George Juraj Stein

An Application of Electromagnetic Induction in Vibration Control

Excessive vibration of machines and/or structures can be controlled passively (e.g. introducing resilient elements) and/or actively (e.g. using elements capable to adjust their properties for actual state of the vibration). An electromagnet, as a vibration control element, can be implemented in active (or semi-active) control strategy. This approach is analyzed in the present paper. The electromagnetic induction occurs in a magnetic circuit exposed to variable magnetic flux, which can be obtained e.g. by changing reluctance (magnetic resistance) of the system due to a variable air gap, as the result of armature vibration. The lumped parameter mathematical model of the coupled electro-magneto-mechanical system is formulated. The performance of the model is analyzed, assuming harmonic forced vibration. By the induction, mechanical energy of vibration is converted into electrical one and dissipated in the shunt resistance. Two concepts are investigated further – electromagnet behaves as (a) a spring element (reduction of equivalent system stiffness); (b) a damping element.

Ferromagnetic eddy current damper of beam transversal vibrations

The paper deals with attenuation of transversal vibrations of a clamped-clamped beam loaded by a rigid mass at beam mid-point and excited by vertical force acting at beam mid-point. The novelty of treated approach is the use of a ferromagnetic conductor as the principal damping device. This is a different approach from that one used in contemporary research papers. Beyond vibration attenuation a concurrent shift in damped natural frequency due to the negative stiffness is observable. The theoretical results are complemented by measurements on a test stand. Up to 10 dB attenuation of the most marked resonance peak and frequency shift by up to 5 % to lower frequency was observed.

Preliminary Investigations of Machine Frame Vibration Damping Using Eddy Current Principle

A novel approach to vibration attenuation, based on the eddy current principle, is described. The combined effects of all magnetic forces acting in the oscillatory system attenuate frame vibrations and, concurrently, decrease the damped natural frequency. A mathematical model of the forces balance in the oscillatory system was derived before. Some experimental results from a mock-up machine frame excited by an asynchronous motor are presented.

Preliminary investigations of a vibration attenuator based on eddy current principle

An electro-magnetic damping device, using the eddy current principle, is analyzed in a simplified, linearised form. Simulation results indicate resonance peak attenuation and shift to lower frequency in respect to a sole mechanical oscillatory system. The novelty of the described approach consists in using a ferromagnetic conductor instead of a diamagnetic one.

Mathematical Modelling and Parameter Identification of an Electro-Magneto-Mechanical Actuator for Vibration Control

An electro-magneto-mechanical system, composed of the electromagnet, having an iron core with a coil and a movable yoke, is analyzed in the paper. Exposing the yoke to mechanical motion, the variation of the magnetic flux due to change of the air gap height induces alternating voltage at the coil terminals. If the electrical circuit is closed, the so generated electrical power is dissipated via the internal coil losses, treated in this paper. Thanks to the interaction between the electrical and mechanical system (i.e. via magnetic force), the power dissipation in electrical circuit influences the dynamical response of the mechanical system. And so the mechanical vibrations can be controlled by these means.The mathematical model of the simplified dynamical system, which describes behavior of the experimental set-up, is derived using a lumped parameter approach.The aim of the article is to identify parameters of the derived mathematical model, focused mainly on electrical circuit. Based on measured experimental data, the static constants as well as dynamic losses were analyzed.Copyright