A study of distributed piezoelectric actuators for structural vibration control
Interest in the use of smart-structure technology for noise and vibration reduction in helicopter applications has been on the rise in recent years. It has been established that significant gains in helicopter performance can be achieved through active rotor blade vibration control. This thesis presents a study of selective structural mode actuation of simple structures by means of surface-bonded piezoelectric actuator patches. The central objective of the study is to establish the potential for the use of piezoelectric actuators in active rotor blade vibration control applications. Theoretical and finite element vibration analyses were carried out, first for a thin flat plate and then for a long, straight, isotropic cantilever box beam. Finally a finite element vibration analysis was carried out for a three-cell hollow helicopter rotor blade structure. In each case, harmonic excitation of the structure by surface-bonded piezoelectric actuator patches is investigated, with the actuator patches in single and multiple configurations. The theoretical models are based on classical elasto-mechanics theory, and include the effect of bonding layer thickness. The finite element analyses were carried out with ANSYS 5.5. All analyses assume the use of readily available PZT4 ceramic piezoelectric actuator patches. The results lead to identification of optimal actuator patch configurations for selective mode excitation of the plate, box beam and helicopter rotor blade structures. Furthermore, the results for the box beam and rotor blade structures indicate that significant attenuation of the first two flapping modes and first two lagging modes can be achieved with practical levels of actuator excitation voltage. However, the results for selective excitation of the twist modes of the structures are inconclusive.