Attitude control of pneumatic active anti-vibration apparatuses with two degrees-of-freedom in shutdown process

For the ultra-precision machining, semiconductor exposure machines employ the pneumatic active anti-vibration apparatuses (AVAs), which have air springs. In industrial scenes, when the vibration due to earthquake is observed, the AVA is automatically stopped by exhausting air. However, the difference of time delays in the response of the air springs causes the undesirable rotational motion of an isolated table. This paper considers the attitude control of the AVA including different time delays during shutdown process. To avoid the rotation of the isolated table, reference trajectory is shaped. It is verified that the range of the rotational angle in the shutdown of the AVA can be reduced by using the proposed method.