High Dynamic Conditions Research Articles

A star identification algorithm for rolling shutter exposure based on Hough transform

The star identification algorithm usually identifies stars by angular distance matching. However, under high dynamic conditions, the rolling shutter effect distorts the angular distances between the measured and true star positions, leading to plethoric false matches and requiring complex and time-consuming verification for star identification. Low identification rate hinders the application of low-noise and cost-effective rolling shutter image sensors. In this work, we first study a rolling shutter distortion model of angular distances between stars, and then propose a novel three-stage star identification algorithm to identify distorted star images captured by the rolling shutter star sensor. The first stage uses a modified grid algorithm with adaptive error tolerance and an expanded pattern database to efficiently eliminate spurious matches. The second stage performs angular velocity estimation based on Hough transform to verify the matches that follow the same distortion pattern. The third stage applies a rolling shutter error correction method for further verification. Both the simulation and night sky image test demonstrate the effectiveness and efficiency of our algorithm under high dynamic conditions. The accuracy of angular velocity estimation method by Hough transform is evaluated and the root mean square error is below 0.5 (°)/s. Our algorithm achieves a 95.7% identification rate at an angular velocity of 10 (°)/s, which is much higher than traditional algorithms.

Multipoint Cluster Observations of Kinetic Alfvén Waves, Electron Energization, and O+ Ion Outflow Response in the Mid‐Altitude Cusp Associated With Solar Wind Pressure and/or IMF BZ Variations

AbstractWe report the properties of low frequency (LF) electromagnetic fluctuations (≤11 Hz) in relation to input electron and ion outflow response observed by Cluster in the mid‐altitude cusp during high solar wind dynamic pressure PSW and active magnetospheric conditions (Kp = 4+). The multipoint observations reveal the dynamic interplay between the spatial‐temporal properties of the wave and electron inputs and the ion outflow response enabling an assessment of causal connections. The LF waves are identified as ingoing traveling Alfvén waves that become dispersive at the ion gyroradius scale (i.e., kinetic Alfvén waves KAWs). The KAWs are collocated with ingoing field‐aligned electrons and ion outflow at keV energies and below. The KAWs are associated with earthward directed Poynting fluxes and energy densities with peak amplitudes occurring at multiple energy enhancements (“step‐ups”) exhibited in the electrons and ions, attributed to IMF BZ and/or PSW variations. Indicative of a causal connection, KAW Poynting fluxes and energy densities are strongly correlated with precipitating electron energy fluxes and outflowing O+ energies and energy fluxes. These yield mid‐altitude cusp empirical relationships that can be incorporated into or constrain cusp transport models. These results demonstrate the important role played by KAWs in enhancing electron precipitation into the cusp ionosphere and subsequent O+ energization upward along the magnetic field into the mid‐altitude cusp and beyond. The results also suggest the importance of PSW and/or IMF BZ variations in driving/controlling the reconnection source Alfvén wave and electron inputs into the cusp that significantly impact the ion outflow process.

A dynamic star spots extraction method based on pixel association

Star trackers are devices that determine high-accuracy attitude by observing stars. As aerospace technology develops, the dynamic performance of the star tracker becomes increasingly important. In the star images taken under high dynamic conditions, the star spots will be tailed or fractured. It will cause a sharp decrease in Signal-to-Noise Ratio (SNR) and make it a challenge to extract and position star spots. In this paper, an Object-to-Pixel star spots extraction and positioning method based on pixel association was proposed, which is a breakthrough compared to the existing Pixel-to-Object extraction method. In the proposed method, rough extraction of star spots is carried out by the Radon transform and image entropy. Precise positioning of star spots is carried out by Gaussian mixture model (GMM) and maximum likelihood estimation (MLE). Experimental results indicate that the proposed method can achieve reliable extraction for star spots with SNR less than 3 or even close to 1. Meanwhile, the positioning accuracy can be improved by at least twice compared with the conventional threshold method.

