There is increasing demand for simple motor drives offering high reliability and fault tolerance in applications such as the aerospace actuator industry, with the development of `more electric aircraft'. This thesis presents a motor drive employing a switched reluctance motor, the novel single sided matrix converter, and a novel double band hysteresis based control scheme for control of the converter, implemented using a field programmable gate array (FPGA). The single sided matrix converter is a direct energy converter, capable of supplying unidirectional currents from a multiphase AC voltage source. It is suitable for driving motors such as the switched reluctance motor and trapezoidal permanent magnet direct current (PMDC) machine. The use of a direct energy converter removes the DC link energy storage element usually found in switched reluctance motor drives, making practical implementation possible without the use of electrolytic capacitors. This is a requirement for applications in the aerospace industry. Controller implementation without the use of a digital signal processor (DSP) makes application of the converter in the aerospace industry easy as specific DSP approval is not required. Simulations of the converter operation are presented, followed by a description of the practical implementation of the novel converter and control schemes. Practical results demonstrate the reliable operation of the converter, driving both switched reluctance and trapezoidal PMDC machines. The work has been published in three conference papers, presenting both the topology of the drive and the applied control schemes, as well as analysing the fault tolerant capabilities of the drive.

This thesis is concerned with the experimental investigation of robust speed control strategies for the industrial motor drive systems. The first objective of the thesis is to implement a high performance programmable dynamometer which can provide desired linear and non-linear mechanical loads for the experimental validation of the robust control methods. The discrete time implementation of the conventional dynamometer control strategy (the inverse model approach) is analysed and it is shown that this method suffers from the stability and noise problems. A new dynamometer control strategy, based on speed tracking and torque feedforward compensation, is developed and successfully implemented in the experimental system. The emulation is placed in a closed loop speed control system and the experimental results are compared with the corresponding ideal simulated results for the validation of the dynamometer control strategy. The comparisons show excellent agreement for a variety of linear and nonlinear mechanical load models and such a high performance experimental load emulation results are reported for the first time in research literature. The second objective of the project is to investigate the Fuzzy Logic Control (FLC) and the Sliding Mode Control (SMC) approaches in order to develop a simple,• algorithmic and practical robust control design procedure for industrial speed drive control systems. The Reaching Law Control (RLC) method, which is an approach to SMC design, and the FLC are used together in order to develop a practical robust speed control strategy. The robustness of the proposed control approach is tested for a variety of linear and non-linear mechanical loads provided by the dynamometer. Using the new robust control method, good output responses are obtained for large parameter variations and external disturbances.

The transmission-line modelling (TLM) method is applied to 3-dimensional problems in electromagnetic compatibility (EMC). The method is found to be a versatile tool which is ideally suited to the modelling of many EMC systems. A new way of deriving the scattering properties of the TLM node is presented and the derivation of mesh parameters, the application of boundary conditions and methods of applying excitation and of taking outputs are described. Issues regarding the efficient implementation of the TLM algorithm and a way of running very large simulations are reported. A multigrid method is introduced which allows meshes of different resolutions to be connected together to form a complete system. The method is used to apply fine resolution only in areas where it is required and to move numerical boundaries away from the region of interest. Comparisons are made with the more traditional graded mesh technique, using the hybrid node. Results are presented for a number of different systems with particular emphasis on the environment in which radiated emission tests are undertaken, although more general systems are also considered. The consequences of making measurements in an unlined screened room are discussed and ways of damping resonances are investigated. Wire, slot and spherical dipole antennas are modelled. Field-to-wire coupling, the TEM cell, a simplified device under test, the shielding properties of a vehicle body and the current induced by a simplified table-top device are also considered. Techniques are developed to obtain the Q factor of a screened room loaded with radiation absorbing material (RAM) and to obtain the radiation resistance of an antenna in free-space and also in close proximity to conducting surfaces.

