Analysis and diagnosis on the dynamic behavior response of the mechanical structures

• Main Authors: Che-Kang Chang, 張哲綱
• Other Authors: S-Y Lin
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/aa8xg8

碩士 === 國立虎尾科技大學 === 機械與機電工程研究所 === 96 === The dynamic behaviors of the mechanical structures commonly utilized in industry are analyzed in this study. The application scope of a motor is widespread such as for the situations of material processing, positioning and power transmission. The development of vehicle engineering is one of the important focus industry policies in our country. Therefore, the rotary structure of the motor and the vehicle vibration absorber structure are selected as the objects for the dynamic behavior response measurement, analysis, diagnosis and assessment in this study. The first part of this study is to determine the modal shape and to calculate the response frequency through the numerical simulation, under the excitation of critical rotational speed via the experimental measurement for a servomotor structure utilized in industry. Spectrum analyzer in conjunction with accelerometer is used to measure and analyze the response of the structure dynamic behavior in experiment. The analysis method for the response of the structure dynamic behavior is through the characteristics of the spectrum waterfall pattern which is exhibited during the acceleration/deceleration process of a motor. The test method of the spectrum waterfall pattern is easily influenced by the noise signal deduced from the environment and the judgment accuracy for structure resonance is reduced from the critical speed excitation as before. Single point grounded skill is utilized to improve the judgment accuracy in this study. A comparison between the data collected from the structure dynamic behavior response measurement and the result obtained from the modal analysis. Their combination is further utilized to establish a procedure for structure resonance judgment. As a result, the accuracy for structure resonance judgment from the spectrum waterfall pattern excited by the critical speed of a rotary structure may be increased exactly. The second part of this study is to monitor the vibration and displacement response when a car travel on a real road condition through the combination of vibration measurement and spectrum signal analysis scheme. Spectrum analyzer, accelerometer and displacement transducer are first used to detect the vibration of a vehicle body, absorber system frame and rigid axle. The on-line signals acquired are then processed for the dynamic behavior response analysis through the Fast Fourier Transform with Power Spectrum Density and Cepstrum, and Overall analysis method exhibiting the characteristics of the vibration signals. The lack of power spectrum density analysis usually performed in vehicle body and absorber system as before is supplementary by this complete analysis. The maximum frequency of the vehicle vibration variation may exactly be determined through this cepstrum analysis. As a result, the vibration energy under this maximum frequency and its violent dynamic response may be effectively reduced. The comfortable and safe performances may be promoted when a car travel on a road based on this improvement proposed.