This paper aims to introduce a new approach to optimize the tunable controller parameters of linear parameterizable controllers. The presented approach is frequency-domain based and can therefore directly be used to tune, among others, proportional integral derivative controllers, low/high-pass filters, and notch filters, using a Frequency Response Function of the plant. The approach taken in this paper is to extract the tunable controller parameters into a diagonal matrix gain and absorb the remainder of the controller in the plant. Then, the generalized Nyquist stability criterion is exploited so as to impose stability and H∞ performance specifications on the closed-loop system. It is shown that the approach results in a convex feasibility problem for certain controller cases and can be reformulated such that it can also be used for grey-box system identification. Simulation and experimental examples demonstrate the efficacy of the approach.@en

In this paper, a control architecture for a two-bladed downwind teeterless damped free-yaw wind turbine is developed. The wind turbine features a physical yaw damper which provides damping to the yawing motion of the rotor-nacelle assembly. Individual Pitch Control (IPC)1 is employed to obtain yaw control so as to actively track the wind direction and to reduce the turbine loads. The objectives of both load and yaw control by IPC are conflicting and therefore two decoupling strategies are presented and compared in terms of controller design, stability, and turbine loads. The design of the different controllers and the physical yaw damping are coupled and have a large impact on the turbine loads. It is shown that the tuning of the controllers and the choice of the yaw damping value involve a tradeoff between blade and tower loads. All results have been obtained by high-fidelity simulations of the state-of-the-art 2-B Energy 2B6 wind turbine.@en

In this paper, a control architecture for a two-bladed downwind teeterless damped free-yaw wind turbine is developed. The wind turbine features a physical yaw damper which provides damping to the yawing motion of the rotor-nacelle assembly. Individual Pitch Control (IPC)1 is employed to obtain yaw control so as to actively track the wind direction and to reduce the turbine loads. The objectives of both load and yaw control by IPC are conflicting and therefore two decoupling strategies are presented and compared in terms of controller design, stability, and turbine loads. The design of the different controllers and the physical yaw damping are coupled and have a large impact on the turbine loads. It is shown that the tuning of the controllers and the choice of the yaw damping value involve a tradeoff between blade and tower loads. All results have been obtained by high-fidelity simulations of the state-of-the-art 2-B Energy 2B6 wind turbine.@en

It is vital for an Uninhabited Aerial Vehicle (UAV) to meet contradictory mission requirements originating from the different tasks this type of aircraft has to fulfil. Among the most prominent requirements are manoeuvrability, endurance and range. The ability to switch between configurations that meet these requirements greatly enlarges the range of possible missions. A UAV wing has been developed to demonstrate the capacity to optimize the aerodynamic and structural performance. The wing is equipped with 4 Macro Fibre Composite (MFC) benders that can be controlled individually and each of these MFC benders actuates a section of the wing. It was chosen to use MFC benders as they possess several advantageous properties over conventional piezoceramic benders: they combine a wide frequency bandwidth with large deformations, yielding a high control authority, and they are less sensitive to cracks and failure, making them more robust for aerospace applications. A numerical study was conducted with XFLR5 to determine the optimal configurations of the flap positions for both range and endurance. A wind tunnel study was performed to verify these results. The wide frequency band of the actuators allows using the developed system also for other purposes such as load alleviation. UAVs are often light and fly at low airspeeds, which make them very sensitive to gust excitation. For this purpose the experimental model was equipped with two accelerometers to measure the amplitude of the first two deformation modes. The wing was designed such that the frequency of the first bending dominated mode and the first torsion dominated mode were close to each other. Consequently, a multiple-input multiple-output controller was used to reduce the amplitude of both modes due to a gust loading simultaneously. This was done with both range and endurance optimized flap configurations as steady state conditions. Finally, it was demonstrated during the wind tunnel tests that the variable camber concept provides enough forces and moments to replace the ailerons.@en

