Showing papers on "Ring laser gyroscope published in 2000"

Rotation sensing with a dual atom-interferometer Sagnac gyroscope

Abstract: We reports improvements to our Sagnac effect matter-wave interferometer gyroscope. This device now has a short-term rotation-rate sensitivity of 6×10−10 rad s−1 over 1 s of integration, which is the best publicly reported value to date. Stimulated Raman transitions are used to coherently manipulate atoms from counterpropagating thermal beams, forming two interferometers with opposite rotation phase shifts, allowing rotation to be distinguished from acceleration and laser arbitrary phase. Furthermore, electronically compensating the rotation-induced Doppler shifts of the Raman lasers allows operation at an effective zero rotation rate, improving sensitivity and facilitating sensitive lock-in detection readout techniques. Long-term stability is promising but not yet fully characterized. Potential applications include inertial navigation, geophysical studies and tests of general relativity.

Design and development of a MEMS-IDT gyroscope

Abstract: The design, development and performance evaluation of a novel radio frequency microelectromechanical systems (MEMS) gyroscope, based on a surface acoustic wave resonator (SAWR) and a surface acoustic wave sensor is presented in this paper. Most of the MEMS gyroscopes based on silicon vibratory structures that utilize the energy transfer between the two vibratory modes demand small fabrication tolerances to minimize signal output when there is no rotation (i.e. zero rate output). This 1 cm×1 cm gyroscope operates based on the principle of a surface acoustic wave (SAW) on a piezoelectric substrate. The SAWR creates SAW standing waves within the cavity space between the interdigital transducers (IDTs). The particles at the anti-nodes of a standing wave experience large amplitudes of vibration perpendicular to the plane of the substrate, which serves as the reference vibrating motion for this gyroscope. A number of metallic dots (proof masses) are strategically positioned at the anti-node locations so that the effect of the Coriolis force due to rotation will amplify the magnitude of the SAW that is generated in the orthogonal direction. The performance of this 74.2 MHz MEMS-IDT gyroscope has been evaluated using rate table and geophone set-ups, indicating very high sensitivity and dynamic range, which is ideal for many of the commercial applications. Unlike other MEMS gyroscopes, this gyroscope has a planar configuration with no suspended resonating mechanical structures, thereby being inherently robust and shock resistant. In view of its one-layer planar configuration, this gyroscope can be implemented for applications requiring conformal mounting onto a surface of interest.

Remote control device with gyroscopic stabilization and directional control

Abstract: A remote control device that utilizes a variable velocity gyroscope for stabilization as well as directional control. The gyroscope is mounted within a device shell and aligned vertically. When the device is stationary or traveling in a straight line, the rotational velocity of the gyroscope is constant. The direction of the moving device can be controlled by accelerating or decelerating the gyroscope.

High Q angular rate sensing gyroscope

Abstract: A structure and arrangement for improving the accuracy and efficiency of an angular rate sensing gyroscope is herein disclosed. Voltage pick-off conductors are applied to an area of the surface of a resonating element of an angular rate sensing gyroscope that is subject to substantially zero stress when the gyroscope is rotationally stationary. Actuator conductors are similarly applied to a resonating element at a location bounded by areas of the resonating element subject to substantially uniform levels of stress when the gyroscope is rotationally stationary. A method for improving the voltage response of a piezoelectric resonating element is also disclosed.

Tuned support structure for structure-borne noise reduction of inertial navigator with dithered ring laser gyros (RLG)

Abstract: Litton Marine Systems is manufacturing the third generation of the marine inertial navigators at the Sperry Marine Division using a new generation of dithered ring laser gyros (RLG) by Honeywell To satisfy the US and foreign navies, stringent military requirements for shock (MIL-STD-901D), vibration (MIL-STD-167) and structure-borne noise (MIL-STD-740) demanded that a new approach in vibration control be employed A combined structure supporting the inertial sensor assembly (ISA) is designed with nominal vibration frequencies outside the dithered ring laser gyro's forcing frequencies The ISA can then be rigidly supported without causing transmission of structure-borne noise Structure-borne noise levels are then attenuated while easily maintaining alignment of the sensor axes This paper addresses a passive vibration control solution implemented on the inertial measurement unit (IMU) of the MK39 Mod3A inertial navigator to meet the structure-borne noise levels of MIL-STD-740-2 By using a compact auxiliary mass, a tuned support structure housing a Honeywell DIG-20 ISA is achieved The robustness of this tuned support structure is demonstrated as Litton Marine Systems expands the product line with the enhanced system performance and high shock single axis indexed MK39 Mod3C inertial navigator system (INS) Presented analytical and experimental results demonstrate the effectiveness of the MK39 Mod3A auxiliary mass basic design This design required no further tuning for the MK39 Mod3C application The shock and vibration advantage of using this approach on an inertial navigator is highlighted The impact of the indexer assembly on system performance and wobble for the shock-isolated system is discussed

Equivalent ARMA model representation for RLG random errors

Abstract: It is shown that a mixture of random noises can be represented by a single equivalent ARMA (autoregressive moving average) model that is simple to implement. We applied the scheme to model RLG (ring laser gyroscope) random errors. An identification result from real test data confirms the validity of this approach.

