scholarly journals A Novel Space Large Deployable Paraboloid Structure with Power and Communication Integration

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Tao Zheng ◽  
Zheng Fei ◽  
Xi Rui ◽  
Lide Yan
Keyword(s):  
Lower Surface ◽  
Control Mode ◽  
Solar Array ◽  
Tracking Accuracy ◽  
Space Applications ◽  
Physical Size ◽  
Ground Station ◽  
Satisfactory Performance ◽  
Tracking Process ◽  
The One

The combination of a solar array and a communication antenna can reduce the entire mass, physical size, and cost in space applications. Currently, related studies mainly focus on the combination of the two structures on the one flat plate structure (FPS). Compared with the FPS, a paraboloid structure has a lower surface density and higher conversion efficiency. Therefore, a novel space large deployable paraboloid structure with power and communication integration (SSPCI) is proposed and designed in detail, for spacecraft on a sun synchronous earth orbit; it consists of a cable mesh membrane reflector (CMMR), an energy conversion device (ECD), and a three-extensible-rod (TER) pointing mechanism. To achieve the goal of integrating power and communication, the TER pointing mechanism drives the CMMR/ECD to track the sun in the sunshine region or to turn to face the ground station/other target in the Earth’s shadow region. Then, through simulation analyses of the deploying process, static force at a limit orientation, and sun tracking process of the SSPCI, it is proved that the SSPCI is feasible and has satisfactory performance. Finally, deploying experiments of the folded hoop of the CMMR and sun tracking experiments of the TER pointing mechanism on the ground were carried out successfully, which proves that the folded hoop can be deployed successfully with fairly high deploying dependability, and the TER pointing mechanism is feasible for the SSPCI from the mechanism principle and the control mode in space applications indirectly. Moreover, the tracking accuracy of the TER pointing mechanism is estimated to be within ±0.4° although the machining precision of its components is not high.

scholarly journals Multiple Drone Navigation and Formation Using Selective Target Tracking-Based Computer Vision

Electronics ◽  
2021 ◽  
Vol 10 (17) ◽  
pp. 2125
Author(s):  
Jatin Upadhyay ◽  
Abhishek Rawat ◽  
Dipankar Deb
Keyword(s):  
Computer Vision ◽  
Target Tracking ◽  
Line Of Sight ◽  
Tracking Accuracy ◽  
Ground Station ◽  
Image Center ◽  
Aerial Vehicle ◽  
Using Data ◽  
The One ◽  
The Individual

Autonomous unmanned aerial vehicles work seamlessly within the GPS signal range, but their performance deteriorates in GPS-denied regions. This paper presents a unique collaborative computer vision-based approach for target tracking as per the image’s specific location of interest. The proposed method tracks any object without considering its properties like shape, color, size, or pattern. It is required to keep the target visible and line of sight during the tracking. The method gives freedom of selection to a user to track any target from the image and form a formation around it. We calculate the parameters like distance and angle from the image center to the object for the individual drones. Among all the drones, the one with a significant GPS signal strength or nearer to the target is chosen as the master drone to calculate the relative angle and distance between an object and other drones considering approximate Geo-location. Compared to actual measurements, the results of tests done on a quadrotor UAV frame achieve 99% location accuracy in a robust environment inside the exact GPS longitude and latitude block as GPS-only navigation methods. The individual drones communicate to the ground station through a telemetry link. The master drone calculates the parameters using data collected at ground stations. Various formation flying methods help escort other drones to meet the desired objective with a single high-resolution first-person view (FPV) camera. The proposed method is tested for Airborne Object Target Tracking (AOT) aerial vehicle model and achieves higher tracking accuracy.

scholarly journals Attention Modulated Multiple Object Tracking with Motion Enhancement and Dual Correlation

