Conference PaperPDF Available

Using 3D Scanning for Improved Helmet Design

Authors:
Using 3D Scanning for Improved Helmet Design
Simone MORLOCK*, Andreas SCHENK, Anke KLEPSER, Andreas SCHMIDT
Hohenstein Institut für Textilinnovation gGmbH, Boennigheim, Germany
DOI: 10.15221/16.190 http://dx.doi.org/10.15221/16.190
Abstract
"One-size-fits-all’ is definitely not a good approach to helmet design, especially for situations with the
significant risk of head injury such as sports and industrial workplaces. Function of helmets is only
given with perfect fit. But the complex geometry of heads was insufficiently defined by traditional
measurement which captures length, width and circumference only as numerical values. Therefore, no
head shape information was available so far. In contrast, 3D scanning-technology provides an
innovative approach for analyzing head measurements and shapes.
Scientific analyses show remarkable variations in head shapes of humans within the same head
circumference. Despite the real need for head protection systems, no reliable anthropometric German
head data of women, men and children was available so far. The results of the Hohenstein R&D
project „Textile-based head protection systems“(IGF 16976 N) close this information gap. To collect
exact three dimensional head data a specific scanning process was installed, heads of men, women
and children were scanned and a database of 3D scan head data was created. Statistic evaluations as
well as 3D shape analysis were conducted. Market share tables and virtual 3D shape models
representing realistic head shapes of German population were generated and new innovative virtual
3D analysis methods for proving fit and ergonomic comfort were developed. 3D scanning-technology
provides an innovative approach for the optimization of helmets in consideration of fit, functionality and
design. In summary, the study results provide fundamental guidelines for helmet optimization in
consideration of fit, functionality and design.
Keywords: 3D body scanning, head measurements, head shapes, size charts, helmet fit
1. Introduction
An increasing number of users – from children to seniors – are dealing with head protection for work
and leisure. There are growing safety demands due to increasing awareness both in legal regulation
and voluntary motivation. But only a helmet that fits and is worn consequently can prevent from severe
head injuries. Despite the real need for head protection systems, no reliable anthropometric head data
of women, men and children was available. Companies had no access to up-to-date-data or
information about head shape or their percentage shares. Findings of morphological research show
subjects with the same head circumference, but differing head shapes. [1] There is a wide variance
between oval and round profiles. Figure 1 shows two individual male heads. Both with a head
circumference of 58 cm corresponding head size 58. Head shapes differ significantly illustrated by the
cross-sections as well as head breadth, length and height.
Fig. 1. Same head circumferences show differences between head morphology
*s.morlock@hohenstein.de; +49- 7143-271-305; www.hohenstein.de
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A head breadth variance with a delta up to 4 cm was identified. This difference cannot be covered by
only one helmet size or shape. Therefore, industry standards do not comply with the state of the art
and anthropometric reality anymore. Figure 2 shows the range of head forms within the head size 58.
Fig. 2. Range of head shapes within the head size 58
There is an increasing number of research publications studying head shape and measurements [2] [3]
[4] [5] [6] [7] [8] [9] [10] among others. This shows the great importance of the issue. Anthropometric
findings from other countries may not be transferred to German population because ethnical groups
differ in body morphology. This also applies to heads. [2] Therefore, German public funded project
„Textile-based head protection systems“ [1] was conducted. Within the project head measurements
and shapes of about 6000 men, women and children of the German population were analyzed and
statistically evaluated. All findings were summarized in a new head specific sizing system. Furthermore,
3D shape analyses were performed. Head types were defined and visualized via 3D head models. To
generate a size range in line with market requirements, market shares were calculated.
The advantage of the new head sizing chart is the classification according to sizes. Unlike ergonomic
procedures there are no percentiles described. For example, standard DIN 33402−2
„Ergonomie-Körpermaße des Menschen“ [11] provides only the 5, 50 and 95 percentile. An
assignment to sizes is not possible as percentiles only give information about the percentage share
smaller or bigger than the percentile, respectively.
