 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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- Results of Comparative Study of Light Sources for Fiber Optic Gyroscopes
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Abstract: Light source is one of the key components of fiber optic gyroscopes. The performance of these gyros, including their scale factor and bias stability depend directly on the parameters of the light source output. Although the modern market offers a variety of light sources potentially suitable for fiber optic gyros, it seems quite challenging to choose a proper light source. The objective of this paper is to study and compare the light sources made by various companies, in particular, to measure and analyze the pattern and width of their spectra, weighted average wavelength, the output optical power, and the power consumption. A comprehensive comparative analysis of the obtained characteristics of the sources has been carried out.
PubDate: 2022-12-01
- AUV Relative Position and Attitude Determination Using Acoustic Beacons
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Abstract: A real-time algorithm for autonomous underwater vehicle (AUV) relative position and attitude determination has been proposed, which uses range measurements to acoustic beacons positioned at small distances to each other on a common platform. Mutual arrangement of AUV and beacons is a priori unknown, and their time scales are not synchronized. The developed algorithm considers the nonlinear character of measurements while featuring a lower computational burden compared to the maximum likelihood method. Results from simulation and postprocessing of real data with different AUV arrangements relative to the beacons are provided.
PubDate: 2022-12-01
- Decomposed Algorithm for Spacecraft Attitude Estimation in Stellar
Correction Mode-
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Abstract: The paper discusses the problem of a spacecraft attitude estimation and its solution by integrating the measurement data from an information-redundant gyro unit and a stellar navigation system. The traditional solution methods are based on the use of Kalman filter of n + 3 order, where n > 3 is the number of measurement channels (gyroscopes or angular rate sensors). The numerical implementation of the corresponding algorithm on an onboard computer requires significant computational burden. To considerably reduce the computational complexity of the algorithm without losing the accuracy, it is proposed to use a method of decomposing the filter of n + 3 order into three filters of the second order and n − 3 filters of the first order.
PubDate: 2022-12-01
- Rapid Re-Convergence of Real-Time Dynamic Precise Point Positioning by
Adding Velocity Constraints-
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Abstract: — In challenging environments like urban vehicle navigation and geological hazards, the GNSS signals are easily blocked, and the long re-convergence time seriously limits many applications of real-time dynamic precise point positioning. Considering that the velocity accuracy is better than the position during re-convergence epochs, we proposed a real-time rapid-positioning method by introducing velocity constraints into the dynamic PPP. According to the different motion states and environments, different velocity constraints are used adaptively. For example, the zero-velocity constraint model is used in the stationary state; the Doppler-velocity constraint model is used when the most visible satellites are temporarily blocked; the other-sensors-velocity constraint model is used when the satellite signal is blocked frequently. Considering that the inaccurate dynamic model will affect the dynamic positioning results, the velocity constraint can be gradually relaxed after the GNSS signals are reacquired and the ambiguity gradually converges. Based on static and kinematic experiments with GPS data, the results show that when the number of visible satellites is greatly dropped due to signal blocking, the new positioning method can significantly speed up the re-convergence of precise point positioning, maintain high accuracy and improve the continuity of real-time dynamic positioning in a short time.
PubDate: 2022-12-01
- New Results of Estimation of Modern Global Ultrahigh-Degree Models of the
Earth’s Gravity Field in the World Ocean-
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Abstract: — With the increase in accuracy and resolution of modern global models of the Earth’s gravity field, more opportunities have appeared to use them in solving the regional gravimetric problems. At the same time, the estimates of existing models depending on the region and geomorphology, as well as methods for predicting the reliability of data in models, taking into account the scale and nature of the problem being solved, become more important. The article is devoted to new estimates of modern models of the gravity field in various regions of the World Ocean and over various geomorphological structures. The estimates were obtained by comparing the data of the most relevant models of the gravity field with the data of high–precision marine areal and route surveys carried out in all major areas of the World Ocean. Based on the results, the model field is promising and it is possible to estimate the spatial distribution of model field errors in the World Ocean. A method for efficient preliminary zoning of a model field in the ocean is proposed. The features of the development of the Earth’s gravity field models are considered, taking into account their actual accuracy and resolution, as well as the issue of general reliability of modern model data in the high-latitude Arctic.
