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- Bohlin, Robert, et al.
(författare)
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Unified solution of manikin physics and positioning - Exterior root by introduction of extra parameters
- 2011
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Ingår i: Proceedings of DHM, First International Symposium on Digital Human Modeling. - : Université Claude Bernard Lyon. - 9782953951509
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Konferensbidrag (refereegranskat)abstract
- Simulating manual assembly operations considering ergonomic load and clearance demands requires detailed modeling of human body kinematics and motions, as well as a tight coupling to powerful algorithms for collision-free path planning. The focus in this paper is kinematics including balance and contact forces, and ergonomically preferable motions in free space. A typical manikin has more than 100 degrees of freedom. To describe operations and facilitate motion generation, the manikin is equipped with coordinate frames attached to end-effectors like hands and feet. The inverse kinematic problem is to find joint values such that the position and orientation of hands and feet matches certain target frames during an assembly motion. This inverse problem leads to an underdetermined system of equations since the number of joints exceeds the end-effectors' constraints. Due to this redundancy there exist a set of solutions, allowing us to consider ergonomics aspects and maximizing comfort when choosing one solution.The most common approach to handle both forward and inverse kinematics is building a hierarchy of joints and links where one root must be defined. A popular place to define the root is in a body part, e.g. in a foot. This leads to a two-step procedure; (i) one level determining when to re-root when moving the root part, (ii) then the Penrose pseudoinverse is used to match the end-effectors' constraints.In this paper we propose using a fixed exterior root by introducing six additional parameters positioning the lower lumbar - three rotations and three translations. This makes it possible to reposition the manikin without a series of re-rooting operations. Another important aspect is to keep the manikin, affected by internal and external forces and moments, in balance. However, by utilizing the exterior root and its added degrees of freedom it is possible to solve the balance, positioning, contact force and comfort problems simultaneously in a unified way. A manikin was implemented, and two test cases demonstrate the applicability of the presented method.
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- Brolin, Erik, 1984-, et al.
(författare)
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Development of body shape data based digital human models for ergonomics simulations
- 2022
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Ingår i: Proceedings of the 7th International Digital Human Modeling Symposium (DHM 2022), August 29–30, 2022, Iowa City, Iowa, USA. - : University of Iowa Press. - 9780984037841 ; , s. 1-9
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Konferensbidrag (refereegranskat)abstract
- This paper presents the development of body-shape-data-based digital human models, i.e. manikins, for ergonomics simulations. In digital human modeling (DHM) tools, it is important that the generated manikin models are accurate and representative for different body sizes and shapes as well as being able to scale and move during motion simulations. The developed DHM models described in this paper are based on body scan data from the CAESAR anthropometric survey. The described development process consists of six steps and includes alignment of body scans, fitting of template mesh through homologous body modeling, statistical prediction of body shape, joint centre prediction, adjustment of posture to T-pose, and, finally, generation of a relation between predicted mesh and manikin mesh. The implemented method can be used to create any type of manikin size that can be directly used in a simulation. To evaluate the results, a comparison was done of original body scans and statistically predicted meshes generated in an intermediary step, as well as the resulting DHM manikins. The accuracy of the statistically predicted meshes are relatively good, even though differences can be seen, mostly related to postural differences and differences around smaller areas with distinct shapes. The biggest differences between the final manikin models and the original scans can be found in the shoulder and abdominal areas, in addition to the significantly different initial posture that the manikin models have. To further improve and evaluate the generated manikin models, additional body scan data sets that include more diverse postures would be useful. DHM tool functionality could also be improved to enable evaluation of the accuracy of the generated manikin models, possibly resulting in DHM tools that are more compliant with standard documents. At the same time, standard documents might need to be updated in some aspects to include more three-dimensional accuracy analysis.
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- Delfs, Niclas, et al.
(författare)
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Automatic Creation of Manikin Motions Affected by Cable Forces
- 2014
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Ingår i: Procedia CIRP:CIRP Conference on Assembly Technologies and Systems, CATS 2014; Dresden; Germany; 12 May 2014 through 14 May 2014. - : Elsevier BV. - 2212-8271. ; 23, s. 35-40
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Konferensbidrag (refereegranskat)abstract
- Effective simulation of manual assembly operations considering ergonomic load and clearance demands requires detailed modeling of human body kinematics and motions, including balance and response to external forces.In this paper we address the interaction of humans with flexible objects. By incorporating detailed physics simulation of flexible objects into the creation of ergonomically feasible human motions, we are able to ergonomically assess manual assembly operations involving cables and hoses.The method is implemented and demonstrated on a challenging operation taken from the automotive industry; a wiring harness assembly.