2. Methods
2.1 Anthropometric 3D head study
Main requirement of the project success was a reasonable amount of target group body data. A
representative 3D scan data pool (n=20000) was available resulting from numerous anthropometric
research projects [12] [13] [14] [15] [16] and others. This 3D body data was acquired by utilizing 3D
bodyscanner Vitus Smart XXL. However, not all data files could not be used for statistic evaluation
because of interference of hair. This will be further described below. A great amount of data had to be
post processed with big effort, e.g. removing hair. Still, a lot of head data could not be used for the
project and had to be excluded. Finally a sample of about 6000 heads of men, women and children
was assembled.
To guarantee the validity of the statistic evaluation, the available scan data quality had to be verified.
This was necessary because 3D bodyscanner Vitus Smart XXL is designed for full body acquisition,
not for detailed hand, feet or head capturing. Therefore, a preliminary study with hand held scanner
Creaform Ergo Handyscan was conducted to capture detailed head and face morphology. For this
purpose, a specific head scanning process was developed (see Figure 3).
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Fig. 3. 3D head scanning process with Creaform Ergo Handyscan
The challenge was to stabilize the head for reducing movements which falsify the scan and
measurement results. 118 heads of men and women were scanned and a comprehensive number of
measurements from each head has been taken. In addition some subjects’ measurements were taken
manually. The measurement by traditional measuring tape was performed with and without scan cap
to analyze possible differences. These head-scans and measurement results were used for evaluating
the head scans captured with Vitus Smart XXL. The objective was to identify the influence of different
scanner systems as well as the influence of hair on the measurement results.
2.2 Verifying data quality
To verify data quality of available scan data several comparative studies were performed. The results
of the measurements manually and digitally as well as the outcome of the different scanner systems
were compared. Findings of the analyses were:
Head measurements taken from Vitus Smart data are considered to be valid
Head circumferences taken from Creaform Scans are around 2 mm smaller than from Vitus Scans
On average, head circumferences taken manually are smaller than digital measurements
In most cases, variation in dimension is bigger on women than on men
Reasons for measurement differences are numerous. They may be caused by the usage of differing
scanner systems (resolution, technic etc.), by head movement during scan process, by inconsistency
of measurement points, by interpersonal variance of measurement technics as well as by individual
subjects’ hair volumes. But, the main reason for measurement differences is hair volume. Figure 4
illustrates the described data analyses. Male subject on the left side is bald-headed. Female subject on
the right side has got voluminous hair. Below the scan pictures there are the head measurements of
Creaform scans, Vitus Scans as well as manually acquired. In addition, there are results of manual
measurements with and without scan cap. Head circumference of the male subject show almost no
differences. For the female subject with large hair volume, measurements differ significantly. Values
range up to 2.9 cm. Besides, scan cap influences values as well.
Fig. 4. Influence of hair volume on head circumference measurements
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The comparison shows that large hair volume unavoidable lead to clear measurement differences. The
least impact has the scanner system itself. Although, Creaform system generates scans with higher
resolutions and therefore better quality, the differences to scans of Vitus system are in average only
2 mm. Compared to other influencing factors the importance is rather marginal. Big influence has the
measurement technique – tape measure or 3D scanner technology in relation to the tension of
manual or digital tape measure. This significantly influences the effect on hair compression while
measuring and thus the measuring results. In addition, in manually measurements interpersonal
difference occur due to inconsistent and non-reproducible tension. Consequences are clear
measurements differences. The larger the hair volume, the bigger are the measurement differences.
Since, women do have often voluminous haircuts, the average measurements differences of female
subjects are bigger than of male subjects.
Furthermore, scan cap influences results as well. Scan caps have to be worn to compress hair for
gathering precise object surface because scanner does only capture surfaces. In former sizing surveys
classic fabric swim caps were used. To get comparable scan results, the same type of caps was
applied in the preliminary study. The disadvantage of those caps is the rather lose fit compared to
neoprene, latex or silicon caps. For that reason, compression is less strong. The advantage is the
simple and wrinkle free donning as well as ears are not covered by the caps. This is necessary to
determine precise head breadth. If a cap bridges the head to ear distance, head breadth will increase
due to hollow spaces. Besides, swim caps made of neoprene, latex or silicon are not easy to be
donned on dry hair. Wrinkles occur or test subjects’ hair cut might be ruined. Hence, acceptance of
voluntary subjects is not likely for neoprene, latex or silicon caps.
