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Force sensing in compact concentric tube mechanism with optical fibers 345

Figure 14.19
Tool tissue interaction in nasal cavity scanning (force).

contact force between the CTR and the surrounding walls was calculated using the
1
calibration matrix, K .
The FBGs experience a moving error in the wavelength shift, as can be seen by the upward
trend in Fig. 14.19. This can be attributed to the constrained space in the nasal passage,
where the CTR maintains constant contact with the surrounding tissue. To determine the
actual change in contact force applied, a moving average trendline was determined, and the
forces were calculated with the deviation from the trendline. The average x-force read by
25
the FBG sensors is 0.0003 N, and the average y-force is 5 3 10 N.
It can be observed from the results that the FBG sensor can detect forces in the range of
0.1 mN accurately, with the peaks and troughs indicating contact between the nasal tissue
within the 6 2.5 degrees range of the CTR’s movement. The marked shift in force at
t 5 60 seconds was attributed to the slight repositioning of the cadaver head, and the
remaining results can be seen to be reasonably consistent.

14.8 Conclusion and future work

A novel compact CTR was presented for the purpose of MIS and enhanced using FBG
sensors to obtain tactile force information during the surgical procedures. Experimentation