振動勾配制御による振動放射音の低減

抄録

Global vibration reduction is difficult to achieve by local sensing. The difficulty comes from a poor observability of the structural modes, which occurs when the measurement point is near nodes of structural modes. Since modal shapes of the vibration velocity and its spatial gradients are different, the observability can be improved by sensing not only the velocity but also its gradients at a single measurement point. On the other hand, from the viewpoint of reducing the sound radiation rather than the structural vibration, the global vibration reduction does not necessarily lead to the global noise reduction, because radiation efficiencies of the structural modes are considerably different. A method to independently measure and control a cluster of the structural modes with high radiation efficiencies, cluster control, was investigated in earlier works, yet the difficulty in achieving global vibration reduction by local sensing is the same as the conventional vibration control. This study investigates cluster control with the error criterion being the vibration velocity as well as its gradients, and presents the control effects via numerical simulations. It was found that the cluster control including the vibration gradients facilitates the global suppression of vibration and noise.