As people do have differing hair volume, it is impossible to determine 100 % accurate head
measurements with state of the art techniques. As described before each scan had to be examined
and poor quality had to be sorted out. In consequence, from the original 20000 available scans 2970
male, 1890 female, 800 boys’ and 520 girls’ heads were left to be analyzed. Furthermore, a correction
factor was implemented. With this value every measurement influenced by hair, like head
circumference, head breadth or head depth, were reduced by correction factor 1.7 %.
2.3 Definition of head measurements
The definition of anthropometric measure points is based on DIN 33 402 [11] and ISO 7250 [17]. Using
standardized methods guarantees comparability of research findings. In addition, new measurements,
e.g. “Upper face breadth”, “Distance head apex to eye” or “Distance head apex to upper ear base”
were analyzed. Overall 25 head and face measurements were taken from each head. Figure 5
presents several head and face measurements, described in the final sizing charts.
Fig. 5. Head and face measurements according to DIN 33 402, ISO 72510 and additional dimensions
2.4 Fundamentals of the sizing chart development
The sample of about 6000 data sets of men, women and children was the basis for the development of
the sizing charts. On that basis, it was possible to perform a representative evaluation of the
morphological head forms in relation to the 3-dimensional head shape. First, every measurement data
set had to be double checked to ensure quality standards. Trained personnel took measurements
interactively. Within the process of plausibility assessment, outlier were identified and erased.
Therefore, a very precise and consistent database was available to perform the statistical analyses.
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The head measurements were statistically analyzed. Both, direct or indirect correlation of the
measurements have been considered. In a multidimensional analysis averages, maximal and minimal
values, scatter and percentage distribution were examined. As an example figure 6 shows the
examination of the measurements “Head apex to eye” and “Distance eye to chin” in correlation to
“Head circumference” and “Head height”. Comparing the two dimensions makes it clear, that the
distance head apex to eye is much more depending on “Head height” than the measurement distance
“Eye to chin” does.
Fig. 6. Correlation analysis of distance “Head apex to eye” to “Head circumference” and “Head height”
Head circumference” is the basic measurement and determines the head size. Primary
measurements as “Head breadth”, “Head depth” and “Head height” are correlated to “Head
circumference”. They are the foundation for defining head types. As a first step head types of the
population were identified. Most important indicator was “Head breadth” and “Head depth”. The
correlation to head circumference answers question about head shape characteristics. Figure 7
illustrates the evaluation of the correlation of “Head breadth” and “Head circumference”.
Fig. 7. Correlation “Head breadth” vs. “Head circumference” – men and women
The scatter diagram shows the correlation of both dimensions for men and women. The red dots
represent female subjects and the blue dots represent male subject. The black trend line shows the
clear correlation between the two measurements. Obviously men and women do have a similar “head
circumference to head breadth ratio”. This indicates similar head forms with the same “Head
circumference”. This could be confirmed by the following research results. Furthermore, the scatter
diagram shows the variance of the dimension head breadth. For example, head circumference 58
presents a range of 3.4 cm. The statistical analyses in combination with the 3D form analyses of the
individual heads are the foundation of the head type definition (see chapter 3.2).
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2.5 Generating virtual 3D head models
3D head models were created on base of the statistical analyses of the head measurements as well as
on the 3D shape analyses. These models give the maximum coverage in regard of the variance. The
3D models correlate with the new developed sizing charts. Utilizing software Geomagic Studio 2012
scans were edited and shaped. The methodical approach was as follows: 3D scans of a specific size
cluster are chosen. Parameters were head circumference, breadth, depth, height and further
secondary measurements. Scan data (point cloud) was edited and converted into a polygon model. On
this basis the average heads were calculated. They were edited and shaped to create watertight
surface models. In the process, the acceptable degree of idealization had to be determined and
checked. Finally, a verification and adjustment of the average 3D head shapes related to the sizing
chart were performed.
2.6 3D Helmet fitting
A 3D based method for helmet fitting was developed based on virtual comparing of head and helmet
form. Necessary condition is the digitalization of the helmets by scanning technology. Virtually the
helmet can be donned on the head by 3D software Geomagic - individual scans as well as average 3D
models may be used. Analyzing cross sections and executing 3D distance analyses allows examining
possible fitting problems.
3. Results and Discussion
3.1 Percentage distribution of head sizes
Figure 8 shows the size distribution of 2970 male and 1890 female subjects with an age range from 18
to 85 years.
