General Assembly Process Research Articles

A knowledge-driven framework and methodology for precision assembly process decision making

Precision assembly process planning technology is one of the major challenges in the field of assembly. Compared with general assembly process planning, precision assembly process planning needs to consider a more complex assembly process, higher precision requirements, and more difficult process control. For this reason, it is of great significance to implement an intelligent assembly process planning and decision-making method for the development of precision assembly technology. This paper realizes the intelligent planning of precision assembly processes through the decision-making route of knowledge modeling and knowledge reasoning. Firstly, a theoretical system of a knowledge-driven precision assembly process decision-making framework is proposed. Secondly, a key precision assembly process decision-making technology is described in detail, which introduces a new approach for knowledge updates based on matching rules. Finally, the effectiveness of the knowledge update method is demonstrated through experimental cases. The knowledge-driven decision-making method combines the accuracy of domain experts’ empirical knowledge with the efficiency of intelligent reasoning algorithms. The knowledge update method ensures the currency of knowledge used for decision making. Therefore, the proposed precision assembly decision-making system framework and knowledge updating techniques in this paper are of great significance for knowledge-driven precision assembly process planning.

Semantic part segmentation of spatial features via geometric deep learning for automated control cabinet assembly

AbstractIndustries with batch size one manufacturing philosophies for highly customized products have been largely limited in manufacturing automation. The control cabinet industry is particularly affected by this problem during the mounting and wiring of components due to high variety, variance, and complexity of components as well as handling tasks. Rapid advances in the field of machine learning are opening new possibilities for automating previously manual processes. This paper proposes a concept for identifying geometric features of electrical components that starts from STEP files and transforms them into modular metrics relevant to build a digital twin and (automatic)manufacturing. The architecture is tested on a self-aggregated and processed dataset of control cabinet components and achieves an average dice score of 65.27% and an intersection over union of 51.41% across all segmentation classes. In addition to semantic part segmentation of the components, the cluster, volume and surface centroids, the normal vectors and the size of each feature are computed. The paper evaluates the suitability of cutting-edge techniques such as diffusion as well as established deep learning architectures. The result is a hybrid end-to-end inference pipeline suitable for general spatial assembly processes.

Workflow modelling for human–robot collaborative assembly operations

With the advent of Industry 4.0 , industries are requested to provide customisation of the products, with a high number of tailored features, which a pure robotic assembly line cannot provide. This suggests using a collaborative and flexible scenario together with the need for workflow modelling architectures. These can handle the communication and interaction among the actors of the workcell to improve the collaboration, making it more fluent, reliable, and able to correct workers’ oversights. Within this scenario, the main contribution of this paper is the introduction of a general library of atomic Predicates that can be combined with a first-order logic allowing to model general industrial assembly processes in human–robot collaboration. Such logics and Predicates allow to model and supervise the workflow, remaining hidden to the operator through an interface that intervenes only when errors have to be notified. The methodology has been validated on a complex collaborative assembly use case, requiring different tools and characterized by components of several sizes and shapes. Predicates have been mainly exploited to recognize human activities, allowing modelling and supervising the workflow. • Formalization of a library of predicates for human activity recognition. • Extension of an architecture to model and supervise assembly operations workflow. • Validation of the proposed methodology in a complex use case scenario.

Analysis on The Assembly Technology of Manned Spacecraft and Unmanned Spacecraft

The aerospace machine contains manned spacecrafts and spacecrafts by whether carrying the person. As an important moment, there are several characteristics between manned spacecrafts and spacecrafts in assembly process. The general assembly process is of vital importance in a spacecraft R&D system. It is at the bottom of the technical system of spacecraft manufacturing, and covers quality assurance, integrated scheduling and logistic controlling. First of all, this paper recommends the concept of the spacecraft assembly technology. And then this text introduces six aspects such as system complicated degree, the microorganism control, how to select nonmetal material, craft methods, transport methods, assembly mode to analyze the difference from spacecraft.

