Fig. 1. Flow chart of software operator fabrication

Fig. 2. Distribution diagram of fiber Bragg grating implantation

Fig. 3. Flow chart of force measurement at the end of software operator

Fig. 4. Experimental system for measuring force of the software operator

Fig. 5. Relationship between wavelength drift and stress of three fiber grating sensors

Fig. 6. Histograms of the wavelength shift residual errors of the FBG sensor 1(a), 2(b), 3(c)

Fig. 7. Calculated transverse force along X-axis F_x (a) and Y-axis F_y (b) versus the actual value using linear fitting

Fig. 8. Residual caused by actual force and fitting

Fig. 9. Histogram of the residual error of F_x (a) and F_y (b)

Fig. 10. Set of measurements of rectified axial forces by the second-order Bernstein polynomial

Fig. 11. Residual figure of axial force F_z

Fig. 12. Histogram of axial force F_z residual