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Authors & Affiliations
Tim Sziburis, Susanne Blex, Ioannis Iossifidis
Abstract
The Ruhr Hand Motion Catalog of Human Center-Out Transport Trajectories [1] is a compilation of three-dimensional task-space motion data simultaneously measured by two motion tracking systems. The first one, an optical motion capture system, provided robust reference data. The second recording system consisted of a single state-of-the-art IMU to demonstrate the feasibility of portable applications. The transport object was moved in 3D space from a unified start position to one of nine target positions, equidistantly aligned on a semicircle. Ten trials were performed per target and hand, resulting in 180 trials per participant in total. 31 participants (11 female, 20 male, age 21-78) without known movement disorders took part in the experiment.
Based on those experimental data, we analyze several characteristics of upper-limb trajectories. All data are rotated so that the straight connection of the defined start and target positions composes the y-axis. By doing so, we explore properties which are independent of the directly measured target location for each task and focus on common properties shared between all target movements. Particularly, we investigate how individual or target-dependent differences can still be quantified after rotation. Furthermore, we model the measured movements by means of dynamical systems (extended attractor dynamics). Differences between the transportation movements to different targets would result in varying parameter sets.
The investigated motion characteristics include the symmetry of velocity peaks and the polynomial target dependence of planarity attributes. To compare the diversity of trajectories in time and space, we introduce a novel variability measure for the planarity of hand paths regarding plane angles and path amplitudes within the plane. These aspects can expose differences between trials (intra-subject) and participants (inter-subject), explored in the modelling process and applied as a methodological framework for pathological analysis. For this, further measurements with patients experiencing movement disorders are planned for future examination. The separability can also be evaluated by machine learning of task classification and user identification. This can provide information on the potential of data-driven pathological analysis to extend the model-based approach since the described experiment and study are conducted in the context of developing a portable glove for the diagnosis of movement disorders.