PubDate: 2022-12-01
- ARAIM Availability of BDS-2 and BDS-3 in the Global LPV-200 Approach
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Abstract: — With the addition of multi-frequency and multi-constellation systems, the Advanced Receiver Autonomous Integrity Monitoring (ARAIM) algorithm is expected to provide a global vertical and horizontal guidance for the localizer performance of vertical guidance (LPV)-200 approach phase in aeronautical navigation worldwide. Currently, the second and third generations of the BeiDou navigation satellite system (BDS-2 and BDS-3) provide their services to users. We consider ARAIM for dual-frequency iono-free BDS pseudorange combinations. With the aim to improve the service performance of the BDS-2 and BDS-3 systems, the assumed integrity support message (ISM) was used to calculate the vertical protection level (VPL) for the LPV-200 approach. The impact of the different parameters of ISM on the ARAIM availability was evaluated. The results demonstrate that, compared with BDS-3, the global coverage of availability for BDS-2+BDS-3 is slightly higher, mainly due to the increase of the number of visible satellites. The availability of BeiDou in the Americas is affected by user range accuracy (URA). With URA decreasing from 2.0 to 0.5 m, the ARAIM availability of BDS-2+BDS-3 in the Americas increased from 50 to 99.9%.
PubDate: 2022-12-01
- A Review of Navigation Algorithms for Unmanned Aerial Vehicles Based on
Computer Vision Systems-
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Abstract: The article analyzes the works devoted to outdoor navigation of unmanned aerial vehicles (UAVs) in GNSS-denied environments using computer vision systems (optical range cameras). The algorithms addressed are based on matching of UAV-generated images with the available georeferenced terrain images. Images are matched either pixel by pixel, by their key points, or using neural networks. The stages of each algorithm, as well as the accuracy achieved by the authors and the field data used for testing are considered. The paper concludes with a discussion of the capabilities and limitations of the proposed approaches.
PubDate: 2022-12-01
- State-of-the-Art Strapdown Airborne Gravimeters: Analysis of the
Development-
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Abstract: The paper analyzes the development of strapdown inertial airborne gravimeters, which have significant advantages over gyrostabilized gravimeters in terms of size, power consumption and cost and substantially expand the capabilities of gravity survey. Technical solutions are described that make implementation of strapdown airborne gravimeters possible. The trends in their development are discussed, including integration of data from strapdown and gyrostabilized gravimeters.
PubDate: 2022-12-01
- Precise Calibration of Strapdown INS Using Low-Accuracy Turntables
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Abstract: A method for calibration of strapdown inertial navigation systems (SINS) is proposed which combines the advantages of the approached based on the application of the Kalman filter, on the one hand, and estimates of changes in specific force in the horizon plane before and after rotation of the turntable, on the other. In contrast to the known methods of SINS calibration that take into account the changes in the horizon components of acceleration with a model measurement matrix in iterative calculations of corrections to biases, scale factors, and misalignments of accelerometers and gyroscopes (hereinafter called gyros), the approach described in this paper uses actual rotations and positions of the SINS with account for previous iterations rather than SINS uniaxial rotation angles and positions specified to a turntable. The same experimental data were used to compare the proposed method with the one using the model measurement matrix. The results have shown that the overall error of the SINS calibrated by the proposed method is less than in the other case; in addition, the number of required iterative refinements is less. The proposed method allows navigation-grade SINS to be calibrated on low-accuracy turntables, with proper consideration for the inaccuracy of the SINS inertial measurement unit (IMU) rotation in shock absorbers.
