A Real-Time Haptics-Based Deformable Model for Virtual Prototyping and Simulations

Virtual reality technology plays an important role in the fields of product design, computer animation, medical simulation, cloth motion, and many others. Especially with the emergence of haptics technology, virtual simulation system provides an intuitive way of human and computer interaction, which allows user to feel and touch the virtual environment. For a real-time simulation system, a physically based deformable model including complex material properties with a high resolution is required. However, such deformable model hardly satisfies the update rate of interactive haptic rendering that exceeds 1 kHz. To tackle this challenge, a real-time volumetric model with haptic feedback is developed in this paper. This model, named as Adaptive S-chain model, extends the S-chain model and integrates the energy-based wave propagation method by the proposed adaptive re-mesh method to achieve realistic graphic and haptic deformation results. The implemented results show that the nonlinear, heterogeneous, anisotropic, shape retaining material properties and large range deformation are well modeled. An accurate force feedback is generated by the proposed Adaptive S-chain model in case study which is quite close to the experiment data.

Analytical Calculation of Cutter/Workpiece Engagements for Helical Hole Milling

Helical milling is a 3-axis machining operation where a cutting tool is feed along a helix. This operation is used in ramp-in and ramp-out moves when the cutting tool first engages the workpiece, for contouring and for hole machining. It is increasingly finding application as a means for roughing large amounts of material during high speed machining. Simulating the helical milling process requires Cutter/Workpiece Engagement (CWE) geometry in order to predict cutting forces. The calculation of these engagements is challenging due to the complicated and changing intersection geometry that occurs between the cutter and the in-process workpiece. For hole milling an additional complication comes from self-intersections that occur with the tool swept volume. This makes the generation of the instantaneous in-process workpiece needed for finding the CWE difficult. In this paper we present an analytical approach for finding the engagement geometry that utilizes the intersection curves between a cylinder representing a flat end mill and the helicoidal surface generated by the bottom of the tool as it feeds downwards along the helix. This technique can be integrated into a solid modeler based approach for machining simulation. It has the advantage of not require instantaneous updates of the workpiece as is typically the case in finding CWEs.

An Ontology Mapping Application Using a Shared Ontology Approach and a Bridge Ontology

This paper presents our continuing work to develop methods to exchange product knowledge in the semantic level in the CAD/CAE domains. We present an approach based on a shared ontology, in which a higher level of ontologies are shared among lower levels of ontologies. Key mapping strategies, such as Equivalency, Attribute Similarity, Composition Similarity, and Inheritance Similarity are defined to map concepts and properties defined in a product design domain and an assembly simulation domain. In addition, a Bridge Ontology is designed to store information obtained from mapping processes and construct a link between different knowledge repositories. An Ontology Mapping Application (OMA) which brings together all these elements has been designed and implemented. It is a Java-based application that allows the user to load source and target ontologies, calculate concept and property similarities between them, display the mapping results, and output a corresponding Bridge Ontology.

Development and Implementation of Shape Comparison of 3D CAD Models

With the advancements of 3D modeling software, the use of CAD in design has become a standard practice. In recent years development in computer hardware and improvements in user friendliness of the CAD software has allowed designers to quickly and easily modify the CAD models. This modification capability allows CAD to be an integral part of the design process. Due to the increase in global competition, companies have become increasingly interested in fast and efficient design processes. One way to achieve improved efficiency is through better collaboration among designers working in common or similar projects and disciplines. A large design problem often requires specialized knowledge from several fields. Collaboration among the designers from these fields will ensure efficient design. Interaction among the designers can prevent redesign of similar components/subsystems, which requires the ability to share their designs. With the increase of collaboration, designers can now get access to large databases of 3D CAD models. But the challenge lies in search capabilities to identify common models from a large database. These considerations suggest that in the near future a challenge in 3D CAD industry will be how to find models of similar components and products. This paper presents an approach and its implementation to measure the similarity among a number of CAD models. The approach is based on the extraction and organization of information from the CAD models, which is followed by the suitable selection of commonality index and calculation of the commonality among a set of CAD models. A set of Vacuum cleaners are modeled and then compared to demonstrate the application of the approach.

A Computational Product Model for Conceptual Design Using SysML

The importance of the concept development phase in product development is contradictory to the level and amount of current computer-based support for it, especially with regards to mechanical design. Paper-based methods for conceptual design offer a far greater level of maturity and familiarity than current computational methods. Engineers usually work with software designed to address only a single stage of the concept design phase, such as requirements management tools. Integration with software covering other stages, e.g. functional modeling, is generally poor. Using the requirements for concept models outlined in the VDI 2221 guideline for systematic product development as a starting point, the authors propose an integrated product model constructed using the Systems Modeling Language (SysML) that moves beyond geometry to integrate all necessary aspects for conceptual design. These include requirements, functions and function structures, working principles and their structures as well as physical effects. In order to explore the applicability of SysML for mechanical design, a case study on the design of a passenger car’s luggage compartment cover is presented. The case study shows that many different SysML diagram types are suitable for formal modeling in mechanical concept design, though they were originally defined for software and control system development. It is then proposed that the creation and use of libraries defining generic as well as more complicated templates raises efficiency in modeling. The use of diagrams and their semantics for conceptual modeling make SysML a strong candidate for integrated product modeling of mechanical as well as mechatronic systems.

