AHFE Open AccessDigital Human Modeling and Applied Optimization
Editors: Sofia Scataglini, Sudhakar Rajulu
Topics: Digital Human Modeling and Applied Optimization
Publication Date: 2023
ISBN: 978-1-958651-52-0
DOI: 10.54941/ahfe1003347
Articles
Development of U.S. Army Tactical Brassiere (ATB) Sizing System
In support of the development of the U.S. Army Tactical Brassiere (ATB), a sports bra for physical training activities, a three-phase study was designed and executed. The first-phase study (Choi-Rokas et al., 2022) investigated the relationship between overall coverage, design features, anthropometric characteristics, and mobility of seven commercial-off-the-shelf (COTS) sports brassieres to document the pros and cons of each design feature. As the results, a single COTS brassiere was ranked as the best out of all assessed sports brassieres, based on breast coverage, reduction of breast movement, and overall participants’ preference. The current study is the second phase of the three-phase study focusing on the development of the sizing system for the ATB. Previous studies and related references (including but not limited to periodicals, video tutorials, manufacturer brassiere sizing charts, websites, and media, etc.) focusing on methodologies to predict brassiere size and/or to develop brassiere sizing systems were reviewed. Communalities between reviewed methods show: 1. Bust Circumference and Underbust Circumference are the two main body dimensions used for developing brassiere sizing systems. 2. The resultant band size is always an even number, in inches, for conventional brassiere sizing system in the U.S. 3. Cup size is determined based on the difference values (delta) between Bust Circumference and Underbust Circumference or between Bust Circumference and brassiere band size. Regardless of the methods to calculate the delta, the brassiere cup size increases by one size as the delta increases every 1-inch. Based on this knowledge, a new method to develop a sizing system was established. In this method, brassiere band sizes are converted from Underbust Circumference values with various adding factors depending on the torso size (i.e., gradually reducing the adding factor from 4-inch, then 0-inch for Underbust Circumference of 34-inch or greater), and brassiere cup sizes are based on the delta between Bust Circumference and Underbust Circumference. Next, the most recent U.S. Army female Soldier anthropometric databases (ANSUR II), which includes both manual and three-dimensional (3D) body shape scans, were reviewed to confirm the availability of two main dimensions, Bust and Underbust Circumferences. Because Underbust Circumference is not available in the original database (ANSUR II), was extracted from the 3D scan. Since dimensions extracted from 3D scans are not identical to their measured counterpart (i.e., Measured Waist Circumference of person A vs. the scan extracted Waist Circumference from person A’s 3D scan), the current study performed additional analyses to minimize those differences. Using the data from ATB phase 1 study, the manual and scan extracted Underbust Circumference measurements were compared, and a simple linear regression analysis was performed to model and predict the manual Underbust Circumference measurements from 3D scan extracted measurements. Then, this model was applied to the Underbust Circumference extracted from ANSUR II 3D database, allowing for the predication of manual Underbust Circumference for each participant. Finally, the established sizing method was applied to U.S. Army databases to develop a brassiere sizing system with 10 different cup sizes and 7 different band sizes. Three band sizes, 32”, 34” and 36” accommodated 92.03% of the target U.S. Army population. A total of seven sister sizes (sizes that share the same cup volumes, i.e., 32D, 34C, 36B, 38A, etc.) were grouped to accommodate over 93% of the target population. Visualization on the results, as well as the topic of fit models are further presented and discussed in this paper.
