RealTime Inverse Kinematics Techniques for Anthropomorphic Limb

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Real-Time Inverse Kinematics Techniques for
Anthropomorphic Limb

• Deepak Tonali, Ambarish Goswami, and Norman I.
  Badler
• Computer and Information Science Department,
  University of Pennsylvania
• Graphical Models 62, Sept. 2000

Presented by Che-Jen Chen Intelligent Media
Laboratory Department of Computer Science,
National Chengchi University fake3d_at_imlab.cs.nccu.
edu.tw
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Outline

• Introduction
• Traditional Inverse Kinematics Algorithms
• An Analytical Algorithm For A 7-DOF Limb
• Conclusions And Future Works

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Introduction

• IK Plays a Key Role in Computer Animation and
  Simulation of Articulated Figures.
• Making a Set of Joint Easy to Control
• Finding Joint Angles From Sensors of Live Subject
• Analyzing Reachable Objects in Virtual Workspace

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Problems That Using Robotics IK Algorithms in
Computer Animation

• Only Involve Position and Orientation Constraints
  of Terminal Segments
• Few Robots Have More Than Six Joints
• Joints Are Independent and Joint Limits Are
  Simple Linear Constraints
• In General, Errors Are Less Critical in CG
  Applications

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Features of This Approach

• Include Aiming and Partial Orientation
  Constraints
• Focus on Analytical Methods
• Extra Degree of Freedom Handling
• Real Time
• 7 DOF - Human Arm
• Dynamic Simulating, Realistic Trajectory
  Generating

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Traditional Inverse Kinematics Algorithms

• Newton-Raphson Methods
• Resolved Motion Rate Control
• Control-theory-based Methods
• Optimization Approaches
• Other IK Techniques and HAL Chains

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Goals in Jack / Quality Criteria

• Goals in Jack
• Position, Orientation, Position Orientation,
  Aiming At and Plane Goals
• IK Algorithm Quality Criteria
• Efficiency, Reliability, Completeness, Stability
  and Generality

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An Analytical Algorithm For A 7-DOF Limb
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Forward Inverse Kinematics
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Solving for ?4

• Low of Cosines
• In This Approach
• From S2 to S1
• VS2S1 . VS2S1 (VS2S1)2
• acos(?4) bsin(?4) C

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Characterizing Extra Degree of Freedom
arbitrary axis (corresponding to F0)
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Solving for R1 R2
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Joint limits
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Partial Orientation Constraints
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Aiming Problems
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Result (1)
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Result (2)
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Conclusions And Future Works

• A Hybrid Analytical Numerical IK Algorithm
• Reduce Complexity by Decomposing the IK Problem
• Repeatability
• Solution Existence Determination
• Redundant Handling

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Conclusions And Future Works (Cont.)

• From Arms Legs to Spine Model and to Entire
  Body
• Decouples a Complex IK Problem Into Simpler Ones
• From Goal Reachable Determination to Balance
  Control Collision Avoidance Constraints

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Q AThank You!

• Presented by Che-Jen Chen
• Intelligent Media Laboratory
• Department of Computer Science, National Chengchi
  University
• fake3d_at_imlab.cs.nccu.edu.tw