A Method of Star Spot Center-of-Mass Localization Algorithm for Star Sensor Under Highly Dynamic Conditions

The starlight guidance system calculates the vehicle attitude information by observing the stars position through the star sensor. When the star sensor operates under high dynamic conditions, the motion blur phenomenon exists in the images taken by it, which seriously affects the computational accuracy of attitude solution. In this paper, based on the motion characteristics of the vehicle under high dynamic conditions, we study and derive the imaging model of the blurred star spot under high dynamic conditions. On this basis, we use the least squares method combined with simulated annealing algorithm to fit the trajectory of the corresponding star spot. The trajectory fitting is based on the information of multiple star streaks in the star field image. And finally, we calculate the center-of-mass coordinates of the star spot. Simulations and experiments demonstrate the feasibility and effectiveness of the method. The fitting error is less than 0.3 pixels for the angular velocity vector [10°/s,0°/s,10°/s] and exposure time 200ms, which is an improvement of at least 0.1 pixel compared to previous studies.

A Spatial–Temporal Star Spots Extraction for High Dynamics Star Sensors

In this article, we consider the problem of extracting star spots for traditional star sensors with short exposure time under high dynamic conditions (>5°/s). Under this setting, the signal-to-noise ratio (SNR) of star spots decreases visibly, resulting in less star information being presented, making most of star spots undetectable. We propose a spatial-temporal star spots extraction for this task. According to the constraints of angular distance and kinematic of stars in multi-frame images, a detection method based on spatial-temporal filtering is first proposed to detect star spots with low SNR. It establishes a star spot observation by using the correlation between its predicted image and measured image, which fuses the measurement information of the star and the motion information of the star sensor, and detects star spots based on the maximum a posteriori (MAP). Then, according to the imaging characteristics that the imaging region of a star spot can be regarded as a rectangle, an extraction method based on hypothesis-verification is developed to completely extract pixels of the star spot. It establishes the classification probability of a pixel by the multi-layer Gaussian mixture model, and extract pixels according to the maximum likelihood estimation (MLE) of the star image. Experiments demonstrate the extraction capability and accuracy of the method. In conclusion, there is a promising application value for the method to improve the attitude estimation accuracy and update rate of star sensor under high dynamic conditions.

Suppression of dc‐offset current in ac‐link of dual‐active‐bridge dc‐dc converter based on triple‐phase‐shift optimal control

AbstractWhen dual‐active‐bridge dc‐dc converter (DAB) with energy storage load operates in a wide voltage range and high dynamic condition, the mismatch of primary and secondary side voltages will lead to high current stress and loss, and the dc‐offset current in the high‐frequency ac link will lead to magnetic saturation of magnetic components, which will damage the devices in serious cases. Therefore, aiming at the operation of DAB in a wide voltage range, a triple‐phase‐shift (TPS) optimal control strategy is adopted, and the phase shift angles of the bridges are adjusted according to the voltage ratio, so as to optimize the electrical stress and loss. What is more, the cause and mechanism of dc‐offset current in the ac‐link are analysed. Based on the TPS optimal strategy, the static dc‐offset current is suppressed with the low‐bandwidth detection of the offset current and the dynamic dc‐offset current is suppressed with the planning the current trajectory. A small‐power prototype is built, and the effectiveness of the TPS optimal control and the static and dynamic dc‐offset current suppression is verified.

Restoration of motion-blurred star images with elliptical star streaks

The restoration of motion-blurred star images under high dynamic conditions is important for the high-precision attitude measurement of star sensors. Through motion modelling analysis, it is found that the streak of the imaged star point (star streak) is an elliptical arc. However, existing star image restoration methods are only suitable for the case where the star streak is a straight line. For this reason, a star image restoration algorithm for elliptical star streaks is proposed in this paper. First, the elliptical star streak is transformed into a circular star streak by projective transformation. Then, the circular star streak is transformed into a straight star streak by polar coordinate transformation. Finally, the restored original star image is obtained by restoration methods for straight star streaks and coordinate inverse transformation. At the same time, the algorithm is further optimized by subdividing the polar coordinates. The experiment shows that the proposed algorithm is effective and the restoration accuracy is at the same level as that of existing star image restoration methods for straight star streaks.

