Showing papers on "Inertial reference unit published in 1995"

Inertial navigation systems for mobile robots

Abstract: A low-cost solid-state inertial navigation system (INS) for mobile robotics applications is described. Error models for the inertial sensors are generated and included in an extended Kalman filter (EKF) for estimating the position and orientation of a moving robot vehicle. Two different solid-state gyroscopes have been evaluated for estimating the orientation of the robot. Performance of the gyroscopes with error models is compared to the performance when the error models are excluded from the system. Similar error models have been developed for each axis of a solid-state triaxial accelerometer and for a conducting-bubble tilt sensor which may also be used as a low-cost accelerometer. An integrated inertial platform consisting of three gyroscopes, a triaxial accelerometer and two tilt sensors is described. >

True north heading estimator utilizing GPS output information and inertial sensor system output information

Abstract: Inertial sensor information is combined with GPS information derived from satellite information signals separately received by a pair of GPS antennae and separately processed. This information is processed in a manner to arrive at the offset angle between the inertial sensor heading angle and true north.

Apparatus and method for determining velocity of a platform

Abstract: An apparatus and method for determining the velocity of a platform includes a GPS receiver and inertial measurement unit (IMU) located at the platform. The GPS receiver provides GPS navigation data using a plurality of GPS satellites while the inertial measurement unit provides inertial navigation data. Acceleration computed from the GPS navigation data is combined with the inertial acceleration generated from the IMU using a Kalman filter to generate a substantially IMU-bias free acceleration of the platform. The resultant acceleration measurement and the GPS navigation data are used to calculate the velocity of the platform in conjunction with a second Kalman filter for removing GPS systematic errors that are normally removed by use of a ground reference station.

System and method for using parabolic models to improve position estimates from a global positioning system

Abstract: Systems and methods allow for the accurate determination of the terrestrial position of an autonomous vehicle in real time A first position estimate of the vehicle 102 is derived from satellites of a global positioning system and/or a pseudolite(s) The pseudolite(s) may be used exclusively when the satellites are not in the view of the vehicle A second position estimate is derived from an inertial reference unit and/or a vehicle odometer The first and second position estimates are combined and filtered using novel techniques to derive a more accurate third position estimate of the vehicle's position Accordingly, accurate autonomous navigation of the vehicle can be effectuated using the third position estimate

Fault tolerant inertial reference system

Abstract: A fault tolerant inertial reference system employs two independent inertial reference units each having its own inertial sensor array with redundant output information. Each inertial reference unit includes an independent source of position and velocity information through employment of a satellite positioning system. In turn, a high-speed error estimator processes inertial sensor output data from a local inertial sensor array with inertial sensor output data from another external inertial sensor array for determining high-level errors, and a low-speed error estimator processes output data from the local inertial sensor array with the velocity and position information separately obtained from the satellite positioning system for determining low-level errors. In turn these high and low-level errors are processed to determine a fault-free inertial sensor configuration for subsequently determining reliable fault tolerant inertial reference data obtainable with a minimum set of inertial sensors.

Inertial velocity command system

Abstract: A velocity command system is provided with a velocity stabilization mode wherein aircraft flight path referenced velocities are determined with respect to an inertial frame of reference, the flight path referenced velocities are held constant during pilot commanded yaw maneuvers so that the aircraft maintains a fixed inertial referenced flight path regardless of the pointing direction of the aircraft. Velocity control with respect to an inertial frame of reference is accomplished by controlling the aircraft flight path based on aircraft body referenced commanded lateral and longitudinal acceleration and based on aircraft body referenced lateral and longitudinal centrifugal acceleration. Operation in the velocity stabilization mode is provided in response to the manual activation of the velocity stabilization mode by the pilot, provided that the aircraft is already operating in the ground speed mode and the aircraft is not in a coordinated turn.

Hemispherical resonator gyro for precision pointing applications

Abstract: The solid-state Hemispherical Resonator Gyroscope (HRG) uniquely offers the benefits of small size, extremely long life, and ultrahigh reliability for spacecraft pointing and control application. The HRG also offers precision performance which can be scaled through control loop and electronics design tradeoffs. Delco Systems Operations has developed the HRG-based Space Inertial Reference Unit (SIRU), which has been designed to maximize the benefits of small size and high reliability and meet the medium grade performance of most spacecraft. The precision performance required for many imaging spacecraft has been achieved through selected modifications to the SIRU design. The result is a precision pointing IRU which maintains the inherent small-size, high reliability characteristics offered by the solid-state HRG. These attributes enable the weight reduction and life extension of precision imaging spacecraft. Modifications to the SIRU design for precision pointing applications have been implemented and characterized. These modifications and test results are described herein.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Attitude control system conceptual design for Geostationary Operational Environmental Satellite spacecraft series

Abstract: The next generation of the Geostationary Operational Environmental Satellite (GOES-N) will require extremely stringent pointing performance for improved weather prediction. These spacecraft will employ high-precision gyros and star trackers in a,unique control system design concept to achieve the end-to-end pointing performance at the focal plane of the instruments. This paper presents the GOES-N attitude control system conceptual design, sensor complement trade-offs, attitude determination theory, and system performance expectations.

