An impedance approach to passive-active vibration control

Licentiate thesis, 2008

The complementary advantages of active and passive vibration control have motivated research concerning hybrid configurations. Previous studies have mainly focused on active constrained layers (ACL). However, investigations pointing towards suboptimal performance of ACL have made it interesting to investigate other solutions. This thesis presents a theoretical approach to hybrid passive-active vibration control. The fundamental principle of the configuration investigated in this thesis is to use active control to force all wave power into a passive constrained layer (PCL). The approach is based on matching the impedance jump at the junction of an untreated beam and a beam treated with PCL. The theoretical results show that the active impedance load absorbs the major part of the incident wave power off-resonance, while it injects power at resonances. The incident wave power in addition to the power injected by the active impedance load is, at resonances, absorbed in the PCL.