Jared Padayachee

MODULAR RECONFIGURABLE MACHINE TOOLS: DESIGN, CONTROL AND EVALUATION

The reconfigurable manufacturing system (RMS) paradigm encapsulates methodologies that enable manufacturing systems to cope effectively with market and product changes. This research presents the design and evaluation of modular reconfigurable machine (MRM) tools as a novel machining solution within the scope of RMS. Mechanical and control designs are presented, outlining the development of this novel machining system. The property of hardware modularity displayed by MRMs enables an adjustment of system functionality and the synergistic redistribution of system resources between production streams, thus facilitating inter-process capacity scaling. Scalable production capacity and adjustable system functionality are the key objectives of reconfigurable manufacturing.

Identification of the breast edge using areas enclosed by iso-intensity contours

The segmentation of a mammogram into background and breast is a crucial first step in the computer aided diagnosis of mammograms that has the advantage of simplifying further processing of the image (by eliminating the background) and also provides a reference for the alignment of views when two views are being compared. A novel method of segmenting the breast from the background by analysing the area enclosed by iso-intensity contours is presented. Results are evaluated by comparison with manual borders drawn by three radiologists for a set of 25 mammograms. The effect of different pre-processing methods, on the accuracy of automated borders, is investigated. The best methods yielded average root-mean-square differences between the manual and automated iso-intensity borders of 3.0+/-0.3 mm for the image set containing clear breast edges and 4.8+/-0.5 mm for the image set containing indistinct breast edges compared to 5.1+/-0.8 and 7.9+/-0.9 mm for the two data sets with no pre-processing. Results are also compared to those obtained from global thresholding.

Modular Reconfigurable Machines Incorporating Modular Open Architecture Control

The reconfigurable manufacturing system (RMS) paradigm has been formulated to encapsulate methodologies that enable manufacturing systems to display a variability of system functionality and capacity in response to constantly changing production requirements. The formulation of a new class of production machinery, modular reconfigurable machines (MRMs), for RMS is presented. By virtue of their fully modular nature these machines are able to display a variability of machining functions and cutting degrees of freedom on a single platform. A corresponding modular open architecture control (OAC) system is presented. OAC overcomes the inflexibility of fixed proprietary automation, ensuring that MRMs provide the reconfigurability and extensibility necessary to meet the demands of modern manufacturing.

A MULTI-PERIOD GROUP TECHNOLOGY METHOD FOR DYNAMIC CELLULAR MANUFACTURING SYSTEMS

A dynamic cellular manufacturing system is a system where cell configurations change in order to respond to changing production requirements. This paper proposes methods for multi-period cell and part family formation. The method of fuzzy C-means clustering is used for part family formation while balancing the part load between cells in each period; a genetic algorithm is presented to solve the model. An integer programming model is presented for multi-period cell formation with the objective of determining an optimal trade-off between reconfiguration cost and the cost of deficit capacity.

A thin, hardware-supported middleware management system for reconfigurable manufacturing systems

The reconfigurable manufacturing system (RMS) paradigm was introduced in response to the need for a manufacturing environment that can handle high-frequency market-driven change. Although this has resulted in much research into the implementation of such a system, there is currently a gap in the technology covering the rapid establishment of control after a reconfiguration. This gap involves the detection of the factory floor’s state, and the communication link between the factory floor and the high-level software (ERP and MES). This paper proposes a thin, hardware-supported middleware management system to support the reconfiguration process and to support industrial implementation to the RMS paradigm.

