• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.41 no.6
• /
• pp.448-457
• /
• 2013

This paper presents the design of an active flutter suppression system for flexible wing using sliding mode control method. The aerodynamic force generated by the motion of a flexible wing control surface is utilized as control force. For this purpose, aeroservoelastic model is formulated by blending aeroelastic model, control surface actuator model, and gust model. A sliding mode controller is designed for active flutter suppression on the aeroservoelastic model in conjunction with Kalman filter that estimates the system states based on the measured output. The performance of the designed controller is demonstrated via numerical simulation for the representative flexible wing model.

• International Journal of Aeronautical and Space Sciences
• /
• v.10 no.2
• /
• pp.52-62
• /
• 2009

A three-dimensional compressible Navier-Stokes solver, KFLOW, using overlapped grids has recently been developed to simulate unsteady flow phenomena over helicopter rotor blades. The blade-vortex interaction is predicted for a descending flight using measured blade deformation data. The effects of computational grid resolution and azimuth angle increments on airloads were examined, and computed airloads and vortex trajectories were compared with HART-II wind tunnel data. The current method predicts the BVI phenomena of blade airloads reasonably well. It is found from the present study that a peculiar distribution of vorticity of tip vortices in an approximate azimuth angle range of 90 to 180 degrees can be explained by physics of the shear-layer interaction as well as the dissipation of numerical schemes.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.10a
• /
• pp.220-225
• /
• 2013

In this study, active control system using sliding mode control method is presented to achieve the gust response alleviation of a three-dimensional flexible wing model. For this purpose, aeroservoelastic model which is composed of aeroelastic plant, control surface actuator model, and gust model depicting the atmospheric turbulence is formulated in the state space. The aerodynamic force generated by the motion of a trailing edge control surface of a flexible wing is made use of as control means. An active control system combining state feedback sliding mode controller and state estimator based on measured responses such as wing tip acceleration and wing root strain is designed for gust response alleviation of a flexible wing aeroservoelastic model. The performance of the controller designed is demonstrated via numerical simulation for the representative flexible wing model under gust loading conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.5
• /
• pp.281-294
• /
• 2015

In order to quantitatively estimate the nonlinear destructive interaction of wave load with wind load, which is very vital for the optimal design of offshore wind energy converter, we carried out a hydraulic model test and wind tunnel test. As a substructure of offshore wind energy converter, we would deploy the monopile, which is popular due to its easiness in construction. Based on the simulation using Monte Carlo simulation using Kaimal spectrum and cross spectrum, the instantaneous maximum wind velocity is adjusted to 10 m/s. And, considering the wave conditions of the Western Sea where a pilot wind farm is planned to be constructed, $H_s=0.1m$, 0.15 m, 0.2 m is carefully chosen. It turns out that the nonlinear destructive interaction between the wind and wave loads acting on the offshore wind energy converter is more clearly visible at rough seas rather than at mild seas, which strongly support our deduction that a Large eddy, a swirling vortex developed near the bumpy water surface in the opposite direction of the wind, is the driving mechanism underlying nonlinear destructive interaction between the wind and wave loads.