Department of Mechanical and Mechatronic Engineering
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Browsing Department of Mechanical and Mechatronic Engineering by browse.metadata.advisor "Basson, A. H."
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- ItemAlternative methods of material handling within a reconfigurable manufacturing station.(Stellenbosch : Stellenbosch University, 2017-03) Deacon, Matthew Marc; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis contributes to evaluating methods of material handling within a reconfigurable manufacturing station, as alternative to a six degree of freedom articulated robot arm. This research follows the design process of formulating the design requirements, considering different concepts and evaluating them, designing a selected concept in detail, validating the concept using test data and then applying the concept to a broader application. A few material handling methods are briefly considered before focusing on the use of a Cartesian robot. Different configurations of a Cartesian robot were considered. As part of the design analysis, a model was developed which allows for the input of various station parameters and provides an estimate of the station’s throughput and cost. This estimation model was implemented in MathCAD and split into two parts: a throughput estimate and a cost estimate. The inputs into the model are the process module configuration and the target kinematics. The model includes load and force calculations for each axis and component selection, as an input to the cost estimate. A control system was developed, based on the PROSA architecture and implemented in C#. The design and implementation of this control system is discussed in this thesis. To be able to validate the research results, a case study is used as an example implementation of the material handling method. However, the design is not limited to the case study, but rather provides a model for any process station with similar transport requirements. The model was validated using a test setup in the Automation Laboratory that uses Festo components. The model therefore only provides for Festo components at this stage, but can easily be expanded upon if other manufacturers are to be considered. After the model was validated, it was applied to the case study, including drive selection, to provide an estimate throughput and cost. These estimates are then compared to previous research that used a six degree of freedom articulated arm robot for a similar case. Other applications, different from the case study, of the model are also discussed.
- ItemAn architecture for the digital twin of a manufacturing cell(Stellenbosch : Stellenbosch University., 2020-03) Redelinghuys, Anro Johannes Hermanus; Kruger, Karel; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The ongoing development of modern manufacturing technology contributes to the rise of the fourth industrial revolution, or Industry 4.0. The digital twin is considered to be key for interaction between the virtual and physical worlds. An important step towards the success of Industry 4.0 is the establishment of practical reference architectures. The dissertation presents the development, implementation and evaluation of the Six-Layer Architecture for Digital Twins with Aggregation (SLADTA). The development starts with the SLADT (excluding aggregation) for a single manufacturing system element, with an industry related case study. The SLADT provides the communication between the physical and digital twin, as well as between the digital twin and the outside world. The architecture is aimed at situations where the products of various vendors are used in the physical and digital twins, and for developing digital twins for newly designed and legacy manufacturing systems. Layers 1 and 2 of the SLADT form part of the smart connection level or physical twin. An Open Platform Communications Unified Architecture (OPC UA) server in Layer 3 provides a vendor-neutral communication interface between the physical twin and the other layers. The data-to-information conversion level, or IoT Gateway, is added as Layer 4 to add context to the data received from Layer 3 before passing the information to Layer 5. When information flows from higher levels to the physical twin, Layer 4 also converts the information to data that can be used by the physical twin. Layers 5 and 6 are the cognition level of the architecture. Layer 5 consists of cloud services that host historical information received from Layer 4. Layer 6 consists of simulation and emulation tools. This dissertation also extends the SLADT, by also providing for Aggregation (SLADTA) and evaluates it for a laboratory scale manufacturing cell that consists of a variety of physical twins. A hierarchical approach is considered for aggregating information from lower- to higher-level digital twins. This approach can also be considered as a digital twin of twins that reduces complexity by breaking a larger digital twin into smaller digital twins of encapsulated functionality. The OPC UA server (Layer 3) supports and simplifies the secure information flow between digital twins, while the IoT Gateway (Layer 4) supervises the information flow. The evaluation of the SLADTA considered its ability to acquire the physical twin state (Layers 1, 2, 3 and 4), maintain an information repository (Layer 5), and simulate and emulate operation (Layer 6). The evaluation further considered the data and information flow, configuration, and decision-making capabilities. Latencies between the OPC UA server (Layer 3) and the IoT Gateway (Layer 4) were identified during the SLADT case study evaluation and had a significant impact on the real-time communication. The latency considerations, between Layers 3 and 4, are evaluated in this dissertation. This dissertation concludes that the SLADTA provides a functional mechanism to implement digital twins. The layers in the SLADTA are not platform dependent and thus allow flexibility for integration into newly designed and legacy manufacturing systems.
