Template-based reverse engineering of parametric CAD models from point clouds

openEven if many Reverse Engineering techniques exist to reconstruct real objects in 3D, very few are able to deal directly and efficiently with the reconstruction of editable CAD models of assemblies of mechanical parts that can be used in the stages of Product Development Processes (PDP). In the absence of suitable segmentation tools, these approaches struggle to identify and reconstruct model the different parts that make up the assembly. The thesis aims to develop a new Reverse Engineering technique for the reconstruction of editable CAD models of mechanical parts’ assemblies. The originality lies in the use of a Simulated Annealing-based fitting technique optimization process that leverages a two-level filtering able to capture and manage the boundaries of the parts’ geometries inside the overall point cloud to allow for interface detection and local fitting of a part template to the point cloud. The proposed method uses various types of data (e.g. clouds of points, CAD models possibly stored in database together with the associated best parameter configurations for the fitting process). The approach is modular and integrates a sensitivity analysis to characterize the impact of the variations of the parameters of a CAD model on the evolution of the deviation between the CAD model itself and the point cloud to be fitted. The evaluation of the proposed approach is performed using both real scanned point clouds and as-scanned virtually generated point clouds which incorporate several artifacts that could appear with a real scanner. Results cover several Industry 4.0 related application scenarios, ranging from the global fitting of a single part to the update of a complete Digital Mock-Up embedding assembly constraints. The proposed approach presents good capacities to help maintaining the coherence between a product/system and its digital twin.openXXXIII CICLO - INGEGNERIA MECCANICA, ENERGETICA E GESTIONALE - Meccanica, misure e robotica01/A3 - ANALISI MATEMATICA, PROBABILITA' E STATISTICA MATEMATICA01/B1 - INFORMATICA09/B2 - IMPIANTI INDUSTRIALI MECCANICIShah, GHAZANFAR AL

User-Driven Computer-Assisted Reverse Engineering of Editable CAD Assembly Models

This paper introduces a novel reverse engineering (RE) technique for the reconstruction of editable computer-aided design (CAD) models of mechanical parts’ assemblies. The input is a point cloud of a mechanical parts’ assembly that has been acquired as a whole, i.e., without disassembling it prior to its digitization. The proposed framework allows for the reconstruction of the parametric CAD assembly model through a multi-step reconstruction and fitting approach. It is modular and it supports various exploitation scenarios depending on the available data and starting point. It also handles incomplete datasets. The reconstruction process starts from roughly sketched and parameterized CAD geometries (i.e., 2D sketches, 3D parts, or assemblies) that are then used as input of a simulated annealing-based fitting algorithm, which minimizes the deviation between the point cloud and the adapted geometries. The coherence of the CAD models is maintained by a CAD modeler that performs the geometries’ updates while guaranteeing the possibly imposed constraints and model coherence. The optimization process leverages a two-level filtering technique able to capture and manage the boundaries of the geometries inside the overall point cloud in order to allow local fitting and interfaces detection. It is a user-driven approach where the user decides what are the most suitable steps and sequence to operate. It has been tested and validated on both real scanned point clouds and as-scanned virtually generated point clouds incorporating several artifacts that would appear with real acquisition devices

Case‑based tuning of a metaheuristic algorithm exploiting sensitivity analysis and design of experiments for reverse engineering applications

Due to its capacity to evolve in a large solution space, the Simulated Annealing (SA) algorithm has shown very promising results for the Reverse Engineering of editable CAD geometries including parametric 2D sketches, 3D CAD parts and assem blies. However, parameter setting is a key factor for its performance, but it is also awkward work. This paper addresses the way a SA-based Reverse Engineering technique can be enhanced by identifying its optimal default setting parameters for the ftting of CAD geometries to point clouds of digitized parts. The method integrates a sensitivity analysis to characterize the impact of the variations in the parameters of a CAD model on the evolution of the deviation between the CAD model itself and the point cloud to be ftted. The principles underpinning the adopted ftting algorithm are briefy recalled. A framework that uses design of experiments (DOEs) is introduced to identify and save in a database the best setting parameter values for given CAD models. This database is then exploited when considering the ftting of a new CAD model. Using similar ity assessment, it is then possible to reuse the best setting parameter values of the most similar CAD model found in the database. The applied sensitivity analysis is described together with the comparison of the resulting sensitivity evolution curves with the changes in the CAD model parameters imposed by the SA algorithm. Possible improvements suggested by the analysis are implemented to enhance the efciency of SA-based ftting. The overall approach is illustrated on the ftting of single mechanical parts but it can be directly extended to the ftting of parts’ assemblies. It is particularly interesting in the context of the Industry 4.0 to update and maintain the coherence of the digital twins with respect to the evolution of the associated physical products and systems

