Noncontact Measurement

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Non-contact Measurement

• of Dynamic Rotational Characteristics

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Laser-Doppler Vibrometer - Typology
Single point, out-of-plane
Differential, out-of plane
Rotational
In-plane
3D vibrometer
Scanning
3D scanning
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Rotational Vibrometer

• Measurement of non-uniform rotational
  characteristics and torsional vibrations
• Rotation angle
• Angular velocity
• Speed (r.p.m.)

Applications contactless dynamic research on
combustion engine shafts
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Working principle

• Measurement priciple
• Laser Doppler Vibrometer
• 2 interferometers with defined beam separation d

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Working principle

• Basic formula
• detection of 2 velocity components va and vb at
  the circumflex of a shaft
• This leads to 2 output signals with the doppler
  frequency shift

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Working principle

• Basic formula
• The beam separation is determined by
• If the equations are solved the resultion doppler
  frequency of both interferometers is
• The doppler shift is only determined by the
  system constants d, ? and the rotational speed ?

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Output

• Doppler frequency output is deviced into its DC
  component (rotational speed ?) and its AC
  components (rotational vibration ??). This means
  that also at zero speed can be detected
  (torisonal modal analysis with shaker
  excitaiton)
• Vibrational angle output ?? is computed by
  integration of the ?? signal
• ?? is defined as the difference between the
  rotational angle determined by the mean RPM value
  and the actual rotational angle.

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Output

• Signal processing in OFV-4000 controller

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Specifications

• 8 mm beam separation
• -7000 to 11000 RPM
• angular velocity 60000/S (0.5Hz to 10kHz)
• vibrational angle 10 (1Hz- 10kHz)
• 5 mm beam separation
• -11000 to 17600 RPM

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Increasing max. RPM

• The limitation is the max. Doppler frequency fD.
  It is determined by the wavelenght and the beam
  separation.
• Lower beam separations increase the max. RPM
• Tilting of the optical head reduces the effective
  beam separation and in creases the possibel RPM
  value.

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Increasing max. RPM

• beam separation dd cos ?

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Applications

• 150 Systems of OFV-4000 sold to
• Automotive industrie
• Suppliers for automotive industy
• Research institures
• Universities

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Applications

• Measurements of torsional vibrations on
• crankshafts
• damper tuning
• run up - coast down evaluation
• crankshafts
• electrical machines
• coupled machine-sets

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Applications

• Basic research
• torsional eigenfrequency test
• shaker excitation

OFV-400
fixed
force transducer
??
A
FRF
Vibsoft
shaker
f
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Applications

• Run-up test for electrical motor with coupling
• (torsional)

Motor
Machine
1/RPM signal
Dataacquisition
??