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Kouzoupis D.,Albert Ludwigs University of Freiburg | Quirynen R.,Albert Ludwigs University of Freiburg | Quirynen R.,Catholic University of Leuven | Garcia J.L.,Albert Ludwigs University of Freiburg | And 3 more authors.
2016 IEEE 55th Conference on Decision and Control, CDC 2016 | Year: 2016

Distributed algorithms for sparse, large-scale optimization problems are preferable over centralized solvers when the computational units are physically far apart from each other or the problem size is too large for the available memory. However, most distributed methods sacrifice convergence speed for simpler computations. In this paper, we propose a novel algorithm for a certain class of nonconvex, separable optimization problems that combines both distributed computations and locally quadratic convergence. It is based on the principle of primal decomposition with exact Hessian information but uses soft coupling between the agents to avoid global calculations and adapt faster to online data changes. An important application field of the presented method is nonlinear parameter estimation, where increasing the number of experiments may lead to problem dimensions that are prohibitive for conventional solvers. We assess the performance of our method on the identification of an Airborne Wind Energy (AWE) system using real-world experimental data. © 2016 IEEE.


Erhard M.,SkySails GmbH | Strauch H.,SkySails
2013 European Control Conference, ECC 2013 | Year: 2013

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. © 2013 EUCA.


Grant
Agency: European Commission | Branch: H2020 | Program: MSCA-ITN-ETN | Phase: MSCA-ITN-2014-ETN | Award Amount: 3.00M | Year: 2015

The height of conventional wind turbines is limited by the enormous stresses on the structure. The idea of the Airborne Wind Energy (AWE) is to replace the most efficient part of a conventional wind turbine, the tip of the turbine blade, with a fast flying high efficiency kite, and to replace the rest of the structure by a tether which anchors the kite to the ground. Power is generated either by periodically pulling a ground based generator via a winch, or by small wind turbines mounted on the kite that exploit its fast cross wind motion. While the concept is highly promising, major academic and industrial research is still needed to achieve the performance required for industrial deployment. This can best be done by innovative junior researchers in a closely cooperating consortium of academic and industrial partners. The ITN AWESCO combines six interdisciplinary academic and four industrial network partners with seven associated partners, all selected on the basis of excellence and complementarity. All partners work already intensively on AWE systems, several with prototypes, and they are committed to create synergies via the cooperation in AWESCO. The main task is to train fourteen Early Stage Researchers (ESRs) in training-by-research and to create a closely connected new generation of leading European scientists that are ready to push the frontiers of airborne wind energy. AWESCO is the first major cooperation effort of the most important European actors in the field and will help Europe to gain a leading role in a possibly huge emerging renewable energy market, and to meet its ambitious CO2 targets. In addition, the AWESCO early stage researchers will be trained in cutting-edge simulation, design, sensing, and control technologies that are needed in many branches of engineering.


Erhard M.,SkySails GmbH | Strauch H.,SkySails GmbH
IEEE Transactions on Control Systems Technology | Year: 2013

In this paper, we present the basic features of the flight control of the SkySails towing kite system. After introducing the coordinate definitions and the 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. © 2012 IEEE.


Maass J.,Hamburg University of Applied Sciences | Erhard M.,SkySails GmbH
Green Energy and Technology | Year: 2013

In order to exploit high altitude wind energy, automatic computer control of tethered kites is a key to success. In this contribution, we report on the automation experiences and development issues on the software architecture gained by the development and operation of our ship propulsion kites during the last eight years. The first part puts focus on the requirements, the architecture and the signal flows of the distributed computer control system. The second part presents control system components in detail, introduces the respective challenges and explains how these are tackled by means of software engineering techniques. We conclude with a brief description on our hardware-in-the-loop simulation and test setup. © Springer-Verlag Berlin Heidelberg 2013.


