Virtual reality for assembly methods prototyping: a review

Assembly planning and evaluation is an important component of the product design process in which details about how parts of a new product will be put together are formalized. A well designed assembly process should take into account various factors such as optimum assembly time and sequence, tooling and fixture requirements, ergonomics, operator safety, and accessibility, among others. Existing computer-based tools to support virtual assembly either concentrate solely on representation of the geometry of parts and fixtures and evaluation of clearances and tolerances or use simulated human mannequins to approximate human interaction in the assembly process. Virtual reality technology has the potential to support integration of natural human motions into the computer aided assembly planning environment (Ritchie et al. in Proc I MECH E Part B J Eng 213(5):461–474, 1999). This would allow evaluations of an assembler’s ability to manipulate and assemble parts and result in reduced time and cost for product design. This paper provides a review of the research in virtual assembly and categorizes the different approaches. Finally, critical requirements and directions for future research are presented

Solving incidence and tangency constraints in 2D

This paper reports on solving geometric constraint satisfaction problems involving incidence and tangency constraints in 2D. A variational geometric constraint solver based on a constructive approach is used: the main goal is to keep the present set of rules as small as possible. Defining tangency conditions as distance and angle constraints allows solving fixed radius configurations. Non-fixed radius schemes are also characterized and a new set of constructive rules is proposed.Postprint (published version

A framework for parametric design optimization using isogeometric analysis

Isogeometric analysis (IGA) fundamentally seeks to bridge the gap between engineering design and high-fidelity computational analysis by using spline functions as finite element bases. However, additional computational design paradigms must be taken into consideration to ensure that designers can take full advantage of IGA, especially within the context of design optimization. In this work, we propose a novel approach that employs IGA methodologies while still rigorously abiding by the paradigms of advanced design parameterization, analysis model validity, and interactivity. The entire design lifecycle utilizes a consistent geometry description and is contained within a single platform. Because of this unified workflow, iterative design optimization can be naturally integrated. The proposed methodology is demonstrated through an IGA-based parametric design optimization framework implemented using the Grasshopper algorithmic modeling interface for Rhinoceros 3D. The framework is capable of performing IGA-based design optimization of realistic engineering structures that are practically constructed through the use of complex geometric operations. We demonstrate the framework’s effectiveness on both an internally pressurized tube and a wind turbine blade, highlighting its applicability across a spectrum of design complexity. In addition to inherently featuring the advantageous characteristics of IGA, the seamless nature of the workflow instantiated in this framework diminishes the obstacles traditionally encountered when performing finite-element-analysis-based design optimization

Combining physical constraints with geometric constraint-based modeling for virtual assembly

The research presented in this dissertation aims to create a virtual assembly environment capable of simulating the constant and subtle interactions (hand-part, part-part) that occur during manual assembly, and providing appropriate feedback to the user in real-time. A virtual assembly system called SHARP System for Haptic Assembly and Realistic Prototyping is created, which utilizes simulated physical constraints for part placement during assembly.;The first approach taken in this research attempt utilized Voxmap Point Shell (VPS) software for implementing collision detection and physics-based modeling in SHARP. A volumetric approach, where complex CAD models were represented by numerous small cubic-voxel elements was used to obtain fast physics update rates (500--1000 Hz). A novel dual-handed haptic interface was developed and integrated into the system allowing the user to simultaneously manipulate parts with both hands. However, coarse model approximations used for collision detection and physics-based modeling only allowed assembly when minimum clearance was limited to ∼8-10%.;To provide a solution to the low clearance assembly problem, the second effort focused on importing accurate parametric CAD data (B-Rep) models into SHARP. These accurate B-Rep representations are used for collision detection as well as for simulating physical contacts more accurately. A new hybrid approach is presented, which combines the simulated physical constraints with geometric constraints which can be defined at runtime. Different case studies are used to identify the suitable combination of methods (collision detection, physical constraints, geometric constraints) capable of best simulating intricate interactions and environment behavior during manual assembly. An innovative automatic constraint recognition algorithm is created and integrated into SHARP. The feature-based approach utilized for the algorithm design, facilitates faster identification of potential geometric constraints that need to be defined. This approach results in optimized system performance while providing a more natural user experience for assembly

