Doctor of Philosophy (Ph.D.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/8871

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item: Thesis-Abstract
An advanced trajectory planner for industrial robot manipulators
(2014-08-22) Munasinghe, SR
This thesis focuses on trajectory planning for industrial robot manipulators. It describes the existing problem of trajectory planning and proposes an appropriate solution. The proposed solution has been devised, implemented and verified for effective functionality. Trajectory planning in this context is the process of planning time-based joint position trajectories for a desired end-effector motion. It needs to consider all relevant constraints of the manipulator and given task specifications; because the final end-effector performance totally depends on the way the joint trajectories are planned. However, most trajectory planners in industrial robotics, even today, have adapted the technique of direct sampling of the desired end-effector motion, and transform such Cartesian positions to joint space using inverse kinematics. Then, the planned joint trajectories are simulated to check if they are realizable within the constraints. It is also inspected if the given task specifications are fulfilled sufficiently. Planned end-effector trajectory is iteratively adjusted by trial-and-error, until an optimum trajectory is obtained. This process has many demerits and it is therefore necessary to develop an appropriate trajectory planning algorithm which has provisions to consider constraints and task specifications in planning end-effector trajectories. It should also be generally applicable to industrial manipulators. Through constant collaboration with Yaskawa Robotics Inc., the major considerations of trajectory planning were identified as being : 1. trajectory allowance, 2. sharp corners, 3. joint acceleration limit, 4. assigned end-effector velocity, 5. Jerk reduction, and 6. delay dynamics. They were considered one-by-one, and techniques were developed to incorporate them into a single trajectory planner. Usually, desired end-effector trajectory is not the optimal trajectory. Therefore, the trajectory planner plans a realizable trajectory with the mentioned considerations above. Realizable trajectory is the optimal trajectory within the given trajectory allowance. At sharp corners, a circular arc is introduced within the trajectory allowance. Joint acceleration limit refers to the power amplifier current rating of the servo controller, and assigned end-effector velocity is the speed specification. End-effector trajectory can be planned using maximum joint acceleration as long as the end-effector remains below the assigned velocity. However, as the end-effector reaches assigned velocity, joint accelerations should be reduced and the speed should be uniformly maintained. Jerk can be reduced by fitting a spline approximation to the planned joint trajectories. Delay dynamics can be compensated by way of pole placement techniques and optimizing the pole by considering servo control input. The proposed trajectory planner was devised and implemented to control an industrial robot manipulator (Performer MK3s) so that a significant improvement of end-effector performance could be demonstrated. The same trajectory planner was rearranged into an autonomous module and incorporated with real-time control. This new implementation was proposed and implemented for supervisory controlled telerobotics applications. It was also applied for welfare robotics applications. Proposed trajectory planner is an off-line process, and it does not require hardware alterations. Thus, it could be conveniently implemented with existing robot manipulator systems.
item: Thesis-Abstract
An Urban environment analysis system based on an integrated land- use and transport model
Sathyaprasad IMS
During last several decades the world population continued to grow at an exponential rate, supported mainly by the improved health care facilities all over the world. But most of this growth was confined to relatively fewer number of urban centres. This trend was more obvious in the metropolitan areas of developing countries, where already high natural population increases were backed by increasing migration from rural areas. These intolerably high population growths, however, were not paralleled by the infrastructure provision, and the inevitable outcome was the numerous land-use, transport and environment related problems. The magnitude and the complexity of urban problems in metropolitan areas of developing countries reveal the extent to which these sectors of the metropolis are interrelated. The interrelationships between these sectors are so significant that the roots of the problems in one sector lie in the other sectors as well, and hence should be handled with an integrated approach. Unfortunately, the current institutional set up or the practice of urban planning does not facilitate policy formulation and implementation with such integrated approach. One of the pre-requisites for this much-needed co-ordinated institutional set up and policy planning and implementation practice is an analysis tool that covers all these sectors and the interrelationships among them. An analysis system for integrated policies of land-use, transport and the environment has the objective of providing such an analysis tool. This research focuses mainly on the development of an urban environment analysis system based on an integrated land-use and transport model. This study deals especially with developing metropolises, and those in the Southeast Asia in particular. The objectives of the study are; understanding the present situation and issues of the developing metropolitan areas; the theoretical development of an integrated land-use and transport model; the development of an estimation system of land-use and the environment; and development of a personal computer based analysis system for integrated policies of land-use, transport and the environment. In the beginning, investigation is made on the present situations of developing metropolises with regard to land-use, transport and the environment, in an attempt to understand the issues and their interrelationships, and to decide on the kind