Erhard M.,SkySails GmbH | Strauch H.,SkySails GmbH
Green Energy and Technology | Year: 2013

We present a simple model for the dynamics and aerodynamics of a tethered kite system and validate it by experimental flight data. After introduction of system setup and model assumptions, the equations of motion for the kinematics are derived and discussed. Then the turn rate law for the kite response to a steering deflection is introduced. The tutorial introduction of the model is finalized by an extension for varying tether lengths, which is the regular operation mode of certain classes of airborne wind energy setups. The second part starts with a summary of the sensor setup. Then, the turn rate law, as distinguishing feature of the model, is illustrated and validated by experimental data. Subsequently, we discuss the kinematics of the kite by comparing model based prediction to experiment. Conclusively, we briefly summarize controller design considerations and discuss the flight controller performance, which further proves the validity of the model as it is based on a feed forward term which in turn, is build on the presented model. © Springer-Verlag Berlin Heidelberg 2013.


Paulig X.,SkySails GmbH | Bungart M.,SkySails GmbH | Specht B.,Anurac
Green Energy and Technology | Year: 2013

In this paper the authors present basic considerations on conceptual kite design in terms of overall system performance of an airborne wind energy system. This kite design process has been developed at SkySails GmbH for the design of large scale traction kites for sea-going vessels. All aspects are first presented in a brief discussion and then applied to the SkySails kite system. Further examples are provided where applicable. This chapter starts by introducing theoretical approaches for determining maximum system performance and certain other aspects of kite aerodynamics with respect to the SkySails kite system. An overview of the limitations considered during the kite design process is also presented. In the following sections, the in uence of kite steering, launch and landing is discussed. Further, structural weight aspects are addressed. The last sections deal with the implications of ground handling on kites. © Springer-Verlag Berlin Heidelberg 2013.


Fritz F.,SkySails GmbH
Green Energy and Technology | Year: 2013

SkySails develops and markets large automated towing kite systems for the propulsion of ships and for energy generation. Since 2008 pilot customer vessels have been operating propulsion kites in order to reduce fuel costs and emissions. In this contribution the SkySails towing kite technology is introduced and an overview over its core components kite, control pod, towing rope, and launch and retrieval system is provided. Subsequently the principles of force generation and propulsion are summarized. In the following part the system's application to airborne wind energy generation is presented, where the kite forces are used to pull the towing rope off a drum, powering a generator in the process. When the maximum tether length is reached, the kite is reeled back to the starting point using the generator as a motor. A functional model was constructed and successfully tested to prove the positive energy balance of this so-called pumping mode energy generation experimentally. An evaluation of the technology's market potential, particularly for offshore wind farms, concludes the contribution. © Springer-Verlag Berlin Heidelberg 2013.


Erhard M.,SkySails GmbH | Strauch H.,SkySails GmbH
Control Engineering Practice | Year: 2015

Energy harvesting based on tethered kites benefits from exploiting higher wind speeds at higher altitudes. The setup considered in this paper is based on a pumping cycle. It generates energy by winching out at high tether forces, driving an electrical generator while flying crosswind. Then it winches in at a stationary neutral position, thus leaving a net amount of generated energy.The focus of this paper is put on the flight control design, which implements an accurate direction control towards target points and allows for a flight with an eight-down pattern. An extended overview on the control system approach, as well as details of each element of the flight controller, is presented. The control architecture is motivated by a simple, yet comprehensive model for the kite dynamics.In addition, winch strategies based on an optimization scheme are presented. In order to demonstrate the real world functionality of the presented algorithms, flight data from a fully automated pumping-cycle operation of a small-scale prototype are given. The setup is based on a 30m2 kite linked to a ground-based 50kW electrical motor/generator by a single line. © 2015 Elsevier Ltd.


The invention relates to an aerodynamic wind energy conversion device and a method for controlling such a device. The aerodynamic wind energy conversion device comprises an aerodynamic wing; at least a first tractive line and a second tractive line; wherein ends of the tractive lines are connected to line connection points located at the aerodynamic wing; at least a first and a second reefing point located across the aerodynamic wing and is characterized in that the length of the second tractive line is shorter than the length of the first tractive line; and wherein the first reefing point is spaced from the first line connection point in a first reefing distance and the second reefing point is d spaced from the second line connection point in a second reefing distance, such that the second reefing distance is longer than the first reefing distance.

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