This thesis describes a novel approach for adaptive optimal control and demonstrates its application to a variety of systems, including motion control learning for legged robots. The new controller, called “FOX”, uses a modified form of Albus’s CMAC neural network. It is trained to generate control signals that minimize a system’s performance error. A theoretical consideration of the adaptive control problem is used to show that FOX must assign each CMAC weight an “eligibility” value which controls how that weight is updated. FOX thus implements a kind of reinforcement learning which makes it functionally similar to the cerebellum (a part of the brain that modulates movement). A highly efficient implementation is described which makes FOX suitable for on-line control. FOX requires a small amount of dynamical information about the system being controlled: the system’s impulse response is used to choose the rules that update the eligibility values. A FOX-based controller design methodology is developed, and FOX is tested on four control problems: controlling a simulated linear system, controlling a model gantry crane, balancing an inverted pendulum on a cart, and making a wheeled robot follow a path. In each case FOX is effective: it associates sensor values with (and anticipates) the correct control actions, it compensates for system nonlinearities, and it provides robust control as long as the training is comprehensive enough. FOX is also applied to the control of a simulated hopping monoped, and a walking biped. FOX learns parameters that fine tune the movements of pre-programmed controllers, in a manner analogous to the cerebellar modulation of spinal cord reflexes in human movement. The robots are successfully taught how to move with a steady gait along flat ground, in any direction, and how to climb and descend slopes.

In February 1965, a research programme in radio astronomy was started by the Electrical Engineering Department of the University of Auckland. One of the main purposes of the programme was to provide a unified theme for post-graduate research in the department. The initial aim of the programme was to develop through graduate research, sufficient facilities for radio astronomy observations at frequencies below 100Mhz. Being among the first group of graduate students in the programme, the author was given the problem of studying the antenna requirements for the programme. At the frequencies concerned, the antenna systems are often large and expensive. As the programme is supported at present, only by funds for ordinary graduate research, there is a great need for an antenna array with good performance at minimal cost. This has led the author into his main field of study, viz. the synthesis of arrays with non-uniformly spaced directional elements. The use of directional elements together with non-uniform spacing technique permits larger inter-element spacings in the array without resulting in large sidelobes in the response pattern. Available synthesis methods are inadequate despite the large number of papers published on the subject since its introduction 7 years ago. The synthesis problem involves the determination of a set of element positions to give a desirable response pattern. Because the element position variables lie in the arguments of the cosine terms in the pattern function, the problem becomes highly non-linear. For simplicity, most of the published works have assumed isotropic elements. The methods proposed have been mainly centred on some form of linear approximations to the problem. Consequently, these methods are only effective over a limited region of space*. As a result of this limitation, good pattern characteristics can only be achieved with impractically small spacings. For arrays with less than about 50 elements, the element spacings can best be determined by an optimisation procedure. This method involves the repeated application of small pertubations to the element positions of a starting array until maximum improvement to the sidelobe levels of the array is achieved. An efficient perturbation method has been proposed by Baklanov et al using a matrix approach. Because of the inherent limitation of this method, Baklanov’s arrays are mostly impractical due to the occurrence of small spacings. Such limitations are removed by the author through the use of a modified synthesis procedure. With this new procedure, the author was able to control the pattern over a considerably larger area in space. Thus arrays with average inter-element spacings up to two wavelengths can be synthesised with positive control over all sidelobes in the arrays. The sidelobe levels of the author’s arrays are, as a whole, bery close to the levels of the corresponding theoretically optimal patterns. The element directivities are taken into account in the synthesis process. A total of 30 non-uniformly spaced arrays of varying sizes and sidelobe levels were synthesised using the method developed. Since all these arrays have near to optimal sidelobe characteristics, they provide a basis for a detailed study of the properties of non-uniformly spaced arrays as a whole. A number of interesting points are revealed when pattern parameters like gain, beamwidth, sidelobe level, etc., are studied in relation with the spacing characteristics of the arrays. A better understanding of the properties of non-uniformly spaced arrays is also gained by comparing the pattern characteristics of the synthesised arrays with that of current tapered arrays. The design and testing of a 16-element non-uniformly spaced array of Yagi antennas is described in Chapter 4. This array demonstrates one practical application of the synthesis work reported in this thesis. *The word ‘space’ used throughout the Introduction does not mean the physical space, which is defined, in a 2-D case, by the zenith angle θ. Here, the space is defined by the parameter χ=2πdavsinθ/λ. Thus with an average inter-element spacing dav= λ, the visible space is defined by χ=0 to π.

