Multiphysics modeling and harmonic input correlation analysis for active twist rotors: Load reduction with macrofiber piezoelectric composites

The current helicopters still endure high vibration due to the alternating aerodynamic loads, causing component fatigue and passenger discomfort. However, the capability of traditional passive control is limited by the narrow operating frequency bandwidth and large additional component weight. The active twist rotor technology based on macrofiber piezoelectric composites offers a potential solution for reducing rotor vibratory loads. To explore the mechanism of loads reduction via active twist and analyze the effects of related input parameters on the control capability, a novel comprehensive dynamics analysis model for multilayer anisotropic composite material blades integrated with active materials is developed. This model accounts for the coupling effect of force and electric fields through modifying the section force-strain constitutive equation. The control effects of different piezoelectric fiber ply orientation angles with ( N b – 1)P, N b P and ( N b +1)P inputs on N b P hub vibratory loads are first systematically quantified. The results show that the ( N b – 1)P voltage has the best control capability on the N b P hub rolling and pitching vibratory loads, achieving reductions exceeding 92.07%. Meanwhile, the N b P voltage has the best control capability on the N b P hub vertical and yawing vibratory loads, achieving reductions exceeding 95.34%. The reductions in the N b P hub vertical and yawing vibratory loads result from the decrease in the N b P blade lift and drag amplitudes. The reductions in the N b P hub rolling and pitching vibratory loads are primarily from the decrease in the ( N b – 1)P aerodynamic amplitudes. Nevertheless, the ( N b +1)P blade lift may increase or decrease, depending on the harmonic order of the control input. The hierarchical attenuation patterns in aerodynamics amplitude modifications under active twist inputs are analyzed in detail, and the control capabilities of the ( N b – 1)P, N b P and ( N b +1)P inputs on the N b P hub vibratory loads are quantitatively evaluated using the Spearman’s rank correlation coefficient for the first time.