Toshihiko Asami

Desktop vibration isolators are often used as a platform for precision measuring instruments. This article discusses the accuracy of performance prediction methods for vibration isolators elastically supported by four air springs. Each air spring possesses a reservoir tank to ensure the natural frequency of the support system remains low and to provide adequate damping force. For practical use, air springs and reservoir tanks should be installed in separate locations and connected by a small-diameter pipe because desktop isolators must be thin. Our previous studies have shown that there is a secondary resonance point in systems supported by air springs with long pipes and reservoir tanks and that it is not simple to theoretically calculate the amplitude and frequency at this point because this type of air spring support system has nonlinear characteristics. In this study, the change in the vibration isolation performance of a desktop vibration isolator with the length of the pipe connecting the main air tank and the reservoir tank of an air spring-supported system was examined experimentally and approximated using theoretical calculations.

The purpose of the present study is to clarify the fluid flow of an oil damper through numerical analysis in order to estimate the exact damping coefficient of an oil damper. The finite difference method was used to solve the governing equation of the fluid flow generated by a moving piston. Time steps based on the fractional step method and the arbitrary Lagrangian-Eulerian (ALE) method were adopted for the moving boundary. In the moving boundary problem, a masking method with a single block grid system was used to stabilize the computation . In other words, algebraic grid generation using a stretching function was used for the moving piston in the cylinder of the oil damper. The time-dependent coordinate system in the physical domain, which coincides with the contour of the moving boundary, is transformed into a stationary rectangular coordinate system in the computational domain. In order to valiade the caluculated results, they were compared with experimental results and the approximate algebraic solution. As a result, it became possible to estimate exactly the degree of contribution of the conversation term the Navier-Stokes equation on the damping coeffcient of the oil damper.