Strapdown Inertial System Research Articles

Dynamic model and simulation of aseismatic system about laser gyro strapdown inertial measure assembly based on MSTMM

The precision of the laser gyro used in tactical missiles is poor because of dithering frequency, actuating by vibration, shock and overload in dynamical environment. This paper introduces the transfer matrix method of the multibody system (MSTMM), establishes the dynamic model of the laser gyro strapdown inertial measure assembly aseismatic system, and analyzes the precision affected by dithering of the laser gyro and shocking of the tactical missile. And the dynamic response of the laser gyro strapdown inertial measure assembly aseismatic system is obtained by simulating the multibody system model. The simulation result indicates a theoretical idea to design the vibration isolation for the laser gyro strapdown inertial measure assembly.

Differential methods of identifying gyro noise structure

The paper considers the differences in accuracy criteria for gyros in two applications: measuring rotation about a fixed axis and measuring rotation about a point. We describe the class of gyro noise with zero spectral density at zero frequency. This noise does not cause errors in angles of rotation (i.e., integrals of angular velocity projections on the gyro sensitivity axis) to accumulate with time, but lead to accumulation of errors in attitude determined by strapdown inertial systems. Ways of identifying gyro noise structure using the known lower order variances are analyzed: two-sample variance (Allan variance), three-sample variance (Hadamar variance), and proposed higher order variances [1].

Integrated attitude reference and navigation system for orbital spacecraft

The paper considers an integrated attitude reference and navigation system for an orbital spacecraft. The system comprises a strapdown inertial attitude reference system based on electrostatic gyros (ESGs) and fiber-optic gyros (FOGs). Algorithms for joint processing of ESG and FOG data which use a Kalman filter and the corresponding criteria are described. Results of computer simulation of the system algorithms with MATLAB using ESG and FOG real test data are given.

Coarse Alignment of a Ship's Strapdown Inertial Attitude Reference System Using Velocity Loci

This paper presents a novel estimation method for fast initial coarse alignment of a ship's strapdown inertial attitude reference system using only inertial measurement unit (IMU) measurements for quasi-static alignment and IMU measurements with GPS aiding for moving-base alignment. Unlike several current techniques, the presented estimation method is effective with any initial attitude error. The estimator is based on the decomposition of the attitude quaternion into separate Earth motion, inertial rate, and alignment quaternions. The alignment quaternion is estimated using a minimum variance fit between loci of body- and navigation-frame velocity vectors using solutions to Wahba's problem. One set of vectors is derived from time integrals of measured vehicle motions, and the second set is derived from Earth motion and GPS data (when moving). For the case of quasi-static alignment, an algebraic expression for the covariance of the attitude estimate as a function of the variance of navigation-frame velocity disturbances is developed. It is shown that, by averaging and interleaving the velocity vectors, the resulting attitude estimate is improved over sequential sampling techniques. It is further shown, for a maneuvering vessel, that a continuous estimate of the attitude error covariance can be generated from the IMU data. This latter feature allows direct initialization of a follow-on fine-alignment stochastic estimator's covariance matrix. Results are presented for quasi-static alignment using inertial sensors only and for full in-motion alignment using navigation-frame GPS velocity and position aiding.

Small-sized integrated navigation system

Strap-down inertial and satellite system BISNS-1T developed by these authors from the Moscow Aviation Institute and JSC “Transas-Telematics” at the request of the Joint-Stock Company “Transas-Aviation” is presented. The main objective of this presentation is to acquaint our audience with the structure features, design, and algorithms of the system, allowing us to raise the accuracy and integrity of the navigation data and to show the results of its natural tests: at the test-bench and on a vehicle. The structure and design of the system were defined taking into account that it should be installed aboard the unmanned aerial vehicle, “Dozor” (Joint-Stock Company “Transas”).

Detecting the characteristics of long-wave irregularity of maglevrailway based on strap-down inertial system

Detecting the characteristics of long-wave irregularity of maglevrailway based on strap-down inertial system

光学陀螺捷联惯性系统的发展与展望

光学陀螺捷联惯性系统的发展与展望

Technologies for positioning pipeline routes and defective places based on integrating intratubal and satellite navigation systems

Four methods of main pipeline positioning are considered. The most progressive and effective method is the one based on the integration of a satellite navigation system (GPS), a strapdown inertial system of navigation (SINS), and a geoinformation system (GIS). The positioning technology of subsurface pipelines is illustrated by the results from actual pipeline positioning.

