Myoelectric Prosthetic
The myoelectic prosthetic
project consists of a skin patch
myoelectric signal collection
module and contactless
transmission system providing
emulation of the electric
signals used to control current
elbow, cuff, gripper arms and
also supporting additional
control functions for future
prosthetic arm functionality.
An adhesive patch is applied to
the skin at a point where it has
been found to have optimum
control. These signals are
processed and sent over a short
distance wireless link to a unit
mounted on the prosthetic.
This project sets out to achieve
a balance between a flexible,
usable hand and a control
system using myoelectric pickup.
All of the prosthetic motion
control we researched uses 'joint'
control. The user activates each
joint in turn in order to get
the 'end point' or 'fingertips'
to a desired location.
This is in contrast to the
normal human movement in which
fingertips are moved in three
dimensional space without
awareness of the specific joint
angles to get there.
This method of control is
preferred in programming robotic
arms. The joint positions of the
arm are calculated using inverse
kinematics.
A myoelectric
signal, although low
voltage and subject to hum and
other pickup, is proportional to
the intensity of the muscle
contraction and present
throughout contraction.
This renders it very
suitable for simple analogue
control systems and allows users
to apply appropriate force using
a combination of learned
behaviour and visual feedback.
Myoelectic signals are generated
for all muscles although only a
selection of muscles are on the
surface where the signals can be
picked up by skin contact.
One of our main aims during this
project has been to create a skin
patch that would pick up
myoelectic
control signals
in a reliable manner for
more precision in prosthetic
control.The pickup of
relatively few myoelectric
signal channels from selected
muscle groups, and the
application of
robotic control derived
techniques, enables a
combination of signals from
these channels to provide
multiple functions.