A multi-point heart rate monitoring using a soft wearable system based on fiber optic technology

Figures

• 

  Figure 1. The soft skin like wearable system with the four FBGs encapsulated into: pictures and geometrical features.

• 

  Figure 2. The calibration curves (experimental data with fitting curves in dotted line and shadowed uncertainty) and the hysteresis loops at velocities mimicking 60 bpm for FBG1, FBG2, FBG3, and FBG4.

• 

  Figure 3. The experimental setup during the test procedure. The SWS (a) taped on the T-shirt, the push button for the signal synchronization (b), the DAQ (c) used to collect the ECG trace and the trigger signal, the ECG sensor (d) and the FBG interrogator (e).

• 

  Figure 4. A block representation of the main steps of the data collection and processing to estimate HR.

• 

  Figure 5. The main steps of the data processing to estimate HR. The SCG signals from the passband filtered FBG1 (blue), FBG2 (magenta), FBG3 (green), FBG4 (orange), and FBGsum (purple) and the ECG signal (red) are shown. The zoom on two consecutive peaks of SCG and ECG signals is reported, highlighting AO and R peaks. The SCG envelopes and the peak detection for a signal from the SWS (i.e., FBGsum) and the ECG is also shown.

• 

  Figure 6. The SCGs from FBG1 (blue line), FBG2 (magenta line), FBG3 (green line), FBG4 (orange line), and FBGsum (purple line) and the ECG signal (red line) and from a single volunteer considering Position 1, Position 2 and Position 3 are shown.

• 

  Figure 7. Schematic of the approach used to group the HR data considering a single position.

• 

  Figure 8. (a) The mean HR values obtained by the FBG1 (blue bars), FBG2 (magenta bars), FBG3 (green bars), FBG4 (orange bars), FBGsum (purple bars) considering the three positions, the three tests and the seven subjects. The reference values estimated by the ECG sensor (red bars) are also reported. (b) The MAE values obtained comparing each HR value estimated by the SWS considering FBG1, FBG2, FBG3, FBG4, and FBGsum with the reference one.