Bartholomew O. Nnaji

Optimization of indoor wireless communication network layouts

Radio Frequency Data Communications (RFDC)technology is rapidly becoming a critical component of many traditional industrial engineering functions including materials tracking, inventory control, warehousing, order processing, shipping and database management. As a means of moving information, RFDC has many attractive features, such as speed, accuracy, reliability, convenience and low operating costs. When implementing RFDC systems a major problem is to quickly and efficiently determine the locations where transceivers should be placed so that effective radio communication can take place. The research described in this paper addresses this issue by developing a computerized layout simulation system that incorporates heuristic optimization methods to solve the placement problem. The effectiveness of this unique automated layout methodology is demonstrated by comparing it with the current method of utilizing manual site surveys, as well as with other placement methods. The methodology and solutions are validated by field-testing at actual facilities.

Design formalism for collaborative assembly design

Abstract Joints in product design are common because of the limitations of component geometric configurations and material properties, and the requirements of inspection, accessibility, repair, and portability. Collaborative product design is emerging as a viable alternative to the traditional design process. The collaborative assembly design (AsD) methodologies are needed for distributed product development. Existing AsD methodologies have limitations in capturing the non-geometric aspects of designers intent on joining and are not efficient for a collaborative design environment. This paper introduces an AsD formalism and associated AsD tools to capture joining relations and spatial relationship implications. This AsD formalism allows the joining relations to be modeled symbolically for computer interpretation, and the model can be used for inferring mathematical and physical implications. An AsD model generated from the AsD formalism is used to exchange AsD information transparently in a collaborative AsD environment. An assembly relation model and a generic assembly relationship diagram are to capture assembly and joining information concisely and persistently. As a demonstration, the developed AsD formalism and AsD tools are applied on a connector assembly with arc weld and rivet joints.

3D model acquisition, design, planning, and manufacturing of orthopaedic devices: a framework

Design and manufacture of orthopedic devices using rapid prototyping technologies has been until recently a highly iterative process that involves multiple users, including doctors, design engineers and rapid prototyping experts. Existing systems for creation of orthopedic parts through rapid prototyping do not follow the principles of concurrent engineering and design for manufacture. This leads to excessive communication between parties and delays in product realization time. In this paper, we lay out the framework for a unified expert system that will enable a doctor to create quickly and easily fully functional prosthetics and orthopedic implants. Necessary components of the model acquisition process should include volumetric segmentation of objects from a CT or MRI dataset and NURBS surface fitting to the boundary points. Finite element analysis and surface model modification modules are also needed, but should be provided in an intuitive fashion for doctors who are not experienced in computer aided design. Preprocessing for rapid prototype building should be automatic, and should include optimal orientation, support structure generation and build simulation modules. Finally, the model should be passed to the rapid prototyping machine in a presliced format for speed and accuracy.

Intellectual Property Protection in Collaborative Design through Lean Information Modeling and Sharing

ing intellectual property is vital to maintain organizational competence in today’s global business environment. In this paper, a lean information modeling and sharing framework is described to support engineering data security management in a peer-to-peer collaborative environment. It allows for selective and interoperable data sharing with finegrained access control at both the server and client sides, thus securing different levels of design information dissemination for intellectual property protection purposes. The considerations of time and value-adding activity with roles, policy delegation relation in a distributed context, and fine-grained control at data set level in the model are to adhere to the general least privilege principle in access control. Heterogeneous design data are exchanged selectively through an eXtensible Markup Language common interface, which provides a neutral format to enhance data interoperability and prevents reverse engineering. DOI: 10.1115/1.2190235

Geometry-based semantic ID for persistent and interoperable reference in feature-based parametric modeling

In current feature-based parametric design systems, the reusability principle is not fully supported as it was expected. Unpredictability and ambiguity of models often happen during design modification within one system as well as among different systems. This reference deficiency significantly reduces the power of feature-based parametric modeling, where geometry re-evaluation generates unexpected shapes. In this paper, a sufficient condition of B-Rep variance based on geometry continuity in parametric complex Euclidean (P^pC^3) space is proposed. Shape and relation parameters are differentiated in P^pC^3, thus parametric family can be defined. A semantic id scheme based on continuity of geometry is developed to solve the problem of naming persistency and to improve interoperability of CAD feature modeling. Hierarchical namespaces localize entity creation and identification. All geometric and topological entities are referred uniformly based on surface ids, and topology semantics is retained in id itself.

