Although modeling and simulation are fertile areas for research and development within medicine, education, and human factors, there is a growing need for fully integrated organ systems as part of any digital human model (DHM). This need is particularly high in task-based survivability assessment. However, the current static geometry used in DHM is insufficient for evaluating conditions during simulated task performance. This insufficiency is due to the fact that internal viscera are inherently non-rigid objects. Therefore, undesirable, and unrealistic behaviors occur when using static models to represent internal viscera as the DHM moves through a variety of postures. The capacity for DHMs to take on a variety of postures and positions contributes to their overall usefulness in modeling and simulation. By using static models to represent internal viscera, errors in model behavior must be tolerated, or the DHM must be limited to a posture that matches the models’ configurations. With the either option being undesirable there is a need to represent internal viscera using dynamic models. A dynamic model will allow for the geometry used in representing the internal viscera to deform as the DHM. Thus this work proposes a computational platform for controlling the motion and deformation of internal viscera models within a DHM. This platform consists of two components. The first component is a new method for maintaining a relative position within a dynamic character’s mesh called skin-based parenting. The second component is a system which takes a free-from deformation technique used in artistic modeling and eliminates the manual input that is usually required. This platform produces representations of internal viscera which conform to the character’s posture in real-time at an interactive rate. Thus enabling the assessment of how particular environmental influences relate to the position and orientation of internal viscera models within a DHM in a variety of postures.

This study focuses on testing the validity and reliability of dynamic Virtual Interactive Design (VID) methodology with dynamic ergonomics analysis. Virtual Interactive Design methodology has been introduced and applied on practical problems in several previous studies, and initially validated with posture-based static ergonomics analysis tools. Although most results have proved the validity and reliability based on static information considered, such validation processes is not sufficient since risks for performing certain tasks can not be fully examined without examining dynamic aspects. But the dynamic virtual interactive design environment has not been validated sufficiently. In my subsequent study, a dynamic ergonomics analysis tool will be integrated into virtual interactive design environment. For the validation of new dynamic virtual interactive design environment, experimental human motion data from 36 subjects in several tasks are imported into the integrated system and dynamic analysis results are achieved. Also, dynamic ergonomics risk results from motion captured directly from human subjects and static ergonomics risk results from virtual interactive design environment are calculated, which two will be used as standard. Comparisons between interested motion series and standard series with respect to ergonomics risk results are applied for validation purpose. And test-retest method is used for testing reliability.

Today's challenge for workforce management lies in providing a healthy, safe and productive working culture where people are valued, empowered and respected. Workforce diversity is becoming an essential aspect of the global workforce, and ageing is the most prominent and significant factor in this regard. Diversity brings many opportunities and challenges, as workers with different backgrounds, cultures, working attitudes, behaviours and age work together, and in future, the key to organizational effectiveness and sustainability will heavily depend on developing and sustaining inclusive work environments where people with their differences can co-exist safely and productively. Manufacturing organizations expect the highest levels of productivity and quality, but unfortunately the manufacturing system design process does not take into account human variability issues caused by age, skill, experience, attitude towards work etc. This thesis focuses on proposing an inclusive design methodology to address the design needs of a broader range of the population. However, the promotion and implementation of an inclusive design method is challenging due to the lack of relevant data and lack of relevant tools and methods to help designers. This research aims to support the inclusive design process by providing relevant data and developing new design methodologies. The inclusive design methodology suggested in this thesis is a three step approach for achieving a safe and sustainable work environment for workers, with special concern for older workers. The methodology is based on the provision of relevant human capabilities data, the capture and analysis of difference in human behaviour and the use of this knowledge in a digital human modelling tool. The research is focused on manual assembly through a case study in the furniture manufacturing industry and joint mobility data from a wide-ranging population has been analysed and the task performing strategies and behaviours of workers with different levels of skills have been recorded and analysed. It has been shown that joint mobility significantly decreases with age and disability and that skilful workers are likely to adopt safer and more productive working strategies. A digital human modelling based inclusive design strategy was found to be useful in addressing the design needs of older workers performing manufacturing assembly activities. This strategy validates the concept of using human capabilities data for assessing the level of acceptability of any adopted strategy for older workers, and suggests that the strategies adopted by skilful workers are more likely to be equally acceptable for older and younger workers keeping in view differences in their joint mobility. The overall purpose of this thesis is to present a road map towards the promotion and implementation of the inclusive design method for addressing workforce challenges and in future the same strategies might be implemented within a variety of other industrial applications. The proposed three step inclusive design methodology and getting a reasonable understanding of human variability issues along with the use of human capabilities data (joint mobility in this case) in a human modelling system for design assessment at a pre-design stage can be considered as the major contributions of this research.

