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As part of the Ultra High Aspect Ratio Wing Advanced Research and Designs (U-HARWARD) project, funded by CS2JU, various gust load alleviation (GLA) technologies have been developed and studied. GLA plays a crucial role in the development of new generation ultra-high aspect ratio wings (UHARWs), as it reduces gust loads, thereby decreasing the structural weight of the wing and, consequently, the entire aircraft. This weight reduction enhances overall aircraft efficiency, enabling a higher aspect ratio. GLA technologies are categorized into passive systems, which require no active intervention, and active systems, where control surfaces redistribute the aerodynamic loads. In this study, passive GLA was implemented using a folding wing tip (FWT) developed by the University of Bristol, while active GLA employed a Static Output Feedback controller developed by Politecnico di Milano. Both approaches were compared against a baseline aircraft configuration. A flutter assessment confirmed that FWT does not introduce aeroelastic instabilities, ensuring the aircraft remains flutter-free across its flight envelope. A thorough comparison of load envelopes, based on nearly 2000 load cases across different flight points and mass configurations, was conducted in compliance with CS25 regulations, examining both positive and negative gust conditions. The results show a possible 15% reduction in the dynamic load envelope for both passive and active solutions. Using NeOPT, a hybrid finite element (FE) model was developed, with a detailed global FEM (GFEM) for the wingbox and stick elements for other components. Linear gust analyses in Nastran, with the hinge locked and released, provided high-fidelity results, comparing wing failure indexes and demonstrating the effectiveness of the FWT solution. [ABSTRACT FROM AUTHOR]

As part of the Ultra High Aspect Ratio Wing Advanced Research and Designs (U-HARWARD) project, funded by CS2JU, various gust load alleviation (GLA) technologies have been developed and studied. GLA plays a crucial role in the development of new generation ultra-high aspect ratio wings (UHARWs), as it reduces gust loads, thereby decreasing the structural weight of the wing and, consequently, the entire aircraft. This weight reduction enhances overall aircraft efficiency, enabling a higher aspect ratio. GLA technologies are categorized into passive systems, which require no active intervention, and active systems, where control surfaces redistribute the aerodynamic loads. In this study, passive GLA was implemented using a folding wing tip (FWT) developed by the University of Bristol, while active GLA employed a Static Output Feedback controller developed by Politecnico di Milano. Both approaches were compared against a baseline aircraft configuration. A flutter assessment confirmed that FWT does not introduce aeroelastic instabilities, ensuring the aircraft remains flutter-free across its flight envelope. A thorough comparison of load envelopes, based on nearly 2000 load cases across different flight points and mass configurations, was conducted in compliance with CS25 regulations, examining both positive and negative gust conditions. The results show a possible 15% reduction in the dynamic load envelope for both passive and active solutions. Using NeOPT, a hybrid finite element (FE) model was developed, with a detailed global FEM (GFEM) for the wingbox and stick elements for other components. Linear gust analyses in Nastran, with the hinge locked and released, provided high-fidelity results, comparing wing failure indexes and demonstrating the effectiveness of the FWT solution.

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Abstract Individual pitch control has shown great capability of alleviating the oscillating loads experienced by wind turbine blades due to wind shear, atmospheric turbulence, yaw misalignment, or wake impingement. This work presents a novel controller structure that relies on the separation of low‐level control tasks and high‐level ones. It is based on a neural network that modulates basic periodic pitch angle signals. This neural network is trained with reinforcement learning, a trial and error way of acquiring skills, in a low‐fidelity environment exempt from turbulence. The trained controller is further deployed in large eddy simulations to assess its performances in turbulent and waked flows. Results show that the method enables the neural network to learn how to reduce fatigue loads and to exploit that knowledge to complex turbulent flows. When compared to a state‐of‐the‐art individual pitch controller, the one introduced here presents similar load alleviation capacities at reasonable turbulence intensity levels, while displaying very smooth pitching commands by nature.

