著者
林 裕介 渡辺 昌宏 原 謙介
出版者
一般社団法人 日本機械学会
雑誌
Dynamics & Design Conference 2010 (ISSN:24242993)
巻号頁・発行日
pp._260-1_-_260-6_, 2010-09-14 (Released:2017-06-19)

This paper deals with theoretical stability analysis of an active feedback control of web flutter which occurs to the web with both ends fixed and tensioned. In this paper, a non-contact active feedback control method of web flutter by using movable plates set at inlet or outlet of the passage are developed and its analytical model is constructed. The equations of motion of the flexible sheet coupled with the fluid flow controlled by the movable plates are obtained. The characteristic equation of the system is derived as a function of the flow velocity in the narrow gap. As a result, it is shown that the web flutter occurs to the web with increasing the flow velocity, and is effectively suppressed by the proposed non-contact flow control devices and active feedback control method. Furthermore, calculation results are verified by the experiments.
著者
齋藤 彰 久能 友宏
出版者
一般社団法人 日本機械学会
雑誌
Dynamics & Design Conference 2019 (ISSN:24242993)
巻号頁・発行日
pp.351, 2019 (Released:2020-02-25)

In this paper, applicability of Dynamic Mode Decomposition (DMD) to the extraction of modal properties of linear mechanical systems from their time-domain dynamic responses, i.e., experimental modal analysis is discussed. Of particular interest is its capability to extract modal parameters, i.e., natural frequencies, damping ratios and mode shapes, from measured time histories of displacement of discrete and distributed mechanical systems. First, theoretical background of DMD is briefly reviewed from the viewpoint of structural dynamics. It is shown that the modal parameters can be extracted from the DMD eigenvalues and the associated eigenvectors. The DMD is then applied to analytical solutions of transient response of discrete mass-spring-damper mechanical systems to discuss the applicability of the DMD to extract the modal parameters from the transient response. Furthermore, the effects of measurement errors on the identified modal parameters are discussed. With relatively large measurement errors, it is shown that DMD produces erroneous results especially for the damping ratios. Finally, DMD is applied to experimentally-obtained impulse response of displacement field of a cantilevered beam with many measurement points, and its modal parameters are extracted. It is shown that the modal parameters extracted by DMD are as accurate as the ones obtained by the existing modal parameter extraction method.
著者
小池 関也 見邨 康平
出版者
一般社団法人 日本機械学会
雑誌
Dynamics & Design Conference 2016 (ISSN:24242993)
巻号頁・発行日
pp.506, 2016 (Released:2017-06-19)

Previous studies, which calculate dynamic contributions of the whole-body joint torques to the generation of bat head speed by using the equation of motion for whole-body with bat system, showed that the motion-dependent term is the largest contributor to the generation of the bat head speed at the ball impact, and also showed that joint torques of the upper limb joints and the torso joint are the main contributors to the head speed with consideration of the generating factors of the motion-dependent term. These results do not tell us the roles of the lower limb joints in the bat head speed generating mechanism. So in order to quantify the roles of the lower limb joints in the mechanism, we quantify the dynamic contributions of the whole-body joint torques to the generation of forward/backward rotational motion of the lower trunk segment during baseball batting motion. Five collegiate baseball players participated in this experiment. They performed hitting a teed ball as strong as possible. Kinetic data of each hand and each foot were obtained by using an instrumented bat equipped with 28 strain gauges and 3 force platforms, respectively. From the results, the flexion/extension torque of both hip joints showed the largest contribution to the forward angular velocity of the lower trunk segment against the large negative contribution due to the torso joint torque. This result indicates that these hip joint torques play an important role to exert large rotational torque at the torso joint, and these hip joint torques show indirect contributions to the bat head speed.
著者
相原 洋人 田中 信雄
出版者
一般社団法人 日本機械学会
雑誌
Dynamics & Design Conference 2007 (ISSN:24242993)
巻号頁・発行日
pp._340-1_-_340-6_, 2007-09-25 (Released:2017-06-19)

There have been a number of reports on active noise control (ANC). However, conventional ANC using a voice coil loudspeaker promises attenuation only at targeted local points. Then ANC using a parametric array loudspeaker as a control source is discussed. A parametric array loudspeaker exploits nonlinear interactions of finite amplitude ultrasounds in the air. Characteristics of a parametric array loudspeaker have already been reported by a number of researchers. However, there are few investigations of simulation or experimental result of ANC using a parametric array loudspeaker. This paper addresses control effect of feed forward ANC using a parametric speaker as a control source. The control effect is more than 20dB by ANC using a parametric array loudspeaker as a control source at 1000Hz. Distribution maps of sound pressure of ANC using a conventional speaker and a parametric speaker as a control source are shown by numerical analyses and experiments.