Showing papers on "Inertial navigation system published in 1968"
TL;DR: In this article, a high quality inertial navigation platform was used by the Meteorological Research Flight in order to measure vertical gust velocities and horizontal wind shear from a Canberra PR 3 aircraft.
Abstract: A high quality inertial navigation platform, originally developed for the TSR 2 aircraft, is now being used by the Meteorological Research Flight in order to measure vertical gust velocities and horizontal wind shear from a Canberra PR 3 aircraft. The equations are derived from which the vertical and horizontal winds are calculated, and an assessment is made of the accuracy of measurement which can be expected for vertical gusts and horizontal shear. Measurements of the residual error velocities which occur when the aircraft is made to pitch, roll and yaw are shown to lie within the theoretical limits, and an example of the velocities derived from a straight and level run in smooth air is also described. The use of this equipment to measure the small-scale variations in wind shear and vertical gusting when the aircraft descends through a layer of turbulence is then described, and the results of one of the first of a series of such flights are given. With the present recording system, the extracti...
92 citations
TL;DR: In this paper, the authors derived and evaluated algorithms for error analysis, large and small scale sensitivity of optimum filtering and fixed interval smoothing solutions to linear estimation problems, as well as ignorance of plant and measurement noise covariance matrices are considered.
Abstract: This paper presents the derivation and evaluation of algorithms for error analysis, large and small scale sensitivity of optimum filtering and fixed interval smoothing solutions to linear estimation problems. Model errors as well as ignorance of plant and measurement noise covariance matrices are considered. Results are presented for a simple scalar problem and for the problem of state estimation in an inertial navigation system operating in the free inertial mode.
58 citations
TL;DR: In this article, the authors derived differential error equations for the navigation errors of a local level undamped pure inertial platform that continuously rotates in azimuth, and derived the time response equations for vector position error produced by a constant level gyro drift error, as a function of platform rotation rate.
Abstract: Differential error equations are derived for the navigation errors of a local level undamped pure inertial platform that continuously rotates in azimuth. From these, the time response equations for the vector position error produced by a constant level gyro drift error, as a function of platform rotation rate, are computed and evaluated. It is shown that platform rotation attenuates the system position error due to level gyro bias and that this attenuation is a nonlinear function of rotation rate.
38 citations
31 Jul 1968
TL;DR: Aircraft navigation aids and flight control equipment, discussing inertial navigators with digital computers and navigation satellites.
Abstract: Aircraft navigation aids and flight control equipment, discussing inertial navigators with digital computers and navigation satellites
35 citations
33 citations
TL;DR: In this article, the estimation problem is modeled as a linear smoothing problem and the appropriate error covariances are found using the known techniques of optimal linear estimation theory, Kalman filtering and smoothing, both at and between the grid points.
Abstract: Deflections of the vertical introduce errors into terrestrial inertial navigation systems. In many situations, these errors prove to be intolerable. However, if vertical deflection data are available prior to a mission, this information can in principle be used to reduce the navigation system errors. It is assumed that measurements of vertical deflections plus noise are available at equally spaced points on a square grid. The accuracy to which the Schuler loop errors can be controlled, given this set of measurements, is bounded by the accuracy to which the uncontrolled Schuler loop errors can be estimated given the same set of measurements. Thus lower bounds on the accuracy of the compensated system may be established by obtaining the optimal error covariances of the equivalent estimation problem. It is shown that the estimation problem can be modeled as a linear smoothing problem if the vehicle travels at a constant heading and at a constant velocity. The appropriate error covariances are found using the known techniques of optimal linear estimation theory, Kalman filtering and smoothing, both at and between the grid points.
22 citations
01 Aug 1968
TL;DR: This tutorial report is to allow the reader with a limited background in optimum estimation techniques and/or inertial system theory to achieve a level of competence which will permit his participation in the design and evaluation of aided inertial guidance systems.
Abstract: : The purpose of this tutorial report is to allow the reader with a limited background in optimum estimation techniques and/or inertial system theory to achieve a level of competence which will permit his participation in the design and evaluation of aided inertial guidance systems. To this end, the Kalman filter is described in some detail, with full use made of intuitive concepts. Next, the theory of inertial navigation is presented. Based on an understanding of inertial systems and the Kalman filter, the reader is then shown how the two are combined to provide accurate, aided inertial systems. Problems arising in the application of the Kalman filter to practical situations are discussed and common methods for solving them are illustrated. Examples in inertial navigation, gyrocompassing, and alignment transfer are provided in support of the theoretical development.
