Fig. 1. New FBG vibration sensor. (a) I-typed section; (b) structure diagram; (c) physical drawing

Fig. 2. Modal simulation of the sensor. (a) Displacement nephogram of the first order modal; (b) strain nephogram of the first order modal

Fig. 3. Strain distribution. (a) Strain distribution of black curve position with length of 20.0 mm; (b) strain distribution at the grating paste position

Fig. 4. Sensor performance simulation. (a) Frequency response at acceleration of 2.0g; (b) accelerated response at vibration frequency of 300 Hz

Fig. 5. Testing system of the sensor

Fig. 6. Time-frequency response curves of the senor. (a) Time domain at 90 Hz; (b) frequency domain at 90 Hz; (c) time domain at 350 Hz; (d) frequency domain at 350 Hz

Fig. 7. Amplitude frequency response curve of sensor

Fig. 8. Spectra of short grating at different frequencies. (a) 90 Hz; (b) 350 Hz

Fig. 9. Acceleration response repeatability curve

Fig. 10. Anti-interference characteristic curve

Fig. 11. Structural damage simulation of I-beam

Fig. 12. Schematic of I-beam working condition

Fig. 13. Time-frequency domain response characteristic of the senor. (a)Time domain response of health status; (b) frequency domain response of health status; (c) time domain response of one crack; (d) frequency domain response of one crack ; (e) time domain response of two cracks; (f) frequency domain response of two cracks

Fig. 14. Energy ratio of three operating frequency bands. (a) Health status; (b) one crack; (c) two cracks

Fig. 15. Wavelet packet energy ratio characteristic

Fig. 16. Identification and comparison results between ELM and BP

Table 1. Damage mode and corresponding output form

Table 2. Verification result of two damage identification models