Biomedical Engineering Reference
In-Depth Information
Endoscopic
Grasper
Force Sensor
Soft
Material
Figure 5.1
A typical grasper jaw, elastomeric material, and FSR sensor (See Plate 9)
the absence of soft tissue, we tested elastomeric materials which exhibit many of the same
complexities and structures as are to be found in soft materials (e.g., material nonlinearity
and viscoelasticity). A typical grasper jaw and soft object (i.e., elastomeric material) and
force sensitive resistor (FSR) sensor are shown in Figure 5.1.
5.3 Method
As shown in Figure 5.1, in order to measure the force experienced by the grasped object,
a force (piezoelectric) sensor was inserted inside the material to be grasped in order to
measure the average force transmitted to the grasped object.This sensor is actually an
FSR, from Interlink Electronics, whose resistance changes in inverse proportion to any
force applied on its surface. The selected sensor was very small, thin, and flexible in order
to be as unobtrusive as possible, and thereby avoid spurious readings.
For the experiments, as shown in Figure 5.2, an endoscopic grasper was equipped with
two sensory devices. One was a potentiometer used to measure the grasper jaw angle. The
second was an FSR affixed to the grasper handle in order to measure the force applied by
the surgeon's thumb. The jaws clamp onto the material to be grasped, in which another
FSR is inserted, in order to measure the force applied to the material.
Potentiometer
Jaws
FSR
Figure 5.2
A picture taken from an endoscopic grasper equipped with two FSR sensors and a
linear potentiometer (See Plate 10)
