Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

An Introduction to Non-Contact Vibration Measurement

4,477 views

Published on

Learn about the technique that is continuing to revolutionize the measurement of structural vibration and shock. The webinar will cover its widespread application to aerospace, automotive, civil, biological, medical and micro- structures.

Topics Include:
- Concept and theory of Laser Doppler Vibrometry
- Product types – scanning and non-scanning
- Example applications including modal analysis, dynamics characterization, production quality testing and FEM validation

Published in: Technology, Business
  • Be the first to comment

An Introduction to Non-Contact Vibration Measurement

  1. 1. 1 Laser Vibrometry: An Introduction to Non-contact Vibration Measurement
  2. 2. 2  Introduction to Polytec  Technology Overview  Advantages and Limitations  Polytec’s Product Portfolio  Applications Examples Outline
  3. 3. 3  Automobiles, construction, agriculture...  Airplanes, satellites, missiles, drones...  Home appliances, power tools...  Data storage and semiconductor  Microstructures, microacoustics, MEMS and nanotechnology  Entertainment, eg: Loudspeakers, microphones, gaming devices, watches, haptic feedback .....  Life sciences (Biology – cells, macro-molecules, entymology, animal communications. Medical – clinical, surgical, diagnostic, therapeutic, dentistry)  Manufacturing & quality control  Structural health monitoring, NDE ....  Optical industry & telecommunications  Defense equipment  Earthquakes  Energy harvesters  Ultrasonic transducers Vibration is Everywhere
  4. 4. 4  Modal analysis  Troubleshoot noise and vibration issues  Transducer development  Finite element model validations  Identify noise sources and map energy paths  Stress and strain mapping  Structural health monitoring  Photoacoustic tomography  Learning from nature  Studying smart structures  In-line quality control The Need to Measure Vibrations
  5. 5. 5  Founded in 1967  ~400 employees worldwide  75 in R&D  Vibrometers since 1986  Gold standard for non-contact measurement solutions in many industries Data Storage Automotive QC MEMS Medical Aerospace Biology Ultrasonics World Leader in Optical Measurement
  6. 6. 6 Geographically positioned to respond effectively to customer needs 5 offices Service center in Hudson, MA Application labs Representative offices 2500+ customers in North America actively use Polytec’s products and services. North America
  7. 7. 7  Laser Doppler Vibrometers For non-contact vibration measurements  Laser Surface Velocimeters For surface speed and length measurements  White Light Interferometers For surface topography or profile measurements in roughness, waviness, form or step-height applications  Acoustic Cameras For visualizing and analyzing sound Optical Measurement Solutions
  8. 8. 8 Optical Measurement Solutions  Laser Doppler Vibrometers For non-contact vibration measurements
  9. 9. 9 Laser Doppler Vibrometry The Technology
  10. 10. 10 Detects Doppler shift Analogous to acoustic Doppler effect High-precision laser interferometer Accurate and precise time-resolved output proportional to vibration displacement or velocity Available easy-to-use data acquisition & software processing Available hardware and software for full-field data The Technology
  11. 11. 11 What is Laser Doppler Vibrometry? Laser Doppler Vibrometry is a non-contact, "point and shoot" technology that directly measures the vibration of a test object using the Doppler effect. PDV-100 Portable Digital Vibrometer Analogy: Acoustic Doppler Effect Sound emitted from stationary car has frequency f = c/l For car moving at velocity v, the observer hears the frequency fD = c/(l - v/f). v c l For a vibrometer: Δ fD α v Δ fD = 2v/l Emitted frequency f Observed frequency fD c: velocity of the sound wave l: emitted wavelength f: emitted frequency
  12. 12. 12 What does Laser Vibrometry Provide?  Modulations in the laser frequency are converted to a voltage output proportional to instantaneous velocity  Changes in optical phase are converted to a signal proportional to displacement ODS and modal analysis Time History Impulse Response Frequency Response
