Articulated Body Dynamics Preview

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Articulated Body Dynamics(Preview)

• Chris Oates
• 3/15/2004

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Background

• Most methods come from field of robotics
• Expands on articulated kinematics, IK
• Forward Given a set of forces and torques on the
  joints, calculate accelerations
• Inverse Given an end effector trajectory,
  calculate joint forces and torques
• Calculation of Inertia Matrix Mapping from joint
  forces to accelerations

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Six Doff

• Easiest to focus on canonical case, the 6-DoF
  robot arm
• This example has 6 1-DoF rotational joints, but
  other configurations possible
• (Ill try to find a photo of a real robot arm)

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Methods

• Recursive Newton-Euler Alrogithm
• Composite-Rigid-Body Algorithm
• Articulated-Body Algorithm

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Project Implementation

• Try to solve the Wheres my Elbow? problem in
  our VR work
• Human arm can be simulated like a robot arm
• Use dynamics to give more accurate solution than
  just IK

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Ideas

• Use Newton-Euler method for inverse dynamic
  calculation
• Closed-form solution exists, but is very
  complicated
• Not sure yet how to model inertia tensor
• Start with a simple desktop app to see how
  equations work, then put into the VR code if time