An Impact Excitation System for Repeatable, High-Bandwidth Modal Testing of Miniature Structures

Abstract

Recent advances in various micro-manufacturing techniques have enabled utilization of miniature devices in numerous applications. However, testing, modeling, and predicting performance of these structures still poses various challenges. Experimental modal analysis techniques have been widely used to obtain the dynamic characteristics of structures; however, having very high natural frequencies, small vibration amplitudes, and high compliance, miniature structures require additional care during modal testing. Although recent developments in sensor technology enabled to obtain accurate high frequency vibration measurements during modal testing of miniature structures, excitation of miniature structures without any damage and within high frequency range in a reproducible manner is still being investigated. This paper presents design, development, and performance evaluation of a custom-made impact excitation system that enables repeatable, high bandwidth, single-hit impacts, and controllable impact force for modal testing of miniature structures. The system is equipped with a miniature force sensor attached to a custom designed flexure and an automated release mechanism driven by an electromagnet. The excitation bandwidth and the impact force exerted to the test structure can be controlled through control parameters: initial displacement given to the flexure and gap between the impact tip and the test surface.