The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Lorenzo Fagiano - One of the best experts on this subject based on the ideXlab platform.
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on the take off of airborne wind energy systems based on Rigid Wings
Renewable Energy, 2017Co-Authors: Lorenzo Fagiano, Stephan SchnezAbstract:The problem of launching a tethered Rigid aircraft for airborne wind energy generation is investigated. Exploiting well-assessed physical principles, an analysis of four different take-off approaches is carried out. The approaches are then compared on the basis of quantitative and qualitative criteria introduced to assess their technical and economic viability. In particular, the additional power required by the take-off functionality is computed and related to the peak mechanical power generated by the system. Moreover, the additionally required on-board mass is estimated, which impacts the cut-in wind speed of the generator. Finally, the approximate ground area required for take-off is also determined. After the theoretical comparison, a deeper study of the concept that is deemed the most viable one, i.e. a linear take-off maneuver combined with on-board propellers, is performed by means of numerical simulations. The simulation results are used to refine the initial analysis and further confirm the viability of the approach.
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on the take off of airborne wind energy systems based on Rigid Wings
arXiv: Optimization and Control, 2015Co-Authors: Lorenzo Fagiano, Stephan SchnezAbstract:The problem of launching a tethered aircraft to be used for airborne wind energy generation is investigated. Exploiting well-assessed physical principles, an analysis of three different take-off approaches is carried out. The approaches are then compared on the basis of quantitative and qualitative criteria introduced to assess their technical and economic viability. Finally, a deeper study of the concept that is deemed the most viable one, i.e. a linear take-off maneuver combined with on-board propellers, is performed by means of numerical simulations. The latter are used to refine the initial analysis in terms of power required for take-off, and further confirm the viability of the approach.
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On Sensor Fusion for Airborne Wind Energy Systems
IEEE Transactions on Control Systems Technology, 2014Co-Authors: Lorenzo Fagiano, Khanh Huynh, Bassam Bamieh, Mustafa KhammashAbstract:A study on filtering aspects of airborne wind energy generators is presented. This class of renewable energy systems aim to convert the aerodynamic forces generated by tethered Wings, flying in closed paths transverse to the wind flow, into electricity. The accurate reconstruction of the wing's position, velocity, and heading is of fundamental importance for the automatic control of these kinds of systems. The difficulty of the estimation problem arises from the nonlinear dynamics, wide speed range, large accelerations, and fast changes of direction that the wing experiences during operation. It is shown that the overall nonlinear system has a specific structure allowing its partitioning into subsystems, hence leading to a series of simpler filtering problems. Different sensor setups are then considered, and the related sensor fusion algorithms are presented. The results of experimental tests carried out with a small-scale prototype and Wings of different sizes are discussed. The designed filtering algorithms rely purely on kinematic laws, hence they are independent of features such as wing area, aerodynamic efficiency, mass, and so on. Therefore, the presented results are representative for systems with larger size and different wing design, different number of tethers and/or Rigid Wings also.
Stephan Schnez - One of the best experts on this subject based on the ideXlab platform.
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on the take off of airborne wind energy systems based on Rigid Wings
Renewable Energy, 2017Co-Authors: Lorenzo Fagiano, Stephan SchnezAbstract:The problem of launching a tethered Rigid aircraft for airborne wind energy generation is investigated. Exploiting well-assessed physical principles, an analysis of four different take-off approaches is carried out. The approaches are then compared on the basis of quantitative and qualitative criteria introduced to assess their technical and economic viability. In particular, the additional power required by the take-off functionality is computed and related to the peak mechanical power generated by the system. Moreover, the additionally required on-board mass is estimated, which impacts the cut-in wind speed of the generator. Finally, the approximate ground area required for take-off is also determined. After the theoretical comparison, a deeper study of the concept that is deemed the most viable one, i.e. a linear take-off maneuver combined with on-board propellers, is performed by means of numerical simulations. The simulation results are used to refine the initial analysis and further confirm the viability of the approach.