Retracted] Motion Control and Tracking Control of UAV Based on Adaptive Sensor

In order to meet the requirements of UAV motion control and tracking control, an adaptive sensor‐based technology is proposed. The main content of the technology is based on the mathematical model of the adaptive sensor, through the quaternion attitude update model, using nonlinear attitude SVDCK filtering and dynamic adaptive adjustment factors and other technologies, and finally through simulation experiments and analysis to build the research means of UAV motion control and tracking control system. The experimental results show that the roll Angle, pitch Angle, and yaw Angle of SVDCKF are 1.703, 1.972, and 1.928, respectively. By adjusting the dynamic adaptive factor, the attitude‐filtering algorithm reduces the error of the attitude solution and improves the robustness of the attitude solution under high dynamic conditions. Conclusion. The technology research based on adaptive sensor can meet the requirements of UAV motion control and tracking control.

A Super-High-Accuracy Attitude Measurement Method of SINS Based on PWQHN Algorithm in the High-Dynamic Maneuver Environment

To reduce noncommutative error (NCE) and improve the attitude-update accuracy in the attitude algorithm of the strapdown inertial navigation system (SINS), we assume that angular rate is represented as a polynomial to deduce the relationship between the angular increment sampling sequence and the derivatives of the quaternion. Subsequently, a high-order numerical solution of the quaternion differential equation is obtained by substituting the derivatives of the quaternion into its Taylor expansion. Generally, the quaternion will be constructed with a series of angular increment samples in a constant updating interval. Furthermore, the piecewise quaternion high-order numerical (PWQHN) algorithm is deduced by reconstructing quaternion in each sampling interval to ulteriorly improve attitude accuracy. The simulation results indicate that the PWQHN algorithm is stable in two kinds of simulation conditions. In the coning motion condition, PWQHN algorithm has the highest accuracy. In the high-dynamic condition, the extreme accuracy of PWQHN is not significantly higher than other algorithms. However, PWQHN can still output accurate attitude in the situation without many angular increment subsamples.

IC-GVINS: A Robust, Real-Time, INS-Centric GNSS-Visual-Inertial Navigation System

Visual navigation systems are susceptible to complex environments, while inertial navigation systems (INS) are not affected by external factors. Hence, we present IC-GVINS, a robust, real-time, INS-centric global navigation satellite system (GNSS)-visual-inertial navigation system to fully utilize the INS advantages. The Earth rotation has been compensated in the INS to improve the accuracy of high-grade inertial measurement units (IMUs). To promote the system robustness in high-dynamic conditions, the precise INS information is employed to assist the feature tracking and landmark triangulation. With a GNSS-aided initialization, the IMU, visual, and GNSS measurements are tightly fused in a unified world frame within the factor graph optimization framework. Dedicated experiments were conducted in the public vehicle and private robot datasets to evaluate the proposed method. The results demonstrate that IC-GVINS exhibits superior robustness and accuracy in complex environments. The proposed method with the INS-centric architecture yields improved robustness and accuracy compared to the state-of-the-art methods.