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / Future telecommunication networks will employ digital transmission techniques. Such networks will provide a number of benefits including the ability to integrate voice and non-voice messages. The transmission channel of this network can be represented by a cascaded channel composed of a number of elementary channels connected in series. Therefore the modelling of such a channel is of particular interest. The influence of noise and other impairments in the cascaded binary channel cause errors which may be represented by a binary signal called the error sequence. Consequently, an important step in digital channel modelling is estimation of parameters and distribution functions which characterise the statistical properties of error sequences in the channel. Thus, the development of efficient methods for this estimation is a problem of long term interest which should be properly solved. This thesis presents methods and techniques for parameter (primarily the probability of error) and distribution function (primarily the error gap complementary distribution function) estimation using the error sequences obtained by measurement or simulation in elementary or cascaded channels. Theoretical analysis and testing confirm that it is possible to control the accuracy and reliability of estimation. Two principal and practical methods for the probability of error estimation are developed: the modified Monte Carlo method (MMC); and the method based on Chebyshev inequality (MCI). In contrast to the traditional Monte Carlo method based on classical statistics, the methods developed in this thesis aim to specify the sample size required to achieve the desired accuracy. The methods developed are based on the dependence of the sample size on the estimated value of a parameter being estimated. Hence the sample size is a random variable and the confidence limits factor (which specifies the width of confidence interval in respect to the estimated value) is a constant. Based on these methods, this thesis proposes and demonstrates two techniques for parameter estimation. The traditional Monte Carlo method has been primarily used for the probability of error estimation in channels without memory. In this thesis the capabilities of this method are extended to the case of estimating the probability of error in channels with memory and cascaded channels. However, even with this extension, this method is not practical due to its complexity and limitations on the qualification and quantification of the accuracy and reliability of estimation. Also, the extended method is unable to satisfactorily estimate the probability of error in cascaded channels with memory; nor could it improve the speed of the estimation process. Two methods and two techniques for distribution function estimation are developed in this thesis. They are demonstrated by estimating the error gap complementary functions of simulated data. For this purpose, simulators of binary channels with and without memory have been developed. The methods and techniques are characterised by their simplicity in application; ability to quantify the accuracy and reliability; time efficiency; and real time capability. The wider application of the methods and techniques developed in this thesis are demonstrated on three examples: a distribution function estimation using data obtained by indoor wideband radio propagation measurement; BER characteristics measurement; and measurement of the residual probability of error in transmission systems using error correcting codes. From the results obtained in the thesis some recommendations for future work in the field of digital channel modelling and simulation are discussed.

This thesis describes a novel approach for adaptive optimal control and demonstrates its application to a variety of systems, including motion control learning for legged robots. The new controller, called “FOX”, uses a modified form of Albus’s CMAC neural network. It is trained to generate control signals that minimize a system’s performance error. A theoretical consideration of the adaptive control problem is used to show that FOX must assign each CMAC weight an “eligibility” value which controls how that weight is updated. FOX thus implements a kind of reinforcement learning which makes it functionally similar to the cerebellum (a part of the brain that modulates movement). A highly efficient implementation is described which makes FOX suitable for on-line control. FOX requires a small amount of dynamical information about the system being controlled: the system’s impulse response is used to choose the rules that update the eligibility values. A FOX-based controller design methodology is developed, and FOX is tested on four control problems: controlling a simulated linear system, controlling a model gantry crane, balancing an inverted pendulum on a cart, and making a wheeled robot follow a path. In each case FOX is effective: it associates sensor values with (and anticipates) the correct control actions, it compensates for system nonlinearities, and it provides robust control as long as the training is comprehensive enough. FOX is also applied to the control of a simulated hopping monoped, and a walking biped. FOX learns parameters that fine tune the movements of pre-programmed controllers, in a manner analogous to the cerebellar modulation of spinal cord reflexes in human movement. The robots are successfully taught how to move with a steady gait along flat ground, in any direction, and how to climb and descend slopes.