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on the take off of airborne wind energy systems based on Rigid Wings
arXiv: Optimization and Control, 2015Co-Authors: Lorenzo Fagiano, Stephan SchnezAbstract:The problem of launching a tethered aircraft to be used for airborne wind energy generation is investigated. Exploiting well-assessed physical principles, an analysis of three different take-off approaches is carried out. The approaches are then compared on the basis of quantitative and qualitative criteria introduced to assess their technical and economic viability. Finally, a deeper study of the concept that is deemed the most viable one, i.e. a linear take-off maneuver combined with on-board propellers, is performed by means of numerical simulations. The latter are used to refine the initial analysis in terms of power required for take-off, and further confirm the viability of the approach.
Fai Cheng - One of the best experts on this subject based on the ideXlab platform.
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A bio-inspired study on tidal energy extraction with flexible flapping Wings
Bioinspiration & Biomimetics, 2013Co-Authors: Qing Xiao, Fai ChengAbstract:Previous research on the flexible structure of flapping Wings has shown an improved propulsion performance in comparison to Rigid Wings. However, not much is known about this function in terms of power efficiency modification for flapping wing energy devices. In order to study the role of the flexible wing deformation in the hydrodynamics of flapping wing energy devices, we computationally model the two-dimensional flexible single and twin flapping Wings in operation under the energy extraction conditions with a large Reynolds number of 106. The flexible motion for the present study is predetermined based on a priori structural result which is different from a passive flexibility solution. Four different models are investigated with additional potential local distortions near the leading and trailing edges. Our simulation results show that the flexible structure of a wing is beneficial to enhance power efficiency by increasing the peaks of lift force over a flapping cycle, and tuning the phase shift between force and velocity to a favourable trend. Moreover, the impact of wing flexibility on efficiency is more profound at a low nominal effective angle of attack (AoA). At a typical flapping frequency f * = 0.15 and nominal effective AoA of 10°, a flexible integrated wing generates 7.68% higher efficiency than a Rigid wing. An even higher increase, around six times that of a Rigid wing, is achievable if the nominal effective AoA is reduced to zero degrees at feathering condition. This is very attractive for a semi-actuated flapping energy system, where energy input is needed to activate the pitching motion. The results from our dual-wing study found that a parallel twin-wing device can produce more power compared to a single wing due to the strong flow interaction between the two Wings.
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A bio-inspired study on tidal energy extraction with flexible flapping Wings
Bioinspiration and Biomimetics, 2013Co-Authors: Wendi Liu, Qing Xiao, Fai ChengAbstract:Previous research on the flexible structure of flapping Wings has shown an improved propulsion performance in comparison to Rigid Wings. However, not much is known about this function in terms of power efficiency modification for flapping wing energy devices. In order to study the role of the flexible wing deformation in the hydrodynamics of flapping wing energy devices, we computationally model the two-dimensional flexible single and twin flapping Wings in operation under the energy extraction conditions with a large Reynolds number of 10 6 . The flexible motion for the present study is predetermined based on a priori structural result which is different from a passive flexibility solution. Four different models are investigated with additional potential local distortions near the leading and trailing edges. Our simulation results show that the flexible structure of a wing is beneficial to enhance power efficiency by increasing the peaks of lift force over a flapping cycle, and tuning the phase shift between force and velocity to a favourable trend. Moreover, the impact of wing flexibility on efficiency is more profound at a low nominal effective angle of attack (AoA). At a typical flapping frequency f * = 0.15 and nominal effective AoA of 10 • , a flexible integrated wing generates 7.68% higher efficiency than a Rigid wing. An even higher increase, around six times that of a Rigid wing, is achievable if the nominal effective AoA is reduced to zero degrees at feathering condition. This is very attractive for a semi-actuated flapping energy system, where energy input is needed to activate the pitching motion. The results from our dual-wing study found that a parallel twin-wing device can produce more power compared to a single wing due to the