Schuler tuning

Abstract: An autonomous covert Inertial Navigation System uniquely suited for underwater applications wherein Schuler and siderial errors are bounded without external navigation aids or active instrumentation of ground speed is achieved by integrating a conventional Inertial Navigation System with a gravity gradiometer capable of measuring gravity field components independently of platform accelerations.

Abstract: This paper derives basic error equations of inertial navigation which apply to any properly constructed inertial navigator. The equations are deduced from the integral equations of inertial navigation by a vectorial analysis. A major result of this analysis is a set of fundamental error propagation equations that has apparently been missed. These equations regard the absolute navigational errors. The conventional velocity and position errors are shown to be transfer errors.

Abstract: Inertial Navigation Systems have found universal application both militarily and commercially. They are self-contained, nonradiating, nonjammable, and sufficiently accurate to meet the requirements of users in a most satisfactory manner. An overview of inertial navigation is provided, followed by several sections detailing a specific, but different mechanization approach. A Ring Laser Gyro (RLG) based navigation system design is reviewed with special emphasis directed at requirements for navigation accuracy and alignment time. Along with discussions of the RLG unit, an introduction to a novel accelerometer approach, the Vibration Beam Accelerometer (VBA), is provided. A gimballed, self-contained High Accuracy Inertial Navigation System, denoted HAINS, represents one approach toward achieving navigation capability of 0.2 nmi / h and an rms velocity of 1.5 ft / s per axis while retaining the form and fit and affordability of standard inertial tactical flight navigators. The Stellar-Inertial Navigation section illustrates the bounding of position and verticality errors thus achieving exceptional accuracies. Two gyroscopic approaches, presently in development are finally discussed. The Fiber Optic Gyroscope (FOG) and Magnetic Resonance Gyroscopes (MRG's) are of interest for navigation because of their potential for low cost and excellent reliability.

Abstract: Significant research has been conducted in recent decades on developing a practical all-accelerometer inertial navigation system and on developing a practical moving-base gravity gradiometer. The former strives to measure kinematic motion in the presence of unwanted variations in gravity; the latter endeavors to measure variations in gravity in the presence of unwanted motion. Thus, goes the adage, one person's signal is another person's noise. In this paper, a mathematical relationship is derived that links the two concepts together. It is demonstrated that a complete solution to real-time navigation and gravity gradient determination can be performed simultaneously and unambiguously using all-accelerometer inertial measurements only. Although the separation of gravity from kinematic motion appears to violate Einstein's principle of equivalence, this is not the case. Nonetheless, accelerometer technology is not yet of sufficient maturity to allow a practical implementation of this concept, but advances certainly are being made that could result in a practical implementation perhaps within a decade.