Electronic Capacitance Tomography systems have proved to be extremely useful in non-invasive measurement for industrial applications. While considerable research effort has been focused on the development and refinement of measurement techniques based on ECT, use of ECT for realtime control has not attracted the same extent of research effort. This work demonstrated that a novel combination of ECT systems and Artificial Neural Networks (ANNs) can be used to control of highly nonlinear industrial systems continuously as demonstrated by the implementation of a neural network-based inverse controller for the MMU laboratory flow. rig conveying the polypropylene pellets. The nature of the flow ofpneumatically conveyed pellets is highly nonlinear which tends to lead to the formation of dunes, necessitating an increase of air velocity to the maximum to clear the dunes, and hence requiring large control energy. If the air velocity can be controlled such that the pellet flow is maintained at a constant rate without the build up of dunes, energy usage associated with such processes can be considerably reduced. One of the main problems in the control of the pneumatic pellet flow system is the difficulty in building good models of the nonlinear dynamics of the system. In this work, ANNs are used to initially build and validate a model of the forward dynamics of the system and then to develop an inverse model of the plant. This inverse model is implemented as a Controller to maintain constant pellet flow and to clear dunes as quickly as possible. Results are obtained from a laboratory flow rig interfaced to a Virtual Instrument Tomographic Measurement System and controlled using dedicated hardware with software implemented in LabView and Matlab. The NN-based controller was highly effective in maintaining a steady pellet flow over long durations of time even in the presence of mass flow disturbances. The results presented in this work showed that a NN-based controller can eliminate energy wastage by automatically clearing dunes as and when they form while maintaining the air velocity at a minimum value necessary to keep the pellet flow homogeneous. Serial and Parallel ECT systems were used in the imaging and control experiments. The additional information obtained by the high imaging rates of the parallel ECT system was used to improve the performance of the controller for long term operations. Hierarchical Self-Organising Maps were also shown to be highly effective in improving the accuracy of the images obtained using the standard Linear Back Projection algorithm for application in ECT-based systems.

Peak current mode control is a popular method of SMPS control due the inherent cycle-by- cycle current limiting, feed-forward control and current sharing ability it provides. However, the subharmonic oscillations which plague peak current mode control must be removed using slope compensation. Until the work presented in this thesis, there have been no true digital implementations of peak current mode control due to the difficulties associated with implementing a digital form of slope compensation. This thesis introduces a complete digital peak current mode converter which uses a novel method of digital slope compensation to remove the subharmonic oscillations observed when using peak current mode control. The digital implementation of peak current mode control is applied to a Buck converter design example which directly compares the proposed digital scheme with an equivalent analog scheme. Exact analytical design equations are derived which allow a specified crossover frequency and phase margin to be achieved concurrently. The l6W Buck converter design example compares the digital peak current mode controlled converter with an analog converter designed to the same specification and tested on the same power stage PCB. The detailed steady state, transient and frequency response results from the hardware experimentations show excellent correlation with the MATLAB simulated converter and are in good agreement with the equivalent analog converter. The crossover frequency is specified as 15kHz and is measured as 14.71kHz on the proposed digital converter with a measured phase margin only 5' less than the specification. The results confirm that the operation of the proposed digital peak current mode control scheme is functionally similar to analog peak current mode control.

