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The Faculty of Engineering at Stellenbosch University is one of South Africa's major producers of top quality engineers. Established in 1944, it currently has five Engineering Departments.
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Browsing Faculty of Engineering by browse.metadata.type "Conference Paper"
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- ItemAdaptive estimation of speech parameters(IEEE, 1994) Basson, J. A. L.; Du Preez, J. A.Linear predictive coding (LPC), and transformations of it, is currently the most popular way of analysing speech signals. Major limitations of using a frame-based technique are that each frame is analysed in isolation of the rest while assuming the excitation source to be a white noise process. In order to reduce computation time, an all pole model is usually employed. In this project an adaptive algorithm is proposed for speech signal analysis. The algorithm is based on the recursive least squares method with a variable forgetting factor. A pole-zero model is used to estimate the anti-formants present in certain sounds (i.e. nasals and nasalized vowels). This method offers better detection of poles and zeros in stationary environments and faster tracking of pole and zero frequencies in nonstationary signals than other sequential methods. An effective input estimation algorithm eliminates the influence of pitch on the parameter estimates by assuming the input to be a white noise process or a pulse sequence.
- ItemAn adaptive transportation prediction model for the informal public transport sector in Africa(IEEE, 2014-10) Ndibatya, I.; Booysen, Marthinus J.; Quinn, J.The informal public transport sector in Sub-Saharan Africa is responsible for transporting the overwhelming majority of the workforce. Often, passengers have to wait for hours for taxis to coincidentally pass by to pick them up, making the transport mode notoriously inefficient. Despite its relevance and impact, the sector is afforded little attention in terms of regulation, development and organization, giving rise to a complex and inefficient system that affects millions of people. In fact, little is known about the industry. To advance understanding of this system, minibus taxis were equipped with tracking devices in this study. Tracking data was then used to develop a model that describes the transport network – essentially finding patterns in the apparent chaos for the potential benefit of its users. The adaptive model uses unsupervised learning to predict the informal stages in the city and provide travelers with intelligence on the best time and place to get transport, thereby reducing the waiting time at the taxi rank and the informal roadside stops. Experimental results show 70.4% model accuracy in dynamically learning the taxi behavior and accurately predicting the best places to get taxis at a given time of the day.
- ItemAgent based job scheduling for a vehicle engine reconditioning machine shop(Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Nyanga, L.; Van der Merwe, A. F.; Burawa, M.; Matope, S.; Dewa, M. T.ENGLISH ABSTRACT: Job scheduling at a machine shop is a multi-decision criteria problem whose skills are acquired after some years of experience. For Small, Medium to Micro Enterprises (SMMEs) with limited machinery the objective when scheduling jobs should not only focus on machine utilization but also on the increase of job through put. The paper presents an agent based job scheduling system for a vehicle engine reconditioning machine shop to assist decision makers in job scheduling. The Analytic Hierarchy Process (AHP) method was used to compute the relative weights of each decision criteria used for job scheduling considering the job priority. The value of the job, the number of operations to be performed, the engine type, the frequency of the customer and the company to customer relationship rating are used to prioritize the jobs. A Multi Agent System (MAS) comprising of the provider, job allocator and machine agents is developed using the Java Agent development framework (JADE) methodology and modelled using Unified Modelling Language (UML 2). The provider agent schedules all the jobs based on job weight and earliest due dates. The job allocator agent is responsible for making sure that all the scheduled jobs are allocated to all the machines after which they are registered as complete jobs and can leave the system.
