Download Human Jaw Motion Simulator

Human Jaw Motion Simulator
Department of Mechanical & Industrial Engineering
Northeastern University
Boston, MA 02115
April 17, 2007
By:
B. Galer
N. Hockenberry
J. Maloof
M. Monte-Lowrey
K. O’Donnell
Advisor and Sponsor:
Prof. Sinan Muftu
Outline
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Motivation and Goals
Project Stages
Important Skull Components
Muscles
System Analysis and Control Development
Design Details
Results and Conclusions
Motivation
• Motivation
– Over 10 million Americans are affected by TMJ disorders
– 2 times as many woman as men suffer from TMJ disorders
– Symptoms range from jaw click to limited movement, lock jaw,
and pain
• Purpose
– Provide resource for analyzing the TMJ to allow for treatment of
TMJ disorders
– To test prosthetics
Overall Project Goals
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Create physical model of a skull
Simulate jaw motions
LabVIEW interface
Virtual Matlab analysis
Stage Goals
• Stage I
– Initial Setup and Jaw Closing
• Stage II
– Jaw Opening (including opening to closing transition)
• Stage III
– Jaw Clenching and Disc Adaptation (disc must be capable of
multiple forms of motion)
• Stage IV
– Lateral Jaw Motion/ Chewing (realistic disc simulation must be
accomplished by this stage).
Background
Important Components of the Skull
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Maxilla
Mandible
Muscles
Ligaments
Temporomandibular Joint
Articular disc
Muscles of Closing and Max Forces
Temporal
120 lbs
Lateral pterygoid
34 lbs
Masseter
93 lbs
Muscle Assumptions and
Constraints
• Muscles
– Can only contract
– Are symmetrical for either side of jaw
– Act in a single plane
– Will be simulated as acting as a single vector
through the center of the muscle.
Muscle attachments
• Koolstra Study 1992
– Attachment points: On Jaw
– Anchor points: On Skull
– Zero point based on contact point
Muscle
Masseter
Lateral
Pterygoid
Temporal
x (m)
y (m)
Attachment
0.0204
-0.0605
Anchor
0.0338
0.0043
Attachment
0.0032
-0.0044
Anchor
0.0239
0.0064
Attachment
0.0363
-0.018
Anchor
0.0167
0.0463
System Analysis and Control
Development
Motion of the Human Jaw
• What motions are involved in closing the jaw?
• What assumptions must be made?
• How can the motion be controlled?
Assumptions
• Compressive Force on disc is constant
• Disc moves with mandible
• Mandible Contact Point
oTaken while in fully closed position
oAlways perpendicular to articulating surface
Results of Assumptions
• The Disc will be Left out of Model
• The Normal Force from the
Articulating Surface Acts Directly on
Contact Point
Physical Constraints of Mandible
• Constrained to single path of travel
• Mapped profile of the articulating surface
• Orientation of lower jaw found at
predefined target positions
System Control
Anatomical
Constraints
Controllability
Available
Knowledge
Control
Knowledge
Physiologically
Realistic
Value
5
4
3
2
1
Total
Force
1
2
1
1
2
20
Position
2
1
2
2
1
25
Force
Position
Statically Indeterminate
Anatomically Constrained
Controllable with Tension or Slack Method
Controllable with Length Adjustments
Definitive Research not Available
Information is Readily Available
Control System Requires More Research
Control System is Common and Simple
Physiologically Accurate
Not Physiologically Accurate
Positional Control
Anchor Points
• Motion Tracking
•Constrained Orientations
•Varying Muscle lengths
Articulating Surface
• Matlab Program
•Variable surface profiles
•Variable tracking locations
Attachments and
Predicted Paths
•Creates positional output
• Control Method
•Control Muscle Lengths
Mandible
Design Details
The Design
Frame
Muscle Decision Matrix
Total
Control
Precision
Accuracy
Complexity
Resources
Safety
Cost
5
4
3
3
3
2
2
High End
Motor
161
10
10
10
3
6
6
1
Standard
Motor
164
8
8
7
7
8
6
7
Pneumatic
78
4
3
4
3
3
3
5
Hydraulic
63
5
3
4
1
1
1
3
Air Muscle
68
4
2
3
2
3
3
5
Muscle
Wire
118
3
6
5
8
6
5
6
Polymer
118
3
6
5
8
6
5
6
Brushless Servo Motors
• High precision and
accuracy
• Position control requires
feedback
• AKM33E- Danaher Motion
• 2.2NM torque
• Built in encoder
Controlling the Motors
• NI PCI-7344 four axis servo/step motion
controller
• MDM-2100 integrated three axis servo drive with
power supply
LabVIEW Interface
• Can be run by any user
• Allow easy future
changes to project
• Feedback loop built into
program
Pulley System
• Pulleys used to
increase torque
• Keeps motor
cost low
• Allows for project
expansion
Wire Attachments and Guides
• Can only pull like
muscles
• Adjustable tension
Skull and Lubrication
• Mimics Program
– Convert CT scan to 3-D model
• SLA model to rubber-molded model
• Attachment points tested for bending
• Lubrication on joint
Lubricated
Surface
A
Surface
B
Coefficient
of Friction
No
Teflon
Delrin
0.45
No
Teflon
Teflon
0.5
No
Delrin
Delrin
0.45
Yes
Teflon
Delrin
0.08
Yes
Teflon
Teflon
0.06
Yes
Delrin
Delrin
0.1
Results and Conclusion
Virtual Analysis
Physical Analysis
Results
Virtual
• Jaw Appeared to Open Improperly
• Negative Force Values
Physical
• Separation at joint
Conclusions
Initial Assumptions Were Incorrect
– Mandible Does Not Stay Perpendicular to the
Articulating Surface
– Muscles Can Only Contract, Whereas Results
Suggested Expansion
• Muscle Choices May be Incorrect or Over
Simplified
Updated Assumptions
Running the System
Special Thanks To
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Prof. Sinan Muftu
Prof. Greg Kowalski
Prof. Rifat Sipahi
Jeff Doughty
Jon Doughty
US Surgical
Brian Weinberg & Prof. Constantinos
Mavroidis’ lab
Questions?