A model of the soft tissue artefact rigid component

摘要: When using stereophotogrammetry and skin-markers, the reconstruction of skeletal movement is affected by soft-tissue artefact (STA). This may be described considering a marker–cluster as deformable shape undergoing geometric transformation formed non-rigid (change in size shape) rigid component (translation rotation displacements). A modal decomposition STA, relative to an appropriately identified basis, allows separation these components. study proposes mathematical model STA that embeds only its estimates relevant six mode amplitudes linear functions selected proximal distal joint rotations during analysed task. was successfully calibrated for thigh shank simultaneously recorded pin- skin-marker data running volunteers. The root mean square difference between measured model-estimated 1.1(0.8) mm (median (inter-quartile range) over 3 subjects � 5 trials 33 markers coordinates), it mostly due wobbling not included model. Knee kinematics estimated reference pin-marker data, both raw compensated with STA. compensation decreased inaccuracy on average from 6% 1% flexion/extension, 43% 18% other two rotations, 69% 25% displacements. Thus, proposed provides estimate which can effectively used within optimal bone pose estimators compensation, simulations aimed at their comparative assessments.