A framework for hull form reverse engineering and geometry integration into numerical simulations

The thesis presents a ship hull form specific reverse engineering and CAD integration framework. The reverse engineering part proposes three alternative suitable reconstruction approaches namely curves network, direct surface fitting, and triangulated surface reconstruction. The CAD integration part includes surface healing, region identification, and domain preparation strategies which used to adapt the CAD model to downstream application requirements. In general, the developed framework bridges a point cloud and a CAD model obtained from IGES and STL file into downstream applications

DIG-MAN: Integration of digital tools into product development and manufacturing education

General objectives of PRODEM education. Teaching of product development requires various digital tools. Nowadays, the digital tools usually use computers, which have become a standard element of manufacturing and teaching environments. In this context, an integration of computer-based technologies in manufacturing environments plays the crucial and main role, allowing to enrich, accelerate and integrate different production phases such as product development, design, manufacturing and inspection. Moreover, the digital tools play important role in management of production. According to Wdowik and Ratnayake (2019 paper: Open Access Digital Tool’s Application Potential in Technological Process Planning: SMMEs Perspective, https://doi.org/10.1007/978-3-030-29996-5_36), the digital tools can be divided into several main groups such as: machine tools and technological equipment (MTE), devices (D), internet(intranet)-based tools (I), software (S). The groups are presented in Fig. 1.1. Machine tools and technological equipment group contains all existing machines and devices which are commonly used in manufacturing and inspection phase. The group is used in physical shaping of manufactured products, measurement tasks regarding tools and products, etc. The next group of devices (D) is proposed to separate the newest trends of using mobile and computer-based technologies such as smartphones or tablets and indicate the necessity of increased mobility within production sites. The similar need of separation is in the case of internet(intranet)-based tools which indicate the growing interest in network-based solutions. Hence, D and I groups are proposed in order to underline the significance of mobility and networking. These two groups of the digital tools should also be supported in the nearest future by the use of 5G networks. The last group of software (S) concerns computer software produced for the aims of manufacturing environments. There is also a possibility to assign the defined solutions (e.g. computer programs) to more than one group (e.g. program can be assigned to software and internet-based tools). The main role of tools allocated inside separate groups is to support employees, managers and customers of manufacturing firms focused on abovementioned production phases. The digital tools are being developed in order to increase efficiency of production, quality of manufactured products and accelerate innovation process as well as comfort of work. Nowadays, digital also means mobile. Universities (especially technical), which are focused on higher education and research, have been continuously developing their teaching programmes since the beginning of industry 3.0 era. They need to prepare their alumni for changing environments of manufacturing enterprises and new challenges such as Industry 4.0 era, digitalization, networking, remote work, etc. Most of the teaching environments nowadays, especially those in manufacturing engineering area, are equipped with many digital tools and meet various challenges regarding an adaptation, a maintenance and a final usage of the digital tools. The application of these tools in teaching needs a space, staff and supporting infrastructures. Universities adapt their equipment and infrastructures to local or national needs of enterprises and the teaching content is usually focused on currently used technologies. Furthermore, research activities support teaching process by newly developed innovations. Figure 1.2 presents how different digital tools are used in teaching environments. Teaching environments are divided into four groups: lecture rooms, computer laboratories, manufacturing laboratories and industrial environments. The three groups are characteristic in the case of universities’ infrastructure whilst the fourth one is used for the aims of internships of students or researchers. Nowadays lecture rooms are mainly used for lectures and presentations which require the direct communication and interaction between teachers and students. However, such teaching method could also be replaced by the use of remote teaching (e.g. by the use of e-learning platforms or internet communicators). Unfortunately, remote teaching leads to limited interaction between people. Nonverbal communication is hence limited. Computer laboratories (CLs) usually gather students who solve different problems by the use of software. Most of the CLs enable teachers to display instructions by using projectors. Physical gathering in one room enables verbal and nonverbal communication between teachers and students. Manufacturing laboratories are usually used as the demonstrators of real industrial environments. They are also perfect places for performing of experiments and building the proficiency in using of infrastructure. The role of manufacturing labs can be divided as: • places which demonstrate the real industrial environments, • research sites where new ideas can be developed, improved and tested. Industrial environment has a crucial role in teaching. It enables an enriched student experience by providing real industrial challenges and problems

Experimental Flight Test Management. Optimization procedures and flight test techniques for test time efficiency and cost reduction.

