Trajectory planning for mini unmanned helicopter in obstacle and windy environments

2018 ◽  
Vol 90 (5) ◽  
pp. 806-814
Author(s):  
Jinwu Xiang ◽  
Tong Shen ◽  
Daochun Li
Keyword(s):  
Boundary Layer ◽  
Trajectory Planning ◽  
Wind Field ◽  
High Speed ◽  
Pseudospectral Method ◽  
Strong Wind ◽  
Unmanned Helicopter ◽  
Wind Fields ◽  
Content Type ◽  
Flight Dynamics Model

Purpose Obstacle and wind field are common environmental factors for mini unmanned helicopter (MUH) flight. This paper aims to develop a trajectory planning approach guiding MUH to avoid static and dynamic obstacles and to fly in steady uniform or boundary-layer wind field. Design/methodology/approach An optimal control model including a nonlinear flight dynamics model and a cubic obstacle model is established for MUH trajectory planning. Radau pseudospectral method is used to generate the optimal trajectory. Findings The approach can plan reasonable obstacle-avoiding trajectories in obstacle and windy environments. The simulation results show that high-speed wind fields increase the flight time and fluctuation of control inputs. If boundary-layer wind field exists, the trajectory deforms significantly and gets closer to the ground to escape from the strong wind. Originality/value The key innovations in this paper include a cubic obstacle model which is straightforward and practical for trajectory planning and MUH trajectory planning in steady uniform wind field and boundary-layer wind field. This study provides an efficient solution to the trajectory planning for MUH in obstacle and windy environments.

Study on the Downburst Field Characteristics under the Influence of Two-Dimensional Continuous Mountains at Different Distance

2014 ◽  
Vol 580-583 ◽  
pp. 3111-3114
Author(s):  
Yi Sun ◽  
Yuan Ze Wu ◽  
Hai Tao Shi ◽  
Bai Feng Ji
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Wind Field ◽  
Strong Wind ◽  
Two Dimensional ◽  
Field Characteristic ◽  
Main Factors ◽  
Cfd Numerical Simulation ◽  
The Impact

Downburst is an outburst strong wind on or near the ground, and its wind field characteristics are significantly different from boundary layer winds. Continuous mountains at different distance are one of the main factors for the influence of downburst wind field characteristic. In this thesis, the changes of the wind field characteristics under the influence of continuous mountains at different distance after the downburst happened are studied by CFD numerical simulation. The impact of downburst is analysed and summarized through the charts.

scholarly journals Empirical high-resolution wind field and gust model in mountainous and hilly terrain based on the dense WegenerNet station networks

2018 ◽  
Author(s):  
Christoph Schlager ◽  
Gottfried Kirchengast ◽  
Juergen Fuchsberger
Keyword(s):  
High Resolution ◽  
Wind Field ◽  
Climate Models ◽  
Meteorological Station ◽  
Strong Wind ◽  
Climate Data ◽  
Wind Fields ◽  
Station Network ◽  
Weather And Climate ◽  
Wind Events

Abstract. A weather diagnostic application for automatic generation of gridded wind fields in near-real time, recently developed by the authors (Schlager et al., 2017), is applied to the WegenerNet Johnsbachtal (JBT) meteorological station network. This station network contains eleven meteorological stations at elevations from about 600 m to 2200 m in a mountainous region in the north of Styria, Austria. The application generates, based on meteorological observations with a temporal resolution of 10 minutes from the WegenerNet JBT, mean wind and wind gust fields at 10 m and 50 m height levels with a high spatial resolution of 100 × 100 m and a temporal resolution of 30 minutes. These wind field products are automatically stored to the WegenerNet data archives, which also include long-term averaged weather and climate datasets from post-processing. A main purpose of these empirically modeled products is the evaluation of convection-permitting dynamical climate models as well as investigating weather and climate variability on a local scale. The application's performance is evaluated against the observations from meteorological stations for representative weather conditions, for a month including mainly thermally induced wind events (July 2014) and a month with frequently occurring strong wind events (December 2013). The overall statistical agreement, estimated for the vector-mean wind speed, shows a reasonably good modeling performance with somewhat better values for the strong wind conditions. The difference between modeled and observed wind directions depends on the station location, where locations along mountain slopes are particularly challenging. Furthermore, the seasonal statistical agreement was investigated from five-year climate data of the WegenerNet JBT in comparison to nine-year climate data from the high-density WegenerNet meteorological station network Feldbach Region (FBR) analyzed by Schlager et al., (2017)In general, the five-year statistical evaluation for the JBT indicates similar performance as the shorter-term evaluations of the two representative months. Because of the denser WegenerNet FBR network, the statistical results show better performance for this station network. The application can now serve as a valuable tool for intercomparison with and evaluation of wind fields from high-resolution dynamical climate models in both the WegenerNet FBR and JBT regions.

