Biomedical Engineering Reference
In-Depth Information
which the centers of the detected lumps are specified:
G U 1 G U 2 ··· G U N
00 ···
0
.
.
.
. . .
0
G r 1 1 G r 2 2 ··· G R N N
00 ···
00
···
G 1 =
(8.15)
0
.
.
.
. . .
00
···
0
G L 1
G L 2
··· G L N
It should be noted that in case of multiple lumps, the center of each lump is mapped to
a row that corresponds to the lump's original depth in the tissue. Therefore, for instance,
G r 1 1 and
G r 2 2 are not necessarily in the same row.
As depicted in step 7 of Figure 8.18, a row interpolation procedure was implemented.
At this step, in each column, three values were known;
G L i . Therefore,
using these values and through a linear interpolation, a new intensity distribution was
assigned to all zeros. The final intensity matrix can be represented as:
G U i ,
G r i i ,and
H 11
H 12
··· H 1 N
H 21
H 22
··· H 2 N
.
.
.
. . .
H
=
[
]
(8.16)
H (M 1 ) 1
H (M 1 ) 2
··· H (M 1 )N
H M 1
H M 2
···
H MN
where the intensity of each cell was calculated from relationship (8.17) as follows:
G r j j G U j
r j 1
H ij
= G U j + ( i
) .
, |
i r j ,
j N
1
1
1
(8.17)
= G r j j + i r j .
G L j G r j j
M r j
H ij
, | r j i M,
1
j N
Figure 8.19c shows the lump position and its approximate size after implementing the
mentioned algorithm when M = N = 7. Evidently, increasing the number of cells in both
directions will enhance the quality of image. Figure 8.19d, for instance, is the constructed
graphical image based on the same sensor's output and enhancement of associated matrix
to M =60and N = 100.
8.3.3 Experiments
An experimental setup was used to generate tactile information by the application of
known loads through the prototyped graspers to soft object which contained a lump. The
graspers were positioned under a probe, which was equipped with a reference load cell,
while the soft object and lump were sandwiched between the two jaws. Photographs of
both prototype graspers, with one and two active jaws, are shown in Figure 8.21a,b,
 
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