Elastic instabilities have traditionally been considered a failure mechanism; however, recent years have seen numerous studies exploiting instabilities as a means to achieve structural functionality. By contrast, interacting instabilities and compound buckling are still largely viewed as a failure mechanism. In this paper, we show that interacting instabilities can also be exploited to achieve bespoke functionality. We focus on 'sequential instabilities', whose associated critical points cannot both lie on a fundamental equilibrium path. We obtain sequential instabilities by combining canonical bifurcations, (e.g. limit point, pitchfork) as building-blocks. Initially, this concept is explored through simple bar-and-spring models that are found to have several properties not exhibited by the building blocks from which they are constructed. Further, the utility of the building block approach, and that of sequential, interacting instabilities, is demonstrated through the development of a morphing structure which must rapidly deploy after a critical input displacement is attained, and meet specific post-deployment stiffness requirements. Two design concepts are proposed, each comprising building blocks to mirror the fundamental working principles identified through the bar-and-spring models. Finite-element models of the design solutions are presented, demonstrating how the designs positively use sequential, interacting instabilities in order to meet the challenging requirements of the application. This work extends the contextual framework of instabilities that can be used to create structures with novel functionality. [ABSTRACT FROM AUTHOR]

To increase the power yield, wind turbines have significantly grown in the last decades. Today, this growth is more and more limited by the weight of the structures and fatigue loads. To compensate these loads, especially flapwise root bending moments, trailing edge flaps can be used. They can change the lift of the blade with little delay to equalize the aerodynamic lift and by this reduce the fatigue amplitude. Such a trailing edge flap has been designed, developed, built and experimentally tested. It uses a flexible, morphing design to seal the entire mechanics against environmental influences, such as rain, dust, or insects. Therefore a design made from glass fiber reinforced plastics in combination with elastomer materials is used. In this paper the design process from the concept to two consecutive demonstrators is presented. Both are tested in the laboratory for their morphing characteristics. [ABSTRACT FROM AUTHOR]

Bend-twist coupling (BTC), a method of passive load alleviation for turbine blade, has a significant influence on blade mechanical properties. The coupling behavior between bending and twisting motions stems from the material anisotropy in blade laminate or from the unique blade geometry such as sweep, deflection, and pre-bending. The material-based approach is employed in this research to determine influence regularity of BTC design on blade mechanical properties. To begin with, the blade property analysis tool PreComp that integrates a shear flow method with the classical laminate theory is adopted to compute the cross-sectional stiffnesses of the blades with different degree of BTC effect. Next, the bend-twist coupling coefficients for the BTC blades with different fiber orientation are calculated. Finally, the remaining mechanical properties including static performance, modal characteristics and buckling limits for different BTC blades are determined by the finite element method and the influence of changes in the degree of BTC effect on all these mechanical properties is further evaluated. The results show that the BTC effect markedly influences the different mechanical properties of the blade in different patterns. The 20° BTC blade has the highest BTC coefficient and the edgewise BTC coefficient at 100 m is 2.5 times higher than the flapwise BTC coefficient, while the maximum value of the torsional modal frequency of 3.8429 Hz and the greatest critical buckling load of 4328.1 kN corresponds to the 10° BTC blade and the 15° BTC blade respectively. [ABSTRACT FROM AUTHOR]

Summary Minimising tower loads is a key issue for the optimal operation and cost‐effective design of wind turbines. Light detection and ranging (LIDAR) technologies enable the measurement of free wind ahead of the rotor and the addition of new feedforward controllers to the traditional control loops, improving the performance in terms of generator speed regulation and load reduction. This paper presents a design procedure based on plant inversion at a set of key frequencies. Tower base longitudinal bending moment is considered the main output of the system. Although the minimisation of tower base loads is the main objective of the design, good results are obtained in terms of generator speed regulation and pitch actuation as well. The methodology has been tested in the well‐known NREL 5MW wind turbine. Results have been obtained for different LIDAR configurations in order to quantify the loss of performance due to measurement errors. In all cases, the feedforward control behaves better than the baseline case.

