Showing papers on "Inertial navigation system published in 1969"

Electronic celestial navigation means

Abstract: An automatic navigation and guidance system for use in moving vehicles such as air or sea craft, and more particularly a navigation system utilizing a single automatic star or satellite tracker through which a continuous indication of the longitude and latitude of the moving vehicle may be provided to an automatic guidance system, automatic star selection being provided, the described celestial navigation device providing continuous, accurate monitoring of a further inertial navigation device during normal operation, the further inertial navigation device providing continuous navigation and orientation during interruptions of the celestial navigation device.

Experimental strapdown redundant sensor inertial navigation system

Abstract: Strapdown redundant experimental sensor inertial navigation package containing gyros and accelerometers, discussing signal real time processing by digital computer

System and method for aligning an inertial navigation system

Abstract: A system and a method of aligning an inertial navigation system providing signals corresponding to azimuth movement of a vehicle moving in a known azimuth. The azimuth movement signals are compared with a signal corresponding to the known azimuth to provide a difference signal for correcting the azimuth movement signals accordingly.

Aircraft strike assurance system

Abstract: A system for computing all necessary flight commands for successfully completing a mission, including a forecast of fuel reserves and time to each target from planned parameters by combining fuel management data and inertial navigation data. The system provides for primary and alternate targets and is adaptable to inflight mission alterations and unforeseen events such as weather changes and engine failure.

Optimum Integration of Aircraft Navigation Systems

Abstract: A current problem in aircraft navigation is determining how to effect alow cost navigation system consistent with required mission operationswhich will render a high degree of accuracy and reliability. One wayto achieve this is through optimum integration of equipment,subsystems, and computer mechanizations. Consistent with this approach,the overall objectives of this paper are to show the advantages of anoptimally integrated aircraft navigation system, and to illustrate howto effect a low cost navigation system with high accuracy performance.An integrated aircraft navigation system employing a Kalman optimumestimation filter is configured and analyzed in detail. The results ofthe analysis clearly indicate how to achieve high accuracy performanceusing low cost subsystems; namely, via optimum systems integration.

An Optimum Inertial/Doppler‐Satellite Navigation System

Abstract: It is obvious that position fixes obtained from the Navy Navigation Satellite System may be used to reset a pure inertial system on long missions where some form of resetting is desirable. This paper discusses a method of system integration whereby the doppler data is treated directly as the observable in a Kalman-filter reset scheme, and thus the intermediate step of computing a position fix is omitted. In the process, this method properly accounts for the vehicle velocity in any dynamical situation, which is a difficult problem when viewed from other approaches. Simulated computer results are presented.

Automatic pilot for navigable craft

Abstract: An automatic pilot for navigable craft in which the drift angle of the craft derived from an inertial navigation system is used to cancel the course heading error in the presence of wind to provide the beam damping function required to achieve asymptotic capture and tight on-course control without overshoot or stand off in the presence of crosswind and/or wind shear.

Hybrid navigation system

Abstract: A hybrid navigation system including an inertial navigation system on a vehicle to be located and a time base signal generator and a receiver on the vehicle. The receiver is coupled to the generator and adapted to receive incoming location signals transmitted from remote stations. Phase differences are determined between the location signals and reference signals generated by the generator. A computer computes on the basis of an error formula and from data received from the inertial navigation system, the reference signals and the phase differences, a correction of position issuing from the inertial system and a corrected position. The computer also computes, from the corrected position, values of the phases of the reference signals corresponding to those which would have been received if the corrected position were true. The time base means is responsive to said values and controls the receiver, computer and determination of phase differences. The computer computes from the phase differences and position values updated values of the parameters of the error formula.

Two-resolver, strapped-down inertial reference system

Abstract: The strapped-down reference system attains the equivalence of a three- and four-gimbal, inertial reference system by using a forward resolver chain, which can be of relatively low accuracy, to derive gimbal angle values, and high-accuracy feedback resolvers to derive signals to cage the gyroscopes. The gyroscopes are caged by pulse torque techniques and integration of angular rates is performed in an essentially digital fashion by pulse generators and stepping motors.