Computer Modeling of Impressed Current Cathodic Protection (ICCP) System Anodes

Computer modeling is now widely used to predict how effective cathodic protection (CP) systems are at protecting structures and maritime vessels. There are two types of CP systems based on either sacrificial anodes or impressed anodes (ICCP) or some combination of the two types. Impressed anodes are often referred to as “active” systems as they can respond to changes in the protection requirements as they are connected to some form of control system. Typically in computer models ICCP anodes are controlled by specifying the current they output in response to the potential measured at a reference electrode. In this paper an alternative approach has been investigated where the model also includes the power supply as well as the associated cables etc connecting to the anodes. This enables us to more accurately model situations where any number of anodes are connected to a single power supply, anode/reference electrode (RE) failure scenarios, non symmetric anode layouts, localized damage to coatings and situations where there are significant appendages to the vessel which change the current requirements. The paper will describe the technical approach to the modeling and present examples of modeling of a commercial FPSO vessel. (Floating, Production, Storage and Offloading vessels are used in the Oil & Gas industry typically as part of deepwater developments) The benefits of the proposed approach compared with the conventional approach will be presented and the results critically analyzed.

Product Analysis and Variants Derivation Based on a Semantically Annotated Product Family Ontology

In literature, there are a number of indexes suggested that serve as the indicator of commonality among product components, modules and variants. However, as these elements are increasingly interconnected with aspects other than the component view, the existing commonality metrics are unable to effectively model these aspects due to their limitation in capturing relevant information for analysis. Therefore, there exists a need to consider multiple design and manufacturing aspects in commonality metrics so that a comprehensive view of the commonality among product variants can be presented. In the current representation schemes proposed for product family modeling, ontology is one of the most promising ones to model the complex semantic relations among various elements in a product family. Nevertheless, the research and application of ontology in the analysis of a product family has so far received little attention. In this paper, we proposed a framework to generate a semantically annotated multi-facet product family ontology. Using a case study of a laptop computer family, we suggest and demonstrate a new commonality analysis approach based on the semantically annotated multi-facet laptop product family ontology. Together with a new method of deriving product variants based on the aforementioned ontology, our approach illustrates the merits of using semantic annotation in assisting ontology based product family analysis.

Challenges for Experience Feedback in Engineering Design

In this paper empirical finding from a study conducted at an aerospace company is compared to theory regarding Experience Feedback (EF), Lessons Learned (LL) and Decision Making (DM). The purpose with the study was to examine how EF within the organization was conducted and what problems and possibilities that was seen. A qualitative approach was taken and interviews and a workshop was conducted. The empirical findings show that EF exist on different levels within the organization but current feedback processes are currently leaning more towards archiving and storing than knowledge sharing and learning. Also passive dissemination approaches are mostly used whereas active dissemination within the correct context is needed The aim with this paper is to discuss issues and empirical findings that should be considered when creating work methods and systems that support learning by EF and LL dissemination.

On Measures of Coupling Between the Artifact and Controller Optimal Design Problems

Optimization of smart products requires optimizing both the artifact design and its controller. The presence of coupling between the design and control problems is an important consideration in choosing the system optimization method. Several measures of coupling have been proposed based on different viewpoints of the system. In this paper, two measures of coupling, a vector based on optimality conditions and a matrix derived from an extension of the global sensitivity equations, are shown to be related under certain conditions and to be consistent in their coupling determination. The measures’ physical interpretation and relative ease of use are discussed using the example of a positioning gantry. A further relation is derived between one measure and a modified sequential formulation that would give results sufficiently close to the true solutions.

Optimizing Locator Position to Maximize Robustness in Critical Product Dimensions

The way parts are located in relation to each other or in fixtures is critical for how geometrical variation will propagate and cause variation in critical product dimensions. Therefore, more emphasis should be put on this activity in early design phases in order to avoid assembly and production problems later on. In earlier literature, locator positions have been defined using optimization to reach a robust locating scheme. This implies that the total robustness of a part is optimized by placing the locators in an optimal way. Sometimes there are areas on parts that are more sensitive to variation than others. Therefore, this paper suggests an approach for optimizing the positions of locators in a locating scheme to maximize robustness in defined critical dimensions. A formulation of an optimization problem is presented, and an algorithm solving this in a heuristic approach is developed. Finally, this algorithm is applied on an industrial example.