact structure, simple method, safety, reliability and simplicity and convenience for installation and operation.

Laser gyro temperature compensation and control device and application

Abstract: The invention discloses a laser gyro temperature compensation and control device and an application. The device comprises a laser gyro cavity, a metal shell, a temperature control device, a self-adaptive temperature control circuit and a temperature sensor. The device is characterized in that the temperature sensor and the temperature control device are put on the laser gyro cavity or the metal shell. The invention also relates to the application of the temperature control device in laser gyro temperature compensation. The invention overcomes the overproof quasi-zero of laser gyro temperature, has obvious self-adaptive temperature compensation effect, solves the problems of project applications when a laser gyro is in bad working environments such as high temperature, low temperature, suddenly changed temperature, and the like and has the advantages of compact and reliable structure, stable working performance, simple operation, and the like.

Sagnac interferometer with adaptive nonlinear detection

Abstract: We present a Sagnac interferometer that uses a nonlinear adaptive medium for detection. The nonlinearity of the medium being characterized by a finite response time, the detection has a finite frequency bandwidth determining two operational regimes: at low variation rate of the rotation speed the interferometer operates in the slow-light regime, providing a direct measurement of the angular acceleration. For high variation rate of the rotation speed the amplitude of the alternating component of the Sagnac phase shift is instead detected, with the continuous and low-frequency components filtered out by the adaptive nonlinear process in the medium.

Application of the vector modulation method to the north finder capability gyroscope as a directional sensor

Abstract: This paper presents the application of the vector modulation method (VMM) to an open-loop interferometric fiber optic gyroscope, called the north finder capability gyroscope (NFCG), designed and assembled in TUBITAK UME (National Metrology Institute of Turkey). The method contains a secondary modulation/demodulation circuit with an AD630 chip, depending on the periodic variation of the orientation of the sensing coil sensitive surface vector with respect to geographic north at a laboratory latitude and collection of dc voltage at the secondary demodulation circuit output in the time domain. The resultant dc voltage proportional to the first-kind Bessel function based on Sagnac phase shift for the first order is obtained as a result of vector modulation together with the Earth's rotation. A new model function is developed and introduced to evaluate the angular errors of the NFCG with VMM in finding geographic north.

Control device for working point of four-frequency laser gyro

Abstract: The invention discloses a control device for a working point of a four-frequency laser gyro. The device comprises a reflector position servo loop, an automatic modulation amplitude control loop and an automatic gain control loop, and coupling is absent among the three loops. The three control loops simultaneously work, the four-frequency laser gyro stably works at any working point, such as a working point with the lowest magnetic sensitivity or temperature sensitivity. Therefore, the anti-jamming capability of the four-frequency laser gyro is improved.

Ultimate-performance fiber-optic gyroscope: A reality

Abstract: The fiber-optic gyroscope started to be investigated in the mid-70s with the advent of optical-fiber communications. Today, it reaches ultimate theoretical performance and surpasses its well-established competitor, the ring laser gyroscope.

Small jitter frequency stabilization method of four-frequency laser gyro

Abstract: When a four-frequency laser gyro adopts light intensity difference for frequency stabilization, accuracy thereof is easily influenced by parameter variation in light combination, photoelectric conversion and amplification processes. The invention discloses a novel frequency stabilization mode, small jitter modulation is carried out on path length of the four-frequency laser gyro, and then frequency stabilization is carried out according to the modulation condition of four-frequency laser gyro intracavity travelling wave mode amplitude, so that the four-frequency laser gyro operates under the condition that homonymous travelling wave mode beat-wave amplitude is maximum. The invention can solve problems which are caused when light intensity difference is adopted for frequency stabilization, and performance of four-frequency laser gyro is improved while the four-frequency laser gyro operates in unique uninterrupted state.

Research on lock-in correction for mechanical dithered ring laser gyro

Abstract: Although a sinusoidal bias method is introduced to avoid working in the death band for a majority of time, the mechanical dithered ring laser gyro (RLG) still encounters information loss when crossing the zero rate point. A novel lock-in error correction method is proposed which can pick up the lost information and remove the random walk error radically. The lost information at the zero rate crossing can be expressed by such parameters as the phase and phase acceleration of a beat frequency signal. These parameters are sampled every time the phase crosses the zero rate point, and two correction trains are formed. Using the minimum variance method, the correction trains are properly scaled to compensate the output of RLG. Experiment shows that even in a bad working condition, this method can achieve satisfactory results.

Model of lock-in in a ring laser and a semiconductor laser gyro

Abstract: It is assumed that the process of lock-in in a ring laser has a finite transient time. This assumption serves as a basis for developing a semiconductor laser gyro. A semiconductor optical amplifier is applied as an amplifying medium, and a ring resonator represents a long optical fiber. The injection of an external single-frequency light into a ring resonator with subsequent circulation of counterpropagating waves is used. The light characteristics of the semiconductor laser gyro are discussed, and the rotation sensitivity of the gyro is demonstrated.

Piezo adjuster for compensating the thermal variations of the optical path length of the cavity of a laser gyroscope

Abstract: This paper discusses the possibility of creating a piezo adjuster with passive thermal compensation elements to be used as part of a ring laser gyroscope to counteract thermal variations of the optical path length of the cavity. The dependence of the linear thermal expansion coefficient of glass–ceramic CO-115M is investigated. The paper presents the temperature dependences of the variation of the cavity perimeter when ideal and actual piezo adjusters are used. It is shown that passive thermal compensation can be achieved by varying the geometrical parameters of the piezoelectric actuator’s structural elements that have various values of the linear thermal expansion coefficient.