Inertial sensor unit

Abstract: The unit has a number of miniaturised inertial sensors arranged so that they are subjected to the same inertial measurement parameter. The signals from the inertial sensors are fed to the same signal processor for generating an output measurement signal representing the inertial measurement parameter. Each inertial sensor contains a miniaturised resonator, whose resonance characteristic is influenced by the inertial measurement parameter. A number of measurement sensors with different measurement ranges can be used for measurement over an extended measurement range.

The Boeing 777 Fault Tolerant Air Data and Inertial Reference System-a new venture in working together

Abstract: The Boeing Commercial Airplane Group has certified an all-new, integrated Fault Tolerant Air Data and Inertial Reference System (FT-ADIRS) on its 777 airliner. The FT-ADIRS consists of the Fault Tolerant Air Data and Inertial Reference Unit (FT-ADIRU), the Secondary Attitude and Air Data Reference Unit (SAARU), and six Air Data Modules (ADMs). New processes for the design, verification, and validation of the system were developed. The FT-ADIRS redundancy management and system performance were validated using a unique process whereby flight-recorded sensor data were replayed through actual production units. Faults were inserted in a Monte Carlo fashion to demonstrate the ability of the inertial navigation and air data functions to isolate and survive sensor faults in real-time.

Star calibration of the pallet inertial sensor assembly for the high-altitude balloon experiment

Abstract: A gyroscope star calibration algorithm developed for use in the High- Altitude Balloon Experiment, a program to resolve acquisition, tracking, and pointing/fire control issues in support of future directed energy programs, is presented. The initial acquisition of a target from a free- floating balloon platform necessitates an inertial pointing capability. Gyroscopes are normally used to measure angular rotations with respect to an inertial reference frame. Given an initial attitude, the gyro measurements can be used to determine the attitude at any later time. For the High Altitude Balloon Experiment, GPS and a magnetometer are used to provide an initial estimate of the payload attitude. This paper describes a deterministic algorithm, which uses star sensors measurements to correct initial attitude uncertainty errors. In addition, a simple method for measuring gyro bias in flight is presented. The consequences of star sensor to gyro frame misalignment are examined for both rate gyros and angular pulse output gyros. This paper describes the algorithm used to meet the calibration accuracy required to inertial pointing of the gimbaled payload.

Central Inertial Guidance Test Facility (CIGTF) Testing of a Depolarized Fiber Optic Gyro Inertial Sensor Assembly

Abstract: Fiber Optic Gyroscopes (FOG’s) have progressed to a state where they are now being used in a variety of missile and aircraft attitude reference systems The majority of these systems utilize polarization preserving fiber in the ring This paper presents the design and test results for an innovative single axis FOG which uses commercially available commuuication fiber for the rate sensing element Thorough testing of a single axis unit at the Central Inertial Guidance Test Facility (CIGTF) at Holloman Aii Force Base, New Mexico, USA followed by Smiths Industries testing of a triad of gyros integrated in an Inertial Sensor Assembly (ISA) has demonstrated performauce superior to the 1 degree per hour design requirement Testing consisted of static and dynamic baseline tests, input axis alignment tests, static and dynamic temperature and magnetic field testing This paper presents an overview of the FOG design and a discussion of the test results

Observability of Gravimeter-Aided Inertial Navigation Systems

Abstract: In this work, the possibility of creating inertial navigation systems corrected in the presence of gravity anomalies is investigated. Observability of gravimeter-aided inertial navigation systems is an important practical question when Kalman filtering is applied for its correction. To solve this problem, error equations are obtained in which errors stipulated by geocentric and geodetic noncoincidence of triads during a vehicle motion above anomaly of the level surface are taken into account. The observability of inertial navigation systems with a gravimeter in the vertical channel is proved in this article. The conditions for observability of position, velocity, and drifts of a gyrostabilized platform on a moving vehicle are obtained.