Mizutani K., Ito K., Ikeura R.

This paper treats a vibration isolation system for an automatic vehicle carrying fragile products in a clean room of semiconductor industries. The vibration isolation has been carried out with a passive device up to now. To improve the performance, the passive system needs to be set up as a lower stiffness. However, the low stiffness of the vibration isolation system is not worse for practical use. With the object of improving the weak point, we propose hybrid type vibration isolation systems composed of a passive system and an active system. The passive system reduces vibrations of high frequency range and an active one reduces those of low frequency range. In this paper, the hybrid system isolates 3-DOF vibrations, that is, bouncing, pitching and rolling vibrations of the vehicle. The control gain of the active device can be tuned optimally in frequency domain. The control theory is applied to design the active system, and the optical control gains to give the effective vibration isolation performance are provided. The controller of the vibration isolation system derives one control force for bouncing vibration and two control moments for pitching and rolling ones in regard to the center of gravity. Usually, an actuator to supply vibration control force is set in each supporting part at the four corners of the loading platform. The allocation of three control outputs to four actuators is not unique because of redundancy, so that the allocation of the control output must be discussed in detail. In conclusions, we could obtain the proper control gain of the active device in hybrid isolation system to reduce vibrations of the vehicle by the control theory, and propose three control gains about the center of gravity derived from the controller were able to allocate to four actuators by the generalized inverse matrix analysis.