MODELING AND NUMERICAL SIMULATION OF AN ALGORITHM FOR THE INERTIAL SENSORS ERRORS REDUCTION AND FOR THE INCREASE OF THE STRAP-DOWN NAVIGATOR REDUNDANCY DEGREE IN A LOW COST ARCHITECTURE

In this paper, an algorithm for the inertial sensors errors reduction in a strap-down inertial navigation system, using several miniaturized inertial sensors for each axis of the vehicle frame, is conceived. The algorithm is based on the idea of the maximum ratio-combined telecommunications method. We consider that it would be much more advantageous to set a high number of miniaturized sensors on each input axis of the strap-down inertial system instead of a single one, more accurate but expensive and with larger dimensions. Moreover, a redundant system, which would isolate any of the sensors in case of its malfunctioning, is obtained. In order to test the algorithm, Simulink code is used for algorithm and for the acceleration inertial sensors modeling. The Simulink resulted sensors models include their real errors, based on the data sheets parameters, and were conceived based on the IEEE analytical standardized accelerometers model. An integration algorithm is obtained, in which the signal noise power delivered to the navigation processor, is reduced, proportionally with the number of the integrated sensors. At the same time, the bias of the resulted signal is reduced, and provides a high redundancy degree for the strap-down inertial navigation system at a lower cost than at the cost of more accurate and expensive sensors.

A new noncommutative kinematic effect and its manifestations in strapdown inertial orientation systems based on fiber optic gyros

A brief survey of the developments in fiber optic gyros for space applications is given. The results of studies of strapdown inertial orientation systems (SIOS) based on triaxial fiber optic gyro are presented. A method for analytical estimation of strapdown inertial orientation system accuracy is given. A variant of a triaxial fiber optic gyro (FOG) with one common emitter is considered. The specific feature of such triaxial FOG is as follows: whereas in the noise correlation matrix of the triaxial fiber optic gyro with three autonomous single-axis FOG, only three diagonal elements are nonzero, in the case of the triaxial FOG with one common emitter, all nine elements in the noise correlation matrix are nonzero. The difference in noise correlations in three measurement channels of the triaxial FOG may result in a considerable (by orders of magnitude) difference in the precision of SIOS. This new noncommutative kinematic effect that was not noticed earlier in gyroscopy and navigation is analyzed using the SIOS based on fiber optic gyros [1].

On GPS/GLONASS/INS Tight Integration for Gimbal and Strapdown Systems of Different Accuracy

AbstractGPS/GLONASS/INS tight integration problem is considered from the viewpoint of mechanics of autonomous and aided inertial navigation. Integration architectures for gimbal and strapdown inertial systems of high or low accuracy are compared.

A WAVELET-BASED METHOD FOR PROCESSING SIGNAL OF FOG IN STRAP-DOWN INERTIAL SYSTEMS

Fibre optical gyroscopes (FOGs) have been applied widely in many fields in contrast with their counterparts such as mechanical gyroscopes and ring laser gyroscopes. The precision of FOG is affected significantly by bias drift, angle random walk, temperature effects and noises. Especially, uncertain disturbances resulting from road irregularities often affect accuracy of strap-down inertial system (SINS). Hence, eliminating uncertain disturbances from outputs of a FOG plays a crucial role to improve accuracy of SINS. This paper presents a wavelet-based method for denoising signals of FOGs in SINS used for exploring and rescuing robots in coal mines. Property of road irregularities in mines is taken into account as a key factor resulting in uncertain disturbances in this research. Both frequency band and amplitude of uncertain disturbances are introduced to choose filtering thresholds. Experimental results have demonstrated that the proposed method can efficiently eliminate uncertain disturbances due to road irregularities from outputs of FOGs and improve accuracy of surrogate data. It indicates that the proposed method has a significant potential in FOG-related applications.