Hyegjoo Choi-Rokas, Peng Li, K. Blake Mitchell
Open Access
Article
Conference Proceedings
An iterative and anthropometrically driven approach to body armor plate design for females
The opening of combat arms positions to females, combined with innovative manufacturing processes allowing for increased curvature in rigid ballistic plates, allows the opportunity to design a body armor plate designed specifically for the female body. The current US body armor plates were developed from male torso shapes. This paper presents an iterative design and development process of female specific armor plates, based on the US Army anthropometric survey data (Gordon 2014) and rapid evaluation of prototyping designs.To understand the variation of female torso shapes, a female torso shape classification scheme was developed (Li, 2023), identifying nine torso groups for the US Army female population. For each shape group, a mean shape was generated from all torso surfaces within that group. Those nine torso shape groups were further categorized into three ‘curvature’ groups, based on angular measurement of the front profiles of each mean shape, as this will define the vertical curvature of a plate. Then two mean torso surfaces, a medium and a large bust shape were selected to target the prototype plate design for. Test plates were 3D printed but did not have equivalent weight as an ESAPI. Once the first plate shape was 3D printed, a design-fit evaluation-redesign cycle was initiated. A fit evaluation was performed to identify the design flaws. Then, those findings were documented and applied to the next round design, repeating this cycle four times. During each evaluation cycle, the current prototype, previous prototype versions, if applicable, and a 3D printed currently fielded plate were tested together. During the fit evaluation, the test participants’ (TPs) bra size was recorded but no measurements were taken. Based on TP’s bra size and prototype preferences, a fit table was created to correlate body size and bust shape to plate shape.The first round of fit evaluations involved the medium curvature plate and TPs (mostly with medium bust shapes). It was found that the TPs felt the top edge of the plate created pressure on the body, causing discomfort. We reduced the peak height of the prototyping plate by 20 mm to create the second iteration of the prototype. The second prototype was an improvement, however some could still feel the top edge of the plate. For the third iteration, the top and bottom plate edges were curved out to alleviate the pressure from the top edge, however, the fit test from this round indicated the curvature of the plate seems too flat. Hence the fourth prototype was developed by reducing the peak height only 10 mm from the first design with curved out edges on the top and bottom; it showed the best acceptability by all medium bust sized TPs. For future development, the accommodation envelope of the fourth iteration prototype will be evaluated so that we can delineate the anthropometric range of the central size in the target population, based on their breast size. Then, the large curvature plate will be evaluated to accommodate large breasted females (approximately 24% population according to the angular analysis of the front torso profile). Author contributions: P.L., H. C-R. and B. M. designed research plan and wrote the abstract. P.L. and H. C-R performed data analysis and fit evaluation, A.T and M.H did detail design and prototyping.References:Gordon, C. C., Blackwell, C. L., Bradtmiller, B., Parham, J. L., Barrientos, P., Paquette, S. P., Corner, B. D., Carson, J. M., Venezia, J. C., Rockwell, Belva M., Mucher, M., and Krietensen, S., (2014), “2012 Anthropometric Survey of U.S. Army Personnel: Methods and Sum-mary Statistics”, Technical Report NATICK/TR-15/007, US Army Soldier Systems Com-mand, Natick Research, Development and Engineering Center.Li, P., Mitchell, B., (2023), A shape classification scheme for female torso, Applied Ergonomics, Volume 106, 2023, 103904, ISSN 0003-6870,https://doi.org/10.1016/j.apergo.2022.103904
Peng Li, Hyegjoo Choi-Rokas, Blake Mitchell, Asbed Tashjian, Matthew Hurley
Open Access
Article
Conference Proceedings
Development of Test and Evaluation Methodologies for Headborne Low Light Sensor Systems
The military is working on improving technical capabilities by developing increasingly advanced low-light sensor headborne systems. There are several known limitations of legacy night vision devices (e.g., narrow field of view, poor depth perception, monochrome display, monocular output), and as technology moves forward, the U.S. Army needs ways to test and evaluate visual performance between systems. The presented research sought to identify, modify and/or develop a series of test methodologies to assess the visual performance of users while wearing these new technologies.Standardized vision performance tests have been used for several decades to assess visual capabilities of the human eye. These tests have been validated through research and clinical usage and are accepted as means of assessing vision, but usually only for the bare eye. Additionally, some tests cannot be used exactly as designed because of one or more design or functional characteristics of night vision/visual enhancement devices (e.g., helmet mounting, monocular view, etc.). We set out to assess the potential of each standard test to be used as designed and, when that was not possible, we modified the test and assessed its potential as a test and evaluation tool for developmental systems.The methodologies were assessed with 14 male, active-duty infantry Soldiers (Age: 22.5±4.31; years in service 3.2±2.40) who all had normal corrected vision (1 participant was red-green color blind). The test included two legacy night vision devices and one prototype device. The test was conducted to both assess the methodologies and compare the legacy devices to the prototype device to determine any improvements in prototype performance over the legacy device performance.Seven tasks were assessed in this study: 1. The Pelli-Robson Contrast Sensitivity test, which showed significant differences between the tested systems. 