scholarly journals Exploration of high-altitude dynamic soaring based on six-degree-of-freedom model

2021 ◽  
Vol 39 (4) ◽  
pp. 703-711
Author(s):  
Siqi Liu ◽  
Junqiang Bai
Keyword(s):  
High Altitude ◽  
Wind Field ◽  
Degree Of Freedom ◽  
Field Energy ◽  
Dynamics Model ◽  
Wind Fields ◽  
Sideslip Angle ◽  
Dynamic Soaring ◽  
Flight Dynamics Model ◽  
Six Degree Of Freedom

Dynamic soaring is an emerging flight range-extension technology that effectively reduces UAV's energy consumption by deriving wind energy from lateral gradient wind fields. Comparing with the small UAV's near the surface, the application of dynamic soaring technology in the high-altitude long-endurance flight requires the additional consideration of the influence of sustained side wind, the influence of the sideslip angle cannot be ignored. This puts higher requirements on the flight dynamics model. In this paper, the dynamic model for the high-altitude dynamic soaring based on the six-degree-of-freedom equation is modeled to replace the traditional mass point model; the energy change principle of the high-altitude dynamic gliding is derived; the effect of the high-altitude wind field on the dynamic soaring UAV is analyzed; and the way to get optimal wind field energy acquisition and energy saving efficiency are analyzed. The results show that the dynamics model based on the six-degree-of-freedom equation can more realistically reflect at high altitude; the application of dynamic soaring can effectively improve the range of the high-altitude UAV; the wind direction at high-altitude wind field has a significant effect on the dynamic soaring efficiency.

scholarly journals Evaluation and Post-Processing of Reanalysis Wind Speeds for Renewable Energy Applications

2021 ◽  
Author(s):  
Sebastian Brune ◽  
Jan D. Keller ◽  
Sabrina Wahl
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Turbine ◽  
Wind Field ◽  
Lower Boundary ◽  
Horizontal Resolution ◽  
Lower Atmosphere ◽  
Wind Fields ◽  
Wind Model ◽  
Lower Boundary Layer

<p>The correct spatio-temporal representation of wind speed is of large interest for the wind energy sector. Therefore, this study compares wind measurements in different heights from several locations in Central Europe with two global (ERA5, MERRA-2) and one regional reanalysis (COSMO-REA6). Employing a two-parameter Weibull distribution, the shape and scale parameters as well as mean, standard deviation and RMSE are investigated at and around common wind turbine hub height. We find that COSMO-REA6 best describes wind fields closer to the surface possibly due to its high horizontal resolution. Here, it also exhibits a good alignment with the diurnal cycle. However, for common wind turbine hub heights and above, ERA5 outperforms the other two reanalyses possibly due to its higher vertical resolution. MERRA-2 overestimates wind speed in the lower boundary layer at nearly all sites.</p><p>In the next step, a diagnostic and mass-consistent wind model is applied to the COSMO-REA6 wind field. The resolution of the wind field will be increased by a factor of 8 from originally 6 km to approximately 800 m. In addition to the vertical stability of the lower atmosphere, the orography on the finer grid and the corresponding effects are taken into account. We expect that especially in complex terrain the wind field will be corrected and thus should fit better to the observations. Channeling effects, shadowing and increased wind speed in exposed locations can be better represented. The new high-resolution wind field forms the basis for a statistical wind model to obtain post-processed wind estimates in the lower boundary layer. This approach will utilize generalized linear model and/or an artificial neural network techniques.</p>

