No description available.

No description available.

The initial results of an investigation into the flow properties of a gaseous suspension of fine particles are reported. The objective of the work has been the acquisition of extensive experimental data, the analysis of which provides a better understanding of the pressure drop and flow characteristics of pneumatically transported solid particles. The versatility of the test rig is demonstrated by the diversity of the investigations performed during this study. Quantitative results were acquired for the flow of different-sized alumina particles flowing through vertical and horizontal pipes of different diameters, and around six bends of varying geometry. Dimensional analysis is profitably applied to the correlation of the experimental. data and the ensuing deductions examined critically. These conclusions were either substantiated or refuted by a visual appreciation of the nature of the flowing suspension. Investigations into bend erosion have explained the mechanism of the erosion process, and the data analysis has produced an equation which defines the mean wear rate as a function of the mean air velocity and the solids-to-air mixture ratio. This study has revealed the need for extensive study of topics not yet fully examined. Suggestions for further work are included at the end of Chapters 5, 6, 7 and 8.

No description available.

No description available.

This thesis presents a novel design methodology for the synthesis of hybrid mechanisms using Genetic Algorithms. GAs are a search and optimisation method which model the mechanics of population genetics to give a truly global search method. In parallel to the development of a suitable GA, the work also develops novel objective function criteria which go some way to providing an approximation to dynamic criteria whilst using only kinematic properties during calculations. This has considerable effect in reducing the time required to find a feasible solution. The thesis presents a set of results which validate the proposed methodology, both in terms of speed of convergence and quality of the final solutions obtained. The application chosen is the synthesis of a hybrid five bar path generating mechanism. A description is given of the development of a practical machine for a given test case, so as to illustrate that the solutions produced are feasible in terms of real world implementation. Results are presented which show the effectiveness of the machine. Finally, a critical analysis of both the methodology and the results is carried out. This highlights some areas in which the methodology could be improved by future work.

This thesis describes a new technique, absolute distance contouring, and a phase unwrapping algorithm for phase maps with discontinuities. Absolute distance contouring, which is based on the shadow moire method, using the rotation of a grating, is a technique which can be used for the measurement of absolute distance from the grating to the object and the determination of an object's height. By the selection of suitable rotation angles, images are captured at different positions of the grating to obtain the required data. The technique is divided into three different methods, according to the number of images required for each measurement and the rotation angles. These are known as: the absolute distance contouring method, the four-image method, and the three-image method. Using these methods, the three-dimensional shape of the object can be obtained directly and it is not necessary to determine the absolute moire fringe order nor to judge the hills and valleys of the object's surface. Some of the problems of the previous shadow moire methods can be solved and some inconvenience can be overcome by the proposed methods. The techniques have been verified by experimental work which was carried out on a specially designed system. The results show that the methods are fast and the accuracy is better than 10μm. The maximum measurable range is related to the geometry of the optical system and the rotation angles. The phase unwrapping algorithm is a technique to obtain the correct phase distribution for a phase map with discontinuities. A crossed grating, which has two sets of lines in two different directions, is projected onto the surface to be measured. The modulated grating image, which is equal to the superposition of two separate modulated images, is captured and Fourier transformed. The two images are separated in the Fourier domain. After filtering and frequency shifting, they are inverse transformed to obtain two phase maps with different precisions. Phase unwrapping at each pixel is carried out independently and the correct phase values can be obtained in the presence of discontinuities caused by a surface with steps or noise. This fast algorithm has been verified experimentally by measuring the shapes of objects with height steps, and it only requires a single image for each measurement. The methods of absolute distance contouring and the new phase unwrapping algorithm are new techniques for the measurement of three-dimensional object profile, which will find application in many areas.

No description available.

