Showing papers on "Inertial reference unit published in 1990"

Airdata calibration of a high-performance aircraft for measuring atmospheric wind profiles

Abstract: The research airdata system of an instrumented F-104 aircraft has been calibrated to measure winds aloft in support of the space shuttle wind measurement investigation at the National Aeronautics and Space Administration Ames Research Center Dryden Flight Research Facility. For this investigation, wind measurement accuracies comparable to those obtained from Jimsphere balloons were desired. This required an airdata calibration more accurate than needed for most aircraft research programs. The F-104 aircraft was equipped with a research pilot-static noseboom with integral angle-of-attack and flank angle-of-attack vanes and a ring-laser-gyro inertial reference unit. Tower fly-bys and radar acceleration-decelerations were used to calibrate Mach number and total temperature. Angle of attack and angle of sideslip were calibrated with a trajectory reconstruction technique using a multiple-state linear Kalman filter. The F-104 aircraft and instrumentation configuration, flight test maneuvers, data corrections, calibration techniques, and resulting calibrations and data repeatability are presented. Recommendations for future airdata systems on aircraft used to measure winds aloft are also given.

Measurement and control system for scanning sensors

Abstract: A sensor may be scanned relative to any arbitrarily selected reference coordinate system by the use of a system including an attitude determination unit, attitude control unit, inertial measurement unit, navigation unit, and a scan generation unit Methods are also employed, in this system, for reducing errors and increasing the accuracy of the scan of the sensor These methods include the use of gyroscopes having no cross axis coupling or inherent limit on their angular speed, a Kalman filter to reduce system errors, continually estimating solutions to the strapdown equation, and a dual loop control system utilizing both rate and position signals which issues motion control commands to the sensor

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.

Inertial stabilizing system.

Abstract: The present invention comprises an inertial stabilizing system to be used preferably in connection with image stabilizing of hand-held optical instruments. An ultralight oscillogyro (1-6) serves as a reference element by which the angular position in inertial space is detected. An electromechanical control system causes a gimbaled part (19) of the optics to assume essentially the same angular position in space assumed by the rotation plane of the rotor of the oscillogyro. The oscillogyro is modified for a widened angular range and the damping of the gyro is utilized for obtaining directly the possibility of target tracking.

Utilization of fiber optic gyros in inertial measurement units

Abstract: Fiber optic gyro technology has been developed to a point where these gyros are now being introduced into advanced engineering models of the next generation of inertial measurement units (IMUs). This paper covers the operating principles of the interferometric type of fiber optic gyroscopes, together with a brief comparison against ring-laser gyroscopes. Recent flight test data of an IMU employing fiber optic gyro sensors are presented. Finally, the unique characteristics of the fiber optic gyro are discussed, with particular emphasis on the role they will play in future fault-tolerant IMUs.

Application of inertial instruments for DSN antenna pointing and tracking

Abstract: The feasibility of using inertial instruments to determine the pointing attitude of the NASA Deep Space Network antennas is examined. The objective is to obtain 1 mdeg pointing knowledge in both blind pointing and tracking modes to facilitate operation of the Deep Space Network 70 m antennas at 32 GHz. A measurement system employing accelerometers, an inclinometer, and optical gyroscopes is proposed. The initial pointing attitude is established by determining the direction of the local gravity vector using the accelerometers and the inclinometer, and the Earth's spin axis using the gyroscopes. Pointing during long-term tracking is maintained by integrating the gyroscope rates and augmenting these measurements with knowledge of the local gravity vector. A minimum-variance estimator is used to combine measurements to obtain the antenna pointing attitude. A key feature of the algorithm is its ability to recalibrate accelerometer parameters during operation. A survey of available inertial instrument technologies is also given.

GPS solves the air combat training program

Abstract: It is shown that, by adopting today's GPS (Global Positioning System) tracking techniques for air combat training ranges, the expanded modern training requirements can be satisfied in a cost-effective manner. These requirements consist of keeping track of the precise position of up to 100 aircraft over an area of up to 25000 square miles at altitudes from ground level to 100000 ft. In addition, it is desirable to accomplish this instrumentation with a few portable groundsites and still obtain high position accuracy of all the players. It is pointed out that the existing instrumentation pods developed by the US Air Force on the Range Applications Program come very close to solving the instrumentation requirement in their present form. They contain a sophisticated datalink, a GPS receiver, and an inertial reference unit. The only unit missing is the air data sensing system, which could be added easily in the existing pod. >

Attitude and orbit control subsystem for ers-1 and its subsystem test

Abstract: This paper presents the design and EM Subsystem test of Attitude and Orbit Control Subsystem (AOCS) for Earth Resources Satellite-1 (ERS-1). Fine attitude control is required in the mission operation phase of the satellite. In this phase the AOCS adopts 3-axis strapdown attitude determination and zero momentum system using 4 skewed reaction wheels. The control law is calculated by On-Board Computer in Attitude and Orbit Control Electronics (AOCE). In the subsystem test, Dynamic Closed Loop Test (DCLT) has been performed by using all real hardware components. Earth sensor and sun sensors were attached on the servo-tables in DCLT, and two different test methods were adopted for Inertial Reference Unit (IRU). One of them was conventional method in which IRU was attached on servo-table, and the other one was the torquing-loop method which used bias current in the IRU gyro rebalance loop. The results of DCLT are as follows: - Torquing-loop method is very useful for ERS-1 AOCS. - AOCS EM has acceptable performances that attitude error is 0.11deg max. and stability is 0.0014deg/sec max.

Integrated Inertial/gps

Abstract: The presence of failures in navigation sensors can cause the determination of an erroneous aircraft state estimate, which includes position, attitude, and their derivatives. Aircraft flight control systems rely on sensor inputs to determine the aircraft state. In the case of integrated Inertial/NAVSTAR Global Positioning System (GPS), sensor failures could occur in the on-board inertial sensors or in the GPS measurements. The synergistic use of both GPS and the Inertial Navigation System (INS) allows for highly reliable fault detection and isolation of sensor failures. Integrated Inertial/GPS is a promising technology for the High Speed Civil Transport (HSCT) and the return and landing of a manned space vehicle.