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 266 ◽  
Author(s):  
Yifeng Wang ◽  
Zhijiang Zhang ◽  
Ning Zhang ◽  
Dan Zeng
Keyword(s):  
Object Tracking ◽  
Multiple Object Tracking ◽  
Tracking Accuracy ◽  
Feature Maps ◽  
Backbone Networks ◽  
Multiple Object ◽  
The Arts ◽  
Training Stage ◽  
The One ◽  
Baseline State

The one-shot multiple object tracking (MOT) framework has drawn more and more attention in the MOT research community due to its advantage in inference speed. However, the tracking accuracy of current one-shot approaches could lead to an inferior performance compared with their two-stage counterparts. The reasons are two-fold: one is that motion information is often neglected due to the single-image input. The other is that detection and re-identification (ReID) are two different tasks with different focuses. Joining detection and re-identification at the training stage could lead to a suboptimal performance. To alleviate the above limitations, we propose a one-shot network named Motion and Correlation-Multiple Object Tracking (MAC-MOT). MAC-MOT introduces a motion enhance attention module (MEA) and a dual correlation attention module (DCA). MEA performs differences on adjacent feature maps which enhances the motion-related features while suppressing irrelevant information. The DCA module focuses on decoupling the detection task and re-identification task to strike a balance and reduce the competition between these two tasks. Moreover, symmetry is a core design idea in our proposed framework which is reflected in Siamese-based deep learning backbone networks, the input of dual stream images, as well as a dual correlation attention module. Our proposed approach is evaluated on the popular multiple object tracking benchmarks MOT16 and MOT17. We demonstrate that the proposed MAC-MOT can achieve a better performance than the baseline state of the arts (SOTAs).

scholarly journals Research on Target Tracking Algorithm Based on Siamese Neural Network

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Haibo Pang ◽  
Qi Xuan ◽  
Meiqin Xie ◽  
Chengming Liu ◽  
Zhanbo Li
Keyword(s):  
Neural Network ◽  
Target Tracking ◽  
Evaluation Criteria ◽  
Attention Mechanism ◽  
Tracking Algorithm ◽  
Temporal Attention ◽  
Tracking Accuracy ◽  
Current Frame ◽  
Tracking Process ◽  
Recognition Ability

Target tracking is a significant topic in the field of computer vision. In this paper, the target tracking algorithm based on deep Siamese network is studied. Aiming at the situation that the tracking process is not robust, such as drift or miss the target, the tracking accuracy and robustness of the algorithm are improved by improving the feature extraction part and online update part. This paper adds SE-block and temporal attention mechanism (TAM) to the framework of Siamese neural network. SE-block can refine and extract features; different channels are given different weights according to their importance which can improve the discrimination of the network and the recognition ability of the tracker. Temporal attention mechanism can update the target state by adjusting the weights of samples at current frame and historical frame to solve the model drift caused by the existence of similar background. We use cross-entropy loss to distinguish the targets in different sequences so that their distance in the feature domains is longer and the features are easier to identify. We train and test the network on three benchmarks and compare with several state-of-the-art tracking methods. The experimental results demonstrate that the algorithm proposed is superior to other methods in tracking effect diagram and evaluation criteria. The proposed algorithm can solve the occlusion problem effectively while ensuring the real-time performance in the process of tracking.

Dynamic Modeling for a Flexible Spacecraft With Solar Arrays Composed of Honeycomb Panels and Its Proportional–Derivative Control With Input Shaper

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Lun Liu ◽  
Dengqing Cao
Keyword(s):  
Dynamic Model ◽  
Vibration Suppression ◽  
Hybrid Control ◽  
Flexible Spacecraft ◽  
Solar Array ◽  
Pd Controller ◽  
Pd Control ◽  
Solar Arrays ◽  
Attitude Maneuver ◽  
The One

