Electromagnetic damping of a mechanical harmonic oscillator with the effect of magnetic hysteresis

The paper presents a method of damping of mechanical vibrations by application of electromagnetic actuators. The physical phenomena that take place in such elements are related to magnetic induction and hysteresis. Induction, which consists in generation of electric current in a conductor placed within a variable magnetic field, has a precise quantitative description in form of the Faraday law. At the same time, magnetic hysteresis in ferromagnetic materials reflects the relation between magnetization of a given sample and magnitude of the external magnetic field that had been active during its whole history. Unfortunately, there is no at present a single commonly accepted model of this phenomenon. In this paper, some considerations by Bertotti (1998) are incorporated to this subject. The authors use a bilinear magnetization curve, which depicts the phenomenon of magnetic saturation. Analysis of the derived equations of motion of the coupled electromagneto-mechanical model revealed that the effect of hysteresis on reduction of vibration amplitude is rather of minor impact, however noticeable. At the same time, the electromagnetic damping itself is powerful. To support the conclusions, appropriate time histories, graphs of the logarithmic damping decrement as well as resonant characteristics are given here as in the previous authors' paper.