Metrology of vibration measurements by laser techniques

Abstract

Metrology as the art of careful measurement has been understood as uniform methodology for measurements in natural sciences, covering methods for the consistent assessment of experimental data and a corpus of rules regulating application in technology and in trade and industry. The knowledge, methods and tools available for precision measurements can be exploited for measurements at any level of uncertainty in any field of science and technology. A metrological approach to the preparation, execution and evaluation (including expression of uncertainty) of measurements of translational and rotational motion quantities using laser interferometer methods and techniques will be presented. The realization and dissemination of the SI units of motion quantities (vibration and shock) have been based on laser interferometer methods specified in international documentary standards. New and upgraded ISO standards are reviewed with respect to their suitability for ensuring traceable vibration measurements and calibrations in an extended frequency range of 0.4 Hz to higher than 100 kHz. Using adequate vibration exciters to generate sufficient displacement or velocity amplitudes, the upper frequency limits of the laser interferometer methods specified in ISO 16063-11 for frequencies 10 kHz can be expanded to 100 kHz and beyond. A comparison of different methods simultaneously used for vibration measurements at 100 kHz will be demonstrated. A statistical analysis of numerous experimental results proves the highest accuracy achievable currently in vibration measurements by specific laser methods, techniques and procedures (i.e. measurement uncertainty 0.05 % at frequencies 10 kHz, 1 % up to 100 kHz).

Vibration Measurement Using Laser Triangulation for Applications in Wind Turbine Blades

“…It is important to mention that the damping coefficient determined through (8) and ( 9) is for the linear elastic range since (9) was determined from Hooke's Law. If it is required to work in the nonlinear elastic range, it is necessary to remove this restriction and determine a new expression for the strain energy (9).…”

“…Metrology of vibration measurements by laser techniques, as performed by Hans-Jürgen [8], has been presented in several documents and contributions at international conferences in this area. There have been many specific sessions on metrology, calibration, and standards focused on presenting and discussing innovative methods, techniques, procedures, experimental results, and international standards, developed at the National Institutes of Metrology (NIM) and the International Organizations for Metrology or Standardization [9][10][11].…”

Modifications of the sine-approximation method for primary vibration calibration by heterodyne interferometry

“…Drift is usually the greatest disturbing effect in SAM investigations. Recent studies have furnished mathematical relationships allowing one to compute the amplitude and phase measurement deviations (systematic errors) due to drift, and to eliminate them by corrections [11,13].…”

“…The heterodyne version of SAM has been described in numerous previous publications [2][3][4][5][6][7][8][9][10][11][12][13]. In most cases, a reference signal, generated by mixing of two signals from the internal quartz oscillator of the Bragg cell and the external synthesis generator, is required for the generation of quadrature signals, a basis of phase demodulation.…”

“…The considerable size of data can be reduced by refined algorithms developed more recently, reducing the number of samples per vibration period by an appropriate factor (e.g. by a factor of 10, leading to 100 samples instead of 1000 samples per vibration period) [11].…”