Incorporation of Pressure Insoles into Inverse Dynamic Analysis
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Date
2022-01-27
Authors
Mahmassani, Ahmad
Journal Title
Journal ISSN
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Publisher
University of Waterloo
Abstract
Estimation of body loads during industrial tasks, such as lifting and weight bearing, is central to workplace ergonomics and the study of the safety and risk factors in work techniques. Evaluating those loads requires data collection of body kinematics and the external forces prevailing during the task under evaluation. Current practice calls for kinematic data to be gathered using optical motion capture systems (OMC) and external forces, primarily ground reaction forces (GRFs), to be gathered using force plates. However, this experimental methodology is confined to laboratory settings.
Modern motion capture systems, such as those based on Inertial Measurement Units (IMUs), pave the way to more versatile motion analysis techniques not confined to labs. Inverse dynamics models have been developed based on IMU kinematic data. In order to eliminate the need for force plates and to make the experimental apparatus fully portable, those models estimate GRFs from measured accelerations.
This study aimed to advance the state-of-the-art on IMU-based inverse dynamics analysis by incorporating pressure insoles as the source of the vertical components of the GRFs, with a view to improving the model fidelity while keeping the experimental apparatus portable. Specifically, it enabled the development of a synchronized and automated inverse dynamics model, comprised of an inertial motion capture suite and pressure insoles, that can estimate net joint forces and moments during manual handling activities.
An experiment was designed to examine whether the GRFs measured by the pressure insole can detect and differentiate among various sizes (and weights) of concrete masonry units (CMUs). The instrumented pressure insoles were consistently able to identify three different CMU block weights (8 kg, 16kg, and 24 kg) during various gait patterns (along circular, square, and linear paths). On the other hand, the results were inconclusive in distinguishing between one-handed and two-handed manual handling of CMUs. An improved inverse dynamic model was introduced to calculate the joint loads workers experience during material manual handling based only on measurements by IMU motion capture suits and pressure insoles.
The outcome of this thesis was the development of a weight detection algorithm with a detection accuracy of 89% across all three sizes of CMUS as well as an integrated inverse dynamic model incorporating data collected by IMUs motion suits and pressure insoles.
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Keywords
Biomechanics, Motion Capture, Pressure Insoles, Weight Detection, Kinetic Analysis, Multi-body Dynamics, Gait Analysis, Signal Processing