Biomedical Engineering Reference
In-Depth Information
applications, such as providing professional development to teachers for which one of the
most effective forms is coaching, or cognitive apprenticeship [24].
One promising new advent in the use of telepresence is its use in performing real-time
surgical operations, as demonstrated in Regensburg, Germany in 2002. Also the transfer
of haptic (tactile) information has also been demonstrated in telemedicine [25].
10.3 Basic Elements of a Teletaction System
The general elements of a teletaction system are shown in Figure 10.4. As previously
stated, a teletaction system is the means by which an operator is presented with information
about the texture, local shape, and/or compliance of a remotely located object through
the use of a tactile display system. One of the more demanding medical applications of
teletaction is the employment and use of robotic laparoscopic telesurgery systems. A tactile
sensor is mounted on the end-effector (the laparoscopic instrument) and a tactile display
is mounted on the master manipulator (the user interface) which presents information
gathered by the tactile sensor to the user. Ideally, the patterns felt by the user would be
indistinguishable from direct contact with the environment. The mechanical tactile display
needs to generate surface stresses that realistically represent data collected by the tactile
sensor. To fully control surface stress, the ideal tactile display system would be an infinite
density array of three-DOF actuators.
Generally, teletaction systems are composed of a tactile sensor, a tactile filter, and a
tactile display, as shown in Figure 10.4. Most teletaction work has focused its attention
on tactile sensors and displays with high spatial but low temporal resolutions [11, 27].
A tactile filter, which is typically a computer with A/D and D/A boards, converts tactile
sensor data into tactile display control data. Some concerns regarding tactile filter design,
however, are the spatial and temporal sampling differences between the sensor and the
display. Also, anomalies exist when attempting to filter strain profile data from the sensor,
and convert them to normal and shear force displacement profiles for the display, due to
the inability of the filter to completely remove all noise from the system.
One promising use for a teletaction system is in minimally invasive surgery (MIS).
Figure 10.5 suggests using a tactile sensor mounted on a catheter to allow a surgeon
performing vascular surgery to feel for plaques, branches, or soft spots inside blood
vessels. The teletaction system uses a tactile stimulator to create a pattern of stress on a
fingertip. This pattern is ideally indistinguishable from direct contact of the finger with
the environment.
10.4 Introduction to Human Psychophysics
The term psychophysics suggests a combination of both physics and psychology. More
specifically, psychophysics is a science concerning human and animal sensory responses
Stress
Pattern
Measured
Strain
Tactile
sensor
Tactile
filter
Tactile
display
Environment
User
Figure 10.4
A block diagram representation of a general teletaction system [26]
 
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