This study develops theorems which generalize or improve the existing predictive dynamics method and implements them to simulate several motion tasks of a human model. Specifically, the problem of determination of contact forces (non-adhesive) between the environment and the digital human model is addressed. Determination of accurate contact forces is used in the calculation of joint torques and is important to account for human strength limitations in simulation of various tasks. It is shown that calculation of the contact forces based on the distance of the contact areas from the Zero Moment Point (ZMP) leads to unrealistic values for some of the forces. This is the approach that has been used in the past. In this work, necessary and sufficient constraints for modeling the non-adhesiveness of a contact area are presented through the definition of NCM (Normal Contact Moment) concepts. NCM point, constraints and stability margins are the new theoretical concepts introduced. When there is only one contact area between the body and the environment, the ZMP and the NCM point coincide. In this case, the contact forces and moments are deterministic. When there are more than one contact areas, the contact forces and moments are indeterminate. In this case, an optimization problem is defined based on the NCM constraints where contact forces and moments are treated as the unknown design variables. Here, kinematics of the motion is assumed to be known. It is shown that this approach leads to more realistic values for the contact forces and moments for a human motion task as opposed to the ZMP based approach. The proposed approach appears to be quite promising and needs to be fully integrated into the predictive dynamics approach of human motion simulation. Some other insights are obtained for the predictive dynamics approach of human motion simulation. For example, it is mathematically proved and also validated that there is a need for an individual constraint to ensure that the normal component of the resultant global forces remains compressive for non-adhesive contacts between the body and the environment. Also, the ZMP constraints and stability margins are applicable for the problems where all the contacts between the environment and the body are in one plane; however, the NCM constraints and stability margins are applicable for all types of arbitrary contacts between the body and the environment. The ZMP and NCM methods are used to model the motion of a human (soldier) performing several military tasks: Aiming, Kneeling, Going Prone and Aiming in Prone Position. New collision avoidance theorems are also presented and used in these simulations.

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. 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 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.

This study was conducted to assess the validity and reliability of the Virtual Build methodology for ergonomics design and analysis. Thirty-six human subjects participated in this study and performed a set of six tasks. The tasks were performed twice in both real and virtual environment. The subject?s motion in performing tasks was analyzed by ergonomics assessments by using Virtual Build methodology. Criteria-related validity was evaluated by comparing the Virtual Build ergonomic assessment results with manual calculation. Test-retest reliability was evaluated by correlating ergonomics assessment results between two trials. The result shows that the Virtual Build methodology is reliable for ergonomic assessments. 48 out of 51 reliability index scores are higher than 0.8. The Virtual Build with virtual environment has lower over-time reliability performance than the real environment. The t-test shows that the Virtual Build is valid for 1991 NIOSH lifting equation assessment when using real environment. Some improvements in enhancing human perception need to be done to make Virtual Build valid when using virtual environment.

No description available.