Fig. 8. Market shares - men and women
Evaluation was performed with adjusted head circumference values reduced by correction factor 1.7 %
(see chapter 2.2). The bar diagram illustrates the most important market shares. For men the major
part is at head circumference 58 and 59 cm. Women have smaller heads in average. The major part
for female subjects is at head circumference 55 and 56 cm. The smallest measured head
circumference was 52 cm and the biggest was 68 cm. These sizes are rather marginal but they show
the complete range of sizes needed for head protection systems.
The percentage size distribution of boys (n=800) and girls (n=520) is shown in figure 9 and 10. Age
range is between 6 and 17 years. Similar to the evaluation of the adult subjects the correction factor
was considered and applied. The bar diagrams illustrate that it is of great importance to differentiate
between the age groups.
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Fig. 9. Percentage distribution according to head circumference in each age group – boys
Fig. 10. Percentage distribution according to head circumference in each age group – girls
3.2 Definition of head types
The parameters to determine the head shape are head breadth and depth. The statistical evaluation of
the two measurements indicated that five head types are needed to cover the wide range of shapes
(see figure 11). Between the head types “Head breadth” increases 0.8 cm and “Head depth” increases
0.4 cm. The five head types allow best market coverage with well-fitting products. If helmet shapes are
more flexible, the scale of values can be easily adapted, e.g. for double sizes.
Fig. 11. Visualization of cross sections of the 5 defined head types - men
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Head type normal covers 63 % of the male population and 62.5 % of the female population.
Nevertheless, 37 % or 37.5 % of prospective clients do have other head types and need helmet
shapes matching to their specific geometry.
Besides head breadth and depth the height of the head is another important primary measurement.
“Head height” has an impact on the evaluation and cluster formation of any other head length, e.g.
“Distance head apex to eye”. First, range of “Head height” was analyzed. Men’s cluster showed 8 cm
differences and women’s cluster showed 7.2 cm differences in maximum. Five head height types with
2 cm differences were defined (see Figure 12).
Fig.12. Five head height types
In contrary to breadth and depth, “Head height” values of men and women differ. Female subjects
show on average 0.5 cm shorter “Head height” than male. The head height type normal covers 58.2 %
of the male market. Yet, the types short and long are not at all niche market. Each of them has a share
of almost 20 %. Market shares for female customers show similar distribution: 60.8 % type normal,
almost 20 % share for type short and long. Head types extra short and extra long are rather marginal
but they show the complete range of head heights.
3.3 Sizing charts for head and face measurements
Findings of statistical analyses were combined in a new sizing system. A sizing chart including 14 head
and face measurements was developed. Figure 13 presents an extract of the sizing chart with “Head
breadth” and “Cranial base width”.
Fig.13. Extract of the sizing charts – “Head breadth” and “Cranial base width”
size
ty pe
Head breadth oval extrem 12.4 12.6 12.8 13.1 13.3 13.5 13.7 14.0 14.3 14.5 14.7 14.9 15.2 15.5 15.7 15.9 16.2
oval 13.2 13.4 13.6 13.9 14.1 14.3 14.5 14.8 15.1 15.3 15.5 15.7 16.0 16.3 16.5 16.7 17.0
normal 14 14.2 14.4 14.7 14.9 15.1 15.3 15.6 15.9 16.1 16.3 16.5 16.8 17.1 17.3 17.5 17.8
round 14.8 15 15.2 15.5 15.7 15.9 16.1 16.4 16.7 16.9 17.1 17.3 17.6 17.9 18.1 18.3 18.6
round extrem
15.6
15.8
16
16.3
16.5
16.7
16.9
17.2
17.5
17.7
17.9
18.1
18.4
18.7
18.9
19.1
19.4
63 6457 58 59 60 61 6248 49 50 51 52 53 54 55 56
size
ty pe
Crania l Base W idth oval extrem 13.1 13.3 13.5 13.7 13.9 14.1 14.3 14.5 14.7 14.9 15.1 15.3 15.5
men oval 13.6 13.8 14.0 14.2 14.4 14.6 14.8 15.0 15.2 15.4 15.6 15.8 16.0
normal 14.1 14.3 14.5 14.7 14.9 15.1 15.3 15.5 15.7 15.9 16.1 16.3 16.5
round 14.6 14.8 15.0 15.2 15.4 15.6 15.8 16.0 16.2 16.4 16.6 16.8 17.0