PubDate: 2022-12-01
- Application of Differential Code Biases in Multi-GNSS Measurements in
Real-Time Precise Point Positioning-
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Abstract: The article experimentally proves the importance of applying Differential Code Biases (DCB) when determining coordinates by Precise Point Positioning (PPP) based on multi-GNSS measurements (GPS, GLONASS, Galileo). The application of DCB significantly reduces the convergence time of the navigation solution. Modifications to RTKLIB software required for the experiment are described, which allow applying the DCB in real time.
PubDate: 2022-12-01
- Multiple AUV Navigation without Using Acoustic Beacons
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Abstract: Autonomous bottom sensor networks are increasingly used to collect various data near the sea bottom. Transmitting these large accumulated data arrays to the data collection and processing center is a pressing problem. A promising method to retrieve data from sensor nodes is to use multiple autonomous underwater vehicles (AUV). The quality of underwater mission performance is then determined by accurate navigation of each vehicle within the group. The article presents a new efficient method of multiple AUV navigation for performing the vital task – servicing the autonomous network of bottom sensor stations. The method requires neither beacons of long baseline acoustic navigation system (LBL ANS) nor surface vehicles. During the mission, some AUVs are moving to the target sensor nodes, while the others are docked to the sensor nodes, read out the accumulated data, and perform the maintenance procedures (battery recharging, state diagnostics, and correction of the mission program). The main idea of the method is that the AUVs docked to the sensor nodes function as temporary stationary beacons of the differential ranging (DR) ANS for the other moving AUVs. The algorithms of the proposed navigation method are considered.
PubDate: 2022-12-01
- Design Philosophy for a Class Of Precision Rate Tables with Inertial
Sensors in the Feedback Loop-
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Abstract: Abstract—The paper considers a concept for designing the precision gyroscopic rate tables with digital control systems and inertial sensors as modern mechatronic control systems. Based on these systems, calibration algorithms for state primary standards of angular velocities can be elaborated. The designs of subordinate standards also containing inertial sensors and digital control systems can be developed based on the designs of the primary standards. These designs include the solutions earlier proposed by the authors and the new ones developed using the proposed algorithms.
PubDate: 2022-09-01
- Methods for Robust Filtering Based on Numerical Characteristics of Input
Processes in Solving Problems of Navigation Information Processing and
Motion Control-
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Abstract: A problem of robust linear filtering of random processes is considered under given constrains on the variance of the process itself and (or) the variances of derivatives, while the form of the power spectral density (PSD) of the process is assumed to be unknown. It is shown that a number of problems of navigation information processing and motion control can be reduced to the above formulation. Informativity of variances of derivatives and the effectiveness of the solutions obtained are analyzed when the variances are used to describe the properties of input processes (IP). A method for obtaining data on IP variances based on the analysis of the numerical characteristics of critical points is considered. Examples of solutions of applied problems are given.
PubDate: 2022-09-01
- Animal Migration Studies with the Use of ICARUS Scientific Equipment in
the URAGAN Space Experiment aboard the Russian Segment of the ISS-
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Abstract: — The major challenges of space research are monitoring and exploration of our planet, which are carried out through the use of remote sensing satellites (RSS) operating in near-Earth orbits. They provide invaluable information for assessing the environmental, epidemiological and other situations on our planet, including animal migration data. The ICARUS project (International Cooperation for Animal Research Using Space) implemented on the International Space Station (ISS) is an ideal laboratory for in-orbit testing of instrumentation and various space technologies aimed to refine methods for tracking movements of mammals and birds. The paper analyzes the experience in the operation of the animal migration monitoring system installed in the Russian segment (RS) of the ISS (ISS RS). The system has incorporated the latest accomplishments in space science, satellite navigation, control technology, and microelectronics. The scientific results on the study of animal and bird migrations obtained within the Russian research program are briefly discussed.
PubDate: 2022-09-01
- Studying the Performance of a Three-Axis Rate Table for Navigation System
Tests-
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Abstract: Abstract—A procedure for measuring the systematic error in angular positioning of a rate table platform based on goniometrical method is described. The method has been tested on a three-axis rate table STA-10. Possible error sources have been detected. The positioning error has been compensated and greatly reduced. Instability of rate table axes rotation rate has been studied, and nonortogonality of its axes has been measured.