2. The Howard-Dolman test (depth perception), which did not result in significant differences between the systems. 3. Field of view performance, using a modernized version of a Ferree-Rand projection perimeter, which resulted in significant differences between the tested systems. 4. A timed pegboard task, to assess hand-eye coordination and dexterity performance, which showed significant differences between the tested systems. 5. A visual acuity assessment task, which assesses the vestibulo-ocuar reflex (VOR) function, showed significant differences between the tested systems. 6. A modified version of the Multi-Target Stepping Task, used to assess limb control, showed significant differences between the tested systems. 7. A novel target stamping task developed to evaluate hand-eye coordination and to measure the impacts on reach accuracy, showed significant differences between the tested systems.Initial testing shows these methodologies are promising as tools to evaluate night vision devices. Other than the Howard-Dolman test, all were sensitive enough to statistically differentiate between the tested items. Follow-on steps include: conducting model analysis to understand the relationship between performance in a given task versus the other; develop the assessed methodologies further to improve test reliability; develop and identify other potential new tests and tools to use as evaluation methods; and utilize the finalized methodologies in any applicable system evaluations.
Jose Villa, Edward Hennessy, Blake Mitchell, Reeve Goodenough, Rebecca Skulsky
Open Access
Article
Conference Proceedings
Evaluating the effects of visual traits on individual marksmanship performance in a simulated fireteam engagement
Enhancing fireteam lethality remains a key priority for the U.S. Army. Along with team dynamics, individual marksmanship performance is a core contributor to a fireteam’s lethality. When considering factors that affect marksmanship performance, an individual’s visual sensory and perceptual traits have been identified as having some of the most influential impacts, however, these insights have primarily been drawn from studies wherein participants completed individually based marksmanship tasks. From an operational perspective, Soldiers are more likely to engage in combat at the team level or higher, and thus, research investigating the effect of individual traits in the context of a team marksmanship task is warranted. The goal of this research is to evaluate individual traits by quantifying relationships between visual traits and marksmanship performance during a team marksmanship task and assess which traits are well defined between high and low performing individuals on the team. This research was completed using data from a cohort of 38 male, Infantry Soldiers who completed a simulated team shooting scenario (TSS) in teams of three at a 72-hour field exercise. Prior to the study onset, visual trait information was collected from each participant, to include dynamic visual acuity, field of view, and useful field of view data. These traits were compared to marksmanship performance gathered from the TSS task. The scenario represented an escalating firing engagement over five minutes. In this engagement, teams were situated in the center of a circle of 28 LED targets, which they were required to scan and engage when a designated hostile was displayed. During the scenario, the LED targets were dormant until activated at various times in different shapes to represent hostile or friendly targets. Weapon-attached sensor technology provided shot timing and placement data which was used to calculate team marksmanship outcomes (i.e., probability of target hits, percent of targets engaged).To explore the relationship between visual traits and marksmanship performance, a correlation analysis was conducted using baseline visual trait data and the TSS marksmanship data. Results of the analysis revealed a strong relationship between central vision processing and probability of hit (r = .32, p = .06). To assess differences in central vision processing between high and low skilled performers (high performers had a p(hit) greater than .3, N = 19), an independent t-test was conducted with marksmanship performance group as the independent variable and central vision processing accuracy as the dependent variable. Results of this analysis revealed a statistically significant difference (t(35) = 2.11, p = 0.04, d = .68), between the top half of performers (M = .92, SD = .03) and the bottom half of performers (M = .87, SD = .08). These results suggest that individuals with higher visual processing capabilities are more likely to perform better in realistic operational engagements with a dynamic setting requiring sector scanning. Findings of this study provide initial evidence that technological or training enhancements to marksmanship performance should consider addressing deficits in or augmenting central visual processing to improve probability of hit on the intended target.
