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An electromagnetic forcing device

An electromagnetic forcing mechanism is described which uses feedback to reduce unwanted harmonics in the force

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Abstract

The paper describes the drawbacks of an electromagnetic forcing device, of the type commonly used to study forced vibration of structures, and presents details of a feedback control system designed to overcome them. The work described was initiated when attempting to generate sinusoidal forcing in a nonlinear beam-vibration study. Magnetic-material nonlinearities and spatial inhomogenieties in the magnetic field led to unwanted harmonics in the force the beam experienced, and feedback was used to reduce these effects. A brief description of the principles of feedback control is presented and the problems encountered in applying the concepts to the electromagnetic forcing device are discussed. Details of the system, its problems, operating characteristics and limitations are presented.

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Abbreviations

A :

amplifier (Fig. 8)

B :

magnetic induction, total

B o :

static component of magnetic induction

B 1 :

oscillatory component of magnetic induction

F o :

static component of force on beam

F 1 :

oscillatory component of force on beam

H :

magnetic intensity

P :

potentiometer (Fig. 8)

Ω:

forcing frequency

ω n :

natural frequency of beam

References

  1. Plas, J. andJanssen, L., “A Transistorized Contactless Electromagnetic Exciter,”Int. J. Machine Tool Design Research,12,1–16 (Mar. 1972).

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  2. Hyer, M.W., “Nonlinear Vibration of Three-Layer Beams,”PhD Thesis, University of Michigan, University Microfilm, Ann Arbor, MI (1974).

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  3. Hyer, M.W., Anderson, W.J. andScott, R.A., “Nonlinear Vibrations of Three-Layer Beams with Viscoelastic Cores: I, Theory,”J. Sound and Vibration,46 (1),121–136 (1978).

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Author information

Authors and Affiliations

  1. School of Engineering, Old Dominion University, 23508, Norfolk, VA

    M. W. Hyer

  2. Department of Aerospace Engineering, University of Michigan, 48109, Ann Arbor, MI

    W. J. Anderson

  3. Department of Applied Mechanics, University of Michigan, 48109, Ann Arbor, MI

    R. A. Scott

Authors
  1. M. W. Hyer
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  2. W. J. Anderson
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  3. R. A. Scott
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Additional information

Work funded in part by the National Science Foundtion, Grant No. GK-36374X. It forms part of the PhD thesis of the first author at the University of Michigan in 1974.

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Hyer, M.W., Anderson, W.J. & Scott, R.A. An electromagnetic forcing device. Experimental Mechanics 18, 161–166 (1978). https://doi.org/10.1007/BF02324136

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  • DOI: https://doi.org/10.1007/BF02324136

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