Carleton University's Rotorcraft Research Group is working on the development of an active rotor control system that incorporates a mechanism for helicopter blade pitch dynamic stiffness modulation at the root, the Active Pitch Link. This system overcomes stroke limitations of smart material and attains superior performance for helicopter rotor-induced vibration reduction. The system was tested at the whirl tower facility and this article reports the achievements obtained with a dynamically similar hinged rotor blade model. Up to 100% reduction in the transmitted loads occurred at the target 2/rev frequency when the blade was excited by a transversal jet to mimic the asymmetric flow of the helicopter rotor in forward flight. An open-loop control algorithm optimized to a target higher-harmonic frequency of the rotor also minimized the impact on the rotor fundamental cyclic control frequency at 1/rev. In another experiment at University of São Paulo, semi-passive control techniques using shunted piezoelectric materials were investigated for the aeroelastic control of fixed wings. Flutter oscillations of a typical section were controlled out over a range of airflow speeds. Finally, the similarity between both control techniques is discussed and recognized that they are based on a dynamic stiffness modulation control principle.

The use of smart materials in vibration control problems, including aeroelastic response, has been investigated in several researches over the last years. Although different smart materials are available, the piezoelectric one has received great attention due to ease of use as sensors, actuators, or both. The main control techniques using piezoelectric materials are the active and passive ones. In the case of aeroelastic control, passive piezoelectric networks have a weak capability of improving the flutter stability margin. Although active systems can achieve good vibration control performance, the amount of external power and added hardware are important issues for active aeroelastic control. In this article, the self-powered semi-passive piezoelectric control of a wind tunnel model aeroelastic response is presented as an alternative to active and passive systems. Linear and nonlinear aeroelastic cases are examined using a test apparatus that allows for experiments of pitch and plunge degrees of freedom of a typical section. Piezoelectric coupling is introduced onto the plunge degree of freedom, and two different semi-passive control schemes are employed: the synchronized switch damping on short circuit and the synchronized switch damping on inductor. An autonomous and self-powered switching circuit is employed, providing a useful self-powered method of aeroelastic control.

Aos meus amigos da Pós-Graduação, com quem dividi os momentos bons e ruins durante a caminhada.Aos meus amigos de laboratório em especial ao Marcel, Tarcísio e Vagner que sempre estavam dispostos a ajudar e discutir sobre os trabalhos, os processos e a vida. Agradeço a minhas irmãs, que mesmo a distância sempre me fizeram sentir estar perto.E um agradecimento especial à meus pais, que sempre me incentivaram e me inspiraram, permanecendo incondicionalmente ao meu lado.

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