Cellular automata model for size segregation of particles

金沢大学理工研究域機械工学系This paper deals with the study of size segregation of particles where the size difference causes characteristic movement of particles inside granular media according to the induced vibration. In this study, segregation of particles due to the difference in size is simulated using Cellular Automata. A connected lattice automaton is introduced in the model, so that the variation of particle sizes as well as geometrical arrangement between particles can be represented. The Cellular Automata model can produce various characteristics which are observed in the actual granular systems. Furthermore, it is known from both numerical and experimental observations that the segregation progress is dependent on the amplitude of excitation as well as the particle size ratio. © 2010 Springer-Verlag

Study on acoustic field with fractal boundary using cellular automata

金沢大学理工研究域機械工学系In the present study, characteristics of the acoustic field in an enclosure bounded by fractal walls are investigated using Cellular Automata (CA). CA is a discrete system which consists of finite state variables arranged on uniform grid. The dynamics of CA is expressed by temporary updating the states of cells according to the local interaction rules, defined among a cell and its neighbors. In this paper, the effect of fractal shaped boundary structure to the reverberation and sound absorption characteristics of an enclosure is investigated for two dimensional acoustic wave propagation model described by CA. Local rules are provided for the construction of fractal patterns as well as representation of wave propagation phenomena. It is known by the numerical simulations that the damping enhancement and also frequency-selective absorbing behavior is seen for specific fractal patterns and stage numbers. © 2008 Springer-Verlag Berlin Heidelberg

A combined approach for modeling particle behavior in granular impact damper using discrete element method and cellular automata

A particle impact damper is a vibration absorber type that consists of a container attached to a primary vibrating structure. It also contains many particles that are constrained to move inside the container, whereby the damping effect can be obtained by collision between particles and the container. The discrete element method (DEM) has been developed for modeling granular systems, where the kinematics of each particle are calculated numerically using the equations of motion. However, the computational time is significant since the algorithm checks for particle contacts for all possible particle combinations. The use of a cellular automata (CA) modeling technique may provide increased computational efficiency due to the local updating of variables, and the discrete treatment of time and space. In this study, we propose a new approach combining DEM with CA for modeling a granular damper under a forced excitation. We use DEM to describe the particle motion according to the equations of motion, while CA is introduced for the particle contact checks in discrete space. We also investigate the effect of simplification in the contact force model, which allows the unit time step of numerical integration to become larger than that used in the strict model. It is shown that the suggested particle contact scanning method and the force approximation model contribute to the reduction of the computational time, and neither degenerates the calculation accuracy nor causes the numerical instability. © 2016 Springer Science+Business Media DordrechtEmbargo Period 12 month

Modeling of sound absorption by porous materials using cellular automata

金沢大学大学院自然科学研究科知的システム創成金沢大学工学部In the present study, acoustic wave propagation in acoustic tube in-corporating sound absorbing material is simulated using Cellular Automata (CA). CA is a discrete system which consists of finite state variables, arranged on a uniform grid (cell). CA dynamics is described by a local interaction rule, which is used for computation of new state of each cell from the present state at every time step. In this study an acoustic tube model is introduced in which ab-sorbing material is characterized by direct modeling of porosity and flow resis-tance. Direct numerical simulation CA model is performed and evaluated by absorption coefficient using standing wave ratio measure. The results showed good correspondence with analytical solutions. © Springer-Verlag Berlin Heidelberg 2006

