Masters Degrees (Mechanical and Mechatronic Engineering)
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Browsing Masters Degrees (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 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 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 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.
- 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.
- 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.
- ItemEvaluation of C# for a station controller in a reconfigurable manufacturing system(2016-12) Graefe, Rainer; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: Reconfigurable manufacturing systems (RMSs) are aimed at dynamic situations, such as varying products, variations in production volume requirements and changes in available resources. RMSs distinguish themselves from other types of manufacturing systems in that they can quickly adapt to a new product being introduced without the need for long reconfiguration times, and can therefore cost effectively produce smaller batch sizes. RMSs in research environments in most cases used Agent Based Control (ABC), but the main automation vendors in the industry do not support ABC. This inhibits the acceptance of RMSs by the industry. For this research, C# was investigated as an alternative to ABC, since C# can provide for many of the functionalities of agents, yet is a more widely known language than ABC. Furthermore, C# is an object-oriented programming (OOP) language and thus possesses characteristics aligned with the core characteristics of reconfigurable manufacturing systems. The focus of this thesis is to determine the suitability of C# for the development of the control software for RMSs. This thesis describes the design, implementation, testing and evaluation of a reconfigurable stacking and buffering station. The controller was implemented in C# and made use of the ADACOR architecture. The physical test-setup was built to evaluate the reconfigurability of the controller in a series of reconfiguration experiments. The thesis showed that the controller could handle all the hardware interfaces without problems, since C# generally simplifies the task of hardware interfacing. OOP characteristics helped making developing and maintaining the code an intuitive task. The stacking station handled all communication with the cell controller correctly, which proved that it could easily be integrated into a distributed control architecture.
- ItemEvaluation of control strategies for reconfigurable manufacturing systems(Stellenbosch : Stellenbosch University, 2013-03) Mulubika, Chibaye; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: The thesis evaluates control strategies for reconfigurable manufacturing systems by using a welding assembly cell as a case study. The cell consists of a pallet magazine, conveyor, feeder subsystem (comprising an articulated robot and singulation unit), welder subsystem (which uses a modular Cartesian robot), and inspection and removal subsystems. The research focuses on control strategies that enhance reconfigurability in terms of structure, hardware and software using agent-based control and the IEC 61499 standard, based on PC control. Reconfiguration may occur when a new product is introduced, as well as when a new subsystem is introduced or removed from the production cell. The overall control architecture is that the subsystems retain no knowledge of the product, but product information resides in the cell controller, while services offered by the subsystems are registered with the directory facilitator of the Java agent platform. The control strategies are implemented on the modular Cartesian weld robot and the cell controller for assembly cell. A layered architecture with low-level control and high-level control is used to allow separation of concerns and rapid changes in both hardware and software components. The low-level control responds in hard real-time to internal and external events, while the high-level control handles soft real-time actions involving coordination of control related issues. The results showed IEC 61499 function blocks to be better suited to low-level control application in distributed systems, while agents are more suited for high-level control. Modularity in software components enhances hardware and software scalability. Additionally, agents can support online reconfiguration of reconfigurable machines.
- ItemEvaluation of Erlang for a stigmergy holonic routing controller(Stellenbosch : Stellenbosch University, 2018-03) Van den Berg, Christopher Sean; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: A reconfigurable manufacturing system (RMS) is a manufacturing paradigm aimed to be able to react to manufacturing uncertainty caused by hardware failures and changes in the global market. Transport systems for RMSs should be able to easily adapt the routing of parts between manufacturing stations, while making optimal use of the transport infrastructure to maximise the RMS's throughput. In this thesis, a holonic routing controller with stigmergy, aimed at a palletised conveyor for an RMS, is developed using Erlang. The objective is to evaluate the suitability of Erlang in implementing a holonic control architecture where a large number of concurrent processes is required within one controller. The routing controller is adapted from architectures found in literature, and uses elements from the product, resource, order, staff architecture (PROSA). The routing controller is a conveyor controller that transfers a pallet from a source to a destination within the conveyor system based on an instruction given by an outside source, such as a user. The conveyor controller makes use of order, resource, feasibility and ant holons to perform the pallet transfer. Order, feasibility and ant holons were each implemented in their own Erlang process within the conveyor controller, while resource holons used three Erlang processes. The conveyor controller was tested in the Mechatronics, Design and Automation Research Group (MADRG) at Stellenbosch University. Higher-level control was performed by interfacing the conveyor controller, described in this thesis, with previously developed lower-level controllers. The results of the testing proved that the controller possessed all the required characteristics of an RMS and could successfully manage pallet traffic within the conveyor system, including avoiding bottlenecks and changing a previously decided route when conveyor segments unexpectedly become available or unavailable. It was found that Erlang is an appropriate programming language to use in implementing the conveyor controller. Erlang possesses built-in functionality that was found to be convenient and useful. With Erlang, it was possible to create and run processes with ease, even when the system was running.
