Nailu Li

Numerical Investigation of Flapwise-Torsional Vibration Model of a Smart Section Blade with Microtab

This study presents a method to develop an aeroelastic model of a smart section blade equipped with microtab. The model is suitable for potential passive vibration control study of the blade section in classic flutter. Equations of the model are described by the nondimensional flapwise and torsional vibration modes coupled with the aerodynamic model based on the Theodorsen theory and aerodynamic effects of the microtab based on the wind tunnel experimental data. The aeroelastic model is validated using numerical data available in the literature and then utilized to analyze the microtab control capability on flutter instability case and divergence instability case. The effectiveness of the microtab is investigated with the scenarios of different output controllers and actuation deployments for both instability cases. The numerical results show that the microtab can effectively suppress both vibration modes with the appropriate choice of the output feedback controller.

Stall Flutter Control of a Smart Blade Section Undergoing Asymmetric Limit Oscillations

Stall flutter is an aeroelastic phenomenon resulting in unwanted oscillatory loads on the blade, such as wind turbine blade, helicopter rotor blade, and other flexible wing blades. Although the stall flutter and related aeroelastic control have been studied theoretically and experimentally, microtab control of asymmetric limit cycle oscillations (LCOs) in stall flutter cases has not been generally investigated. This paper presents an aeroservoelastic model to study the microtab control of the blade section undergoing moderate stall flutter and deep stall flutter separately. The effects of different dynamic stall conditions and the consequent asymmetric LCOs for both stall cases are simulated and analyzed. Then, for the design of the stall flutter controller, the potential sensor signal for the stall flutter, the microtab control capability of the stall flutter, and the control algorithm for the stall flutter are studied. The improvement and the superiority of the proposed adaptive stall flutter controller are shown by comparison with a simple stall flutter controller.

Aeroelastic Vibration Suppression of a Rotating Wind Turbine Blade using Adaptive Control

A mathematic rotating blade model is established with periodic time-varying aerodynamic load, which is simulated by Beddoes-Leishman dynamic stall model. The consequent aeroelastic model is utilized to analyze blade dynamics and design control strategy for blade flutter suppression application. Aeroelastic stability of rotating blade is indicated by open-loop simulation test for critical flutter speed study. It was found that designed Adaptive Controller is capable of restraining flutter vibration with trailing-edge flap, and its robustness and effectiveness are shown by closed-loop tests with a wide range of aerodynamic loads. The stability analysis presents that the stability of the given Adaptive Controller, proved theoretically by Adaptive Stability Theorem.

Flutter Suppression of Rotating Wind Turbine Blade Based on Beddoes-Leishman model using Microtabs

Recent developments in flow control technology have resulted in small-sized, powerefficient devices, as microtabs, which is capable of impacting flow field over rotating wind turbine blade to generate control forces. The model of the rotatory blade is considered as an aeroelastic system with unsteady periodic aerodynamic loads, simulated by BeddoesLeishman stall model. The traditional control technique as PID control can not address the problem of blade fluttering or multiple performance goals arising from wind turbine operation. Therefore, novel approach for control design, as Adaptive Control, is required. The stability of the designed controller is revealed by good performance of simulation results in open-loop and closed-loop tests, showing robustness and effectiveness of the controller in flutter suppression with Microtabs. Moreover, The stability of the feedback system is proved theoretically by the given Adaptive Stability Theorem for periodic time-varying system. The demonstration of the stability theorem is also given by certain cases.

Adaptive Aeroelastic Suppression of a Wind Turbine Blade Using Trailing-edge Flap

The aeroelastic model of a rotating wind turbine blade model is established with periodic time-varying aerodynamic loads, which are stimulated by Beddoes-Leishman dynamic stall model. The proposed model is then used to analyze blade dynamics and design control strategy for blade flutter suppression application. The control strategy is implemented by the Adaptive Controller and the actuator, trailing-edge flap. It was found that the Adaptive Controller is capable of suppressing flutter vibration with trailing-edge flap, and it’s robustness and effectiveness are shown by good closed-loop simulation results with a wide range of aerodynamic loads in Region 2 and Region 3. The stability analysis presents that the stability of the Adaptive Controller can be proved theoretically by Adaptive Stability Theorem.

Aeroelastic Suppression of Wind Turbine Blade Using Trailing-Edge Flap

The variation of aeroelastic system dynamics is treated as the change of time-varying aerodynamic loads along the operation trajectory of a spinning wind turbine. An Adaptive Control scheme is introduced to suppress flutter based on the proposed model. The robustness and effectiveness of Adaptive Control is shown by simulation results. For stability analysis, Adaptive Stability Theorem is proved theoretically by Kalman-Yacubovic Lemma and demonstrated numerically by certain cases.Copyright

Adaptive Control of Flow Over Rotating Wind Turbine Blades Using the Beddoes-Leishman Dynamic Stall Model

A new control problem arises with unsteady flow over large-sized wind turbine blades, bringing a control issue for periodic time-varying systems (PTS). The plant is treated as a pitch and plunge system coupling with the Beddoes-Leishman stall model and Adaptive Control is used to overcome the fluctuation brought by periodic fluctuations of the flow. Floquet Theory is introduced for stability assessment using Runge-Kutta Method. A time-varying version of the adaptive control stability theorem is established. The theorem is demonstrated theoretically and numerically.Copyright