It is vital for an Uninhabited Aerial Vehicle (UAV) to meet contradictory mission requirements originating from the different tasks this type of aircraft has to fulfil. Among the most prominent requirements are manoeuvrability, endurance and range. The ability to switch between configurations that meet these requirements greatly enlarges the range of possible missions. A UAV wing has been developed to demonstrate the capacity to optimize the aerodynamic and structural performance. The wing is equipped with 4 Macro Fibre Composite (MFC) benders that can be controlled individually and each of these MFC benders actuates a section of the wing. It was chosen to use MFC benders as they possess several advantageous properties over conventional piezoceramic benders: they combine a wide frequency bandwidth with large deformations, yielding a high control authority, and they are less sensitive to cracks and failure, making them more robust for aerospace applications. A numerical study was conducted with XFLR5 to determine the optimal configurations of the flap positions for both range and endurance. A wind tunnel study was performed to verify these results. The wide frequency band of the actuators allows using the developed system also for other purposes such as load alleviation. UAVs are often light and fly at low airspeeds, which make them very sensitive to gust excitation. For this purpose the experimental model was equipped with two accelerometers to measure the amplitude of the first two deformation modes. The wing was designed such that the frequency of the first bending dominated mode and the first torsion dominated mode were close to each other. Consequently, a multiple-input multiple-output controller was used to reduce the amplitude of both modes due to a gust loading simultaneously. This was done with both range and endurance optimized flap configurations as steady state conditions. Finally, it was demonstrated during the wind tunnel tests that the variable camber concept provides enough forces and moments to replace the ailerons.@en

It is vital for an Uninhabited Aerial Vehicle (UAV) to meet contradictory mission requirements originating from the different tasks this type of aircraft has to fulfil. Among the most prominent requirements are manoeuvrability, endurance and range. The ability to switch between configurations that meet these requirements greatly enlarges the range of possible missions. A UAV wing has been developed to demonstrate the capacity to optimize the aerodynamic and structural performance. The wing is equipped with 4 Macro Fibre Composite (MFC) benders that can be controlled individually and each of these MFC benders actuates a section of the wing. It was chosen to use MFC benders as they possess several advantageous properties over conventional piezoceramic benders: they combine a wide frequency bandwidth with large deformations, yielding a high control authority, and they are less sensitive to cracks and failure, making them more robust for aerospace applications. A numerical study was conducted with XFLR5 to determine the optimal configurations of the flap positions for both range and endurance. A wind tunnel study was performed to verify these results. The wide frequency band of the actuators allows using the developed system also for other purposes such as load alleviation. UAVs are often light and fly at low airspeeds, which make them very sensitive to gust excitation. For this purpose the experimental model was equipped with two accelerometers to measure the amplitude of the first two deformation modes. The wing was designed such that the frequency of the first bending dominated mode and the first torsion dominated mode were close to each other. Consequently, a multiple-input multiple-output controller was used to reduce the amplitude of both modes due to a gust loading simultaneously. This was done with both range and endurance optimized flap configurations as steady state conditions. Finally, it was demonstrated during the wind tunnel tests that the variable camber concept provides enough forces and moments to replace the ailerons.@en

It is vital for an Uninhabited Aerial Vehicle (UAV) to meet contradictory mission requirements originating from the different tasks this type of aircraft has to fulfil. Among the most prominent requirements are manoeuvrability, endurance and range. The ability to switch between configurations that meet these requirements greatly enlarges the range of possible missions. A UAV wing has been developed to demonstrate the capacity to optimize the aerodynamic and structural performance. The wing is equipped with 4 Macro Fibre Composite (MFC) benders that can be controlled individually and each of these MFC benders actuates a section of the wing. It was chosen to use MFC benders as they possess several advantageous properties over conventional piezoceramic benders: they combine a wide frequency bandwidth with large deformations, yielding a high control authority, and they are less sensitive to cracks and failure, making them more robust for aerospace applications. A numerical study was conducted with XFLR5 to determine the optimal configurations of the flap positions for both range and endurance. A wind tunnel study was performed to verify these results. The wide frequency band of the actuators allows using the developed system also for other purposes such as load alleviation. UAVs are often light and fly at low airspeeds, which make them very sensitive to gust excitation. For this purpose the experimental model was equipped with two accelerometers to measure the amplitude of the first two deformation modes. The wing was designed such that the frequency of the first bending dominated mode and the first torsion dominated mode were close to each other. Consequently, a multiple-input multiple-output controller was used to reduce the amplitude of both modes due to a gust loading simultaneously. This was done with both range and endurance optimized flap configurations as steady state conditions. Finally, it was demonstrated during the wind tunnel tests that the variable camber concept provides enough forces and moments to replace the ailerons.@en

