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CHAPTER 9

Techniques Behind the LMM

Frequency estimation with a digitiser

The interferometer output is recorded with a digitiser and frequency is estimated from the waveform. The Zero-crossing Averaging Method (ZAM) and the Zero-crossing Fitting Method (ZFM) were proposed.

Figure: Frequency measurement using a digitiser (ZAM and ZFM)

• Y. Fujii, J. Valera, "Impact force measurement using an inertial mass and a digitizer", Meas. Sci. Technol., Vol.17, No.4, pp.863–868, 2006.
• Y. Fujii, "Impact response measurement of an accelerometer", Mech. Syst. Signal Process., Vol.21, No.5, pp.2072–2079, 2007.
• Y. Fujii, J.P. Hessling, "Frequency estimation method from digitized waveform", Exp. Tech., Vol.33, No.5, pp.64–69, 2009.
• T. Jin, A. Takita, S. Mitatha, P.P. Yupapin, H.Z. Jia, W.M. Hou, Y. Fujii, "Method for acceleration measurement using a laser Doppler interferometer", Meas. Sci. Technol., Vol.24, No.7, 077001, 2013.

Latest result (2026)

Pendulum mechanism

A mechanism that supports the mass with a pendulum instead of an air bearing.

• Y. Fujii, "Pendulum for precision force measurement", Rev. Sci. Instrum., Vol.77, No.3, 035111, 2006.

Dual-beat interferometer

A laser Doppler interferometer that uses both beat frequencies, enabling measurement of high-speed motion.

Figure: Dual beat-frequencies laser Doppler interferometer (Rev. Sci. Instrum., 2011)

• A. Takita, H. Ebara, Y. Fujii, "Dual beat-frequencies laser Doppler interferometer", Rev. Sci. Instrum., Vol.82, 123111, 2011.

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Contents

• Home
• 1. Principle
• 2. Why It Is Needed
• 3. Space Balance
• 4. Dynamic Calibration
• 5. Dynamic Error Correction
• 6. Air-Bearing Friction
• 7. Material Testing and Micro-Force
• 8. Biomechanics and Impact
• 9. Measurement Techniques
• 10. Papers
• 11. Contact

The Levitation Mass Method: precision force measurement by the definition of force | Yusaku Fujii (Gunma University)