Nobuo Tanaka

Acoustic cluster control of noise radiated from a planar structure

Acoustic cluster control is proposed for the purpose of achieving global sound attenuation of a planar structure. First, acoustic cluster filtering using a point sensor array is presented, which enables the grouping of sound radiated from a target object into a set of clusters, such that each cluster possesses the same common characteristics. This allows the possibility of extracting the cluster of interest without causing observation spillover. Based on the principle of reciprocity, cluster actuation using a point source array is then presented. Driving the source array in accordance with a proposed control law, the excitation of the designated cluster is performed without causing control spillover. Moreover, by combining both acoustic cluster filtering and acoustic cluster actuation, acoustic cluster control may be performed. In implementing acoustic cluster control, the necessary and sufficient condition for the acoustic cluster control is illustrated. It is also shown that the sound radiated from a planar structure may be captured in appropriate acoustic cluster filtering so that acoustic cluster control may be implemented. Experiment was conducted demonstrating the capability as well as the validity of the acoustic cluster filtering, actuation, and control for suppressing the noise radiated from a rectangular panel.

A Study of the Dynamic Damper with a Preview Action : Experiment of the Dynamic Damper with a Preview Action

This paper deals with a realization of a dynamic damper with a preview action already proposed by the authors. It is also the purpose of this paper to verify the control effect of the dynamic damper for the suppression of a transient vibration resulting from an impact force. First, this paper shows a mechanism of a newly designed dynamic damper with a preview action. Then, based upon three kinds of preview actions proposed in the previous papers, and impact experiment is carried out, verifying the effectiveness of these preview methods. Furthermore, an influence of the maximum impact force upon the control effect for the suppression of the first wave of the transient vibration is investigated. In addition, by varying preview conditions such as a preview time and an initial displacement of a damper mass, the control effect in terms of the preview action is considered.

A Study on the Vibrationless Forging Hammer : 2nd Report, Optimum Design of Feedforward Element

From the viewpoint of feedforward control, this paper deals with an optimum design of a vibrationless forging hammer system presented in the previous paper. First, a chart to estimate the control effect in terms of a feedforward control is shown. Then, with the aid of the chart, a design procedure of the vibrationless forging hammer system is demonstrated. In order to design the control system quantitatively, a performance index to show the suppression effect of a transmitted impulsive force is proposed. Based upon the index, a nonlinear programming is applied to fine optimum parameters of the system. Furthermore, taking into consideration a realizability of the feedforward element, the vibrationless system is designed. Finally, by using a signal wave of an impulsive force obtained in the actual impact process, a simulation experiment is carried out, and the capability of the vibrationless hammer system is verified.