Raft attitude control and elastic deformation suppression technique for large-scale floating raft air spring mounting system

2021 ◽  
pp. 107754632110388
Author(s):  
Yuanran Qiu ◽  
Wei Xu ◽  
Wenjun Bu ◽  
Wenzheng Qin
Keyword(s):  
Elastic Deformation ◽  
Attitude Control ◽  
Large Scale ◽  
Relative Displacement ◽  
Deformation Monitoring ◽  
Air Spring ◽  
Floating Raft ◽  
Control Precision ◽  
Suppression Technique ◽  
Pressure Parameter

The structure of floating rafts-equipped vessels will be inevitably undermined due to application of large-scale designs. When encountering strong external disturbances, not only the rafts will deviate from the original balanced position but also greater elastic deformation will be generated, which may lead to the relative displacement between devices on rafts and endanger the operation safety of equipment. In this study, a class of raft elastic deformation monitoring and discrimination methods is put forward via analyzing the features of large-scale raft elastic deformation. Air springs layout is optimized through finite element method (FEM). A flexible raft control responding model is established and a novel raft elastic deformation suppression technique is proposed based on air spring pressure parameter identification that adjusts the air spring pressure distribution. The experimental results indicate that this technique can effectively control the attitude of the rafts and reduce elastic deformation, leading to a largely improved control precision and a faster convergence speed of the raft.

scholarly journals Subsidence Monitoring of Fill Area in Yan’an New District Based on Sentinel-1A Time Series Imagery

2021 ◽  
Vol 13 (15) ◽  
pp. 3044
Author(s):  
Mingjie Liao ◽  
Rui Zhang ◽  
Jichao Lv ◽  
Bin Yu ◽  
Jiatai Pang ◽  
...  
Keyword(s):  
Time Series ◽  
Large Scale ◽  
Ground Deformation ◽  
Dynamic Change ◽  
Deformation Monitoring ◽  
Chinese Loess Plateau ◽  
Ground Subsidence ◽  
Shanxi Province ◽  
Environment Change ◽  
Loess Area

In recent years, many cities in the Chinese loess plateau (especially in Shanxi province) have encountered ground subsidence problems due to the construction of underground projects and the exploitation of underground resources. With the completion of the world’s largest geotechnical project, called “mountain excavation and city construction,” in a collapsible loess area, the Yan’an city also appeared to have uneven ground subsidence. To obtain the spatial distribution characteristics and the time-series evolution trend of the subsidence, we selected Yan’an New District (YAND) as the specific study area and presented an improved time-series InSAR (TS-InSAR) method for experimental research. Based on 89 Sentinel-1A images collected between December 2017 to December 2020, we conducted comprehensive research and analysis on the spatial and temporal evolution of surface subsidence in YAND. The monitoring results showed that the YAND is relatively stable in general, with deformation rates mainly in the range of −10 to 10 mm/yr. However, three significant subsidence funnels existed in the fill area, with a maximum subsidence rate of 100 mm/yr. From 2017 to 2020, the subsidence funnels enlarged, and their subsidence rates accelerated. Further analysis proved that the main factors induced the severe ground subsidence in the study area, including the compressibility and collapsibility of loess, rapid urban construction, geological environment change, traffic circulation load, and dynamic change of groundwater. The experimental results indicated that the improved TS-InSAR method is adaptive to monitoring uneven subsidence of deep loess area. Moreover, related data and information would provide reference to the large-scale ground deformation monitoring and in similar loess areas.

scholarly journals Density Distribution Maps: A Novel Tool for Subcellular Distribution Analysis and Quantitative Biomedical Imaging

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 1009
Author(s):  
Ilaria De Santis ◽  
Michele Zanoni ◽  
Chiara Arienti ◽  
Alessandro Bevilacqua ◽  
Anna Tesei
Keyword(s):  
Density Distribution ◽  
Large Scale ◽  
Super Resolution ◽  
Spatial Location ◽  
Relative Displacement ◽  
Distribution Analysis ◽  
Laboratory Equipment ◽  
Imaging Device ◽  
Distribution Maps ◽  
Super Resolution Microscopy

