Showing papers on "Inertial navigation system published in 1990"

Inertial navigation

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.

The Meteorological Measurement System on the NASA ER-2 Aircraft

Abstract: A Meteorological Measurement System (MMS) was designed and installed on one of the NASA high-altitude ER-2 aircraft (NASA 706). The MMS provides in situ measurements of free-stream pressure (+ or - 0.3 mb), temperature (+ or - 0.3 C), and wind vector (+ or - 1 m/s). It incorporates a high-resolution inertial navigation system specially configured for scientific applications, a radome differential pressure system for measurements of the airflow angles, and a compact, computer-controlled data acquisition system to sample, process and store 45 variables on tape and on disk. The MMS hardware and software development is described, and resolution and accuracy of the instrumentation discussed. Custom software facilitates preflight system checkout, inflight data acquisition, and fast postflight data download. It accommodates various modes of MMS data: analog and digital, serial and parallel, and synchronous and asynchronous. Flight results are presented to demonstrate the capability of the system.

Separate bias Kalman estimator with bias state noise

Abstract: A modified decoupled Kalman estimator suitable for use when the bias vector varies as a random-walk process is defined and demonstrated in a practical application consisting of the calibration of a strapdown inertial navigation system. The estimation system accuracy associated with the modified estimator is shown to be essentially the same as that of the generalized partitioned Kalman estimator. Considering that the sensor error random rates assumed in the example are on the order of 5 to 10 times greater than normally associated with contemporary strapdown systems, it may be inferred that inertial navigation systems possessing more typical sensor error random growth characteristics should be amenable to a decoupled estimator approach in a broad spectrum of aided-navigation system applications. This should also be true in a variety of other applications in which the bias vector experiences only limited random variation. >

Optimal strapdown attitude integration algorithms

Abstract: The paper examines various algorithms for integrating the noncommutivity rate equation arising in the implementation of the attitude reference function of a strapdown inertial navigation system, and derives a class of optimized algorithms for performing this integration. The accuracy characteristics associated with each of the algorithms, when the system is exposed to pure coning motion, as well as to a generalized vibrational environment, are defined. The class of optimized algorithms is shown to minimize the mean error in the correction provided by the algorithm in a generalized vibrational environment.

Inertial navigation sensor integrated obstacle detection system

Abstract: A system that incorporates inertial sensor information into optical flow computations to detect obstacles and to provide alternative navigational paths free from obstacles. The system is a maximally passive obstacle detection system that makes selective use of an active sensor. The active detection typically utilizes a laser. Passive sensor suite includes binocular stereo, motion stereo and variable fields-of-view. Optical flow computations involve extraction, derotation and matching of interest points from sequential frames of imagery, for range interpolation of the sensed scene, which in turn provides obstacle information for purposes of safe navigation.

Testing a decentralized filter for GPS/INS integration

Abstract: A decentralized Kalman filter strategy is presented and applied to GPS/INS (Global Positioning System/inertial navigation system) integration. Two Kalman filters are used. One is a local filter, processing GPS data and providing locally best estimates of position and velocity. The second is an INS filter which uses the results from the GPS filter as updates to the estimates obtained from the inertial data. Because of the high short-term accuracy of the inertial system, the position results from INS can be used for cycle slip detection and correction. The major advantages of this method are the flexible combination of GPS and INS and the simplicity of the implementation. Compared to centralized filtering, the decentralized filter gives globally the same optimal estimation accuracy as the centralized Kalman filter. The accuracy does not deteriorate when a suboptimal cascaded filter is used, which has some advantages in terms of computational efficiency. Extension of this method to more sensors is straightforward. Numerical results are used to illustrate the salient features of the method. >

The alignment of ship launched missile IN systems

Abstract: The author outlines the requirements for on-board inertial navigation systems in the next generation of tactical missiles. The significance of alignment accuracy in the performance of such missile systems is discussed, drawing attention to the physical processes which introduce alignment error in a ship launched missile. Two different techniques which may be used to alleviate the problems of alignment inaccuracy are discussed. The first method involves the use of shipboard inertial measurements to carry out an alignment prior to launch. Such methods are strongly dependent on ship motion. The second method involves tracking the missile with the ship's radar and the use of the radar measurements to aid the missile navigation system during flight. The author outlines the integration of the different measurements, the algorithms needed to implement each scheme and concludes with a comparison of the relative merits of shipboard and in-flight alignment.