PubDate: 2022-09-01
- Satellite Time Keeping Methodology for IRNSS/NavIC Constellation
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Abstract: — Accuracy of range measurements using navigation satellites primarily depends on on-board clock correction parameters which are broadcasted to users periodically. The on-board clock offset, a critical correction parameter which accumulates due to fractional frequency offset as well as frequency drift, has to be maintained within the allocated broadcast limit throughout the satellite’s service. In IRNSS satellites, the clock offset is maintained within the broadcast limit by applying frequency offset corrections to the on-board atomic clock monitoring unit. In this paper, we discuss the methodology implemented for computing the clock offset using one-way range measurement data. Further, we report the time keeping methodology employed in IRNSS satellites that enables maintaining the satellite clock offset within the broadcast limit with minimum number of intervening frequency offset corrections throughout their operational life time.
PubDate: 2022-09-01
- Study of Scalar Calibration Problems for a Vector Meter
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Abstract: The article continues studying the features of scalar calibration. The main objectives of this work are to generalize and analyze known calibration programs, and compare the analytical metrics of estimates obtained from the programs generated using various target functions, assuming normal distribution of measurement errors.The article also draws conclusions about the feasibility of optimizing the calibration programs and about the general logic of their synthesis.
PubDate: 2022-09-01
- The Isotope Shift Suppression in NMR-based Balanced Quantum Rotation
Sensor-
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Abstract: — Designing a compact balanced quantum rotation sensor (gyroscope) based on nuclear magnetic resonance in xenon is one of the most urgent and promising tasks in modern metrology. The ultimate accuracy of the sensor is mostly constrained by the isotope shift conditioned by the difference in relaxation rates of two xenon isotopes under spatially nonuniform spin-exchange pumping of nuclear magnetic moments. The proposed method for suppressing the isotope shift and its partial derivatives is based on creating the external magnetic field with nonlinear spatial gradient. The simulation results based on experimental data demonstrate that the method can be applied to small gas cells with higher spatial nonlinearity of pumping parameters.
PubDate: 2022-06-01
DOI: 10.1134/S2075108722020079
- Multipath Mitigation Technique for GNSS Gyrocompass Using Phase
Measurements-
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Abstract: The paper focuses on the methods to reduce the satellite signal multipath effect on the accuracy of attitude parameters, in particular, the true heading, generated by the designed marine GNSS gyrocompass—INS/GNSS system with the single-axis rotation of the antenna and IMU units. Test results for the compass prototype model have been provided, with the artificial distortions created by the GNSS signal reflector.
PubDate: 2022-06-01
DOI: 10.1134/S2075108722020031
- Temperature and Humidity Impact on the Accuracy of Chekan-AM Gravimeter
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Abstract: — Marine gravimetry aims to obtain accurate and reliable data on gravity field anomalies in water areas. Modern gravimetric systems such as Chekan-AM feature high accuracy due to the novel circuit and design solutions in the conditions specified in the technical description. The article discusses the influence of ambient temperature and humidity on the accuracy of the Chekan-AM gravimeter. These meteorological factors matter both during short measurement periods, within individual survey lines, and long periods, during expeditions far away from the reference points. For 18 months, the authors of the article have been carrying out laboratory tests of the gravimeter with simultaneous registration of meteorological parameters. Based on the observation results, the correlation dependences of the zero-point drift of the gravimeter sensitive element on seasonal temperature and humidity variations were calculated. Marine expeditions data were also studied, with analysis of the temperature impact over a short time period during the marine gravimetric survey. Based on the results of the experiments it was shown that meteorological monitoring should be performed in the course of gravimetric surveys, including those onboard research vessels. An additional thermal noise becomes noticeable in the survey conducted in an area with low variations in the gravity field, and it should be considered when analyzing and evaluating the results.
PubDate: 2022-06-01
DOI: 10.1134/S2075108722020080
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