Noise and vibration is a major issue in helicopters. Active and passive control systems have been used in attempts to reduce these effects. This paper presents a system for the active control of a rotor blade anhedral tip flap with the intention of reducing noise due to Blade Vortex Interaction (BVI). In the experiments, the flap hinge is represented by a shaft and actuated by Shape Memory Alloy (SMA) wires. Closed-loop control of the angular position of the shaft is accomplished first with a single SMA wire, and next with two antagonistic SMA wires. The results of these experiments are presented and discussed. To get a rough approximation of the number of SMA wires that are required, the aerodynamic loads imposed at the anhedral tip flap are estimated by a one dimensional analysis. The setup is then modeled using the SMA constitutive and transformation equations as well as the equations of equilibrium of the whole system. The resulting system of nonlinear equations is solved using a fixed point solution method. The close agreement between the output of the simulations and the corresponding experimental results demonstrates the validity of the model.

16th International Conference on Adaptive Structures and Technologies, ICAST
Department of Mechanical and Aerospace Engineering

Lynch, B. (Brian), Ghorashi, M. (Mehrdaad), & Nitzsche, F. (2006). On the use of shape memory alloy wires for anhedral angle control in helicopter rotor blades. In 16th International Conference on Adaptive Structures and Technologies (pp. 53–60).