- ItemAn ARTI Holonic architecture implementation for table grape production management.(Stellenbosch : Stellenbosch University, 2021-03) Rossouw, Johan Joubert; Kruger, Karel; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The management of table grape production is complex, since it must adhere to strict production requirements, facilitate numerous decisions by various experts, and integrate many human workers. With the ever increasing market demands, the table grape industry needs to adopt new technologies in order to stay competitive. The objective of this thesis is to develop a system to aid the table grape production management. The developed system uses the Activity Resource Type Instance (ARTI) reference architecture to implement a holonic production management system, which is able to address the challenges of the table grape production management. The ARTI components and their functionality are explained. The table grape production management is explained to identify the elements that makes up the production management. The mapping of the identified elements to the ARTI components is described in detail before the implementation of the system components are discussed. The developed system is compared to the currently implemented system. The comparison is based on three key aspects of the table grape production manage system– communication, information management and decision support. The comparisons are drawn according to the functionality of each system to initiate, monitor, change and cancel a production order. The results show that a production management system based on the ARTI reference architecture is able improve on the communication, information management and decision support of the currently implemented system. The developed system is also robust against disturbances and is flexible and adaptable to react to production order changes.
- ItemAspects of distributed conceptual design support(Stellenbosch : Stellenbosch University, 2002-04) Schueller, Andreas; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The findings of an investigation into the requirements of a support system for distributed conceptual design in small and medium enterprises are presented. Distributed conceptual design refers to the collaboration of spacially distributed design teams during the early stages of the product development process. Three main elements of a support system were identified. The first element, 'Design Methodology', places a framework for specification development, functional analysis, concept generation and concept evaluation at the designers' disposal. It systematically guides the users through the different steps of the design process. These steps can be performed either alone, or together with other team members. The users are also aided in documenting their steps in order to allow the team members or designers of followup projects to understand the decisions made. The second element, 'Communication and Information Transfer', co-ordinates the communication between the distributed designers and provides a platform for the exchange of design-related data, e.g. customer requirements, ideas, sketches, comments, and decisions. A case study was carried out to assess the use of various tools for communication and information transfer during synchronous and asynchronous collaboration. The case study is described and the results are presented and discussed. Both elements make use of a support service providing various 'Input Devices for Conceptual Design', the third element of a support system. While standard tools such as mouse and keyboard meet the requirements of subsequent stages of the design process, they are often impractical in creating or annotating sketches. Various low-cost input devices were investigated. A framework was developed to integrate the three elements into one support system. The 'Distributed Design Assistant', abbreviated as 'DiDeas', is an Internet-based system that allows simultaneous multi-user collaboration. A relational database is located on a central web-server and stores all design information entered into the system. The user interface was realized in the form of a collection of Microsoft Active Server Pages, which can be accessed platform-independently via a standard webbrowser. The development of the database structure and of the user interface is described in detail. A second case study was carried out to evaluate the Distributed Design Assistant. The case study is described and the results are presented and discussed. The low-cost system has proven to be a very useful tool for distributed conceptual design. The Distributed Design Assistant systematically guides novice and experienced designers through the stages of specification development and conceptual design. It facilitates the easy collection and the fast exchange of a large amount of textual and graphical information during these stages. Although the system is relatively simple, compared to professional product data management systems used in later stages of the design process, it strongly enhances the productivity of designers and distributed design teams. Keywords: Distributed Design, Conceptual Design, Systematic Product Development
- ItemAspects of linking CAD and cost estimation software(Stellenbosch : Stellenbosch University, 2001-12) Liu, Yang; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis describes a module that links AutoCAD and CeDeas (cost estimation software which was developed by Department of Mechanical Engineering, University of Stellenbosch). CeDeas is intended for estimating the direct manufacturing cost of simple welded assemblies in a batch production environment. It is aimed at use during late concept design or early detail design. The link module was developed in Borland C++ Builder. By using COM (Component Object Model) technology, the link module employs the methods and the properties of the AutoCAD automation interface to extract manufacturing information that is required by CeDeas. The link module prompts the user to pick objects in an AutoCAD drawing and then determines the values required by CeDeas to estimate the manufacturing cost. The user can choose between a "direct select method" (which uses the properties of geometric entities already in the drawing) and a "user define method" (whereby the user defmes temporary entities or combines aspects of existing entities in the AutoCAD drawing). With these results and some non-geometric inputs, the user can get a cost estimate of components and assemblies. After design changes, the link module can provide CeDeas with updated values with minimal user interaction in situations where the "direct select method" was used. The designer can therefore easily use the cost estimates to compare design alternatives to optimise the design. Validation studies demonstrated the numerical accuracy of the use of the link module. The link module can be regarded as an extension of CeDeas. At present it only supports AutoCAD R14, but can be extended to support AutoCAD 2000 and Mechanical Desktop.
