Wissensbasierte Entwurfsbewertung der Produktgestalt mittels Multi-Agentensystemen

Beim Gestalten legen die Konstruierenden eine Vielzahl der Produkteigenschaften fest, welche Einfluss auf den gesamten Produktlebenszyklus haben. Daher verlangt ein moderner Produktentwicklungsprozess, dass ein Produkt nicht nur aufgrund seiner Funktionserfüllung optimiert wird, sondern auch vor dem Hintergrund des Design for X (DfX), welches die Berücksichtigung von Anforderungen aus dem gesamten Produktlebenszyklus beinhaltet. Die zunehmende Komplexität in der Produktentwicklung und der fehlende Wissensaustausch, beispielsweise zwischen der Entwicklung und Fertigung, führen zu unnötigen Iterationsschleifen und hohen Kosten. Im Rahmen dieser Arbeit wird eine wissensbasierte Entwurfsbewertung der Produktgestalt mittels Multi-Agentensystemen vorgestellt, um den Konstruierenden ein digitales Assistenzsystem zur Überprüfung von CAD-Modellen hinsichtlich der DfX-Anforderungen zur Verfügung zu stellen. Hierzu werden, zum einen für die Repräsentation des domänenspezifischen Wissens wissensbasierte Entwicklungs- und Konstruktionssysteme untersucht und zum anderen für die Durchführung von dezentralen Schlussfolgerungsmechanismen und Verhandlungen das Multi-Agentensystem vorgestellt. Das methodische Vorgehen MaSE4D zur Entwicklung von Multi-Agentensystemen ermöglicht, ausgehend vom initialen Systemkontext, eine strukturierte Zusammensetzung der dezentral verteilten Wissensquellen, um eine ganzheitliche Bewertung in der Domäne der Produktgestaltung vorzunehmen. Durch einen generalisierten Aufbau einer Software-Architektur ist es zudem möglich ein 3D-Modell in einer CAD-Entwicklungsumgebung, mittels graphenbasierter Featureerkennung, zu analysieren und automatisiert anzupassen. Des Weiteren werden Templates für die Programmierung von Agenten zur Verfügung gestellt, welche die dezentrale Wissensverwaltung, die Kommunikation unter den Agenten sowie deren Verwaltung im Kontext der Produktgestaltung unterstützen. Die Anwendbarkeit und Validierung des methodischen Vorgehens und der Entwicklungsumgebung für das Multi-Agentensystem erfolgt durch die Bewertung von zehn unterschiedlichen Frästeilentwürfen.During the design process, the designers determine numerous product properties that have an influence on the entire product life cycle. Therefore, a modern product development process requires that a product is not only optimized based on its functional fulfillment but also regarding Design for X, which includes the consideration of requirements from the entire product life cycle. The increasing complexity in product development and the lack of knowledge exchange between development and manufacturing lead to iteration loops and higher costs. In the context of this work, a knowledge-based evaluation of embodiment design using multi-agent systems is presented to provide designers with a digital assistance system for the verification of CAD models regarding Design for X. For this purpose, knowledge-based engineering systems are investigated for the representation of domain-specific knowledge on the one hand. On the other hand, multi-agent systems are introduced for the execution of decentralized reasoning mechanisms and negotiations. The methodological approach MaSE4D for the development of multi-agent systems allows, starting from the initial system context, a structured composition of the decentralized distributed knowledge sources to perform a holistic evaluation in the domain of product design. A generalized software architecture allows analyzing and automatically adapting a 3D model in a CAD development environment using graph-based feature recognition. Furthermore, templates for programming agents are provided, which support decentralized knowledge management, communication among agents, as well as their management in the context of product design. The applicability and validation of the multi-agent system's methodological approach and development environment is performed by evaluating ten different milling designs

Making design decisions under uncertainties: probabilistic reasoning and robust product design