Subcellular spatial location is an essential descriptor of molecules biological function. Presently, super-resolution microscopy techniques enable quantification of subcellular objects distribution in fluorescence images, but they rely on instrumentation, tools and expertise not constituting a default for most of laboratories. We propose a method that allows resolving subcellular structures location by reinforcing each single pixel position with the information from surroundings. Although designed for entry-level laboratory equipment with common resolution powers, our method is independent from imaging device resolution, and thus can benefit also super-resolution microscopy. The approach permits to generate density distribution maps (DDMs) informative of both objects’ absolute location and self-relative displacement, thus practically reducing location uncertainty and increasing the accuracy of signal mapping. This work proves the capability of the DDMs to: (a) improve the informativeness of spatial distributions; (b) empower subcellular molecules distributions analysis; (c) extend their applicability beyond mere spatial object mapping. Finally, the possibility of enhancing or even disclosing latent distributions can concretely speed-up routine, large-scale and follow-up experiments, besides representing a benefit for all spatial distribution studies, independently of the image acquisition resolution. DDMaker, a Software endowed with a user-friendly Graphical User Interface (GUI), is also provided to support users in DDMs creation.

scholarly journals Transient Response of Bridge Piers to Structure Separation under Near-Fault Vertical Earthquake

2021 ◽  
Vol 11 (9) ◽  
pp. 4068
Author(s):  
Wenjun An ◽  
Guquan Song
Keyword(s):  
Large Scale ◽  
Bending Moment ◽  
Relative Displacement ◽  
Superposition Method ◽  
Longitudinal Displacement ◽  
Transient Wave ◽  
Vibration Period ◽  
Vertical Excitation ◽  
Mode Superposition Method ◽  
Main Girder

Given the possible separation problem caused by the double-span continuous beam bridge under the action of the vertical earthquake, considering the wave effect, the transient wave characteristic function method and the indirect mode superposition method are used to solve the response theory of the bridge structure during the earthquake. Through the example analysis, the pier bending moment changes under different vertical excitation periods and excitation amplitudes are calculated. Calculations prove that: (1) When the seismic excitation period is close to the vertical natural vibration period of the bridge, the main girder and the bridge pier may be separated; (2) When the pier has a high height, the separation has a more significant impact on the longitudinal displacement of the bridge, but the maximum relative displacement caused by the separation is random; (3) Large-scale vertical excitation will increase the number of partitions of the structure, and at the same time increase the vertical collision force between the main girder and the pier, but the effect on the longitudinal displacement of the form is uncertain; (4) When V/H exceeds a specific value, the pier will not only be damaged by bending, but will also be damaged by axial compression.

A landscape-ontology scale MTInSAR deformation monitoring solution for the sustainable conservation of architectural heritage sites

2021 ◽  
Author(s):  
Hang Xu ◽  
FuLong Chen
Keyword(s):  
Large Scale ◽  
Anthropogenic Activities ◽  
Deformation Monitoring ◽  
Global Navigation Satellite Systems ◽  
Structural Defects ◽  
Spatial Density ◽  
Architectural Heritage ◽  
Heritage Sites ◽  
Sustainable Conservation ◽  
Great Wall

<p>Architectural heritage is cultural and spiritual symbol of our predecessors with immeasurable historical, artistic, and technological value. However, these heritages are exposed to long-term degradation due to the combination impacts from the natural erosion and anthropogenic activities. Consequently, it is important to establish an effective deformation monitoring system to support the sustainable conservation of those properties. In order to make complementary to conventional geodetic measurements such as global navigation satellite systems (GNSS) and leveling in terms of spatial density, we propose a landscape-ontology scale multi-temporal InSAR (MTInSAR) solution for the preventive deformation monitoring of large-scale architectural heritage sites through the adaption of current MTInSAR approaches. We apply different solutions in Shanhaiguan section of the Great Wall in China and the Angkor Wat in Cambodia based on their onsite characteristics. At the cultural landscape scale, we improve the small baseline subset (SBAS) approach by the induced pseudo-baseline strategy in order to avoid the errors caused by inaccurate external DEM, resulting in a robust deformation estimation in mountainous areas where the architecture heritage of the Great Wall located; at the ontology scale, we integrate the differential SAR tomography (DTomoSAR) with the finite element method (FEM) for the structural instability detection of the Angkor Wat Temple, pinpointing the structural defects from the 3D deformation measurements and simulation. This study demonstrates the capability of adaptive MTInSAR approaches for the preventive monitoring the deformation of large-scale architectural heritage sites.</p><p><strong>Keywords</strong>: Architectural heritage; two-scale; deformation; MTInSAR</p>

scholarly journals On the short-term variability of turbulence and temperature in the winter mesosphere