- ItemConceptual design of a fixture-based reconfigurable spot welding system(Stellenbosch : University of Stellenbosch, 2009-03) Sequeira, Michael Allan; Basson, A. H.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.This thesis details the conceptual design of a fixture-based, reconfigurable, automated spot welding system aimed at manufacturing various sub-assemblies of circuit breakers. The welding operations are currently done using manual welding equipment, making this stage of the assembly process highly labour intensive. A range of product models and variants are assembled in quantities requiring frequent change-overs. Low-cost automation within a developing country’s manufacturing industry, more specifically within the Republic of South Africa, is the target context. The chosen design restriction, of incorporating a part fixturing design approach, distinguishes this research from F. S. D. Dymond’s work, who addressed the same problem while restricted to a fixtureless assembly approach. A conceptual layout design was developed to address part feeding, manipulation, transportation, fixturing and welding requirements, for an entire breaker model range. A simulation model for three possible layouts of the selected conceptual design provided a means to investigate each layout’s ability to tolerate and balance variation in production requirements, and to establish objective comparative performance data. This showed that the optimal configuration consists of four single loop layout systems. The thesis concludes that the final concept possesses the flexibility to produce the primary product range. Reconfiguration for production beyond this range is assisted by the modular nature of the layout. Ultimately, a reconfigurable design should focus on a properly selected base of core product ranges, providing an expandable and reusable system. The system can be supported by manual assembly stations which handle highly variant, incompatible product ranges.
- ItemConceptual design of a fixtureless reconfigurable automated assembly system(Stellenbosch : University of Stellenbosch, 2009-12) Dymond, F. S. D.; Basson, A. H.; Kim, Y.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The conceptual design of a fixtureless reconfigurable automated spot welding system for manufacturing subassemblies for residential circuit breakers was investigated. This research was aimed at developing a possible low cost automation alternative to a South African industrial manufacturer, which is presently heavily dependent on personnel for manual assembly of their core products. System reconfiguration allows for the assembly of a range of subassemblies with geometric component variation on a given system configuration, as well as the potential for the system to be reconfigured to assemble other ranges of circuit breaker subassemblies. The subassembly selected as focus consists of six different components, which vary geometrically from one product variant to another. A fixtureless approach was selected, to minimise reconfiguration down time and the need for reconfigurable fixtures since reconfigurable fixtures have not found significant acceptance in industry. This varies from a fixture-based approach, which was considered in related research. The conceptual assembly system presented here consists of the following modules: a flexible vision based part feeder, twin 6 DOF robotic manipulators each with a multipurpose gripper, and a stationary spot welding station. Critical conceptual design elements were further investigated to refine their selection and confirm feasibility with respect to the target industry application. This process ended with a preliminary cost estimate which served as a basis for comparison between the fixtureless, fixture-based and present manual assembly process. The fixtureless concept was overall more expensive than the fixture-based concept, primarily because of the limits to production throughput. The fixtureless concept was however cheaper than the present manual assembly approach but had a far longer payback period than desired by the industry. The complexity and possible uncertainties of the concept combined with the long payback period indicated that the fixtureless concept is not suitable for the target application.
