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The research focuses on an investigation of the erosion-corrosion behaviour of Cu-Ni-base alloys in aqueous environments. The principal objectives of the research were to examine the fundamental mechanisms of the erosion-corrosion attack. The work was focused on a standard Cu-10%Ni alloy that is used extensively in a variety of marine industries and on Marinel alloy, which is a high strength precipitation-hardened copper-nickel alloy. Erosion-corrosion tests were carried out for exposure times up to 72 hours, in a solid free 3.5% NaCl solution impinging at velocities of 2.38-86 m/sec, (Re=4500-86000), at temperatures of 19°C and 35°C. The overall erosion-corrosion behaviour and the direct corrosion component were monitored using gravimetric and electrochemical-monitoring techniques. Contributes from mechanical erosions were assessed by cathodically protecting specimens under impingement conditions. The research also considered the influence of various parameters such as temperature, time, velocity, salinity variations, and impingement angle. The extent and morphology of material deterioration and protective film formation under various environmental conditions were assessed, utilizing surface profiling equipment and light optical and scanning electron microscopy. The work has quantified the complex contributions of corrosion, erosion and synergy to the overall erosion-corrosion material loss. An important finding was the substantial superior erosion-corrosion resistance of Marinel compared to the standard Cu-10%Ni, with interesting effects of impinging velocity and time of exposure being observed. Also this work provided some clear evidence of significant potential benefits in terms of erosion-corrosion resistance, obtained by the exposure of Marinel at the elevated temperature.

The biofouling resistant coatings of hydrogel containing the cationic surfactants benzalkonium chloride and Arquad 2C-75 both extended the fouling free period in marine temperate waters. In the case of BAC the coating stayed clean for 10-12 weeks and the Arquad 2C-75 for 12-14 weeks. Due to the longer life of the hydrogel containing the Arquad 2C-75 instrument trials were carried out using this material. An effective method of attaching the coatings to the optical and membrane ports of sensors was developed and allows the coating to be either held in either a screw down or bolted polymer ring. The diffusion coefficient of cationic surfactants in seawater is reduced compared to diffusion coefficients in freshwater. In seawater the diffusion coefficient of benzalkonium chloride was found to be 2.44 x 10-6 cm2 s-1 compared to 7.78 x 10-6 cm2 s-1 in distilled water at 25°C. Careful choice of gas permeable membrane can result in a slightly longer biofouling lifetime, but only by 1-2 weeks. At 6 weeks all gas permeable membranes had significant fouling which affected their gas permeability. The diffusion rates of ammonia gas, a gas commonly measured in the sea, through PTFE gas sensor membranes varied between PTFE manufacturers with flux measurements ranging from 0.05-1131 µg cm-2 h-1. In addition to the hydrogel testing on instruments within this project a variety of external research groups and environmental agencies are currently testing the hydrogels on their instrumental ports.

This thesis describes the modelling, analysis and design of multirate sampled-data feed-back via the polynomial equations approach. The key theoretical contribution constitutes the embedding of the principles underpinning and algebra related to the switch and frequency decomposition procedures within a modern control framework, thereby warranting the use of available computer-aided control systems design software. A salient feature of the proposed approach consequently entails the designation of system models that possess dual time- and frequency-domain interpretations. Expositionally, the thesis initially addresses scalar systems excited by deterministic inputs, prior to introducing stochastic signals and culminates in an analysis of multivariable configurations. In all instances, overall system representations are formulated by amalgamating models of individual sub-systems. The polynomial system descriptions are shown subsequently to be compatible with the Linear Quadratic Gaussian and Generalised Predictive Control feedback system synthesis methods provide causality issues are dealt with appropriately. From a practical perspective, the polynomial equations approach proffers an alternative methodology to the state-variable techniques customarily utilised in this context and affords the insights and intuitive appeal associated with the use of transfer function models. Numerical examples are provided throughout the thesis to illustrate theoretical developments.