Peioneti Lam, Jose Villa, John Christopher, Stephanie Brown, Linda Desimone, Wade Elmore, Seth Elkin-Frankston, Victoria Bode, Blake Mitchell
Open Access
Article
Conference Proceedings
Movement Description Method and Application for Dance of Chinese Traditional Drama
The purpose of this research is to propose a description model of human motion for Chinese traditional drama, which contained body structure, spatial orientation and movement force effect three dimensions. A multi rigid model is established based on the relative relationship between nodes and edges, record the movements of each part with geometric figures to establish the skeleton hierarchy of multiple joint points. In addition, we applied the description method on the virtual body in digital CTD performance system, which is designed base on augment reality technique. Also, we extracted the complete set of human motion from CTD such as martial dramatic works and body movement in Bingxi painting dance performance, and design the virtual human action by combining the posture base on the model above. This description method can realize the creative transformation and innovative development of Chinese excellent traditional culture in intelligent media.
Yihang Du, Zhang Yao, Niu Ke
Open Access
Article
Conference Proceedings
Considerations when Applying the BioRID II Dummy Used in Crashworthiness tests to 50 Percentile of Korean, Chinese, and Japanese Height
The Insurance Institute for Highway Safety (IIHS) uses BioRid II dummies to evaluate seat safety. However, it is necessary to verify whether this dummy actually represents the body well when seated. In the case of women, the incidence of whiplash injury is two to three times higher than that of men, so a new dummy was created for this purpose. In addition, since there is a difference in the driver's median height by country, it is necessary to verify whether the dummy used in the actual vehicle crash test adequately represents the difference in the standard body size of the driver in that country.Purpose: A decision was made to compare the specifications of the BioRid II dummy used in the crash test and the numerical values of the evaluation items when the actual participants sat in the test condition. The height of the participants was classified into the height of the 50th percentile for the males and females of each country, and the difference was analyzed through a comparison with the parameter data of BioRID II.Method: A total of 15 participants were seated in a crashworthiness situation including the seatback angle, and side-view X-rays were taken and data were acquired. On the X-ray, the angle of the occipital interface plate relative to horizontal, the angle of the T2 vertebra relative to horizontal, the H-point indicator to occipital condyle pin (horizontal), and the H-point to indicator to occipital condyle (vertical) were measured. Then, after classifying according to the median height of Korea, China, and Japan, each data was compared with the parameters of BioRID II.Result: In the angle of the occipital interface plate relative to horizontal, which is a parameter used for testing in IIHS, BioRID II was measured as 29.5 ± 0.5°. When the average height was 175.6cm, the angle of the occipital interface plate relative to horizontal was 18.3 ± 5.89°, 170.4cm was 18.60 ± 5.36, and 162.3cm was 19.05 ± 4.93°. The angle of the T2 vertebra relative to horizontal was 37 ± 0.5° for BioRID II, 11.7 ± 8.38° for the average height of 175.6cm, 10.21 ± 7.55° for 170.4cm, and 7.60 ± 5.9° for 162.3cm. The H-point indicator to occipital condyle pin (horizontal) was 156 ± 3mm for BioRID II, 272.3 ± 60.57mm for the average height of 175.6cm, 251.1 ± 63.97mm for 170.4cm, and 219.2 ± 59.62mm for 162.3cm. The H-point indicator to occipital condyle (vertical) was 609 ± 3mm for BioRID II, 734.5 ± 39.18mm for the average height of 175.6cm, 708.2 ± 46.90mm for 170.4cm, and 668.6 ± 23.91mm for 162.3cm. As such, there was a difference in the values of the parameters presented in BioRID II and the values according to the height corresponding to each country's actual height.
