Optimum active twist input scenario for performance improvement and vibration reduction of a helicopter rotor

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 different 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 while assuming the actuator material embedded in the blade structure. 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 87% while the rotor power required is decreased by 3.3% as compared to the baseline uncontrolled rotor in low speed descending flight condition when using the non-harmonic active twist schedules. The resulting optimized actuation profiles are found for each of the active twist control cases and the physical mechanism leading to less vibration and power consumption is discussed. The Pareto optimum is also examined to illustrate the simultaneous reduction in the power required and the hub vibration of the rotor.