Application of Kalman filtering to the calibration and alignment of inertial navigation systems

Abstract: Problem areas and practical solutions in the development of large-dimension Kalman filters for the calibration and alignment of complex inertial guidance systems are discussed. The basic vector attitude error equation is augmented by gyro and accelerometer unknown parameters. The parameter estimation problem is converted into a state estimation problem. A complete approach and description of the dual extended Kalman filter, one for accelerometers and one for gyros, is given. To reduce computational load, a technique of prefiltering (data compression or measurement averaging) has been implemented in the mechanization with very little degradation in the performance of the filter. The models of gyros and accelerometers used are described in detail. A technique for generating parameter excitation trajectories which provides observability of instrument parameters has been developed by maximizing the information matrix. A typical set of results for a simulator data set for parameter estimates and innovation sequences is given to show the performance, convergence, accuracy, and stability of the filter estimates. >

A Strapdown Inertial Algorithm Using an Earth-Fixed Cartesian Frame

Abstract: An algorithm for processing strapdown inertial data in an earth-fixed Cartesian frame is developed in this paper. It is compared with the standard algorithm that uses the local-level frame and the geographic coordinate system for the model formulation. A general formulation of the modeling equations for the two approaches is given, and the linearization of the equations and the formulation of the appropriate Kalman filter are outlined. The derivation of the reference gravity model for both frames is briefly discussed, and numerically efficient formulas for the model's computation are given. In the case of the Cartesian algorithm, this leads to new formulas for all three components of the gravity vector. Real data are used to compare the two algorithms and to show that the accuracy is the same in both cases, but that the Cartesian formulation is about 30 percent more efficient.

Observability analysis of piece-wise constant systems with application to inertial navigation

Abstract: A method for analyzing the observability of time-varying linear systems which can be modeled as piecewise constant systems is presented. An observability matrix for such systems is developed for continuous and discrete time representations. A stripped observability matrix is introduced which simplifies the analysis in cases where the use of this matrix is legitimate. This approach circumvents the difficulty associated with the investigation of the observability Gramian of time-varying linear systems. It is shown that instead of investigating a Gramian, only a constant observability matrix needs to be investigated. Moreover, it is shown that if certain conditions on the null space of the dynamics matrix of the system are met, the observability matrix can be greatly simplified. A step-by-step observability analysis procedure is presented for this case. The method is applied to the analysis of in-flight alignment of inertial navigation systems whose estimability is known to be enhanced by maneuvers. >

Passive gravity gradiometer navigation system

Abstract: A totally passive navigation system using gravity gradient map matching techniques is described. The system requires no external information and is nonemanating and nonjammable. The system consists of an inertial system updated by position fixing from map matching to gravity gradiometer outputs. The advantages of the system over existing terrain map matching systems are covered. The difficult instrumentation problem is solved with proven hardware by the Bell rotating accelerometer gravity gradiometer system. The issue of the database necessary for gravity gradient map generation is addressed. The results of an accuracy analysis in the form of a parametric study for such variables as altitude, speed, number of gradiometers, quality of the gradiometers, and quality of the inertial components are presented. >

Integrated fault-tolerant air data inertial reference system

Abstract: A fault-tolerant air data and inertial navigation reference system utilizes skewed axis inertial sensors and fault-tolerant redundant electronics to provide higher redundancy with fewer parts. Parallelly operating processor circuits each receive the individual outputs of six skewed-axis gyros and six skewed-axis accelerometers. Each processor independently processes parity equations using the outputs to identify malfunctioning sensors. Further, the output of each processor is transmitted to three parallelly operating voter circuits. The voters are operable to discard a processor if its output does not agree with the majority. The voter outputs are similarly fed back to the processor circuits, which compare these outputs, and discard any voter whose output disagrees with the majority, thus providing a completely integrated system.