- ItemAn AHP-based evaluation of maintenance excellence cirteria(South African Institute for Industrial Engineering, 2014) Tendayi, Tinashe George; Fourie, CorneliusENGLISH ABSTRACT: A state of Maintenance Excellence is when an organisation has achieved best maintenance practice standards and has reached the benchmark for the performance of maintenance operations. Various models exist in literature that highlight what elements need to be present in an organization in order to achieve maintenance excellence standards. However, these standards have to be prioritised according to the current state of the organisation’s operations. The Analytic Hierarchy Process (AHP) is a technique that is useful in establishing the priority and importance of individual decision-making alternatives through pairwise comparisons. In this study, the AHP process is used to evaluate a set of organisation-specific maintenance excellence criteria. A railway rolling stock maintenance organisation in the Western Cape region of South Africa is used as a case study for this exercise. By applying AHP to the results obtained from a survey conducted at the case study, some inconsistencies were found in the judgments made by the respondents. AHP was then used again to revise these judgments to make them more consistent. The end result of the study was a set of weighted and prioritized maintenance excellence criteria which will be useful in the organization’s endeavors to attain maintenance excellence.
- ItemAlignment of a functional innovation strategy(Stellenbosch : Stellenbosch University, Department of Industrial Engineering, 2011-09) Katz, B. R.; Du Preez, N. D.; Schutte, Corne S.L.For a strategy to be successful it first needs to be the correct strategy then it needs to be aligned with the business values, structures, capabilities and other strategies and finally it needs to be executed [1]. This paper focuses, specifically, on the alignment of a company’s functional innovation strategy. The connection between the different levels of innovation strategy and other business strategies are developed and explained. A range of different business strategy classifications are presented from the literature and a golden thread of alignment is sewn from a company’s grand, strategic perspective down to its functional strategies. A theoretical framework is presented, which contains the strength of the relationships between different generic strategic perspectives and the components of a functional innovation strategy. The end result of this paper is a suggested decision framework which a company can use to align its functional innovation strategy with its strategic perspective, which in turn should be aligned with the company’s mission and vision. This will enable the company to assign the correct resources to its innovation activities so that innovation enables it to achieve its overall objectives. The decision framework is tested in theory by focusing on the insurance industry and understanding the interaction between the strategic perspectives of a company and that company’s focus on innovation. Evidence is gathered to support assumptions about the company’s innovation focus.
- ItemAnalysis of a time based and corrective maintenance system for a sugar producing company(South African Institute for Industrial Engineering, 2014) Chindondondo, Brian; Nyanga, Lungile; Van der Merwe, Andre Francois; Mupinga, Tapiwa; Mhlanga, SamsonENGLISH ABSTRACT: The Southern Africa sugar producers’ market is under threat from Brazilian sugar, with the latter’s sugar landing in Southern African countries - Zimbabwe in particular – at 75% of the selling price of local producers. This paper outlines an investigation of the current maintenance systems of a Zimbabwean sugar producer and its shortcomings, with a view of optimization. Research has shown that maintenance can contribute between 15 to 75% of production costs, thus playing a critical role in product pricing and consequently competition. Maintenance records and interviews to maintenance personnel from the company were used to extract data relevant to the study. A bottleneck asset in the production line was chosen as a subject to measure the impact of the current maintenance system in cost terms. The study shows that the company is using a hybrid of time based and corrective maintenance. The paper also shows that the current maintenance philosophy resulted in downtime of eighty (80) hours on the subject asset over a four (4) year period, that translated to an equivalent of USD1.9 million in potential revenue lost; which downtime could have been avoided with better maintenance methods. The paper concludes by recommending the introduction of Condition Based Maintenance on the subject asset as an alternative to optimize the maintenance function of the company.
- ItemAnalytical prediction of rotor eddy current loss due to stator slotting in PM machines(IEEE Xplore, 2001-08) Wills, Dominic A.; Kamper, Maarten J.Certain types of PM electric machines are particularly susceptible to the proliferation of eddy currents flowing within the solid conducting regions in the rotor. These eddy currents can be induced by current winding harmonics, but also by the interaction of the static rotor magnetic field with the permeance variation of the slotted stator known as ‘slotting’. This work focuses on the analytical calculation of eddy current loss that occurs in the conducting regions within a rotor under no-load conditions. The results are compared with finite element analysis and measured results from a machine test. Good agreement is achieved between the three methods of comparison.
