Instrumentation & Measurement Magazine 26-3 - 29

Fig. 5. Diagram of image fitting points.
the movement platform to make the finger move slowly along
its own length.
First of all, the planar perception experiment was carried
out, as shown in Fig. 6a. A single finger was placed on the horizontal
silicone block surface, and the finger moved slowly on
the surface of the object under the drive of the moving platform.
The central wavelength of the process was recorded at
the sampling frequency of 20 Hz. The initial bending state was
taken as the initial center wavelength, and the offset was calculated
according to the initial wavelength. The wavelength
offset result is shown in Fig. 6d, basically around 0 pm, and it
can be determined that the surface of the object over which the
soft finger slides is basically flat, that is, the wavelength offset
image is consistent with the actual surface of the object being
slid.
Next, the curved surface perception experiment was carried
out, as shown in Fig. 6b. A single finger was placed on the
curved silicone block surface and the procedure was the same
as in the plane sensing experiment as the soft finger moved
slowly on the surface of the object driven by the moving platform,
and the central wavelength of the process was recorded
at the sampling frequency of 20 Hz. The initial bending state
was taken as the initial center wavelength, and the offset was
calculated according to the initial wavelength. The wavelength
offset result is shown in Fig. 6e, where the wavelength
offset range is 0~300 pm, and the surface of the object sliding
by the soft hand can be judged as a curved surface by the wavelength
offset image.
Finally, the rough plane perception experiment was carFig.
4. Pressure calibration result. (a) Finger 2; (b) Finger 3; (c) Finger 4.
Shape and Hardness Perception
Experiment
Object Shape Touch Recognition
We fixed the palm of the soft hand on the three-axis movement
platform, so that it could move in three directions in a straight
line, and then placed the object to be identified directly under
the finger, with a certain initial bending of the finger, and set
May 2023
ried out, as shown in Fig. 6c. The previous steps were repeated,
and the wavelength offset result is shown in Fig. 6f. In the sliding
process, the maximum offset of the center wavelength was
about 180 pm, and the surface of the object can be judged as a
rough surface with four grooves by the wavelength offset image.
When a finger slides horizontally across the surface of an
object in a curved state, the degree of bending of the finger itself
will be affected by the shape of the object. Because of the
flexibility and adaptability of the soft hand, the surface shape
of the object will force the finger itself to adapt to this change.
Combining with the FBG element which senses the bending of
the finger, the whole process can be recorded.
IEEE Instrumentation & Measurement Magazine
29
Instrumentation & Measurement Magazine 26-3

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