Biomechanical Modeling and Analysis of Human Motion

1. Biomechanical Modeling and Analysis of Human Motion Cole, Joshua Knapp, Austen University of Colorado at Colorado Springs, Department of Mechanical Engineering Advisor: Prof. Steve Tragesser

2. The Objective Create a low cost, non-invasive, portable system for analysis of the internal forces and torques required for human motion

3. Video Capture Kodak PlaySport Resolution: 720 X 1280 Frame Rate: 60 fps Image Processing with MATLAB • Manually input initial marker positions • Filter all colors but green/blue for each frame • Search based on previous centroid location • Two colors distinguish between markers • Output Cartesian Coordinates

4. Dynamic Modeling • Modeled body as series of rigid links • Convert video capture output to angular position • Two methods of analysis

5. Point Mass Analysis • Compute position, velocity, and acceleration of center of mass (CoM) of the three – link model • Calculate horizontal and vertical components of ground reaction force • Calculated using Newton’s 2nd Law for CoM

6. Three – Link Analysis Application of Newton’s 2nd Law and Euler’s Law to attain 9 equation’s of motion (EOM’s) • Three EOM’s per link • 2 EOM’s through • 1 EOM through

7. Three – Link Analysis Equations of Motion:

8. Three – Link Analysis

9. Results and Validation Point Mass Analysis • GRFy vs. Experimental Data from Force Plate • Force Plate = Validation of dynamic analysis • GRFx << GRFy which is the expected outcome • Data from 0.0 to ~0.2 seconds is invalid due to filtering of video capture data • Squat performed after 0.2 sec which allows invalid data to be neglected

10. Results and Validation Three-Link Analysis: • GRFy vs. Experimental Data from Force Plate • GRFy is less accurate with this model than point mass model • GRFx increases to a large magnitude which is not correct outcome • Computations with three-link model more sensitive to measurement errors than point mass analysis

11. Results and Validation Three – Link Analysis: • Figure, top to bottom: • Calculated horizontal component of internal knee force • Calculated vertical component of internal knee force • Calculated horizontal component of internal hip force • Calculated vertical component of internal hip force • Amplitudes appear to be within a realistic range

12. Results and Validation Three – Link Analysis: • Ankle, knee, and hip torques • Result of subject’s muscle actuation • Results qualitatively match expected torque behavior • Values not consistent with results in literature Figure 6: Three-Link Calculated Internal Torques

13. Conclusions and Recommendations • Partially demonstrated feasibility of system • GRF more accurate than internal forces and torques • Sources of error • Markers • Clothing Color • Approximations • Frame rate/camera resolution

14. Future Research and Limitations • Long-term goal: Analyze broad range of human motion and impact of such motion • Possible through calculation of internal forces and torques • Examples of human motion which could be analyzed: • Prosthetic patient gait analysis • Sports performance analysis • Low-gravity analysis • Three-dimensional video capture system • Multi-link model with an arbitrary number of links • Progress EOM’s to allow analysis where feet leave contact with ground

15. Thank you We appreciate you taking your time to listen • Questions/comments/concerns?