Intelligent configuring for agile joint jig based on smart composite jig model

Agile joint jig (AJJ) is a novel and promising reconfigurable assembly jig, which is put forward to deal with the disadvantages of traditional dedicated assembly jig in aerospace industry. For AJJ design, it is under the combined influence of aircraft product and assembly process requirements, especially the experience and knowledge of designers. Although case-based reasoning (CBR) gives the possibility to make fixture design more efficiently, this method has its weakness that the most similar case maybe is not the optimal selection and the designers still depend on their knowledge to determine what changes need to be made and how these changes can be achieved. In order to lower the requirement for designers’ skills and enhance the AJJ design efficiency, this paper presents an intelligent configuration method based on smart composite jig model (SCJM). Firstly, the concept and definition of SCJM are presented. It is not only a generic assembly jig architecture for a certain aircraft product family but also appends information and knowledge through MBD (model-based definition). Secondly, the requirement information model including product general information and assembly process information and so on is established with MBD for driving AJJ design automatically. Based on the above models, the intelligent configuration method for AJJ is proposed and realized by combing auto-selection reasoning with auto-assembly reasoning. The auto-selection reasoning is to achieve that the standardized components are selected actively by matching attributes between SCJM and product model. The auto-assembly reasoning is to automatically assemble the selected components in terms of the typical constraint relationships. By these ways, the SCJM can perceive the product assembly requirements by itself and then achieve appropriate design automatically. Finally, a computer-aided system for intelligent design of airplane assembly jig was developed. The results indicated that the proposed methods are able to significantly improve the design efficiency and quality of reconfigurable assembly jig.

Supramolecular Construction of Optoelectronic Biomaterials

Peptide self-assembly is a powerful method to create functional nanoscale materials such as optoelectronically relevant organic nanostructures. The enormous potential that may come from bringing π-conjugated electronic function into biological environments is poised to impact cell and tissue engineering, biosensors, and related biomedical applications. However, very little synthetic guidance is available with respect to uniting these two different materials sets in a generally applicable manner. In this Account, I describe my group's work to synthesize and assemble peptidic nanostructures built around organic electronic elements. The Account begins with a very brief background to the area of supramolecular electronics, followed by a description of areas where these nanomaterials could be useful in biology. I then discuss the synthetic approaches that we utilized to embed a variety of π-electron units directly within peptide backbones. A key supramolecular challenge with respect to subsequent self-assembly of these new molecules is balancing electrostatic contributions within the resulting nanomaterials, because the suitable geometries for stabilizing peptide assemblies may not necessarily correspond to those suitable for maximizing intermolecular π-electron interactions. Regardless of the respective magnitudes of these two major influences, the assembly paradigm is fairly robust. Variation of the π-electron units and the peptide sequences that make up the "peptide-π-peptide" triblock molecules consistently leads to fairly uniform tape-like nanostructures that maintain strong electronic coupling among the component π-electron units. We explored a diverse range of π-electron units spanning fluorescent oligo(phenylene vinylene)s, electron-accepting rylene diimides, and hole-transporting oligothiophenes. I then describe the characterization of the nanomaterials that form after molecular self-assembly in order to understand their internal structures, electronic interactions, and morphologies as existing within self-supporting hydrogel matrices. I also describe how a facile shearing process provided globally aligned macroscopic collections of one-dimensional electronic fibrils in hydrogel matrices. These general assembly processes influence intermolecular π-stacking among the embedded chromophores, and the assemblies themselves can facilitate the covalent cross-linking and polymerization (for example, of reactive diyne units). The latter offers an exciting possibility to create peptidic nanostructures comprised of single polymer chains. Finally, I discuss electronic properties as manifested in the interactions of transition dipoles within the nanomaterials and electrical properties resulting from field-effect gating. The ability to tune the observable electrical properties of the nanostructures externally will allow for their transition to in vitro or in vivo platforms as a powerful new approach to regulating biological interactions at the nanoscale.

Assessing spatial and environmental drivers of phylogenetic structure in Brazilian Araucaria forests

