Virtual Prototyping and Hardware-in-the-Loop Testing for Musculoskeletal System Analysis

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Virtual Prototyping and Hardware-in-the-Loop
Testing for Musculoskeletal System Analysis

• Michael J. Del Signore
• Venkat Krovi and Frank Mendel

Mechanical and Aerospace Engineering
Anatomical Sciences SUNY Buffalo
E-mail mjd24_at_eng.buffalo.edu Web
mechatronics.eng.buffalo.edu/research/sabertooth/
ICMA 2005 Niagara Falls, Ontario,
Canada International Conference on Mechatronics
and Automation
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Goals
Development of tools for biological hypothesis
testing leveraging research methodologies that
have revolutionized the mechatronics domain.
Outline

• Introduction
• Case Study Description
• Modeling Framework
• Implementation Framework
• Conclusion

ICMA 2005 Niagara Falls, Ontario,
Canada International Conference on Mechatronics
and Automation
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Introduction Case Study Modeling
Implementation Conclusion

• Virtual Prototyping (VP) and Hardware-in-the-Loop
  Testing (HIL)
• Used extensively in mechatronics and many other
  engineering fields.
• Revolutionized design, analysis, and validation
  processes.

• Application and integration into other
  professional arenas.
• Similar advancements and benefits.
• Biological sciences could benefit from rapid
  hypothesis testing tools

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Introduction Case Study Modeling
Implementation Conclusion

• Virtual Prototyping
• Simulation and refinement of suitable models of a
  product in software.
• Compute/calculate kinematic, dynamic and
  FEA-based responses.
• Visualized in a 3D interactive graphical virtual
  environment.

Movie2
Movie1
Video examples taken courtesy of
MSC.VisualNastran4D, Tutorials
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Introduction Case Study Modeling
Implementation Conclusion
Hardware-in-the-Loop Testing (HIL) Simulation in
which parts (or all) of the virtual model have
been replaced by the actual physical model.
Movie3
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Introduction Case Study Modeling
Implementation Conclusion
Adaptation and implementation of a VP/ HIL
framework into one of the candidate biological
sciences arenas
Musculoskeletal System Analysis

• Three Critical Steps
• Model creation with adequate fidelity.
• Analysis of various actions/ behaviors.
• Iterative testing for refining hypotheses.

Powerful Tool
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Introduction Case Study Modeling
Implementation Questions
Challenges

• Unlike traditional engineering systems,
  musculoskeletal systems inherently possess
  considerable irregularities and redundancies.

Irregularities
Redundancies

• Complex Asymmetric Geometric Shapes (i.e.
  muscle, bone).
• Each specimen is unique.
• Dealing with (trying to simulate) living tissue.

• Multiple Muscles More actuators than degrees
  of freedom.
• Infinite set of actuator (muscle) forces can
  produce the same end-effector force.

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Introduction Case Study Modeling
Implementation Conclusion
Challenges (contd)

• These characteristics cannot be readily handled
  by current computational tools.
• Preliminary simulation performed using existing
  tools met with limitations due the softwares
  inability to handle redundancy.

Muscles ? Linear Actuators
Skull/ Mandible Interaction ? Revolute Joint
User-specified input to the system ? External
forces

• This provides the motivation for development of a
  low-order computationally tractable model based
  on screw-theoretic methods.

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Introduction Case Study Modeling
Implementation Conclusion

• Goals of Case Study
• Musculoskeletal modeling and analysis of the
  skull/ mandible structure of an extinct
  Sabertooth cat.
• Development of a low-order screw theoretic model.
• Underlying articulated structure and superimposed
  musculature can be modeled as a redundantly
  actuated parallel mechanism.

• Estimate the muscle forces associated with an
  applied/ desired bite force.
• Estimate the maximal bite force of the animal.

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Introduction Case Study Modeling
Implementation Conclusion

• Screw Theoretic Model
• A low-resolution computational model of the
  skull/ mandible musculoskeletal system of the
  sabertooth cat.
• The motions (twists) of the system as well as the
  external bite force (wrench) can be expressed in
  screw coordinates.

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Introduction Case Study Modeling
Implementation Conclusion

• Screw Theoretic Model (contd)
• Each muscle is modeled as a Revolute-Prismatic-Rev
  olute (RPR) serial chain manipulator with an
  actuated prismatic joint.
• An external (desired bite) force is applied to
  the system.
• Need to calculate the actuator (muscle) forces
  needed to produce the external bite force.

RPR Serial Chain
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Introduction Case Study Modeling
Implementation Conclusion

• Find the end-effector twist due to the screws
  generated by each joint in the ith RPR chain
  (muscle).

• Find the selectively non-reciprocal screws (SNRS)
  associated with the active-joint of every muscle
  (Wk,i).

• Collect the SNRS for all active joints of each
  chain to obtain the system equation.

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Introduction Case Study Modeling
Implementation Conclusion

• System Equilibrium Equation

• fP Particular Solution
• Equilibrating force field
• Least-squares solution
• fH Homogeneous Solution
• Interaction force field
• Used to ensure that all muscle forces are
  positive.

• Pseudo-inverse based solution

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Introduction Case Study Modeling
Implementation Conclusion

• Implementation Framework
• Merger of various software and hardware elements

• Perform iterative and repeated what-if studies
  for bite and muscle force estimation.

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Introduction Case Study Modeling
Implementation Conclusion
GUI Graphical User Interface

• Analysis is performed over a range of muscle
  insertion/ origin points and jaw gapes.

Movie4
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Introduction Case Study Modeling
Implementation Conclusion

• Hardware-in-the-Loop Test Bed
• The HIL test-bed is currently in development.
• The developed test-bed is capable of being
  adjusted to allow bite-testing of a wide variety
  of specimens.
• Geometric data from the CT scans is used to
  develop castings of the dentition (upper and
  lower jaws).

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Introduction Case Study Modeling
Implementation Conclusion

• Muscles will be approximated by tensioned cables
  and actuator forces in these cables are
  determined from the simulation of the virtual
  model.
• A MATLAB/ Simulink/ Real-Time-Workshop framework
  will be used to facilitate rapid conversion into
  a real-time executable for execution on the
  deployment computer.

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Introduction Case Study Modeling
Implementation Conclusion

• Overview of a VP/ HIL framework for
  musculoskeletal system analysis.
• Physical test-bed in development
• Existing tools proved inadequate and a low-order
  screw-theoretic model was developed.
• Overall framework was presented in the context of
  a Case Study.
• Bite and muscle force estimation in an extinct
  Sabertooth cat.
• Shows significant promise for speeding up the
  overall analysis process.

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Thank You
Questions?