- ItemAuditory intelligent speed adaptation for long–distance informal public transport in South Africa(IEEE, 2016-04) Ebot Eno Akpa, N. A.; Booysen, Marthinus J.; Sinclair, M.ENGLISH ABSTRACT: Informal transport refers to the collective passenger road transport industry with little or no regulatory control of its operations, usually characterised by unplanned and ad-hoc service delivery. The notoriously dangerous informal transport industry in South Africa – dominated by minibus taxis – has been shown to disregard the posted speed limit on long-distance trips. Not only do they frequently exceed the differentiated speed limit imposed on minibus taxis, but also the speed limit imposed on normal passenger vehicles. This paper evaluates the impact of an auditory Intelligent Speed Adaptation (ISA) intervention, applied at various intensity levels, on the speeding behaviour of this seemingly intransigent mode of transport. The experiment evaluates the behaviour on the R61 between Beaufort West and Aberdeen. We evaluate the speeding distributions, speeding frequencies, speed percentiles, mean speeds, and the statistical relevance of key metrics. We find that the auditory intervention has a clear impact on speeding behaviour, both when applied at an audible level that can be drowned out by a radio, and even greater impact at a loud level. The impact on speeding is significant, with speeding frequency (both time and distance) reducing by over 20 percentage points.
- ItemAutomated landing of an intelligent unmanned aerial vehicle in crosswind conditions using total energy control(2014-12-10) Le Roux, C. T.; Engelbrecht, J. A. A.ENGLISH ABSTRACT: This paper presents the development, implementation and verification of a flight control system for the automated landing of an intelligent unmanned aerial vehicle (UAV) in crosswind conditions. There is an increasing number of commercial opportunities for UAVs in business, agriculture, industry and mining, the emergency services and security services. The major barrier to commercialisation of UAVs is the certification process, where automated take-off and landing is a key feature required. The automated landing system presented in this paper uses a longitudinal control system based on the total energy control system (TECS), and a lateral control system that combines a heading and guidance controller with a cross-track error controller. A software state machine is used to advance the flight control system through the different stages of the automated landing. The TECS architecture allows the airspeed and flight path angle to be decoupled, while the Cross-Track Controller uses a limited integrator to drive the cross-track error to zero in the presence of crosswind. The automated landing system is implemented on a UAV with an on-board computer, sensors and actuators, and is verified in simulation and with practical flight tests. The hardware simulation results show that the UAV is able to land autonomously in crosswinds up to 3.6 metres per second, with a landing accuracy of 3.50 metre in-track and 0.12 metre cross-track.
- ItemBusiness models for sustained eHealth implementation : lessons from two continents(Computers & Industrial Engineering Conference Proceedings, 2012-07) Van Dyk, Liezl; Wentzel, M. Jobke; Van Limburg, A.H. Maarten; Van Gemert-Pijnen, Lisette; Schutte, Corne S. L.; CIE42 ProceedingsThere is general consensus that Computers and Information Technology have the potential to enhance health systems applications, and many good examples of such applications exist all over the world. Unfortunately, with respect to eHealth and telemedicine, there is much disillusionment and scepticism. This paper describes two models that were developed separately, but had the same purpose, namely to facilitate a holistic approach to the development and implementation of eHealth solutions. The roadmap of the Centre for eHealth Research (CeHRes roadmap) was developed in the Netherlands, and the Telemedicine Maturity Model (TMMM) was developed in South Africa. The purpose of this paper is to analyse the commonalities and differences of these approaches, and to explore how they can be used to complement each other. The first part of this paper comprises of a comparison of these models in terms of origin, research domain and design principles. Case comparisons are then presented to illustrate how these models complement one another.
- ItemCapacitive seat sensors for multiple occupancy detection using a low-cost setup(IEEE -- Institute of Electrical and Electronics Engineers, 2013-02) Zeeman, Adriaan Siebrits; Booysen, Marthinus J.; Ruggeri, Giuseppe; Lagana, BrunoThe Minibus public transportation sector and road safety remains a significant challenge in Africa. We propose a low cost system to monitor the taxi industry and encourage safe driving. A low cost capacitive proximity sensor for seat occupancy detection based on the loading mode capacitive sensing technique is designed. The capacitive sensor uses a single electrode to detect an occupant. We use ZigBee modules for a dynamic wireless system integration where sensors can be added or removed without modifications. A mathematical model of the capacitive sensor is developed and we determine the capacitance on the sensor’s electrode. The occupied capacitance is double the unoccupied capacitance. Our results show that the proposed capacitive sensor can distinguish clearly between an unoccupied and occupied seat.
