Akiyoshi Tamura

Analysis of dynamic characteristics for cylindrical journal bearing based on average flow theory.

As a preliminary study on elastic cylindrical journal bearing, this paper presents an analytical method and the calculated results of the static and dynamic characteristics of a rigid cylindrical journal bearing, based on an average flow model theory. By using a modified law of the equivalent lubricant density and viscosity in the negative pressure region, reasonable static pressure distributions with small negative pressure or zero pressure can be obtained. Dynamic pressure distributions, produced by journal velocity, are consistent with those in infinitely long journal bearing theory, proposed by the author in the previous paper. Elastic and damping coefficients are qualitatively equal to the prevailing numerical results. It is also found that the unstable threshold speed and whirl frequency of a rigid rotor and bearing system are in good agreement with those in infinitely long journal bearing theory, described above.

The high speed positioning control of a flexible system.

One of the most effective ways to realize a high speed positioning control is to lighten the weight of the mechanical parts of the system. But in such a system, flexibility must be taken into consideration in the control theory, otherwise it results in positioning error and remaining vibration. Positioning control depends on an access mode and a positioning mode ; and to realize a high speed positioning control, fast access is required at first. In the access mode, only the positioning of the load close to the object point is required. So in the access mode, it seems to be possible to control a flexible system with an open loop circuit, so long as there exists little disturbance. From this point of view, the access mode of high speed positioning control of a flexible system with minimum input energy is discussed in this paper.

Nonstationary Vibration of a System with Backlash Passing through a Resonance

When a system with backlash is subjected to an exciting force, of which the frequency linearly increases or decreases with time and passes through a resonance, nonstationary responses of the system are numerically analyzed and formulas for estimating the maximum amplitudes of the responses are proposed. The evaluation errors are below 25% over the range considered here comparing to the numerically integrated results. The above formulas are derived from a comparison of the two maximum amplitudes, one of which is obtained from a response curve calculated by integrating the equations of motion of the backlash system and the other from the estimation equations of the maximum amplitude for a linear systems passing through a resonance.

Vibration of a system with backlash passing through a resonance.

本研究は,単純ながたを有する一自由度系に,一定振幅,一定角加速度をもつ起振力を作用する場合の共振点通過時の振動特性を数値解析し,その最大振幅推定法を明らかにしたもので,起振力の振幅とがたの比,および角加速度の正負により,がた系の共振点通過時の最大振幅は,みかけの起振力の振幅,みかけの角加速度,および線形一自由度系の場合の最大振幅推定式などを用いて評価できることを示している.

Vibration of rigid rotors supported by anisotropic springs.

弾性支持されたたて形ロータでは,上下の軸受支持の弾性主軸方向が一致しない場合がある.本報では上下の軸受の弾性主軸方向に任意の角度差αが存在するときの剛性ロータの自由振動について解析と実験を行い,αによる危険速度の変化およびロータのふれまわり軌跡の特徴を明らかにした.危険速度がαの影響を受けない場合の条件を提示し,その理由を軸受部でのふれまわり運動に関する力関係から説明した.