Scanning Laser Vibrometry Assessment of Sports Equipment

Transcription

1 Scanning Laser Vibrometry Assessment of Sports Equipment 20 th September 2007 Polytec Vibrometer User s Meeting Mr

2 Contents Introduction PSV-300, 2D Soccer analysis. PSV-400, 3D Soccer analysis. Cricket bat and Tennis racket analysis. Slide 2: 23 November, 2007

3 Loughborough What we do Computer modelling and simulation Design and prototype manufacture Analysis of ball / implement impacts Instrumentation and measurements Equipment testing Elite Player testing and analysis Access to elite players and sports facilities Slide 3: 23 November, 2007

4 2D Soccer Ball Modal Analysis - Introduction 2006 World Cup. adidas teamgeist ball sold over 15 million replicas. Continuing strides to create a ball that exhibits better flight and impact characteristics. Continuing battle between manufacturers to innovate and create a more advanced soccer ball. web.deu.edu.tr Slide 4: 23 November, 2007

5 2D Soccer Ball Modal Analysis Introduction Axe et al. (2002), The vibrational mode structure of a golf ball. Reports discrete frequencies at which golf balls can vibrate, mode patterns of these vibrations and how mode shapes are excited. Journal of Sports Sciences, 20, Shannon & Axe (2002), On the acoustic signature of golf ball impact. Background information on vibrations, techniques to acquire and analyse data also analysis of sound produced by impacting golf balls. Journal of Sports Sciences, 20, Slide 5: 23 November, 2007

6 2D Soccer Ball Modal Analysis - Introduction Tennis ball impact at 6000 FPS Slide 6: 23 November, 2007

7 2D Soccer Ball Modal Analysis - Introduction SLDV versus Accelerometer Avoids physical interaction between transducer and target. Removes mass loading effect. FIFA inspected soccer ball weight grams. High Spatial density. Eliminates predicting mode shapes. Speed and ease of recording measurements. Repeatability, stable sensitivity of transducer over time Slide 7: 23 November, 2007

8 2D Soccer Ball Modal Analysis - Preliminary testing Non-marking methodology No retroreflective markers Polytec PSV 300 Frequencies: 0 Hz 30 MHz Vibration Amplitudes: 2pm 10m Vibration Velocities: 50 nm/s 30 m/s Strong SNR Area of Poor SNR Slide 8: 23 November, 2007

9 2D Soccer Ball Modal Analysis - Preliminary testing Acoustic Excitation Mechanical Excitation 6.3 Hz, 50 Hz 150 Hz 50 Hz 150 Hz Acoustic versus mechanical excitation source. 334 Hz, 390 Hz 334 Hz 390 Hz 950 Hz 981 Hz 443 Hz 950 Hz 981 Hz 1000 Hz 1156 Hz 1000 Hz Slide 9: 23 November, 2007

10 2D Soccer Ball Modal Analysis - Final Protocol Puma and adidas soccer balls under test. Target suspended at valve. Target excited acoustically, by whitenoise and sinusoidal input. Grid of orthogonal, equispaced points projected onto target. These points calibrated with laser. Slide 10: 23 November, 2007

11 2D Soccer Ball Modal Analysis - Final Protocol Polytec Software Fast Fourier Transform (FFT) Bandwidth 20 khz 320 ms per measurement. Frequency resolution Hz Trigger level 5% 283 grid points measured. Slide 11: 23 November, 2007

12 2D Soccer Ball Modal Analysis - Final Protocol Slide 12: 23 November, 2007

13 2D Soccer Ball Modal Analysis - Schematic of optical setup adapted from (Polytec 2000) Where:- PBS = Polarising beam splitter L = Lens WP = Quarter wave plate BC = Bragg cell BM = Beam Splitter Slide 13: 23 November, 2007

14 2D Soccer Ball Modal Analysis - Results Resonant Frequencies of Soccer Balls. 2 Magnitude, μm/s 2 Ball A Ball B Frequency, Hz Slide 14: 23 November, 2007

15 2D Soccer Ball Modal Analysis - Results ODS at lower frequency of excitation Slide 15: 23 November, 2007

16 2D Soccer Ball Modal Analysis - Results ODS at higher frequencies of excitation Ball B Slide 16: 23 November, 2007

17 2D Soccer Ball Modal Analysis - Results ODS at higher frequencies of excitation Ball A Slide 17: 23 November, 2007

18 2D Soccer Ball Modal Analysis - Results Ball A Slide 18: 23 November, 2007

19 2D Soccer Ball Modal Analysis - Results Ball A, valve facing Slide 19: 23 November, 2007

20 3D Soccer Ball Modal Analysis - Introduction 2006 World Cup Ball, Modal analysis Slide 20: 23 November, 2007

21 3D Soccer Ball Modal Analysis - Setup Slide 21: 23 November, 2007

22 3D Soccer Ball Modal Analysis Scan Grid Two separate scans carried out, possible to stitch together Left Side Right Side Slide 22: 23 November, 2007

23 3D Soccer Ball Modal Analysis Scan Grid Side on Face on Above Slide 23: 23 November, 2007

24 3D Soccer Ball Modal Analysis - Results Resonant Peak at 258, 306 Hz 381 Hz 475 Hz 585, 659 Hz Slide 24: 23 November, 2007

25 3D Soccer Ball Modal Analysis Results, Excitation at 258 Hz Slide 25: 23 November, 2007

26 3D Soccer Ball Modal Analysis Comparison with FPS Slide 26: 23 November, 2007

27 3D Soccer Ball Modal Analysis Results Above Face on Excitation at 306 Hz Slide 27: 23 November, 2007

28 3D Soccer Ball Modal Analysis Results Excitation at 475 Hz Slide 28: 23 November, 2007

29 Cricket Bat Modal Analysis Measured impact location, vibration and elicited players response to a shot Player feels painful/pleasant vibrations through handle. 1 st Mode 2nd Mode 3 rd Mode Slide 29: 23 November, 2007

30 Tennis Racket Modal Analysis Vibrations are a huge part of tennis racket performance. Most novice players are aware of the sweet spot when striking the ball. Slide 30: 23 November, 2007

31 Overall Conclusions SLDV desirable tool in Modal analysis of any sports equipment. Acoustics research Validation of FE models. Sound Pressure Level, Kilo Pa 3.00E E E E E E-05 Power Spectrum <2 khz Figure 11.4 Subject Y, Power Spectrum <2000Hz Fv 21 Nike 23 Puma 31 Roteiro 29 Nike Geo Merlin adidas - Roteiro adidas - Fevernova Puma - shudoh 0.00E Frequency, Hz Slide 31: 23 November, 2007

32 Scanning Laser Vibrometry Assessment of Sports Equipment Thank you for listening. Acknowledgements to Dr Andy Harland, Dr Ashley Symes, Dr David Barras and Mr Rue Hallam Reference: J.Ronkainen & A. Harland, Sports Engineering Journal, Soccer ball modal analysis using a scanning laser Doppler vibrometer, 2007, 10, pp