round extrem
15.1
15.3
15.5
15.7
15.9
16.1
16.3
16.5
16.7
16.9
17.1
17.3
17.5
Crania l Base W idth oval extrem 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6 14.8 15.0
women oval 13.1 13.3 13.5 13.7 13.9 14.1 14.3 14.5 14.7 14.9 15.1 15.3 15.5
normal 13.6 13.8 14.0 14.2 14.4 14.6 14.8 15.0 15.2 15.4 15.6 15.8 16.0
round 14.1 14.3 14.5 14.7 14.9 15.1 15.3 15.5 15.7 15.9 16.1 16.3 16.5
round extrem
14.6
14.8
15.0
15.2
15.4
15.6
15.8
16.0
16.2
16.4
16.6
16.8
17.0
Crania l Base W idth oval extrem
boys oval 12.1 12.3 12.5 12.7 12.9 13.1 13.3 13.5 13.7 13.9 14.1 14.3 14.5 14.7
normal 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6 14.8 15.0 15.2
round 13.1 13.3 13.5 13.7 13.9 14.1 14.3 14.5 14.7 14.9 15.1 15.3 15.5 15.7
round extrem
Crania l Base W idth oval extrem
girls oval 11.6 11.8 12.0 12.2 12.4 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2
normal 12.1 12.3 12.5 12.7 12.9 13.1 13.3 13.5 13.7 13.9 14.1 14.3 14.5 14.7
round 12.6 12.8 13.0 13.2 13.4 13.6 13.8 14.0 14.2 14.4 14.6 14.8 15.0 15.2
round extrem
63 6457 58 59 60 61 6248 49 50 51 52 53 54 55 56
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Similarities and measurement differences between age groups and sex were identified and reflected in
the chart. The charts include five head types – oval extreme, oval, normal, round, extra round – as well
as five head heights – extra short, short, normal, long, extra long. The size range starts at size 48 and
ends at size 64. Adult head circumference range is from 52 to 62 cm, children’s circumferences range
from 48 to 60 cm. The sizing charts for adults represent the complete age range. Regarding primary
measurements “Head breadth” and “Head depth”, this applies for children, too. Values are covering
grown-ups as well as infants. Measurement differences between children and adults are minimal and
range from 1 to 3 mm. For that reason, it was not considered useful to develop a specific children’s
chart. Thus, secondary measurements hat to be described separately.
3.4 Representative 3D head models
Following, the generated virtual average 3D heads are illustrated. They are representing and
visualizing the measurements of the new developed sizing chart. Figure 14 shows men’s heads in type
normal and sizes 56, 58, 60 and 62. Figure 15 is visualizing men’s head types oval extreme, oval,
normal, round and round extreme in size 58. The average female heads in figure 16 are type normal
and in sizes 54, 56 and 58. In figure 17 average boys’ heads in type normal in sizes 52, 54, 56 and 58
are presented.
Fig.14. Representative 3D head models men – sizes 56, 58, 60 und 62 – head type normal
Fig. 15. Representative 3D head models men – size 58 – head types oval extreme, oval, normal, round, round extr.
Fig. 16. Representative 3D head models women – sizes 54, 56, und 58 – head type normal
Fig. 17. Representative 3D head models boys – sizes 52, 54, 56, und 58 – head type normal
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3.5 Fitting results
Finally, the ergonomic comfort of helmets was analyzed. The distance gaps between head geometry
and real helmet inside by using 3D scanning technology were evaluated. This method allows the virtual
testing of helmet fitting based on head measurements and 3D head shape models. Figure 18 shows
two 3D fitting analyses with individual head scans utilizing Geomagic Studio 2012. On the left a
well-fitting helmet is illustrated. Cross section shows good form accordance. There is only marginal
penetration of the textile inner lining which is compressed by the subjects head. The result is confirmed
by transparent presentation of helmet on subjects head scan. On the right side an ill-fitting helmet is
presented. Cross sections show clear penetration of inner lining. The visualization of the transparent
helmet on the subject confirms the finding.
Fig. 18. Example for 3D helmet fit analysis – well and ill-fitting helmet
Further research is needed on virtual fitting analyses. In addition, objective and reproducible textile
parameters regarding deformability of inner linings as well as information of pressure zones on the
human head are required to obtain profound fitting results.