All-fiber interferometric fiber optic gyroscope for inhibiting zero drift

Abstract: A method for inhibiting zero drift of an all-fiber interferometric fiber optic gyroscope and a corresponding all-fiber interferometric fiber optic gyroscope are disclosed. The method comprises: reversing the polarity of an AC voltage applied to a PZT piezoelectric ceramic phase modulator according to a predetermined half-cycle time period, and making half of the difference between output rotation rates of the gyroscope in two adjacent half-cycle time periods as the output rotation rate of the gyroscope in a cycle. A phase reversal switch and a DSP chip are added to the all-fiber interferometric fiber optic gyroscope. The phase reversal switch is used for controlling the polarity of the AC voltage, and the DSP chip is used for outputting a square wave signal to control the phase reversal switch and for calculating the output rotation rate of the gyroscope according to the output signal of a demodulation/amplifier circuit.

Four-frequency laser gyro control method

Abstract: The invention discloses a four-frequency laser gyro control system The system realizes the control over a path length and a magnetic field according to variation characteristics of difference frequency information output by a four-frequency laser gyro per se along with the path length and the magnetic field to ensure that the four-frequency laser gyro works under a condition that a zero offset of the four-frequency laser gyro has minimum sensitivity to the variation of the magnetic field or a cavity length, and thus, the performance of the four-frequency gyro is improved

Near shot-noise limited performance of an open loop laser-driven interferometric fiber optic gyroscope

Abstract: We report for the first time experimental evidence of near shot-noise limited performance for an open loop interferometric fiber optic gyroscope interrogated with a narrowband laser instead of a broadband source. Using a highly coherent laser source (uf = 2.2 kHz), the measured gyroscope noise is 350 nrad/Hz for an average returning power of 20 μW, while the measured noise for the same gyro operated with a broadband source (uλ ≈ 30 nm) was 850 nrad/√Hz. This measured noise is only ~2 dB above the calculated shot noise for this power. This result was made possible by using a very narrow linewidth, which greatly reduces the laser phase noise and thus the phase-noise-mitigated coherent backscattering. This excellent noise performance has applications for future fiber gyroscope technologies as well as other sensors utilizing a Sagnac interferometer. The bias drift of the laser-driven gyroscope was higher than anticipated but could be reduced to roughly Earth-rate using a frequency sweeping technique. In addition to improved sensitivity, the benefits of using a laser include much higher scale factor stability, lower power consumption, and lower component cost.

Laser gyro north finder

Abstract: The utility model discloses a laser gyro north finder, which comprises a support seat, a rotating shaft vertically arranged in the support seat, and a rotating turret fixed on the rotating shaft, wherein upper and lower ends of the rotating shaft are rotationally connected with the support seat through a bearing; a detecting system, a rotation system and a positioning system are arranged on the rotating shaft and the rotating turret; the detecting system comprises a bracket arranged on the rotating shaft through a shock absorber; a transversally arranged accelerometer, a vertically arranged accelerometer and a laser gyroscope are arranged on the bracket; and the positioning system is used for positioning the rotating turret after the rotating turret is rotated to four measuring positions. The laser gyro north finder provided by the utility model has the advantages of reliable measurement, compact dimension, convenience in installation and maintenance, low cost, and the like.

Four-frequency laser gyro electronic reading system

Abstract: The invention discloses a four-frequency laser gyro signal reading method based on electronic signal processing. In the method, the separation of beat-frequency signals of two single gyros is finished by electronic signal processing instead of optical signal processing, so that beams output by a four-frequency differential laser gyro can be mixed together by means of only one simple prism, and the sensitive angular velocity of the four-frequency laser gyro can be extracted from the mixed beams by using the electronic signal processing algorithm. The simplified beam-combining assembly has the advantages of less attenuation of optical signals, simple structure and higher firmness and is easy to assemble.

All-Fiber Mode-Locked Ring Laser With a Sagnac Filter

Abstract: We present an ytterbium-doped all-fiber all-normal-dispersion laser with a Sagnac filter. The Sagnac filter facilitates the all-fiber configuration without bulk filtering components. In addition, the bandwidth, central wavelength, and modulation depth can be tuned easily by controlling the length of the polarization-maintaining (PM) fiber and polarization controllers in the Sagnac loop. All these properties are independent of the polarization state of the pulses. Stable mode-locked pulses are obtained in this laser with a pulse energy of 3.5 nJ.

Instantaneous phase method for readout signal processing of body dithered ring laser gyro

Abstract: The readout signal of a body dithered ring laser gyro contains both useful information and the dither component. The dither component must be removed to get the useful information. The dither stripping method can get the useful information without latency. But the quadrature demodulator only has 1/4 pulse resolution, which means that the quantization noise will limit the short-term accuracy. The effect and the property of quantization noise are analyzed in detail. Taking advantage of high-speed analog-to-digital conversion (ADC), the analog values of the two beat frequency signals in quadrature are sampled. A novel instantaneous phase method is introduced, which can get the residual phase besides 4× resolution and the quantization noise can be removed radically. The Allan variance analysis of experimental results shows that the quantization noise coefficient using this method is only 1/7 of that using the original 4× resolution method.