- ItemControl of a conveyor system for a reconfigurable manufacturing cell(Stellenbosch : Stellenbosch University, 2013-12) Le Roux, Anro; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This work entails a study of the control software of transportation systems for use in recon gurable manufacturing systems (RMSs). Various control approaches are considered, with the focus on enhancing recon gurability. The work is unique in the sense that the RMS is designed to manufacture small parts/products and is meant to be used in developing countries. Manufacturing systems that can ensure product quality and delivery, are a critical need in countries where the bulk of manufacturing systems function with manual labour. RMSs and holonic manufacturing systems (HMSs) are identi ed as concepts that can potentially compete with manual manufacturing systems. The competing system must thus have a low initial adoption risk, be able to adapt to changing product functionality and demands, and have a comparable throughput rate. IEC61311-3, IEC64199 function block and agent-based control architectures are evaluated. The control software is tested on an experimental conveyor system. The thesis shows that IEC61131-3 and IEC64199 architectures are advantageous in lower levels of control. IEC64199 function blocks provide human interface and development tools and simpli es the distribution of control. The human interface and development tools of IEC64199 function blocks may prove bene cial in providing system monitoring and rapid low skilled adaptation of the control system, increasing recon gurability of systems in under-developed countries. Unfortunately, the low maturity of the development environments for IEC64199 function blocks is a limitation. It is shown that an IEC64199 function block controller becomes complex as the actuator/sensor count exceed 10. Agent-based systems o er reliable control and powerful communication tools but requires a higher level of expertise than IEC64199 function blocks. Agent-based systems are proposed for the core high level control. Complex systems can be controlled with agents and intelligence can be added to control systems in a recon gurable way. For the recon gurable control of large manufacturing systems, agent-based control was found to be superior to IEC64199 function blocks.
- ItemControl of reconfigurable assembly system(Stellenbosch : University of Stellenbosch, 2010-12) Adams, Azeez Olawale; Basson, A. H.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This work considers the control of reconfigurable assembly systems using a welding assembly system as a case study. The assembly system consists of a pallet magazine, a feeding system, an inspection and removal system, a welding system and a conveyor. The aim of the work is to compare PC and PLC as controllers, as well as to compare two different approaches to reconfigurable control. The control system of the pallet magazine was developed using a PC and a PLC. The PC control was programmed using Visual C#, while the PLC was programmed in Ladder Logic using Siemens S-300 STEP7. The two controllers were compared based on the attributes that measure the quality of a controller's software, which include its capability, availability, usability and adaptability. The approaches to reconfigurable control considered were the agent-based methodology and the IEC 61499 distributed control methodology, both of which were applied to the feeding system. The agent-based control system was implemented using the JADE agent platform, while the IEC 61499 distributed control system was implemented using the FBDK software kit. These two methods were compared based on the characteristics of a reconfigurable system, which include the system's modularity, integrability, convertibility, diagnosability, customization and scalability. The result obtained in comparing the PC to the PLC shows that the PLC performs better in terms of capability, availability and usability, while the PC performs better in terms of adaptability. Also, the result of the comparison between the agent-based control system and the IEC 61499 distributed control system shows that the agent-based control system performs better in terms of integrability, diagnosability and scalability, while the IEC 61499 distributed control system performs better in terms of modularity and customization. They are, however, on a par in terms of convertibility.