Использование смешанного и гибридного обучения в современной российской педагогической практике

In the conditions of high dynamics of digitalization of all spheres of public life, the active use of blended and hybrid learning in educational practice is of particular importance. These phenomena have been introduced into the Russian education system relatively recently, which requires their careful consideration and detailed analysis. In the course of the study, the author of the article found that in the conditions of Russian pedagogical practice today there is no common understanding of the term “blended learning”, as there is no specifics in the differentiation of blended and hybrid learning, which gives rise to frequent substitution of concepts and the lack of detailing the difference in these phenomena. At the same time, the analysis showed that blended and hybrid learning are, although similar, but still not identical processes. In particular, hybrid learning involves the priority use of online formats, as well as the parallel, rather than sequential, implementation of innovative digital and traditional educational technologies, so that the difference between online participants and face-to-face participants is practically erased. The study also revealed the advantages, disadvantages and main problems in the implementation of blended and hybrid learning in Russia; emphasis is placed on the transformation of the teacher’s functions in the context of the transition to mixed forms. In particular, it has been established that it is not teaching that becomes the dominant function, but the organization and management of the pedagogical process, its methodological support using the synthesis of various educational technologies, advising students at all stages of mastering educational programs.

ЗАСТОСУВАННЯ ХОЛІСТИЧНОГО ПІДХОДУ В ПРОЦЕСІ ЗАБЕЗПЕЧЕННЯ ЕКОНОМІЧНОЇ БЕЗПЕКИ ПІДПРИЄМСТВА

The current orientation of security entities to the detection of internal threats and the subsequent elimination of the consequences of their implementation is characterized by insufficient efficiency in the conditions of high dynamics of the external environment. The application of a holistic approach in the process of ensuring the economic security of the enterprise involves the formation of a holistic view of the set of processes that take place in the internal and external environment of the enterprise. The research is aimed at the application of a holistic approach in the process of ensuring the economic security of the enterprise in the part of conducting a trend analysis in order to characterize the impact of the main factors on the labor market. In order to determine the main trends in the development of the labor market, which have a significant impact on the economic security of the enterprise, the following methods are used: induction and deduction, comparison and systematization – in the study of the essential characteristics of the holistic approach; synthesis and analysis – to determine the main trends in the development of the labor market; morphological analysis – to specify the degree of influence of individual changes in the labor market on the economic security of the enterprise; graphic – for visual presentation of theoretical and methodical material; abstract-logical – for theoretical generalizations and research conclusions. A systematic trend analysis with the widest possible horizons of the information field allows you to identify the facts of the emergence and change of threats and the emergence of new market opportunities that will contribute to the achievement of corporate goals. The practical application of theoretical developments was implemented in relation to the labor market as a component of the external information field, which made it possible to identify and characterize the factors that most significantly affect the economic security of the enterprise and should be taken into account for the implementation of preventive protective measures. It is substantiated that security subjects should take into account the following parameters of the national labor market, which are associated with: signs of a demographic crisis (decrease in the number of the population due to an increase in mortality, a decrease in the birth rate, a decrease in the average life expectancy and a deterioration in the age structure); workforce reduction; gaps in the development of human capital; high level of unemployment; consequences of COVID-19; a significant number of refugees and internally displaced persons due to the continuation of military aggression on the part of the Russian Federation.

Constant hue loci in different color spaces for stimuli in Rec. 2020 color gamut and HDR conditions.

Hue is an important attribute for characterizing a color stimulus, which is also an output in various color spaces. The investigations on the hue linearity and constant hue loci for different color spaces were generally conducted using conventional CRT displays or surface color samples, in which the color stimuli were within small color gamuts and viewed under standard dynamic range conditions. With the development of imaging technologies, the hue linearity and constant hue loci need to be investigated for wide color gamuts and high dynamic range conditions, which is critically important for image processing (e.g., gamut mapping and tone mapping). In this study, we carefully carried out a hue matching experiment using high-power LED devices. The color stimuli almost reached Rec. 2020 color gamut with the luminance above the diffuse white luminance (i.e., a high dynamic range condition). The results suggested that the hue linearity of ICTCP color space was the best among the nine color spaces. Twenty-one constant hue loci were derived for each of these nine color spaces, which can be used for hue correction when performing image processing and to further revise the color spaces.

