Intelligent control of an automated adhesive dispensing cell.

Imperial Users onl

An Opto-Electronic Stand-Off Sensor for Robotics

This thesis presents an optoelectronic stand-off sensor and actuation system developed for robotic applications. The measuring principle is based on an on-axis method of detecting variation in a beam reflected from a surface. The sensor utilizes two photodiodes to measure the difference in beam power falling through two pinholes, to estimate the distance between the workpiece surface and incident focused beam waist. The output voltage from the differential stage is normalized to negate the effects of surface reflectivity, colour, and texture. Two mathematical models are presented which simulate the device. The first depends only on the theory of propagation of gaussian beams, whilst the second relies upon simulating the reflected beam using geometrical optics to calculate the radiometric distribution at the detecting pinholes. A set of experiments were performed to analyze and optimize the performance of a number of sensor configurations. The experimental results are bounded between gaussian and radiometric model results. A comparison of the results of the three models, conclusions regarding sensor performance and principles for optimally designing such systems are given. A proportional control circuit for one sensor servo combination was designed and tested using a solenoid as an actuator. The predicted performance of the complete servo system was modelled utilizing the ACSL language. While an experimental rig was built and experiments designed to analyze the output of the system in response to a step input. The results of this show that the stand-off system gives varying response to different materials indicating that the electronic method of normalizing the sensor output is insufficient. The results also show that the device is sensitive to controller gain and behaves in a non-linear fashion as predicted. The actual response is generally faster than the predicted response. Conclusions and recommendations for further work and development are given

A conceptual framework for success factors required for a South African SME foundry.

Doctoral Degree, University of KwaZulu-Natal, Durban.South Africa has witnessed an unprecedented decline in the number of foundries over the past four decades, with literature reflecting that there has been about 73 percent reduction in the number of foundries in South Africa in this period. The purpose of this research is to investigate the contribution of four sets of factors, which are: entrepreneur’s individual characteristics, internal non-individual factors, external-non individual factors, and operational approaches of a foundry as definitive of success. The research also sought to establish intervention measures that could be implemented to make these foundries more sustainable. Through hypothesis testing, the research also sought to establish relationships between the four sets of factors and intervention measures. The target population was 117 small and medium enterprise foundries in South Africa. Sample sizes were 303 participants for the quantitative strands and 11 participants for the qualitative strand. Judgemental purposive sampling was employed for the qualitative strand and cluster sampling for quantitative strand. Two questionnaires were the only tools used for collecting data, one personally administered for the qualitative strand, and another administered online for the quantitative strand. Convergent mixed methods approach was employed, where both qualitative and quantitative data was collected, analysed, and compared to identify where the two strands converged. The factors upon which the two data strands converged were accepted as the success factors required to effectively run an SME foundry in South Africa. Structural equation modelling and thematic analysis were used for data analysis of quantitative and qualitative strands respectively. It was verified that intervention measures had a positive relationship with the entrepreneur’s individual characteristics, external non-individual characteristics, and operations approach of SME foundries. The hypothesis of a relationship between intervention measures and internal non- individual characteristics of a foundry was not supported, hence it was rejected. Ultimately, a framework outlining the success factors and intervention measures required as well as their relationships was postulated. This research contributes to the novel knowledge on success factors required to run SME foundries through the suggested framework. In the penultimate, recommendations and suggestions for future studies are proffered

Jig-Less Assembly for Aerospace Manufacture

Due to the high level of investment required to compete successively in the global aerospace and automotive markets, these industries are forced to form partnerships wherever possible and thereby share their resources appropriately. This in turn has brought about the requirement to provide a standardized flexible design and manufacturing capability in which interchangability and compatibility may take place. Current assembly practices and associated tooling can be traced back to the earliest days of aircraft production and have become relatively expensive and inflexible in today’s environment. The final assembly stage has been recognized to be a key area which has the potential to offer substantial returns as well as play a major role in any change management process within the organisation. Assembly tooling, jigs and fixtures, are required to support and maintain positional accuracy of components during assembly. Traditional jigs and fixtures make up for the short comings at the product design and manufacturing phases and add significantly to the final product costs and reduce flexibility in the production process. Jig-Less Assembly Concept (JAC) has been defined and researched with the aim to integrate and optimize various tools and techniques with which to reduce or eliminate the assembly tooling currently in use. The outcome of the research presents a comprehensive critique of the processes involved in and pertaining to the assembly of typical airframe assemblies. The thesis forms a platform from which to move forward towards the embodiment of the concept of jig-less assembly. Particular attention is drawn from the research to the need for appropriate organisational and management strategies as well as technical innovation in the adoption of a jig-less approach to airframe assembly. Together with BAe Airbus and Military this collaborative research seeks to define the scope of JAC by identifying and evaluating the issues and constraints, to enable the development of supportive techniques in unison with best practice engineering within a robust and sustainable manufacturing system. This commercially focused R & D required liaison and working at all levels within a variety of industrial sites using live case studies at Filton and Chester.MPhi