Evidence of phylogenetic conservatism in plant ecological traits has accumulated over the past few years, suggesting an interplay between the distribution of phylogenetic clades and major environmental gradients. Nonetheless, determining what environmental factors underlie the distribution of phylogenetic lineages remains a challenge because environmental factors are correlated with spatial gradients where the latter might indicate some degree of dispersal limitation in phylogenetic pools. We analyzed the phylogenetic structure of plant assemblages across the Brazilian Araucaria forests and assessed how phylogenetic structure responds to environmental and spatial gradients. We compiled data on plant occurrence in 45 plots across the Araucaria forest biome. The phylogenetic structure of the plots was characterized using phylogenetic fuzzy‐weighting followed by principal coordinates of phylogenetic structure (PCPS). We used distance‐based redundancy analysis (db‐RDA) to analyze the relationships between phylogenetic clades and environmental and spatial factors. Variation partitioning showed that the phylogenetic structure of Brazilian Araucaria forests was better explained by environment factors (altitude and annual mean temperature) than by space. Yet, spatially‐structured environmental variation explained about one‐third of total variation in the phylogenetic structure. Thus, the influence of spatial filters on the phylogenetic structure was more related to environmental gradients across the Brazilian Araucaria forest biome than to dispersal limitation of phylogenetic lineages. Furthermore, the influence of explanatory factors on the phylogenetic structure was concentrated in few nodes, the one splitting tree ferns from seed plants, and a second splitting malvids from other eurosids. Assessing the functional links between species distribution patterns and environmental gradients is not an easy task when we have to deal with large species pools. Identifying major phylogenetic gradients across an environmental and/or geographical range of interest can represent a first step towards a better understanding of general assembly processes in ecological communities.

Assembly Model Based on Dynamic Transition Graph for Satellite General Assembly Process Planning

Beginning with the disassembly of the semi-finished modules, the general assembly process of satellites is quite different from that of other mechanical products. This kind of disassembly-reassembly process cannot be solved by the widely used cut-set theory that only deals with linear problems, thus an approach called Dynamic Transition Graph (DTG) is proposed to solve this nonlinear assembly sequence planning problem. By analyzing and verifying possible assembly statuses hierarchically through matrix operations, a DTG is produced on the basis of Liaison Graph, where the DTG includes all the geometric feasible assembly sequences for the general assembly of satellite. Finally, the effectiveness of this method is verified by an example.

BOOK REVIEW: Ratsimbaharison, Adrien. THE FAILURE OF THE UNITED NATIONS DEVELOPMENT PROGRAMS FOR AFRICA. Lanham, MD: University Press of America, 2003.

Reviewed by: The Failure of the United Nations Development Programs for Africa Loveness Schafer and Mark Schafer Ratsimbaharison, Adrien . 2003. The Failure of the United Nations Development Programs for Africa. Lanham, MD: University Press of America. 196 pp. $29.00 (paper) My favorite aspect of this book was the author's discussion of the United Nations General Assembly processes that led to the United Nations Program of Action for the African Economic Recovery and Development (UNPAAERD) and the United Nations New Agenda for the Development of Africa (UNNADAF). Ratsimbaharison alleges that the United Nations erred in allowing its programs to be formulated chiefly by African nations without adequate input from the wider body of nations, and then adopted without a formal vote. No wonder donor nations did not fund or support these initiatives! No wonder they failed miserably! The United Nations failed to rally the international community, failed to coordinate disparate development efforts, failed to charge a single specific entity with the responsibility of administering its programs, and failed to learn adequately from the failure of its first program in developing its successor. Hopefully, students of international relations can learn from this scathing account of U.N. General Assembly failures, even if the assembly itself could not. The critical kernel can be summed up succinctly: process matters. How the United Nations goes about formulating its programs exerts a strong influence on its capacity to achieve its programmatic goals. In adopting programs rooted in dependency-informed perspectives expressed through the Organization of African Unity (OAU) and Africa's Priority Program for Economic Recovery (APPER), these programs were little more than another outlet for the regional bodies to express their development priorities. Clearly, development programs have to be acceptable to both donors and recipients, as the author recommends. Unfortunately, Ratsimbaharison fails to offer concrete suggestions for improving U.N. General Assembly processes. Instead, he suggests the United Nations follow the path of the International Monetary Fund, recommending (1) eschewing regional programs and dealing only with specific nations and (2) embedding programs within the context of the global economy. I find these recommendations baffling because, whatever their advantages or disadvantages, IMF negotiations with its member states can hardly be described as model processes of transparency and accountability. Case studies of Madagascar and Mauritius are included to demonstrate the uselessness of regional programs, because they reflect uniqueness prevalent among the region's nation-states. Ratsimbaharison characterizes both the Malagasy national development strategy and the UNPAAERD and UNNADAF programs there as "inward-looking," at odds with the prevailing economic trends embodied in structural-adjustment programs. Mauritius, in contrast, was "outward-looking," one of the more-successful African nations, and one that actively pursued a strategy of export-oriented industrialization. Old fashioned U.N. programs would have been useless, maybe even harmful, if they had been implemented in this Indian Ocean economy. [End Page 88] The moral, of course, is that the Bretton Woods institutions, the IMF and the World Bank, offered the only viable path to development, the path winding through austerity, SAPs, export-processing zones, liberalization, and so on. Consistent with IMF operating procedures and practices, the specific adjustment policies should be decided on a case-by-case basis (regional prescriptions are too constraining), and should ensure that each nation optimize its economic niche within the global economy. I had hoped for a different conclusion. Of course the U.N. General Assembly should not be a mouthpiece for the OAU, adopting programs without even putting it up for a vote. But neither should the United Nations be constrained to development projects and orientations consistent with the "prevailing economic order," or the global financial institutions to support it. The United Nations must attempt to be an institution within which a continuous dialog can take place, a dialog in which individual nations, regional bodies, global financial institutions, and international NGOs can all have a voice. U.N.-supported regional development programming need not overly constrain national programs, and they have the potential to foster cooperation in furthering trade and communications among Africa's nation-states, as regional trade associations (North American Free Trade Agreement, the European Union) have done elsewhere. Ratsimbaharison's recommendations that U.N...