UL-PML: constraint-enabled distributed product data model

The global economy has made manufacturing industry more distributed than ever before. Product design requires more involvement from various technical disciplines at different locations. In such a geographically and temporally distributed environment, efficient and effective collaboration on design is vital to maintain product quality and organizational competency. Current standard computer-aided design data formats do not support design collaboration effectively in terms of design information and knowledge capturing, exchange, and integration. Design constraints cannot be represented and transferred among different groups, and design information cannot be integrated efficiently within a distributed environment. A new design data model, the Universal Linkage model, is developed here to represent design-related information for network-based collaborative design. It incorporates geometric and non-geometric constraints with traditional geometric elements, thus allowing more design knowledge sharing in collaborative design. Segments of design information can be linked and integrated into a set of complete product data. Thus, lean information exchange can be realized. This model, which has good properties of openness and extensibility, is represented by Directed Hyper Graph and Product Markup Language.

Solving Interval Constraints by Linearization in Computer-Aided Design

Current parametric CAD systems require geometric parameters to have fixed values. Specifying fixed parameter values implicitly adds rigid constraints on the geometry, which have the potential to introduce conflicts during the design process. This paper presents a soft constraint representation scheme based on nominal interval. Interval geometric parameters capture inexactness of conceptual and embodiment design, uncertainty in detail design, as well as boundary information for design optimization. To accommodate under-constrained and over-constrained design problems, a double-loop Gauss-Seidel method is developed to solve linear constraints. A symbolic preconditioning procedure transforms nonlinear equations to separable form. Inequalities are also transformed and integrated with equalities. Nonlinear constraints can be bounded by piecewise linear enclosures and solved by linear methods iteratively. A sensitivity analysis method that differentiates active and inactive constraints is presented for design refinement.

Heuristics for single-pass welding task sequencing

Welding task sequencing is a prerequisite in the offline programming of robot arc welding. Single-pass welding task sequencing can be modelled as a modified travelling salesman problem. Owing to the difficulty of the resulting arc-routing problems, effective local search heuristics are developed. Computational speed becomes important because robot arc welding is often part of an automated process-planning procedure. Generating a reasonable solution in an acceptable time is necessary for effective automated process planning. Several different heuristics are proposed for solving the welding task-sequencing problem considering both productivity and the potential for welding distortion. Constructive heuristics based on the nearest neighbour concept and tabu search heuristics are developed and enhanced using improvement procedures. The effectiveness of the heuristics developed is tested and verified on actual welded structure problems and random problems.

Ontology-based virtual assembly model for collaborative virtual prototyping and simulation

Todays virtual prototyping systems for assembly provide a single instance of simulation and analysis solutions from models that are often generated from scratch. Virtual assembly models (VAM) are not fully integrated with other design activities, such as conceptual and detailed design, and design intent is not fully propagated to all product development activities. An assembly design (AsD) ontology can capture assembly and joining intents and can be efficiently reused in collaborative assembly development activities. Through the use of ontologies, computer systems can reason with data and information rather than just explicitly capture it. This paper presents an AsD ontology that plays as a formal, explicit specification of a shared conceptualization of assembly design and serves as a basis for a VAM for collaborative virtual prototyping and simulation (VP&S). The ontology-based VAM makes clear the relations among assembly components and form features in an AsD and provides systematized knowledge, which can be reasoned by collaboration tools. The VAM also captures design rationale including joining intent and spatial relationships. This paper discusses the role of VAM in collaborative VP&S and presents an AsD browser for virtual assembly analysis

A multimedia support system for collaborative assembly design

In collaboration, multimedia information/data act as very important tools to share product design and engineering knowledge between project participants. However, current multimedia in collaboration provide only communication protocols and have limitations on capturing any engineering information imposed on product design. Hence, this paper aims to introduce a new framework of multimedia support for assembly design (AsD). The multimedia are linked to remote and distributed engineering information/data, which are core sources of AsD decision making. In doing so, rather than directly interfacing and sharing engineering information/data, the new framework will provide design participants with a seamless way of collaboration. Attributed relational graphs (ARGs) are adopted to employ an efficient representation of image contents. An extended ARG is proposed to incorporate information about assembly relationships and mathematical decision-making models with ARG-formatted graphical information. This research employs a service-oriented architecture (SOA) remotely and transparently to exchange multimedia, assembly relationships and mathematical model information for multimedia support. MSS-AD (multimedia support system for collaborative AsD), a prototype system, has been implemented to show the feasibility of the idea proposed in this paper.