Inertial navigation sensor integrated motion analysis for obstacle detection

Abstract: A maximally passive approach to obstacle detection is described, and the details of an inertial sensor integrated optical flow analysis technique are discussed. The optical flow algorithm has been used to generate range samples using both synthetic data and real data (imagery and inertial navigation system information) obtained from a moving vehicle. The conditions under which the data were created/collected are described, and images illustrating the results of the major steps in the optical flow algorithm are provided. >

Inertial navigation system with automatic redundancy and dynamic compensation of gyroscope drift error

Abstract: An inertial navigation system with automatic redundancy and dynamically calculated gyroscopic drift compensation utilizes three, two-degree of freedom gyroscopes arranged whereby any two of the gyroscopes form an orthogonal triad of measurement sensitive axes. The input axes of the three gyroscopes form three pairs of parallel input axes, each pair of parallel input axes corresponding to one axis of the orthogonal triad of axes. The three gyroscopes are operated in a plurality of preselected combinations of both clockwise and counter clockwise directions, thus changing the direction of the angular momentum vector by 180°. Parity equations are formed from each pair of gyroscope outputs whose measurement sensitive axes are parallel. The parity equations include combinations of gyroscope pairs that have been operated in both the clockwise and counterclockwise directions. Gyroscope drift estimates are then computed using the parity equations to provide individual gyroscope lumped drift corrections (self-calibration) to the inertial guidance and navigation system.

The Effect of Geometry on Integrity Monitoring Performance

Abstract: A variety of integrity monitoring and failure detection algorithms have been described in previous lite:ature for G~S and inertial. navigation systems. .These ~gorlthms have In common their use of redundant 1DfOrmatl~n to detect and identify system component faults. Receiver Autonomous Integrity Monitoring (RAIM) algorithms designedfor GPS receiversmake use or redundant measurementsto GPS satellites to detect and isolate faults in any individual satellite signal. Fault-tolerant in~rtial navigationsystemsused~tafr?m redundant instruments in a similar Cashionto detect and Identify faults in any instrument. Onekey areaof interestis the minimum GPSsatellitegeometry conditions that are required for RAIM algorithms to be effective. The Radio Technical Commission for Aeronautics (RTCA) Special Committee 159 has prepared a -Uinimum bperational Performance Standard (MOPS) which specifies the alarm threshold, detection probability and allowable false alarm rate for different pqasesof flight. This paper derives a geometry parameterthat canbe usedto definewhenRAIM is effectivefor ea.chphaseof flight. . . The integrity geometry parameters can also be app~ed. in evaluating the performance of redundant inertial naVIgation systems in the presenceof single or multiple instrument faults. To continue navigating.in tae presenceof a failure, it is necessarynot only to detect that a failure occurred but also identify the faulty component. The integrity geometry parameter allows the optimum geometry to be determined for maximizing the probability of failure detectionand isolationin the presenceof multiple instrument faults.

GPS/INS integration on the Standoff Land Attack Missile (SLAM)

Abstract: The Standoff Land Attack Missile (SLAM) is a worldwide, all-weather, precision-strike weapon system deployed from carrier-based aircraft. In the primary mode of operation, target location and other mission data are generated from intelligence sources available on the aircraft carrier and loaded into the missile prior to aircraft takeoff. After missile launch, the SLAM inertial navigation system (INS) guides the missile along the planned trajectory. Updating the missile INS from the Global Positioning System (GPS) during flight provides precise midcourse navigation and enhances target acquisition by accurate, on-target pointing of the SLAM Maverick seeker. The GPS/INS avionics and software integration used for SLAM are described in detail, along with some of the design tradeoffs that led to the approach. The avionics configuration integrates the Harpoon midcourse guidance unit, which includes a strapdown inertial sensor package and digital processor, with a Rockwell-Collins single-channel, sequential GPS receiver processor unit (RPU), a derivative of the GPS phase-III user equipment. In addition to the GPS receiver elements the RPU contains the navigation processor, which executes the SLAM navigation, Kalman filter algorithms, and other guidance algorithms including seeker pointing. Flight-test results of the SLAM GPS-aided INS are also included. >

Estimating the residual error of the reflectivity displacement method for aircraft motion error extraction from SAR raw data

