Vibration isolation unit combining a air spring with a voice coil motor for negative stiffness

A vibration isolation unit for constructing multi-axis systems was developed. The unit consists of a base, an air spring, a middle mass, a voice coil motor (VCM) and an isolation table. The air spring suspends the middle mass on the base. The VCM is used to realize a suspension with negative stiffness (negative spring), which is connected to the air spring through the middle mass and suspends the isolation table. Such serial connection of a positive spring and a negative spring enables the isolation system to have high stiffness against direct disturbance even with soft springs. The validity of this method is confirmed experimentally with the manufactured unit. A two-axis vibration isolation system was constructed with two units. It was demonstrated that the position and attitude of the isolation table was maintained even in the presence of a moving mass on the isolation table.