- ItemCharacteristics of single layer selective laser melted tool grade cemented tungsten carbide(Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering., 2016) Van Staden, A. C.; Hagedorn-Hansen, D.; Oosthuizen, G. A.; Sacks, N.Cemented carbide tools, specifically tungsten carbide based alloys, have found a wide range of application fields including manufacturing, agriculture, and mining, among others. A need for customised tooling solutions using cemented carbide alloys have been identified. Additive manufacturing is chosen as a novel manufacturing process due to its superior material and process flexibility. The study investigates the melting behaviour observable during the SLM process using a tool grade cemented tungsten carbide powder. The laser power, scan velocity, and hatch spacing of the SLM process are varied and single powder layers are sintered accordingly. This is done to determine the varying influence these parameter combinations have on the melting behaviour of the material during sintering. For each set of parameter combinations the test samples were analysed using microscopic imaging. It is found that a combination of high laser power, high hatch spacing, and low scan speed yields the best results.
- ItemCommunication in a LabVIEW based holonic controller(Faculty of Engineering, Department of Industrial Engineering, Stellenbosch University, 2016) Masendeke, D. M.; Basson, A. H.ENGLISH ABSTRACT: This paper presents a communication approach for a holonic controller developed in LabVIEW. The controller is aimed at station that forms part of a reconfigurable assembly cell. The objective of the research was to evaluate the extent to which LabVIEW facilitates reconfigurability in this context. The holons were implemented by using LabVIEW’s producer/consumer (to achieve asynchronous inter- and intra-holon communication) and state machine architectures. The paper discusses some implementation considerations. The paper shows that LabVIEW offers some attractive facilities for lower levels of reconfigurable control systems.
- ItemA comparison of Quad-tree and Voronoi-based spatial partitioning for dynamic load balancing(2014-12) Van Greunen, M.; Engelbrecht, H. A.ENGLISH ABSTRACT: Massively multi-user virtual environments (MMVEs) face scalability challenges, one being the large number of concurrent users interacting in the virtual environment (VE). Spatial partitioning addresses this problem by distributing partitions of the VE, and their associated users, to separate servers. Users dynamically migrate between partitions as they move within the VE and server load imbalances occur when users flock to popular locations (such as cities or boss arenas). Dynamic Load Balancing can be achieved by dynamically scaling the VE partitions and migrating users to underloaded servers. In this paper, we assume an MMVE has load balancing and focus on comparing two spatial partitioning methods, namely Quad-trees and Voronoi diagrams, using OverSim, an extension of the OMNeT++ simulation package. We evaluate each approach using the number of messages sent between servers, the distribution of users across servers and the number of servers in use as performance metrics. We conclude that a Voronoi based system is better in distributing the load across multiple servers, but has a greater computational cost than a Quad-tree based system.
- ItemComparison of return on investment for an entry level micromilling machine versus benchmark state of the art machines(South African Institute for Industrial Engineering, 2013-07) Dirkse van Schalkwyk, T. G.Entry level micromilling machines have a substantially reduced capital cost, and lower operating costs associated with them, compared to the state of the art micromilling machines. This paper presents the decision making process and complexity of comparing these two technologies given part requirements, time constraints and part features. Some decisions are trivial, while others require an in-depth understanding of the economics and technical aspects of the technology and the product. Insights gained from research and manufacturing of Micromilled parts are discussed as well as aspects that could impact a techno-economic model. The model aspects are then related to various product sectors each with an estimated market size. One of the outputs of the paper is a business decision framework to guide investors.