This thesis considers the modelling and feedback control of continuous-time systems, focusing on the non- minimal state space (NMSS), proportional- integral-plus (PIP) control methodology. The control problems associated with marine energy devices, in particular wave energy converters (WECs), provide the main motivation and context for this work. The 'high- level' objective for a WEC is to maximise energy extracted by the device; consequently, a range of optimisation strategies have been proposed, including various on- line tuning techniques. However, adaptive tuning requires high performance 'low- level' feedback control of the device actuators, a subject that has received less attention in the literature. To investigate these issues, the thesis employs a simulation of a hydraulic power take-off (PTO) circuit driven by a piston connected to the body of a point absorbing wave energy converter (WEC); the effect of the piston is considered a significant periodic disturbance signal. The damping force exerted by the piston on the body of the WEC is continuously adjusted by changing the torque supplied by an electric generator, allowing the velocity of the WEC to be kept in phase with the incident wave force. The PTO simulation is linked to a hydrodynamic model of the WEC and an optimisation module. Control schemes for tidal turbines are more advanced than those for WECs, being based upon research already undertaken for wind turbines. However, data are more readily available for wind turbines; consequently, this thesis considers a simulation of a wind turbine in which the generator reaction torque and hub speed are related to the rectifier firing angle and blade pitch. Earlier research into PIP control design has largely focused on discrete- time systems, often based on a relatively coarse sampling interval. For a \NEC, a controller based entirely in the continuous-time domain offers several advantages, not least because most of the theoretical work in this area is considered from a physically based modelling perspective. In this thesis, the continuous- time NMSSjPIP control methodology is applied to several practical examples, including the PTO problem, revealing limitations in the previously developed univariate approach. Hence, the present thesis necessarily extends the methodology in several new 'Nays: Basic continuous- time PIP control does not account for the interconnected variables present in many systems, such as the disturbance caused by the piston driving the PTO circuit. For this reason, the author has investigated two forms of feed-forward controller: the first is obtained by extending the non-minimal state vector to include the disturbance signal; the second uses block diagram analysis, an approach found to yield the best performance in simulation. When the disturbance signal caused by the piston is sufficiently far from the operating level upon which the feed- forward controller is based, the response deteriorates. In order to improve disturbance rejection, the thesis introduces a novel non-linear feed- forward compensator obtained from a state dependent representation of the system dynamics. The controller obtained using this method rejects almost all of the disturbance and more accurately follows the set point in comparison to the linear approach. Continuous- time multivariate PIP control algorithms are developed and evaluated using the wind turbine simulation. To address a problem with the identified control models being non-proper or descriptor systems, the thesis develops a novel combined multivariate algebraic decoupling and pole assignment algorithm with no reference to the NMSS model. Finally, the algorithms are evaluated, where appropriate, using other simulated and practical examples, notably a laboratory experiment comprising a connected pair of electric motors. Although a relatively straightforward system to control, it is nonetheless utilised as a preliminary study into practical implementation issues. Indeed, to the author's knowledge, this represents the first hardware demonstration of continuous-time PIP methods. These experiments were conducted in lieu of wave tank experiments which clearly represent the next stage of the research.

A prototype has been designed and constructed that has fed 3kW into a Commercial workcoil at 150 kHz. Another lower power inverter has been built. This was developed with ease of production in mind to aid the transfer of technology to the sponsoring company. The company have adopted this unit and are manufacturing it. The thesis reviews induction heating power supplies with emphasis on those able to operate above 100 kHz. Members of the MOSFET family are described and critically assessed for the application Prototypes of various configurations have been constructed and experience of these has led to the choice of current fed topology as the best for the application. The design and layout of a three phase current fed full bridge inverter that can feed 5 kW into an industrially relevant coil at 400 kHz and a single phase 2.5 kW version are described. Results of tests carried out on the units are presented. A microprocessor system has been selected which has been used for closed loop control of power, temperature and housekeeping tasks such as the supervision of interlocks.

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The performance of earthing systems under variable frequency and transient conditions has been investigated in this research. The work has involved an extensive review of the published literature, theoretical and computational studies of earth electrode systems, laboratory experiments and outdoor tests at the University's earthing test site and at operational power installations. A critique was carried out of the classical fall-of-potential measurement method for determining the earth resistance of earth electrode systems. It was found that when there is insufficient spacing between the earth electrode under test and the auxiliary current return electrode, there can be a significant error when applying the 61.8% rule. This error is negative for single electrodes such as rings or square grids, while, for earth systems involving extended earthing systems such as earthed overhead towerlines, the error is positive. The performance of a variable frequency impedance measurement system (IMS) developed at Cardiff University was tested in the laboratory and in the field. Using a controlled source of noise mixed with a pure sinusoidal waveform, optimal test frequencies of 48Hz and 52Hz were identified to obtain high noise rejection and accurate prediction of the power frequency impedance. The IMS system was applied successfully to measure earth impedance at a range of high voltage operational installations. Calculations based on equivalent circuit models and computer simulations using a commercial numerical code were used to quantify the frequency dependence of the earth impedance of rod, horizontal and grid electrodes in the range DC to IOMHz. It was shown that inductive effects become significant for all electrode systems above a particular frequency referred to as the upturn frequency which is related to resistivity. In high resistivity media, the earth impedance of a rod falls above a particular threshold frequency which may be attributed to capacitive effects. New analytical expressions were derived to describe these features. The effective length and impedance at effective length were calculated for a horizontal earth electrode. It was demonstrated that these quantities are dependent on resistivity and frequency. Simulations and impulse tests on a 275kV transmission tower base show that a significant earth potential rise was found at the tower base, which highlights the importance of assessing transient step and touch voltages under surge conditions. The impulse resistance was found to be equal to the value corresponding to the steady state conditions, for the range of input current shapes considered. However, the impulse response of full tower models was shown to be dependent not only on soil resistivity, but also on the shape of the impulse current. The surge impedance of the tower was determined using a circuit model representation of the tower and frequency analysis of the tower top and tower base potentials. This model gives values higher than those calculated using an analytical expression for a conical tower, which was based on the assumption of zero soil resistivity. High voltage tests results showed that the measured impulse resistance decreases with increasing surge current. This behaviour may be due to non-linear conduction phenomena occurring in the soil (thermal conduction and soil ionisation).

