In-flight tracking of helicopter rotor blades using shape memory alloy actuators

This paper describes the concept, design, fabrication and control of a shape memory alloy (SMA) wire actuator for tracking helicopter rotor blades while in-flight. A NACA 0012 wing section that has a 12 in chord and span was constructed with a trailing-edge tab with a 4 in span and a 2.4 in chord. A shape memory alloy wire actuator was embedded into the wing section. The actuator consists of a wire clamp, a hinge tube and several pre-strained, 0.015 in diameter SMA (Nitinol) wires. It was shown that with SMA wires that have 3.158% initial pre-strain, a tab deflection of 29° could be obtained.