Smart Material-Actuated Rotor Technology – SMART

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Abstract
Vibration, noise, and aerodynamic design compromises are primary barriers to further improvements in effectiveness of the helicopter. The MD900 light utility helicopter main rotor system is modified to include in-blade smart material actuation for active control. A piezoelectric (PE)-driven trailing edge flap is used for vibration, noise, and aerodynamic performance improvements. A shape memory alloy (SMA)-driven trailing edge trim tab is used for in-flight blade tracking. Sizing and conceptual design of an active flap and trim tab system for the MD900 helicopter were completed. Several two-dimensional airfoil and flap/tab models were wind tunnel tested and an aerodynamic database was established. Structural samples of the flap actuator mounts, flap section, tab, and full-span flap were fabricated and successfully tested. Several prototype actuators were developed and extensively tested to establish their performance and robustness in the dynamic operating environment. The flap actuator uses two biaxial PE stack columns, operating in a push pull mode, a column mid-support, and a stroke amplification mechanism. The tab actuator uses two biaxial SMA tubes for actuation/bias, an SMA-activated lock for power-off operation, and integrated microprocessor control electronics. Results to date confirm that smart material in-blade active control of a rotor is feasible and offers significant performance and cost benefits. Projected payoffs from reduced vibrations and noise as well as in-flight tracking include improved component lives, reduced maintenance and improved crew, passenger, and community acceptance.

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