Biomedical Engineering Reference
In-Depth Information
(a)
(b)
(c)
Lumps
configurations
Experimental
results
Finite element
results
Figure 8.23
The experimental and analytical results for two-dimensional localization. Each row
illustrates the information of the studied case. In the right-hand column, the dashed line represents
the output voltages of the lower array of the sensors, while the solid line is associated with the
upper jaw
can be seen in the graphical representation, as well as finite element analysis. In the third
case (Figure 8.22c) a larger lump is placed between two smaller lumps. It is shown that
the system is capable of detecting all three masses. However, the darker band associated
with sensing element 4 gives information on the relative size of the middle lump with
respect to the others. In the last case (Figure 8.22d) a small lump had been positioned
between two larger lumps. As can be seen from the results, the sensor was unable to detect
the smaller mass. A closer examination of the finite element stress distribution shows that
the two larger lumps created a stress profile between themselves in such a way that the
effect of the small mass had been suppressed. This figure demonstrates that for multiple
lumps with different sizes and locations, and in order to obtain an accurate result, more
than one attempt in different orientations might be needed.
Alternatively, Figure 8.23 shows the results of four case studies in which both jaws of
the graspers were equipped with arrays of sensing elements. Figure 8.23a demonstrates
a case in which two identical lumps were positioned close to sensing elements 1 and
4 of the upper jaw (1
U
and 4
U
) respectively. The corresponding graphical image shows
clearly the location of the lumps and, in conjunction with the grayscale image, gives some
information about the size of the lumps.
In the next configuration (Figure 8.23b), lumps are positioned apart in such a way that
one lump is placed beneath sensing element 4
U
and the second lump is placed above
sensing element 1
L
(slightly overlapped with sensing element 2
L
). The graphical image
constructed, based on the experimental sensor's output, is shown in the middle column
of Figure 8.23b, in which the position (in
x
-and
y
-directions) is clearly extractable. The
gray levels, in this case, can be compared with those of Figure 8.23c in which the lumps
are positioned far from the sensing elements.
Again the position and size of lumps can be clearly perceived from the experimental
data shown in the middle column. In all three cases, the finite element results shown in