- ItemEvaluation of labview based control for a reconfigurable manufacturing subsystem(Stellenbosch : Stellenbosch University, 2015-03) Masendeke, Darlington M.; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis considers the evaluation of LabVIEW based control for reconfigurable manufacturing systems (RMSs), and in particular for an RMS subsystem. The evaluation used a rivet feeder station as a case study. The architecture of the rivet feeder station included a vibratory bowl feeder, a singulation device, a pick-n-place mechanism and an XYZ positioning table. The objective of the research was to determine whether LabVIEW is a suitable development environment for implementing holonic control. The motivation for considering LabVIEW in this thesis was that other control approaches, such as IEC 61499 function blocks, agent-based control and object-orientated control, that have been used in most RMS research, have not found favour with industry. The PROSA holonic reference architecture was adopted here, with the following holons: Coms Holon, Request Manager Holon, Order Holon, Product Holon Manager, Pick-n-Place Holon and XYZ Table Holon. The holons, constituting the controller, were designed based on LabVIEW’s producer/consumer and state machine architectures. The controller was aimed at making the rivet feeder station reconfigurable. Furthermore, the controller was interfaced with a cell controller through a TCP/IP connection and an XML format of messaging was adopted for communication. The main limitations and disadvantages of LabVIEW, for the implementation of holonic control systems, were found to be: the graphical programming which makes the block diagram cumbersome to follow, for complex applications; and that dynamic instantiation of objects or memory cannot be achieved in LabVIEW. However, LabVIEW holds the following advantages: shared variables and TCP/IP components simplify communication over a network; easy construction of the graphical user interface using controls and indicators on LabVIEW front panels; the XML standard format in LabVIEW provides flexibility to create your own unlimited tags; and immediate compilation of LabVIEW programs. Furthermore, LabVIEW easily can be integrated with hardware such as the compactRIO with a CANopen card. The reconfigurability assessment of the rivet feeder station included three experiments which involved changing the product type, adding new devices and performing station diagnostics. From these experiments, it was concluded that the key characteristics of reconfigurable manufacturing systems were achieved, thereby demonstrating the suitability of LabVIEW for implementing holonic control.
- ItemEvaluation of vision-based robot control configurations for reconfigurable assembly(Stellenbosch : Stellenbosch University, 2016-03) Steed, Clint Alex; Basson, A. H.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis considers vision based robot control for a reconfigurable manufacturing cell. Reconfigurable manufacturing systems are aimed at rapidly adapting to fluctuations in market demand, shorter product life cycles and product customization. Computer vision is a promising component of such manufacturing systems, in particular aiding the flexibility to handle a range of products with reduced set-up time and fewer fixtures. The objective of the research presented here was to develop a simulation-based approach to compare eye-in-hand and fixed camera vision-based control within a reconfigurable assembly cell. These configurations have dissimilar system costs and system performance characteristics. The research used a KUKA six degree of freedom articulated arm robot, a DVT Legend 540 camera and a Cognex ism-1100 camera, as well as the software supplied with the cameras. The simulation was aimed at predicting the throughput rate of multiple eye-in-hand and fixed camera configurations, where configurations include varying the numbers of reconfigurable singulation units, positions of machines, parts being singulated, etc. The throughput rates for different configurations can then be compared to their costs and ease of reconfiguration. The simulation uses a holonic control system that was designed based on the ADACOR architecture. The thesis describes in detail the holons used, including their hardware, data structures and responsibilities. A multi-agent system was implemented for high-level control and some of the agents communicated with their respective lower-level controllers during validation testing. In the simulation, software (including KUKA Simpro and some custom software) replaced the hardware and low-level controllers. Tests on a number of physical laboratory configurations were used to validate the simulation. The simulation's application is demonstrated in a number of experiments in which cell configurations and machine performance were varied. For example, for a particular situation simulated, these experiments showed that the eye-in-hand configuration has a competitive cost to performance ratio when tasks have a significant waiting period (pallet exchange time, tasks deployed sparsely, etc.). In most experiments, however the fixed camera configuration performs better. The simulation allowed “hardware in the loop” testing, which also makes it a useful tool for development of the cell.