- ItemControl of the feeder for a reconfigurable assembly system(Stellenbosch : Stellenbosch University, 2013-03) Kruger, Karel; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis documents the research conducted into the control of the feeder subsystem of a Reconfigurable Assembly System (RAS). The research was motivated by a new set of modern manufacturing requirements associated with an aggressive and dynamic global market. The motivation can be more specifically attributed to the need for selective automation, through the installation of reconfigurable systems, in the South African manufacturing industry. The objective of the research was to implement and evaluate Multi-Agent Systems (MASs) and IEC 61499 function block systems as potential control strategies for reconfigurable systems. The control strategies were implemented for the control of the feeder subsystem of an experimental RAS at Stellenbosch University. The subsystem's hardware consisted of a singulation unit with a machine vision camera, part magazines and a six DOF pick-'n-place robot. The structure of the control strategies is based on the ADACOR holonic reference architecture. The mapping of the subsystem holons to the structures of the control strategies is explained. The development and implementation of the control strategies, along with the accompanying lower level software, is described in detail. A system reconfigurability assessment was performed and the results are discussed. The assessment was performed at two levels – the Higher Level Control (HLC) (where the control strategies were implemented) and the low level control and hardware. The assessment was done through four reconfiguration experiments. The evaluation of the HLC was done through both quantitative and qualitative performance measures. The implications of the reconfiguration, involved in each of the respective experiments, on the low level software and hardware are discussed. The experimental results show that agent-based control adds more reconfigurability to the feeder subsystem than IEC 61499 function block control, and that agents have more advantages regarding customizability, convertibility and scalability than IEC 61499 function blocks. Also, the ability of agent-based control to implement reconfiguration changes during subsystem operation makes it more suitable to the case study application.
- ItemCost model for bipolar plate manufacture(Stellenbosch : Stellenbosch University, 2012-12) Atkinson, Juan Pablo; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis gives a cost model for the manufacture of bipolar plates in South Africa. The methods for the manufacture considered are machining, using a micro-milling machine, and compression moulding. The focus of this thesis is on compression moulding. Details of the work done towards developing and validating the models are described, and then the cost models are discussed in detail. The results of the analysis done using the cost model is given with attention paid to the effect of changing design parameters, such as channel size and flow field area, and of the cost of production for both methods over various production volumes. The thesis concludes that compression moulding becomes the better option for production volumes greater than 324 bipolar plates, with a cost that eventually reaches close to R140 per plate for high enough production volumes (over 5000). The cost to produce 1000 plates using compression moulding is estimated at R294 per plate. An increase of the channel size gives a small reduction in the total cost, while the increase in cost with an increase in flow field area is large.
- ItemCritical evaluation of predictive modelling of a cervical disc design(Stellenbosch : University of Stellenbosch, 2007-12) De Jongh, Cornel; Basson, A. H.; Scheffer, C.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.This thesis is concerned with the simulation of the in vivo biomechanical performance of a cervical disc replacement. A representative (averaged) maximum range of motion (ROM), determined by measurement of 10 student participants (5 male, 5 female), was used as head motion input to a simulation model of the cervical spine containing a disc implant at the C5/C6 intervertebral level. Intradiscal pressure, relative applied force on the C5 vertebrae, bending moments and vertebral rotations were recorded. The force and motion components of the results obtained were critically evaluated against the ISO and ASTM experimental protocol standards, probing the representativeness of these standards to the actual in vivo behaviour of the cervical functional spinal unit. Further, the wear resulting from a lifetime (10 million cycles) of the ISO prescribed -and simulation determined input cycles was simulated using a linear wear model with a triangulation technique for volume lost due to wear, and compared to in vitro results in the literature. The inputs used for the wear model were determined from a validated non-linear static contact finite element method (FEM) model. The simulation “chain” shows great potential as a comparative tool for the preexperimental testing of spinal implant designs and may be used with relative success as an alternative to expensive prototype testing.
