Optimal active twist input scenario for rotor performance improvement and vibration reduction

Abstract

In this paper, the best actuation scenario is sought using a multitude of active twist control inputs taking advantage of a global search algorithm to improve performance and reduce vibration of a helicopter rotor. The active twist schemes include a single harmonic, multiple harmonic, and three other segmented non-harmonic actuation cases. An advanced particle swarm assisted genetic algorithm (PSGA) is employed for the optimizer. In addition, a comprehensive rotorcraft analysis code CAMRAD II is used to reach the trim and to predict the rotor power and hub vibratory loads. A scale-down BO-105 model is used for the reference rotor and the actuator material is assumed to be embedded in the blade structure. The numerical simulation is carried out for low speed descent and high speed forward flight conditions. Among the active twist control inputs, the non-harmonic cases show the best performance gains in reducing the hub vibrations and power consumptions. The hub vibration is reduced by up to 75% while the rotor power is decreased by 2.8% as compared to the baseline uncontrolled rotor at the low speed descending flight condition. The resulting optimized actuation profiles for each of the active twist control cases are found denoted as a function of amplitudes and phases of the rotor response.