Fig. 2 Signal plane divided into cell of DWT Fig. 1 Schematic diagram for the monitoring system

Study of Health Monitoring of Vehicle Structure by Using Feature Extraction based on Discrete Wavelet Transform Akihisa TABATA *4, Yoshio AOKI, Kazutaka ANDO and Masataka KATO Department of Precision Machinery Engineering, Nihon University, 7-14-1 Narashino-dai, Funabashi-shi, Chiba, 274-8501 Japan In recent years, development of the wireless communication technology is able to provide useful information and active safety for the drivers. Though many researchers try to monitor a traffic congestion, weather condition, road surface condition and car maintenance by the on-board TV camera or the probe car system, sensor signals of these have non-stationary and transitory characteristics while the vehicle is in motion. In this study, we specially turn attention to the feature extraction for the strain signals while the vehicle is in motion. We examine the local analysis based on the Discrete Wavelet Transform and the Short-Time Fourier Transform applied to the feature extraction of the failure detection. Key Words : Vibration, Sensor, Diagnostic Technique, Monitoring, Stress-strain Measurement, Safety Engineering E-mail : d0604001te@edu.cst.nihon-u.ac.jp

Fig. 2 Signal plane divided into cell of DWT Fig. 1 Schematic diagram for the monitoring system

Fig. 3 Re-composition of signal by DWT Table 1 Experimental conditions Fig. 4 Image of the crest factor

Fig. 5 Time domain response in the driving test Fig. 6 Experimental result of the STFT in Kaiser Fig. 7 Result of the filtering operation

Fig. 8 Result of signal conditioning by DWT (The case of puncture)

Fig. 9 Time domain response in the driving test Fig. 10 Result of signal conditioning by DWC (The case of loosen bolt)

Fig. 12 Location of PVDF sensors in the experiments Fig. 13 Comparison of the crest factor for the light and left side Fig. 14 Relation between runing time and average of the crest factor Fig. 11 Change of the crest factor with the number of loosen bolts (1) Ichiro Kageyama et. al., Study on a road surface sensing system for snow and ice road, Transactions of the Society of Automotive Engineers of Japan, Vol.33, No.4, (2002), pp. 179-184. (in Japanese) (2) Ichiro Kageyama et. al., Study on a Road Surface Sensing System for Snow and Ice road, JSAE Review, Vol. 23, No. 3, (2002), pp. 333-339.

(3) Nobuaki Kawahara, Yasutoshi Suzuki, Automotive MEMS sensor, Journal of Society of Automotive Engineers of Japan, Vol. 59, No. 5, (2005), pp. 87-90. (in Japanese) (4) Masataka Kato, Yoshio Aoki, Health monitoring of vehicle structure by using feature extraction based on the discrete wavelet transform, Proceedings of Annual Meeting of JSME/MMD, (2003), pp. 1065-1066. (in Japanese) (5) Ryosuke Matsuzaki, Akira Todoroki, Wireless strain monitoring of tire using capacitance changes with oscillator, Journal of the Japan Society for Composite Materials, Vo. 30, No. 2, (2004), pp. 55-62. (in Japanese) (6) Kouhei Arai, Fundamental Theory on Wavelet Analysis, Morikita Publishing Co., Ltd.(2000), pp. 28-29. (in Japanese) (7) Hiroaki Nakano, Shizuo Yamamoto, Yasuo Yoshida, Signal processing and image processing by wavelet, Kyoritsu Publishing Co., Ltd. (1999). (in Japanese)