THE BIAS TEMPERATURE DEPENDENCE ESTIMATION AND COMPENSATION FOR AN ACCELEROMETER BY USE OF THE NEURO-FUZZY TECHNIQUES

In this paper, we describe a new method for improved performance of inertial sensors, with applications in strap-down inertial systems. A new empirical model is proposed for the bias temperature dependence compensation of accelerometers using their input and output data. Experimental testing of the accelerometer is first realized, as data for 2 inputs and 1 output are collected. Based on this data, an empirical model is built using a neuro-fuzzy network, which learns the process behavior and uses a Fuzzy Inference System (FIS) for model realization. The improvement in the reproduction quality of the experimental surface by the neuro-fuzzy model is achieved through the FIS training using a Sugeno learning algorithm with two inputs and one output. Generation and training of the FIS are performed with Matlab functions, the training of which is realized on a high number of epochs, for example, on a number of 105 training epochs. It is noticed that the proposed algorithm leads to a 35.5 times reduction in the error due to temperature dependence of the bias.

Model of dynamic descriptions of the strapdown inertial system

Model of dynamic descriptions of the strapdown inertial system

Railway track inspection using INS-BINS-N

The results of an integrated strap-down inertial system development and tests are presented. The system includes laser gyros and accelerometers and is intended for measuring railway track angular parameters. To raise the accuracy of angles and distance measurements the inertial system is integrated with a GPS receiver and an odometer. Test results showed that BINS-N accuracy is better than the accuracy of an issued system

NUMERICAL AND EXPERIMENTAL STUDY OF AN ALGORITHM OF ATTITUDE FOR A STRAP-DOWN INERTIAL SYSTEM

Two numerical algorithms are presented here: the integration of the Poisson equation of attitude and the calculation of the angles from the elements of the matrix of attitude. The method here suggested lies in the use of a fast algorithm of Wilcox type in which the errors of commutation are eliminated by the use of a numerical artifice implemented in a data acquisition card: information on the angular velocity is given on only one channel among the three channels of the chart (the two other channels are put at zero) during a step of calculation. The numerical simulations are performed and validated by use of the Wilcox integration method which implies errors of commutation, with various orders of truncation, and by the integration method with an algorithm with two rates of calculation. By use of a strap-down inertial system and the Matlab software, real time experimental tests are carried out to calculate the best alternatives of the algorithm of integration resulted from the numerical simulations.

A Unified Mathematical Framework for Strapdown Algorithm Design

A Unified Mathematical Framework for Strapdown Algorithm Design

Fiber-optic strapdown inertial system with sensing cluster continuous rotation

This research describes a technique and a performance analysis of a fiber-optic strapdown inertial system with sensing cluster continuous rotation around the vertical body axis of the vehicle. The bias errors of these inertial sensors, gyros and accelerometers with cluster rotation, will have periodically varying corresponding components along the body axes. The modulated sensor errors produce reduced system errors. Simulation results indicate that, compared with the conventional method, the proposed approach attenuates the navigation errors and alignment errors due to the gyros' error and the accelerometers' error.

Analytical Modeling of Sensor Quantization in Strapdown Inertial Navigation Error Equations

Although generally not considered a major contributor to system inaccuracy, inertial sensor quantization error, if not properly modeled, can lead to erroneously large estimates of its impact on inertial navigation system performance. Analytical methods are described for modeling inertial sensor quantization in strapdown inertial system error parameter propagation and measurement equations. Error propagation equations are derived in classical differential error state dynamic and discrete difference format. It is shown how the attitude, velocity, and sensor error parameters in these equations must be modified to enable proper sensor quantization error modeling as white noise and to account for differences in attitude, velocity, and position update frequencies. The discrete difference error equation form is used to develop values for attitude/velocity measurement noise covariances and for spectral densities of white quantization noise terms in the differential error propagation equations. A general discussion is included of how quantization white noise spectral densities should be computed for the differential error propagation equations for compatibility with two-speed attitude, velocity, and position updating algorithms. Validity limits for white noise modeling approximations and methods for reducing quantization noise are discussed. Numerical examples are provided.

Alignment of Strapdown Inertial System with Full Uncertainty of Initial Sensor Unit Attitude

Alignment of Strapdown Inertial System with Full Uncertainty of Initial Sensor Unit Attitude