Development of a vibration isolation system using an air suspension with automatic damping adjustment mechanism

In this study, we develop a vibration isolation system using an air suspension with a variable length slit restriction, clarify its dynamic characteristics and build a system that automatically adjusts an equivalent damping coefficient and an equilibrium position of a supported object. The proposed air suspension can provide an optimum damping coefficient by a damping adjustment mechanism. The optimum damping coefficient, which provides the minimum resonance amplitude, increases as mass of the supported object increases. The damping coefficient can be varied by varying slit length of the restriction. In order to vary slit length, the damping adjustment mechanism consists of a fixed plate, which has a partially circular groove and a rotating flat plate faced to the grooved plate. The variable length partially circular slit is formed by the two plates. The damping coefficient is almost proportional to an adjustment angle of the rotating flat plate in the adjustment mechanism. An optimum adjustment angle which provides the minimum resonance amplitude can be obtained by equation showing a relationship between the supported mass and the optimum adjustment angle. The proposed system consists of the air suspension, two pressure sensors measuring atmospheric pressure and static pressure in the cylinder and the reservoir tank, the damping adjustment mechanism, a servo motor rotating the flat plate to tune the adjustment angle and a micro-computer. The micro-computer calculates the optimum adjustment angle which is obtained from the measured pressure data and controls the servo motor to adjust the damping coefficient. The equivalent damping coefficient of the proposed air suspension does not depend on the amplitude even if the slit length is changed by the damping adjustment mechanism. Even if the mass increases up to three times of the nominal value, the minimum resonance amplitude is achieved by using the damping adjustment mechanism.