4. Conclusions
The results of the scientific research provide fundamental product developing guidelines which
correspond to customer’s requirements. [18] Head measurements and 3D virtual models give
comprehensive geometrically information for optimized product development. The present engineer
standards can be adapted to the state-of-the-art.
With the development of the head sizing charts providing size related head data a foundation is given
to produce optimized helmet fit for differing head types. On the basis of a representative sample
market shares with optimal coverage were identified. Analyses showed that largest source of failures
are human hair. Varying hair volume leads to differences in head measurements regardless of
measurement technic. These deviations are unavoidable. In addition, hair influences helmet fit and
wearing comfort. Further research is needed.
The statistical analyses of children’s head measurements indicated that some differences in face
dimensions are growth-related. Head and face proportions are significantly changing with cranium
growth. While the upper part of head is changing only a little, the lower facial part is changing
significantly. This could not be completely presented within this limited space. In regard of the face
measurements further clusters in age groups are necessary.
Acknowledgment
The IGF project 16976 N by the research association Forschungskuratorium Textil e.V.,
Reinhardtstraße 12-14, 10117 Berlin, is financed through the AiF within the framework of the program
for promotion of cooperative industrial research (IGF) by the German Federal Ministry for Economic
Affairs and Energy based on a resolution by the German Bundestag.
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... Designers seek morphological data to help them define shapes, first of the segment and eventually of the related object (Morlock et al., 2016). These data are either rare or of limited use because they are associated with particular populations for whom the morphology may be specific. ...
... Development. The production of new data will always be useful, but needs are constantly evolving; the data deemed useful sometimes need to be very precise and specific (e.g., hair thickness for helmet use; Morlock et al., 2016). We need to develop tools to assist in the production of data, and include them in the toolbox for practitioners, as proposed by Liu et al. (2008). ...
... Designers seek morphological data to help them define shapes, first of the segment and eventually of the related object (Morlock et al., 2016). These data are either rare or of limited use because they are associated with particular populations for whom the morphology may be specific. ...
... Development. The production of new data will always be useful, but needs are constantly evolving; the data deemed useful sometimes need to be very precise and specific (e.g., hair thickness for helmet use; Morlock et al., 2016). We need to develop tools to assist in the production of data, and include them in the toolbox for practitioners, as proposed by Liu et al. (2008). ...
... For many years now, 3D scanning technology has brought benefits in the area of ergonomic design of protection devices. Contemporary research mostly concentrates on rendering the shape of the human body with the aim of improving the fit of PPE [14][15][16][17][18][19] as researchers determine the so-called internal dimensional allowances to improve the fit of PPE in accordance with the anthropometric traits of individual users. ...
Full-text available
Article
The article describes the importance of dimensional allowances, which are a consequence of the use of personal protective equipment (PPE) for work safety. The method of 3D scanning was proposed for determining the dimensional allowances which has been preliminary validated. Two geometric solids (a cylinder and a cuboid) were used to approximate the minimum space around the person using PPE. The solids are a simplified representation of the silhouette of a human subject performing activities in a confined work environment. They also correspond to the typical shapes of access openings and confined spaces, reflecting the real working conditions of welders, firefighters, mine rescuers, and other rescue teams. A detailed analysis of dimensional allowances for a full welding PPE set is provided. Based on the adopted parameters: the dimensions of the body, the base area and the volume, the differences in the dimensions of the body of a person dressed in underwear and in PPE were compared. The results of the presented studies indicate a significant role of dimensional allowances in interactions between persons wearing PPE and the work environment. The results are planned to be implemented in a new anthropometric atlas of human’s measures used for ergonomic design.
... Fit is an important parameter to consider when designing protective equipment, and morphological differences have been shown to greatly affect fit. 9,10 Anecdotally, headgear and facial wear (glasses, oxygen masks, hel- mets, etc.) have been known not to fit the East-Asian population when designed by European and North American companies. Ball and colleagues 11 wanted to investigate the morphological differences between the Chinese population and European Caucasians. ...