Making design decisions is characterized by a high degree of uncertainty, especially in the early phase of the product development process, when little information is known, while the decisions made have an impact on the entire product life cycle. Therefore, the goal of complexity management is to reduce uncertainty in order to minimize or avoid the need for design changes in a late phase of product development or in the use phase. With our approach we model the uncertainties with probabilistic reasoning in a Bayesian decision network explicitly, as the uncertainties are directly attached to parts of the design artifact′s model. By modeling the incomplete information expressed by unobserved variables in the Bayesian network in terms of probabilities, as well as the variation of product properties or parameters, a conclusion about the robustness of the product can be made. The application example of a rotary valve from engineering design shows that the decision network can support the engineer in decision-making under uncertainty. Furthermore, a contribution to knowledge formalization in the development project is made

Process Chain-Oriented Design Evaluation of Multi-Material Components by Knowledge-Based Engineering

The design of components suitable for manufacturing requires the application of knowledge about the manufacturing process chain with which the component is to be manufactured. This article presents an assistance system for decision support in the context of design for manufacturing. The assistance system includes explicit manufacturing process chain knowledge and has an inference engine that can automatically evaluate the manufacturability of a component design based on a given manufacturing process chain and resolve emerging manufacturing conflicts by making adjustments on the component or resource side. A link with a CAD system additionally enables the three-dimensional representation of derived manufacturing stages and manufacturing resources. Within the assistance system, a manufacturing process chain is understood as a configurable design object and is implemented via a constraint satisfaction problem. Furthermore, the required abstraction of manufacturing processes within finite domains can be reduced to the extent that necessary modeling resolution is achieved by incorporating empirical or simulative surrogate models into the CSP. The assistance system was conceptually validated on a tailored forming process chain for the production of a multimaterial shaft and provides added value, as valuable manufacturing information for component designs is automatically derived and made available in explicit form during the component development

Application of Decentralized and Self-Regulating Knowledge Bases for Assembly Design Automation

During product development, changes to parts that are already built into assemblies usually lead to the need to check the function and consistency of the assembly. This procedure is very time-consuming and has to be performed again for each change. In this paper, an approach is presented in which the individual parts are represented as agents that adapt themselves to new conditions. The agents are combined in a multi-agent system (MAS) and interact via communication over messages. For this purpose, a methodical procedure for the development of the MAS and the implementation in a CAD development environment is presented. The validation of the MAS is carried out on the application example of a gearbox

Application of the Computational Design Synthesis framework for individualized car seats

The manufacturing capabilities of additive manufacturing allow great design freedom for mass customization of different products. This new solution space needs to be explored and served by engineers when designing individual variants of a product. Therefore, the methods of model generation for the individual variant with individual customer specific requirements must be improved to take advantage of this design freedom. This paper discusses the specific challenges of designing a customized car seat by showing its general process chain and the challenges associated with the design of foam replacement structures that offer the possibility to customize the stiffness of the cushion. A possible framework for the underlying digital process chain is then discussed. This framework manages model synthesis according to anthropometric data and safety requirements as conflicting requirements within various complex engineering correlations. In a case study, the chosen Computational Design Synthesis (CDS) framework is applied to the problem of designing an individualized car seat. Detailed descriptions of the concept for each block in the process chain are presented within the case study. The paper and conclusion discuss whether the framework meets the challenges of the application example and further steps for the project

Thermo-Elastic Topology Optimization For High Temperatures Gradients Using Load Separation

Designing components for thermo-mechanical loads is a challenging process. While mechanical loads like forces or pressure demand a stiff and thick-walled design, thermal loads create temperature gradients, resulting in thermo-mechanical stress from the structure's temperature proportional and, therefore, uneven expansion. In contrast to a pure mechanical load case, an initial design before optimization can already include stress levels beyond the limit of the material. Therefore, common optimization approaches for a preliminary design use exemplary systems with low-temperature gradients, so thermal stresses do not exceed the limit. From there, energy density is used to calculate the topology optimizations sensitivity and therefore decide which elements to remove and which to keep. This paper describes a novel approach for reducing thermo-mechanical stress by following the stress corresponding temperature gradients from the heat source to the sink to calculate a new sensitivity that helps to grow cooling channels. The optimization is exemplarily shown on a piston for internal combustion engines. While handling delta temperatures of 600K, results show a reduction in thermo-mechanical stress while reducing the component's mass. Because the approach reduces critical stress in a component, it allows the initial design (before the topology optimization) to have stress levels way above yield strength