THE DESIGN OF RECONFIGURABLE ASSEMBLY STATIONS FOR HIGH VARIETY AND MASS CUSTOMISATION MANUFACTURING

The economical production of mass customised and high variety goods is a challenge facing modern manufacturers. This challenge is being addressed, in part, by the on-going development of technologies that facilitate the manufacturing of these goods. Existing technologies require either excessive inbuilt flexibility or frequent changes to the machine set up to provide the manufacturing functions required for the customisation process. This paper presents design principles for automated assembly stations within the scope of mass customisation. Design principles are presented that minimise the hardware and operating complexities of assembly stations, allowing stations to be easily automated for concurrent mixed model assembly with a First In First Out (FIFO) scheduling policy. A reconfigurable assembly station is developed to demonstrate how the proposed design methods simplify the creation and operation of an assembly station for a product family of flashlights. OPSOMMING Die ekonomiese vervaardiging van grootskaalse aangepaste en hoe verskeidenheid goedere is ‘n uitdaging wat hedendaagse vervaardigers in die gesig staar. Die uitdaging word deels geadresseer deur die ontwikkel van tegnologiee wat die vervaardiging van hierdie goedere fasiliteer. Bestaande tegnologiee vereis egter uitgebreide ingeboude aanpasbaarheid of gereelde veranderinge aan die masjienopstelling, om die vervaardigingvermoe deur die aanpassings proses vereis, te verskaf. Hierdie artikel hou ontwerpbeginsels voor vir geoutomatiseerde monteerstasies binne die bestek van massa aanpasbaarheid. Die ontwerpbeginsels minimeer die hardeware- en bedryfkompleksiteit van monteerstasies. Hierdie benadering vergemaklik dit om stasies te outomatiseer vir gelyklopende gemengde model montering met ‘n Eerste-In-Eerste-Uit (FIFO) skeduleringsbeleid. ‘n Herkonfigureerbare monteerstasie is ontwikkel om te demonstreer hoe die voorgestelde ontwerpbeginsels die skep en bedryf van ‘n monteerstasie vir ‘n produk-familie van

Combined Use of the Area under the ROC Curve and a measure of Contrast to Evaluate Template Matching Similarity Metrics

Template matching is a common method used in medical image analysis to determine how similar regions in a test image are to a given reference image. For the matching, a reference image is moved across a test image and a measure of similarity is computed at each position. This process results in a similarity map, which indicates how well the reference image is matched to the test image at each position. The strength of any template-matching algorithm lies in the similarity metrics used. A novel method is presented for the comparison of the matching performances of various similarity metrics, incorporating the area under the receiver operating characteristic (ROC) curve and a measure of contrast, both computed from the similarity map. The area under the ROC curve is a standard method of evaluating the performance of computer-aided diagnosis systems and provides a measure of how much of the reference image has been correctly matched, with values close to 1 being preferred. The measure of contrast provides an indication of how well the correctly matched regions stand out from the background in the similarity map and values close to 1 are preferred. These two measures are combined to define a quantity known as “matching accuracy”, which ranges from −1 to 1 and is chosen to only be positive when contrast and area under the ROC are both positive. “Matching accuracy” allows quantitative evaluation of the matching performance of similarity metrics and an example of its use, to assess the matching performance of two similarity metrics (Euclidean distance and mutual information), is presented. The similarity metrics are applied to the template matching of pairs of mammographic images and “matching accuracy” is also used to investigate the effect on matching performance of several algorithm parameters (e.g. sampling window size and bit depth).

A MULTI-STAGE OPTIMISATION METHOD FOR THE MANAGEMENT OF AN ON-DEMAND FIXTURE MANUFACTURING CELL FOR MASS CUSTOMISATION PRODUCTION SYSTEMS

The implementation of reconfigurable fixtures is a major facilitator of mass customisation. Traditional scheduling techniques do not consider reconfigurable fixtures comprehensively. This paper describes a multi-stage optimisation method that manages the recirculation of reconfigurable fixtures in a mass customisation production system. The method was based on an on-demand fixture manufacturing cell that served a part processing cell. The method consists of three stages: using established techniques such as k-means clustering and hierarchical clustering; and a novel mixed integer linear programming (MILP) model to optimise operation sequences. Minimisation of total idle time (and thus makespan) was used as the measure of performance.

A method for optimising the evolution of cellular manufacturing systems

Cellular Manufacturing Systems (CMS) are a central concept in just-in-time and lean manufacturing. Although CMS are able to provide a strategic operating advantage, machine cell clusters do not remain optimal over an extended period of time. This paper presents a method for planning the evolution of the CMS over a multi-period horizon, such that the machine cell clusters are periodically reconfigured to provide good performance. The method uses the concept of fuzzy-clustering for part family generation and a mixed integer linear program for the assignment of machine resources to cells. The results show that the evolving cells are significantly more competitive than fixed configurations.

Optimal Scheduling of an on-Demand Fixture Manufacturing Cell for Mass Customisation Production Systems - Model Formulation, Presentation and Validation.

A focal point of mass customisation production systems (a significant aspect of the fourth industrial revolution) is the implementation of reconfigurable jigs and fixtures. Traditional methods for the treatment of conventional fixtures are inadequate for those of the reconfigurable type. This paper describes the implementation of an on-demand fixture manufacturing cell that would reside in a mass customisation production system. The focus, in particular, is on the behaviour and optimisation of this cell in relation to the production system. To achieve this, a multi-stage optimisation procedure was developed that involves cluster analysis and a mixed inter linear programming (MILP) model to minimise total idle time (and thus makespan) in the system.