A new approach for numerical-diffusion control of flux-vector-splitting schemes for viscous-compressible flows

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Paragmoni Kalita ◽  
Anoop K. Dass ◽  
Jongki Hazarika
Keyword(s):  
Boundary Layer ◽  
High Speed ◽  
Scaling Function ◽  
High Speed Flow ◽  
Diffusion Term ◽  
New Approach ◽  
Numerical Diffusion ◽  
Content Type ◽  
Speed Flow ◽  
Flux Vector Splitting

Purpose The flux vector splitting (FVS) schemes are known for their higher resistance to shock instabilities and carbuncle phenomena in high-speed flow computations, which are generally accompanied by relatively large numerical diffusion. However, it is desirable to control the numerical diffusion of FVS schemes inside the boundary layer for improved accuracy in viscous flow computations. This study aims to develop a new methodology for controlling the numerical diffusion of FVS schemes for viscous flow computations with the help of a recently developed boundary layer sensor. Design/methodology/approach The governing equations are solved using a cell-centered finite volume approach and Euler time integration. The gradients in the viscous fluxes are evaluated by applying the Green’s theorem. For the inviscid fluxes, a new approach is introduced, where the original upwind formulation of an FVS scheme is first cast into an equivalent central discretization along with a numerical diffusion term. Subsequently, the numerical diffusion is scaled down by using a novel scaling function that operates based on a boundary layer sensor. The effectiveness of the approach is demonstrated by applying the same on van Leer’s FVS and AUSM schemes. The resulting schemes are named as Diffusion-Regulated van Leer’s FVS-Viscous (DRvLFV) and Diffusion-Regulated AUSM-Viscous (DRAUSMV) schemes. Findings The numerical tests show that the DRvLFV scheme shows significant improvement over its parent scheme in resolving the skin friction and wall heat flux profiles. The DRAUSMV scheme is also found marginally more accurate than its parent scheme. However, stability requirements limit the scaling down of only the numerical diffusion term corresponding to the acoustic part of the AUSM scheme. Originality/value To the best of the authors’ knowledge, this is the first successful attempt to regulate the numerical diffusion of FVS schemes inside boundary layers by applying a novel scaling function to their artificial viscosity forms. The new methodology can reduce the erroneous smearing of boundary layers by FVS schemes in high-speed flow applications.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

Influence of ageing treatment on microstructure, mechanical properties and adhesive wear behaviour of 6063 aluminium alloy

2014 ◽  
Vol 66 (4) ◽  
pp. 520-524 ◽  
Author(s):  
Serkan Büyükdoğan ◽  
Süleyman Gündüz ◽  
Mustafa Türkmen
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
High Speed ◽  
Al Alloys ◽  
Wear Behaviour ◽  
Al Alloy ◽  
Strain Ageing ◽  
Content Type ◽  
Static Strain ◽  
Structural Applications

Purpose – The paper aims to provide new observations about static strain ageing in aluminium (Al) alloys which are widely used in structural applications. Design/methodology/approach – The present work aims to provide theoretical and practical information to industries or researchers who may be interested in the effect of static strain ageing on mechanical properties of Al alloys. The data are sorted into the following sections: introduction, materials and experimental procedure, results and discussion and conclusions. Findings – Tensile strength, proof strength (0.2 per cent) and percentage elongation measurement were used to investigate the effect of strain ageing on the mechanical properties. Wear tests were performed by sliding the pin specimens, which were prepared from as-received, solution heat-treated, deformed and undeformed specimens after ageing, on high-speed tool steel (64 HRC). It is concluded that the variations in ageing time improved the strength and wear resistance of the 6063 Al alloy; however, a plastically deformed solution-treated alloy has higher strength and wear resistance than undeformed specimens for different ageing times at 180°C. Practical implications – A very useful source of information for industries using or planning to produce Al alloys. Originality/value – This paper fulfils an identified resource need and offers practical help to the industries.

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