Abstract: The performance of the reflectivity displacement method is reported. The reflectivity displacement method extracts all the necessary motions of the aircraft from the radar backscatter signal using a new radar configuration and new methods for evaluating the azimuth spectra of the radar signal. Hence, an inertial navigation system is unnecessary for many applications. An error analysis of this method is carried out, and a comparison of two processed images with and without motion compensation is shown, proving the estimated performance. >

Strapdown Astro‐Inertial Navigation Utilizing the Optical Wide‐angle Lens Startracker

Abstract: This paper discusses the application of strapdown stellar inertial systems as autonomous navigators for manned aircraft, ships, missiles, and remote piloted vehicles. It analyzes the implications of gyroscopic performance, artificial stellar image stabilization, star density, sky visibility, and sky background irradiance considerations for system performance. It concludes that a high-precision, reliable, low-cost stellar inertial system can be achieved by eliminating gimbals and combining a strapdown INS with an optical wide-angle lens startracker (OWLS).

Method and apparatus of integrating Global Positioning System and Inertial Navigation System without using accelerometers

Abstract: A method and arrangement for integrating a Global Positioning System and an Inertial Navigating System without the use of accelerometers to provided a velocity steering signal that is utilized in the guidance of a flying vehicle, such as a space craft. The method and arrangement do not require the use of accelerometers. A mechanization for interfacing the integrated Global Positioning System and the Inertial Navigating System with a flight control system which controls a flying vehicle is disclosed.

Reliability analysis of fault-tolerant IMU architectures with redundant inertial sensors

Abstract: A systematic reliability analysis procedure for evaluating fault-tolerant inertial measurement unit (IMU) architectures is described. This reliability analysis procedure is based on modeling the system architecture, the component reliabilities, and the redundancy management. The component reliabilities are based on constant failure rates and exponential failure distributions. The procedure computes both the overall reliability of the IMU and the major contributors to the IMU reliability. This reliability analysis procedure is used to evaluate and compare three state-of-the-art fault-tolerant IMU architectures: the triple triad architecture, the dual quad architecture, and the hexad architecture. >

Terrain referenced navigation

Abstract: An attempt is made to provide airframe manufacturers and system integrators with an overview of terrain referenced navigation, with particular emphasis on the principle of operation, the types of sensors, and correlation processes in use. The optimization of the sensors for terrain referenced navigation is discussed, and terrain referenced navigation is compared with the Global Positioning System (GPS). It is noted that applications of terrain referenced navigation in conjunction with the database are perhaps more important than the improved navigation accuracy. How each of these applications is implemented and the hardware implications are detailed. The three-dimensional accurate position and the database can be used for other functions such as terrain following and intelligent ground proximity warning. >

Method and apparatus for aircraft navigation

Abstract: An aircraft navigation system is disclosed for use in missions involving unfamiliar terrain and/or terrain having hostile forces. The navigation system includes an inertial navigation system, a map of the terrain with elevational information stored in a digitized format as function of location, a typical energy managed or narrow (radar or laser) beam altimeter, a display system and a central processing unit for processing data according to preselected programs. The data processing system includes an operational mode (software program) for relating the continuing sequence of altimeter readings with the paths on the digitized map. In this manner, the true position of the aircraft (20) can be determined with respect to the digitized map (24) and can be displayed on a plan view of the map. When the correct position of the aircraft with respect to the digitized map is known, a display of the map and the aircraft can provide presentations useful to the navigation of the aircraft.

The use of INS/GPS in a highway survey system

Abstract: The integration of an inertial navigation system (INS) and Global Positioning System (GPS) receivers in differential mode is investigated for application to highway survey systems. A mobile highway inventory system (MHIS) operated by Alberta Transportation is used as a first step in the realization of an all-purpose kinematic survey system. MHIS requirements of approximately 0.5 m in position, 10 cm-s/sup -1/ in velocity, 0.5% in slope, and 0.2 degrees in curvature appear obtainable with the integrated system. If these requirements can be surpassed, INS/GPS can be used for road surveys, possibly replacing conventional survey techniques. The authors briefly describe the MHIS and outline the benefits of using INS/GPS for accurate and reliable geometric data collection. They outline the mathematical models for INS/GPS integration. Road tests performed using INS/GPS over a well-controlled traverse are discussed, and results are given. >