A high-precision dynamic model of a flexible spacecraft installed with solar arrays, which are composed of honeycomb panels, is established based on the nonconstrained modes of flexible appendages (solar arrays), and an effective cooperative controller is designed for attitude maneuver and vibration suppression by integrating the proportional–derivative (PD) control and input shaping (IS) technique. The governing motion equations of the system and the corresponding boundary conditions are derived by using Hamiltonian Principle. Solving the linearized form of those equations with associated boundaries, the nonconstrained modes of solar arrays are obtained for deriving the discretized dynamic model. Applying this discretized model and combining the IS technique with the PD controller, a hybrid control scheme is designed to achieve the attitude maneuver of the spacecraft and vibration suppression of its flexible solar arrays. The numerical results reveal that the nonconstrained modes of the system are significantly influenced by the spacecraft flexibility and honeycomb panel parameters. Meanwhile, the differences between the nonconstrained modes and the constrained ones are growing as the spacecraft flexibility increases. Compared with the pure PD controller, the one integrating the PD control and IS technique performs much better, because it is more effective for suppressing the oscillation of attitude angular velocity and the vibration of solar array during the attitude maneuver, and reducing the residual vibration after the maneuver process.

ROBUST SONIC LOG TRACKING USING A MULTI-RESOLUTION APPROACH

2021 ◽  
Author(s):  
Ting Lei ◽  
◽  
Michiko Hamada ◽  
Adam Donald ◽  
Takeshi Endo ◽  
...  
Keyword(s):  
Sudden Change ◽  
Processing Technique ◽  
Tracking Algorithm ◽  
Signal Loss ◽  
Tracking Accuracy ◽  
Signal Processing Technique ◽  
Waveform Data ◽  
Sonic Log ◽  
Tracking Process ◽  
Sonic Logs

Borehole acoustic logging is an acquisition method that is regarded as the most efficient and reliable method to measure subsurface rock elastic property. It plays an important role in both well construction and reservoir evaluation. The acquisition is carried out downhole by firing a transducer and then collecting waveforms at an array of receivers. A signal processing technique such as the slowness-time-coherence method is used to process array waveform data to resolve slownesses from different arrivals. To label these slowness values, a classification algorithm is then required to first determine if a primary (P) or a secondary (S) arrival exists or not, and then label out the existing ones at each depth of the entire logging interval to deliver continuous compressional and shear slowness logs. Such a process is referred as automatic sonic log tracking process. Clearly, it is of great importance to be able to track log as accurately as possible. Traditional approaches either use predefined slowness or arrival time boundary to distinguish them or treats slowness peaks in consecutive depths like “moving particles” and use a particle tracking algorithm to estimate their trace. However, such a tracking algorithm is often challenged by a sudden change in formation types at bed boundary, fine-scale heterogeneity, downhole logging noise, as well as unpredicted signal loss due to bad borehole shape or gas influx. Consequently, the tracking process is often a tricky task that requires heavy manual quality control and relabeling process, which poses significant bottleneck for a timely delivery of sonic logs for downstream petrophysical and geomechanical applications. In this paper, we propose a new physical based multi-resolution tracking algorithm that can improve the robustness of the tracking process. The new algorithm is inspired by the fact that different resolution sonic logs can sense different rock volumes and therefore response differently to a thin layer or an interval with bad borehole conditions. It works by grouping slowness-time peaks with different resolutions to form clusters, which are then tracked by the connecting with its neighboring depths. As different resolution slownesses are physically constrained by the convolution response of heterogeneous layers, the cluster-based multi-resolution tracking approach exhibits better logging depth continuity than the traditional single-resolution methods. Outliers due to noise can be confidently avoided. Finally, remaining gaps due to shoulder bed boundary can be patched by a convolution constrained optimization process from coherences from different resolutions. This new approach is therefore referred as a multi-resolution approach and can significantly improve sonic log tracking accuracy than the single resolution approach. This new algorithm has been tested on several sonic logging field data and demonstrates robust tracking performance of sonic P&S logs. Additionally, with the multi-resolution processing, sonic logs with different resolution can be reliably obtained and a high-quality high-resolution sonic log can also be automatically delivered, which can then be used to match resolution of other petrophysical logs for various types of interpretation.

