Creating a Sensory Input Bio-Prosthetic Prototype

Current
upper extremity prosthetic technology can be classified into three categories:
cosmetic, internally powered and externally powered. Cosmetic prosthetics are
used solely to enhance appearance. Internally powered prosthetics (IPP) use
motion of the amputee to function. These systems usually consist of gyros,
cables and other basic mechanical systems. Externally powered prosthetics offer
a wider range of motion as well as more internal functions such as pulley or
servo motor mechanics.

Principal
differences between human limb functionality and mechanical prosthetics are
functionality, strength, range of motion and reciprocity. Though most of these
issues are being advanced within prosthetics using various material
breakthroughs, the reciprocity of the human hand is often overlooked.

The
power of the human hand does not lie solely in the fact that it can manipulate
its surroundings, but that its surroundings can also manipulate it. A human
limb is more than just a mechanized tool; it is a sensory powerhouse that
allows a person to understand his or her environment. The sensory nerves in the
hand allow a person to sense stimuli such as temperature, humidity, chemical
stimulation, acceleration and pressure.

To
mimic these capabilities, a communication system to support a mechatronic
prosthetic is critical. After all, a nervous system feedback system is
essentially a biological mechatronics system complete with wires (nerves),
signals and actuators (muscles and tendons). The purpose of this project was to
investigate the concept of designing a prosthetic hand that could mimic this
reciprocal ability of the human hand, how one would be designed, what
components could be used to create it, and how functional the resulting design
could be.

Basic
Hand Design

The
"Sensory Input Bio Prosthetic Hand" created for this project is a concept
design of a sensor feedback system in a prosthetic system. The hand has two
modes: automatic and manual. The modes can be toggled between by flipping the
mode switch on the underside of the wrist. When the hand is in automatic mode,
it is simply responding to its environment. Any time it detects touch on any of
its five fingertips; it moves that finger into a grabbing position. After a
pause, it moves the finger back to its original position.

Creating a Sensory Input Bio-Prosthetic Prototype

Grabbing
force can be controlled to protect an item being grabbed and to protect the
hand itself. When set in automatic mode, the force dial on the underside of the
wrist can be turned to adjust the maximum force the fingers can impart. If the
dial is turned all the way counter-clockwise, then the hand will move its
fingers as long as any level of touch is sensed. If the dial is turned all the
way clockwise, it will only move until it feels a slight force resisting its
movement. For example, if the operator
wants to grab something solid, like a block, he would turn the dial all the way
counter-clockwise. If the operator wants to grab something light and fragile,
like a flower, he would turn the dial all the way in the clock-wise direction.
Many different settings can be attained for the hand's gripping strength in
between

Comments (0)

Please log in or register to post comments.
By submitting this form, you accept the Mollom privacy policy.
  • Oldest First
  • Newest First
Loading Comments...