Laser gyroscope having a circular waveguide with an asymmetrically tapered region

Abstract: A gyro comprising a laser device for generating laser beams to be propagated circuitally in opposite directions, wherein an electric signal is taken out from the laser device, the oscillation frequencies of the laser beams being different from each other when the laser device is held stationary.

System and method for providing cavity length control of a ring laser gyroscope

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.

Nonvolatile digital potentiometer trimmed ring laser gyroscope

Abstract: A ring laser gyroscope (RLG) is configured with control circuits that are capable of automatic calibration. The RLG generates two laser beams in opposite directions around a closed loop path to determine angular rotation of the RLG. The laser beams propagate in a laser gain medium, and a laser intensity monitor circuit is operatively connected to the laser gain medium to monitor an intensity of the laser beams propagating in the laser gain medium. A dithering circuit is provided, including a dithering motor for mechanically oscillating the RLG at a controlled frequency and dither angle. A gain circuit is operatively connected to a detector array of the RLG to amplify a detector signal therefrom. According to the present invention, an automatically variable resistance is provided to calibrate the laser intensity monitor circuit of the RLG, to control the dither angle at which the dithering motor mechanically oscillates the RLG, and/or to calibrate the gain circuit of the RLG. In one embodiment, the automatically variable resistance(s) is provided by one or more digital potentiometers connected to the relevant control circuitry.

Conformal MEMS-IDT gyroscopes and their comparison with fiber optic gyro

Abstract: This paper presents the design, fabrication and evaluation of a conformal Radio Frequency (RF) MEMS Gyroscope, base don surface acoustic wave resonators (SAWR) and surface acoustic wave sensors (SAWS), with very high sensitivity and dynamic range. Most MEMS gyroscopes based on silicon vibratory sensors utilizes the energy transfer between the two vibratory modes suffers serious drawback in producing identical resonating modes and hence to attain a sub-degree per second is quite impractical. This 1 cm X 1 cm gyroscope is working based on the principles of surface acoustic wave (SAW) standing waves on a piezoelectric substrate. The SWAR creates standing wave inside the cavity and the particles at the anti-nodes of standing wave experience large amplitude of vibrations, which serves as the reference vibrating motion for this gyroscopes. Arrays of metallic dots are strategically positioned at the anti- node locations so that the effect of Coriolis force due to rotation will acoustically amplify the magnitude of the waves. The performance of this 74.2 MHz MEMS Gyroscope has been evaluated using geophone setup and rate table setup, which shows very high sensitivity and dynamic range, which is ideal for the conventional applications. Unlike other MEMS gyroscopes, this gyroscope has a planar configuration with no suspended resonating mechanical structures, thereby giving rise to inherent robustness and shock resistance. With its one layer planar configuration, this gyroscope can easily be implemented to the applications requiring conformal mounting on to a surface of interest.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Ring laser gyro and its driving method

Abstract: PROBLEM TO BE SOLVED: To operate a ring laser type gyro at low current SOLUTION: A driving current is reduced based on a memory effect such that a laser beam remains within a ring resonator for a certain period of time Currents are passed through eight ring laser elements 1, 2, 3, 4, 5, 6, 7, and 8 at different times Ith=3 mA and I1=4 mA When total reflection occurs on the side face of the ring resonator of the element 1, evanescent light which propagates along a boundary face Exists when an oscillating wavelength is 155 μm, the seeping distance of the evanescent light is 0074 μm By disposing within the seeping distance an optical waveguide which constitutes the ring resonator, the laser beam circling within the ring resonator of the element 1 can be coupled to the element 2 COPYRIGHT: (C)2001,JPO

Parallel-beam sensor/actuator unit and its application to the gyroscope

Abstract: Proposes application of a parallel-beam structure to the gyroscope. The parallel-beam structure has the following significant features: 1) the tip moves in parallel at the end; 2) this structure converts the small displacement into a large concentrated strain; 3) even though some units are piled up, each unit does not interfere with another; and 4) the lateral rigidity is high. We analyzed these basic features by finite-element method analysis. We have proposed the parallel-beam sensor/actuator unit using this structure, and a new gyroscope. We show two methods to improve its performance; these are resonant frequency control and mechanical coupling suppression. It is concluded that the proposed structure is suited to the gyroscope.