The effectiveness of trailing-edge flaps and microtabs in damping 1P-3P loads has been proven through a series of research work during the past decade. This paper presents the results of an investigation into the effectiveness of these devices in power enhancement and power control for responding to the issue of where these devices can be used with dual function of load and power control on a medium size turbine. The 300 kW-AWT27 wind turbine is used as the base wind turbine and the effects of adding trailing-edge flaps and string of microtabs of different lengths positioned at different span locations on the aerodynamic performance of the rotor are studied. In each case, the wind turbine simulator WTSim is used to obtain the aerodynamic performance measures. In the next step, the original blade twist is redesigned to ensure that the blade is optimized upon the addition of these active flow controllers. It is found that blades equipped with flaps can increase the annual average power and reduce the blade loading at the same time for constant speed and variable speed generators. Power enhancement is more visible on constant speed rotors, while load reduction is more significant on variable speed rotors. To achieve constant speed rotors, an average power enhancement of around 12 % is achieved for a flap of size 25 % of the blade span located at about 72 % of the blade span. Microtabs are less effective in power control and can improve the produced power only by a few percentage points.

A physics-based optimisation framework is developed to investigate the potential advantages of novel technologies on the energy efficiency of a midrange passenger aircraft. In particular, the coupled-adjoint aerostructural analysis and optimisation tool FEMWET is modified to study the effects of active flow control at different load cases for conventional and unconventional wing configurations. This multidisciplinary design optimisation (MDO) framework presents the opportunity to optimise the wing considering static aeroelastic effect and, by its gradient-based method, save substantial computational time compared to high-fidelity tools, keeping a satisfying level of accuracy. Two different configurations are analysed: a forward- and backward-swept wing aircraft, developed inside the Cluster of Excellence SE2A (Sustainable and Energy-Efficient Aviation). The forward-swept configuration is sensitive to the aeroelastic stability effect, and the backward configuration is influenced by the aileron constraint. They may lead to a weight increment. Sensitivity studies show the possible role of key parameters on the optimisation results. The highest fuel weight reduction achievable for the two configurations is 5.6% for the forward-swept wing and 9.8% for the backward configuration. Finally, both optimised wings show higher flexibility. [ABSTRACT FROM AUTHOR]

This article presents the application of aeroelastic tailoring in the design of wings for a flying demonstrator, as well as the validation of the design methodology with flight test results. The investigations were performed in the FLEXOP project (Flutter Free Flight Envelope Expansion for Economical Performance Improvement), funded under the Horizon 2020 framework. This project aimed at the validation of methods and tools for active flutter control, as well as at the demonstration of the potential of passive load alleviation through composite tailoring. The technologies were to be demonstrated by the design, manufacturing and flight testing of an unmanned aerial vehicle of approximately 7 m wingspan. This article addresses the work towards the load alleviation goals. The design of the primary load-carrying wing-box in this task is performed using a joint DLR–TU Delft optimization strategy. Two sets of wings are designed in order to demonstrate the potential benefits of aeroelastic tailoring—first, a reference wing in which the laminates of the wing-box members are restricted to balanced and symmetric laminates; second, a tailored wing in which the laminates are allowed to be unbalanced, hence allowing for the shear–extension and bending–torsion couplings essential for aeroelastic tailoring. Both designs are numerically optimized, then manufactured and extensively tested to validate and improve the simulation models corresponding to the wing designs. Flight tests are performed, the results of which form the basis for the validation of the applied aeroelastic tailoring approach presented in the article. [ABSTRACT FROM AUTHOR]

