Dubbed the
neuroArm, it’s the brainchild of neurosurgeon
Dr. Garnette Sutherland
and his team of researchers.
The neuroArm is designed to operate
on the head of a patient sitting
in an MRI machine. A surgeon at a
workstation controls the arm using
real-time MR imaging as a guide.
And the robot’s hand is actually
steadier than that of a human surgeon.
A surgeon’s hand is stable to
about 100 microns, say developers,
but the neuroArm is good to about
25 microns.
MacDonald, Dettwiler, and
Assoc. (MDA), makers of the Space Shuttle’s Canadarm, did the main engineering work.
One of the tricky parts of the design was coming up
with nonmagnetic motors and bearings. “Magnetic
materials in the MRI field generate artifacts on the
image the doctor uses to make decisions,” explains
Alan Feinstein, CEO of Nanomotion Ltd., part
of Johnson Electric’s Medtech group. Nanomotion
supplied the motors that power neuroArm’s
six axes.
The Nanomotion motors use PZT, a piezoelectric
ceramic, to move a small ceramic finger back and
forth. The finger rotates a ceramic ring, thus creating
motion through friction. The motors are adapted
from versions originally used in vacuum environments
for semiconductor manufacturing. This involved
converting stainless-steel parts to ceramic
and coming up with fully ceramic bearings.
“The motor is putting pressure into the work
surface. That means you need a certain amount
of stiffness in the structure it works against,” says
Feinstein. “We normally need a stiffness of about
40 N/micron. But the robot’s stiffness was low because
of the plastic and ceramic bearings. We had
to collaborate closely with designers to make sure
we didn’t cause too much wear or noise despite
compromises on stiffness.”
The PWM signals driving the motors could also
potentially interfere with MRI signals, so Nanomotion
built in a tunable filter that shifts the motor
drive pulse frequency out of harm’s way.
Make Contact
Nanomotion Ltd.,
(800) 821-6266,
nanomotion.com
MacDonald, Dettwiler, and
Associates Ltd.,
tinyurl.com/23whp8
Univ. of Calgary
neuroArm video
and information,
tinyurl.com/ywkl67
Overview of PZT motor
technologies and applications,
tinyurl.com/yuusyt
tinyurl.com/2gk7td
tinyurl.com/yrxc96