Handpiece for Immersion Virtual Laparoscopic Interface (VLI)
This
handpiece offers compatibility with old Immersion VLI devices. It
features a movable fore-finger control that rotates the shaft of the
VLI utilizing the VLIs internal sensors for control feedback.
Additionally a spring-loaded thumb control provides feedback to the
VLIs input system for a variable amount of tool open and close. Like
most of our other tools this piece is precision CNC machined out of
Acetal and Stainless Steel to provide an extreme durability and long
life under continuous use without any device maintentance.
Background Information
Existing
VLI handpieces had several weaknesses. The two biggest flaws were
internal analog processing and hardwired feedback cable. To address
those issues we created a precision tool that uses easily-replaced
cables and a fully digital/optical internal design.
Our Design
Our
goal was to eliminate the issues common to existing VLI handpieces. To
do this we first started our own custom design of the tool body. We
then added our own electronics and optics. Finally we made the
handpiece cabling field-serviceable should cables need to be replaced
from the stresses of continuous use in training environments.
Metal Mechanical Attachment
- The handpieces are attached to the VLI both electrically and
mechanically. Our mechanical attachment is a CNC machined piece for
reliability even under the stress of continuous motion. The visible
portion of the attachment slides over the input shafts of the VLI and
is fixed in place with a recessed set screw. Internally the attachment
mates up precisely with our custom handpiece body to provide a smooth
operating sleeve bearing. At the far internal end of the attachment is
a ribbed wheel that allows the VLI shaft to be rotated with the users
finger.
Stainless Steel Attachments
- Stainless Steel stands up well to the variety of body chemistries and
cleanings these devices are exposed to in a training environment, such
as a medical simulation lab in a training hospital. We try to use
high-quality plastics whenever possible. However, when metal components
are necessary, we use SS to prevent rust and damage from continuous use
and exposure to human contact. These handpieces use SS for the body
screws, shaft attachment, and rotation point pins.
Acetal - Our
Acetal body resists damage from body chemistry, cleaning solvents, and
abuse such as dropping, that are common in resident training
environments. Acetal also has self-lubricating properties that we
utilize for an extremely long service life that is completely
maintenance free. We custom design each tool body for a specific
purpose and precisely CNC machine it from Acetal billet. Sleeve
bearings are integrated directly into our Acetal designs, directly
mating with other Acetal, or Stainless Steel components to create
low-friction, smooth operating, maintenance free points of rotation.
Monocoque-
Using a monocoque design allows us to create a compact tool design that
encloses internal circuitry and acts as a load-bearing and active
structure. The design for these handpieces also precisely places and
focuses the internal optics of the tool for reliable operation over the
lifetime of the handpiece.
Digital Signal Processing
- Other handpieces use analog processing internally, generally through
the use of an analog magnetic sensor fixed to the tool body and a
moving permanent magnet attached to the thumb control. Unfortunately
that design requires user calibration from handpiece to handpiece as
the magnet and sensor may have slight variances from one unit to the
next. To eliminate that problem we process everything digital inside
our handpieces. As the thumb control is actuated it pulses light beams
inside our tools. A signal processor measures the absence and presence
of the light beam reflections and can digitally measure the exact level
of actuation of the thumb trigger. All of our units produce exactly the
same output from one unit to the next.
Glass-Free Optics
- Often glass is a superior material for use in precision optics.
Unfortunately glass is often too fragile for application in medical
simulation. Even glass optics that are protected by a very robust case
eventually experience damage due to the repetitive drops from medical
residents. To prevent this point of failure we use high-quality plastic
and metal optics in our devices. Our beam transceivers and optical
lenses are all plastic. Our optical discs consist of stainless steel or
anodized aluminum with high-resolution alternating transparent and
opaque plastic overlays. These resilient components withstand repeated
high-impact drops without failure.
PWM Output -
The VLI only accepts an analog input from the handpieces. This variable
voltage indicates the level of actuation on the thumb trigger of the
tool. We use a programmable logic device to convert the digital pulses
from the trigger optics into a precision referenced voltage that we
output from our handpieces into the VLI.
Replaceable Cable -
Our handpieces have 3/32" sockets on them, the same as the VLI. We
supply each handpiece with a cable with 3/32" plugs on each end. Unlike
other VLI handpieces that have a cable that is permanently attached to
their internal circuitry, our cables can be easily replaced in the
field, in the unlikely event that they become damaged through repeated
flexing and stresses in the training environment.
Project Summary
Our
VLI handpieces are in continuous use at a variety of government and
medical training institutions. Thanks to the use of high quality
materials and careful design these tools are known for having a
flawless record of operation.
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