The work in this thesis starts with the development of a Graphical User Interface to aid the manual control of the experimental crane model and to achieve a better container management system. A structural analysis of the laboratory rig is then carried out. The technique used is to divide the whole structure into two parts: a stationary framework and a moving substructure (including its attachments). The dynamic effect of the moving substructure is represented by four equivalent, time-dependent, contacting forces (or lumped masses), and the dynamic behaviour of the stationary framework, induced by the moving substructure, is predicted by computing the responses to these forces (or lumped masses). Before the forced vibration responses can be obtained a finite element model of the scale crane rig has first to be established and validated by means of modal testing. A general technique for incorporating a standard finite element package into a procedure to calculate the dynamic responses of structures due to time-dependent moving point forces is then developed. In order to take the inertia effects of the moving substructure into account a new concept of equivalent time-dependent moving lumped masses is introduced. A general procedure has been developed to allow a standard finite element package to be extended to deal with the dynamic analyses of a three-dimensional framework subjected to the two-dimensional multiple moving masses. The theoretical results obtained are validated by comparison with experimental findings.

The thesis describes the development of a new continuum damage mechanics (hereafter, CDM) model for the deformation and failure of brittle matrix composites reinforced with continuous fibres. The CDM model is valid over sizes scales large compared to the spacing of the fibres and the dimensions of the damage. The composite is allowed to sustain damage in the form of matrix micro-cracking, shear delamination, tensile delamination and fibre failure. The constitutive equations are developed by decomposing the composite compliance into terms attributable to the fibre and matrix, and modelling the competing failure modes by intersecting failure surfaces based on maximum stress theory. The fibres are treated as being weakly bonded to the matrix so that the fibres only transmit axial loads, and fail in tension. The matrix is modelled as isotropic linear elastic and is treated as transversely-isotropic after damage has initiated. The effect of multiple matrix cracking on the stiffness was determined from experimental data, while failure was modelled by a rapid decay in the load bearing capacity. Although the model is motivated largely to proportional loading, matrix unloading and damage closure has been modelled by damage elasticity. During compression, the matrix stiffness is identical to the undamaged state with the exception that the fibres are assumed not to transmit compressive loads. The model was implemented computationally through a FORTRAN subroutine interfaced with the ABAQUS/Standard finite element solver. The CDM model was validated by comparing experimental and computational results of test specimens with unidirectional and balanced 0°-90° woven fibres of a brittle matrix composite, fabricated from polyester fibres in a polyester matrix. This composite system exhibits low elastic mismatch between fibres and matrix, and has similar non-dimensionalised stress-strain response to a SiC/SiC composite proposed for the exhaust diffuser unit of the Rolls-Royce EJ200 aero-engine.

This thesis focuses on the development of data-driven automated techniques to enhance performance assessment methods. These techniques include process control loop status monitoring, fault localisation in a number of interacting control loops and the detection and isolation of multiple oscillations in a multi-loop situation. Not only do they make use of controlled variables, but they also make use of controller outputs, indicator readings, set-points and controller settings. The idea behind loop status is that knowledge of the current behaviour of a loop is important when assessing MVC-based performance, because of the assumptions that are made in the assessment. Current behaviour is defined in terms of the kind of deterministic trend that is present in the loop at the time of assessment. When the status is other than steady, MVC-based approaches are inappropriate. Either the assessment must be delayed until steady conditions are attained or other methods must be applied. When the status is other than steady, knowledge of current behaviour can help identify the possible cause. One way of doing this is to derive another statistic, the overall loop performance index (OLPI), from loop status. The thesis describes a novel fault localisation technique, which analyses this statistic to find the source of a plant-wide disturbance, when a number of interacting control loops are perturbed by a single dominant disturbance/fault. Although the technique can isolate a single dominant oscillation, it is not able to isolate the sources of multiple, dominant oscillations. To do this, a novel technique is proposed that is based on the application of spectral independent component analysis (ICA). Spectral independent component analysis (spectral ICA) is based on the analysis of spectra derived via a discrete Fourier transform from time domain process data. The analysis is able to extract dominant spectrum-like independent components each of which has a narrow-bank peak that captures the behaviour of one of the oscillation sources. It is shown that the extraction of independent components with single spectral peaks can be guaranteed by an ICA algorithm that maximises the kurtosis of the independent components (ICs). This is a significant advantage over spectral principle component analysis (PCA), because multiple spectral peaks could be present in the extracted principle components (PCs), and the interpretation of detection and isolation of oscillation disturbances based on spectral PCs is not straightforward. The novel spectral ICA method is applied to a simulated data set and to real plant data obtained from an industrial chemical plant. Results demonstrate its ability to detect and isolate multiple dominant oscillations in different frequency ranges.

