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Journal Article

Optimization-Based Grasp Posture Generation Method of Digital Hand for Virtual Ergonomics Assessment

2008-06-17
2008-01-1902
Automatically generating humanlike grasp postures of the digital hand is a key issue for the virtual ergonomic assessment of the industrial products. In this paper we propose a new optimization-based approach for generating the realistic grasp posture. As an objective function, we use the number of the contact points, the fit of the specific part of the hand surface for the feature edges of the product surface and the margin for the constraints on the joint angle limits of the figures. The experimental studies on the grasp posture generation for the digital camera indicate that more realistic grasp posture could be generated using the proposed optimization-based method than the one using our former method.
Technical Paper

Motion Distribution Map of Ingress to Driver's Seats

2007-06-12
2007-01-2506
This paper proposes a method for analyzing the ingress motions for different driver's seats. Because of the multiplicity of possible ingress strategies, a unique motion calculated by minimization of energy consumption is not sufficient for understanding the variety of motions. In addition, during ingress the human body is supported by the hand placed on the steering wheel, the legs move without collision with the side sill, and the head avoids the roof rail. Consequently, difficulty is expected in constructing a computational dynamics model for this complex motion that is sufficiently precise to predict human behavior. In order to understand ingress behavior without a detailed physical model of human motion, we utilize a motion distribution map based on the degree of similarity between motions.
Technical Paper

Generation and Validation of 3D Links for Representative Hand Models

2007-06-12
2007-01-2512
This paper proposes a method for constructing a three-dimensional (3D) link model of a representative hand model, and to change its posture. The link data were derived using bone mesh models extracted from MR (magnetic resonance) images of 18 subjects. The length of each link was estimated by stepwise multiple regression analysis of 98 hand measurements. A 3D link for the representative hand model was generated by deforming the generic hand model using the estimated link length. The proposed method was validated by constructing models for six actual subjects. Link lengths and the distances between salient points were compared.
Technical Paper

Virtual Ergonomic Assessment on Handheld Products based on Virtual Grasping by Digital Hand

2007-06-12
2007-01-2511
The purpose of this research is to develop a system for virtual ergonomic assessment of products without real subjects and physical mockups by integrating a digital hand model with a product model. In previous work, we developed functions of a semi-automatic grasp planning for the digital hand and of quantitatively evaluating the grasp stability of the product based on the force-closure and the grasp quality in our system. We also confirmed the validity of the results from these functions by comparing them with the real grasp postures. However, only evaluating the grasp stability could not necessarily derive the appropriate grasp postures. To solve this problem, in this paper, we propose a new function of evaluating “ease of grasping (EOG)” for the grasp posture based on EOG-map constructed from principal component analysis for finger joint angles in real subjects’ grasps.
Technical Paper

Dhaiba: Functional Human Models to Represent Variation of Shape, Motion and Subjective Assessment

2006-07-04
2006-01-2345
Dhaiba (Digital Human Aided Basic Assessment system) is a visualization software platform implemented on VirTools®. This software integrates a whole body model (DhaibaMan) with functional centers of rotation for 17 joints, a detailed hand model (DhaibaHand) with 31 Degree of Freedom (DoF) and databases of anthropometry and motions. The platform supports the design of human-compatible products such as cell phones, packages and cars. Models of human motions with strategy differences, subjective assessment of usability, deformation and friction of fingertips will be integrated.
Technical Paper

Dhaibashoulder: A Scalable Shoulder Model for Accurate Reach Envelope using the Orbital Surface of the Functional Joint Center

2006-07-04
2006-01-2323
We have developed a generic model of the human shoulder named “DhaibaShoulder.” In order to generalize the shoulder model formed by the orbital surface of the center of rotation of the shoulder, we clarified relationships between: the position of the center of rotation in the torso coordinates system, the shape of the orbital surface, and the torso anthropometric data. Using these results, our shoulder model can deform in accordance with anthropometric data and can determine the center of rotation in proportion to the posture of the upper arm. If the model is applied to a digital manikin, an actual reach envelope is simulated more accurately than is possible with other commercial digital manikins.
Technical Paper

An Application of a Digital Hand to Ergonomic Assessment of Handheld Information Appliances

2006-07-04
2006-01-2325
Recently, as CAD systems have spread, style design with digital mockups has been used. But physical mockups are still used to evaluate the ergonomic design of products. However, the conventional methods of the evaluation using a physical mockup of a product are inefficient in an upstream style design process, for it takes time and money. So, our research purpose is to develop a system for ergonomics design, which enables ergonomic assessment for a handheld information appliance without “real” subjects and physical mockups by integrating a digital hand with a product model and its task operation model.
Technical Paper

Hand Link Modeling and Motion Generation from Motion Capture Data Based on 3D Joint Kinematics

2005-06-14
2005-01-2687
Characterization of the human hand motion necessary to manipulate hand-held equipment requires accurate capture and reconstruction of the arbitrary subject's hand motions with respect to the object. The present study used an individual link structure modeled from optical motion capture data to perform this task and compared the results against those obtained by medical imaging. Posture data was captured while grasping several cylinders, and the captured data were utilized to generate new postures to grasp cylinders of arbitrary diameter.
Technical Paper

Functional Shoulder Joint Modeling for Accurate Reach Envelopes Based on Kinematic Estimation of the Rotation Center

2005-06-14
2005-01-2726
We developed a new method to estimate the functional center of rotation of the shoulder joint. Using this method, we examined the relationship between the posture of the upper arm and the displacements of the estimated center of rotation of the shoulder joint. The displacements were calculated from the flexion-extension angle and abduction-adduction angle of the upper arm. In this study, we propose a shoulder model for digital manikins that simulates reach envelopes more accurately than that for the existing digital manikins.
Technical Paper

Estimation of Five Anatomical Landmarks on a Foot Model's Toes Based on Surface Shape

2005-06-14
2005-01-2730
We propose producing a body model consisting of anatomical landmarks used in product design from point clouds from a three-dimensional scanner. We previously proposed producing a foot model automatically by deforming the template of known landmarks using free-form deformation (FFD), but shapes of actual toe tips vary widely from the template. Here we propose extracting five landmarks on the toes of a foot model.
Technical Paper

Automatic Landmarking in 3D Human Head Scans

2005-06-14
2005-01-2731
We propose some methods to automatically estimate the position of orbitale and tragion from raw 3D scanner data. The 3D scanner captures point cloud and mesh data representing the body surface. To utilize the data, we also need underlying anatomical landmarks. The tragion position is estimated using three methods, by detecting the saddle shaped area, by setting an average position relative to ear robe, and by 3D template matching. Orbitale position is estimated by regression analysis using the position of eyes and subnasale as independent variables. The methods are tested and the results are compared using 20 Japanese head form data.
Technical Paper

An Analysis of Hand Measurements for Obtaining Representative Japanese Hand Models

2005-06-14
2005-01-2734
In order to create digital models representing the variation in hands of adult Japanese, 82 measurements were taken for 103 subjects using traditional methods. Factor analysis of the measurements was performed, and the first 2 factors were used to calculate measurements for 9 members of the boundary family. A 3D digital model was created for each family member by deforming a generic model by minimizing the total difference of 40 measurements between the generic model and the target hand model. The generic model with 36 degrees of freedom was created from medical images of a subject captured in 4 different posture.
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