Concept: "Scalar" is an above-elbow (transhumoral) modular prosthesis design used for rock climbing. The name has two meanings: it can mean someone who scales (climbs) obstacles, but it can also mean a value with magnitude but no direction. In conversations with the climbers I know, they seem to really identify with both meanings. Most rock climbing prostheses currently don’t yet
feature a hand that’s similar in shape to a human hand - that is, they end in hooks, or
wedges that allow you to grip with a single point of pressure. I want to design
a functional piece that would work like an actual hand, with articulating
fingers, as well as grips on the fingers and palm th
at assist with traction
during climbing. I will be drawing inspiration from tattoo designs around
the world, firstly from an artist named Kenji Alucky, whose work I’ve admired
for years. His art is very geometric, and has clean lines and stippling
combined with negative space that creates a visual feeling closely related to sacred
geometry. I’ve also been drawing inspiration from nature to create other visual
elements, such as trees or ferns to cover a portion of the arm and complement
the hard lines of the geometric piece.
at assist with traction
during climbing. I will be drawing inspiration from tattoo designs around
the world, firstly from an artist named Kenji Alucky, whose work I’ve admired
for years. His art is very geometric, and has clean lines and stippling
combined with negative space that creates a visual feeling closely related to sacred
geometry. I’ve also been drawing inspiration from nature to create other visual
elements, such as trees or ferns to cover a portion of the arm and complement
the hard lines of the geometric piece.
Research so far: In my research on prosthetic devices for above-elbow amputees
(and below-elbow, for that matter), I’m finding that arms are much more complex
than legs in terms of musculature and joint function. There are upwards of 30
muscles and at least 18 joints that function together to operate a human arm, and
the end purpose of all that complexity is the fine motor control of the fingers. One of the first challenges I'm tackling is modeling joint articulations that are more flexible in range of motion than
your standard hinge joints. There are above-elbow prosthetic devices that use
only simple hinge joints, but you wouldn’t be able to rock climb very well with
that type of design. I’m taking a lot of artistic liberty with the overall
engineering of my device, and hoping that an engineer would be able to get me
the rest of the way into real-world functionality. My main goal is to create a
beautiful, desirable cosmesis (outer coverage of a prosthesis) that could be
fitted with specific engineered parts later to become a functioning prosthesis,
using the engineering concepts I’ve proposed to fit in the cosmesis. For some
in-depth ideas on ways to structure the joints, I found useful diagrams on the
Johns Hopkins Applied Physics Laboratory website. The lab provides a simple but
detailed visual aid on a sensored above-elbow prosthetic limb that they’ve
designed, with x-ray views that really helped me plan out how I think I’m going
to model the fingers, elbow, and wrist joints.
Here’s what I’m working on, in terms of the various joint types:
elbow - hinge joint
wrist - combination rotating and hinge (ulna and radius twisting)
thumb - ball and socket
palm - hinge halfway into the palm
origin of fingers - hinge in 2 directions at connection to palm
OR full rotation using ball joints
finger middles and ends - hinge only
no naked edges
ghosted
hand detail
Modeling so far: I started by using DupEdge to pull horizontal and vertical curves from a polygonal arm model provided
by Professor Scott. I then Joined the curves, and Rebuilt with a consistent number of points
down the arm and through the fingers, double checking that I still had intersection. I strategically chose “edge loops” from the
original mesh that would become the defining edges and midsections of the component parts of
the prosthesis. I occasionally projected a straight curve onto a finger to get a
smooth, aligned loop to work with, since the mesh of the original model often flows
in a way I didn’t want my curve-based surface to flow. I used SetPt to level out my
horizontal and vertical curves, in order to set up for success with NetworkSrf (or Loft in some cases).
Sweep1, Loft, and NetworkSrf to get my prosthetic "last" components.
Lofted the palm section, but first used TweenCurves to get intermediate cross
sections for a smoother surface, because the original cross sections I pulled
from the polygonal model were not supporting the surface enough. Used a loose Patch to
close off the fingers before creating the structure for the joints. This will likely be temporary for the ends of the fingers. Also used
CutPlane and Trim when Patch surfaces didn’t look very clean. Used
GumballAlignment when the pivot needed to be readjusted to an object. Used
SrfSeam to adjust the seams on my base surfaces so that they’re tucked away
under the arm. This also ensures that if I want to use FlowAlongSrf later, my seam is in a convenient spot. Used NetworkSrf to create the ends of the fingers.
For the elbow joint, I modeled a rounded wheel using circular
curves, Loft, Cap, and FilletEdge to create a joint that interacts with the
lower arm like a traditional hinge joint. I then used BooleanDifference to
remove a portion of the arm pylon to accommodate the elbow wheel, and Trimmed
edges that were too sharp for filleting a solid at first. For the wrist joint, I needed
to create a combination joint that hinged forward and backward, but also
twisted, mimicking the way the radius and ulna rotate around each other to get
that second degree of motion. I drew two rounded rectangle curves, then lofted
them together, capped the ends, and filleted the edges. I created a cutout by
intersecting a sphere with the rounded rectangular piece, then used
BooleanDifference to remove the rounded area. Filleted those edges too. Created
a housing around the round joint that closes the top of the hand and connects
to the ball joint housing by using a combination of Sweep2 and BlendSrf. Had to
use Dir to change the direction of the surface normals on a few objects during
this portion, so that they built correct surfaces.
For the geometric design and organic leaf designs, I will be using
FlowAlongSrf after modeling the details flat on the planar UV representations,
then extruding, filleting edges, etc.
Sources:
DESIGN OF ARTIFICIAL ARMS AND HANDS FOR PROSTHETIC
APPLICATIONS: Richard F. ff. Weir, Ph.D.
Amputee Coalition:
Johns Hopkins Applied Physics Lab: joint information
Kenji Alucky:
No comments:
Post a Comment