Showing papers on "Ring laser gyroscope published in 1976"

Electromagnetic wave ring resonator

Abstract: An electromagnetic wave ring resonator is disclosed including means to spatially rotate the electromagnetic field distribution of waves resonant therein about the direction of propagation of such waves to enable such waves to resonate with opposite senses of circular polarization, and means, including a laser amplifier medium, to provide different indices of refraction to resonant waves of the same sense of circular polarization as they pass through such laser amplifier medium in different directions. With such arrangement the two mentioned means enable the waves to resonate with four different frequencies. In a laser gyroscope using such ring resonator the electromagnetic field distribution rotating means includes a catoptric arrangement which, together with the last-mentioned means, reduces the loss, scatter and linear birefringence associated with the ring resonator included in such gyroscope. The last-mentioned means produces the Zeeman effect in the laser medium and efficiently provides different optical pathlengths for waves passing through such medium because the magnetic field vector of such waves interacts with the processing atomic magnetic dipoles of the amplifier medium at the emission frequency of such amplifier medium.

Stimulated brillouin scattering ring laser gyroscope

Abstract: A stimulated Brillouin scattering (SBS) ring laser gyroscope. The SBS laser gyroscope is fabricated from a single-mode optical fiber waveguide and is optically coupled to a laser to accommodate being pumped in two directions by laser radiation having sufficient energy to induce stimulated Brillouin scattering radiation (SBS). The apparatus includes means for extracting a portion of each of the SBS radiation from the single-mode optical fiber waveguide and superimposing the extracted portions to permit detection of a beat frequency therebetween. The beat frequency detected is indicative of the rate of angular rotation of the area circumscribed by the single-mode optical fiber waveguide. Means are provided to accommodate a significant reduction in the required laser pumping power.

Counterbalanced oscillating ring laser gyro

Abstract: A compact and reliable dithered laser gyro utilizes a rectangular laser path geometry to reduce scattering and thereby improve anti-locking capabilities of the laser gyro. In addition, the rectangular geometry serves to reduce the overall package size of the laser gyro and permits the mounting of the anti-lock mechanical dithering drive mechanism within the laser gyro unit. A counterbalance is also provided to reduce vibration from the unit.

Fiber Laser Gyroscopes

Abstract: The application of the optical fiber waveguides to laser gyroscopes is divided into two sections: 1) The ring interferometer and 2) The ring laser. Experiments show that a well defined, stable interference pattern can be obtained using a single mode fiber. This together with the experimentally obtained coupling efficiency of laser radiation into the fiber (-50%) indicate that in addition to a sensitive ring interferometer gyroscope a ring laser gyroscope can be built using a single mode fiber waveguide as the passive part of the laser cavity.© (1976) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Estimation of dynamic alignment errors in shipboard firecontrol systems

Abstract: A problem in fire control systems is the estimation of the relative alignment between remotely located target sensor and weapon coordinate frames. This paper describes and analyzes a shipboard system concept for estimating initial misalignments and compensating ships dynamic bending and flexure. The concept uses miniature strapdown inertial sensor assemblies at remote sensor/weapon stations to monitor instantaneous differences in rotational and translational motions. Equations are developed for Kalman filter estimation of alignment and flexure errors using incremental angular displacement and incremental velocity matching measurements. Optimal filter performance predictions are shown graphically for calm and rough sea conditions for both conventional and ring laser gyro inertial sensor assemblies.

Differential laser gyro development

Abstract: The Differential Laser Gyro (dilag) is a significant advancement in strapdown inertial guidance. Its four simultaneously oscillating modes allow it to retain the advantages inherent in a laser gyro without many of the drawbacks found in present two mode units. The DILAG concept employs two complete laser gyros operating in the same optical cavity. The gyros are distinguished from each other by their polarization state; one is right circularly polarized (RCP), while the other is left circularly polarized (LCP). Both gyros are biased out of their respective dead-band regions by the same Faraday cell. Because of their opposite polarization states, the gyros respond with equal but opposite frequency shifts to a given rotational input rate. When one gyro output is subtracted from the other, the result is a doubling of rate sensitivity combined with a cancellation of the common Faraday bias. Operated in this manner, the DILAG becomes insensitive to variations in the Faraday bias and thereby eliminates the usual requirements for Faraday cell stability. In addition the DILAG requires no dithering, either mechanical or electrical. This paper considers these points as well as a number of other special characteristics of the DILAG which offer significant improvements in gyro performance. Among those areas discussed are the reduction in shielding requirements, the elimination of all moving parts including those associated with cavity length control, and the advantages occurring in data collection and self check capability.

Failure detection and isolation investigation for strapdown skew redundant tetrad laser gyro inertial sensor arrays

Abstract: The degree to which flight-critical failures in a strapdown laser gyro tetrad sensor assembly can be isolated in short-haul aircraft after a failure occurrence has been detected by the skewed sensor failure-detection voting logic is investigated along with the degree to which a failure in the tetrad computer can be detected and isolated at the computer level, assuming a dual-redundant computer configuration. The tetrad system was mechanized with two two-axis inertial navigation channels (INCs), each containing two gyro/accelerometer axes, computer, control circuitry, and input/output circuitry. Gyro/accelerometer data is crossfed between the two INCs to enable each computer to independently perform the navigation task. Computer calculations are synchronized between the computers so that calculated quantities are identical and may be compared. Fail-safe performance (identification of the first failure) is accomplished with a probability approaching 100 percent of the time, while fail-operational performance (identification and isolation of the first failure) is achieved 93 to 96 percent of the time.

Redundant Strapdown Laser Gyro Navigation System

Abstract: For the last several years, NASA has pursued the development of low-cost high-reliability inertial navigation systems that would satisfy a broad spectrum of future space and avionics missions. Two specific programs have culminated in the construction of a Redundant Strapdown Laser Gyro Navigation System. These two programs were for development of a space ultrareliable modular computer (SUMC) and a redundant laser gyro inertial measurement unit (IMU). The SUMC is a digital computer that employs state-of-the-art large-scale integrated circuits configured in a functional modular breakdown. The redundant laser gyro IMU is a six-pack strapdown sensor package in a dodecahedron configuration which uses six laser gyros to provide incremental angular positions and six accelerometers for linear velocity outputs. The sensor arrangement allows automatic accommodation of two failures; a third failure can be tolerated provided it can be determined. The navigation system also includes redundant power supplies, built-in test-equipment (BITE) circuits for failure detection, and software which provides for navigation, redundancy management, and automatic calibration and alignment.