Objective Measurement of Rattle Problems

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Objective Measurement of Rattle Problems
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The Problem

• Rattle In Vehicle Interior Components
• is easily picked up by passengers
• is a common warranty problem
• can be difficult to locate point of origin
• assessment of severity requires experienced
  assessors
• production monitoring difficult
• requires quiet environment
• requires experienced operator
• depends on subjective evaluations

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The Solution

• Measure vibration simultaneously at key points
  around structure
• requires phase matched transducers and parallel
  sampling
• Optimum locations need to be determined for each
  structure
• Shaker used to provide repeatable inputs
• Special analysis extracts rattles and shows
  levels
• levels correlate with subjective ratings
• pass/fail criteria can be established for end of
  line testing
• Sine Sweep test yields Rattle v Frequency plot

4
Sine Sweep Frequency curve extraction
MeasuredVibration signal
Sine pulses extracted
Frequency vs Time Calculated
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Sine Sweep Impact levels extraction
High-Pass Filtered
MeasuredVibration signal
Maximum levels extracted
Plotted against Frequency
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Example Rattling in Car Seat

• Seat Fixing bolts and Headrest Rods used as
  standard measurement locations
• Data sampling rate 20kHz to capture rattles
  (short duration impacts)
• Measurement duration
• Sine sweep 1 complete sweep
• Random or cobblestones 30 Seconds

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Vibration Measurement Positions
Headrest Rods
Seat fixing bolts
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Sine Sweep Test showing Rattle Levels vs.
Frequency
Headrest Rattles
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Sine Sweep test showing subjective correlation
VR6
VR4
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Random Excitation Signal
Current Material
New Material
VR6
VR4
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Conclusions

• Objective measurements correlate well with
  subjective ratings
• Objective plots give information about frequency
  of problems
• Measurement is simple and quick
• sensors attached magnetically at easily
  accessible locations
• Analysis is quick
• DATS Macro runs in seconds
• Saved graph layout provides standard format
• Plots can be directly pasted into reports
• Reliable Automated End of Line Monitoring Possible

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End