Woojin Choi, Siyoung Choi, Ka Sanghoon, Kim Sunwoong, Sohn Moonjun
Open Access
Article
Conference Proceedings
A simplified human body model for assisting electric bicycle design
Compared to non-electric bicycles, power-assistance ones could be designed for more postural comfort with less consideration of power production when pedalling. The present work aimed to develop a simplified human body model to assist in the design of power-assisted bicycles to better accommodate a target user population. To characterize body posture in bicycle use, the inter-segmental angles corresponding to a reference posture were measured from a sample of 63 males and females testing 4 existing bicycle models for comfort and long distance use. As a first approximation, only upper body was modelled as a 2D linkage composed of trunk (hip to shoulder) and arm (shoulder to grip) segments. To better account for postural effect, functional segment lengths were measured in the reference posture, and used to build the regression equations with body height. For a given bicycle characterized by saddle and handlebar position, the hip and shoulder angles could be fully determined for a rider using the proposed model. To validate the model, we compared the measured and predicted inter-segmental angles and showed that the proposed human model could account for the effects of both body height and bicycle’s geometry. To show the usefulness of the proposed model, a comfortable range of hip and shoulder angles was defined from the experimental data and was used to predict the fit area of handlebar and saddle position for both short and tall persons. Simulation results show that a more reclined seat tube could better accommodate both short and tall users.
Xuguang Wang, Junfeng Peng
Open Access
Article
Conference Proceedings
Assessing Ergonomics on Cobot for an Optimized Integrated Solution in Early Phase of Product and Process Design
The design goal for Human-Robot collaboration is combining the repeatability and productivity of automated systems with the flexibility of the operators [1]. One main interest is for cobots to take over complex and physically demanding assembly tasks, reducing the biomechanical workload on workers and increasing product quality. However, as reported by several authors [1-3], the introduction of cobots is not straightforward and should be thoroughly investigated and planned to avoid higher mental stress on workers and a decrease in efficiency. In this respect, Digital Human Modelling can support the integration of robots in design or evaluation of hybrid cells, anticipating process and interaction criticalities.One key aspect of hybrid cells is task allocation between worker and cobot. Recently, Authors in [4] proposed an optimization procedure that looks into productivity and ergonomics. However, the proposed approach is rather complex to apply and does not allow for evaluations of the what-if type, which are particularly useful in the development of new hybrid cells.The paper proposes a new methodology, which has the advantage of being simple and allowing for a visualization of shared operations through a simulator, and for a heuristic evaluation during the design phase of the hybrid workstation, and, finally, permitting a “what-if” analysis. The work is part of the research project D-HUMMER (Digital HUMan Model for ERgonomic workplace) funded by EIT Manufacturing (project number 22294).The simulation tools are the IPS IMMA and IPS Robotics that integrate in the same scenario the evaluation of the biomechanical load on different anthropometries of workers with the performance of the robot working cycle. The advantage of a full digital approach allows frontloading in Concept Phase the workstations’ layout and sequence, even considering different variants, before any production line is established.In the presented methodology, each working job scenario is represented by a state-machine (fig. 1), where each state defines a single atomic task (i.e. a single state) that may be fulfil by either the robot or the human operator, depending on the choice of the workplace designer. Each atomic task is characterized by several parameters (e.g. human strains, time of execution, etc.). In each of the simulator runs, a performance index I_k is computed:I_k = sum_(i=1, to n) alpha_i,k * t_i,k + beta_i,k * s_i,kwhere:k : is the index of each scenario, each represented by a state machine.i : is the index of each state in the state machine.t_i,k : is the time required for each atomic tasks_i,k : is the human strain required for each atomic taskalpha and beta are appropriate weights for each parameter.The paper presents the methodology through a real industrial use case of the Whirlpool microwave assembly. In the current workstation (fig.2) the operator assembles a heavy component (transformer), given by a robot that places it on a table. The worker has therefore the full weight of the component in hands. The optimized solution (fig.3) improves the robot usage, resetting the weight for the worker, and achieving better safety and ergonomics conditions.The methodology has been applied to an already-existing industrial solution. However, its application in early stage may mark a paradigm shift in the workstation design layout for manufacturing companies.