scholarly journals Experimental Study on the Effects of Coolants on Surface Quality and Mechanical Properties of Micromilled Thin-Walled Elgiloy

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1497 ◽  
Author(s):  
Da Qu ◽  
Peng Zhang ◽  
Jiadai Xue ◽  
Yun Fan ◽  
Zuhui Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Surface Quality ◽  
Lower Surface ◽  
Work Piece ◽  
Dry Machining ◽  
Core Component ◽  
The Core ◽  
Thin Walled ◽  
The One

In this study, minimum quantity coolant/lubrication (MQCL) is found to have significant impact on the surface quality and mechanical properties of the micromilled thin-walled work piece that is the core component of an aeroaccelerometer. Three kinds of coolants were used in the micromilling process to analyze their effects on surface quality and mechanical properties of the component. The experiment results show that an appropriate dynamic viscosity of coolant helps to improve surface roughness. The high evaporation rate of the coolants can enhance the cooling performance. Comparing with the dry machining case, MQCL has better performance on improving tool wear, surface quality, and mechanical properties of the micromilled work piece. It yielded up to 1.4–10.4% lower surface roughness compared with the dry machining case in this experiment. The machined work piece with the best mechanical properties and the one with the worst mechanical properties appeared in the ethyl alcohol and the dry machining case, respectively. The reasons for deteriorating surface quality and mechanical properties in dry machining cases are also analyzed. For improving the micromilling process, the penetration and cooling effect of the coolants are more important. This paper gives references to obtain better service performance of the component by improving the micromilling process.

Solar Array and Battery Sizing for a Photovoltaic Building in Malaysia

2013 ◽  
Vol 64 (4) ◽  
Author(s):  
Hadi Nabipour Afrouzi ◽  
Saeed Vahabi Mashak ◽  
Zulkurnain Abdul-Malek ◽  
Kamyar Mehranzamir ◽  
Behnam Salimi
Keyword(s):  
Minimum Cost ◽  
Solar Irradiation ◽  
Solar Array ◽  
Pv System ◽  
Pv Array ◽  
Pv Module ◽  
Mathematical Equations ◽  
The One ◽  
The Right ◽  
The Cost

Renewable energy plays an important role in the national energy policy especially in reducing greenhouse gas emissions. For a photovoltaic (PV) system, one important consideration is the cost of the system. One needs to select the best PV array from a range of selection, that is, the one which is the most efficient and with a best price. This article illustrates a method to compute the size and cost of a required PV array, and then after to compute the required battery for the case of a photovoltaic building in Malaysia. The computation is simulated using Matlab integrated with suitable mathematical equations. The generated current and power of the PV array are calculated for daily solar irradiation in Malaysia. The computation enables the user to quickly compute the initial cost needed to be spent if a given PV system is to be installed. A typical building requiring 12 kWh daily energy with 6 kW peak demand load was shown to need at least 114 solar modules at a cost of about RM53k. It is noted that the main cost of the whole PV system is mainly contributed by the cost of the chosen PV array. Hence, the right choice of a PV module is vital in achieving the minimum cost.

scholarly journals The Strategy of Inverter Seamless Mode Switching in Master-Slave Independent Micro-grid

2018 ◽  
Vol 160 ◽  
pp. 04003
Author(s):  
Hanhong Jiang ◽  
Yao Lu ◽  
You Wu ◽  
Yi Wang
Keyword(s):  
Control Mode ◽  
Mode Switching ◽  
Improvement Strategy ◽  
Uninterruptible Power Supply ◽  
Grid Connection ◽  
Experiment Verification ◽  
Simulation And Experiment ◽  
Micro Grid ◽  
Uninterruptible Power ◽  
The One