of integration between land-use, transport and the environment that best suits the urban areas under discussion. The ways of modelling interactions between land-use and transport are formed considering the dynamics of land-use change and trip characteristics. Land-use and transport interaction is represented in two ways in the contemporary urban models; interaction type where land-use and transport are represented hierarchically connected separate modules, and integrated type where land-use and transport are represented in an organically connected single model framework. The two kinds of integration are discussed and compared. Some urban environmental issues pertinent to the developing metropolises, which have some significance at finer spatial levels than the whole metropolis, are identified and discussed in detail. Most of these issues can be identified as externalities of land-use and transport. The environmental estimation is therefore based on the land-use and transport forecast from the integrated land use and transport model. The interaction between transport and the environment have been the subject of many researches and at present there are many good environment estimation models to forecast transport externalities. But little research has been conducted on the environmental impacts of land-use. Although the environmental impacts of transport are very important, impacts of land-use, such as solid waste and waste water problem, are not at all insignificant, especially in developing metropolises. In the development of the environment estimation system here, interactions between land-use and the environment are discussed. Because the environment estimation model is intended to be used together with an integrated land-use and transport model (which itself is based on an improved version of the RURBAN (Random Utility Rent-Bidding ANalysis) land-use model), it is considered to be necessary to use predicted land-use and transport conditions as inputs, and environment qualities that form explanatory variables for land-use forecast as some of the outputs. In the development of the estimation system of urban land-use and the environment, environmental impacts of land-use are classified into those depend on the change of land-cover and those depend on the intensity of land-use activities. Land cover dependent environmental impacts can be estimated if the land-cover change is known., whereas for other impacts the land-use activity intensity should be known. The basic assumption behind the land cover and emission estimation is that both the land cover and the emission rate of pollutants are related to the land price of the area, which is an output from the land-use model. Land price is used here to represent the intensity of urban activities taking place in a given zone. Out of the zone characteristics predicted by the land-use simulation model, land price represents the intensity of activities most. Since the environmental estimation system is developed to be used together with a land-use simulation model, land price is selected as an index of activity intensity. Land cover does not mean the land-use of an area but the 'spatial composition of land according to the land cover types, such as vegetation, water bodies or built-up areas, as defined in the remote-sensing information'. Whereas emission rates are defined as 'the amount of pollutant emission in a given time from a unit of locator group'. The relationships that relate land cover compositions and emission rates with the land price are developed empirically using base year data of sampled zones. The empirical relationships developed using sampled data are used to forecast the land cover compositions and emission rates of a zone with a known land price. Land cover and emission rates for the forecast year, are used together with land use activity data, derived from the locator composition, and other topographic data, in the environmental simulation model to estimate environmental indicators for different zones. An empirical study is carried out to investigate to what extent is valid the assumption that the emission rates, which represent the intensity of activities in a zone, are related to the land price. Ward-wise solid waste emission data during 1987 and 1990 in the city of Yokohama for residential land-use agree with the assumption. The emission rates and the land price are related with correlation coefficient (R2) of between 0.32 and 0.57. These low correlations are, however, found to be due to the high land prices in two of the wards, which actually have more relationship with the Tokyo metropolis than with Yokohama. The exclusion of these two wards increase the correlation coefficient to 0.95. However, it is found that the per capita pollutant emission relates better with the land price, than the pollutant emission per household, in the case of residential land-use. Example emission equations are derived to estimate solid waste generation from the residential land-use. Another empirical study is carried out to examine the relationship between the land cover composition and the land price. Aerial photographic information and land prices of 1990 in the City of Yokohama are used. Land blocks with varying land prices and belong to different land-uses are used in the analysis. Land cover types are identified visually from the aerial photographs. These land cover compositions correlate with the land price, with correlation coefficients (R2) varying between 0.5 and 0.8. An example set of share curves, which represent the relationships between land price and the composition of land covers, are developed using the data, for different land-use categories. A personal computer based analysis system for integrated policies of land-use, transport and the environment is developed based on the integrated land-use and transport model and the urban environment analysis system mentioned above. The latter part of the study discusses the development of this analysis system on MS-Windows 3.1 environment using Visual BASIC 3.0 as the user interface and FORTRAN language for simulation programs. A brief explanation about the basic features, the facilities available, and the kind of visual output presentation available in the system is also given.
