University of Iowa Iowa Research Online Theses and Dissertations Fall 2014 Digital human modeling for optimal body armor design Nic Andrew Capdevila University of Iowa Copyright 2014 Nic A. Capdevila This thesis is available at Iowa Research Online: https://ir.uiowa.edu/etd/1435 Recommended Citation Capdevila, Nic Andrew. "Digital human modeling for optimal body armor design." MS (Master of Science) thesis, University of Iowa, 2014. https://doi.org/10.17077/etd.dpr75fbl Follow this and additional works at:https://ir.uiowa.edu/etd Part of theElectrical and Computer Engineering Commons DIGITAL HUMAN MODELING FOR OPTIMAL BODY ARMOR DESIGN by Nic Andrew Capdevila A thesis submitted in partial fulfillment of the requirements for the Master of Science degree in Electrical and Computer Engineering in the Graduate College of The University of Iowa December 2014 Thesis Supervisor: Research Scientist Timothy Marler Copyright by NIC ANDREW CAPDEVILA 2014 All Rights Reserved Graduate College The University of Iowa Iowa City, Iowa CERTIFICATE OF APPROVAL _____________________ MASTER’S THESIS _______________ This is to certify that the Master’s thesis of Nic Andrew Capdevila has been approved by the Examining Committee for the thesis requirement for the Master of Science degree in Electrical and Computer Engineering at the December 2014 graduation. Thesis Committee: ___________________________________ Timothy Marler Thesis Supervisor ___________________________________ Karim Abdel-Malek ___________________________________ Jasbir Arora ___________________________________ Jon Kuhl To my parents, my family, my friends, and all of those who have guided and inspired me along the way. I would not be where I am without you. ii ACKNOWLEDGMENTS The work presented in this thesis, as well as the thesis itself, would not be possible without Dr. Timothy Marler, whose tireless effort, patience, guidance, knowledge, helpfulness, encouragement, understanding, and attitude will act as an inspiration to me always. I cannot thank him enough for being a wonderful teacher and person, and my respect for him knows no bounds. I would like to thank my academic advisor, Karim Abdel-Malek, for his time and support. I would like to thank all of my committee members for their valuable time, as well as their feedback. My deepest gratitude and affection to everyone at the Virtual Soldier Research program, especially Anith Mathai, Kimberly Farrell, Andy Taylor, Rich Degenhardt, and Jake Kersten, for all of their help along the way. Lastly, I can’t thank my parents enough for granting me with the “Scholarship For Men Who Aren’t Ready To Leave School,” as well as for the quite literally endless love, pride, confidence and support. This work was funded by the Office of Naval Research (ONR). iii ABSTRACT In order to leverage advances made in body-armor materials, as well as to further the design landscape, considering body armor as a complete human-centric system is becoming more prevalent. This trend necessitates a greater focus on human systems integration (HSI) and human-centric design. Digital human models (DHMs) provide a powerful tool for HSI, but modeling-and-simulation tools, let alone DHMs, have rarely been used with body armor. With respect to analysis, this is changing. New methods for evaluating body armor from a biomechanical perspective have been developed within the SantosTM DHM. It is now possible to import digital models of body-armor systems, place them on an avatar, simulate various tasks (i.e., running, aiming, etc.), and then virtually evaluate the armor’s effect on performance, balance, mobility, bulk, etc. However, with respect to design, there are no available simulation tools to help users balance the goals of maximizing mobility and survivability concurrently. In response to these growing needs, there are two new areas of work being proposed and discussed. First, this work leverages a series of new virtual evaluation capabilities for Personal Protective Equipment (PPE) and implements a filter that automatically evaluates and selects from a library of designs the most advantageous PPE system based on user- selected objectives and constraints. Initial tests have shown realistic results with minimal computational demand. iv Secondly, this thesis proposes a new method for armor-system topology optimization that optimizes not only biomechanical metrics but also external (to the DHM system) metrics from potentially complex injury and protection models. The design variables for this optimization problem represent the position on the body of small body-armor elements. In addition, the existence of each element is modeled as a variable, such that unnecessary elements are determined and removed automatically. This inclusion of location in combination with the traditional existence variable is a novel inclusion to the topology optimization method. Constraints require that no two elements overlap. The objective functions that govern where the armor elements are moved must be general enough to function with any external data, such as survivability. Thus, a novel process has been developed for importing external data points (i.e., stress at points in the body resulting from a blast simulation) and using regression analysis to represent these points analytically. Then, by using sequential quadratic programming for gradient-based optimization, the armor elements are automatically positioned in order to optimize the objective function (i.e., minimize potential injury). This new approach allows any metric to be used in order to determine general body-armor concepts upstream in the design process. This system has the potential to become especially useful when trying to optimize multiple objectives simultaneously, the results of which are not necessarily intuitive. Thus, given a specified amount of material, one can determine where to place it in order to, for example, maximize mobility, maximize survivability, and maximize balance during a series of specified mission-critical tasks. The intent is not necessarily to provide a final design with one “click”; accurately considering all aspects of hard and soft v armor is beyond the scope of this work. However, these methods work towards providing a design aid to help steer system concepts. Test cases have been successfully run to maximize coverage of specific external data for internal organs (and thus survivability) and mobility, while minimizing weight. The weight metric has also been successfully used as a constraint in the optimal armor design. In summary, this work provides 1) initial steps towards an automated design tool for body armor, 2) a means for integrating different analysis models, and 3) a unique example of human-in-the-loop analysis and optimization. vi PUBLIC ABSTRACT In order to leverage advances made in body-armor materials, as well as to further the design landscape, considering body armor as a complete human-centric system is becoming more prevalent. This trend necessitates a greater focus on human systems integration (HSI) and human-centric design. Digital human models (DHMs) provide a powerful tool for HSI, but these modeling-and-simulation tools, have rarely been used with body armor. Currently, with respect to design, there are no available simulation tools to help users balance the goals of maximizing mobility and survivability concurrently. In response to these growing needs, two approaches are discussed. First, this work leverages a series of new virtual evaluation capabilities for Personal Protective Equipment (PPE) and implements a filter that automatically evaluates and selects from a library of designs, the most advantageous PPE system based on user-selected objectives and constraints. Secondly, this thesis proposes a new method for armor-system design optimization that optimizes not only biomechanical metrics but also external (to the DHM system) metrics from potentially complex injury and protection models. This new approach allows any metric to be used in order to determine general body-armor concepts upstream in the design process. This system has the potential to become especially useful when trying to optimize multiple objectives simultaneously, the results of which are not necessarily intuitive. Thus, given a specified amount of material, one can determine where to place it in order to, for example, maximize mobility, maximize survivability, and maximize balance during a series of specified mission-critical tasks. vii