The topic of this thesis is the study of dielectric response of ultra-thin STO films in nano capacitors in external applied electric fields present in the simulation cell. Our model refers to a common ab initio model scheme, and several aspects of the dielectric response of STO films interfaced with a metal electrode where faced. The principal aspect was the modelling of such films in an applied electric field, and the task has been successfully implemented in the context of first principles calculation scheme. In fact, it is possible to interface a layer of metal with a layer of such dielectric material and apply an external field so that the task has been achieved even using , periodic boundary conditions in a DFT context. We prove that it is possible to define and calculate the high frequency dielectric constant foe. The former is given by the ratio.. I present, in the second part, a general formula with the aim to calculate the 'group velocity', of a quantal system, where I firstly developed my derivation oa a real vector field in an abstract geometrical way. I have discussed a particular application aimed to condesed matter where I have shown that at order of expansion of the Hamiltonian of power of lie it is possible to obtain the qunatum Lorentz force the expression of the power delivered by an external electromagnetic field to the electronic sub-system. I also wrote the Berry phase in a mechanical way and introduce a new quantum phase. I have shown that those phases can be derived by two 'new' vector fields corresponding to: 'angular-momentum' field and a vector field that does not have any classical analogue.

Generation of control torque at low cost for highly agile satellite missions is generally achieved with momentum exchanged devices, such as momentum or reaction wheels and control moment gyros (CMGs) with high slew manoeuvrability. However, the generation of a high control torque from the respective actuators requires high power, large mass and high cost. The main objective of this research is to introduce a novel type of attitude control actuator that generates control torques about all three principal axes of a rigid satellite using only a spinning wheel and tilt mechanisms. The tilt mechanism changes the spin axis of the spinning wheel about the tilt plane axes thereby generating control torque about an axis in the plane that is orthogonal to both the tilt axes and the spinning wheel axis. To complete the 3 DoF torque generation, torque is generated about the spinning wheel axis by varying the spinning wheel speed. Few literature sources describe the concept of inertial actuator with 3 DoF torque capabilities. But in this research, a novel equation of motion is developed for the proposed inertial actuator from the fundamental laws of physics that does not require the popular pseudo-inversion as obtained with CMG systems. An extended LQR control law named HPB (High Performance Bounded) control that uses gain-scheduling and bounded torque control to provide better attitude performance than classical LQR with the advantage of incorporating a maximum torque constraints, was adapted to control a mathematical model of a rigid satellite. A prototype of the proposed actuator was built using commercial off the shelf components (COTS). The entire hardware design process is described and is accompanied with extended hardware and software simulations developed using CAD and MatLab/Simulink software. The newly proposed actuator has several distinct advantages compared to other existing inertial actuators. This includes the ability to generate active control torque in all principal axes of a rigid satellite compared to having conventional reaction wheels aligned to each of the three principal axes of the satellite or a cluster of CMGs. This translates to the lower mass, lower power requirement and low cost that are the critical driving factors in the design of any small satellite ACS. This new concept presents advantages for earth observation missions where the required slew angle is limited and for small satellites where accommodating multiple actuators reduces the size that can be allocated to payloads. Academically, significant contributions have been made to the field including: development of a new set of dynamic equations of motion for the inertial actuator, extending the conventional LQR control logic for a more time efficient control, 3 DoF testbed development, systematic design and build of the proposed actuator using commercial of the shelf components, and 3 DoF torque capability experimentation.