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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The computation of eigenvalues and eigenvectors of very large sparse matrices

Paige, Christopher Conway January 1971 (has links)
Several methods are avi1iible for computing elgenvalues and eigenveotors of large sparse matrices, but as yet no outstandingly good algorithm is generally known. For the synimetric matrix case one of the most elegant algorithms thetiretically is the method of m1rini1zed iterations developed by Lanczos in 1950 • This method reduces the origi1 matrix to tn-diagonal form from which the eigenaystem can easily be found. The method can be used iteratively, and here the convergence properties and different possible eigenvalue intervals are first considered assiinrtng infinite precision computation. Next rounding error pn1 yses are given for the method both with and without re-orthogonalization. It is shown that the method has been unjustly neglected, in fact a particular computational algorithm for the method without re-orthogoiiRl I zation is shown to have remarkably good error properties. As well as this the algorithm is very fast aM can be pronamined to require very little store compared with other comparable methods, and this suggests that this variant of the Lanczos process is likely to become an extremely useful algorithm for finding several extreme eigenvalues, and their eigenvectors if needed, of very large sparse symmetric matrices.
2

Robust Control for Multi-Axis Test Rigs

Gizatullin, A. O. January 2008 (has links)
Structural test rigs may incorporate between 1 and 30 hydraulic actuators each providing a load or displacement control. A closed loop PID controller is most commonly used to provide displacement or load control. Normally, industrial controllers provide a relatively high operational bandwidth of the actuator and a good performance within its operational range. The problem arises when the load is changing over a considerable range and sometimes in an unexpected manner. This causes undesirable interaction between actuators and results in degradation of the reference signal tracking. The controller proposed in this thesis is designed to meet aforementioned challenges facing the control system for modern multi-axis rigs: to reach satisfactory reference signal tracking without the need for iteration and robust performance in the presence of interactions and disturbances. The controller is a novel extension of the Model Reference Adaptive Control method known as Minimal Control Synthesis (MCS). It is arranged to function seamlessly through integration with a conventional test rig controller. Furthermore the controller employs important features which allow model following behaviour of the hydraulic cylinder and, to a large extent, to compensate for the actuator dynamics by the inverse model extension. A theoretical tool has been proposed for the analysis of the adaptation dynamics of the controller. A multi-axis scheme for the controller utilises a decentralised approach which implies individual control of each cylinder of the multi-axis system with coupling effects treated as disturbances, which should be attenuated by the adaptive controller. Experimental studies for single-axis and multi-axis variants of the control scheme were conducted on a six-axis MAST. Very good dynamic performance was demonstrated relative to a standard industrial controller. However, it was found that the bandwidth and disturbance attenuation property of the controller were compromised to some degree because it was not feasible to include acceleration feedback signal in the controller structure.
3

Developing manufacturing control applications with microcontroller based internet connectivity

Bashir, Anwar January 2006 (has links)
This thesis describes work on the development of a `plug and play' communications system for ethernet designed to enable devices to automatically provide data logging and control services over a network. Examination of the current work in protocol design such as Common Object Request Broker Architecture (CORBA) suggests that there is scope for research in developing a simpler design. This view is supported by examining the factors that have led to the widespread adoption of the Internet and its protocols. The approach is to develop a protocol that is open systems based. The protocol will allow multiple applications to be served; one of these applications will be to enable numerical controllers to download programs over the Internet. The research carried out here involves developing a standard `plug and play' communications protocol for ethernet based on TCP/IP. A pre-requisite for developing such a `standard' protocol is that of universal interfacing. In view of the fact that devices do not share common interfaces a universal electronic connector box has been developed. The purpose is to provide connectivity to a wide range of devices. The development of the electronic box involved building successively complex prototypes. The prototypes are designed to control and transfer information to and from equipment such as printers, photocopiers, electronic door access and numerical controllers. By building such a diverse range of `real world' applications it is possible to show how a single technology can control dissimilar devices. The development of the technology has the potential to enable SME's to replace complex personal computer based control systems with simple Internet enabled `plug and play' controllers. By sharing common functions and data services the technology also creates new opportunities for SME's to develop supply chain management and enterprise resource planning systems. The results of the research have led to the design and implementation of photocopier and printer control management systems, as a test of the validity of the protocol and prototypes that have been developed. The printer and photocopier control management systems are now in daily use by staff at the University of Teesside. The numerical machine control system has attracted government funding for further development.
4

Development of integrated methods for control of Networked Control Systems

Recalde Camacho, Luis Felipe January 2010 (has links)
No description available.
5