Development of a knowledge-based and collaborative engineering design agent

In order to avoid errors in engineering design that affect the later product life cycle, especially the manufacturing process, an analysis or evaluation has to be performed at the earliest possible stage. As this evaluation is very knowledge-intensive and often this knowledge is not directly available to the engineer, this paper presents an approach for a knowledge-based and collaborative engineering design agent. The technology based on multi-agent systems enables problem-solving support by an autonomous knowledge-based system which has its own beliefs, goals, and intentions. The presented approach is embedded in a CAD development environment and validated on an application example from engineering design

Structuring and Provision of Manufacturing knowledge through the Manufacturing Resource Ontology

One challenge in manufacturing-integrated product development is the accessibility of the required manufacturing knowledge. Here, ontologies offer the possibility to structure and formalize information in the form of a knowledge base in order to act as a generic interface to the manufacturing and design specific systems. This paper describes the development of a generic knowledge base called MARON (MAnufacturing Restriction ONtology) for the structured representation of manufacturing restrictions via formalized manufacturing capabilities. Using the example of an expert system for process element-oriented manufacturability analysis, it is shown how MARON contributes to automated decision support in the context of manufacturing-oriented design

Transparent, flexible, and strong 2,3-dialdehyde cellulose films with high oxygen barrier properties

2,3-Dialdehyde cellulose (DAC) of a high degree of oxidation (92% relative to AGU units) prepared by oxidation of microcrystalline cellulose with sodium periodate (48 degrees C, 19 h) is soluble in hot water. Solution casting, slow air drying, hot pressing, and reinforcement by cellulose nanocrystals afforded films (similar to 100 mu m thickness) that feature intriguing properties: they have very smooth surfaces (SEM), are highly flexible, and have good light transmittance for both the visible and near-infrared range (89-91%), high tensile strength (81-122 MPa), and modulus of elasticity (3.4-4.0 GPa) depending on hydration state and respective water content. The extraordinarily low oxygen permeation ofPeer reviewe

Process chain-oriented manufacturability assessment of products by using a constraint satisfaction problem

Dieser Beitrag stellt eine rechnergestützte Modellierungsstrategie vor, um Prozesskettenwissen, wie die Gestaltung der Fertigungsstufen, prozessübergreifende Fertigungsrestriktionen oder Fertigungshilfsmittel, für die Produktgestaltung zu formalisieren und im Kontext des Design for Manufacturing für Produkt- und Prozessgestaltungsentscheidungen bereitzustellen. Dabei werden am Beispiel einer Tailored-Forming-Prozesskette die Herstellungsschritte einer Multimaterial-Welle mittels eines Constraint-Satisfaction-Problems (CSP) modelliert, indem die geometrischen Transformationen einzelner Fertigungsstufen sowie Fertigungsrestriktionen in Form von Constraints und Fertigungsstufen sowie Fertigungshilfsmittel über Parameter in den CSP-Variablen formuliert werden. Das CSP ist damit in der Lage, ausgehend von einem Geometriemodell eines Bauteils eine prozesskettenorientierte Restriktionsprüfung zur Herstellbarkeitsbewertung durchzuführen und automatisiert Fertigungsstufen sowie Fertigungshilfsmittel zu konfigurieren.This paper presents a computer-aided modeling strategy to formalize process chain knowledge, such as the design of manufacturing stages, cross-process manufacturing constraints or manufacturing tools, for product design and to provide it for product and process design decisions in the context of design for manufacturing. Using the example of a tailored forming process chain, the manufacturing steps of a multi-material shaft are modeled by means of a constraint satisfaction problem (CSP) by formulating the geometric transformations of individual manufacturing steps as well as manufacturing restrictions in the form of constraints, and manufacturing steps as well as manufacturing resources via parameters in the CSP variables. The CSP is thus able to perform a process-chain-oriented restriction check for manufacturability evaluation based on a geometry model of a component and to automatically configure manufacturing stages and manufacturing resources and tools