- ItemData Analytics for predictive maintenance of Wind Turbines.(Stellenbosch : Stellenbosch University, 2021-12) Devenish, A.; Basson, A. H.; Kruger, K.; Grobler, J.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: There is a global drive for using greener energy sources for power generation, for which wind energy is a popular alternative. Significant investment is thus attracted to wind farm development. However, research into wind farm management is required to improve the economic viability of wind turbines, and maintain wind energy as a competitive source for electricity generation. Elements of wind farm management that contribute significantly to the overall costs of operating wind farms, are maintenance and repair operations. Maintenance and repair operations constitute 20-25% of the total levelised cost of wind turbines. Decreasing these costs would thus greatly contribute to improving the operating costs of wind farms. The research in this thesis investigates the detection of wind turbine failures to aid the contribution of preventative measures that can be taken to decrease the total levelised cost of wind turbines. The objective of this thesis is to evaluate the use of data analytics for predictive maintenance of wind turbines. Therefore, the thesis presents a review of predictive maintenance solutions found in literature, as well as a case study which demonstrates the use of various data analytic techniques for predictive maintenance of wind turbines. In the case study, various machine learning algorithms are evaluated for predicting failures in wind turbines by two broad approaches - classification and regression. The classification approaches predict whether a failure will occur in a certain time period, while regression approaches estimate the time until a failure occurs. The best performing algorithm for classification in the case study was the support vector machine (SVM), and for regression the random forest. The classification and regression models were evaluated using recall and precision, and root mean squared error (RMSE), respectively. Binary and multiclass experiments were performed for both classification and regression approaches. The binary predictions provided failure warnings without an indication of which component was going to fail, whereas the multiclass experiments made separate failure predictions for each component category. A conclusion drawn from the multiclass predictions is that the failure categories have different predictabilities, as some showed to be more successfully predicted than others. Knowing which component is going to fail is valuable to wind farm operators because they can immediately focus on implementing preventative measures for that specific problem in the turbine. The time required to locate the cause of the failure warning, inspect and fix what is faulty, and return the turbine to normal operation again, will therefore be reduced. From the outcomes of this thesis, it is concluded that for the dataset used in this research, regression is the most reliable approach for predicting failures in wind turbines. Even though the multiclass cases' data was more severely imbalanced than the binary cases, the multiclass failure predictions were better for some components than the binary case predictions: the binary case's RMSE was 30.9 hr, while the multiclass errors ranged from 10.2 hr for transformer failures to 21.4 hr for hydraulic group failures.
- ItemDesign analysis of a lomolding machine(Stellenbosch : University of Stellenbosch, 2007-12) Goussard, Charl Leonard; Basson, A. H.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.This dissertation describes the design analysis of a lomolder (a machine similar to an injection moulding machine). It focuses on key design aspects that will drive the purchase cost of the machine and that will also influence the maintenance and operating cost. The main objective of the study is to provide an understanding of the key factors that influence the cost of a lomolder as well as the factors that contributes to a quality manufactured part. A semi-analytical flow model was developed to predict cavity pressure drops for a range of part sizes. This model was necessary to eliminate time consuming numeric simulations required for machine optimisation. Numerous machine concept designs were developed and a final layout design chosen. A parametric CAD model was built for the lomolder. Layout designs for different sized lomolders can be generated with this model. The dissertation concludes with a cost study that focuses on the purchase cost of a lomolder unit. Key elements such as choice of actuator and piston to part area ratio are described.
- ItemDesign for manufacture through fabrication : a manufacturing time and cost estimation model for large fabricated assemblies(Stellenbosch : Stellenbosch University, 1998) De Swardt, A. V.; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical & Mechatronic Engineering.ENGLISH ABSTRACT: This thesis concerns the development of manufacturing time and cost estimation models for large mechanical engineering assemblies. The objective of the time and cost models are to serve the design engineer as a tool for estimating manufacturing time and cost, as the design progresses from the conceptual to the detail design stage. The manufacturing time and cost estimation models will give the designer the advantage of evaluating different concepts with time and cost as decision making criteria. The models can also be used as a redesign tool for existing products so that a cost comparison can be made between the existing and new design. The models can also be used as a design optimisation tool for the manufacturing time and cost of a new design or redesign. This will reduce unnecessary costs associated with a certain design Basic process flow diagrams were determined from shop floor practice for each manufacturing process and its secondary process( es). Data for these models were obtained by time studies. The time study data was then used to investigate correlation's between manufacturing time and certain design parameters. Manufacturing time estimation formulae were then developed from the time study data. Five major time and cost estimation models were developed and tested. The five models are: Welding Time Estimation for the Flux Core Arc Welding Process, Tack Welding Time Estimation, CNC Flame Profile Cutting Time Estimation, Manual and Mechanised Bevelling Time Estimation and Plate Bending Time Estimation. Each model depicts the manufacturing time and consumable requirements.
