Generating physically realistic kinematic and dynamic models from small data sets: An application for sit-to-stand actions

Kinematic and dynamic models are used to create simplified, yet accurate representations of reality. In application to biological systems, there is often a choice on what level of complexity is appropriate for the model. This paper introduces a structured method for obtaining an accurate model that can represent the sit-to-stand motion and reproduce the associated contact forces in the standing phase. These models are generated from small datasets, just five measured sit-to-stand actions, and result in simple, physically realisable dynamic models. The assumptions made apriori on the model are minimal, with the number of segments, axes of rotation, marker allocation and location, and dynamic model all determined from this small dataset. From this initial analysis, the use of a triple pendulum with a simple point mass at the centre of the torso was found to be representative. Through the generation of these simple, repeatable models, this work aims to develop a modelling framework that is suitable for the study of biological systems and clinical use.