DYANA - FOR 3 DIMENSIONAL ANALYSIS OF HUMAN MOTION

  • J.P. Baudin
  • P. Gervais

Abstract

The study of the dynamics of human motion has, until recently, been limited to research in two dimensions. Although three dimensional analyses are more common today, they are generally limited to kinematic evaluations with few studies examining the kinetics of human movement. A complete understanding of the biomechanics of human motion requires an examination of the forces and torques driving the movement. The purpose of this research was to develop a computer program capable of doing a complete dynamic analysis of three dimensional motion of the entire human body while performing aerial skills. A 14 segment, rigid link model, with all joints having three rotational degrees of freedom, was used to represent the human body. Body segment parameters were calculated using methods found in biomechanics literature. Two cameras were used to record the airborne phase of tuck jumps, split jumps and straddle jumps performed by two subjects in a calibrated space. The cinematographical records from the two cameras were digitized and then spatial coordinates of all segment endpoints were calculated using the Direct Linear Transform (DLT) technique. The orientation in space for each segment with respect to the inertial frame was defined by a using the xyz-convention of Euler angles. DyAna, a computer program written in 'C', was developed to do three dimensional dynamic analysis of the different jumps. Linear and angular kinematics were calculated for all segments of the body using central difference and finite difference techniques respectively. An inverse dynamics approach based on the Newton-Euler equations of motion was used to calculate the net forces and torques acting at the joints. The program produced good results for linear and angular kinematics and kinetics for the skills studied. As no similar three dimensional studies were found in the literature, the maximum force and torque values calculated for the tested movements were found to be reasonable when compared with two dimensional studies. In geneml, the computer program DyAna was found to work well for doing dynamic analysis of complete human movement for the airborne motions studied. Its best application in the field of biomechanics would be for the study of human motion outside of the lab setting, such as in sporting events when subject preparation is not possible.