The performance of robotic manipulators is critical to their widespread use in industry. As manipulators become faster, their potential productivity can rise thus improving the return on the investment required to purchase them. Improving accuracy, on the other hand, increases the range of tasks for which the manipulator is suitable. The speed and accuracy of a manipulator is partly determined by the capability of the algorithm used to control it. Whilst being a highly non-linear multiple input, multiple output device, however, most industrial controllers are derived on the basis that the robot is a series of independent, linear actuator+ link subsystems. The resulting independent joint controller is simple to design and implement but is limited in its performance as link interactions and the non-linear effects of centrifugal and Coriolis forces degrade the accuracy at high manipulator velocities. Improvements in the control of manipulators may be made by incorporating a mathematical model of the manipulator in the control algorithm. Control schemes such as `computed torque' incorporate an inverse model of the manipulator to calculate the input torques required to force the end-effector to follow a desired trajectory. The equations of motion required to implement these controllers are large and complex even for relatively simple manipulators. This thesis explores how bond graph representations of robotic manipulators may be used to automate the implementation of model based controllers. To provide a practical basis for this research the bond graph derived controllers are tested on an experimental rigid, planar, direct drive two-link manipulator. It is shown how the bondgraph for this manipulator, including d.c. motor actuators, can be constructed and used to derive the equations of motion of the manipulator automatically. The bond graph model is then validated by comparing simulations obtained using these equations of motion with experimental data.

This work represents an investigation of the corrosion behaviour of primarily high-grade alloys in marine environments. A range of marine conditions of varying severity has been considered and their effect on the electrochemical corrosion characteristics assessed. The study has utilised a range of electrochemical monitoring techniques, light and scanning electro microscopy and other surface techniques to assess the extent and morphology of corrosion attack under certain conditions. Principal components of the study include the effect of elevated temperature (up to 60oC) on corrosion initiation and propagation in static and high velocity impinging seawater. In addition, the effect of micro and macro fouling has been assessed using immersion tests and a hydrodynamic model. Continuation of the biological effects on corrosion looked at the effect of the presence and activity of Sulphate Reducing Bacteria (SRB) on corrosion mechanism. Correlations between accelerated laboratory tests and the real time behaviour of materials have been successfully made. Methods to counteract fouling often include the use of biocides and, in this study, the effect of high levels of hypochlorite dosing has been investigated. Mechanical and corrosion effects by liquid impact and by liquid-solid impact constitute a major part of this work and the use of electrochemical tests has enabled the proportions of weight loss on a given material attributed to corrosion, erosion and a synergistic factor to be elucidated. Several options exist to combat excessive deterioration due to mechanical wear. Two processes, shot-peening and laser irradiation, have been assessed primarily for corrosion resistance in a marine environment.

This thesis is concerned with the analysis, control and identification of hybrid dynamical systems. The main focus is on a particular class of hybrid systems consisting of linear subsystems. The discrete dynamic, i.e., the change between subsystems, is unknown or nondeterministic and cannot be influenced, i.e. controlled, directly. However changes in the discrete dynamic can be detected immediately, such that the current dynamic (subsystem) is known. In order to motivate the study of hybrid systems and show the merits of hybrid control theory, an example is given. It is shown that real world systems like Anti Locking Brakes (ABS) are naturally modelled by such a class of linear hybrids systems. It is shown that purely continuous feedback is not suitable since it cannot achieve maximum braking performance. A hybrid control strategy, which overcomes this problem, is presented. For this class of linear hybrid system with unknown discrete dynamic, a framework for robust control is established. The analysis methodology developed gives a robustness radius such that the stability under parameter variations can be analysed. The controller synthesis procedure is illustrated in a practical example where the control for an active suspension of a car is designed. Optimal control for this class of hybrid system is introduced. It is shows how a control law is obtained which minimises a quadratic performance index. The synthesis procedure is stated in terms of a convex optimisation problem using linear matrix inequalities (LMI). The solution of the LMI not only returns the controller but also the performance bound. Since the proposed controller structures require knowledge of the continuous state, an observer design is proposed. It is shown that the estimation error converges quadratically while minimising the covariance of the estimation error. This is similar to the Kalman filter for discrete or continuous time systems. Further, we show that the synthesis of the observer can be cast into an LMI, which conveniently solves the synthesis problem.