This thesis concerns the exploitation of the site isolation concept in cascade sequences that facilitate rapid construction of complex polycyclic molecules. Site isolation is the anchoring of mutually destructive reagents onto solid supports to prevent their mutual deactivation.

This thesis discusses the implementation and performance of various conventional and artificial-intelligence-based control and estimation techniques for variable speed induction motor drives. The drive types considered are scalar drives, and high-performance vector and direct torque controlled drives. In the first part, various conventional control design techniques are developed and applied to conventionally controlled drives. The performance of these drives is compared to that of fuzzy logic controlled drives, for which a specific design method is developed using universal fuzzy logic controllers. The developed methods are studied using simulations and experimental results. Implementation issues are presented in detail. In the second part, the design and implementation of conventional and artificial-intelligence-based speed estimators for use in scalar, vector and direct torque controlled drives are discussed. The conventional estimators considered comprise both a mathematical-model-based speed estimator and a model-reference-adaptive-system-based speed estimator. The artificial-intelligence-based estimators considered use artificial neural networks which are trained on data collected in simulations. The performance of both types of estimator, in the entire operating range of the drive, is discussed extensively.

This thesis describes a systematic investigation into the sources of acoustic noise and vibration in switched reluctance machines, and encompasses the vibrational behaviour of the stator, the influence of control parameters, and an evaluation of the effectiveness of active vibration cancellation. The influence of leading design parameters, such as the width and number of poles and the yoke thickness, and geometric asymmetries, such as lamination notches in the stator core, and the effect of the stator windings, the frame, the end-caps and the mounting assembly, on the natural frequencies and modes of vibration are investigated, Chapter 3. Both two-dimensional and three-dimensional finite element analyses are employed, the predicted results being validated by measurements on various experimental models, which consequently highlights the limitation of the finite element technique for highly complex structures with discontinuities in their fabrication. The influence of the mass and stiffness of the laminated stator core and the stator windings on the natural frequencies and vibration modes is investigated, and effective material properties are deduced for the analyses. It is found that the number of poles and lamination notches on the stator influence the number of vibrational modes which occur in the audible frequency range due to the introduction of dual natural frequencies, viz. symmetrical and anti-symmetrical modes, which are shown to separate further in value as the asymmetries become more profound. As the diameter of the stator yoke is reduced the natural frequencies increase, whereas increasing the thickness of the yoke and the adding of a frame and end-caps significantly increase the natural frequencies. The effect of the stator poles is to significantly reduce the stator natural frequencies, which are irrespective to a variation to the width of the poles, a variation in their mass being annulled by the resulting change in stiffness. Similarly, it is shown that the winding mass and stiffness offset each other so that their influence is also relatively small, whereas, although quantification of the damping is not within the aims of this thesis, it is apparent that the windings introduce a high level of damping which consequently limits the magnitude of the vibrations and hence acoustic noise. Finally, the laminated nature of the core is quantified and is shown to affect the effective material properties compared to an equivalent solid core, and to increase the effective damping. Previous investigations have studied the influence of the drive control parameters, but generally limit the analysis to either the frequency or time domain or to measurements of the sound pressure level, and are generally carried out in isolation. Therefore. the influence of alternative operating modes and their associated control parameters on the acoustic noise and vibration of an SR machine is thoroughly investigated. the results being analysed in both the frequency and time domains, and compared with measurements of the sound pressure level, Chapter 4. The noise and vibration which results when the SR machine is operated under both voltage and current control. with both hard and soft chopping techniques, and various switching angles, and for various sampling and switching frequencies, is measured. The influence of speed and load is also investigated, and the vibration and noise are also investigated under single pulse mode operation. It is found that hard chopping results in a noisier operation than with soft chopping due to increased current ripple, especially under current control. The noise and vibration is clearly shown to differ under current control compared to voltage control and single pulse mode, due to the random switching of the phase voltages resulting in wideband harmonic spectra, thereby increasing the levels of all the mechanical resonances. Further, it is found that the noise and vibration increase with both speed and load. In general, the increases in noise and vibration are attributed to an increase in the rate of decay of current at phase turn-off, regardless of the control parameter under investigation. Finally, the effectiveness of active vibration cancellation for nOIse reduction is investigated under typical operating modes in Chapter 5, which, for the first time, is analysed in both the frequency and time domains, and validated by measurements of the sound pressure level. It is found that active vibration cancellation is less effective for machine stators which have more than one dominant vibration mode within the audible frequency range, since the technique is only capable of applying active cancellation for a single vibration mode, thus any further resonances remain unaffected. Further, during chopping control, especially current control which results in random switching, it has been shown, for the first time, that the effective time-delay varies to that applied, thus rendering the technique less effective. This is found to be attributed to the asynchronism of the final chopping edge and point of phase turn-off, therefore preventing the vibrations from being excited in anti-phase, as explained in section 5.6.