- ItemThe development and evaluation of an Erlang control system for reconfigurable manufacturing systems(Stellenbosch : Stellenbosch University, 2018-03) Kruger, Karel; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The dynamic and highly competitive nature of the modern manufacturing environment has introduced a new set of challenges, urging researchers and industry to formulate new and innovative solutions. The concepts of holonic and reconfigurable manufacturing systems showed great promise to address the challenges. While these concepts could not achieve significant industry adoption, they will play an important role in the latest emerging paradigm in manufacturing – the fourth industrial revolution, or Industry 4.0. Industry 4.0, can potentially have a significant impact on all aspects of the manufacturing industry, aiming to enhance individualization of products through highly flexible production, extensively integrate customers and businesses in valueadded processes and link production and high-quality services to deliver hybrid products. To achieve these goals, Industry 4.0 relies on Cyber-Physical Production Systems (CPPSs) to enhance the connectedness throughout all levels of the manufacturing enterprise. CPPSs aim to enhance the intelligence, connectedness and responsiveness of manufacturing systems. These goals closely resemble those of holonic and reconfigurable manufacturing systems, indicating the relevance of research on these topics to the development and implementation of CPPSs. The objective of this dissertation is to evaluate the suitability of the Erlang programming language as an alternative for the implementation of holonic control in manufacturing systems. The dissertation presents an Erlang-based holonic control implementation for a manufacturing cell. The Erlang implementation is evaluated through a comparison with an equivalent implementation using Multi- Agent Systems (MASs), which is considered as the status quo for holonic control implementation in manufacturing systems research. To accomplish the evaluation of the holonic control implementations, evaluation criteria is formulated. The evaluation criteria focusses on both the development of control implementations and the adoption of the implementations by industry. The criteria identifies a set of quantitative and qualitative performance measures that are indicative of seven critical requirements for holonic control implementations. The Erlang and MAS implementations are evaluated and compared according to these performance measures and requirements. The comparison shows that the Erlang implementation matches the functionality of the MAS implementation and even offers some advantages for the desired characteristics for the holonic control of manufacturing systems. The advantages in availability and supportability can be attributed to the enhanced modularity and fault tolerance of the Erlang implementation. The Erlang implementation also allows for increased development productivity through a reduction in software complexity and simplification of software verification. The findings of the evaluation confirms the inherent suitability of the Erlang programming language for the implementation of holonic control. It is recommended that further research be conducted on the refinement of the architecture and the development of a framework for holonic control implementations in Erlang.
- ItemDevelopment of tailorable mechanical design support software(Stellenbosch : Stellenbosch University, 2013-12) Van der Merwe, Ruan; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: A wide variety of design methodologies exist in literature and the methodologies employed may differ among companies and even among design teams. Therefore a software tool, called DiDeas II, is being developed for the early phases of mechanical engineering design. DiDeas II is customisable to accommodate various design methodologies. An approach for customisability which allows the user interface and data structure to be customised without changing the source code has been implemented in previous developments via an approach combining ontology and conceptual graphs. This approach is expanded in this thesis to allow for the implementation of various design methodologies through the use of tables for the display of information with inheritance of data among these tables. During groupwork, communication is both asynchronous and synchronous. DiDeas II has been developed in this thesis to facilitate and capture both asynchronous and synchronous communication between team members. Capturing such communications has the potential to provide insight into design decisions. The communication functionality was assessed in case studies in an academic environment. DiDeas II proved to be effective at recording “soft” information during design and placing the information into context for future reference. The degree to which DiDeas II could be customised to suit the design process at different companies was assessed through discussions with engineers in industry. These discussions showed that it was possible to customise DiDeas II according to the design processes followed by the participants.