Approaching to flight test is paramount to keep clear in mind that accurate test management is the cornerstone between failure and success. Flight testing remains an essential element of sound air vehicle development. The current emphasis on expanding the use of M&S has been promulgated with the intention that it can help to reduce flight test time and cost, enhance test safety, and increase testing efficiency. The “predict-test-validate” (a.k.a. ”model-test-model”) paradigm is held forth as the most efficient combination of these development tools. In this paradigm the initial modelling and simulation guides the planning and conduct of flight testing, with incremental test results then used to enhance the accuracy and/or fidelity of the simulation before the process is repeated. The cycle would be repeated many times during the course of the test program, especially in an effort to avoid the "fly-fix-fly" paradigm that commonly proves inefficient and trying to avoid future operational shortfalls. Although much of the technical leadership in the NATO aerospace industry and Italian Defence Department insist that M&S is not intended to replace flight testing, there remains concern among flight test practitioners that the result will be an overreliance on simulation. This has a potential for neglecting invaluable empirical test data verifying system performance. In addition, detrimental and potentially hazardous system characteristics may not be uncovered, and overall assessment of vehicle worthiness vis-a-vis its mission will suffer. Appreciation for a sound balancing of flight testing with simulation must be promulgated. In addition, a methodology appears to be needed to help insure this sound balance. The term M&S is taken to include,[1]: Digital models and computer simulations using those models; Mathematical analytical tools such as Computational Fluid Dynamics; Simulated flight testing such as in wind tunnels and engine altitude test chambers; Hardware-in-the-loop simulations; Pilot-in-the-loop simulations, with and without hardware-in-the-loop; In-flight simulation; Other large-scale ground tests. Each of these initially employ simplified system representations that become more complex as the systems engineering process defines the system during the course of development and as test data becomes available to improve model and simulation fidelity and accuracy. Present initiatives are expanding the application of verification and validation of M&S resources to ensure that they function as intended and suitably represent real-world behaviour. Flight testing itself can be considered a simulation if the test article is an experimental system or early prototype, if some internal or external system functions are contrived, and if test conditions do not truly match actual in-service scenarios (such as simulated combat). OT&E flight test relies heavily on constructive simulation and PITL tactical simulations. All this has become more popular as simulation capabilities have increased and flight test budgets and schedules have decreased. However, the flight environment, with systems interacting and with a pilot (perhaps) in control, is not a simulation. Flight test remains the most dynamic and credible medium for collecting actual system performance data. Test management holistic concept is much more, taking into account also the relevant phase of actual test preparation, test matrix identification (totality of test points to be performed), coordination, FTTs set-up, generation of new validation techniques and reporting, of course. The purpose of this thesis work is to show how an accurate test management based on alternative geometry acquisition processes, test matrix generation algorithms, M&S, new FTTs and validation procedures can be used effectively and efficiently to support flight testing. In particular, in order to reduce the scope of the subject activity the focus is kept on a specific branch of the test field known as Store Integration and Safe Separation; the approach could be expanded to other branches of flight test, but customization would be required. The question becomes how much flight testing can really be replaced by simulation before jeopardizing the safety of flight and increasing the cost of simulation prohibitively to make it worthwhile. Simulation is not a panacea for all test problems, but a valuable tool that must be used cautiously and wisely in the course of a test program, the key word is “balance” and its maidservants are “optimization, synchronization and coordination”

A survey on personal computer applications in industrial design process

Thesis (Master)--Izmir Institute of Technology, Industrial Design, Izmir, 1999Includes bibliographical references (leaves: 157-162)Text in English, Abstract: Turkish and Englishxii, 194 leavesIn this thesis, computer aided design systems are studied from the industrial designer's point of view. The study includes industrial design processes, computer aided design systems and the integration aspects.The technical issues are priorly studied, including current hardware and software technologies. The pure technical concepts are tried to be supported with real-world examples and graphics. Several important design software are examined, whether by personal practice or by literature research, depending on the availability of the software.Finally, the thesis include a case study, a 17" LCD computer monitor designed with a set of graphic programs including two-dimensional and three-dimensional packages.Keywords: Computers, industrial design methods, design software, computer aided design

