Characterization of Rotating Structures in Coast-down by means of Continuous Tracking Laser Doppler Vibrometer

  • M. Martarelli
  • C. Santolini
  • P. Castellini
Conference paper
Part of the Conference Proceedings of the Society for Experimental Mechanics Series book series (CPSEMS)


In rotating machinery variations of modal parameters with rotation speed may be extremely important in particular if very light and undamped structures are taken into account, like helicopters rotors or wind turbines. The relation between natural frequencies and rotation speed is expressed in the form of Campbell diagrams. However it could be required to know also the deviation of operational or mode shapes. In several cases it is not possible to fully control the rotating speed of the machine and only coast-down tests can be performed. Such kind of tests is often fast due to the reduced inertia of rotors: for this reason, an experimental technique able to determine Operational Deflection Shapes (ODSs) in short time and with sufficient accuracy, appears very promising. Moreover coast-down processes are very difficult to be controlled, they causing unsteady vibrations. The need to obtain ODSs from coast-down experiments requires the measurement over a large number of points and therefore a very efficient approach for the rotation control and synchronous acquisition must be developed. In this paper a continuous scanning system operating on rotating structures has been developed, that allows to measure ODS and natural frequencies excited in rotating conditions at different rotation speed during a coast down. This techniques has been tested on a laboratory test bench and compared with traditional Experimental Modal Analysis (EMA) results obtained in non-rotating conditions and with data from Tracking Laser Doppler Vibrometry (TLDV) operating in coast down and at consecutive constant rotation speeds (i.e. each measurement was performed in steady conditions). EMA and TLDV have been performed over a grid of points in order to have ODSs with adequate spatial resolution, it requiring long measurement time. However these data has been used as reference to validate the continuous scanning approach.


Wind Turbine Mode Shape Vibration Measurement Tracking Laser Helicopter Rotor 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Ewins D. J., (2000). Modal testing. Research studies press LTD.Google Scholar
  2. 2.
    Genta G., (2004). Dynamics of Rotating Systems. Mechanical Engineering SeriesGoogle Scholar
  3. 3.
    Campbell W., (1924). Protection of Steam Turbine Disk Wheels from Axial Vibration. Transactions of the ASME: 31–160.Google Scholar
  4. 4.
    Blewins, R. D., (1984). Formulas for natural frequency and mode shape. R.E. Krieger publishing CO., INC.Google Scholar
  5. 5.
    McConnel, K. G., (1995). Vibration Testing, Theory and Practice. JOHN WILEY & SONS, INC.Google Scholar
  6. 6.
    Sung Kyun Kim, Hong Hee Yoo Vibration Analysis of Rotating Composite Cantilever Plates, KSME International Journal. Vol. 16 No.3. pp. 320-326, 2002 Google Scholar
  7. 7.
    P.Castellini, C.Santolini, “Vibration measurements on blades of naval propeller rotating in water”, in: Proceedings of the Second International Conference of Vibration Measurement by Laser Techniques, SPIE 2368, Ancona, Italy, 1996, pp. 186–194.Google Scholar
  8. 8.
    A. Fioretti, D. Di Maio, D. J. Ewins, P. Castellini, E.P.Tomasini, Deflection shape reconstructions of a rotating five-blade helicopter rotor from SLDV measurements, 9th International Conference on Vibration Measurements by Laser and Noncontact Techniques & Short Course, Ancona, 22-25 June 2010.Google Scholar
  9. 9.
    S. Di Battista, D. Di Maio, D. J. Ewins, P. Castellini, E.P. Tomasini, Development of a Comprehensive Mathematical Model for Simulating the Effects of Misalignments in Vibration Measurements using Scanning LDV Measurement Systems, 9th International Conference on Vibration Measurements by Laser and Noncontact Techniques & Short Course, Ancona, 22-25 June 2010.Google Scholar
  10. 10.
    P.Castellini, N.Paone, “Development of the tracking laser vibrometer: performance and uncertainty analysis”, Review of Scientific Instruments 71 (12) (2000) 4639–4647.CrossRefGoogle Scholar
  11. 11.
    A. Colombo, Applications of Laser Vibrometry to Rotorcraft Development: on-going projects at AgustaWestland in collaboration with Università Politecnica delle Marche, Oral presentation only, 8th International Conference on Vibration Measurements by Laser Techniques & Short Course, Ancona, 17- 20 June 2008Google Scholar
  12. 12.
    A.Gasparoni, M. S. Allen, S. Yang, M. W. Sracic, P. Castellini, E.P. Tomasini, Experimental Modal Analysis on a Rotating Fan Using Tracking-CSLDV", 9th International Conference on Vibration Measurements by Laser and Noncontact Techniques & Short Course, Ancona, 22-25 June 2010.Google Scholar
  13. 13.
    P.Castellini, G. M.Revel, and E. P. Tomasini, “Laser Doppler Vibrometry: A Review of Advances and Applications”, in The Shock and vibration digest; a publication of the Shock and Vibration, Information Center, Naval Research Laboratory, vol. 30, 1998.Google Scholar
  14. 14.
    P.Castellini, M. Martarelli, E.P. Tomasini, “Laser Doppler Vibrometry: Development of advanced solutions answering to technology’s needs” in Mechanical Systems and Signal Processing 20 (2006) 1265–1285.Google Scholar
  15. 15.
    Martarelli M., (2001). M. Martarelli, Exploiting the Laser Scanning Facility for Vibration Measurements. vol. Doctor of Philosophy London: Imperial College of Science, Technology & Medicine University of London.Google Scholar
  16. 16.
    A. B. Stanbridge, M. Martarelli, and D. J. Ewins, "Scanning laser Doppler vibrometer applied to impact modal testing," in 17th International Modal Analysis Conference - IMAC XVII. vol. 1 Kissimmee, FL, USA: SEM, Bethel, CT, USA, 1999, pp. 986-991.Google Scholar
  17. 17.
    Stanbridge, A. B., Martarelli, M., Ewins, D. J., (2001). Rotating disc vibration analysis with a circular-scanning LDV. In Proceedings of IMAC XIX, Kissimmee.Google Scholar
  18. 18.
    D. Di Maio, D.J. Ewins, Applications of continuous tracking SLDV measurement methods to axially symmetric rotating structures using different excitation methods, Mechanical Systems and Signal Processing, 24, 3013–3036, 2010CrossRefGoogle Scholar
  19. 19.
    P.Castellini, G.M.Revel, L.Scalise, R.M.De Andrade, “Experimental and numerical investigation on structural effects of laser pulses for modal parameter measurement”, Optics and Laser in Engineering, vol.32, pp.565-581, 2000, ed. Elsevier Science Ltd., Northern Ireland, ISSN 0143-8166Google Scholar
  20. 20.
    P.Castellini, G.M.Revel, Laser vibration measurements and data processing for structural diagnostic on composite material, Review of Scientific Instruments, Volume 71, Issue 1, January 2000, 207-215CrossRefGoogle Scholar
  21. 21.
    Martarelli M., Ewins D. J., Continuous scanning Laser Doppler Vibrometry and speckle noise occurrence, Mechanical Systems and Signal Processing, 20, 8, 2006, pp. 2277-2289, ISSN 0888-3270.Google Scholar

Copyright information

© Springer Science + Business Media, LLC 2011

Authors and Affiliations

  • M. Martarelli
    • 1
  • C. Santolini
    • 2
  • P. Castellini
    • 2
  1. 1.Universitá degli Studi e-CampusNovedrateItaly
  2. 2.Universitá Politecnica delle MarcheAnconaItaly

Personalised recommendations