Individual pitch control has shown great capability of alleviating the oscillating loads experienced by wind turbine blades due to wind shear, atmospheric turbulence, yaw misalignment, or wake impingement. This work presents a novel controller structure that relies on the separation of low‐level control tasks and high‐level ones. It is based on a neural network that modulates basic periodic pitch angle signals. This neural network is trained with reinforcement learning, a trial and error way of acquiring skills, in a low‐fidelity environment exempt from turbulence. The trained controller is further deployed in large eddy simulations to assess its performances in turbulent and waked flows. Results show that the method enables the neural network to learn how to reduce fatigue loads and to exploit that knowledge to complex turbulent flows. When compared to a state‐of‐the‐art individual pitch controller, the one introduced here presents similar load alleviation capacities at reasonable turbulence intensity levels, while displaying very smooth pitching commands by nature. [ABSTRACT FROM AUTHOR]

In recent years, load alleviation technologies have been more widely used in transport aircraft. For aircraft already in service, load alleviation can contribute in extending the fatigue life, or enable small configurational changes. If load alleviation is considered in the aircraft design process, the structural mass of the aircraft can be reduced. This paper investigates various maneuver and gust load alleviation algorithms as well as potential future technologies regarding flight operation, turbulence forecast and material science, and it evaluates the mass reduction that can be achieved. In doing so, a long-range transport aircraft was taken as the reference, and the considered load case conditions were 1-cos gusts, maneuvers and quasi-steady landing. Based upon the loads, the composite structure of the lifting surfaces was optimized, while the secondary masses as well as the wing planform were kept unchanged. With all technologies implemented, a reduction of the wing box mass by 26.5% or 4.4% of the operating empty mass could be achieved. [ABSTRACT FROM AUTHOR]

Summary: Minimising tower loads is a key issue for the optimal operation and cost‐effective design of wind turbines. Light detection and ranging (LIDAR) technologies enable the measurement of free wind ahead of the rotor and the addition of new feedforward controllers to the traditional control loops, improving the performance in terms of generator speed regulation and load reduction. This paper presents a design procedure based on plant inversion at a set of key frequencies. Tower base longitudinal bending moment is considered the main output of the system. Although the minimisation of tower base loads is the main objective of the design, good results are obtained in terms of generator speed regulation and pitch actuation as well. The methodology has been tested in the well‐known NREL 5MW wind turbine. Results have been obtained for different LIDAR configurations in order to quantify the loss of performance due to measurement errors. In all cases, the feedforward control behaves better than the baseline case. [ABSTRACT FROM AUTHOR]

A new method for predicting manoeuvre loads on a large transport aircraft with a swept-back wing and a load alleviation system based on control surface deflections is developed. For this purpose, three-dimensional Reynolds-averaged Navier–Stokes (RANS) simulations of the rigid wing–fuselage configuration are performed while the aerodynamics of the tailplane are estimated by means of handbook methods. For a closer analysis, different quasi-steady pitching manoeuvres are chosen based on the CS-25 regulations. One of these manoeuvres is also simulated with active load alleviation, leading to a reduction in the wing-root bending moment by more than 40%. Besides demonstrating the potential of the considered load alleviation system, it is shown which manoeuvres are especially critical in this context and which secondary effects come along with load alleviation. [ABSTRACT FROM AUTHOR]

A morphing wing concept allowing for coupled twist-camber shape adaptation is proposed. The design is based on an optimized thickness distribution both spanwise and chordwise to be able to morph the wing sections into targeted airfoil shapes. Simultaneously, the spanwise twist is affected by the actuation. The concept provides a higher degree of control on the lift distribution which can be used for roll control, drag minimization, and active load alleviation. Static deformation and flight tests have been performed to evaluate and quantify the performance of the proposed mechanism. The ground tests include mapped actuated wing shapes, and wing mass and actuation power requirements. Roll authority, load alleviation, and aerodynamic efficiency estimates for different configurations were calculated using a lifting line theory coupled with viscous 2D airfoil data. Roll authority was estimated to be low when compared to a general aviation aircraft while the load alleviation capability was found to be high. Differences between the lift to drag ratio between the reference and morphing wing configurations are considerable. Mass and actuation energy present challenges that can be mitigated. The flight tests were used to qualitatively assess the roll control capability of the prototype, which was found to be adequate. [ABSTRACT FROM AUTHOR]