Valerio Cibrario, Manuela Vargas Gonzalez, Cesare Fantuzzi, Maria Pia Cavatorta, Enrica Bosani, Daniel Dengel, Meike Schaub, Niclas Delfs, Elin Fägerlind, Alessandro Bagalà, Domenico Spensieri
Open Access
Article
Conference Proceedings
Effects of Back Postures on Driving Positions as Measured with DHMs
Drivers use a range of back postures that affect seated positions. Standards in seat design and safety tests assume drivers sit in fully supported back postures which this investigation finds invalid for small females. Twenty-two cars and 20 utility vehicles from Europe, USA, and Asia were measured and evaluated with the ERL Digital Human Models. In these vehicles, the head restraint interferes with upright postures in small females and requires an average neck flexion that is 2.9X greater than optimal for driving positions in these DHMs. Small women’s thighs penetrate the linear elastic region of front of cushion an average of -5.7 ±5.9 mm which would require muscle contractions to compress for holding the heel on the floorboard. Postural adaptations move small women into unsupported backs for driving. Consequently, improvements in vehicle and seat designs for back posture variability are needed for comfort, ergonomics, and safety.
Mac Reynolds, Sofia Scataglini
Open Access
Article
Conference Proceedings
Analysis of Changes in Spinal and Pelvic Parameters when Optimally Seated on an Automotive Seat Compared to Standing
PURPOSE: The comfort of a seat in a seated posture has been reported to be affected by the alignment of the spine and pelvis in a standing posture when designing an automotive seat. Therefore, in order to find items to improve vehicle seat comfort performance, this study was conducted to measure the change in spinopelvic parameter values according to a change from a standing posture to a seat sitting posture and to reflect them in the design of vehicle seats to improve comfort.METHOD: X-ray data for 15 participants was measured and analyzed while standing and sitting in the optimal posture on an automotive seat. Cervical lordosis angle, thoracic kyphosis angle, lumbar lordosis angle, sacral inclination angle, and C7-SVA (sagittal vertical axis) were measured.RESULTS: Compared to standing, there were no statistically significant changes in the cervical lordosis and thoracic kyphosis angles when sitting in the car seat in the optimal posture, but only the lumbar lordosis changed (from 32.13° ± 8.356° to 6.568° ± 3.048°, p<0.0001). Cervical lordosis varied from 12.78° ± 8.15 to 12.58° ± 9.14° and thoracic kyphosis from 30.34° ± 8.10° to 31.6° ± 9.48° when standing and sitting in an optimal posture, but there was no statistical significance. However, the lumbar lordosis decreased from 32.13° ± 8.36° to 6.57° ± 3.05° and the sacral inclination angle decreased from 27° ± 11.13° to -21.79° ± 6.48°, respectively, and both were statistically significant in the paired t-test (p< 0.0001, p<0.0001, respectively). In the case of C7-SVA, there was a statistically significant change from 22.26 ± 15.17mm to 94.23 ± 46.14mm (p=0.0007). Except for the differences in the cervical lordosis angle change and the thoracic kyphosis angle change, there were statistically significant differences in standing and sitting conditions.CONCLUSION: As a result of this study, the changes in lumbar lordosis angle, sacral inclination angle, and C7-SVA were greater when sitting on a seat than when standing. This is related to the performance of comfort when sitting on a seat, and this data is expected to be used as useful data for designing seat shapes and lumbar support when developing seat designs in the future.
Woojin Choi, Siyoung Choi, Ka Sanghoon, Kim Sunwoong, Sohn Moonjun
Open Access
Article
Conference Proceedings