DXF HAND


One of the most troublesome aspects of robotic or cybernetic manipulation
system development has been the jitter associated with servo motors. By contrast,
the contraction associated with a conformational change in the nickel-titanium muscle wire
does not suffer from this problem. A fasciculating pulse across a low voltage
switch can produce a smooth contraction of the wire across a fairly wide ambient temperature
range. By varying the rate of the pulse at the beginning and/or end of the contraction
a wide range of contraction rates and force potentials can be achieved. The control
of the switches is performed either directly or remotely (IP) using the object
oriented programming language Python and a parallel port Crydom low voltage switch bank.

In developing a Flexinol (muscle wire) manipulator which can be
controlled remotely or function autonomously with Para-biotic neural constructs
we are using the programming language Python. To accomplish this it was necessary
to evaluate the possibility of using bio-forms (anatomical models based on
three dimensional scans of biological structures. The scanned images
are compiled into 3-Dimensional DXF files. The DXF file formats and 3DS files
contain information relating to these three dimensional objects.

The data for constructing the DXF files for the human hand is based on two sources.
The first is a spiral CT image of a human
hand scanned at a thickness of 0.65 mm. The images are imported into the
program Slicer-Dicer in order to 1) separate out the individual bones of the hand
for reconstruction and 2) to save the isolated bone in DXF file format.
Following this the dxf file is imported into trueSpace modeling program for surface
smoothing, orientation and evaluation of surface reconstruction anomalies.
The second sorce of 3D information for the DXF files is obtained from a 4th
Axis Rotational 3D scanner (grant supported) for a Roland MDX15 Automated
milling/scanning platform.
The dxf file object is saved in the reference database and then is subtracted from
a volume to create a void model of the bone. The void model is then oriented and
is then printed to the Roland CNC milling machine. The resulting plastic model can be
used to create an RTV silicone (Tin-Sil 70/60) rubber mold for casting either
plastic or low melting point metal parts corresponding to the bone.

While developing this process the joint itself has been modeled and optimized for
tele-robotic applications (see Proto-Lab joint). The pseudo-bones and joint cowling
have been modeled using the same approach and can be "fused" in trueSpace with the
actual scanned human hand bone dxf files to produce a hybrid pseudo joint- scanned bone object.





Reference materials on The Human Hand: The bones of the human hand are divided into three groups: 1) Carpal
2) metacarpal and 3) phalangeal (hand) Detailed views are available at the Visible Human server.

The initial dxf files for the Proto-joint are provided below:

DXF: Simplified endoskeletal bone segment


DXF: Proto-Joint with limited range of motion


Images of prototype Hamilton-Joints:









Anatomy of Hand



A. Skelton
B. Muscles 

A.  Skelton of the hand is subdivided into-
	1.	Carpal bones or wrist bones
	2.	Meta carpal bones of palm
	3.	Phalanges or bones of digits

Carpal bones: are eight in number and arranged in proximal and distal 
rows - 4 in each.
  
Metacarpal Bones:
These are five in number, consisting of body, base and head. Each extends 
from carpal bone to proximal phalanx of the respective finger. The bone of 
metacarpal articulates proximally with the carpal and on each side with the 
adjacent metacarpal bones except  the base of first metacarpal which does not 
articulate with second,  Head articulates with proximal phalanx on each finger. 
On each side of head is a tubercle between the tubercles  on the palmer side a 
hollow fossa for the attachment of collateral ligament of metacapophalangeal 
joint.

Phalanges of hand:
 are 14 in number, 3 for each finger and two for thumb. All phalanges contain 
 three bones  proximal. Middle and distal except for  thumb these are 
  proximal and distal.  Each phalanx has 3 parts; base, body and head.
B. Muscles of the hand are subdivided into 3 groups
1)	Muscles of the thumb.
2)	Muscles of the little finger.
3)	 Muscles of the palm. 


Thumb:
1. Abductor Pollicis Bevis - abducts the thumb at carpometacarpal and 
metacarpophalangeal joint.
2. Oppenens Pollicis- abducts , flexes and medially rotate the first 
metacarpal bone.  This is opposition, occurs primarily at 
carpametacarpal joint.
3. Flexor Pollicis Brevis- It flexes the proximal phalanx at the 
metacarpophalangeal joint and indirectly rotate the metacarpal bone of the 
thumb at carpometacarpal joint.
4. Adductor pollicis- adducts the thumb

Little Finger
1.	Palmaris Brevis
2.	Abductor digiti minimi - abducts the littlr finger away from ring finger
3.	Flexor digiti minimi - Flexes little finger at metacarpophalangeal joint
4.	opponens digiti mimnimi - It abducts, flexes and laterally rotates the 
fifth meracarpal

Intermediate muscles:
1.	Lumbrical muscles are four small  fascicul are associated 
with tendons of the flexor digitorum profundus.  Each lumbrical muscle flexes 
the proximal phalanx at the corresponding metacarpophalangeal joints and extends 
the two distal phalanges at the interphalangeal joints.
Interosseous muscles occupy the spaces between metacarpal bones,  
and are divided into two sets- dorsal and palmer.  Dorasl Interossei  
abduct the fingers from the imaginary line drawn longitudinally through the 
axis of the middle finger and palmer Interossei adducts towards the imaginary 
line  They also flex the fingers at metacarpophalngeal joint and extend the two 
distal phalanges at interphalangeal joint.

Flexion of fingers in grasping an object is performed 
by Flexor digitorum superficilis and profundus.








Reference for Anatomical Information:

Gray's Anatomy of the Human Body - Classic Edition 1918 Bartleby online



Palmar aspect



Dorsal Aspect


 
First set of Human Hand bones (Right side) received for 

computer modeling in Jan 2007

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