Doctoral Degrees (Mechanical and Mechatronic Engineering)

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An 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.
Aspects 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
Design 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.
The 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.
Edge 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.
A flexible distributed design assistance tool in early design phases
(Stellenbosch : Stellenbosch University, 2007-12) Liu, Yang; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
ENGLISH ABSTRACT: The globalisation is increasing the complexity of product development in terms of product variants and the range of technologies implemented. It emphasises the requirement for developing various design information support systems for the world market. However, small and medium enterprises that employ a wide range of design procedures may not be able to afford customised information support systems, with the result that there is a need for flexible, i.e. easily adaptable, design support tools. Four case studies were carried out to investigate the requirements for an information support system aimed at the design process and design documents. They indicated that a design information support system aimed at supporting design teams in the pre-detail mechanical design phases should be able to adapt various design methods and handle design information in a flexible way. Flexible here means being applicable over a wide range of contexts and extendable without affecting data already captured. Ontology based approaches are widely applied where diverse information has to be handled. The development of the Internet today also makes a distributed design approach more and more popular for mechanical design. An internet-based design support system called DiDeas II (Distributed Design assistant) was developed here with an ontologybased approach implemented to provide distributed and flexible assistance during concept generation in small companies. The DiDeas II has separate server side and client side programs, which communicate through a TCP/IP connection. DiDeas II allows design teams to manage their design information according to various design methods, to decrease time-delays and to improve communication between team members. These benefits were confirmed in two case studies carried out to evaluate DiDeas II. Keywords: Distributed design; ontology; concept design, web-based system.
The modelling of granular flow using the particle-in-cell method
(Stellenbosch : University of Stellenbosch, 2004-03) Coetzee, Corne J.; Basson, A. H.; Vermeer, P. A.; University of Stellenbosch. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
Granular flow occurs in a broad spectrum of industrial applications that range from separation and mixing in the pharmaceutical industry, to grinding and crushing, blasting, stockpile construction, flow in and from hoppers, silos, bins, and conveyer belts, agriculture, mining and earthmoving. Two totally different approaches of modelling granular flow are the Discrete Element Method (DEM) and continuum methods such as Finite Element Methods (FEM). Continuum methods can be divided into nonpolar or classic continuum methods and polar continuum methods. Large displacements are usually present during granular flow which, without remeshing, cannot be solved with standard finite element methods due to severe mesh distortion. The Particle-in-Cell (PIC) method, which is a so-called meshless method, eliminates this problem since all the state variables are traced by material points moving through a fixed mesh. The main goal of this research was to model the flow of noncohesive granular material in front of flat bulldozer blades and into excavator buckets using a continuum method. A PIC code was developed to model these processes under plane strain conditions. A contact model was used to model Coulomb friction between the material and the bucket/blade. Analytical solutions, published numerical and experimental results were used to validate the contact model and to demonstrate the code’s ability to model large displacements and deformations. The ability of both DEM and PIC to predict the forces acting on the blade and bucket and the material flow patterns were demonstrated. Shear bands that develop during the flow of material were investigated. As part of the PIC analyses, a comparison between classic continuum and polar continuum (Cosserat) results were made. This includes mesh size and orientation dependency, flow patterns and the forces acting on the blade and the bucket. It is concluded that the interaction of buckets and blades with granular materials can successfully be modelled with PIC. In the cases conducted here, the nonpolar continuum was more accurate than the polar continuum, but the polar continuum results were less dependent on the mesh size. The next step would be to apply this technology to solve industrial problems.
Multi-path planning and multi-body constrained attitude control
(Stellenbosch : Stellenbosch University, 2012-12) Okoloko, Innocent; Basson, A. H.; Kim, Y.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
