Non-collocated control of vibration of a three-DOF structure using the electromagnetic vibration absorber

Abstract

Vibration control is very important in many areas including machine operation and daily life. Semi-active vibration control integrates a tuning control scheme with a tunable vibration absorber for suppression of vibration due to a harmonic excitation with a variable excitation frequency. The electromagnetic vibration absorber (EMVA) is a semi-active vibration device whose stiffness can be tuned on-line. In this study, the EM VA is used for non-collocated vibration control. The study consists of two parts. In the first part, the characterization of the EMVA is revisited using a commercial FE package, Comsol Multiphysics. Various single physics models are built including the electromagnetic coil, the electromagnetic coil with a core, and a permanent magnet (PM) placed between a pair of PMs. These models are used to study the magnetic density in the gap of the electromagnet. A coupling model that involves magnetism and structural mechanics is built. This model is used to study the factors that affect the magnetic stiffness. In the second part, the EMVA is implemented to suppress vibration of a structure that can be modeled as a three-degree-of-freedom system. The non-collocated control theory is reviewed. The EM VA is modified to allow both manual adjustment and on-line tuning. Three different control methods, FFT-based method, FFT-based plus fine tuning method, and RM S-based method, are developed. The experimental results using the three methods are compared.