Airborne wind energy is the theme of four different public presentations at Delft University of Technology during the busy month of December.

• Alexandre Trofino, Marcelo De Lellis and Ramiro Saraiva of the Federal University of Santa Catarina (UFSC), Brasil, will be presenting on two sub-topics, Thursday 5 December from 11:45-12:45h in room B, Faculty of Aerospace Engineering:
  Turning Angle Control of Power Kites for Wind Energy
  An alternative model for the turning angle dynamics of a power kite is presented, proposing a control scheme with two loops. The identification of the parameters of the model is discussed. The outer loop uses Bernoulli’s lemniscate as an offline-optimized trajectory to generate a reference for the inner loop, which controls the turning angle through feedback linearization. Simulation results for electric power generation and control performance are presented, accounting also for wind turbulence.
  Passive Phase Design of a Pumping Kite Wind Generator
  A maneuver design method for the passive phase of a pumping kite generator is presented. The design is based on a two-dimensional downwind kite model. A robustness index against wind turbulence is proposed and analyzed, and an offline algorithm for generating a reference for the flight trajectory, which maximizes the cycle power, is presented. Controllers for tracking this flight reference are designed, followed by a discussion on simulation results.
• Edwin Schreuder will present his MSc research, Thursday 12 December from 10.00-10.45h in room F, Faculty Mechanical, Maritime and Materials Engineering (3mE), Mekelweg 2
  Improving winch control performance in kite power systems using gain scheduling and a compliant element
  To increase the power output of the kite power system demonstrator of the TU Delft, an improved winch control design is required. Measurements of the current system showed especially poor performance of the tether force during the reel out phase of the pumping cycle and revealed a substantial propagation delay in the control loop. As a maximum tether force is to be respected, a force tracking gain scheduled controller state feedback controller was proposed for a nonlinear model. It was found that the stability of the system is compromised for high enough system delay. By extending the system with a compliant element between the tether and the kite, a larger delay can be allowed before instability occurs while its tracking behaviour is reversed. This allows for increased power extraction.
• Eric van der Knaap will present his MSc research, Friday 13 December from 14.30-15.45h in room C, Faculty of Aerospace Engineering, Kluyverweg 1
  A particle system approach for modelling flexible wings with inflatable support structures
  The goal of this research is to investigate if the bending behaviour of inflatable beams can be modelled accurately by a particle system approach and how such a model affects the computational costs. The inflatable beam is segmented into a number of discrete elements which are connected by rotational joints which include rotary springs that approximate the non-linear bending stiffness. A semi-rigid element is introduced to approximate each discrete beam segment. Reaction moments in the rotary springs are translated to reaction forces on the particles of two connecting pyramids. The computation costs are measured by counting floating point operations. A sensitivity analysis is performed on the computational costs induced by adding normal springs, rotary springs, particles, semi-rigid elements and iterations in the solver.
• Jelle Wijnja will present his MSc research, Wednesday 18 December from 9.30-10.15h in room C, Faculty of Applied Sciences, Department of Chemical Engineering, Julianalaan 136
  Aeroelastic modelling of a large airborne wind turbines
  In this Master's thesis a tether-bridle module is developed for the aeroelastic simulation code ASWING. The tether is simulated as a straight, flexible spring with user defined mass, drag area and spring stiffness. The bridles are simulated as perfectly rigid and connect the lifting surface to the tether. With this additional module, ASWING can predict aeroelastic behaviour for tethered flight. In this Master's thesis the Makani airborne wind turbine is analysed for divergence, aileron effectiveness and reversal and flutter. Aileron effectiveness and flutter are critical, but can be resolved by relatively small adjustments in wing lay-up and geometry.