Analysis and evaluation of a novel inertial navigation system

Abstract: sensors. The theory of the system mechanization is develop ed from first principles and methods for calculation of the system loop gains are presented. First, a single-axis system is considered and then the analysis is generalized to a three-axis system. The analyses performed indicate that error propagation for the novel system and the conven tional system are identical for identical error sources. It is also shown that the RAMP base motion isolation syste provides a better gyro environment than that used in a con ventional system since the level gyros are not required in the gimbal servo loops. Reports of flight tests of this system corroborate these conclusions. SUMMARY A novel inertial navigation system referred to in the literature as the RAMP inertial navigator is analyzed and then compared to a conventional local vertical navigation system. The main attraction of this system is that it is capable of indicating the vertical using only gyros as sensors, The theory of the system mechanization is developed from first principles and methods for calculation of the system loop gains are presented. First, a single-axis system is considered and then the analysis is generalized to a three-axis system. The analyses performed indicate that error propagation for the novel system and the conventional system are identical for identical error sources. It is also shown that the RAMP base motion isolation system provides a better gyro environment than that used in a conventional system since the level gyros are not required in the gimbal servo loops. Reports of flight tests of this system corroborate these conclusions. fulfillment of the requirements for the degree of Master of Science.

Manual Astronaut Navigation

Abstract: : The report presents selected methods, procedures, and equipment that form a basis for the development of a flexible manual space navigation system. These include a graphical method of eccentricity determination, geometric element determination by numerical differentiation of range measurements, differential correction of orbital elements, manual position fixing, orientation elements determination, improved optical ranging, and the possible uses of back- up inertial platforms, hand-held mechanical calculators, and hand-held, battery operated, computers. Numerical examples and error analyses are also presented.

Designing differentiating and integrating gyroscopes and accelerometers

Abstract: : The book covers the fundamentals of analysis and designing of differentiating and integrating gyroscopes and accelerometers and an analysis of their errors under different operating conditions is given. Simple calculation formulas for determination of the basic parameters of these instruments and also their instrumental and methodical errors are given. Depending upon the assignment of the instrument, requirements for static, dynamic, and accuracy characteristics are shown. Much attention is given description of the physical essence and causes of appearance of the examined errors. (Author)

Application of kalman filtering to baro/inertial height systems.

Abstract: : The report consists of a chapter written for a NATO-AGARDOGRAPH entitled 'Theory and Applications of Kalman Filtering'. The problems of traditional baro/inertial height units are discussed. A Kalman filter is proposed and results are given from a mathematical model of the system. (Author)

Schuler's principle and inertial navigation

Abstract: M. Schuler, distinguished member of the German gyrocompass school, and sometime gyrocompass engineer with the firm of Anschuetz-Kaempfe of Kiel, tried to adapt the properties of the center of percussion or oscillation of a compound pendulum to make of such a device an ideal artificial horizon for navigation. His idea was clear and simple. If the center of suspension is placed at rest at the center of a circle, and the center of oscillation is placed in and restrained to its circumference, then the pendulum is normal to the circumference, i.e., locally vertical true. If now the center of oscillation is moved in any manner in the circumference, this local true vertirnl at the center of oscillation will be preserved, according to well-known principles of dynamics originating with Newton’ and d’Alembert.? This statement remains true if the center of the circle is also the origin of a central force, e.g. attraction, acting on the center of mass of the pendulum. In applying this concept to the threedimensional case of the earth, however, Schuler quite neglected the fact that the center of curvature of a trajectory in the earth’s surface does not, in general, always coincide with the earth’s center. There can be, therefore, another central force with an erroneous origin which will disturb the local vertical attitude of the pendulum as its center of oscillation shifts about in the peripheral surface of the earth. He did not succeed in an attempted reduction to practice, nor, it seems, has there subsequently been such a reduction, although he did apply his idea successfully in a method of dealing with gyrocompass steaming error oscillations. He published a brief account in the German language of his thinking and practical work on such devices in 1923: and is the inventor of record on certain pertinent German patents! About 1950 some engineers working on inertial navigation in America were becoming aware of his work and his 1923 paper. The notion soon became popular in several navigation engineering circles that Schuler’s idea and the concept of inertial navigation were one and the same, especially with respect to the two artificial horizons involved.’ No En@ translation of Schuler’s 1923 paper appears to have been available before 1956, and only two‘?’ are known to the author to exist at this time, perhaps in very limited availability. Although the author has read them, he has not relied on these. For the passages quoted in German, he gives translations of his own, but he neither recommends nor places reliance in these translations, preferring to rest his case on Schuler’s German paper? In Schuler’s 1923 paper, if he failed quite correctly and rigorously to state his principle, to relate it to the principles and history of dynamics, to work out his illustrative examples, and to notice faults in his exposition, these are not errors chargeable to him. It seems his purpose may have been to suggest in a genial,

Airborne Gravimetry Program.

