University of Hertfordshire

Documents

  • Diogo Montalvao
  • Thomas Baker
  • Balazs Ihracska
  • Muhammad Aulaqi
View graph of relations
Original languageEnglish
Number of pages16
Pages (from-to)506-521
JournalMechanical Systems and Signal Processing
Journal publication date15 Jan 2017
Volume83
Early online date6 Jul 2016
DOIs
Publication statusPublished - 15 Jan 2017

Abstract

Many applications in Experimental Modal Analysis (EMA) require that the sensors’ masses are known. This is because the added mass from sensors will affect the structural mode shapes, and in particular its natural frequencies. EMA requires the measurement of the exciting forces at given coordinates, which is often made using piezoelectric force transducers. In such a case, the live mass of the force transducer, i.e. the mass as ‘seen’ by the structure in perpendicular directions must be measured somehow, so that compensation methods like mass cancelation can be performed. This however presents a problem on how to obtain an accurate measurement for the live mass. If the system is perfectly calibrated, then a reasonably accurate estimate can be made using a straightforward method available in most classical textbooks based on Newton’s second law. However, this is often not the case (for example when the transducer’s sensitivity changed over time, when it is unknown or when the connection influences the transmission of the force). In a self-calibrating iterative method, both the live mass and calibration factor are determined, but this paper shows that the problem may be ill-conditioned, producing misleading results if certain conditions are not met. Therefore, a more robust method is presented and discussed in this paper, reducing the ill-conditioning problems and the need to know the calibration factors beforehand. The three methods will be compared and discussed through numerical and experimental examples, showing that classical EMA still is a field of research that deserves the attention from scientists and engineers.

Notes

© 2016 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

ID: 9320532