In this thesis, a novel disc-type ultrasonic motor stator is investigated. The stator has an asymmetrical structure (120°-90°-150° support boundary configuration) on its surface. The advantages of this structure include a single electrical phase driving, multiple-resonant-modes driving, rotational direction changes by modulation of driving frequencies, single contact point, and simple driving electrical circuit. With the setup of a precision laser vibrometer measurement experiment, mode motions and wave propagations of the UM are analyzed. The model is further verified by using finite element simulations where a 3-dimensional mechanical element with an extra electrical degree of freedom is used and then electrical impedance response, phase response and mechanical frequency response of the UM are studied. Furthermore, a transfer function model and equivalent circuit model of the Um in terms of radial and tangential displacement components are established for control objectives and for certification of dynamic characteristic parameters. The equivalent circuit model verifies radial, tangential and couple vibration modes once more and is used in search of resonance frequencies. The PSPICE has been used to simulate the equivalent circuit components. Finally, a speed control scheme is implemented by using current modulation and commercial DSP technique, in order to keep the revolution speed constant. The proposed ultrasonic motor system has proven good dynamic behaviours with the driving frequency range of 65k-100kHz and reaches a maximum revolution speed of 600rpm.

No description available.

This research aimed at investigating the relationship between three phase induction motors vibration (MVS) and current signatures (MCS). This is essential due to the cost of vibration measuring equipment and in cases where vibration of interest point is not accessible; such as electrical submersible pumps (ESP) used in oil industry. A mathematical model was developed to understand the effects of two types of induction motors common faults; rotor bar imperfections and phase imbalance on the motor vibration and current signatures. An automated test facility was developed in which 1.1 kW three phase motor could be tested under varying shaft rotation speeds and loads for validating the developed model. Time and frequency domains statistical parameters of the measured signals were calculated for fault detection and assessing its severity. The measured signals were also processed using the short time Fourier transform (STFT), the Wigner-Ville distribution (WVD), the continuous wavelet transform (CWT) and discrete wavelet transform (DWT) and wavelet multi-resolution analysis (MRA). The non-stationary components, representing faults within induction motor measured vibration and current signals, were successfully detected using wavelet decomposition technique. An effective alternative to direct vibration measurement scheme, based on radial basis function networks, was developed to the reconstruction of motor vibration using measurements of one phase of the motor current. It was found that this method captured the features of induction motor faults with reasonable degrees of accuracy. Another method was also developed for the early detection and diagnosis of faults using an enhanced power factor method. Experimental results confirmed that the power factor can be used successfully for induction motor fault diagnosis and is also promising in assessing fault severity. The suggested two methods offer inexpensive, reliable and non-intrusive condition monitoring tools that suits real-time applications. Directions for further work were also outlined.

No description available.

The purpose of this thesis is twofold: to examine the validity of the rotating-field and cross-field theories of the single-phase induction motor when applied to a cage rotor machine; and to examine the extent to which skin effect is likely to modify the characteristics of a cage rotor machine. A mathematical analysis is presented for a single-phase induction motor in which the rotor parameters are modified by skin effect. Although this is based on the usual type of ideal machine, a new form of model rotor allows approximations for skin effect phenomena to be included as an integral part of the analysis. Performance equations appropriate to the rotating-field and cross-field theories are deduced, and the corresponding explanations for the steady-state mode of operation are critically examined. The evaluation of the winding currents and developed torque is simplified by the introduction of new dimensionless factors which are functions of the resistance/reactance ratios of the rotor and the speed. Tables of the factors are included for selected numerical values of the parameter ratios, and these are used to deduce typical operating characteristics for both cage and wound rotor machines. It is shown that a qualitative explanation of the mode of operation of a cage rotor machine is obtained from either theory; but the operating characteristics must be deduced from the performance equations of the rotating-field theory, because of the restrictions on the values of the rotor parameters imposed by skin effect.

No description available.

This thesis introduces and researches the concept of a new form of switched reluctance motor, in which the rotor is made from a series of discrete segments. Single phase machines are initially examined and design rules established. Predictions of air-gap force density are compared with toothed rotor equivalents and it is shown that much greater force densities are theoretically possible with the segmental design. The thesis then proceeds to apply the concepts developed to two different three phase configurations, which show particular advantages. Two demonstrator machines are designed and built, and their method of construction described. Measured static test results are initially presented for each machine and compared with a conventional switched reluctance motor of the same dimensions, revealing both the advantages and disadvantages of the two segmental rotor configurations. Both demonstrator machines are then run as SRM drives, with the current to each phase supplied from an asymmetric half bridge converter. The current and voltage waveforms are monitored, along with measurements of mean torque output. Waveforms are compared with those predicted by simulations and conclusions are drawn regarding the performance of the drive systems. The results of this work clearly demonstrate that segmental rotor SRMs have much greater torque capability than conventional toothed geometries. Of the two demonstrator machines constructed, one has a very high torque per unit loading, but has relatively long end-windings; the other has slightly reduced torque per unit loading but overcomes the problem of long end-windings. Both machines appear to outperform other forms of reluctance motor.