Showing papers on "Inertial measurement unit published in 1977"

Evaluating Sensor Orientations for Navigation Performance and Failure Detection

Abstract: A study of the constraints imposed by the choice of particular orientations of redundant inertial sensors upon navigation system performance and the detection and identification of sensor failures in fault-tolerant inertial measurement units is presented. Figures of merit are derived for systematically evaluating alternative sensor orientations. The volume of the ellipsoid associated with the covariance matrix of estimation errors is used to rank sensor orientations in terms of navigation performance. Distance measures commonly used in hypothesis testing are used to rank sensor orientations in terms of the detectability of sensor failures. The application of these results is illustrated for configurations of four 2-degree-of-freedom gyroscopes.

Airborne surveying apparatus and method

Abstract: A method and apparatus for surveying ground terrain from an airborne vehicle is disclosed. According to the method and apparatus, an inertial measurement unit, a position tracking device, and a terrain altimeter are carried by the airborne vehicle in a known vector relationship to one another. The inertial measurement unit provides continuous accelerometer data from which a first determination of vehicle position can be made. Simultaneously, data from the tracking device representative of the position of the tracking device relative to cooperating reflection means on the ground, if within sight of the airborne vehicle, provides, in combination with gimbal angle sensor outputs from the inertial measurement unit, an independent determination of the position of the vehicle. The two position measurements, when available, are continuously compared in real time on board the vehicle and error corrections are generated therefrom by estimation theory. The generated error corrections are stored and updated in real time and error correction signals are preferably provided to at least the inertial measurement unit to correct errors due, for example, to drift in the unit. The airborne vehicle can thereby be out of sight of the cooperating reflection means for substantial time durations without substantially degrading the accuracy of the position information. Corrected positional information, which includes the generated error corrections, and the correlated output of the terrain altimeter are stored to provide a profile of the region over which the vehicle flies. In preferred embodiments of the invention, both the position tracking device and the terrain altimeter are laser devices.

History of Inertial Navigation

Abstract: the guidance system used by the Germans in 1942 in the V–2 missile can be considered to be the first use of inertial navigation. It is true that Foucault defined the gyroscope in 1852 and that Schuler developed the gyrocompass in 1908, but the former device was only a measuring instrument and the latter, although of inertial quality, was only a partial inertial system. The Sperry flight instruments of the late 1920's and early 1930's were attitude–indicating not velocity or position-indicating devices. Earnest development of inertial navigation systems began in the United States in the late 1940's and early 1950's by the M.I.T. Instrumentation Laboratory, Northrop and Autonetics under Air Force sponsorship. This work led to the inertial guidance systems for ballistic missiles—both land and ship launched. The 1960's brought the Space Age and the advance of inertial guidance in Apollo. During this time inertial guidance systems also found their way into military and then commercial airplanes. Behind the system development was the simultaneous and necessary development of theory, analysis, components, subsystems and testing. The author, whose professional career has been simultaneous with the growth of inertial navigation, draws on his personal experiences in the field of direct association with many of the people and events involved.

Apparatus for computing the rate of change of energy of an aircraft

Abstract: A rate of change of energy computer utilizing signal processing of the inner vectorial product of inertial acceleration and inertial velocity wherein such parameters are derived utilizing outputs from the aircraft INS (inertial navigation system) and from body mounted accelerometers.

The History of Inertial Navigation

Abstract: Practical inertial navigation is a quite recent achievement, only twenty-five years for serious research and development and only five for its commercial use. However, one might possibly say that a partial understanding of some of its principles is much more ancient. For example, in the Bible1 we read that God used a plumb-line to identify a particular location!

Design, Development, Analysis, and Laboratory Test Results of a Kalman Filter System-Level IMU Calibration Technique

Abstract: : The United States Air Force Avionics Laboratory at Wright-Patterson Air Force Base, Ohio, is presently conducting inhouse advanced aided-inertial navigation software development programs. This report describes the design, development, analysis, and laboratory test results of an IMU calibration and error model development methodology formulated to support the design and test of inertial navigation software and associated Kalman Filters. The IMU error analysis methodology incorporates a 68-state Kalman Filter and uses only system- level IMU velocity and gimbal angle measurements taken during a two and a half hour, twelve-platform attitude test to estimate IMU significant error sources relative to the inertial instrument random disturbances. The Kalman Filter incorporates a number of error model residual states which provide a measure of the degree to which the test article conforms to the assumed IMU error model. IMU error parameter estimation can be accomplished either on-line in real time or off-line using recorded IMU measurements. Results obtained from both a CDC- 6600 computer simulation of the IMU calibration problem and a laboratory development program indicate that the technique is conceptually more comprehensive and accurate, and requires less specialized test equipment and test time than conventional calibration methods. The technique appears to be a likely candidate for IMU acceptance and intermediate and depot level maintenance tests.

