|M.Sc Student||Eran Langzam|
|Subject||Impact Loading Attenuation in Landing from Vertical Falls|
|Department||Department of Biomedical Engineering||Supervisor||Professor Emeritus Mizrahi Joseph|
During its long-term usage, the human body is daily
subjected to different set of loads; among them are the transient forces, which
are characterized by large force transients over short periods. These forces,
referred to in the literature as “Impact”, can cause short and long term
damages. Impact on the human body was widely studied and its characterization
is being continuously updated. In addition to the quantitative characterization
of the ‘force wave’ attenuation along the body and its effects, there are
continuous efforts to simulate the phenomena using dynamical models that
provide a better insight and serve as a reliable research tool. Existing models
of the human body for impact during vertical fall have been incomplete and have
generally included “Lumped”, “Rigid-bodies”, and “Wobble-mass” models.
The goal of this research was to set a mathematical model, which well reflects the impact stage, of a human drop. Since this model was defined up to a parametric level, a reliable parameter estimation procedure was also required. The model was based on both simulated and in-vivo experimental data.
Two 2D biomechanical models were examined: a 5-segment
“rigid-body” model, and a comprehensive 8-segments “wobble-mass” model. The
segments’ mass-inertia properties were evaluated using anthropometrics tables
and analytical modeling methods.
The study included three “blocks”, corresponding to the different levels of the modeling stages: “Block-one”’ used a simulated (=”synthesized”) database to define and explore the basic analysis tools regarding parameter estimation and optimization procedure (e.g.: optimization algorithm, functional structure etc.). “Block-two” applied the general configuration of “block-one” to adjust the algorithm to the specific impact of the fall problem (e.g.: what model best represents the impact, etc.). ”Block-three” provided an explanation to some of “block-two” inaccuracies, and improved the algorithm to better perform. The final algorithm was tested on 27 files of six subjects’ experiments, indicating a consistent behavior, and was able to well replicate the three experimental measurements of the head acceleration, shank acceleration, and vertical ground reaction forces (VGRF).
The present model provides an established “wobble-mass” segmentation, and underlines the benefits to the impact phenomenon. The research also brings a reliable optimization algorithm to solve the unknown impedance parameters, backed by methodological examinations rather then previously used operational “finger rules”.
The research results can be implemented on impact studies, and its tools can be used in other fields of engineering.