Showing papers on "Inertial measurement unit published in 1984"

Artificial satellite attitude control system

Abstract: A system for controlling an attitude of an artificial satellite to decide the present attitude of the satellite on a spatial coordinate and angular velocities of rotation about body axes of the satellite, by the use of inertial sensors and star sensors, to calculate an objective attitude of the satellite on the basis of the present attitude information, the angular velocities of rotation about the body axes and orbit information received from a ground station so that the attitude of the satellite and the changing rate thereof are controlled simultaneously.

Adaptation of a strapdown formulation for processing inertial platform data

Abstract: An estimator propagation formulation which ultilizes dynamic data (attitude and sensed acceleration information) from a gimballed inertial platform has been developed to aid in the Shuttle post-flight trajectory reconstruction process and aerodynamic coefficient determination studies. Unlike the classical inertial algorithms, this formulation yields a six degree-of-freedom fully coupled state and attitude estimate. Furthermore, this inertial version is shown to be independent of initial unknown platform misalignments. Results obtained using actual Inertial Measurement Unit (IMU) data and Aerodynamic Coefficient Identification Package (ACIP) strap down data from Shuttle flights are presented.

Marine positioning with a GPS-aided inertial navigation system

Abstract: The accuracy requirements for precise horizontal positioning of a moving vessel in the offshore and open ocean are expected to approach the 3m to Sm level within this decade Previous simulation studies and lan d-based tests have shown that such a level of accuracy can be achieved by a combination of inertial navigation and GPS satellite positioning techniques A Kalman filter and an optimal smoother have been developed to integrate an inertial navigation system with a slow switching GPS satellite receiver for marine positioning purposes The Kalman filter and optimal smoother were tested on the Canadian east coast in November 1982 The paper outlines first the operational principle of the GPS aided inertial navigation system and the development of the Kalman filter and smoother It then presents the results and a detailed error analysis of the offshore tests

A Fault Tolerant System for an Integrated Avionics Sensor Configuration

Abstract: An aircraft sensor fault tolerant system methodology for the Transport Systems Research Vehicle in a Microwave Landing System (MLS) environment is described The fault tolerant system provides reliable estimates in the presence of possible failures both in ground-based navigation aids, and in on-board flight control and inertial sensors Sensor failures are identified by utilizing the analytic relationships between the various sensors arising from the aircraft point mass equations of motion The estimation and failure detection performance of the software implementation (called FINDS) of the developed system was analyzed on a nonlinear digital simulation of the research aircraft Simulation results showing the detection performance of FINDS, using a dual redundant sensor compliment, are presented for bias, hardover, null, ramp, increased noise and scale factor failures In general, the results show that FINDS can distinguish between normal operating sensor errors and failures while providing an excellent detection speed for bias failures in the MLS, indicated airspeed, attitude and radar altimeter sensors

Flight test configuration for verifying inertial sensor redundancy management techniques

Abstract: The Redundant Strapdown Inertial Measurement Unit presently tested in flight configuration consists of a semioctahedral array of four dynamically tuned, two-degree-of-freedom (TDOF) gyros and four TDOF accelerometers which can provide dual, fail-operational performance for integrated avionics systems. Attention is given to the multilevel algorithm used for the detection and isolation of three ranges of sensor failure in an integrated avionics context. A technique for the generation of accelerometer and gyro error thresholds which is sensitive to dynamic sensor errors and separation effects is presented, together with simulation results. Emphasis is placed on the ensuring of highly reliable data for flight control/navigation functions, while minimizing false or missed alarms.

Application of Multifunction Strapdown Inertial System

Abstract: : Reliability, redundancy, and survivability are key issues as integrated requirements for flight control, fire control, propulsion control and navigation are developed. These integrated systems require dependable sources of inertial measurement data. Current inertial systems, however, are expensive to acquire and maintain, dedicated to specific systems, and are not designed to meet integrated reliability, redundancy, and survivability, requirements. The Multifunction Strapdown Inertial System concept uses a minimum number of inertial sensors in a survivable configuration to provide inertial data for flight control, navigation, weapon delivery, cockpit displays, and sensor stabilization. Because of advantages in survivability, life cycle cost, maintainability and performance, the Multifunction Flight Control Reference System (MFCRS) program was initiated to verify, through flight test, on a McDonnel Douglas F-15 Eagle the key issues of redundancy management and flight control. A redundancy management system based on parity equations was designed. The sensors were arranged in two skewed and dispersed clusters. (Author)

Fault-tolerant system considerations for a redundant strapdown inertial measurement unit

Abstract: The development and evaluation of a fault-tolerant system for the Redundant Strapdown Inertial Measurement Unit (RSDIMU) being developed and evaluated by the NASA Langley Research Center was continued. The RSDIMU consists of four two-degree-of-freedom gyros and accelerometers mounted on the faces of a semi-octahedron which can be separated into two halves for damage protection. Compensated and uncompensated fault-tolerant system failure decision algorithms were compared. An algorithm to compensate for sensor noise effects in the fault-tolerant system thresholds was evaluated via simulation. The effects of sensor location and magnitude of the vehicle structural modes on system performance were assessed. A threshold generation algorithm, which incorporates noise compensation and filtered parity equation residuals for structural mode compensation, was evaluated. The effects of the fault-tolerant system on navigational accuracy were also considered. A sensor error parametric study was performed in an attempt to improve the soft failure detection capability without obtaining false alarms. Also examined was an FDI system strategy based on the pairwise comparison of sensor measurements. This strategy has the specific advantage of, in many instances, successfully detecting and isolating up to two simultaneously occurring failures.

The DREO (Defence Research Establishment Ottawa) Inertial Navigation Laboratory: Development and Test Capabilities,

Abstract: : The DREO Inertial Navigation Laboratory was developed between 1977 and 1981 as the only complete gyroscope, accelerometer and inertial system test laboratory for the evaluation of strapdown components and systems in Canada. With the aid of a consultant, the laboratory was designed for maximum flexibility; virtually any type of gyroscope can be excited and tested with existing test equipment. The purpose of such a laboratory is twofold; primarily it provides a test facility for the evaluation of manufacturer's navigation components before procurement of systems but as well it is a flexible, independent facility for experimentation, research and development. More specifically, work within the laboratory has centered upon investigation and characterization of low cost strapdown inertial navigation components ans systems. Strapdown technology holds the promise of low cost, long lifetime and ease of maintenance with the mechanical complexity of the traditional gimballed systems being replaced by software computation. Testing of strapdown gyroscopes is quite different from that of gyroscopes employed on gimballed platforms; a strapdown gyroscope must operate over the entire dynamic range of the vehicle within which it is mounted including not only the possibility of high angular rates but alos severe vibration and shock. This report details the development, equipment types and specifications, data acquisition capabilities and tests that can be performed in the DREO Inertial Navigation Laboratory. Additional keywords: Canada; Specifications.