Identification of loading characteristics on vibration isolator using air suspensions

Abstract

In this study, we propose a method for estimating mass, center of gravity and moment of inertia of loading on vibration isolator using state quantities of air suspensions and clarify the usefulness of the proposed method by experiments. The air suspension is one of fundamental components of the vibration isolator that utilizes a stiffness caused by compressibility of air and damping effect caused by viscosity of air. The vibration characteristics of the vibration isolation system using air suspensions, which has the translational and rotational degree of freedoms, vary according to the characteristics of the loading such as the weight, the position of the center of gravity and the moment of inertia. The weight and the position of the center of gravity can be estimated from static characteristics. But the moment of inertia can only be estimated from the dynamic behavior. Therefore, the natural frequencies of the vibration system are measured and the moment of inertia is estimated using the relational expression between the natural frequencies and the moment of inertia. The loading is supported by a rubber film lifted by the air pressure fed into the air suspensions. In addition, the internal pressure of the air suspensions is measured by the pressure sensor in the tank of the air suspensions. In this experiment, in order to estimate the moment of inertia of the loading supported by the two air suspensions, the loading is freely vibrated and the natural frequencies are measured. In this study, the estimation errors of the weight, the position of the center of gravity, and the moment of inertia are within 10 [%] using the state quantities of the air suspensions and the natural frequency of the rotation mode.