  13. 13. 13 Bragg cellf0 ± fD f0 f0 + 40 MHz He-Ne Laser <1mw (633nm) x(t) v(t) Photo-detector Measurement Beam Reflected Beam ΔfD = 2v/lFrequency Modulated signal 40 MHz ± fD The Heterodyne Interferometer
  14. 14. 14 FM Doppler signal Controller Photo-detector system Voltage ~ Velocity Voltage ~ Displacement AM electrical signal FFT spectrum Signal Demodulation
  15. 15. 15 Components of an LDV System  Sensor Head - Laser source - Interferometer optics - Receiving electronics - Camera  Controller - Decoders for: Velocity Displacement - Filters Lo- and hi-pass  Data Acquisition - Polytec VibSoft - User-supplied FM signal (high frequency) ± 10 V velocity or displacement signal
  16. 16. 16 Different Configurations Single/Multi- Point Scanning 3 Axis Scanning 3 Axis Differential Long Range
  17. 17. 17 m² mm² µm² single point scanning From Macro to Micro to MEMS
  18. 18. 18  Higher accuracy – no mass or stiffness added, sub-µm spatial resolution, picometer displacement resolution, frequency and temperature independent, pre-calibrated (calibration and resolution unaffected by distance or field-of- view)  Cost and time savings – point and shoot, easier set-up, nothing to attach, typically no surface preparation, laser may be scanned for rapid full-field data, only one transducer to calibrate, NO extensive analysis required to get results  Wider range of operation and applications – in vacuum, through windows, high frequency, large amplitude, hot, lightweight, long range, rotating, inaccessible or microscopic Why Laser Doppler Vibrometry (LDV)?
  19. 19. 19 Higher Accuracy  frequency and temperature independent  fine spatial resolution  Down to <1µm  For micro-structures  And measurements closer to edges  sub-pm displacement resolution  With digital decoding  no mass or stiffness added  Delicate, lightly damped structures Benefits
  20. 20. 20 Accelerometer Response Benefits - Comparison with Accelerometer
  21. 21. 21 Vibrometer Response (w/o Accel) Benefits - Comparison with Accelerometer
  22. 22. 22  point and shoot  Target almost anything quickly and easily  Easier set-up, nothing to attach, close or far  laser may be scanned for rapid full-field data  Amplitude and phase spectra at up to >250k points  More comprehensive data for a more complete modal analysis or FE validation Benefits Cost and Time Savings
  23. 23. 23 Wider Range of Operation and Applications - I  wide frequency range (DC – 1,200 MHz)  large amplitude range (to 40 m/s)  no surface temperature limit Benefits
  24. 24. 24  submerged  through windows  delicate Wider Range of Operation and Applications - II Benefits
  25. 25. 25  inaccessible  rotating  remote  microscopic Benefits Wider Range of Operation and Applications - III
  26. 26. 26  On macro- and micro-structures  Tailored solutions for:  Research, production, industrial and in-the-field environments  Ultrasonic and high amplitude applications  Structures at remote distances OFV-505 PDV-100 Single Point Solutions OFV-534 with integrated video and illumination
  27. 27. 27 RSV-150 long range laser vibrometer  Bridge height 108m  Steel framework  Distance > 140m  Excitation: train displacement of the bridge during slow transit of train Single Point Solutions
  28. 28. 28 Thermomechanical characterization of tungsten filaments Single Point Solutions
  29. 29. 29 Differential Measurement Example: HSV-2000 Engine valve-train testing:  relative movement between two surfaces  removes background vibration of engine block  12 kHz valve bounce revealed Car engine Two optical sensor heads Beam steering probes -15 -10 -5 0 5 10 15 0 180 360 540 720 Cam Shaft Angle (deg) Velocity(m/s) 7500RPM 6500RPM -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 148 168 188 208 228 248 CamShaft Angle (deg) Velocity(m/s) 7500RPM Dual Beam Solutions
  30. 30. 30 RLV-5500 Rotational vibrometer measures pure angular motion – independent of test object shape or any lateral vibrations Measured Outputs:  DC rpm value  Angular velocity signal  Angular displacement Example Applications:  Order tracking analysis  Crankshafts  Propshafts Rotational Solutions