item: Thesis-Abstract
The Development of a structure for the design of hazard audits
(2014-07-07) Dester, WS
Hazard auditing, which is a formal, systematic, critical examination of a situation or set of circumstances to identify hazards, is fundamental to hazard management. Auditing is facilitated by "an audit" that details activities, procedures, systems and artefacts, where hazards might be identified. This thesis describes the development of a structure, in the form of a hierarchy, that can be used in the design of hazard audits. An examination of systems such as manufacturing and process plants, for hazards, is usually undertaken by examining the subsystems, (i.e. activities, systems, and procedures). Existing audits therefore, tend to be specific, as for example, audits of unsafe acts, unsafe conditions, technical functioning of materials and machinery, management. This type of audit restricts the examination to a closed system within observable and well described physical and organisational boundaries. It is argued in this thesis that examinations for hazards should go beyond this closed system and also look for hazards within the larger systems of society and industry. An examination of hazards can be seen as a search for evidence of proneness to failure. The hierarchy developed in this research focuses on hazard auditing for a construction project. Construction, which is associated with the construction industry, is only one phase in a larger system, the project, which encompasses development, use, and withdrawal from use. It is argued that evidence of proneness to failure of a construction project may be found in these systems, (project and industry), in the larger system of a social environment, and in the subsystems that are part of a construction project. These hazards are described in terms cf concepts, and presented in the form of a hierarchy that indicates inter-dependencies between concepts. This hierarchy is a basic structure to be used in the design of hazard audits. The concepts incorporated into the hierarchy are discussed and described in terms of their potential to provide evidence of proneness to failure. Sections of hierarchy are built up and presented at appropriate positions in the thesis. It is proposed that this approach to hazard auditing will allow for flexibility in dealing with specific situations, yet provide for the identification of hazards that can exist and develop outside of those situations. It is suggested that such an approach should be regarded as a specialist activity of hazard management. Further, it is argued that the activity of hazard engineering should be recognized as a separate discipline within its own right.
item: Thesis-Abstract
A Framework for providing a lifelong social security system for the operational workforce in the construction Industry in Sri Lanka
Wijewickreme, SP; Ekanayaka, LL; Pathirage, CP; Egbu, C
Construction is a projectised industry. One of the important resource requirements for construction projects is the availability of an operational workforce for its physical production. Hence, the operational workforce is a critical deciding factor in the success and failure of construction projects. The construction sector in Sri Lanka is suffering from a shortage of a required operational workforce for its physical operations even though the unemployment rate in Sri Lanka is about 5.2%. Research has further highlighted that “work” and “pay” are only the surface factors, hiding underneath them (similar to an iceberg) are a multitude of different problems and the psychological needs of the workers. In addition to the shortage, there is a lack of an organised structure for human resources, which delivers time, cost and quality related behavioural constraints within the construction industry of Sri Lanka since circa the 1980’s. The aim of the research is to develop a sustainable framework for a lifelong social security system for the operational workforce of the construction industry in Sri Lanka without increasing the prevailing construction costs. The hypothesis is the minimising of resource wastages and behavioural impacts of current practices and the introduction a secured future life through a new system of lifelong social security [PR/SS] for the operational workforce. It is anticipated that the finances required for providing a social security system can be salvaged from the recovery values of material and time wastages and the demand and supply impacts generated as repercussions from the behavioural practices of the current operational workforce. The research instruments used for gathering primary and secondary data for evaluating the financial impacts of behavioural constraints were a questionnaire survey and audited financial statements. About 400 questionnaires (That were premeditated to calculate the monetary impacts of the social behaviors of the construction operatives via ‘degree of importance’ and ‘relative important index’) were distributed to higher management of contracting organisations in Sri Lanka. A further request was made to the contracting organisations to provide audited statements for the past five years. From the research, it was identified that the unavailability of a human resources structure is a major constraint for the construction industry in Sri Lanka. Salvaged finances that could derive from the removal of the transitional layers of risk multiplication and the removal of the behavioural constraints of the construction operatives are sufficient to finance a lifelong social security system for themselves. Based on the research findings, framework for the Building Forces of Sri Lanka [BFSL] was developed to overcome from the interim thinking pattern of the current construction operatives. In the current system, contracting organisations are not capable of providing the required training for the operatives. With the implementation of BFSL alongside the strong intervention from statutory organisations, a trained operational workforce can be developed to face any situation within the construction arena in Sri Lanka.