The dataset presented here regard the analysis reported in the research article entitled “Comparison of different plasma actuation strategies for aeroelastic control on a linear compressor cascade” De Giorgi et al. (2021) [1]. These data are related to the Computational Fluid Dynamics (CFD) assessment of different plasma actuation strategies for the aeroelastic control of an aero engine compressor cascade in subsonic flow conditions. The authors evaluated the accuracy of numerical computations using experimental results. Here, both experimental and raw data of the CFD simulations are presented.

A physics-based optimisation framework is developed to investigate the potential advantages of novel technologies on the energy efficiency of a midrange passenger aircraft. In particular, the coupled-adjoint aerostructural analysis and optimisation tool FEMWET is modified to study the effects of active flow control at different load cases for conventional and unconventional wing configurations. This multidisciplinary design optimisation (MDO) framework presents the opportunity to optimise the wing considering static aeroelastic effect and, by its gradient-based method, save substantial computational time compared to high-fidelity tools, keeping a satisfying level of accuracy. Two different configurations are analysed: a forward- and backward-swept wing aircraft, developed inside the Cluster of Excellence SE2A (Sustainable and Energy-Efficient Aviation). The forward-swept configuration is sensitive to the aeroelastic stability effect, and the backward configuration is influenced by the aileron constraint. They may lead to a weight increment. Sensitivity studies show the possible role of key parameters on the optimisation results. The highest fuel weight reduction achievable for the two configurations is 5.6% for the forward-swept wing and 9.8% for the backward configuration. Finally, both optimised wings show higher flexibility.

This article presents the application of aeroelastic tailoring in the design of wings for a flying demonstrator, as well as the validation of the design methodology with flight test results. The investigations were performed in the FLEXOP project (Flutter Free Flight Envelope Expansion for Economical Performance Improvement), funded under the Horizon 2020 framework. This project aimed at the validation of methods and tools for active flutter control, as well as at the demonstration of the potential of passive load alleviation through composite tailoring. The technologies were to be demonstrated by the design, manufacturing and flight testing of an unmanned aerial vehicle of approximately 7 m wingspan. This article addresses the work towards the load alleviation goals. The design of the primary load-carrying wing-box in this task is performed using a joint DLR–TU Delft optimization strategy. Two sets of wings are designed in order to demonstrate the potential benefits of aeroelastic tailoring—first, a reference wing in which the laminates of the wing-box members are restricted to balanced and symmetric laminates; second, a tailored wing in which the laminates are allowed to be unbalanced, hence allowing for the shear–extension and bending–torsion couplings essential for aeroelastic tailoring. Both designs are numerically optimized, then manufactured and extensively tested to validate and improve the simulation models corresponding to the wing designs. Flight tests are performed, the results of which form the basis for the validation of the applied aeroelastic tailoring approach presented in the article.

In recent years, load alleviation technologies have been more widely used in transport aircraft. For aircraft already in service, load alleviation can contribute in extending the fatigue life, or enable small configurational changes. If load alleviation is considered in the aircraft design process, the structural mass of the aircraft can be reduced. This paper investigates various maneuver and gust load alleviation algorithms as well as potential future technologies regarding flight operation, turbulence forecast and material science, and it evaluates the mass reduction that can be achieved. In doing so, a long-range transport aircraft was taken as the reference, and the considered load case conditions were 1-cos gusts, maneuvers and quasi-steady landing. Based upon the loads, the composite structure of the lifting surfaces was optimized, while the secondary masses as well as the wing planform were kept unchanged. With all technologies implemented, a reduction of the wing box mass by 26.5% or 4.4% of the operating empty mass could be achieved.