- ItemEdge scanning and swept surface approximation in reverse engineering(Stellenbosch : Stellenbosch University, 2001-12) Schreve, Kristiaan; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: Broadly speaking Reverse Engineering is the process of digitising a physical object and creating a computer model of the object. If sharp edges formed by two surfaces can be extracted from a point cloud (which is the set of measured points) it can speed up the segmentation of the point cloud and the edges may also be used to construct swept surfaces (or various other types of surface that best captures the design intent). A strategy is presented to "scan" edges. The strategy simulates a CMM (Coordinate Measurement Machine) as it would scan a sequence of short lines straddling the edge. Rather than measuring on a physical object, the algorithm developed in this dissertation "scans" on the points in the point cloud. Each line is divided in two parts, or line sections, belonging to the surfaces fanning the edge. The points of the line sections are then approximated with polynomials. Each edge point is the intersection of two such polynomials. In many engineering components sharp edges are replaced with fillet radii or the edges become worn or damaged. This algorithm is capable of reconstructing the original sharp edge without prior segmentation. A simple analytical model was developed to determine the theoretically achievable accuracy. This Analytical accuracy was compared with the accuracy of edges extracted from point clouds. A series of experiments were done on point clouds. The input parameters of the experiments were chosen using the technique of Design of Experiments. Using the experimental results the parameters that most significantly influences the accuracy of the algorithm was determined. From the Analytical and experimental analysis guidelines were developed which will help a designer to specify sensible input parameters for the algorithm. With these guidelines it is possible to find an edge with an accuracy comparably with an edge found with the traditional method of finding the edges with NURBS surface intersections. Finally the algorithm was combined with a swept surface fitting algorithm. The scanned edges are used as rails and profile curves for the swept surfaces. The algorithms were demonstrated by reverse engineering part of another core box for an inlet manifold. If the edge detection parameters are specified according to the guidelines developed here, this algorithm can successfully detect edges. The maximum gap size in the point cloud is an important limiting factor, but its effect has also been quantified.
- ItemAn electric actuator selection aid for low cost automation(Stellenbosch : University of Stellenbosch, 2008-03) Egbuna, C. Chukwudi; Basson, A. H.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.Low Cost Automation (LCA) is of immense importance to industry, and even more so for small scale industries. In implementing LCA determining cost effective and efficient actuator alternatives present challenges for design engineers. Most often decisions are experiential or entirely based on manufacturer recommendations. Experience based decisions are most often biased with respect to the engineers’ knowledge. Similarly, manufacturer recommendations are restricted to their own products and are as such also biased. Either way, sub-optimum drive alternatives may sometimes be chosen. This demonstrates the need for making better informed decisions based on more than experience and what is available for use. This thesis reports the development of an electric actuator selection procedure and aid for use in the early layout design phase. It provides readily accessible information on technically viable actuator options. Experiential knowledge of experts in the field, commercial information, as well as data obtained from experimentation was used in its development. Being orientated towards LCA, the procedure has been targeted at the application of electric motors and their associated control technologies but can be extended to hydraulic, pneumatic and other actuators. In achieving a wider applicability of the selection aid, a generic set of actuator properties descriptive of most actuators was formulated. An AC drives control evaluation was conducted for developing the selection procedure and aid. It provided a means to validate some selection aid rules associated with actuator controllability. Quantitative data on speed and positioning accuracies of common AC three phase motors and their associated inverter technologies were the targeted results of the experimentation.
- ItemAn evaluation of a design method for mixed flow fans(Stellenbosch : Stellenbosch University, 2002-03) Du Toit, Jacques H. (Jacques Hendrik); Von Backstrom, T. W.; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: Mixed flow fans find application in an operating region between that of axial flow and centrifugal fans. The candidate investigated the working of these mixed flow fans and formulated a design algorithm. The algorithm was based on work done by previous authors, most of which have tried to modify existing axial flow fan design methods to suit the mixed flow case. A fan was designed, built and tested. Tests showed that the fan did not perform as designed, producing a lower pressure rise at a lower flow rate. A five hole probe was used to measure the exit flow vector and the results showed that most of the work was done by the lower half of the blade. Based on this discrepancy between the designed and actual fan performance, a number of changes to the design procedure were recommended. Amongst other things: the use of numerical blade modelling procedures instead of modified cascade correlations and the disregard of the Coriolis work in the design of the blade shape.