Low pressure pneumatic servomechanisms

Chitty, A. January 1973 (has links)
Tests on a continuous action low pressure electro-pneumatic linear motion servomechanism are described. Data from individual tests on the components of this system, including the servo valve and the actuator, is used for analogue computer simulations. The simulations are shown to model the experimental system over a wide range of conditions. A simple linear equation is shown to model many aspects of the behaviour of the system. This equation is presented in a form which enables the importance of many system parameters to be easily assessed. An all pneumatic linear-motion servo using discrete fluidic components is described. This system uses pulse-width modulated signals to control on/off valves. Tests on components of the system, including beam deflection proportional amplifiers, Schmitt triggers, valves and a fluidic displacement sensor and also on the complete servo are described. Shortcomings in currently available components are shown to limit the performance of both systems, and modifications necessary to improve their closed loop behaviour are proposed.
6

Integrated real-virtuality system and environments for advanced control system developers and machines builders

Hussein, Mohamed January 2008 (has links)
The pace of technological change is increasing and sophisticated customer driven markets are forcing rapid machine evolution, increasing complexity and quality, and faster response. To survive and thrive in these markets, machine builders/suppliers require absolute customer and market orientation, focusing on rapid provision of solutions rather than products. Their production systems will need to accommodate unpredictable changes while maintaining financial and operational efficiency with short lead and delivery times. Real-Virtuality (R-V) systems are an innovative environment to address these requirements by facilitating enhanced support in machine system design utilising integrated real-virtual environments centred on concurrent machine system development and realization. This environment supports not only machine system design but also the development of the control system at the same time. Utilising the Real-Virtual Mapping Environment (RVME), 3-D simulation machine models can perform actual machine operations in real-time when coupled with the real machine controller. This provides a more understandable, reliable and transparent machine function and performance. The research study explores different types of controller verification methods and proposes a new method which employs the use of a control signal emulator. The research study has fomulated a novel technique for emulating quadrature encoder signals to provide virtual closed loop control of servomotors. The deployment of a control signal emulator technique makes the system unique and removes its dependency on specific hardware. Enabling the real-time data from the signal emulation environment eases the task of realising a real-time machine simulator. To evaluate the proposed architecture, three case studies were performed. The results have shown that it is possible to create verified and validated machine control programs with no modification needed when applied to the real machine. The migration from the virtual to the real world is totally seamless. The result from the study show that the virtual machine is able to operate and respond as a real machine in real-time. This opens up the unexplored potential of integrated 3-D virtual technology. The real-time 3-D simulation virtual machine will enable commissioning and training to be conducted at an earlier stage in the design process (without having to wait for the real machine to be built). Furthermore, various test scenarios can also be developed and tested on the system which helps to provide a better lofriderstanding of the machine behaviours and responses. This research study has made an original contribution in the field of machine system development. It has contributed a novel approach of using emulated control signals to provide machine control programmers with a platform to test their application programs at machine level which involves both discrete digital signals and continuous signals. The real-time virtual environment extends the application domain for the use of simulation. The architecture proposed is generic; to be exact it is not constrained to a specific industrial control system or to a specific simulation vendor.
7

The design of a control system for the mitigation of vibration in variable speed screw compressor systems

Milligan, William James January 2011 (has links)
No description available.
8

Enhanced Bees Algorithm with fuzzy logic and Kalman filtering

Darwish, Ahmed Haj January 2009 (has links)
The Bees Algorithm is a new population-based optimisation procedure which employs a combination of global exploratory and local exploitatory search. This thesis introduces an enhanced version of the Bees Algorithm which implements a fuzzy logic system for greedy selection of local search sites. The proposed fuzzy greedy selection system reduces the number of parameters needed to run the Bees Algorithm. The proposed algorithm has been applied to a number of benchmark function optimisation problems to demonstrate its robustness and self-organising ability. The Bees Algorithm in both its basic and enhanced forms has been used to optimise the parameters of a fuzzy logic controller. The purpose of the controller is to stabilise and balance an under-actuated two-link acrobatic robot (ACROBOT) in the upright position. Kalman filtering, as a fast convergence gradient-based optimisation method, is introduced as an alternative to random neighbourhood search to guide worker bees speedily towards the optima of local search sites. The proposed method has been used to tune membership functions for a fuzzy logic system. Finally, the fuzzy greedy selection system is enhanced by using multiple independent criteria to select local search sites. The enhanced fuzzy selection system has again been used with Kalman filtering to speed up the Bees Algorithm. The resulting algorithm has been applied to train a Radial Basis Function (RBF) neural network for wood defect identification. The results obtained show that the changes made to the Bees Algorithm in this research have significantly improved its performance. This is because these enhancements maintain the robust global search attribute of the Bees Algorithm and improve its local search procedure.
9

Microcontroller-based transient signal analysis and distributed system for intelligent process monitoring