In order to realize the uninterruptible power supply in the master-slave independent micro-grid system, the micro-grid inverter needs to realize the mode switching of the grid-connection/grid-disconnection. How to reduce the transient oscillation during switching, so as to effectively achieve seamless mode switching is a key issue to be solved. In this paper, a typical master-slave control independent micro-grid is used as an example, the strategy of mode switching is improved in two aspects. On the one hand, the state-following algorithm is adopted to improve the switching strategy of the outer loop. On the other hand, the current inner loop is taken by the H∞ robust controller to improve the robustness of the controller. Compared with the traditional PI control mode switching, this paper illustrates the feasibility of the proposed strategy through the simulation and experiment verification. The improvement strategy in this paper can effectively reduce the voltage and current oscillation during mode switching.

scholarly journals The Hipparcos Mission: Will it be a Scientific Success?

1990 ◽  
Vol 123 ◽  
pp. 27-33
Author(s):  
M.A.C. Perryman
Keyword(s):  
Routine Data ◽  
High Energy ◽  
High Energy Particle ◽  
Scientific Success ◽  
Ground Station ◽  
Solar Arrays ◽  
Transfer Orbit ◽  
The One ◽  
Scientific Value ◽  
Data Reductions

AbstractThe Hipparcos astrometry satellite was launched on 8 August 1989, and after spacecraft and payload commissioning, commenced the routine data acquisition phase on 26 November 1989. Having failed to reach its planned geostationary orbit, major revisions in the mission operations were made, and the post-launch expectations of the mission were strongly degraded with respect to the original goals - principally due to the greatly reduced observational efficiency (caused by the lack of ground station coverage) and the anticipated degraded mission lifetime (as a result of the high-energy particle degradation of the solar arrays in the geostationary transfer orbit).The final astrometric accuracies attainable by the Hipparcos mission will be influenced by the spacecraft and payload performances on the one hand, and by fraction of useful data and mission lifetime on the other. It will be shown that the elemental observational measurements correspond very closely to the predictions, and the data recovery fraction now stands at around 60–70 per cent, so that the ultimate scientific value of the Hipparcos results will be tied directly to the satellite lifetime. A measurement duration of at least 18 months is mandatory if the astrometric parameters (parallaxes and proper motions) are to be decoupled through the data reductions procedures. A somewhat longer lifetime (2.5–3 years) is necessary in order to reduce the errors on the astrometric parameters to the astrophysically-significant accuracies of around 2 milli-arcsec.It will be shown that the present indications of the satellite performances, and the significant progress already made in the data reductions, indicate that the difficulties of the ‘revised’ Hipparcos mission have been largely overcome, and that these target accuracies could still be achievable.

scholarly journals Tackling the triple threats of childhood malnutrition

BMC Medicine ◽  
2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Martha Mwangome ◽  
Andrew M. Prentice
Keyword(s):  
Micronutrient Deficiencies ◽  
Obese Children ◽  
Double Burden ◽  
Physical Size ◽  
Obesity Epidemic ◽  
Nutritional Health ◽  
Hidden Hunger ◽  
The One ◽  
The Impact ◽  
Poor Nutrition

AbstractThe term ‘double burden of malnutrition’ is usually interpreted in terms of the physical status of children: stunted and wasted children on the one hand and overweight/obese children on the other. There is a third category of malnutrition that can occur at either end of the anthropometric spectrum or, indeed, in children whose physical size may be close to ideal. This third type is most commonly articulated with the phrase ‘hidden hunger’ and is often illustrated by micronutrient deficiencies; thus, we refer to it here as ‘undernutrition’. As understanding of such issues advances, we realise that there is a myriad of factors that may be influencing a child’s road to nutritional health. In this BMC Medicine article collection we consider these influences and the impact they have, such as: the state of the child’s environment; the effect this has on their risk of, and responses to, infection and on their gut; the consequences of poor nutrition on cognition and brain development; the key drivers of the obesity epidemic across the globe; and how undernourishment can affect a child’s body composition. This collection showcases recent advances in the field, but likewise highlights ongoing challenges in the battle to achieve adequate nutrition for children across the globe.

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