Vibration Modal Analysis by High-Speed and Accurate Shape Measurement Using One-Pitch Phase Analysis Method

To protect vibration of structures, vibration modal analysis is important. Conventional experimental vibration analysis method uses accelerometers or laser displacement meters. The analysis takes much time and troublesome work. Especially, by contacting accelerometers to objects the results of frequency mode have some errors because of contact of the accelerometer weight. The authors have previously proposed a new method for shape measurement, i.e. the one-pitch phase analysis (OPPA) method using moire topography. In moire topography, the number of pixels for one pitch is constant regardless of the object height. The OPPA method analyzes the phase of each pixel in a single-shot image by using brightness data from one pitch of a projected grating. A motion capture system has been previously developed using OPPA method and measured the 3D coordinates at every pixel of the surface of a human body. In this study, the OPPA method is applied to vibration modal analysis of a cantilever plate using a high-speed camera. This method is useful for inspection of automobiles, machines, buildings, etc. without contact, in a short time.