A framework for isogeometric-analysis-based design and optimization of wind turbine blades

Typical wind turbine blade design procedures employ reduced-order models almost exclusively for early-stage design; high-fidelity, finite-element-based procedures are reserved for later design stages because they entail complex workflows, large volumes of data, and significant computational expense. Yet, high-fidelity structural analyses often provide design-governing feedback such as buckling load factors. Mitigation of the issues of workflow complexity, data volume, and computational expense would allow designers to utilize high-fidelity structural analysis feedback earlier, more easily, and more often in the design process. Thus, this work presents a blade analysis framework which employs isogeometric analysis (IGA), a simulation method that overcomes many of the aforementioned drawbacks associated with traditional finite element analysis (FEA). IGA directly utilizes the mathematical models generated by computer-aided design (CAD) software, requires less user interaction and no conversion of CAD geometries to finite element meshes, and tends to have superior per-degree-of-freedom accuracy compared to traditional FEA. The presented framework employs the parametric capabilities of the Grasshopper algorithmic modeling interface developed for the CAD software Rhinoceros 3D. This Grasshopper-based framework enables seamless, iterative design and IGA of CAD-based geometries and is demonstrated through the optimization of both a pressurized tube and a simplified wind turbine blade design. Further, because engineering models, such as wind turbine blades, are typically composed of numerous surface patches, a novel patch coupling technique is presented. For the sake of straightforward implementation and flexibility, the coupling technique is based on a penalty energy approach. Formulations for the penalty parameters are proposed to eliminate the problem-dependent nature of the penalty method. This coupling methodology is successfully demonstrated using a number of multi-patch benchmark examples with both matching and non-matching interface discretizations. Together, these technologies enable practical and efficient design and analysis of wind turbine blade shell structures. The presented IGA approach is employed to perform vibration, buckling, and nonlinear deformation analysis of the NREL/SNL 5 MW wind turbine blade, validating the effectiveness of the proposed approach for realistic, composite wind turbine blade designs. Further, a blade design framework that combines reduced-order aeroelastic analysis with the presented IGA methodologies is outlined. Aeroelastic analysis is used to efficiently provide dynamic kinematic data for a wide range of wind load cases, while IGA is used to perform high-fidelity buckling analysis. Finally, the value and feasibility of incorporating high-fidelity IGA feedback into optimization is demonstrated through optimization of the NREL/SNL 5 MW wind turbine blade. Alternative structural designs that have improved blade mass and material cost characteristics are identified, and IGA-based buckling analysis is shown to provide design-governing constraint information

An incremental constraint-based approach to support engineering design.

Constraint-based systems are increasingly being used to support the design of products. Several commercial design systems based on constraints allow the geometry of a product to be specified and modified in a more natural and efficient way. However, it is now widely recognised the needs to have a close coupling of geometric constraints (i.e. parallel, tangent, etc) and engineering constraints (Le. performance, costs, weight, etc) to effectively support the preliminary design stages. This is an active research topic which is the subject of this thesis. As the design evolves, the size of the quation set which captures the constraints can get very large depending on the complexity of the product being designed. These constraints are expected to be solved efficiently to guarantee immediate feedback to the designer. Such requirement is also necessary to support constraint-based design within Virtual Environments, where it is necessary to have interactive speed. However, the majority of constraint-based design systems re-satisfy all constraints from scratch after the insertion of a new design constraint. This process is time consuming and therefore hinders interactive design performance when dealing with large constraint sets. This thesis reports research into the investigation of techniques to support interactive constraint-based design. The main focus of this work is on the development of incremental graph-based algorithms for satisfying a coupled set of engineering and geometric constraints. In this research, the design constraints, represented as simultaneous sets of linear and non-linear equations, are stored in a directed graph called Equation Graph. When a new constraint is imposed, local constraint propagation techniques are used to satisfy the constraint and update the current graph solution, incrementally. Constraint cycles are locally identified and satisfied within the Equation Graph. Therefore, these algorithms efiiciently solve large constraint sets to support interactive design. Techniques to support under-constrained geometry are also considered in this research. The concept of soft constraints is introduced to represent the degrees of freedom of the geometric entities. This is used to allow the incremental satisfaction of newly imposed constraints by exploiting under-constrained space. These soft constraints are also used to support direct manipulation of under-constrained geometric entities, enabling the designers to test the kinematic behaviour of the current assembly. A prototype constraint-based design system has been developed to demonstrate the feasibility of these algorithms to support preliminary desig