Over the past decades, there have been a number of trends that have driven the desire to improve the ability to navigate in all environments. While the Global Positioning System has been the driving factor behind most of these trends, there are limitations to this system that have become more evident over time as the world has increasingly come to rely on navigation. These limitations are mostly due to the low transmission power of the satellites, where navigation signals broadcast from space are comparatively weak, especially by the time they have travelled to receivers on the ground. This makes the signals particularly vulnerable to fading in difficult environments such as "urban jungles" and other built up areas. The low signal-to-noise ratio (SNR) also means, that the signals are susceptible to jamming, both hostile and accidental. This motivates the need for alternatives technologies to satellite navigation and consider terrestrial based alternatives such as LORAN-C and eLORAN, but there is also significant interest in the exploitation of other non-navigation signals for positioning and navigation purposes. These so-called 'Signals of Opportunity' do not generally require any alterations to existing communications transmission infrastructure and utilise alternative multi-carrier modulation techniques to those used by navigation systems. This project examines the use of such a signal, the Digital Audio Broadcast (DAB) signal, as a positioning source. This thesis contains complete research from initial coverage simulations in the UK, through to extensive static testing, and the use of the signal in a dynamic environment and it has been shown that the Digital Audio Broadcast signal has potential as a terrestrial based positioning signal.

For aerospace related electric systems, torque/force density, reliability and fault tolerance are of the utmost importance. A method by which high figures of reliability can be achieved is by eliminating any mechanical gearing or interconnection elements between the electrical machine and its mechanical load. This means that direct drive, electrical machines must be employed. However, to implement such solutions (without any mechanical advantages), electrical machines with excellent torque density (for rotational machines) and force density (for linear machines) performances are required. In this work, the main aim is to propose and investigate possible methods for extending and improving the torque/force density capabilities of high performance, state of the art, electrical machines (both rotational and linear). This is done in order to be able to meet the performance requirements while lacking the mechanical advantages synonymous with gearing and/or mechanical interconnections. Novel electro-magnetic and thermal management structures, detailed design and optimisation procedures for electrical machines are presented in this thesis. As vehicles to investigate these novel concepts, a tubular linear, permanent magnet motor and a rotational, synchronous permanent magnet motor are designed, built and experimentally tested. These machines which are both for aerospace related applications serve to show and validate the worthiness of the proposed, performance enhancement measures.

Matter can be identified by its interaction with electromagnetic fields. This can be described by its dielectric and magnetic properties, which typically vary with respect to frequency in the microwave region. Microwave-frequency spectroscopy is capable of making non-contact, non-destructive, non-invasive and label-free measurements with respect to time. It can be used to characterise all states of matter and combinations thereof, such as colloids and microparticulate suspensions. Sensors based upon this technology therefore have great potential for (bio)chemical and industrial point-of-sampling applications where existing measurement techniques are insufficiently portable, low-cost or sensitive. Microfluidics is the manipulation of fluids within microscale geometries. This gives rise to phenomena not observed at the macroscale that can be exploited to achieve enhanced control of fluid flow. This means that microfluidic techniques can be used to perform complex chemistry in a completely sealed environment with minimal reagent consumption. Hence, microfluidics offers an ideal sample interfacing method for a microwave-frequency sensor. This work is concerned with developing novel, low-cost and highly sensitive probes that be easily integrated into a microfluidic device for performing on-chip sample preparation and diagnostics for generic (bio)chemical and industrial point-of-sampling applications. To this end, several novel microwave resonant structures were designed, optimised and integrated into microfluidic devices in order to characterise a variety of liquid-phase samples.

Permanent Magnet brushless DC motors are now competing with many other types of motors in the world industries application. However, for low and medium power applications, brushless DC motors are often the main option due to its recognized advantage such as having no commutator, more efficient, need less maintenance, smaller in size and can operate at higher speeds than conventional motors. The overall objective of this project is to produce an improved prototype BLDC motor with concentrated winding concept for an aircraft actuator application. Specifically, the aim is to extract the maximum power density and torque per kilograms by utilizing high switching frequencies, high pole numbers and minimizing magnetic material content. In this work, the research has focused on developing a procedure to design the BLDC motor by selecting several parameters and analysing their effects on the overall performance. Therefore, this research involved software and hardware methods which are broken down into field and circuit modeling, calculation of basic dimensions, magnetic circuit calculations, stator slot design, winding design, performance and loss calculation and lastly prototyping. Magnet software for finite element method (FEM) analysis and analysis programs based on standard software are used to optimize the overall performances. The proposed methods are verified by actual experimental result on the developed prototype. The performance of the prototyped machine is evaluated by using a high speed 150kw, 20,000 rpm test rig and data capturing equipment.