Alyami, Mohammad Manea January 2008 (has links)
The research presented in this thesis considers the feasibility of utilising dsPICs (digital signal controllers) in the development of effective monitoring systems which have the capability to adapt to changes in operating conditions and can be quickly calibrated to suit a range of applications, thus helping to reduce the development time constraint. The capability of these monitoring solutions to detect and isolate faults occurring in pneumatic processes is investigated and their effectiveness verified. Three applications are considered gas pipe leakage, linear actuator operations and gripper action. In each case, solutions are developed based upon the dsPIC. The solutions utilise the analysis of pressure transients to overcome the limitation in the dsPIC memory. The deployment of minimal sensors and electronics was essential to optimise the cost of the system. Leak detection techniques are developed with application to gas fitting pipes. The speed at which correct decisions are determined was the essence of this work. The solutions are tested, compared and their capability validated using pipes which had been rejected according to industrial standards. In this application a dsPIC digital signal controller and a pressure sensor were deployed, thus ensuring a low cost monitoring solution. Linear actuator "end of stroke" monitoring has, previously, largely been possible using limit switches. A more challenging method based upon the deployment of a pressure sensor is outlined. Monitoring model surfaces were obtained and their capability to determine the health of the process was proved, at various supply pressures. With regard to the gripper monitoring, a performance surface by which the gripper action can be monitored is generated and embedded within the dsPIC. Various faults are simulated and their effect on the gripper performance investigated. Leakage and blockage are also investigated at various places in the pneumatic circuit to allow for an algorithm to be devised. Faults may be detected and isolated, and their locations identified to allow for timely recovery treatment, thus supporting an enhanced process monitoring strategy.
10

Differences between machine and human testing of shock absorbing systems

Alcantara Alcover, Enrique January 2000 (has links)
This thesis documents a study on the sources of the differences found between results from machine and walking testing of shock absorbing systems. A complex programme of experiments was conducted at the Institute of Biomechanics of Valencia to explore the four most outstanding statements proposed with this respect: 1. - No accurate simulation of impacts by machine test. This was investigated by comparing results from testing materials simulating impact forces with results from walking tests. 2. - In use materials degrade and their properties change and existing machine testing methods could not replicate material properties during walking. A new testing method was developed to measure the recovery ability of materials by simulating plantar pressures and results compared with walking tests. 3. - Shoe effect on walking kinematics and heel pad confinement has greater influence on shock absorption than material properties. An instrumented pendulum was developed to study the heel pad. Insole materials were evaluated in walking tests, in pendulum tests and in different machine testing including the new method developed simulating plantar pressures and the results compared. 4. - Accommodation to impact conditions occurs according to a controlled proprioceptive feedback model. Accommodation, impact perception, comfort, walking and passive biomechanical variables and material properties were studied in relation to system's input, output and goal. Accurate simulation of impacts improved the ability of machine test to predict the walking performance of materials, but not upper body shock transmission. Properties of materials such as recovery ability, stiffness and hardness play an important role in concepts and passive interaction but mainly by influencing accommodation. Accommodation was identified as the source of differences of results between machine and walking tests of shock absorbing materials. The human body was described as comprising two independent mechanical systems: One system, governed by the elasticity and hardness of materials, it is defined by impact forces and accelerations that are inversely related to upper body transmission and control the perceived impact through foot position and knee bend. The other system is defined by heel pad stiffness, insole properties at initial loading and passive interaction that regulate upper body shock transmission by ankle inversion for comfort control. Passive interaction is defined in this thesis as the mechanical coupling between insole and heel pad that determines the properties of the system either through heel pad confinement or compression. Machine tests appear to predict results with respect to the first system but not the second, which required passive human testing. For insole use, high-energy absorption materials are preferred. These are capable of increasing elastic deformation to reduce impact forces and accelerations without increasing initial-maximal stiffness by passive interaction thus avoiding any increase of head transmission due to accommodation. Heel pad properties were described by three mechanical components accounting for 93.08% of total variance: These are an elastic component, a viscoelastic component and a component related to elastic deformation at low stiffness. Differences were found between shod and barefoot test results. With barefoot there was an initial low stiffness (18-50 kNm*1) response that was not evident in the shod tests which showed elastic deformation related to final stiffness. With barefoot, the elastic component accounted for impact forces variance (> 70%) and initial deformation component for peak force time (> 60%), while shod impact forces were related mainly to the elastic deformation component (> 60%) whereas rate of loading and acceleration were related to the initial-maximal stiffness component (>20%). Differences in heel pad mechanics due to age, gender and obesity were observed. Although the heel pad properties degraded with age, losses appeared to be compensated by obesity.

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