strong flow interaction between the two Wings. (Some figures may appear in colour only in the online journal) Nomenclature A sweep area (m 2) c chord length (m) C l (t) instantaneous lift coefficient C m (t) instantaneous moment coefficient C op power coefficient d b foil displacement at trailing edge (m) f frequency of flapping wing (Hz) 3 Author to whom any correspondence should be addressed. f * reduced frequency h(t) instantaneous heaving position (m) h 0 amplitude of heaving motion (m) l c pitching centre (m) p instantaneous power (W) S f gap ratio between twin Wings t instant time (s) T oscillating period (s) U ∞ free-stream velocity (m/s) x f x coordinate in body-fixed system (m) y(x f , t) instantaneous foil lateral excursion 1748-3182/13/036011+16$33.00 1 © 2013 IOP Publishing Ltd Printed in the UK & the USA Bioinspir. Biomim. 8 (2013) 036011 W Liu et al α 0 nominal effective AoA (deg) α eff (t) effective angle of attack (deg) α f (t) local AoA at the leading edge in body-fixed coordinate system (deg) α l (t,x) local effective AoA (deg) α t (x f) lateral amplitude η energy extraction efficiency θ 0 amplitude of pitching motion (deg) θ l (t,x) local pitching angle (deg) θ l0 averaged local pitching amplitude (deg) θ t (t) instantaneous pitching angle (deg) ω angular frequency AoA angle of attack LEC leading edge control (model) LEV leading edge vortex TEC trailing edge control (model) LE leading edge FSI fluid–structure interaction
Sunil K. Agrawal - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of effects of flapping wing aspect ratio and flexibility on aerodynamic performance
2010 IEEE International Conference on Robotics and Automation, 2010Co-Authors: Chengkun Zhang, Zaeem A. Khan, Sunil K. AgrawalAbstract:In earlier studies, the optimal wing kinematics that gives the best aerodynamic performance was determined with a robotic flapper. The geometry and physical properties of Wings are also critical for designing and fabricating Flapping Wing Micro Air Vehicles (FWMAVs). In this paper, the effects of wing aspect ratio and flexibility on aerodynamic performance are experimentally investigated to determine the optimal aspect ratio for Micro Air Vehicles (MAVs) Wings at Reynolds number around 18,000. The comparison between the aerodynamic performance of Rigid Wings and flexible Wings are also made whose veins are fabricated out of different materials.
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ICRA - Experimental investigation of effects of flapping wing aspect ratio and flexibility on aerodynamic performance
2010 IEEE International Conference on Robotics and Automation, 2010Co-Authors: Chengkun Zhang, Zaeem A. Khan, Sunil K. AgrawalAbstract:In earlier studies, the optimal wing kinematics that gives the best aerodynamic performance was determined with a robotic flapper. The geometry and physical properties of Wings are also critical for designing and fabricating Flapping Wing Micro Air Vehicles (FWMAVs). In this paper, the effects of wing aspect ratio and flexibility on aerodynamic performance are experimentally investigated to determine the optimal aspect ratio for Micro Air Vehicles (MAVs) Wings at Reynolds number around 18,000. The comparison between the aerodynamic performance of Rigid Wings and flexible Wings are also made whose veins are fabricated out of different materials.
Mustafa Khammash - One of the best experts on this subject based on the ideXlab platform.
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On Sensor Fusion for Airborne Wind Energy Systems
IEEE Transactions on Control Systems Technology, 2014Co-Authors: Lorenzo Fagiano, Khanh Huynh, Bassam Bamieh, Mustafa KhammashAbstract:A study on filtering aspects of airborne wind energy generators is presented. This class of renewable energy systems aim to convert the aerodynamic forces generated by tethered Wings, flying in closed paths transverse to the wind flow, into electricity. The accurate reconstruction of the wing's position, velocity, and heading is of fundamental importance for the automatic control of these kinds of systems. The difficulty of the estimation problem arises from the nonlinear dynamics, wide speed range, large accelerations, and fast changes of direction that the wing experiences during operation. It is shown that the overall nonlinear system has a specific structure allowing its partitioning into subsystems, hence leading to a series of simpler filtering problems. Different sensor setups are then considered, and the related sensor fusion algorithms are presented. The results of experimental tests carried out with a small-scale prototype and Wings of different sizes are discussed. The designed filtering algorithms rely purely on kinematic laws, hence they are independent of features such as wing area, aerodynamic efficiency, mass, and so on. Therefore, the presented results are representative for systems with larger size and different wing design, different number of tethers and/or Rigid Wings also.