Exploring Event Camera-Based Odometry for Planetary Robots

Due to their resilience to motion blur and high robustness in low-light and high dynamic range conditions, event cameras are poised to become enabling sensors for vision-based exploration on future Mars helicopter missions. However, existing event-based visual-inertial odometry (VIO) algorithms either suffer from high tracking errors or are brittle, since they cannot cope with significant depth uncertainties caused by an unforeseen loss of tracking or other effects. In this work, we introduce EKLT-VIO, which addresses both limitations by combining a state-of-the-art event-based frontend with a filter-based backend. This makes it both accurate and robust to uncertainties, outperforming event- and frame-based VIO algorithms on challenging benchmarks by 32%. In addition, we demonstrate accurate performance in hover-like conditions (outperforming existing event-based methods) as well as high robustness in newly collected Mars-like and high-dynamic-range sequences, where existing frame-based methods fail. In doing so, we show that event-based VIO is the way forward for vision-based exploration on Mars.

Forming managers’ exploitation and exploration from the interplay of managers’ formal and informal networks in China: a moderated mediation model

ABSTRACT Managerial networks represent a crucial factor affecting managers’ exploitation and exploration. However, the theoretical mechanism linking managerial networks to managers’ exploitation and exploration remains poorly understood. Thus, we focus on the interplay of managers’ formal and informal networks and develop a moderated mediation model to examine the relationship between managerial networks and managers’ exploitation and exploration. An analysis of 269 managers working in 73 Chinese enterprises reveals that the consistency of managers’ formal and informal network has a positive indirect relationship with managers’ exploitation and exploration via knowledge creation. Environmental dynamism moderates the strength of this mediated relationship such that the mediated effects are weaker under conditions of high environmental dynamism and stronger under conditions of low environmental dynamism. By exploring this theoretical mechanism, this study contributes to the literature concerning exploitation and exploration at the managerial level and systematically analyzes managers’ relationship networks and behaviours based on social information processing theory.

Информационная модель перспективной базы данных в системе управления телекоммуникационной сетью Carrier Ethernet

Purpose: To develop an informational model of a promising database in the system of management of telecommunication network which uses Carrier Ethernet technology for to ensure the efficiency of storage, access and update of data on the telecommunication network functioning that will allow to increase the operativeness of implementation of OAM (Operation, Administration and Management) control-management built-in processes at timely and reasonable decision-making on telecommunication network management in conditions of high dynamics of changes in the network state as well as in view of Carrier Ethernet technology specificities. Thus, in order to provide services of given quality, an information model of database in telecommunication network management system has been created with indication of information main sources which’re represented by subsystems and models of telecommunications network management system in accordance with the previously developed three-level conceptual model. Also, to achieve the stated goal a logical structure of the obtained database information model on the example of domain objects has been developed. Methods: Fundamentals of complex process management theory; theory of multi-agent systems of management of distributed object; theory of systems of information storage and presentation; object-oriented projection method; set-theoretic approach for the description of data set about a control object. Results: The obtained informational model of database and the developed logical three-level structure of functioning are described verbally and mathematically. The evaluation of functioning of the proposed logical structure of the database in the system of telecommunication network management using Carrier Ethernet technology and OAM mechanisms is given. The directions of further research towards development of the models of major processes of collection, processing and provision of data on functioning of subsystems in the system of telecommunications network management are proposed. Practical significance: The developed informational model of database in the system of telecommunications network management differs from well-known ones by the possibility of accounting for and including in the data of the implementation of the complex of unique models of functioning and management of Carrier Ethernet telecommunication network and the mechanisms of OAM management, that were previously obtained by the authors and represent subsystems in the telecommunications network management system with the use of Carrier Ethernet technology possibilities.

