Development of linear motor-driven amplifying device for reproducing long period vibration

Abstract

This paper discusses method for reproducing vibrational waves with large amplitude of displacement which exceeds allowable stroke of shaking table. Excitation system which has amplifying device, driven by linear motor, on shaking table is proposed for reproducing such waves. To reproduce vibrational waves as the absolute displacement of amplifying device, which is equal to the sum of the absolute displacement of shaking table and the relative displacement of amplifying device, a cooperating excitation method is are considered. In this method, the amplitude of target wave is distributed for shaking table and amplifying device. A vibration test is conducted and it is verified that the proposed excitation system can reproduce random wave which has maximum amplitude of ±600 mm precisely. Furthermore, this paper discusses the reducing method of the negative influence of reaction force, caused by elastic vibration of test object, on target value following characteristics of amplifying device. Two-degree-of-freedom control system which has feedback controller and feedforward controller is designed for improving the characteristics of the amplifying device. To verify the applicability of the two controllers, a vibration test is conducted, and it is clarified that the variation of the target value following characteristics, due to reaction force caused by test object, can be reduced by using the two-degree-of-freedom control system.