GG1308 ring laser gyro inertial measurement systems: Honeywell's low-cost solution for tactical applications

Abstract: The GG1308 ring laser gyro (RLG) inertial measurement systems represent the smallest-volume, lightest-weight, and lowest-cost RLG systems. These systems are designed to provide the functions required for inertial guidance, aided or midcourse navigation, and vehicle stabilization and control to a wide variety of tactical missiles, standoff weapons, unmanned aerial vehicles, torpedoes, and manned rotorcraft. GG1308 inertial systems achieve their low cost as a result of several significant development thrusts. Low-cost inertial sensors must be utilized. The GG1308 RLG is a true design-to-cost device with producibility and the cost of parts, materials, assembly labor, and manufacturing automation being the dominant design drivers. Additionally, these GG1308 inertial systems use a commonality design approach. This philosophy has made it possible to develop several generic hardware elements which need only be repackaged to provide an inertial system in the form factor required for specific programs. It also provides the system with an adaptability and intelligence to improve its performance throughout its useful life by making software improvements which do not affect the hardware design or production process. >

Vision-aided inertial navigation

Abstract: A technique of removing inertial-odometer drift errors by identifying landmarks along the vehicle's route is presented. Landmark identification is performed with the use of laser range data. The scenario being developed consists of a ground vehicle equipped for autonomous retrace of a path that was stored while the vehicle was being remotely piloted to its destination. On the outbound portion of the vehicle's journey, objects are detected with the laser range imagery, tracked from frame to frame, and recorded as landmarks if they meet the requirements of the landmark model. During the retrace phase, inertial-odometer data are used to guide the vehicle along the outbound path (in reverse). The landmarks recorded on the outbound path are again located during retrace, and their locations serve to remove any positional error that has occurred. This technique of vision-aided inertial navigation is presented along with processed laser range data. >

Integrated inertial navigation system/Global Positioning System (INS/GPS) for manned return vehicle autoland application

Abstract: It is noted that with the development of the International Space Station Freedom, people will permanently live in space and require routine access and an assured crew return capability in case of emergencies in space. The extended duration in space requires a manned return vehicle that is less demanding on the crew and provides an autonomous deorbit, entry, and autoland capability. The authors discuss an autoland capability with an integrated differential GPS/INS that provides the required position and velocity accuracies without the need for tactical aircraft navigation (TACAN) and microwave landing system (MLS) navigation aides. Simulation results are used to demonstrate the feasibility of autoland using differential GPS aided with a high-precision altimeter. This concept applies to several manned space applications, such as Assured Crew Return Vehicle (ACRV), Assured Shuttle Availability (ASA), Advanced Manned Launch System (AMLS), and National Aerospace Plane (NASP), and to unmanned return vehicles such as the Propulsion Avionics Module (P/AM). >

Ring laser gyro applications for tactical missiles: the Army TACMS solution

Abstract: The Honeywell H700-3A ring laser gyro missile guidance set (AN/DJW-51) provides navigation, guidance, autopilot, weapons dispensing, and communications functions for the US Army TACMS missile in a low-initial-cost and low-life-cycle-cost package. It is primarily the use of low-cost inertial sensors which make the use of a ring laser gyro navigation system feasible in the tactical missile market. The H700-3A ring laser gyro missile guidance set has proven to be a low-cost, high-accuracy guidance and navigation system for the deep-strike Army missile weapons system. This has been borne out by a highly successful test program of 26 missile flights. The components of the missile guidance set are described in detail. >

A unified approach to inertial navigation system error modeling

Abstract: Several inertial navigation system error models have been developed and used in the literature. Most of the models are ad hoc models which were needed to solve certain particular problems and were developed for that purpose only. Consequently, the relationship, correspondence, and equivalence between the various models is not evident. This paper presents a new methodology for developing inertial navigation systems error models which also puts all of the known models in the same framework and shows the equivalence between them. The new methodology is based on several choices the developer has to make which uniquely define the error model. This new approach enables the development of all existing models in a unified way, hence the equivalence and correspondence between them is obvious. Moreover, any new model which is of interest can be developed using the methodology presented in this work. In fact, any new model which will ever be developed for the class of systems considered here will fit into the framework described in this paper.