8 citations
Patent•
26 Sep 1968
TL;DR: In this article, the authors describe a system in which a dead-reckoning computer is used to resolve the outputs of SPEED and head-finding of parallel positions.
Abstract: INERTIAL NAVIGATION SYSTEMS IN WHICH BASIC POSITION DATA IS SUPPLIED TO A POSITION DISPLAY DEVICE FROM A DEAD RECKONING COMPUTER THAT RESOLVES THE OUTPUTS OF SPEED AND HEADING DETECTING APPARATUS INTO COORDINATE POSITION SIGNALS. MECHANICAL AND ELECTRICAL INTEGRATOR SYSTEMS ARE UTILIZED AS THE BASIC DEAD RECKONING COMPUTERS. IN THE PREFERRED CONSTRUCTIONS, THE DEAD RECKONING COMPUTER IS CONTINUOUSLY UP-DATED, IN ACCORDANCE WITH THE OUTPUT FROM A RADIO NAVIGATION RECEIVER MEANS, TO CORRECT THE OPERATION OF THE COMPUTER TO A RATE COMMERSATURE WITH THE MAXIMUM OVERALL DRIFT RATE OF THE SENSING DEVICES AND THE COMPUTER.
5 citations
TL;DR: The Kalman optimum linear filter is found to apply to the navigation problem if some technique is used to account for possible non-Gaussian maneuver accelerations, and two methods are suggested which greatly reduce the amount of computation with a minimum degradation in the performance of the system.
Abstract: Although navigation systems have generally been developed by solving exactly the dynamic equations of motion, in reality the navigation problem is a statistical one since there are unpredictable errors in the measurements. The advent of very powerful navigation computers makes it possible by using statistical filtering techniques to retrieve more of the information contained in the navigation measurements. The navigation system is thus developed here as an information-filtering problem rather than a simulation of a deterministic physical system. The Kalman optimum linear filter is found to apply to the navigation problem if some technique is used to account for possible non-Gaussian maneuver accelerations. A major problem in the application of statistical techniques is the tremendous amount of computation required. Two methods are suggested which greatly reduce the amount of computation with a minimum degradation in the performance of the system. In one method, physical considerations are used to divide the total filter into smaller, simpler filters. In the other method, the optimum gains are precomputed and approximated by simple functions in the flight computer. The details are given for the alignment and calibration of an inertial platform using statistical filtering.
5 citations
12 Aug 1968
01 Jan 1968
TL;DR: Nonorthogonal multisensor strapdown inertial reference unit providing redundant capabilities and optimal performance as mentioned in this paper, which can be used for both inertial and nonorthogonality.
Abstract: Nonorthogonal multisensor strapdown inertial reference unit providing redundant capabilities and optimal performance
Patent•
29 Nov 1968TL;DR: In this paper, a Doppler processor system including an inertial guidance platform and a coherent radar having an azimuthally scanning antenna, the scan rate of which is substantially constant over all portions of the scan region, computing means for computing the on-boresight doppler velocity Vfd and the time rate of change of the doppling velocity V fd whereby the use of function potentiometers mounted on the radar antenna gimbal system is avoided, and increased utilization is made of an onboard computer.
Abstract: In a doppler processor system including an inertial guidance platform and a coherent radar having an azimuthally scanning antenna, the scan rate of which is substantially constant over all portions of the scan region, computing means for computing the on-boresight doppler velocity Vfd and the time rate of change of the doppler velocity V fd whereby the use of function potentiometers mounted on the radar antenna gimbal system is avoided, and increased utilization is made of an onboard computer. Direction matrix conversion computing means, responsive to said radar and to said inertial platform, provides a first and second output corresponding to a respective one of a preselected derivative of the doppler velocity and the product sEANVzRAD, where: SEAN sine of the antenna elevation angle VzRAD platform velocity resolved in the coordinates of the radar system. A first analog integrator responsive to said first output of the computing means provides a signal indicative of V fd; and signal combining means having a first and second input, responsive to a respective one of said second output of the computing means and to the double integral with respect to time of the first output of the computing means, provides a signal indicative of Vfd.
01 Aug 1968
TL;DR: In this article, single degree of freedom integrating gyro in strapdown inertial systems, discussing error reduction is discussed, and the authors discuss error reduction in the inertial system.
