Nihon Kikai Gakkai ronbunshu (Jan 2025)
Estimation of characteristics of supported object on vibration isolator using air suspensions
Abstract
An air suspension is one of the fundamental components of a vibration isolator that utilizes a stiffness caused by compressibility of air and damping effect caused by viscosity of air. In this study, we propose a method for estimating mass, center of gravity and moment of inertia of a supported object on the vibration isolator using state quantities of air suspensions and validate the proposed method by experiments. Previous research has shown that to obtain optimal vibration characteristics in a multi-degree-of-freedom vibration isolator supported by multiple air suspensions, it is necessary to set the damping coefficient of each air suspension according to the moment of inertia around a horizontal axis passing through the center of gravity. Therefore, it is necessary to estimate the characteristics of the supported object to derive and set the optimum damping coefficient, which varies according to them. The mass and the center of gravity can be estimated from static condition of the air suspensions. The moment of inertia can be estimated from the natural frequency of the vibration system. However, the damping coefficient of the vibration isolator is generally large since its vibration isolation characteristics should be optimize. For this reason, it is difficult to measure the natural frequency from the transient response of the supported object on the vibration isolator. Therefore, in this study, targeting a 2-DOF system, which is the simplest structure in which the moment of inertia affects the vibration characteristics, we clarify a method to estimate the moment of inertia using air suspensions, which can reduce the damping coefficient as much as possible only when estimating the characteristics of the supported object, and verify the method through experiments. The experimental results showed that the estimation error of the mass is 4% at maximum and the center of gravity is 3% at maximum. The estimation error of the moment of inertia is 24% at maximum regardless of the center of gravity of the supported object.
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