パラメトリック励振型動吸振器を使用した多自由度系の制振手法に関する研究

本研究は多自由度系の制振を容易に行うためのパッシブ制振器の開発を目的にしている。具体的には、パラメトリック励振型動吸振器またはオートパラメトリック吸振器ともいわれる振子式動吸振器を利用する。この種の動吸振器は、その固有振動数が主系の固有振動数の1/2になるように調整することにより、主系の共振付近の振動に対して制振効果を発揮する。このとき主系の共振付近でのみ振子が発振し、それ以外の振動数では振子は振動せず、静止状態にある。したがって、1次共振、2次、3次、・・・などのように特定の共振用に調整された動吸振器によってそれに対応する共振のみを制振することが可能であり、かつ他の次数の共振には影響を与えないので、他の動吸振器の動作を妨害しない。この種の動吸振器の適用範囲を拡大するため、支点回りに回転ばねを持つ振子式動吸振器を開発している。重力を利用した振子では振動方向及び振子寸法の制限があり、適用範囲が限られることが多い。支点回りに回転ばねを持つ振子について、支点が振動変位する場合のパラメトリック共振を調べ、パラメトリック励振型動吸振器として利用可能であることを示している。つぎに3自由度系を製作してその1次共振と2次共振を対象に制振を試みている。1次共振振動数の半分の固有振動数を持つ振子系を1次共振用の動吸振器、2次共振振動数の半分の固有振動数を持つ振子系を2次共振用の動吸振器として設置し、その動作特性と制振効果を確かめる実験を行っている。結果として、各共振状態においてはそれに対応する動吸振器のみが動作し、系の振幅も減少することが確認されて多自由度系の制振が容易に行えることを明らかにしている。A purpose of this study is to develop a passive absorber which makes it possible to suppress vibration of multi-degree-of-freedom systems using pendulum type dynamic absorbers which is called a parametric excitation dynamic absorber or an autoparametric vibration absorber. Such a dynamic absorber generates vibration suppression near resonance frequency of the main system when a natural frequency of the dynamic absorber is adjusted to half of natural frequency of the main system. A pendulum of the dynamic absorber vibrates only around resonance frequency of the main system and does not vibrate except the resonance frequency. The adjusted dynamic absorber to 1st resonance, 2nd resonance, etc can suppress amplitude of the corresponding resonance and does not disturb the dynamic absorbers for other resonances because it vibrates around only resonance. A pendulum type dynamic absorber which includes a rotational spring and damper has been developed in order to expand a sphere of the applica tion. Pendulums vibrated by the gravity have restriction for a sphere of the application because of having limitation of vibrating direction and the pendulum size. Parametric resonance of the pendulum with a rotational spring and damper is investigated when a support point of the pendulum is vibratory, and it is shown that its pendulum can be used for the parametric excitation dynamic absorber.Then 1st and 2nd resonances of three-degree-of-freedom main system have been experimentally controlled by the dynamic absorber. The dynamic absorber with natural frequency equal to half of the 1st natural frequency of the main system reduces a peak of 1st resonance of the main system and the dynamic absorber with the frequency equal to half of the 2nd natural frequency also reduces a peak of 2nd resonance in the experiment. The suppression effect and the pendulum behavior are discussed. It is concluded that each dynamic damper becomes active only near the corresponding resonance and the main system vibration becomes small. Therefore the proposed parametric excitation dynamic absorbers can suppress vibration of multi-degree-of-freedom system.研究課題/領域番号:17560203, 研究期間(年度):2005-2006出典：「パラメトリック励振型動吸振器を使用した多自由度系の制振手法に関する研究」研究成果報告書　課題番号17560203（KAKEN：科学研究費助成事業データベース（国立情報学研究所））（https://kaken.nii.ac.jp/report/KAKENHI-PROJECT-17560203/175602032006kenkyu_seika_hokoku_gaiyo/)を加工して作

Modelling of incident sound wave propagation around sound barriers using cellular automata

In the present study, acoustic wave propagation in the field including sound isolation panel is simulated using Cellular Automata (CA). CA is a discrete system which consists of finite state variables, arranged on a uniform grid. CA dynamics is described by a local interaction rule which is used for computation of new state of each cell from the present state at every time step. In this study a sound field is modeled using CA where the sound isolation panel exists and the numerical simulation results are evaluated quantitatively by the insertion loss. The results showed good correspondence with analytical solutions. © 2012 Springer-Verlag Berlin Heidelberg

Experimental Investigation of an Adaptively Tuned Dynamic Absorber Incorporating Magnetorheological Elastomer with Self-Sensing Property

The magnetorheological elastomer (MRE) is known to belong to a class of smart materials whose elastic properties can be varied by an externally applied magnetic field. In addition to the property of the field-dependent stiffness change of the MRE, the electrical resistance of the composite is also changed by the induced strain, thereby providing a new self-sensing feature. In the present study, a novel, dynamic vibration absorber is developed using an MRE with a self-sensing function and adaptability. The natural frequency of the absorber is instantaneously tuned to a dominant frequency extracted from the strain signal of MRE. The damping performance test shows that the vibration of a system with one degree-of-freedom that is exposed to a nonstationary disturbance can be adequately reduced by the proposed frequency-tunable dynamic absorber without the use of external sensors. © 2016 Society for Experimental MechanicsIn Press / Embargo Period 12 month

Modeling of granular damper using cellular automata

金沢大学工学

Vibration coutrol using neural network with adaptively rearranging structure

金沢大学工学

Vibration of Induction Motor Rotor in Rotary Magnetic Field (Case of Two Poles Motor)

Vibration of a rotor in rotary magnetic field of a two poles induction motor has been investigated. The vibration is measured at any relative position of the stator and the rotor in various power supply frequencies in the experiment and is analyzed in consideration of structural factors of the rotor. The following conclusion is obtained through the experiment and the analysis, (1) 2ω vibration of two times of the power supply frequency ωoccurs because of offset between the stator center and a gyration center of the rotor. (2) Two vibrations of ω(1— s) and ω(l + i·) where s is slip ratio occur because of unbalance of the rotor or disagreement between the gyration center and the geometrical center of the rotor. (3) An unstable vibration is predicted in the analysis when the power supply frequency equals to a natural frequency of the rotor. But the unstable vibration did not occur in the experiment because of the damping. © 1999, The Japan Society of Mechanical Engineers. All rights reserved