item: Thesis-Abstract
Hyperbolic paraboloid shell roofs
(2014-04-10) Mathai, AC
Of recent years,hyperbolic paraboloid doubly curved surface, has been used extensively in construction. It makes efficient ur.e of materials by relying on form or shape for strength rather than on mass. The simplicity of its structural action and its inherent beauty make it possible to achieve aesthetically pleasing structures of imposing proportions. One of the features of the hyperbolic paraboloid form, which appeals to the architect, is the many ways in which this warped surface can be combined to achieve completely dissimilar striking effects. The groined vault, the inverted umbrella and the saddle shape vault are all popular examples of the different appearances which can be achieved with basically the same
item:
Long waves on water of variable depth
(5/24/2011) Gunasekara, MM
This dissertation is mainly a review of some of the work done by various authors on the long wave (shallow water) approximation and its applications to different problems. Shallow water wave equations are derived which are identical with Stoker's equations but the method of derivation is slightly different. The method of characteristics is used in solving the differential equations governing the shallow water wave theory. The climbing and breaking of waves on sloping beaches is discussed. After the derivation of the transport equations for the discontinuities that can exist across a characteristic an equation is obtained for the time and hence the distance of breaking. A simple explanation of the formation of a bore in a sloping stream is given here. The climb of a bore on a beach of uniform and non-uniform slope is also discussed briefly because of its close resemblance to non-uniform shock propagation in gas dynamics. The notion of tsunami waves and the use of shallow water wave theory in the study of the numerical simulation of realistic tsunamis is also discussed briefly.
item: Thesis-Abstract
Molecular and ultrafine structure of cotton fibres
(5/24/2011) Fernando, LD
Differences among native cottons which have been recognized the textile industry for many years, and have formed the basis for Cotton classification in commerce and ultimate utilization, include Factors such as fiber length, fineness and spinnability. Recent, detailed investigations have established that, in addition, cotton types wary in their fundamental mechanical properties. The object of the present work has been to ascertain whether the variation in fiber properties are due to differences which exist at the ultrafine and molecular levels of the structure. Furthermore, with the advent of man-made fibers, modifications of the properties of natural fibers has become a compelling requirement, for their survival in the competitive world markets; and for this reason a detailed study of the structure of the cotton fiber has particular relevance. The ultrafine and molecular structure of several varieties of cottons have been examined by means of transmission electron micro-scope and X-ray and electron diffraction techniques. It has been possible to establish that there are no significant differences in: (i) the size of the particles (obtained after hydrolysis) whose dimensions may be taken to represent the combined crystalline and Para-crystalline regions, and (ii) the crystal structure (cellulose I), between different cotton types. X-ray studies have shown that differences in the orientation of the 'crystallites' I have an effect on the mechanical properties of the fiber. Thus, the evidence leads to the conclusion that variation in fiber properties are due to differences at higher (fibrillar) levels of structural organization. Electron diffraction results have conclusively shown the inadequacies of the widely accepted model for the fundamental structural unit of crystalline cellulose I (unit cell), proposed by Meyer and Misch on the basis of X-ray diffraction studies. A possible unit cell to fit the observed data, from electron (and X-ray) diffraction, has been postulated, even though a detailed elaboration of a unit cell for cellulose I was outside the scope of this work. The present study has laid the foundations for further |investigations into the structure of cotton fibres at the fibrillar level and a more rigorous study of the unit cell of native cellulose means of electron diffraction.
item: Thesis-Abstract
A systems approach to earthquake vulnerability assessment
(2014-07-07) Sanchez-Silva, M
The ability to take decisions about the expected response of existing projects (i.e. buildings, lifelines, cities) to an earthquake is difficult and complex. The behaviour of a few selected parameters of the main structural system (e.g. inter-storey drift) are commonly used to make judgements. The behaviour of a project clearly depends upon the structure but it also depends upon many other factors which often are not considered. These include, safety culture, management, condition, use, construction, materials and so forth. The modelling and measurement of these factors vary in quality since they are very different in nature. A model which enables these factors to be put together to assess the proneness to failure of a particular project is proposed. The model follows a systems approach and concentrates on the modelling and management of information. The management of the uncertainty, which is classified into fuzzincss, incompleteness and randomness, is an important part of the model. Hierarchically arranged holons describe the processes making up the project and capture inherent fuzziness of the problem. The model includes tests (such as audits) which a project must pass in order to be declared dependably safe. Dependability is a measure of the degree to which an engineering theory has been tested in practical problems. The proposed methodology combines existing numerical models as well as ways of processing vague information and expert judgement. It is also a very flexible tool which allows the handling of various types of projects and situations which are slightly different from past experience. Experts will use linguistic assessments to measure the evidence about the dependability of processes to sustain their function during an earthquake. Linguistic assessments are matched to interval probability numbers. An interval number is used to capture, in a practical manner, features of fuzziness and incompleteness. Interval probability theory is used to combine evidential support values throughout the hierarchy. A computer implementation of the model (i.e. EVAS) was developed to show its potential for practical use. The software developed was used to apply the methodology to the Hospital Regional de Buenaventura in Colombia. Further testing of the proposed model and EVAS in practical applications should be carried out to ensure their dependability.

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