134 research outputs found

    Control of Towing Kites for Seagoing Vessels

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    In this paper we present the basic features of the flight control of the SkySails towing kite system. After introduction of coordinate definitions and basic system dynamics we introduce a novel model used for controller design and justify its main dynamics with results from system identification based on numerous sea trials. We then present the controller design which we successfully use for operational flights for several years. Finally we explain the generation of dynamical flight patterns.Comment: 12 pages, 18 figures; submitted to IEEE Trans. on Control Systems Technology; revision: Fig. 15 corrected, minor text change

    Sensors and Navigation Algorithms for Flight Control of Tethered Kites

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    We present the sensor setup and the basic navigation algorithm used for the flight control of the SkySails towing kite system. Starting with brief summaries on system setup and equations of motion of the tethered kite system, we subsequently give an overview of the sensor setup, present the navigation task and discuss challenges which have to be mastered. In the second part we introduce in detail the inertial navigation algorithm which has been used for operational flights for years. The functional capability of this algorithm is illustrated by experimental flight data. Finally we suggest a modification of the algorithms as further development step in order to overcome certain limitations.Comment: 6 pages, 9 figures, submitted to European Control Conference (ECC) 201

    Modeling and dynamics of a two-line kite

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    A mathematical model of a kite connected to the ground by two straight tethers of varying lengths is presented and used to study the traction force generated by kites flying in cross-wind conditions. The equations of motion are obtained by using a Lagrangian formulation, which yields a low-order system of ordinary differential equations free of constraint forces. Two parameters are chosen for the analysis. The first parameter is the wind velocity. The second parameter is one of the stability derivatives of the aerodynamic model: the roll response to the sideslip angle, known also as effective dihedral. This parameter affects significantly the lateral dynamics of the kite. It has been found that when the effective dihedral is below a certain threshold, the kite follows stable periodic trajectories, and naturally flies in cross-wind conditions while generating a high tension along both tethers. This result indicates that kite-based propulsion systems could operate without controlling tether lengths if kite design, including the dihedral and sweep angles, is done appropriately. If both tether lengths are varied out-of-phase and periodically, then kite dynamics can be very complex. The trajectories are chaotic and intermittent for values of the effective dihedral below a certain negative threshold. It is found that tether tensions can be very similar with and without tether length modulation if the parameters of the model are well-chosen. The use of the model for pure traction applications of kites is discussedThis work was supported by the Ministerio de Economía y Competitividad of Spain and the European Regional Development Fund under the project ENE2015-69937-R (MINECO/FEDER, UE). GSA work is supported by the Ministerio de Economía y Competitividad of Spain under the Grant RYC-2014-15357. MGV was partially supported by grant TRA2013-41103-P (MINECO/FEDER, UE). RS was partially supported by the projects AWESCO (H2020-ITN-642682) and REACH (H2020-FTIPilot-691173)

    Crosswind Kite Control - A Benchmark Problem for Advanced Control and Dynamic Optimization

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    This article presents a kite control and optimization problem intended as a benchmark problem for advanced control and optimization. We provide an entry point to this exciting renewable energy system for researchers in control and optimization methods looking for a realistic test bench, and/or a useful application case for their theory. The benchmark problem in this paper can be studied in simulation, and a complete Simulink model is provided to facilitate this. The simulated scenario, which reproduces many of the challenges presented by a real system, is based on experimental studies from the literature, industrial data and the first author’s own experience in experimental kite control. In par- ticular, an experimentally validated wind turbulence model is included, which subjects the kite to realistic disturbances. The benchmark problem is that of controlling a kite such that the average line tension is maximized. Two different models are provided: A more comprehensive one is used to simulate the ’plant’, while a simpler ’model’ is used to design and implement control and optimization strategies. This way, uncertainty is present in the form of plant-model mismatch. The outputs of the plant are corrupted by measurement noise. The maximum achievable average line tension for the plant is calculated, which should facilitate the performance comparison of different algorithms. A simple control strategy is implemented on the plant and found to be quite suboptimal, even if the free parameters of the algorithm are well tuned. An open question is whether or not more advanced control algorithms could do better

    A state-of-the-art review and feasibility analysis of high altitude wind power in Northern Ireland

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    AbstractIn many countries wind energy has become an indispensable part of the electricity generation mix. The opportunity for ground based wind turbine systems are becoming more and more constrained due to limitations on turbine hub heights, blade lengths and location restrictions linked to environmental and permitting issues including special areas of conservation and social acceptance due to the visual and noise impacts. In the last decade there have been numerous proposals to harness high altitude winds, such as tethered kites, airfoils and dirigible based rotors. These technologies are designed to operate above the neutral atmospheric boundary layer of 1300m, which are subject to more powerful and persistent winds thus generating much higher electricity capacities. This paper presents an in-depth review of the state-of-the-art of high altitude wind power, evaluates the technical and economic viability of deploying high altitude wind power as a resource in Northern Ireland and identifies the optimal locations through considering wind data and geographical constraints. The key findings show that the total viable area over Northern Ireland for high altitude wind harnessing devices is 5109.6km2, with an average wind power density of 1998W/m2 over a 20-year span, at a fixed altitude of 3000m. An initial budget for a 2MW pumping kite device indicated a total cost £1,751,402 thus proving to be economically viable with other conventional wind-harnessing devices

    Airborne Wind Energy Conference 2019 : (AWEC 2019)

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    [Book of Abstracts from the Airborne Wind Energy Conference 2019.

    Optimization of an Airborne Wind Energy System using Constrained Gaussian Processes with Transient Measurements

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    Airborne wind energy systems are built to exploit the stronger and more consistent wind available at high altitudes that conventional wind turbines cannot reach. This however requires a reliable controller design that can keep the airborne system flying for long durations in varying environmental conditions, while respecting all operational constraints. A frequent design for such a system includes a flying airfoil tethered to a ground station. We demonstrate an on-line data based method that optimizes the towing force of such a system in the presence of altitude constraints and varying wind. We actively learn Gaussian Process models, mapping relevant measurements to the objective, constraint and state dynamic functions of the system. We then formulate a chance - constrained optimization problem that takes into consideration uncertainty in the learned functions and finds feasible directions for improvement. Simulation studies show that we can find near optimal set points for the controller without the use of significant assumptions on model dynamics while respecting the unknown constraint function. The results also show an improved performance over our previous work which was restricted to steady state processes

    Dynamics and control of a single-line maneuverable kite

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    Through simulation, an automated control system for a single-line maneuverable kite is developed for application in kite wind energy production. The kite used in this study is a small, tension-controlled, single-line kite, commonly known as a fighter kite. These kites have a simple design, but flying them requires complex control of line tension and visual input. At low tether tension, the kite is unstable; spinning about the tether. Increasing tension in the tether causes the kite to deform and fly in the direction it was facing. Experienced fliers can produce intricate maneuvers and often participate in competitions with other fliers. A simplified physical and behavioral numeric simulation of the kite\u27s dynamics was created and shown to closely approximate the actual kite\u27s flight characteristics. This model was used to develop successful control algorithms for autonomous flight. Information of the kite\u27s state and orientation used by the controller was gradually reduced to that which is physically measurable from the ground. An experimental test rig was designed and constructed for future testing in real wind conditions
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