Fig. 1. Three-dimensional force sensor structure

Fig. 2. Sensing principle of fiber Bragg grating

Fig. 3. Horizontal mechanical model of cross beam

Fig. 4. Axial mechanical model of cross beam

Fig. 5. Sensor calibration experimental system

Fig. 6. Coupling interference in all directions of force sensor

Fig. 7. ELM network structure

Fig. 8. Decoupling flow chart of SSA-ELM algorithm

Fig. 9. Influence of different parameters on decoupling accuracy and efficiency

Fig. 10. Relationship between hidden layer nodes， MSE and T_d

Fig. 11. Overall situation comparison of coupling interference

Fig. 12. Comparison of coupling interference in all directions before and after decoupling

Fig. 13. Comparison of type I and Ⅱ errors of each decoupling algorithm