Gyroscopes and gravitational waves

Abstract: The behaviour of a gyroscope at rest in the TT-grid of a gravitational plane wave is analysed. It is shown that spatial frames adapted to the observer carrying the gyroscope (with respect to which the precession must be measured) can be selected in order to have a precession which is dominated (to first order in the dimensionless amplitude h of the wave) only by one polarization state of the wave, giving the gyroscope a sort of filtering property. The discussion is then generalized to the case of a gyroscope in generic geodetic motion in the same background.

Calibration of Installing Errors of Laser SINS

Abstract: According to the performance index of strapdown navigation system and utilizing the doubleaxis turn table with arc second position accuracy,a rotating experiment method is given to calibrate the scale errors and installing errors of the laser gyro.This paper illustrates the theory of rotating experiment methos in detail,and discusses the accuracy of the experiment.The method is believed to meet the performance requirements of laser gyro strapdown system.

High accuracy ring laser interferometer using an external cavity ring laser

Abstract: An optical sensing apparatus for use in a ring laser interferometer measuring a physical quantity of an object includes a ring laser cavity formed by several internal mirrors, of which at least two internal mirrors are partly light-transmitting. The ring laser cavity generates two laser beams of an identical wavelength, the two laser beams propagating in counter direction to each other in the ring laser cavity. External mirrors are disposed at a distance from the ring laser cavity, whereby portions of the two laser beams, which pass through the internal mirrors and travel on optical paths toward the external mirrors, are reflected back into the ring laser cavity. The apparatus further includes at least one platform for mounting the external mirrors.

Ring laser gyro with an injected third beam

Abstract: A gyro includes a laser device for generating a first and second laser beams to be propagated circuitally in opposition directions. An electric signal is taken out from the laser device. A third laser beam having an oscillation frequency different from that of the first laser beam is led to enter the laser device so as to be propagated circuitally in the same direction as the first laser beam.

The C-II ring laser project

Abstract: The intensive use of Very Long Baseline Interferometry (VLBI), as well as Satellite and Lunar Laser Ranging (SLR, LLR) and the GPS-System allows for a precise monitoring of the current variations in earth rotation. The precision for the VLBI-system is as high as one part in 109 for a 24 hour measurement campaign. Since all these techniques are based on external reference frames, it is desirable to develop inertial sensors to the same resolution. Ring laser gyroscopes have the potential to be used for that purpose. The basic idea is to scale up the area surrounded by the two counter-rotating laser beams in order to gain higher sensitivity for the instrument with respect to the rotation rate. The Canterbury Ring Laser (C-I) consisting of a square of area 0.755 m2 has shown that ring lasers with a perimeter more than 60 cm are possible, in that the occurrence of more than one longitudinal mode of operation could be avoided by reducing the power of the circulating beams (Bilger et al., 1993). The next instrument C-II with an area of 1 m2 demonstrated many of the mechanical requirements for a stable instrument. It was constructed from a monolithic block of Zerodur, so that the size of the area does not change under temperature variations. A successfully built prototype for a large ring (G0) finally proved that it is possible to build a ring laser gyroscope with at least 14 m length of cavity (Rowe et al., 1999). This means that most of the demands for a highly sensitive inertial earth rotation sensor are met. On this basis a high resolution and highly stable instrument, suitable for geophysical applications, can be constructed.

Fiber optic laser gyroscope using phase sensitive detection method

Abstract: PURPOSE: A fiber optic laser gyroscope is provided to improve performance by applying a phase sensitive detection unit with a signal processing method for removing an error due to strength difference between two pulses. CONSTITUTION: A multi-directional combiner(334) is inserted for the detection of a mode-locked pulse row. The pulse ratio is converted to an electric signal via an optical detector(380). By using a phase sensitive detector(39), an element with a frequency of the same as that of a phase-modulated signal and on the same phase is detected from the electric signal.