Transformer noise is of increasing environmental concern so continued efforts are being made by electrical steel and transformer producers to satisfy users by reducing the noise. Magnetostriction and magnetic forces are the main causes of transformer core noise and vibration. Understanding of the relationship from the core material to core structure and core vibration to core noise can help the design of low noise transformer cores. The most appropriate parameter for investigating the relationship between noise and vibration is sound pressure (in the unit of Pascals) in the frequency domain because it is not A-weighted. In this study, the side surfaces of transformer cores were found to emit higher noise than front and top surfaces at low magnetic induction. When the magnetic induction was increased, the effect of magnetic force increased and caused the front surfaces to emit higher noise. For three phase three limb transformer cores, the front surface of the middle limb generated higher noise than the outer limbs due to the effect of T-joint. However this does not translate higher noise level because of the phase difference of the vibration between the limbs. Due to this A-weighted sound power level of three phase, three limb transformer cores were shown to be lower than single phase transformer cores, although at the same cross sectional area and core window size the three phase cores has larger size. A model, developed to separate the effects of magnetostriction and magnetic forces on transformer core vibration, showed that at low induction, magnetostriction is more significant than magnetic forces. The magnetic forces become more significant than magnetostriction when the induction is increased. Magnetostriction primarily depends on material and stress but magnetic forces principally depend on core building. Louder noise can be generated from a core built with low magnetostriction material than higher magnetostriction if the building tolerances are worse. The effect of magnetic forces on transformer core vibration can be reduced by using a bonding technique.

The Current Source Inverter (CSI) is one of the simplest power converter topologies that can convert DC to AC and feed power generated from photovoltaic (PV) cells into the AC grid with a single power conversion stage over the whole PV voltage range. The CSI also provides smooth DC current which is one of the requirements of the PV cells as well as preventing reverse current using unidirectional switches. However, the CSI operates with low efficiency at lower PV voltages, which is where the PV cells produce maximum output power. This low efficiency is caused by large differences in voltage levels between the PV side and the grid side across the converter. This thesis presents an alternative topology to the three-phase CSI by connecting an AC capacitor in series with each AC phase line of the CSI circuit. The presence of the series AC capacitors in the CSI topology allows the AC voltage levels to be adjusted to match the voltage levels of the PV cells. Therefore, the CSI with series AC capacitors is able to operate with optimal DC-AC voltage levels. Performance of the proposed topology is evaluated in comparison to the standard CSI and five other converter topologies based on transformerless circuit concepts selected from those already available in the market and suitable converters discussed in the literature. All converter topologies were modeled and simulated with the SABER simulation software package. The CSI with series AC capacitors prototype was constructed in order to validate the feasibility of the proposed topology and the performance of the proposed topology in comparison to the standard CSI. Simulation results show that the CSI with series AC capacitors provides improved efficiency and better input/output power quality in comparison to the standard CSI. The proposed topology also achieves the lowest output line current distortion, lowest voltage stress across the circuit components and lowest estimated cost of power semiconductors when compared to all considered topologies. Experimental results are also presented to validate the simulation results.

The advancement of the mobile communication industry increases the need for RF power amplifier (RFPA) to be more efficient and linear. The communication network that is shifting towards smaller micro-cell or nano-cell network has also motivated the design of the RF power amplifier to be simple, compact and cost efficient. In this research work, a novel technique for efficiency and linearity improvement of the RFPA is presented. A simplistic approach in the technique called ‘Auxiliary Envelope Tracking' (AET) system has promoted the design for small and straightforward AET tracking generator, a key component in the system. The use of low cost components in the AET tracking generator has made the technique commercially attractive. The AET technique proposes a separation in generating DC and AC components of the AET signal that biases the drain of the RFPA. The separation eases the generation of the signals resulting in low power consumption that leads to efficiency improvement. The investigation of the gain characteristic of gallium nitride (GaN) RFPA has shown an important RFPA attribute where the gain varied substantially as the drain voltage increases. By using the AET technique, the gain characteristic is harnessed to get linearity improvement. In order to validate the technique, AET measurement systems for two-carrier and WCDMA signals were developed and experimented. A special Class AB RFPA is designed and implemented to use dedicatedly for this investigation. In two-carrier signal measurement, a tracking generator is developed that consists of an envelope amplifier (EA) and a diplexer. The RFPA and the tracking generator are then combined to be an integrated AET block. In order to accommodate the high peak-toaverage ratio (PAR) and high bandwidth WCDMA signal, a broadband RF transformer was designed as part of the AET tracking generator to replace the diplexer. The two-carrier and WCDMA signals measurement results have proven that the AET technique is a valid technique for efficiency and linearity improvement. The improvements were achieved with simple, compact and cost-effective implementation.