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- Delfs, Niclas, et al.
(författare)
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Introducing Stability of Forces to the Automatic Creation of Digital Human Postures
- 2013
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Ingår i: 2nd International Digital Human Modeling.
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Konferensbidrag (refereegranskat)abstract
- Although the degree of automation is increasing in manufacturing industries, many assembly operations are performed manually. To avoid injuries and to reach sustainable production of high quality, comfortable environments for the operators are vital. Poor station layouts, poor product designs or badly chosen assembly sequences are common sources leading to unfavorable poses and motions. To keep costs low, preventive actions should be taken early in a project, raising the need for feasibility and ergonomics studies in virtual environments long before physical prototypes are available. Today, in the automotive industries, such studies are conducted to some extent. The full potential, however, is far from reached due to limited software support in terms of capability for realistic pose prediction, motion generation and collision avoidance. As a consequence, ergonomics studies are time consuming and are mostly done for static poses, not for full assembly motions. Furthermore, these ergonomic studies, even though performed by a small group of highly specialized simulation engineers, show low reproducibility within the group.Effective simulation of manual assembly operations considering ergonomic load and clearance demands requires detailed modeling of human body kinematics and motions as well as a fast and robust inverse kinematics solver. In this paper we introduce a stability measure rewarding poses insensitive to variations in contact points and contact forces. Normally this has been neglected and only the balance of moment and forces has been taken into account. The manikin used in this work has 162 degrees of freedom and uses an exterior root. To describe operations and facilitate motion generation, the manikin is equipped with coordinate frames attached to end-effectors like hands and feet. The inverse kinematic problem is to find joint values such that the position and orientation of hands and feet matches certain target frames during an assembly motion. This inverse problem leads to an underdetermined system of equations since the number of joints exceeds the end-effectors’ constraints. Due to this redundancy there exist a set of solutions, allowing us to pick a solution that maximizes a scalar valued comfort function. Many objectives are included in the comfort function, for example in terms of joint angles, joint moments and solid objects’ distance to the manikin. The proposed stability measure complements the earlier balance criterion and is combined into the comfort function. By increasing the importance of this function the digital human model will reposition to a more stable pose. The digital human model will be tested on a set of challenging assembly operations taken from the automotive industry to show the effect of the stability measure.
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- Hanson, Lars, et al.
(författare)
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Design concept evaluation in digital human modeling tools
- 2022
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Ingår i: Proceedings of the 7th International Digital Human Modeling Symposium (DHM 2022), August 29–30, 2022, Iowa City, Iowa, USA. - : University of Iowa Press. - 9780984037841 ; , s. 1-9
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Konferensbidrag (refereegranskat)abstract
- In the design process of products and production systems, the activity to systematically evaluate initial alternative design concepts is an important step. The digital human modeling (DHM) tools include several different types of assessment methods in order to evaluate product and production systems. Despite this, and due to the fact that a DHM tool in essence is a computer-supported design and analysis tool, none of the DHM tools provide the functionality to, in a systematic way, use the results generated in the DHM tool to compare design concepts between each other. The aim of this paper is to illustrate how a systematic concept evaluation method is integrated in a DHM tool, and to exemplify how it can be used to systematically assess design alternatives. Pugh´s method was integrated into the IPS software with LUA scripting to systematically compare design concepts. Four workstation layout concepts were generated by four engineers. The four concepts were systematically evaluated with two methods focusing on human well-being and two methods focusing on system performance and cost. The result is very promising. The demonstrator illustrates that it is possible to perform a systematic concept evaluation based on human well-being, overall system performance, and other parameters, where some of the data is automatically provided by the DHM tool and other data manually. The demonstrator can also be used to evaluate only one design concept, where it provides the software user and the decision maker with an objective and visible overview of the success of the design proposal from the perspective of several evaluation methods.
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