Simulating realistic human behavior on a virtual avatar presents a difficult task. Because the simulated environment does not adhere to the same scientific principles that we do in the existent world, the avatar becomes capable of achieving infeasible postures. In an attempt to obtain realistic human simulation, real world constraints are imposed onto the non-sentient being. One such constraint, and the topic of this thesis, is self-collision avoidance. For the purposes of this topic, a posture will be defined solely as a collection of angles formed by each joint on the avatar. The goal of self-collision avoidance is to eliminate the formation of any posture where multiple body parts are attempting to occupy the exact same space. My work necessitates an extension of this definition to also include collision avoidance with objects attached to the body, such as a backpack or armor. In order to prevent these collisions from occurring, I have implemented an effort-based approach for correcting afflicted postures. This technique specifically pertains to postures that are sequenced together with the objective of animating the avatar. As such, the animation's coherence and defining characteristics must be preserved. My approach to this problem is unique in that it strategically blends the concept of keyframe interpolation with an optimization-based strategy for posture prediction. Although there has been considerable work done with methods for keyframe interpolation, there has been minimal progress towards integrating a realistic collision response strategy. Additionally, I will test this optimization-based approach through the use of a complex kinematic human model and investigate the use of the results as input to an existing dynamic motion prediction system.

Der Einsatz von digitalen Menschmodellen erlaubt neben einer frühzeitigen ergonomischen Analyse die Gestaltung von Arbeitsprozessen und stellt ein hilfreiches Werkzeug in der Produkt- und Prozessgestaltung dar. Im Rahmen dieses Beitrages soll auf ausgewählte Schwerpunkte der Entwicklung des digitalen Menschmodells „The Smart Virtual Worker“ eingegangen werden. Das Forschungsprojekt soll einen Beitrag zur Lösung, der mit dem demografischen Wandel der Gesellschaft einhergehenden Herausforderungen leisten. Die daraus resultierenden Forschungsschwerpunkte liegen insbesondere in der Einbeziehung von Alterungs- und psychischen Faktoren in die Bewegungsgenerierung des Menschmodells und der Modellierung von Umweltbedingungen. In Umsetzung des Projektes wurde ein erstes Arbeitsszenario erarbeitet, auf dessen Basis die vorgenannten Forschungsaufgaben interdisziplinär gelöst werden sollen.

The present work deals with the development of a computational geometric framework for vision modeling for performing visibility and legibility analyses in Digital Human Modeling (DHM) using the field-of-view (FoV), estimated geometrically from 3D tessellated head scans. DHM is an inter-disciplinary area of research with the prime objective of evaluating a product, job or environment for intended users through computer-based simulations. Vision modeling in the existing DHM’s has been primarily addressed through FoV modeling using right circular cones (RCC). Perimetry literature establishes that the human FoV is asymmetric due to unrestricted zygomatic vision and restrictions on the nasal side of the face. This observation is neither captured by the simplistic RCC models in DHM, nor rigorously studied in vision literature. Thus, the RCC models for FoV are inadequate for rigorous simulations and the accurate modeling of FoV is required in DHM. The computational framework developed in this work considers three broad components namely, the geometric estimation and representation of FoV, visibility and statistical visibility, and legibility of objects in a given environment. A computational geometric method for estimating FoV from 3D laser-scanned models of the human head is presented in this work. The strong one-to-one similarity between computed and clinically perimetry maps establishes that the FoV can be geometrically computed using tessellated head models, without necessarily going through the conventional interaction based clinical procedures. The algorithm for FoV computation is extended to model the effect of gaze-direction on the FoV resulting in binocular FoV. A novel unit-cube scheme is presented for robust, efficient and accurate modeling of FoV. This scheme is subsequently used to determine the visibility of 3D tessellated objects for a given FoV. In order to carry out population based visibility studies, the statistical modeling FoV and generation of percentile-based FoV curves are introduced for a given population of FoV curves. The percentile data thus generated was not available in the current ergonomics or perimetry literature. Advanced vision analysis involving character-legibility is demonstrated using the unit-cube with an improved measure to incorporate the effect of character-thickness on its legibility.