- ItemA comparison of simple low-power wedge-type X-band waveguide absorbing load implementations(IEEE, 2007-11) Stander, T.; Van der Walt, P. W.; Meyer, P.; Steyn, W.Two inexpensive waveguide absorbing loads are constructed and measured, each using a single thin resistive sheet absorber supported by styrofoam walls, and 50mm in length. It is found that a V-cut wedge displays less reflection than a tapered wedge, with -30 dB reflection across a band 8.5 - 12.4 GHz.
- ItemA concept demonstrator for self-organising demand-driven inventory management in pharmaceutical supply chains(South African Institute for Industrial Engineering, 2018) Du Plessis, Marno; Van Vuuren, Jan H.; Van Eeden, JoubertENGLISH ABSTRACT: Perennial stock-outs of essential medicines are commonplace in the pharmaceutical supply chains of developing countries. Stock-outs are mainly attributed to a general lack of collective information sharing in pharmaceutical supply chains. In this paper, a computerised agent-based simulation model concept demonstrator is proposed and demonstrated hypothetically as part of a larger drive to establish the value of leveraging information sharing in pharmaceutical supply chains with a view to enhance decision-making. The objective of this paper is to outline the prerequisite research inputs, design requirements and hypothetical implementation of the aforementioned demonstrator. The work reported on in this paper remains a work in progress.
- ItemConsidering the need for alternative intervention strategies for the management of diabetic policy formulation in South Africa(South African Institute for Industrial Engineering, 2018) Thomas, Victoria Val; De Kock, Imke H.; Bam, LouzanneENGLISH ABSTRACT: The increasing prevalence of diabetes in South Africa, alongside other non-communicable diseases, places a heavy burden on the health care system; especially when faced with the significant difference in quality of care between private and public health care, and the increased burden of disease. This paper analyses various diabetic policies already implemented in South Africa, and considers the need to investigate alternative policies and intervention strategies to manage diabetes in South Africa. Due to the complex nature and non-linear interactions which exist within the health care system, a system dynamics-based approach is suggested as a useful analysis tool to evaluate and understand the dominant factors that influence the effective management of diabetes to potentially inform more effective and efficient diabetic policy formulation.
- ItemContemporary wind generators(Energy Research Centre, 2015) Akuru, Udochukwu Bola; Kamper, Maarten J.It is believed that wind energy is growing at a very rapid rate, especially in the last few years. When compared with other sources of renewable energy in the energy portfolio, it becomes evident that the bulk is wind energy-based. However, there are some backlogs to full manifestation of this technology ranging from initial high cost to performance and reliability issues, among others. But in spite of these bottlenecks, new research trends have been assertive in seeking out a sustainable solution for harnessing wind energy for power generation -especially in the design and construction of wind generators. In order to motivate and prime a sustainable energy mix among stakeholders, this paper is a shot at appraising the theory of these innovative wind generators towards ecological sustainability, economy, efficiency, and employment creation.
- ItemCorrelation and causation : a potential pitfall for efficient asset management(South African Institute for Industrial Engineering, 2014) Heyns, Johannes Hendrik; Vlok, P. J.ENGLISH ABSTRACT: The successful coordination of activities and practices within a system rely on the organisation’s ability to make informed decisions. Decisions must be made quickly and effectively, while ensuring efficient Physical Asset Management (PAM). Access to processed data, in the form of reliable information, on how sub systems interact greatly simplifies decision-making. Many organisations mistake correlation for causation when analysing this data. Such a mistake carries great consequences for organisations, since important decisions might unknowingly be based on self-invented problems, while the true problem is left unresolved. It is crucial to understand the difference between correlation and causation when practising root cause analysis within a PAM environment. Although root cause analysisis presumed a highly specialised field, organisations can equip themselves to better understand how different events within a PAM system are interconnected. If done correctly this might simplify the process of detecting problems, which might exist within a system.This paper highlights the differences between correlation and causation. Potential pitfalls on how correlation can be mistaken for causation within a PAM environment are identify and explained. Recommendations are made on how to avoid these pitfalls.