Abstract: : The report summarizes the studies and experimental work on airborne gravimetry systems. The analytical studies identify navigation and stabilization requirements, and present methods for reducing airborne gravimeter readings to gravity estimates, including special considerations involved with the use of a gyro accelerometer for the gravimeter. A survey of candidate gravimeters demonstrates the fairly wide choice available from accelerometers employed by inertial guidance systems. Development and test of an experimental system using a type 25 pendulous integrating gyro accelerometer are described, flight tests summarization and reduced data presented. Results of March, 1968 flights show a bias error of 6.2 milligals a standard deviation of 4.7 milligals for fourteen lines of data. Classified data are presented in a separate volume. (Author)

Positive ion measurement of spacecraft attitude - Gemini X and XII.

Abstract: A new method of measuring spacecraft pitch and yaw angles utilizing the properties of environmental positive ions is described. The technique requires that the spacecraft velocity be greater than the random thermal ion velocity. It is based on the fact that the current to a planar ion sensor is dependent on spacecraft attitude. For the measurement of pitch or yaw, two planar electrostatic analyzers are combined in an appropriate probe configuration. The theoretical foundations of the method are developed and the experiment described. The results of 45 hr of operation on Gemini flights X and XII are summarized. The ion attitude system is found to have a faster response time and lower weight and power consumption than the onboard inertial guidance system. Absolute comparison of pitch and yaw angles from inertial and ion measurements shows that the two methods agree within 1.5° in pitch and 2.0° in yaw. The dependence of the results on latitude, roll variations, and thruster firings is shown. Modifications of the ion system to meet other flight requirements and its incorporation into attitude control systems are outlined.

Design of Strapdown Gyroscopes for a Dynamic Environment Interim Scientific Report II

Abstract: Error analysis for single degree of freedom integrating gyro, and figure of merit relating gyro errors to orientation error of strapdown inertial reference system

Ground Testing of Inertial Navigators to Improve Dynamic Performance

Abstract: A ground testing method has been devised to evaluate the dynamic errors of an inertial navigation system. A trimmed stationary inertial system in the navigation mode can be subjected to programmed platform orm drift rates, and generate position outputs which are compared with those of a perfect navigator. The linearized error equations for this testing mode are derived and the resulting position error propagation is analyzed using Kalman filtering in order to identify the error sources. A simulated platform with a fixed set of error sources is analyzed to evaluate this testing concept. An example is presented to show that the gyro and accelerometer scale factor and misalignment error coefficients can be estimated.

On the Treatment of Inertial Measurement Unit Data in Optimal Linear Navigation Policies

Abstract: The inclusion of the integrated nongravitational acceleration outputs from an inertial measurement unit in an optimal linear navigation policy is treated. This formulation appears to be considerably different nt from the treatments of IMU data for space vehicle navigation that have previously been discussed and promises to yield considerably better results in many instances. It has the advantage that the data are processed in an optimal fashion that makes the best use of knowledge of the general system characteristics. Further, the IMU enters the formulation in the same manner as any other sensor and, therefore, provides a more uniform method of treatment. Two methods of dealing ng with the IMU are discussed and then applied to a simple example. The advantages of the second formulation are observed to be quite significant.

Error analysis of strapdown and local level inertial systems which compute in geographic coordinates

Abstract: Error analysis of strapdown and local level inertial navigation systems which compute in geographic coordinates

The Schuler pendulum and inertial navigation.

Abstract: Mr. Bell and Professor Stratton have in the October Journal shed interesting light on the nature of inertial navigation as applied to navigation around a planet. It is a pity that Mr. Bell has repeated that in such inertial systems vehicle position and velocity are deduced from measurement of acceleration. This idea is certainly misleading so far as understanding error propagation in these systems is concerned, if not actually wrong.

State transition matrix for inertial navigation systems

Abstract: Error equation for inertial navigation systems formulated and solved in state space notation

Strapdown navigation equations for geographic and tangent coordinate frames

Abstract: Navigation equations for geographic and tangent coordinate frames for radar strapdown inertial navigation

Direction cosine computational error

Abstract: Computer-generated computational errors in direction cosine matrix for strapdown inertial system