The Naval Architecture of Vasa, a 17th-Century Swedish Warship

The Swedish warship Vasa sank in Stockholm harbor after sailing less than one nautical mile (1.85 km) on its maiden voyage in 1628. The hull was raised in 1961, and after a lengthy conservation and reconstruction process, went on display in a state-of-the-art museum in 1990. The hull is estimated to be 98% intact, making it the oldest intact wooden ship recovered to date. The recovery and remarkable preservation of the hull presents unparalleled archaeological research opportunities. This dissertation recovers and analyzes the methods of naval architecture used to design the hull of Vasa as evidenced in its intact structure. Digital 3D solid modeling software is used to virtually deconstruct the hull to facilitate a nuanced understanding of the design principles that guided the construction of the ship Although Vasa was a Swedish warship constructed in Stockholm, it was designed and built by Dutch shipwrights. In the early 17th century, the Dutch rose to prominence as the premier shipbuilders in Europe. The quality and character of Dutch-built vessels were renowned and Dutch shipwrights were hired to build the merchant fleets and navies throughout Europe. Limited scholarly attention has been given to the methods of naval architecture by which Dutch shipwrights designed their ships. Dutch shipwrights designed and built ships according to orally transmitted principles of design and therefore left little written evidence for their tradition of naval architecture. Vasa presents an unprecedented opportunity to examine the methods used by Dutch shipwrights to design large vessels as they are evident in an intact hull. The results of the analysis contained in this dissertation suggest that Vasa was designed according to proportional and arithmetical methods of naval architecture. The methods are identical or very similar to those described in Nicolaes Witsen’s 1671 treatise on Dutch shipbuilding. While many aspects of Vasa’s hull appear to be derived according to the tradition of naval architecture described by Witsen, certain significant deviations resulted in an atypically narrow hull. The methods of analysis in this dissertation, which highlight digital 3D visualization, mark an attempt to expand the range of analytic and explanatory tools available to nautical archaeologists in the 21st century

Integrated material practice in free-form timber structures

Integrated material practice in free-form timber structures is a practice-led research project at CITA (Centre for IT and Architecture) that develops a digitally-augmented material practice around glue-laminated timber. The project is part of the InnoChain ETN and has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642877. The advent of digital tools and computation has shifted the focus of many material practices from the shaping of material to the shaping of information. The ability to process large amounts of data quickly has made computation commonplace in the design and manufacture of buildings, especially in iterative digital design workflows. The simulation of material performance and the shift from models as representational tools to functional ones has opened up new methods of working between digital model and physical material. Wood has gained a new relevance in contemporary construction because it is sustainable, renewable, and stores carbon. In light of the climate crisis and concerns about overpopulation, and coupled with developments in adhesives and process technology, it is returning to the forefront of construction. However, as a grown and heterogeneous material, its properties and behaviours nevertheless present barriers to its utilization in architecturally demanding areas. Similarly, the integration of the properties, material behaviours, and production constraints of glue-laminated timber (glulam) assemblies into early-stage architectural design workflows remains a challenging specialist and inter-disciplinary affair. Drawing on a partnership with Dsearch – the digital research network at White Arkitekter in Sweden – and Blumer Lehmann AG – a leading Swiss timber contractor – this research examines the design and fabrication of glue-laminated timber structures and seeks a means to link industrial timber fabrication with early-stage architectural design through the application of computational modelling, design, and an interrogation of established timber production processes. A particular focus is placed on large-scale free-form glulam structures due to their high performance demands and the challenge of exploiting the bending properties of timber. By proposing a computationally-augmented material practice in which design intent is informed by material and fabrication constraints, the research aims to discover new potentials in timber architecture. The central figure in the research is the glulam blank - the glue-laminated near-net shape of large-scale timber components. The design space that the blank occupies - between sawn, graded lumber and the finished architectural component - holds the potential to yield new types of timber components and new structural morphologies. Engaging with this space therefore requires new interfaces for design modelling and production that take into account the affordances of timber and timber processing. The contribution of this research is a framework for a material practice that integrates processes of computational modelling, architectural design, and timber fabrication and acts as a broker between domains of architectural design and industrial timber production. The research identifies four different notions of feedback that allow this material practice to form