Fundamental characteristics of semiconductor ring laser gyroscopes

Abstract: Semiconductor ring lasers have many capabilities of realizing new functional devices. In this paper, we propose a novel optical inertial rotation sensor using a semiconductor ring laser. If a semiconductor ring laser operates as an optical inertial rotation sensor, a very small and simple optical gyroscope can be realized. To our knowledge this is the first demonstration of a semiconductor ring laser gyroscope (S-RLG). Experimental results are as follows. (1) The Sagnac frequency shift can be detected as a beat note by the terminal voltage change of the semiconductor ring laser without branching the circulating optical power. Therefore, the S-RLG system can be constructed very simply as compared with already proposed optical gyroscopes. (2) The detected beat frequency between two counterpropagating lasers in the S-RLG is directly proportional to the applied rotation rate. (3) Furthermore, we present data demonstrating the injection locking phenomenon around low rotation rate. These results verify that the proposed S-RLG operates as an optical inertial rotation sensor based on the Sagnac effect. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 73–78, 2000

Device and process for measuring the mutual orientation of hollow cylinder and an assigned cut edge

Abstract: A method and apparatus for measuring the mutual orientation of an optionally oriented hollow cylinder and a cut end of a body containing the hollow cylinder by employing a high-precision laser gyroscope. In using this method, the orientation measurements can be obtained in a more economical and time efficient manner than those employed using conventional methods. The method involves first placing a laser gyroscope on the inside wall of a hollow cylinder and electronically registering the three-dimensional orientation of said laser gyroscope according to at least two angular coordinates relative to a laboratory system; storing the three-dimensional orientation as a first measurement result; placing the laser gyroscope directly on the cut end, or indirectly on the cut end by resting it on a support mechanism that rests on the cut end; electronically registering the three-dimensional orientation of said laser gyroscope according to at least two angular coordinates relative to a laboratory system; storing the three-dimensional orientation as a second measurement result; comparing said first and second measurement results to obtain a value of a phase displacement angle; and displaying the value of the determined phase displacement angle. The device is especially suited for checking the orientation of cylinder heads and cylinder bore axes of large-volume diesel engines.

Microwave gyroscope—novel rotation sensor

Abstract: A high-performance microwave gyroscope (MG) is theoretically developed for the first time to our knowledge. The MG is based on the Sagnac effect in a microwave ring resonator, where a specially tailored phase shifter (PS) on the basis of surface acoustic waves is inserted. In the result, the MG has a few orders higher sensitivity and dynamic range than state-of-the-art laser gyros, so it can serve as an advanced rotation sensor in navigation and fundamental sciences. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 255–257, 2000.

Control of laser beams in a ring laser gyro

Abstract: A ring laser gyro wherein a first and a second laser beam propagate with propagating directions different with each other comprises electrode areas on an optical waveguide configuring the ring laser and controls an current injected or a voltage applied to the electrode areas, wherein the oscillating frequencies of the first and second laser beams are different from each other, thereby causing an increase and a decrease in the beat frequency enabling to detect the direction and the speed of a rotation at the same time. With regards to a method for detecting a rotation, the anode of the laser gyro is connected to an operational amplifier. Since the signal outputted from the operational amplifier has a frequency corresponding to the angular speed, it is converted into the voltage by a frequency-voltage conversion circuit so as to detect a rotation. This same method can be used for other types of gyros such as a semiconductor laser gyro, a gas lager gyro and the like.

Application of a ring laser for measurement of track geometrical parameters

Abstract: Over last years, the ring lasers are wildly used as sensors of inertial measuring and navigational systems, due to such exceptional properties, as high accuracy, wide dynamic range, non-sensitivity to linear acceleration, et al. In the conditions of growing speeds and density of railway traffic, growing requirements to accuracy of measurements, the systems on ring laser gyro (RLG) and accelerometers seem to be the most promising. Track checking includes the use of track measuring cars or carriages automatically recording the railway condition control of the railway under a load by the use of specialized track measuring vehicles equipped with computers for registration and analysis of measurement results. Although the ring laser gyroscope provides a very high accuracy in the measurement of angular rates and angles, it does have one significant problem -- synchronization of the counter-propagating waves. This effect is usually referred to as lock-in. There were many solutions to the lock-in problem, but mechanical dithering of the RLG was finally adopted as a practical solution to it.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Laser device having an optical waveguide for discerning movement of an optical gyroscope and an optical gyroscope utilizing same

Abstract: A gyro comprising a laser device for generating laser beams to be propagated circuitally in opposite directions, wherein an electric signal is taken out from the laser device, the oscillation frequencies of the laser beams being different from each other when the laser device is held stationary.