Abstract: Single degree of freedom integrating gyro in strapdown inertial systems, discussing error reduction
01 Jul 1968
Patent•
05 Dec 1968TL;DR: In this paper, the vertical accelerometer of a ship is first counted and scaled to provide an output related directly to the total acceleration, and the resultant output is passed through a filter that corresponds to a particular weighting function (heavily weighted for the middle time) to remove the factor of ships heave acceleration.
Abstract: The output of the vertical accelerometer of a ships inertial navigation sem (SINS), in pulse form, is first counted and scaled to provide an output related directly to the total acceleration. The SINS computer provides the latitude, and north and east velocities of the ship, which are then converted into the theoretical gravity and the Coriolis error. These two factors are subtracted from the total scaled acceleration, and the resultant output is passed through a filter that corresponds to a particular weighting function (heavily weighted for the middle time) to remove the factor of ships heave acceleration. The final output is the free-air gravity anomaly in terms of real time.
01 Sep 1968
TL;DR: A set of computer programs has been developed that provides a way of evaluating optimum and sub-optimum Kalman estimation techniques and has been described in a statistical manner, in order to specify the random noise quantitatively as a function of time.
Abstract: : This report develops a method for analyzing the errors incurred in optimum estimation schemes. The optimum control law for modern control systems is usually a function of all the states of the system. In many practical cases it is necessary to extract information concerning the states from the measurement of the output. This extraction process is called estimation. Due to random measurement noise and the random noise components of the states of the system, the estimate of the states is not perfect. A set of computer programs has been developed that provides a way of evaluating optimum and sub-optimum Kalman estimation techniques. The random noise processes have been described in a statistical manner, in order to specify the random noise quantitatively as a function of time.
01 Aug 1968
TL;DR: Strapdown inertial navigator alignment and calibration in swaying launch vehicle on pad, using optimal recursive linear filter as mentioned in this paper was used to align the inertial navigation system with the launch vehicle.
Abstract: Strapdown inertial navigator alignment and calibration in swaying launch vehicle on pad, using optimal recursive linear filter
01 Jan 1968
TL;DR: Apollo gyro reliability covering guidance, navigation and control systems, stressing failure mode prediction is stressed.
Abstract: Apollo gyro reliability covering guidance, navigation and control systems, stressing failure mode prediction
01 Mar 1968
TL;DR: A computing algorithm for the fixed-base self-alignment of a gimballess inertial navigation system is derived by the application of linear estimation theory and results indicate that the initial direction cosine matrix can be aligned in 20 seconds.
Abstract: : A computing algorithm for the fixed-base self-alignment of a gimballess inertial navigation system is derived by the application of linear estimation theory. Simulation results indicate that the initial direction cosine matrix can be aligned in 20 seconds with not more than 10 arcseconds of error in azimuth or level. (Author)
TL;DR: In this article, a minimal-time controller was proposed for the Boeing 2707 SST that utilizes information derived from the ILS receiver and an on-board inertial navigation system.
Abstract: Precise measures of position and velocity of an aircraft have important applications during the landing phase. Such measures can be obtained, in directions, normal to an instrument landing system (ILS) reference path, by suitably tying together an inertial navigation system and an instrument landing system. Operations performed on the difference between ILS position and inertially-measured position yield corrections to the inertially-measured position and velocity.
An important facet of the fully automatic landing problem is the acquisition of the ILS localizer course. A considerable improvement in performance, compared with that of a conventional system, may be realized during this phase by applying optimal control theory with a minimal time-to-acquisition criterion. The second part of this paper presents a practicable realization of a minimal-time controller which utilizes information derived from the ILS receiver and an on-board inertial navigation system. Solution characteristics are presented for the Boeing 2707 SST.
01 Aug 1968
01 Mar 1968
01 Jan 1968
01 Aug 1968
TL;DR: Precision tilt and rotational isolation system design for inertial navigation sensor testing and a comparison study showed good results in terms of precision and efficiency.
Abstract: Precision tilt and rotational isolation system design for inertial navigation sensor testing
TL;DR: In this paper, the authors discuss spectrum occupancy, satellite power, lane ambiguities and computational procedures for a navigation satellite system designed for ATC without requirement for onboard transmitter, discussing spectrum occupancy and satellite power.
Abstract: Navigation satellites system designed for ATC without requirement for onboard transmitter, discussing spectrum occupancy, satellite power, lane ambiguities and computational procedures
Dissertation•
01 Jun 1968TL;DR: In this article, the authors present a model for the development of an unmanned aerial vehicle (UAV) based on the idea of the MIMO-V. M.S. Thesis.
Abstract: Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics. Thesis. 1968. M.S.