Turbulence and gusts cause variations in the aerodynamic forces and moments applied to the structure of aircraft, resulting in passenger discomfort and dynamic loads on the structure that it must be designed to support. By designing Gust Load Alleviation (GLA) systems, two objectives can be achieved: first, realizing higher passenger comfort; and second, reducing the dynamic structural loads, which allows the design of lighter structures. In this paper, a methodology for designing combined feedback/feedforward GLA systems is proposed. The methodology relies on the availability of a wind profile ahead of the aircraft measured by a Doppler LIDAR sensor, and is based on $H_{\infty}$ -optimal control techniques and a discrete-time preview-control problem formulation. Moreover, to allow design trade-offs between those two objectives (to achieve design flexibility) as well as to allow specification of robustness criteria, a variant of the problem using multi-channel $H_{\infty}$ -optimal control techniques is introduced. The methodology developed in this paper is intended to be applied to large aircraft, e.g. transport aircraft or business jets. The simulation results show the effectiveness of the proposed design methodology in accounting for the measured wind profile to achieve the two mentioned objectives, while ensuring both design flexibility and controller robustness and optimality. [ABSTRACT FROM AUTHOR]

Load alleviation control is highly desirable to reduce penalties associated with the added structural mass required to withstand rare load scenarios. This is particularly true for wind turbine designs incorporating long‐span blades. Implementation of compliance‐based morphing structures to modify the lift distribution passively has the potential to mitigate the impact of rare, but integrally threatening, loads on wind turbine blades while limiting the addition of actuation and sensing systems. We present a novel passive load alleviation concept based on a morphing flap exhibiting selective compliance from an embedded bistable element. A multifidelity, aeroelastic tool is used to study the shape adaptability of a morphing flap indicating that passive changes from high lift generation to load alleviation configurations can be achieved by exploiting the energy of the flow. This mechanism offers a method to reduce catastrophic peak loads potentially, thus offering the possibility to lower the overall structural weight of wind turbine blades. [ABSTRACT FROM AUTHOR]

A morphing wing concept allowing for coupled twist-camber shape adaptation is proposed. The design is based on an optimized thickness distribution both spanwise and chordwise to be able to morph the wing sections into targeted airfoil shapes. Simultaneously, the spanwise twist is affected by the actuation. The concept provides a higher degree of control on the lift distribution which can be used for roll control, drag minimization, and active load alleviation. Static deformation and flight tests have been performed to evaluate and quantify the performance of the proposed mechanism. The ground tests include mapped actuated wing shapes, and wing mass and actuation power requirements. Roll authority, load alleviation, and aerodynamic efficiency estimates for different configurations were calculated using a lifting line theory coupled with viscous 2D airfoil data. Roll authority was estimated to be low when compared to a general aviation aircraft while the load alleviation capability was found to be high. Differences between the lift to drag ratio between the reference and morphing wing configurations are considerable. Mass and actuation energy present challenges that can be mitigated. The flight tests were used to qualitatively assess the roll control capability of the prototype, which was found to be adequate.

Lightweight flexible aircraft suffers from unwanted oscillatory vibrations during aircraft manoeuvres. A recently developed distributed-delay signal (DZV) shaper is therefore proposed to be applied as a feedforward controller to alleviate the manoeuvre loads, as an alternative to traditional structural filters used routinely in this context. Structural filters are essentially linear low-pass filters with bandwidth below the significant flexible modes, applied to control signals generated either by the pilot's direct input or by the flight control system. It has been showed that if instead a properly tuned signal shaper is used, better performance can be achieved: first, the target modes are significantly attenuated while the responsiveness of the aircraft is less compromised and secondly, the oscillatory nature of the vibrations are reduced. The high fidelity simulation results on a full scaled dynamic model of a highly flexible blended wing–body (BWB) aircraft show that in comparison to traditional structural filters, signal shapers significantly reduce the wing root loading (forces and moments) which provides potential structural benefits. [ABSTRACT FROM AUTHOR]

