Hokkaido University Research Profiles

Manufacturing Technology

Vibration Measurement Technology Using a Non-contact Laser Excitation System

Development of high-frequency vibration measurement and high-sensitivity damage detection technology

We have developed a technique to apply an ideal impulse excitation force using laser ablation generated on a structural surface by high-power pulsed laser irradiation. This technology enables non-contact, high-precision vibration measurement in the high-frequency range, which had previously been impossible.

Content of research

As in Fig. 1, which shows the principle of laser-induced excitation force generation, the laser-induced excitation force is caused by laser ablation. Figure 2 shows an example of the application of this technology, a vacuum environmental excitation measurement system for a membrane structure. This system consists of a YAG-pulsed laser, dielectric multilayer mirror, collecting lens, membrane structure, LDV and vacuum chamber. The membrane structure is fixed inside the vacuum chamber, allowing us to conduct the experiment by adjusting the air pressure inside the chamber from the atmospheric to the vacuum environment. Figure 3 shows the measured frequency response of the membrane. As shown in Fig. 3, with an increase in the vacuum level, the resonance frequency of the membrane becomes higher and at the same time the resonant response level increases. In this way, this technology enables the extraction of both mass effect and damping effect caused by the air on the membrane surface. We have conducted experiments to verify the effectiveness of this technology in a vacuum chamber, which assumes a space environment.

  • Fig. 1: Principle of laser excitation

  • Fig. 2: Vibration test system in a vacuum environment

  • Fig. 3: Change in frequency response due to differences in air pressure

Potential for social implementation

  • ・Monitoring of nuclear facilities, etc.
  • ・Measurement of vibration and diagnosis of damages during actual operation of automobiles, rotating machinery, etc.
  • ・High-precision vibration measurement and characterization in the MEMS field
  • ・Diagnostic applications in biological fields

Appealing points to industry and local governments

It can be applied to objects where measurement and evaluation of vibration in the high frequency range is desired, such as MEMS and ultra-precision positioning equipment.
This technology is extremely useful to measure vibration and evaluate soundness of the systems at nuclear facilities and other places where human work is difficult due to safety concerns.
It can be used to measure and monitor the vibration characteristics of automobiles and vehicles during their actual operation (driving).

Intellectual property related to this research

PCT/JP2011/003412 「Method for Measurement of Vibration Property of Structure, and Vibration Property Measurement Device」
 (日本:特許第5750788号 米国:特許第9,291,604号  欧州:11795411.5)