It is vital for an Uninhabited Aerial Vehicle (UAV) to meet contradictory mission requirements originating from the different tasks this type of aircraft has to fulfil. Among the most prominent requirements are manoeuvrability, endurance and range. The ability to switch between configurations that meet these requirements greatly enlarges the range of possible missions. A UAV wing has been developed to demonstrate the capacity to optimize the aerodynamic and structural performance. The wing is equipped with 4 Macro Fibre Composite (MFC) benders that can be controlled individually and each of these MFC benders actuates a section of the wing. It was chosen to use MFC benders as they possess several advantageous properties over conventional piezoceramic benders: they combine a wide frequency bandwidth with large deformations, yielding a high control authority, and they are less sensitive to cracks and failure, making them more robust for aerospace applications. A numerical study was conducted with XFLR5 to determine the optimal configurations of the flap positions for both range and endurance. A wind tunnel study was performed to verify these results. The wide frequency band of the actuators allows using the developed system also for other purposes such as load alleviation. UAVs are often light and fly at low airspeeds, which make them very sensitive to gust excitation. For this purpose the experimental model was equipped with two accelerometers to measure the amplitude of the first two deformation modes. The wing was designed such that the frequency of the first bending dominated mode and the first torsion dominated mode were close to each other. Consequently, a multiple-input multiple-output controller was used to reduce the amplitude of both modes due to a gust loading simultaneously. This was done with both range and endurance optimized flap configurations as steady state conditions. Finally, it was demonstrated during the wind tunnel tests that the variable camber concept provides enough forces and moments to replace the ailerons.@en

At present, the cost of offshore wind energy does not meet the level of onshore wind and fossil-based energy sources. One way to extend the turbine lifetime, and thus reduce cost, is by reduction of the fatigue loads of blades and other turbine parts using Individual Pitch Control (IPC). This type of control, which is generally implemented by feedback control using the MultiBlade Coordinate transformation on blade load measurement signals, is capable of mitigating the most dominant periodic loads. The main goal of this article is to develop a self-optimizing feedforward IPC strategy for a two-bladed wind turbine to reduce actuator duty cycle and reduce the dependency on blade load measurement signals. The approach uses blade load measurement data only initially for tuning of the feedforward controller, which is scheduled on the rotor azimuth angle and wind speed. The feedforward strategy will be compared to the feedback implementation in terms of load alleviation capabilities and actuator duty cycle. Results show that the implementation is capable of learning the optimal feedforward IPC controller in constant and turbulent wind conditions, to alleviate the pitch actuator duty cycle, and to considerably reduce harmonic fatigue loads without the need for blade load measurement signals after tuning.@en

Traditionally, wind turbine controllers are designed using first principles or linearized or identified models. The aim of this paper is to show that with an automated, online, and model-free tuning strategy, wind turbine control performance can be significantly increased. For this purpose, iterative feedback tuning (IFT) is applied to two different turbine controllers: drivetrain damping and collective pitch control. The results, obtained by high-fidelity simulations using the NREL 5MW wind turbine, indicate significant performance improvements over baseline controllers, which were designed using classical loop-shaping techniques. It is concluded that iterative feedback tuning of turbine controllers has the potential to become a valuable tool to improve wind turbine performance.@en

Wind turbine load alleviation has traditionally been addressed in the literature using either full-span pitch control, which has limited bandwidth, or trailing-edge flap control, which typically shows low control authority due to actuation constraints. This paper combines both methods and demonstrates the feasibility and advantages of such a combined control strategy on a scaled prototype in a series of wind tunnel tests. The pitchable blades of the test turbine are instrumented with free-floating flaps close to the tip, designed such that they aerodynamically magnify the low stroke of high-bandwidth actuators. The additional degree of freedom leads to aeroelastic coupling with the blade flexible modes. The inertia of the flaps was tuned such that instability occurs just beyond the operational envelope of the wind turbine; the system can however be stabilised using collocated closed-loop control. A feedforward controller is shown to be capable of significant reduction of the deterministic loads of the turbine. Iterative feedforward tuning, in combination with a stabilising feedback controller, is used to optimise the controller online in an automated manner, to maximise load reduction. Since the system is non-linear, the controller gains vary with wind speed; this paper also shows that iterative feedforward tuning is capable of generating the optimal gain schedule online.@en