Deicing using piezoelectric actuators is considered as a potential solution to the development of low-energy ice protection systems for rotorcraft. This type of system activates resonant frequencies of a structure using piezoelectric actuators to generate sufficient stress to break
the bond between the ice and the substrate. First, a numerical method was validated to assist the design of such systems. Numerical simulations were performed for the case of a flat plate and validated experimentally. The model was then used to study important design parameters such as actuator
positioning and activation strategies, and it was concluded that positioning actuators at antinode locations, and activating them in phase with those antinodes to obtain maximum displacements for a given vibration mode. The findings were then used to apply piezoelectric deicing to structures
more representative of a helicopter rotor blade. The method was implemented on a thinned Bell 206 main rotor blade and a Bell 206 tail rotor blade. Deicing performance was demonstrated in an icing wind tunnel. Power input to the actuators was below 19 kW/m2 (12 W/inch2)
for all structures.
Significant structural vibration is an undesirable characteristic in helicopter flight that leads to structural fatigue, poor ride quality for passengers and high acoustic signature for the vehicle. Previous Individual Blade Control (IBC) techniques based on piezoelectric actuator schemes to reduce these effects have been hindered by electromechanical limitations of piezoelectric actuators. The Smart Spring is an active tunable vibration absorber using the IBC approach to adaptively alter the ''structural impedance'' at the blade root. In the paper, a mathematical model was developed to determine the response of the absorber under harmonic excitation. An adaptive notch algorithm using a DSP platform was developed to implement vibration control. Reference signal synthesis techniques were used to automatically track the shift in the fundamental vibratory frequency due to variations in flight conditions. Experiments using a mechanical shaker and wind tunnel tests conducted on the proof-of-concept hardware achieved significant vibration suppression at harmonic peaks. Investigation verified the capability of the Smart Spring to suppress multiple harmonic components in rotor vibration through active impedance control.
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