Biomedical Engineering Reference
In-Depth Information
respectively. Because the PVDF base sensing elements were prepared manually, a
discrepancy between the output voltages for equal loads was observed at the beginning.
To compensate for this disparity, a controllable coefficient for each sensing element
was defined. Then, using homogeneous elastomeric materials (without any inclusion),
the outputs of the sensors were adjusted identically. The output voltages of the sensing
elements in both designs were processed and displayed graphically, according to the
explained algorithm.
An elastomeric material of known Young's modulus was used as the bulk soft object
and three metallic balls, simulating lumps of different sizes (3.9, 6.3, and 7 mm), were
inserted into hollow spaces carved out of this material. To change the depth of the lumps,
several layers of the elastomeric material were cut with the same dimensions but with
different thicknesses. The lumps were placed in one of the layers, so that the other
elastomeric layers were used as spacers in order to increase or decrease the distance of
the lump layer from the top and bottom surfaces. A similar experimental set up to that
shown in Figure 8.5 was used.
Lump
Probe
Upper
Jaw
Sensor
Array
PVDF Sensing
Element
Elastomeric
(a)
Upper
Jaw
Upper
Sensing
Array
Lower
Jaw
Lower
Sensing
Array
(b)
Figure 8.21
Photographs of the sensors under the test. (a) The sensor with one active jaw used
for construction of one-dimension graphical images. (b) The sensor with two active jaws used for
two-dimension graphical rendering of detected lumps
