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

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

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

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

Point Mass Analysis Position Data Outputted Video Capture System Finite Difference Method F=ma to attain GRFx & GRFy 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 2 nd Law for CoM

Three – Link Analysis

Equations of Motion:

Three – Link Analysis Angular Position, Velocity, and Acceleration EOM’s Internal Forces and Torques

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

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

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

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

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

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

Thank you We appreciate you taking your time to listen – Questions/comments/concerns?