Sustainable Fashion and Textile Recycling

The clothing and textile industry is a resource-intensive industry and accounts for 3 to 10 percent of global carbon dioxide emissions. In addition, the industry is extremely linear and generates large amounts of waste. For the industry to move from a linear to a circular economy, several solutions are required along the value chain: upstream by working with resource efficiency, the longevity of textile products, and preventing waste; and downstream with techniques for sorting and recycling. In addition, solutions for traceability and transparency need to be developed and coordinated as accepted methods for sustainability measurements. This Special Issue (SI) "Sustainable Fashion and Textile Recycling" brings together areas of knowledge along the textile value chain to highlight the difficulties and opportunities that exist from both a broader perspective and in specific issues. In this SI, these 11 papers are mainly devoted to new research in traceability, design, textile production, and recycling. Each valuable article included in this Special Issue contributes fundamental knowledge for a transformation of the textile and fashion industry to take place. Numerous studies, solutions, and ideas need to be carried out to create the innovations that will become the reality of our future. Likewise, we need to learn from each other and take advantage of all the fantastic knowledge that is generated globally every day towards a better future for generations to come

Smart automated computer-aided process planning (ACAPP) for rotational parts based on feature technology and STEP file

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe concept of smart manufacturing comprises high levels of adaptability with rapid design changes, digital information technology, and more data training. This differs from traditional manufacturing, which depends on constant inputs for the generation of process planning to manufacture a part or requires human intervention if any of the input changes. Smart manufacturing has become a vital issue in the manufacturing industry since the start of the twenty-first century, in terms of time and production cost. One of the most effective concepts for achieving a smart manufacturing industry is the use of Computer-Aided Process Planning (CAPP) which is the key technology that connects Computer-Aided Design (CAD) and the Computer-Aided Manufacturing (CAM) processes. A lot of effort has been spent taking CAPP systems to the next upgraded level that is Automated Computer- Aided Process Planning (ACAPP) in order to provide complete information about the product, in a way that is automated, fast, and accurate. One of the most import aspects in creating an ACAPP system is the use of feature technology, as it is the first step in converting the design to manufacturing features. This includes in particular the development of efficient Automatic Feature Recognition (AFR) systems and solving features intersecting issues. The implementation of AFR techniques is an indispensable concept for transferring product data between CAD and ACAPP systems. Different international Product Data Exchange (PDE) standards, such as Drawing Exchange Format (DXF), Initial Graphic Exchange Specification (IGES), and Standard for the Exchange of Product (STEP) files are used to accomplish this purpose. Although many AFR techniques and systems have been developed to serve this aim, each of them has limitations. For example, each system is restricted to recognise a specific set of predefined manufacturing features; hence, if new features are included in the model design, they will not be recognised. In this work, a novel and smart interactive AFR (SI-AFR) system has been proposed for recognising features of rotational parts. A parser has been developed to extract the geometrical and topological information of a part design from a STEP file and to send it to the next steps. Then, the system manipulates the extracted information to facilitate the feature recognition process. During this progression, the system contributes to solving issues considered drawbacks in previous works, such as identifying the convexity and concavity of toroidal surfaces and efficiently isolating faces that belong to holes and internal shapes. Finally, the feature recognition process has been divided into two parts: recognition of predefined features and smart interactive feature recognition. This has been written using C# coding to extract the features’ geometrical and topological information from the STEP file. Whilst the first part of the proposed system has the ability of recognising 54 predefined features, the main contribution of this research is concentrated in the second part of the system which allows new features to be detected, identified, and added to the predefined feature set. This is achieved by extracting the type and specification of each face, the geometrical and topological relation between each two adjacent faces, and the number of the faces that form the new feature. Due to its ability in identifying predefined and new features, it is believed that the system represents a new generation of feature recognition systems. Also, a “features subtraction” system has been created as an optimal solution for complex features intersecting cases. It takes the final manufacturing features from the SI-AFR system as an input. The system has seven steps for analysing, processing, and calculating intermediate features. The intermediate features represent layers of material to be removed, in an optimal sequence. These are recognised by scanning in all directions of the part, to determine the intersecting areas between the final manufacturing features. Such a system provides a whole vision of transferring a blank into the desired shape via step-by-step rough turning, drilling, and boring processes. The results from the SI-AFR and features subtraction systems depend on the geometrical and topological information of the pre-defined and new features. These are analysed for the purpose of automatically generating CAPP outputs, such as the process selection, cutting tools, sequence of operations, and generating G-code. This is to reduce the time and production cost, as well as human intervention, and hence significantly contributes to an organisations efforts in sustainability. The proposed ACAPP system has been practically validated, clearly demonstrating how it surpasses the capabilities of traditional CAM software, since all the outputs are achieved automatically, which CAM software are currently not capable of. The final manufacturing features of the part have been produced accurately, compared to the design features, in terms of specified design dimensions and tolerances. The current version of the system covers rotational symmetrical parts, however this work can be extended to include rotational non-symmetrical and prismatic parts.Republic of Iraq Ministry of Higher Education & Scientific Researc