  31. 31. 31  Two beam separations (d = 7.5mm or 24mm)  Four stand-offs (70mm, 200mm, 400mm, 600mm)  Measures angular velocity and displacement from -8,000 to +20,000 RPM @ up to 20kHz  Eliminates down-time associated with contact methods d f RV RV D BB AA 2 cos cos l       Rotational Solutions
  32. 32. 32 MSA-100-3D integrates 3 independent vibrometers Simultaneously measures three axes of motion at a single point with one laser Calculates Vx, Vy & Vz Scanning stage enables acquisition of full-field data 3-D Solutions
  33. 33. 33 Compared to accelerometers  Laser has no mass, damping, stiffening – BA, MA  Laser can be scanned – F, CS  Long standoffs, through windows, fluids, hi temps – MA, S  No cabling on structure – F, MA, S  Better spatial resolution: spot diameter typically 10s of µm – BA, MA  FEM geometry import for easier, faster point definition – F, LE  One (or 3) transducer(s) to calibrate (no book keeping), LE, CS  No accelerometer rolloff or resonance – to 1.2 GHz!! BA, MA  Spatial aliasing? - More data points BA, LE F [Hz] accelerometers Why Laser Vibrometry? BA = Better Accuracy F = Faster MA = More Applications LE = Lower Chances for Errors CS = Cost Savings S = Safer
  34. 34. 34 19 MP -4.00E-08 -3.00E-08 -2.00E-08 -1.00E-08 0.00E+00 1.00E-08 2.00E-08 3.00E-08 0.234668 0.186155 0.137642 0.0891290.0406156-0.007897 -0.05641-0.104923-0.153436-0.201949 9 MP -4.00E-08 -3.00E-08 -2.00E-08 -1.00E-08 0.00E+00 1.00E-08 2.00E-08 3.00E-08 0.23467 0.1619 0.08913 0.01636 -0.05641 -0.12918 -0.20195 5 MP -2.00E-08 -1.50E-08 -1.00E-08 -5.00E-09 0.00E+00 5.00E-09 1.00E-08 0.234668 0.113385 0.0163594 -0.104923 -0.201949 19points 9points 5points Low point density:  amplitude error  distorted shape 514Hz Spatial Aliasing
  35. 35. 35  Up to 250,000 locations scanned point-by-point – vibration velocity or displacement  Software for exciter signal generation, data acquisition, display & manipulation  Geometry file imported or measured  Animated data visualization  Data export for modal analysis or FEM validation  Up to 25MHz bandwidth System Stitched data Data Management SystemFront-end Sensor Head Scan Electronics HD Video LDV Sensor Scanning Mirrors Scanning Vibrometry
  36. 36. 36 1D Scanning Simple Structures  ODS  Acoustics – noise source identification  Rotating 3D Scanning Complex Structures  Structural dynamics  Modal analysis  FEM validation  Stress & strain  Robot-integrated 1D or 3D Scanning?
  37. 37. 37  Full 3-D vibration response over measurement surface (>2,500 points)  Integrated data stitching provides complete coverage with single system  Precise data for modal analysis and model verification Correlation with accelerometer data out-of-plane 3D Scanning Vibrometry
  38. 38. 38 3D Scanning Vibrometry - RoboVib
  39. 39. 39 Example: deflection shape at 580 Hz Case Study – Steering Knuckle
  40. 40. 40 MSA-500 Micro System Analyzer  Powerful all-in-one measurement workstation for 3-D static and dynamic characterization of MEMS and MOEMS microstructures  Characterization of out-of-plane vibrations with scanning vibrometry PLUS:  Measurement of in-plane motion and vibration with stroboscopic video microscopy  Profiling surface topography with white light interferometry Three Measurement Technologies One Integrated Package Micro Systems Measurements
  41. 41. 41
  42. 42. 42 MSA-100-3D Micro System Analyzer Micro Systems Measurements
  43. 43. 43 Micro/Small Systems Measurements MSA-050 Stage-scanning vibrometer for small/micro structures  Bandwidth up to 2 MHz  50 mm x 50 mm max. scan area  Integrated PSV software  Integrated video
  44. 44. 44 Advanced non-contact vibration measurements available for every budget  Measurements using Polytec’s latest non-contact measurement technology  Application engineers to operate the measurement systems to their fullest potential  Access to the full portfolio of Polytec‘s products  The convenience of testing at either your facility or in one of several Polytec labs  Short-notice, time-critical measurements  No need to invest capital for occasional measurements when ownership is hard to justify  Evaluate the full potential prior to purchase  Greater budget flexibility Engineering Services and Rental Program

×