ENGLISH ABSTRACT: This research focuses on the development of new efficient algorithms for multi-path planning and multi-rigid body constrained attitude control. The work is motivated by current and future applications of these algorithms in: intelligent control of multiple autonomous aircraft and spacecraft systems; control of multiple mobile and industrial robot systems; control of intelligent highway vehicles and traffic; and air and sea traffic control. We shall collectively refer to the class of mobile autonomous systems as “agents”. One of the challenges in developing and applying such algorithms is that of complexity resulting from the nontrivial agent dynamics as agents interact with other agents, and their environment. In this work, some of the current approaches are studied with the intent of exposing the complexity issues associated them, and new algorithms with reduced computational complexity are developed, which can cope with interaction constraints and yet maintain stability and efficiency. To this end, this thesis contributes the following new developments to the field of multipath planning and multi-body constrained attitude control: • The introduction of a new LMI-based approach to collision avoidance in 2D and 3D spaces. • The introduction of a consensus theory of quaternions by applying quaternions directly with the consensus protocol for the first time. • A consensus and optimization based path planning algorithm for multiple autonomous vehicle systems navigating in 2D and 3D spaces. • A proof of the consensus protocol as a dynamic system with a stochastic plant matrix. • A consensus and optimization based algorithm for constrained attitude synchronization of multiple rigid bodies. • A consensus and optimization based algorithm for collective motion on a sphere.
Standby redundant control using Erlang/OTP and JADE for a manufacturing cell.
(Stellenbosch : Stellenbosch University, 2019-04) Hawkridge, Greg Thomas; Basson, A. H.; Kruger, Karel; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering (CRSES)
ENGLISH ABSTRACT: In past decades, the manufacturing sector has been characterised by intense competition resulting from globalisation and shifting customer requirements. This has led to the pursuit of approaches and paradigms that better handle the requirements of modern manufacturers. This pursuit has culminated in the recent focus on the Industry 4.0 and Industrial Internet of Things (IIoT) paradigms. The future manufacturing systems envisioned by these paradigms are increasingly complex. The reliability or availability of complex systems is a concern since complexity increases the likelihood of unexpected failure modes. Holonic systems show great promise for managing this complexity, but they may contain holons that represent single points of failure. The availability of these holons can be improved through standby redundancy. This dissertation evaluates the hypothesis that Erlang/OTP provides an effective platform for implementing standby redundancy in a distributed holonic manufacturing cell. Erlang is a functional programming language designed for the development of fault-tolerant soft real-time control systems. The Open Telecom Platform (OTP) is a set of Erlang libraries that simplifies the development of large complex systems. OTP is such a central feature of Erlang that they are typically referred to collectively, as Erlang/OTP. Erlang/OTP’s standby redundancy effectiveness is evaluated in two stages. First, it is evaluated through the implementation of standby redundancy for a monolithic station controller, the performance of which is benchmarked against the claims of an existing commercial solution. This implementation is representative of standby redundancy for singular resource holons. The evaluation shows that the Erlang/OTP implementation can handle the same failure modes as the commercial solution and achieves a similar changeover time. Furthermore, it shows that Erlang/OTP is suitable for implementing standby redundancy at a software level for embedded devices that do not provide such mechanisms at a hardware level. Next, Erlang/OTP’s effectiveness for standby redundancy in a distributed holonic cell controller is evaluated through a case study comparison of an Erlang/OTP implementation and a Java Agent Development (JADE) framework implementation. JADE is a popular Multi-Agent System framework and has in many respects become the de facto standard for holonic control implementations in academic research. The two implementations are compared using a set of quantitative and qualitative criteria. The comparison demonstrates that the Erlang/OTP implementation outperforms the JADE implementation for all the standby-redundant performance metrics. This is attributed to the centrality of fault-tolerance in Erlang and OTP. The comparison suggests that more development effort may be required for a standby-redundant Erlang/OTP holonic implementation, since Erlang/OTP does not contain the same degree of supporting communication and protocol infrastructure as an established framework like JADE. However, Erlang/OTP’s superior performance outweighs this shortcoming and the comparison concludes that Erlang/OTP provides a better platform for implementing standby redundancy than JADE. The findings of both evaluations confirm that Erlang/OTP provides an effective platform for implementing standby redundancy in a distributed holonic controller for a manufacturing cell. Using Erlang/OTP, the ability to combine standby redundancy and holonic control has the potential to improve controller availability for the complex distributed systems envisioned by Industry 4.0 and IIoT.

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Browsing Doctoral Degrees (Mechanical and Mechatronic Engineering) by browse.metadata.advisor "Basson, A. H."

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