Article
Ice hockey helmets must pass standardized impact tests to be certified for sale. However, these tests are performed with the helmet attached to a surrogate headform. Human head shapes are not uniform, and very few standards exist for helmet fitting for the common user. The goal of this study was to develop an accurate and cost-effective three-dimensional acquisition protocol to assess the geometric fit of human subject heads to a variety of ice hockey helmets. The study had three main objectives: First, a photogrammetry-based three-dimensional acquisition system was developed. Second, the researchers populated a database of both male human heads and ice hockey helmets by scanning five different helmet models from various manufacturers. Finally, the system accuracy and error were calculated using root mean squared errors between the dimensional difference curves of repeated scans. Errors were calculated by repeating the entire protocol error with 20 comparisons (root mean squared error = 2.83 mm), the alignment error with 5 comparisons (root mean squared error = 1.14 mm), and scaling error with 4 comparisons (root mean squared error = 1.84 mm). Suggestions are provided in the section “Discussion” on how to create a system that is more time efficient with higher resolution renders and lower error. A method that quantifies three-dimensional fit is the first step toward studying the relationship between helmet fit and user-specific helmet protection.
Full-text available
Conference Paper
In product design, human body measurements are essential when it comes to products that need to fit the contour of the human body in order to be effective. When designing these products, designers must integrate anthropometric dimensions in their design process to optimize the usability and functioning of the product. In spite of the wide variety of available anthropometric tools, designers most commonly use traditional (1D) anthropometric information when designing and evaluating products. This does not always offer the detailed information of the human body shape required to develop a product with an optimal fit. This is especially the case for medical products such as respirators and orthesis, but also in consumer products, such as helmets and protective glasses. 3D anthropometry however, creates a significant opportunity for designers by offering detailed information regarding the shape of the human body. Advances in 3D imaging technologies have reinforced these possibilities in the field of anthropometry. With the use of these technologies, it is possible to capture a complete 3D image of the whole body in a matter of seconds, making the measurement process less invasive and therefor more suitable for populations that are difficult to measure with traditional means like children, elderly and physically impaired persons. The objective of this study is to map the variation of children's heads and faces and to define a new way to present this 3D anthropometric data so that it is tailored for use in design. For the first stage of this study, an anthropometric survey was conducted, whereby the heads and faces of children between the ages of 0.5 to 7 years old were analysed. Around 300 boys and girls were measured combining traditional anthropometric measurements with measurements derived from 3D images. All subjects were photographed using a digital three-dimensional photogrammetry system (3dMD Face imaging system). This paper presents the preliminary 3D data set of the heads and faces of children aged 0.5-7 years for design applications and shows the summary statistics for some of the traditional anthropometric measurements.
Full-text available
Conference Paper
In order to design products that will interact with head and face, engineers need to build a solid knowledge about their target customer’s morphology. Classical methods allow only a definition of different size groups derived from specific 2D anthropometric measurements such as head girth, bizygoma-tic breadth, mouth breadth … (Snyder 1978 [2]). Acquiring 3D geometry is another method that is being used increasingly for the past 20 years. From Bradtmiller in 1993 [3] to Mochimaru in 2008 [8], 3D scans offer the possibility to carry a full analysis of morphological details. Indeed, using 3D point clouds instead of classical 2D anthropometric measurements allows taking into account the curvature variations in specific areas such as cheek or chin. Some methods are using mathematical functions (Biasotti 2008 [7]), others are working with an analogous 3D model associated with anatomical landmarks (Mochimaru 2008 [8] ; Ma 2005 [6]). Most of those methods are trying to classify population into size groups which are based on global 3D variations such as depth, width and height of the model. Those groups are then represented with average 3D model (Kouchi 2004 [5]). Our goal here is to compute a simple and standardized method for analysing head and face morphology. It had to give results that directly take into account more details than just global dimension variations through an average 3D model and that could be directly usable to validate the right interface geometry of a computer aided designed product. The sample population was composed of 51, 15 to 47 year old women and 64, 16 to 55 year old men. The digitalisation was performed using a Konica Minolta VI-910 laser scanner. Every subject’s face was digitalized using three automatically registered views. The reconstructed scanned faces were then oriented along a reference plane computed from 3 anatomical landmarks (Projection of the Nasion on the face’s symmetry plane, Mental protuberance and Exocanthion). The same plane was then used to extract parallel level curves of the face (Figure 1). After normalizing all the curves in polar coordinates, every mean level curve was calculated on our scanned population. Using the whole population, we manage to compute a mean 3D face mapped with the geometric standard deviation (STD) (Figure 8). This preliminary result is a first step toward an easy face / product interface design for manufacturers as it provide them with the zone of less significant morphology disparity (The green zones). However, the use of a common reference point was necessary to register every face of our sample, and moving this point to another location changed the global standard deviation mapping - which is easily explained by a null STD at that point -. The anatomical landmark picking required (in this method) are also a source of inaccuracy. In order to avoid those two main limits, further work is necessary to use an automatic registration and spherical normalisation (allowing not working with a reference point and landmarks). Finally, this method should be validated in regard to traditional anthropometric methods (2D measurements).
