Institute of Fundamental Technological Research

A concept is presented of gust alleviation in wind turbines by using the blade aerodynamic torsional moment as an actuator for forcing the blade to feather in order to reduce aerodynamic loads. The pitching to feather is implemented through a temporary release of the blade-hub torsional connection after that the blade rotates freely until it reaches the assumed pitch angle. To describe this process, a simple wind turbine model with three elastic blades is formulated and some numerical simulations are performed. The results of the simulations include, among others, the time-history of the out-of-plane blade bending moment in response to the uniform gust, showing that, in this way, it is possible—at least theoretically—to reduce this moment by approximately 2/3 of its peak value. Moreover, the blade pitch angle changes faster than increased by a regular control actuator.

wind turbine, gust alleviation, load reduction

In this paper, the method of center manifold reduction is applied to the limit cycle calculations of a three-dimensional thin airfoil placed in an incompressible flow. Limit cycle oscillations are caused by a cubic structural restoring force corresponding to the aileron rotation. The equation of motion is written as an integro-differential equation and also as an approximate set of ordinary differential equations. Two different implementations of the method of center manifold reduction for these two cases are briefly outlined. It is emphasized, that the formal power series expansions used in the method of center manifold reduction typically diverge and cause the method not to give satisfactory results. An example is presented, when the method of center manifold reduction cannot even qualitatively predict the occurrence of a stable limit cycle of a small amplitude.

Adaptive Impact Absorption focuses on adaptation of energy absorbing structures to actual dynamic loading by using system of sensors detecting and identifying impact in advance and semi -active dissipaters with controllable mechanical properties which enable change of system dynamic characteristics in real time. The article present s a review of research conducted at the Department of Intelligent Technologies of the Institute of Fundamental Technological Research dedicated to applications of systems for Adaptive Impact Absorption. Wide range of presented examples covers pneumatic landing gears, bumpers for offshore towers, wind turbine blade-hub connections and d protective barriers for automotive applications.

adaptive impact absorption, safety engineering, smart structures, optimal control