Integration of Electromagnetic and Optical Motion Tracking Devices for Capturing Human Motion Data Woojin Park

For human motion studies, which are to be used for either dynamic biomechanical analyses or development of human motion simulation models, it is important to establish an empirical motion database derived from efficient measurement and well-standardized data processing methodologies. This paper describes the motion recording and data processing system developed for modeling seated reach motions at the University of Michigan's HUMOSIM Laboratory. Both electromagnetic (Flock of Birds) and optical (Qualysis) motion capture systems are being used simultaneously to record the motion data. Using both types of devices provides a robust means to record human motion, but each has different limitations and advantages. The amount of kinematic information (DOFs), external sources of noise, shadowing, off-line marker identification/tracking time, and setup cost are key differences. Although there are reports on the use of each of the devices when used separately in studying human movement, to our knowledge no research has been reported where-in both devices were simultaneously used. To meet our research goals, we believed there were advantages by combining the two devices. A kinematic linkage model, which consists of eight links and twenty-two degrees-of-freedom was developed to represent a seated operator. A protocol of placing the electromagnetic receivers and optical markers was developed considering both the kinematic linkage definition of a seated operator and the advantages/shortcomings of the two measurement devices. A simulator was built, in which typical industrial and in-vehicle reach activities could be studied. A technique to correct errors in placing the electromagnetic receivers was developed, which uses initial standardized postures. This paper also describes joint center estimation and angle calculation methods using the sophisticated human model and inverse kinematics capabilities of the EAI-Transom Jack software.