Development of active six-degrees-of-freedom microvibration control system using giant magnetostrictive actuators

Abstract

An active six degrees-of-freedom microvibration control system using giant magnetostrictive actuators is developed in order to realize a microvibration-free space for precision instruments which hate vibration. A giant magnetostrictive actuator is suitable as a displacement actuator for active microvibration control, because it is both compact and durable and also its response against input is fast and reliable. The developed device consists of a table, six air springs, eight magnetostrictive actuators and six accelerometers on the table. Four actuators are set in the horizontal directions, and another four in the vertical direction. Since air springs and actuators as a unit of vertical support system are arranged in parallel, readjustment of the system is quite easy, even when the operating load on the table is changed. The dimensions of the table are 2000 mm length, 1400 mm width, 230 mm height and a weight of about 2 tons. The operating load on the table is 2 tons. A giant magnetostrictive rod is 6 mm in diameter and 50 mm long. The actuators operate within the stroke range of ±25 µm. A feedback control strategy using only six components of table acceleration on the table is adopted and the controller is designed by a model matching method. The obtained control performance of the system through two vibration control tests can be summarized as follows (1) Root-mean-square values of the table accelerations under micro-tremor are reduced to one-third to one-tenth of the floor accelerations, and kept less than 0.008 cm s-2. (2) Induced vibrations by impacts acting on the table disappear in less than 0.05 s.