Hexapod Structures in Surgical Applications Presented by

1
Hexapod Structures in Surgical Applications

• Presented by
• Sanjay Shirke
• Muhammad Umer

2
The Hexapod - A Brief History of Design

• 1800s Mathematician Augustine Cauchy studies
  rigidity of polygons
• 1947 Dr. Eric Gough applies the parallel
  kinematic platform to a tire testing machine
  developed working under Dunlop.
• 1962 Klaus Cappel develops vibration equipment
  for Franklin Institute.
• 1965 Stewart platform developed for aircraft
  simulation.
• 1995 Frauhofer Institute in Stuttgart, Germany
  approaches Physik Instrumente to develop the
  surgical robot.

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The Hexapod - A Brief History of Design
(a)
(b)
Fig.1. 1949-2000 (a)The original Dunlop tire
testing machine invented by Eric Gough, (b) The
modern tire testing machine.
4
The Hexapod - A Brief History of Design
(a)
(b)
Fig.2. 1965 -1970 (a)The original Stewart
Platform for aircraft simulation, (b) later
incorporating the design of an octahedral hexapod.
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The Hexapod - A Brief History of Design
Fig.3. 6 DOF motion achieved through 6 strut
linear actuators. The resulting rapid, submicron
multi-axis translation and rotation makes the
hexapod ideal for precision surgical applications.
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The Hexapod - A Brief History of Design
Universal Joints - offer 2 rotational DoF
Linear Hydraulic Actuators - offer 2 DoF 1
translation and 1 rotation
Source Marks Standard Handbook for Mechanical
Engineers
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Hexapods Engineering and Kinematic Principles

• Mobility The Kutzbach Criterion
• n 12 (struts) 1(base) 1(platform) 14
• c 3 x 6 x 4 72
• M 6(14 1) 72 6 DoF

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Hexapods Engineering and Kinematic Principles

• Range of Motion and Resolution

Fig 4. The Physik Instrumente M-800.11
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Hexapods Engineering and Kinematic Principles

• Design Criteria
• Minimize mass and inertia for maximum speed and
  acceleration.
• Strut Operation linear hydraulic actuators
• Joint Design Universal or Ball and Socket
• Integrity tested with CAD, FEA, and laser
  vibrometery tools.

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Is the Hexapod really worth it?

• advantages
• Complete range of motion.
• High precision and accuracy
• Computer visualization tools
• High stiffness
• High load/weight ratio

• limitations
• Friction
• Length of struts
• Dynamic thermal growth
• Calibration

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Development of Surgical Applications

• Hexapod vs. Nonapod
• Extra legs contain redundant sensors
• Insures against failure of standard measuring
  system
• Reliability increase is of the essence

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The future of Parallel Kinematics

• Minimize Friction, hysteresis, and backlash
• Improve material composition to limit thermal
  growth
• Actuators A future in the voice coil?
• Currently, applications are limited to endoscopy.
• Incorporate use of scissors, forceps, balloon
  catheters and coagulation probes.
• Endorse the use of a cockpit to create a virtual
  surgery environment
• Expand to the fields of orthopedics,
  ear/nose/throat surgery, and ophthalmology.

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Bibliography and References

• Avallone, E.A., Baumeister III, T., Marks
  Standard Handbook for Mechanical Engineers 10th
  Edition, McGraw-Hill, New York, 1996
• Hale, Layon C., Principles and Techniques for
  Designing Precsion Machines, UCRL-LR-133066,
  Lawrence Livermore National Laboratory, 1999.
• Smith, S.T., Chetwynd, D.G., Foundations of
  Ultraprecision Mechanism Design, Gordon and
  Breach Science Publishers, Switzerland, 1992.
• Low-Inertia Parallel-Kinematics Systems for
  Submicron Alignment and Handling
  (http//www.parallemic.org/Reviews/Review012.html)
  
• Why Hexapods and Parallel Kinematics?
  (http//www.hexapods.net/hexapod.htm)

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Bibliography and References

• Six DOF Hexapod Challenge of Design and
  Innovation (http//biotsavart.tripod.com/hexapod.
  htm)
• Surgeon Navigates from Operating Cockpit
  (http//www.hoise.com/vmw/articles/LV-VM-05-98-17.
  html)
• History of the Universal Joint
  (http//www.driveshafts.com/u-joint.html)
• M-850 Hexapod 6-Axis Parallel Kinematics Robot
  (http//www.physikinstrumente.com/micropositioning
  systems/8_4.html)