손목 자세와 외부 부하에 따른 손목 불편도 모델링

The objectives of this study are to analyze representative wrist postures while using hand tools and parts at general assembly processes, to evaluate perceived discomfort on the wrist when external loads are present, and to suggest an evaluation and prediction model of perceived discomfort. Sixteen subjects participated in an experiment to appraise perceived discomfort. Three types of the wrist postures with five levels of non-neutralities were analyzed when five levels of external load were applied to each posture. The ANOVA results showed that the perceived discomfort of wrist postures was significantly affected by both the wrist posture and external load (p<0.001). It was also shown that some of the interactions between external loads and the wrist postures(Flexion/Extension*Load, Flexion/Extension*supination/pronation, ulnar/radial deviation*supination/pronation) were significant(p<0.001). The result implies that a new posture classification scheme for workload assessment methods may be needed to reflect such effects of external load and wrist posture. A regression model of perceived discomfort was developed with respect to wrist posture and external load from the experimental data. A subsequent experiment revealed that the correlation coefficient between the predicted values of perceived discomfort from the model and the actual values obtained from the experiment was about 0.98. It is expected that the results help to properly estimate the body stress resulting from worker's postures and external loads and can be used as a valuable design guideline to analyze potential hazard of musculoskeletal diseases in industry.

Amyloid formation: an emulation of matrix protein assembly?

Although more than 20 different proteins are now associated with the amyloidoses, the fibrils share many properties. Despite disparity in primary and tertiary structures of the subunit proteins, assembled fibrils exhibit similar morphology, binding of Congo red, interaction with Thioflavine T, formation of complexes with serum amyloid P component, apolipoprotein E, several glycosaminoglycans, the receptor for advanced glycation endproducts and cross-recognition by some monoclonal antibodies. Thus, it is probable that the mechanism of amyloid generation involves a generic process that can be evoked by most, if not all, proteins under conditions that degrade the native conformation. As suggested by others, the beta-helix or beta-roll conformation may be the unifying element of fibril conformations. Several proteins that have evolved to form physiologically useful amyloid-like fibrils, as well as some proteins associated with pathological amyloidoses, exhibit sequence repeat patterns that may facilitate beta-roll or beta-helix formation. Threading analyses of 2 natural amyloid-forming proteins, curli and human Pmel 17, indicate compatibility of their primary structures with both beta sandwich and beta-helix conformations, suggesting a possible innate conformational pliability. In addition, these results may suggest that the misfolded form of some proteins that are associated with conformational disease may be the native conformation of other proteins to which they are linked by evolution. Finally, since many matrix and structural proteins are known to incorporate numerous tandem repeat sequence elements, we propose that the mechanism of fibril formation is fundamentally related to a general protein assembly process that is integral to the generation of cells and tissues.

Integration of CAPP and PPC — The PPC Part

The paper introduces concepts for the integration of Computer Automated Process Planning (CAPP) and Production Planning & Control (PPC). Logics, benefits and scenarios of functional integration are discussed. Methods and techniques for the Implementation of an integration are highlighted. Based on a general assembly Process model, various planning aspects of PPC such as lot-sizing, scheduling and bottleneck management are finally shown.