An online ergonomic evaluator for 3D product design

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been applied to guide the design of hand tools,
furniture, and other consumer products [31,32]. The
latter is focused on analyzing the action angles,
trajectories, and reaching spaces of the body parts
under specified human motions. It contributes to the
design of work environment, machines, production
lines, and other occupational equipments [33,34].
Ergonomic assessment for the car interior design
mainly concerns static anthropometry. In this study, a
digital model is constructed with a local anthropometry
database in Taiwan [35], which serves as a
complete data source for characterizing the 3D human
body of both male and female adults in the country.
This human model can be customized according to
different body sizes chosen by the user. The
customization is performed based on the template
approach [36] previously developed in which human
models at different scales are controlled by a set of
anthropometrical parameters. The design of this
anthropometry database follows three important
guidelines: (1) design for extreme individuals, (2)
design for adjustable range, and (3) design for average.
2.4. Posture generation
The digital human can be placed in a set of postures
that are recognized in a motion capturer and modeled
with the captured data [37]. The human motion is
comprised of a set of rigid parts connected by joints,
referred to as a human template, as shown in Fig. 1.A
different human template is generated from each
anthropometry data set that corresponds to a specific
C.-F. Kuo, C.-H. Chu / Computers in Industry 56 (2005) 479–492
percentage of the body size. These rigid parts are
allowed to rotate and translate with respect to the
connected joints under biomechanical constraints.
Complex and realistic postures are thus created with
minimal user’s interactions. Moreover, compounding
homogeneous transformations are applied to generate
the postures of body extremity [38]. For instance, the
posterior segments, like wrist’s final position, are
determined by a series of the anterior segment’s
rotations including forearm, upper arm, and torso.
Note that the use of the human templates helps a nonskilled
designer easily create realistic character
postures by learning only a small set of key
parameters.
2.5. Posture evaluation
The mechanism for the posture evaluation is based
on a musculoskeletal load assessment method
proposed by Chaffin and Baker [39]. This twodimensional
static sagittal model (see Fig. 2) divides
human body into seven major parts [40]. The
dimensions of each part are collected and stored in
the anthropometric database. Ignoring the influence of
inertia, we compute the angle of each joint and
combine the result with the dimensional data. In the
posture assessment, the focus is on shoulder, elbow,
wrist, hip, knee, and toe. The relative positions
between important body points and the product are
Fig. 1. 3D human template based on motion capture data. Fig. 2. Chaffin’s biomechanical model [39].