2018 ◽  
Vol 36 (4) ◽  
pp. 1099-1116
Author(s):  
Gerald A. Lehmacher ◽  
Miguel F. Larsen ◽  
Richard L. Collins ◽  
Aroh Barjatya ◽  
Boris Strelnikov
Keyword(s):  
Attitude Control ◽  
Large Scale ◽  
Lower Thermosphere ◽  
Density Fluctuations ◽  
Large Temperature ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Temperature Structure ◽  
Wind Shears

Abstract. Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (<0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0<Ri<0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (Kp∼5).

scholarly journals Fault Reconstruction Approach for Distributed Coordinated Spacecraft Attitude Control System

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Mingyi Huo ◽  
Yanning Guo ◽  
Xing Huo
Keyword(s):  
Control System ◽  
Attitude Control ◽  
Large Scale ◽  
Sliding Mode ◽  
Reconstruction Error ◽  
Spacecraft Attitude ◽  
Alignment Error ◽  
Spacecraft Attitude Control ◽  
Attitude Control System ◽  
Fault Reconstruction

This work presents a novel fault reconstruction approach for a large-scale system, that is, a distributed coordinated spacecraft attitude control system. The attitude of all the spacecrafts in this distributed system is controlled by using thrusters. All possible faults of thruster including thrust magnitude error and alignment error are investigated. As a stepping stone, the mathematical model of thruster is firstly established based on the thruster configuration. On the basis of this, a sliding mode observer is then proposed to reconstruct faults in each agent of the coordinated control system. A Lyapunov-based analysis shows that the observer asymptotically converges to the actual faults. The key feature of this fault reconstruction approach is that it can achieve a faster reconstruction of the fault in comparison with the conventional fault reconstruction schemes. It can globally reconstruct thruster faults with zero reconstruction error, and this is accomplished within finite time. The effectiveness of the proposed approach is analytically authenticated via simulation study.

Mission Performance Model

2015 ◽  
pp. 51-78
Keyword(s):  
Attitude Control ◽  
Large Scale ◽  
Training System ◽  
Performance Model ◽  
Performance Models ◽  
Application Performance ◽  
Mission Success ◽  
Operational Application ◽  
Flight Deck ◽  
Effective Design

Mission Performance Models (MPM) are important to the design of modern digital avionic systems because the flight deck information is no longer obvious. In large-scale dynamic systems, necessary responses to the incoming information model should be a direct correspondence. A Mission Performance Model is an abstract representation of the activity clusters necessary to achieve mission success. The three core activity clusters are trajectory management, energy management, and attitude control and will be covered in detail. Their combined performance characteristics highlight the vehicle's kinematic attributes, which then anticipates unstable conditions. Six MPM are necessary for the effective design and employment of a modern mission-ready flight deck. We describe MPM and their structure, purpose, and operational application. Performance models have many important uses including training system definition and design, avionic system design, and safety programs.

The Satellite Attitude Control Law Design Based on Machine Learning

2014 ◽  
Vol 519-520 ◽  
pp. 741-746 ◽  
Author(s):  
Guo Jiang Sun ◽  
Jin Hui Li ◽  
Shi Ming Chen ◽  
Yun Feng Dong
Keyword(s):  
Machine Learning ◽  
Attitude Control ◽  
Fitness Function ◽  
Control Law ◽  
Sensors And Actuators ◽  
Control Laws ◽  
Satellite Attitude ◽  
Control Precision ◽  
Attitude Error ◽  
Satellite Attitude Control

Traditional optimization algorithms can only optimize parameters in control laws. Machine learning method can optimize parameters and evolve satellite attitude control law automatically under certain criterion. Single axis satellite attitude simulation system with noise was built up, which included satellite attitude dynamic model, sensors and actuators model. The control laws inputs were attitude error, attitude errors integral and angular velocity error, and outputs were actuators control instructions. Control laws fitness function was an attitude errors statistical function. With suitable function set selected for genetic programming (GP) and parse tree used to represent a control law expression, GP was used to evolve control law expression automatically. Simulation result shows that this method can evolve control law with uncertainties noise better. The evolved control law response and control precision are better than PID, and it can be used in satellite attitude control.

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