Process and gear for assembly and adjustment of symmetrical laser gyroscope with prisms of total internal reflection and symmetrical laser gyroscope

Abstract: laser gyroscopic technology. SUBSTANCE: prisms and monoblock are positioned on adjustment gear. Base faces of monoblock are pressed against base surfaces of adjustment gear. Prisms are moved with location surfaces to base faces of monoblock to contact. Presence of interference picture between base surfaces is controlled. Prisms are pressed till optical contact between location surfaces of prisms and base faces of monoblock is achieved. Gear for realization of process includes adjustment plate with base polished surface and two pairs of standard rests. Monoblock of gyroscope has base surface and pairs of base faces. Position of optical prisms with reference to monoblock is set by position of base surfaces of pairs of prisms relative to base surface and pairs of base faces of monoblock. EFFECT: enhanced precision, reduced manufacturing cost and increased adaptability of proposed gyroscope for mass production. 3 cl, 5 dwg

Ring laser device and control of spectrum line width of ring laser gyro apparatus

Abstract: PROBLEM TO BE SOLVED: To provide a ring laser device and an apparatus and a method for controlling the spectrum line width of ring a laser gyro apparatus which has no need of an optical system for narrowing the band and allows the entire size to be reduced. SOLUTION: In a feedback circuit, a pulse having the most narrow width is selected as a reference among three pulses just preceding a pulse under interest to judge whether the width of the pulse under interest is greater or smaller than that of the reference (Fig. 3, 9). The feedback circuit increase or degreases a current to be injecting to a ring laser according to the difference between the now noticed pulsewidth and the reference pulsewidth (Fig. 3, 10) and takes the pulsewidth of one pulse just preceding an always noticed pulse as a reference pulsewidth so that the pulsewidth of the always noticed pulse may be less than the reference pulsewidth.

Laser gyro active media gas flow determination

Abstract: The being advantages ofthe laser gyro against the precise gyro with rotating mass are the cost efficiency and the theoretical rapidity for practical systems. There have been unavailable the relevant publications on the laser gyro's necessary precision providing and also on its rapidity and on the nonstationary systematic errors excluding in real time. on the other hand it is known that output frequency of continuous wave linear laser is establishing, even in stationary conditions, during the transition time of 20 minutes up to 3 hour for different laser types '. Thus most traditional measurements with continuous wave laser are used in stationary conditions, when the counting of output characteristics is begun after the necessary transition time is gone 2 Since the output ofring laser is proportional to the active media generation frequency, the laser gyro has the nonstationary systematic error with the same value of the transition time. The investigations have been performed would be derived in the two groups. There are the laser gyro error's "mathematical models" and so-called "dynamic compensation methods" discussed in . The "dynamic compensation methods" are based on using of the temperature-depending elements in feed back system of the output signal. The both methods require the lasting measurements of laser gyro output in the stationary conditions to define the coefficients of the error model or to determinate the characteristics ofthe temperature-depending elements. These measurements must be repeated or the parameters must be automatically tuned for any other case. So it is unreasonable. The plasma heat regime influence on the precise ring laser output is considered in this work following to The case of the heat influence on the plasma without the dimensions changing is supposed. The thin effects, as modes drag, mode competition and radiation trapping ,do not be considered in order to the more clear idea. The each component of laser active media (electron gas, ion gas, excited atoms, etc.) has its own optical properties and puts its deposit in the ring laser output instability The analysis resulted in shows that, in case of constant electron and ion concentrations and when the frequency of electron-ion collisions is comparatively low, one obtains the Fresnel drag effect with electro-neutral atoms only.

Digitally processed, phase-reading fibre gyroscope

Abstract: We present a simple digital processing method that provides a significant improvement for the performance of a phase-reading open-loop fibre-optic gyroscope. The phase-reading gyroscope measures the angular speed in terms of a phase difference between the two counter-propagating beams in the Sagnac interferometer. Instead of electronic phase meters we use a very simple PC-based digital process which computes the Sagnac phase. With this method we measure rotation rates down to 100°h−1. The errors of this scheme are studied for different signal-to-noise ratios and the number of bits of the analog-to-digital converter.

Fast Initial Alignment and Its Errors of RLG Strapdown Inertial Navigation System for Land Vehicle

Abstract: To study the fast initial alignment of ring laser gyro (RLG) strapdown inertial navigation system for land vehicle, the two-position alignment technology was adopted, the principle and software flow of the method were presented, the alignment precision was tested and the error sources having influence on alignment precision were analyzed. The influences of gyro constant drift and accelerometer bias on alignment precision are eliminated by the two-position alignment method. Moreover the three gyros constant drifts and three acce1erometers biases were calibrated at alignment and compensated in the navigation state, so the navigation precision was improved effectively.