Abstract The wind turbine size is nowadays becoming increasingly larger as an effective approach to reduce cost of energy. Passive load control technique is introduced to alleviate the increasing loads on an upscaling wind turbine blade to improve its fatigue life. In this paper, the composite bend-twist coupled blade is investigated and utilized to mitigate the cyclic fluctuating loads in shear wind. The NREL 5-MW blade is firstly inversely redesigned of its composite layup configuration. The fiber on the spar cap is rotated away from the blade axis to implement the bend-twist coupling (BTC). An advanced aeroelastic model of the wind turbine blade is developed to conduct the study. The geometrically exact beam theory is used to account for the large deformation effects, while the tool VABS is utilized to generate the cross-section stiffness matrices. Meanwhile, the free wake lifting surface model is adopted to calculate the aerodynamic loads, which is physically more realistic than the traditionally used BEM method. Based the established model, the influences of BTC on the rotor aerodynamic performance are investigated. Load mitigation effects of the blades with various spar cap fiber angles are evaluated. The influences of coupling region and different wind speeds are also discussed. [ABSTRACT FROM AUTHOR]

It is projected that, in the following years, the wind-energy industry will maintain its rapid growth over the last few decades. Such growth in the industry has been accompanied by the desirability and demand for larger wind turbines aimed at harnessing more power. However, the fact that massive turbine blades inherently experience increased fatigue and ultimate loads is no secret, which compromise their structural lifecycle. Accordingly, this demands higher overhaul-and-maintenance (O&M) costs, leading to higher cost of energy (COE). Introduction of flow-control devices on the wind turbine is a plausible solution to this issue. Flow-control mechanisms feature the ability to effectively enhance/suppress turbulence, advance/delay flow transition, and prevent/promote separation, leading to enhancement in aerodynamic and aeroacoustics performance, load alleviation and fluctuation suppression, and eventually wind turbine power augmentation. These flow-control devices are operated primarily under two schemes: passive and active control. Development and optimization of flow-control devices present the potential for reduction in the COE, which is a major challenge against traditional power sources. This review performs a comprehensive and up-to-date literature survey of selected flow-control devices, from their time of development up to the present. It contains a discussion on the current prospects and challenges faced by these devices, along with a comparative analysis centered on their aerodynamic controllability. General considerations and conclusive remarks are presented after the discussion.

In this study, a wind turbine model with a smart rotor is presented to optimize the sizing parameters of the trailing edge flap (TEF) and design the multi-objective TEF controller. The proposed model consists of TEF actuators, and the aerodynamic, applied load, structural, drive chain, and generator models. Additionally, under standard wind turbine control, the present model shows good agreements with FAST at different wind conditions. At the rated steady wind condition, the TEFs yield exactly the same effects as those elicited by FAST. An approach is proposed using two orthogonal experiments to optimize the TEF sizing parameters for maximizing the TEF effects on blade load alleviation and wind turbine output power smoothness. As a result, a group of optimal TEF sizing parameters is obtained. A multi-objective TEF controller adopting multivariable dynamic matrix control (M–DMC) and nonlinear dynamic matrix control (N–DMC) is used to control the flapwise blade root moment and output power. The simulations indicate that the average reduction rates of the flapwise root moment power spectral density (PSD) of blade 1 are within the range of 87–97% at 1 P frequency, and that the average reduction rate of the generator power standard deviation is within the range of 8–42%. [ABSTRACT FROM AUTHOR]

Abstract A commonly applied method to reduce the cost of wind energy, is alleviating the periodic loads on turbine blades using Individual Pitch Control (IPC). In this paper, a data-driven IPC methodology called Subspace Predictive Repetitive Control (SPRC) is employed. The effectiveness of SPRC will be demonstrated on a scaled 2-bladed wind turbine. An open-jet wind tunnel with an innovative active grid is employed to generate reproducible turbulent wind conditions. A significant load reduction with limited actuator duty is achieved even under these high turbulent conditions. Furthermore, it will be demonstrated that SPRC is able to adapt to changing operating conditions. [ABSTRACT FROM AUTHOR]