Ficucs: Ein Constraint-Solver für geometrische Constraints in 2D und 3D

This thesis reflects the results of many years of research and development work in the field of geometric constraints for standard geometries in 2D and 3D. The experiences with constructive as well as numerical approaches for the calculation of constraint-based models have been continuously incorporated into the development of the constraint solver Ficucs. Besides the algorithms and data structures used in Ficucs the thesis describes various applications which use Ficucs as calculation module and corresponding models. The aim was to develop a constraint solver which is usable in many different kinds of projects. The focus was on interactivity and stability of the algorithms, because that is very important for the user's acceptance. A lot of improvements were found, most of them were also implemented and thus verified. It arose that a combination of different concepts in one application is often problematic. The thesis shall make the achieved results accessible to the interested readers and motivate further research work concerning a hybrid approach which combines constructive as well as numerical methods.Die vorliegende Arbeit spiegelt Ergebnisse einer langjährigen Forschungs- und Entwicklungstätigkeit auf dem Gebiet der geometrischen Constraints zu Standardgeometrien in 2D und 3D wider. Die Erfahrungen zu konstruktiven und numerischen Ansätzen für das Berechnen der constraint-basierten Modelle flossen in die Entwicklung des Constraint-Solvers Ficucs ein. Neben den in Ficucs genutzten Algorithmen und Datenstrukturen werden diverse Applikationen, welche Ficucs als Berechnungsmodul nutzen, sowie dazugehörige Modelle beschrieben. Ziel der Tätigkeiten war es, einen in den verschiedensten Projekten einsetzbaren Constraint-Solver zu entwickeln. Besonderes Augenmerk lag auf der Interaktivität sowie der Stabilität der Algorithmen, welche für eine Nutzerakzeptanz sehr wichtig sind. Hierzu wurden immer wieder Verbesserungsmöglichkeiten gefunden, zum Großteil auch implementiert und somit verifiziert. Es zeigte sich, dass die Kombination unterschiedlicher Konzepte in einer Anwendung oft problematisch ist. Die vorliegende Arbeit soll die erreichten Resultate interessierten Lesern zugänglich machen und zu einer weiteren Forschungstätigkeit in Richtung eines hybriden Ansatzes aus konstruktiven und numerischen Verfahren anregen