Development of the German A-4 guidance and control system, 1939 - 1945: A memoir

Abstract: The development by 1943 of a fully inertial navigational system for the German A-4 (V-2) missile is detailed. This flight control system used a triple-axis stabilized platform with two longitudinal accelerometers and one lateral accelerometer.

Performances and Characteristics of Floated Pendulum Accelerometers with a Passive Magnetic Suspensions

Abstract: Single Degree of Freedom Floated Pendulum Accelerometers with a three-axis passive magnetic : suspensions applied to the output axes had been developed at NAL in order to develop more precise inertial sensors such as floated gyros and floated accelerometers which will be used in the inertial navigation system. The design and the performances within ±1G region of the above accelerometers were described in the third report. This study is precise measurement of the performances of the accelerometers (MSA-1, MSA-2) in high static acceleration region (±12 G) and of the frequency response of the MSA-1. The magnetic suspension rotor core of the MSA-1 is made of ferrite, and that of the MSA-2 is laminated supermaloi. The main results obtained are as follows.(1) The performances of the accelerometers in the acceleration region are ; non-linearity coefficient 7 × 10-5 G/G2 (MSA-1), 7 × 10-4 G/G2 (MSA-2), short term repeatability ±4 × 10-4 G (MSA-2).(2) The magnetic suspensions can be acted normally in high static accelerationdisturbance (±15 G), and the optimum material of the suspension rotor core is ferrite which has such properties as high permeability, high saturation of magnetic flux density, minimum eddy current loss, etc.(3) The frequency response of the MSA-1 obtained is about 17 Hz when the accelerometer is adjusted to the optimum dynamic condition.

Development of Capability for Multifunction Integrated Reference Assembly Evaluation.

Abstract: : The significance of this research and development to the Air Force is the development of the tools and techniques required to assess the feasibility of using a minimum number of inertial sensors to provide the inertial reference information consistent with aircraft requirements for weapon delivery, flight control, navigation, fire control, and flight safety. Multifunction Inertial Reference Assembly (MIRA) is the term which describes the generic class of systems designed to meet this objective. Emphasis is placed on the development of a simulation capability for the evaluation of MIRA systems in realistic environments. A definition of the aircraft and flight-control system selected for the simulation is included along with a consideration of the inertial-sensor requirements for MIRA systems. Results demonstrating the capability of the simulation are presented. The life-cycle-cost implications of the MIRA approach are also dealt with. (Author)

Flight test results of the Strapdown hexad Inertial Reference Unit (SIRU). Volume 1: Flight test summary

Abstract: Flight test results of the strapdown inertial reference unit (SIRU) navigation system are presented. The fault-tolerant SIRU navigation system features a redundant inertial sensor unit and dual computers. System software provides for detection and isolation of inertial sensor failures and continued operation in the event of failures. Flight test results include assessments of the system's navigational performance and fault tolerance.

Flight-control/navigation inertial reference system

Abstract: The preliminary design of a redundant strapdown navigation system for integrated flight-control/navigation use has been completed. Based on application of tuned-gimbal gyros, a compact configuration (13 in x 13 in x 14 in) has been achieved for fail-operational/fail-operational redundancy. Test data are presented for strapdown system test programs including flight testing of the LN-50 tuned-gimbal gyro system. Testing of a redundant sensor configuration is currently in process. Strapdown gyro development also includes ring laser and nuclear magnetic resonance techniques.

Functional Requirements of the Interface Between the NAVSTAR GPS Receiver Model X and the Advanced Inertial Reference Sphere. Volume II.

Abstract: : The performance requirements for the GPS X-set impose difficult and conflicting design problems on the receiver. To accurately track the incoming signals in a high-dynamics environment, a wide-bandwidth tracking loop is required with a high-order tracking network. For best performance in the presence of noise, on the other hand, a narrow bandwidth tracking loop is desired. Techniques for utilizing an Inertial Measurement Unit (IMU), such as the Advanced Inertial Reference Sphere (AIRS), to aid the receiver tracking loops are studied. The IMU can provide accurate information on translational accelerations and orientation changes experienced by the receiver. By properly using the IMU data, the receiver bandwidth can be reduced without increasing the dynamics-induced tracking error. The end result is an improvement in performance in noisy or jamming situations.