Showing papers on "Inertial reference unit published in 1972"

A Redundant Strapdown Inertial Reference Unit (SIRU)

Abstract: The hardware and software mechanization of the SIRU redundant strapdown system is described. Six gyroscope and six accelerometer modules are arranged with their input axes in a unique symmetrical pattern that corresponds to the array of normals to the faces of a dodecahedron. This configuration enables optimal data processing with self-contained failure isolation for up to two out of six of either instrument module type, and continued operation with as many as three out of six failures. Each instrument module is a prealigned normalized assembly that contains its own torque-to-balance electronics, temperature controller, etc. The modular features provide enhanced system maintainability. Redundant hardware concepts are applied in the supporting instrumental package electronics (dual-power supplies, triple-redundant clocks, etc.). The degree of redundancy use in the Electronics Assembly is based upon the relative reliability of the individual circuits and circuit isolation concepts. The system has been mechanized so that satisfactory operation is achieved with a variety of electronic and instrument degradation or catastrophic failures and is free from the possibility of a system failure resulting from a single-point failure mechanism. Descriptions of the software data processing and failure isolation algorithms are presented with an itemization of the system's computational real-time and memory requirements.

Ships inertial navigation storage and retrieval system (sinsars)

Abstract: A system for storing and retrieving the outputs of inertial sensors (accelerometers) and of other appropriate quantities such as EM Log Data (velocity reference), time, gimbal angle information and depth gauge data (depth reference aboard a submarine) of an inertial system, in order to be able to continue navigation with reasonable accuracy at some future time after a system failure without the need of external information to re-initialize the solution of the navigation problem. The system comprises an inertial measuring unit (IMU), a navigation computer, a memory unit, and an electronic switching and timing unit. Sensor information from the inertial measuring unit (IMU) is stored temporarily during non-availability of the navigation computer. The sensors of the inertial measuring unit continue to supply information for storage during the time the navigation computer is inoperative without requiring command and/or control information from the computer. The navigation computer processes the sensor information stored during its failure at a rate faster than that of real time data processing until it has processed all of the stored sensor information. The navigation computer goes into its normal processing mode thereafter. Thus accurate navigation is continued without the submarine coming to the surface for resets (reference information).

Theory of gyro with rotating gimbal and flexural pivots

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Gyro and accelerometer failure detection and identification in redundant sensor systems.

Abstract: Algorithms for failure detection and identification for redundant noncolinear arrays of single degree of freedom gyros and accelerometers are described These algorithms are optimum in the sense that detection occurs as soon as it is no longer possible to account for the instrument outputs as the outputs of good instruments operating within their noise tolerances, and identification occurs as soon as it is true that only a particular instrument failure could account for the actual instrument outputs within the noise tolerance of good instruments An estimation algorithm is described which minimizes the maximum possible estimation error magnitude for the given set of instrument outputs Monte Carlo simulation results are presented for the application of the algorithms to an inertial reference unit consisting of six gyros and six accelerometers in two alternate configurations

New Method for the Alignment of Inertial Navigation Systems

Abstract: Before an inertial navigation system is used, an initialization procedure is required. The initialization procedure consists of alignment of the platform and the entry of position and velocity. A new method for the alignment of inertial navigation systems is presented in this paper. Alignment of the platform is usually accomplished by a procedure known as gyrocompassing. When gyrocompassing is employed, the inertial system is operated in a damped mode and relatively little base motion is tolerated. The well-known Kalman filter algorithm can also be used in a real time computer to align inertial navigation systems. The method discussed in this paper is in some respects similar to the Kalman filter; however, the definition of a co variance matrix is not required. Like the Kalman filter, the technique can be used to align damped and undamped inertial systems. It can be used to align inertial systems on moving or stationary vehicles. It can also be used to compute gyro drift biases in addition to platform misalignment angles. Computer simulations relating to a number of initial conditions and unmodeled error sources are discussed. It is shown that the algorithm can be used to align a system with considerable base motion.