부산대학교 도서관

A system for actively controlling the span-wise rotational twist of a hollow beam along its longitudinal axis, including a hollow beam structure having a leading edge and a trailing edge region, the beam being split along its length, an actuator arranged between split surfaces of the beam, the actuator adapted to move the split surfaces in a longitudinal direction relative to each other, inducing a twist in the beam. In one embodiment, the actuator is a plurality of thermal expansion material blocks alternating with mechanical compression blocks, the thermal expansion material blocks being heated to cause expansion in the spanwise longitudinal direction. Other alternative actuators include a rotary actuators such as a threaded screw, piezoelectric or magnetostrictive blocks, a hydraulic actuator, or a pneumatic actuator. In an embodiment, the beam is an airfoil shape.