There are many applications, such as paper mills, locomotive traction and machine tools, which require high performance control of more than one electric motor. These multi-motor drives are generally available in two configurations. The first one consists of a number of three-phase voltage source inverters (VSI) connected in parallel to a common DC link, each inverter feeding a three-phase AC motor. This configuration allows independent control of all machines by means of their own three-phase VSIs. The second method comprises one inverter, which feeds multiple parallel-connected three-phase motors. However, this configuration does not allow independent control of each motor and is suitable only for traction. This thesis explores a novel concept for multi-motor drive systems, based on utilization of multi-phase machines and VSIs, and series connection of all the machines in the group. Application of a single multi-phase VSI in conjunction with multi-phase machines generates additional degrees of freedom. The research presented here utilises these additional degrees of freedom to control a number of machines independently within a novel multi-phase multi-machine drive. The concept is based on the fact that independent flux and torque control of any AC machine, regardless of the number of stator phases requires control of only two stator current components. This leaves the remaining current components free to control other machines within the group. It is shown that it is possible to connect the machines in such a way that what one machine sees as the flux/torque producing components the other machines see as non-flux/torque producing components, and vice versa. Therefore it is possible to connect in series a number of multi-phase machines and independently control each machine while supplying them from a single multi-phase inverter. Different configurations of the multi-motor drive are possible depending on certain properties of the supply phase number. In general, higher the supply phase number is, higher the number of connectable machines is. However, some phase numbers are more favourable than others, as discussed in detail in the thesis. Simulation studies are provided for five, six, seven, nine, ten and fifteen phase configurations in order to verify the concept. It is shown that the concept is independent of the type of AC machines used and the only requirement is that they all have sinusoidal distributed magnetomotive force. Current control in both the stationary and rotating reference frames is considered and it is concluded that current control in the rotating reference frame requires compensation of the additional voltage drops caused by the series connection. Two possible methods of compensating for these voltage drops are suggested and verified by simulation. Finally, a laboratory rig is described, which utilises two three-phase inverters connected in such a way as to form a single six-phase inverter. A six-phase two-motor drive comprising a symmetrical six-phase induction machine and a three-phase induction machine or a three-phaseP MSM is investigatede xperimentally. An analysis of the performance of the two-motor drive is presented and it is shown that decoupled control of each machine is achieved.

The purpose of this study was to apply vibrations to the workpiece during surface grinding in order to improve the performance of the process. In addition to this, further necessary parameters were examined and analysed. A first step was to design the vibrating rig and after a number of different designs the most suitable model was selected for the conduction of the preliminary studies. However, a novel-improved system was designed and manufactured in order to undertake the full volume of experimental work. A number of simulations including stress and modal analysis were carried out and all the static and dynamic characteristics of the rigs were identified. Moreover, the exact dynamic behaviour of the rigs - including their natural frequencies - was established though real experiments. Sweep - sine and impact tests were employed in order to identify these dynamic parameters and the results were compared to those of simulation with the intention to detect the amount of error between these techniques. The rigs were vibrated at their resonant frequencies in order to achieve high values of amplitude with low voltage input. The static and dynamic characteristics of the grinding machine tool were identified. Similar methods such as sweep-sine test were employed in order to find the natural frequency of the machine tool's spindle unit. Static and dynamic stiffness of the machine tool's spindle unit as well as its compliance were identified. The preliminary studies showed an improvement in surface quality of the workpiece as well as a small reduction in cutting forces. This reduction was getting bigger with the increase of depth of cut. The main body of experimental work followed and showed that for 25 urn depths of cut, the vibration-assisted method could decrease up to 22.5 % the tangential forces. Furthermore, the effect of vibration was getting more noticeable at higher wheelspeeds and workspeeds. At those speeds the reduction in workpiece surface roughness reached 12.6%. Moreover, it was found that the application of vibration increased the material removal rate, reduced the cutting forces, increased the G-ratio and produced lower values of wheel wear compared to conventional grinding. Finally, an innovative closed-loop vibration control system was used for the process which could control the amplitude and the frequency of vibration in the actual grinding cycle. This I A Abstract system managed to control the applied values of vibration amplitude at resonant or near resonant frequencies. It was found that for higher depths of cut the closed-loop vibration control reduced the normal forces by 19% compared to open-loop control and 21 % compared to conventional grinding. Furthermore, the closed-loop control system performed better in terms of workpiece surface quality when grinding mild steel compared to conventional grinding and open-loop vibration control.