No abstract

No abstract

In recent years, there has been an increasing demand for micro-vibration free space from industrial and scientific organizations. In response to this demand, several active micro-vibration control systems utilizing various types of actuators have been developed and applied in various environments and to a number of machines. The authors have developed an active micro-vibration control system with six degrees of freedom using giant magnetostrictive (GMS) actuators and actually have applied it to an FIB (focused ion beam).In general, a GMS actuator has a quicker response time and bigger displacement characteristics at higher frequencies than an air actuator. Therefore, we have developed a hybrid actuator that consists of a GMS actuator and an air actuator. Its main feature is that the two actuators are arranged in parallel. Ideally, such a hybrid actuator would have the merits of both component systems. Through experimental tests on the hybrid actuator and simulation analysis on the uni-axial micro-vibration control device using the hybrid actuator, we have shown that this is the case.Following this successful result, we have developed an active 6-DOF micro-vibration control system using hybrid actuators. This paper presents an outline of the active 6-DOF micro-vibration control system, the hybrid actuator used, and the design strategy of the control system. Results of control experiments under various disturbances are described. Through these results, it is verified that an active 6-DOF micro-vibration control system using hybrid actuators controls vibration more effectively than use of air actuators alone. This good performance is realized by the efficiency of the hybrid actuator, which is attributed to the collaboration of the air actuator and GMS actuators.

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.

No abstract