Article
The present research sought to apply underlying principles that determine helmet fit to develop a scientific design method for determining the minimum number of helmet sizes to accommodate the full anthropometric variability of the population. The method was tested on a prototype helmet concept using a stratified sample of males and females drawn to represent the Joint Strike Fighter population. Asian- and African American subjects were specifically included in order to examine the effects of racial anthropometric variability on fit. While the ranges of accommodation for the initial design was broad, it encompassed only a portion of subjects who fell within the 99% probability ellipse, best meeting the fitting needs of a very small subset of the population. Applying a fit mapping method determined that two helmet sized, sized and shaped differently than those initially proposed and with a modified fitting concept, would accommodate 99% of both males and females. The fit mapping process also provided specific, quantified feedback to the designers on size and shape modifications needed to make the helmet to provide better fit for the full range of the population. Determining the parameters that link anthropometric principles to fit of a specific piece of equipment permit design modifications to equipment to be made early in the design process using only a single size prototype, resulting in fewer sizes while ensuring accommodation of the desired population.
Article
A method used to determine the probable population accommodation of a helmet sizing system is described. The method involves the use of 3D laser scanning, as a means of measuring helmet standoff distance (distance between the inside of the helmet and the skull), and the selection of a representative sample of test subjects. The laser scanner and the software developed to calculate standoff distance proved to be an excellent tool for the assessment of helmet fit. The main advantages include ease of use and visualization of problem areas. This 3D-analysis method gives designers objective evidence of the need for design changes as well as an idea of what these changes should be. A comparison was made between standoff distance results obtained from the scanner and those obtained using a physical measurement method (a probe). Although discrepancies were found between the two, sources of errors intrinsic to both methods make it difficult to determine which of the two methods yielded the truest standoff distance. Analysis of the comparison data shows laser scanning to be slightly more conservative than the probe method for standoff distance purposes, i.e. erring on the side of safety.
Article
Sizing data generated by the military for use in fitting respirators have been the normative basis for commercial respirator sizing. Anthropometric data developed for males and females of military age in the 1950s and 1960s are still in use today and form the only comprehensive body of information available on this subject. The twofold objective of this study was to: (1) develop an anthropometric database detailing the face size distributions of respirator users using both traditional measurement methods and three-dimensional scanning systems; and (2) use the database to establish fit test panels to be incorporated into the National Institute for Occupational Safety and Health's respirator certification and international standards. A stratified sampling plan was used with three age strata, two gender strata, and four race/ethnic group strata. The plan called for an equal sample size of 166 in each cell. Subjects were obtained at 41 sites from 8 states. In addition to height and weight, 18 facial dimensions and neck circumferences were measured using traditional methods. A total of 3997 subjects were measured using traditional methods, and 1013 of them were also scanned using a 3-D head scanner. As this was a volunteer sample, subjects did not appear in the specific proportions needed for the sampling plan. The resulting data were weighted to correspond to the U.S. population. This article presents the summary statistics for the traditional measurement data only. Multivariate analyses of the data from this study and military data revealed that using historical, military data would be inadequate for describing the anthropometric variability of the current U.S. work force.
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CAESAR -The most comprehensive source for body measurement data
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Grundsatzuntersuchung zur Optimierung textilbasierter Kopfschutzsysteme
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S. Morlock, M. Harnisch, H. Mucha, "Grundsatzuntersuchung zur Optimierung textilbasierter Kopfschutzsysteme", IGF 16976 N, Hohenstein Institut für Textilinnovation gGmbH, Boennigheim, Germany, 2014
Grundsatzuntersuchung zur Konstruktion passformgerechter Bekleidung für Frauen mit starken Figuren
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Sizing trials of a prototype aircrew helmet: Lessons re-learnt
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