Study of Health Monitoring System of Machines by Using Wavelet Transform

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It is very important to estimate the damage rate of machines under the verious dynamic loading from the point of view of guranteeing their safety and developing the scheme of their maintenance. In this study, the health monitoring system to monitor the damage of machines is investigated to assure the safety of machines. The wavelet transform is applied to the analyzed responses of machines and its feasibility is confirmed. The results obtained from this research are summarizeda as follows. (1) Simultaneous analysis of waves propagating through multilayred media consisting of gas and solid fields is done by using the boundary element method. Through this analysis, the location of abnormal signal for machines is identified by using the wavelet transform of responses. (2) The orthonormal wavelet with large N for Daubechies wavelet can give the good estimation for the occurrence time of abnormal signal under the noisy condition. (3) In case of estimating number entering into plastic region by wavelet analysis, Meyer's wavelets are most reasonable among three types of analyzing wavelets. Moreover, as the change of hysteretic restoring force of system becomes large, number entering into plastic region can be estimated remarkablely.