Applications of Operational Modal Analysis in Gearbox and Induction Motor, Based on Random Decrement Technique and Enhanced Ibrahim Time Method

Abstract

There have been steadily growing requirements from the academia and industry, demanding non-invasive methods and reliable measurement systems of research devoted to operational mode analysis (OMA). Due to the simplicity of performing only structures surface vibration measurements, OMA is frequently applied in machine fault diagnosis (MFD) and structure health monitoring (SHM). OMA can handle big structures, such as bridges, buildings, machines, etc. However, there is still an open question: how to properly handle the harmonic effects of rotating components and the difficulty of closely estimating space modes are still a nightmare to deal with. Therefore, the main objective of this paper is to identify the structure of natural frequencies by the regeneration of frequency response functions (FRFs) for complex structures based on OMA. The novelty of our approach is to use the random decrement technique (RDT), correlation function estimation (CFE), and enhanced Ibrahim time method (EITM) to overcome OMA’s difficulties and limitations. To reduce further rotational harmonics effects, gear mesh and side band frequencies, digital signal processing techniques based on notching filters, and liftering analysis techniques were also used. All the experiments were performed at the laboratory test rig and conducted by using three accelerometers, one impedance hammer, one force sensor, and one data acquisition board. To reduce data’s variabilities, each test was measured three times for 5 min. The data sampling frequency for all the experiments was 25.6 kHz. To validate the proposed methodology, extensive OMA tests were performed for the generation of FRFs. The measured objects were a steel bar, induction motor, and gearbox. Five structural natural frequencies for the induction motor and eight structural natural frequencies for the gearbox were generated, respectively.

Observation and Prediction of Instability due to RD Fluid Force in Rotating Machinery by Operational Modal Analysis

“…And the validity was then confirmed by comparison with EMA. Castro and Zurita (2022) proposed a method to remove harmonic components, which is a challenge for OMA for rotating machinery, and verified it through experiments. However, to the best of the author's knowledge, there are no studies that use OMA to estimate the modal parameters of the system considering the RD coefficients and observe or predict the process of destabilization of rotating machinery.…”

Operational and Analytical Modal Analysis of a Bridge Using Low-Cost Wireless Arduino-Based Accelerometers

“…On the other hand, MEMS a erometers are silicon-based sensors that found their way into many industrial applica due to their significant ongoing technological developments. The most significant advantage of OMA in comp modal characterization in natural operating condition excite the structure [30]. Consequently, in civil engine are typically used for bridges [31].…”

“…The most significant advantage of OMA in comparison with EMA and ISMA is its modal characterization in natural operating conditions when it is difficult to artificially excite the structure [30]. Consequently, in civil engineering applications, OMA methods are typically used for bridges [31].…”

Modal and Structural Identification of Historic Bell Tower in Čuntić, Croatia Using Ambient Vibration Testing

“…The bell tower was damaged during the Petrinja earthquake in such a way that its functionality was compromised, so an evaluation of its seismic resistance is required. Recently, the application of the results of experimental determination of modal parameters with AMT for different buildings has gained importance [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. Gentile and Saisi [15] presented the results of investigations based on ambient vibrations carried out to evaluate the structural condition of a masonry bell tower built in the XVII century and about 74 m high.…”

“…They determined operational acceleration and strain responses to train passage and developed a new damage index by formulating a strategy to combine damage features obtained individually from acceleration and strain analysis. Castro and Zurita [32] presented the application of OMA to gears and induction motors, based on the random decrement technique and the extended Ibrahim time method. This work shows how far the application of OMA goes beyond monitoring the condition of structures in civil engineering.…”