A method for improving the efficiency of integrated processing of Earth remote sensing data in solving problems of spatial objects monitoring

A method is proposed for improving the efficiency of the system for complex processing of data obtained by remote sensing of the Earth in conditions of limited resources in solving problems of spatial objects monitoring. The efficiency of the system functioning is increased through the rational allocating its resources according to the tasks to be solved, taking into account the priority solution of those that have a higher value of relative importance coefficient. It is also proposed to improve the efficiency of solving each of the tasks on the basis of exclusion from the work plans for solving those resources that are overloaded with other tasks, but at the same time make an insignificant contribution to the formation of an integral result. The simulation results show that the use of the proposed method for improving the efficiency of the system functioning for complex processing of Earth remote sensing data in conditions of limited resources, when solving problems of monitoring spatial objects, makes it possible to ensure the required quality of managerial decisions, especially in conditions of high dynamism of changing the monitoring objects characteristics.

A Technique of the Distributed Information Systems Control Method Choice under the High Network Dynamics Conditions

Purpose of research. The purpose of this study is to select a method for managing a distributed system, which, based on known parameters, would reduce the consumption of resources of computing devices. The resource of an information system is understood as the probability of failure-free operation (reliability function), which degrades over time for each node, the faster, the higher its workload.Methods. Considering that with high dynamics of the edge layer of the network, the frequency of system reconfigurations becomes relatively high, and the need for reconfigurations is unpredictable, reducing the total time spent on reconfigurations makes it possible to increase the time spent on solving functional computational problems of the system and thereby reduce the load of nodes. The reconfiguration time can be reduced both by reducing the time for detecting a failure in a distributed system, and by reducing the new configuration forming time. In this paper, a method for reducing the time of the failure detection is considered. The analysis of the applicability of system control methods (centralized, with a distributed leader, decentralized) is based on the obtained analytical estimates of the time the system detects a failure under control conditions using one method or another. A numerical experiment makes it possible to identify areas of system parameters, where it is preferable to use the method with a distributed leader.Results. The main result of this work is a methodology for choosing a method for managing distributed information systems in conditions of high dynamics of the network infrastructure, focused on reducing the consumption of resources of computing devices.Conclusion. System reconfiguration time can be shortened by choosing the most appropriate control method. Thus, the time allotted for solving the functional tasks of the application increases, the workload of the computational nodes decreases, and, therefore, the FBG values increase over the planning horizon.

GNSS Signal Acquisition Algorithm Based on Two-Stage Compression of Code-Frequency Domain

The recently-emerging compressed sensing (CS) theory makes GNSS signal processing at a sub-Nyquist rate possible if it has a sparse representation in certain domain. The previously proposed code-domain compression acquisition algorithms have high computational complexity and low acquisition accuracy under high dynamic conditions. In this paper, a GNSS signal acquisition algorithm based on two-stage compression of the code-frequency domain is proposed. The algorithm maps the incoming signal of the same interval to multiple carrier frequency bins and overlaps the mapped signal that belongs to the same code phase. Meanwhile, the code domain compression is introduced to the preprocessed signal, replacing circular correlation with compressed reconstruction to obtain Doppler frequency and code phase. Theoretical analyses and simulation results show that the proposed algorithm can improve the frequency search accuracy and reduce the computational complexity by about 50% in high dynamics.

Johnson-Cook model parameters determination for 11% and 14% Mn-Steel

The behaviour of high-manganese steel under large strains and different strain rates needs to be investigated to predict its response to various dynamic loading conditions including impact. An empirical constitutive relation developed by Johnson and Cook (JC) is applied at high strain rate and dynamic loading conditions to determine the flow stress and material strength. The deformation behaviour of two high-manganese steel cylindrical specimens (11% and 14% Mn-content) was studied using uniaxial tensile tests, compression tests at various strain rates and finite element (FE) simulation. These tests were conducted at room temperature to examine the effects of strain rate, material plasticity and strain hardening to ultimately determine the JC model parameters. Fracture appearance of tensile test specimens was also studied using optical microscopy and SEM. Results showed that 11%Mn-steel exhibited more toughness, ductility and strain hardening than 14% Mn-steel. The JC model parameters have been evaluated and represented in tabular form. Tensile tests have been compared with recent published works. Good agreement between the results has been observed.