In February 1965, a research programme in radio astronomy was started by the Electrical Engineering Department of the University of Auckland. One of the main purposes of the programme was to provide a unified theme for post-graduate research in the department. The initial aim of the programme was to develop through graduate research, sufficient facilities for radio astronomy observations at frequencies below 100Mhz. Being among the first group of graduate students in the programme, the author was given the problem of studying the antenna requirements for the programme. At the frequencies concerned, the antenna systems are often large and expensive. As the programme is supported at present, only by funds for ordinary graduate research, there is a great need for an antenna array with good performance at minimal cost. This has led the author into his main field of study, viz. the synthesis of arrays with non-uniformly spaced directional elements. The use of directional elements together with non-uniform spacing technique permits larger inter-element spacings in the array without resulting in large sidelobes in the response pattern. Available synthesis methods are inadequate despite the large number of papers published on the subject since its introduction 7 years ago. The synthesis problem involves the determination of a set of element positions to give a desirable response pattern. Because the element position variables lie in the arguments of the cosine terms in the pattern function, the problem becomes highly non-linear. For simplicity, most of the published works have assumed isotropic elements. The methods proposed have been mainly centred on some form of linear approximations to the problem. Consequently, these methods are only effective over a limited region of space*. As a result of this limitation, good pattern characteristics can only be achieved with impractically small spacings. For arrays with less than about 50 elements, the element spacings can best be determined by an optimisation procedure. This method involves the repeated application of small pertubations to the element positions of a starting array until maximum improvement to the sidelobe levels of the array is achieved. An efficient perturbation method has been proposed by Baklanov et al using a matrix approach. Because of the inherent limitation of this method, Baklanov’s arrays are mostly impractical due to the occurrence of small spacings. Such limitations are removed by the author through the use of a modified synthesis procedure. With this new procedure, the author was able to control the pattern over a considerably larger area in space. Thus arrays with average inter-element spacings up to two wavelengths can be synthesised with positive control over all sidelobes in the arrays. The sidelobe levels of the author’s arrays are, as a whole, bery close to the levels of the corresponding theoretically optimal patterns. The element directivities are taken into account in the synthesis process. A total of 30 non-uniformly spaced arrays of varying sizes and sidelobe levels were synthesised using the method developed. Since all these arrays have near to optimal sidelobe characteristics, they provide a basis for a detailed study of the properties of non-uniformly spaced arrays as a whole. A number of interesting points are revealed when pattern parameters like gain, beamwidth, sidelobe level, etc., are studied in relation with the spacing characteristics of the arrays. A better understanding of the properties of non-uniformly spaced arrays is also gained by comparing the pattern characteristics of the synthesised arrays with that of current tapered arrays. The design and testing of a 16-element non-uniformly spaced array of Yagi antennas is described in Chapter 4. This array demonstrates one practical application of the synthesis work reported in this thesis. *The word ‘space’ used throughout the Introduction does not mean the physical space, which is defined, in a 2-D case, by the zenith angle θ. Here, the space is defined by the parameter χ=2πdavsinθ/λ. Thus with an average inter-element spacing dav= λ, the visible space is defined by χ=0 to π.

Far from being simply a necessary appliance to extend our day, artificial light has a great influence on human behaviour and wellbeing, perception of the surroundings and comfort. The energy needed for lighting is also a significant impact on our natural resources. For these two broad reasons lighting systems that improve the human visual and perceptual experience and reduce energy use are of widespread value. This work covers research into the application of LED technology as the next generation of mainstream lighting. It looks at the reasons why this technology is set to become the dominant way in which we light our lives, and the technical hurdles that are slowing this shift in lighting. It also presents the development, testing and prototyping of such an LED lighting product for use in the architectural market. This niche application is where LED lighting is currently most suited, due to the compactness, colour adjustability and lower colour rendering required. Establishing the technology here will help to gain consumer appreciation and acceptance of this beneficial and useful new paradigm in lighting. The design incorporates a shape that is pleasing to the eye with a simple oval profile. It was designed to be subtle and compact, blending into the ceiling as cleanly as possible. Practical testing on the finished prototype showed it to produce a wide range of colours and colour temperatures, while maintaining a safe LED temperature. The simplicity also makes the unit competitive in terms of cost.

Distributed generation has the potential to reduce the supply-demand gap emerging in New Zealand’s electricity market. Thereby it can improve the overall network efficiency, harness renewable energy resources and reduce the need for upgrading of existing distribution lines. A typical New Zealand rural community consisting of three adjacent farms at Totara Valley near Woodville represents a demonstration site on distributed generation for Massey University and Industrial Research Limited. Local renewable energy resources are being used for the purpose of sustainable development. Alternative micro-scale technologies are being combined to achieve a valuable network support. This paper is an in-depth report on the implementation process of the HyLink system; a system which utilises hydrogen as an energy carrier to balance and transport the fluctuating wind power. The report documents its development from the laboratory stage to commissioning at Totara Valley, which was carried out under direction of Industrial Research Limited. The PEM electrolyser’s performance at different stack temperatures was investigated. It was found that hydrogen production increases at the same voltage with a higher stack temperature. This is due to the improved kinetics of the electrochemical reactions and decreased thermodynamic energy requirement for water electrolysis. The electrolyser efficiency measurement at the half of its maximal power input (247 W) resulted in 65.3%. Thereby the stack temperature attained less than half of the allowed limit of 80°C. The capture of the excess heat by insulation can improve the electrolyser’s efficiency. Pressure tests were performed on the 2 km long pipeline at Totara Valley using hydrogen and natural gas in order to test their permeability. The results were compared with previous studies at Massey University and with data obtained from the industry. The hydrogen permeability was measured to be 5.5 * 10[to the power of]-16 mol m m[to the power of]-2 s[to the power of]-1 Pa[to the power of]-1 for a 2 km MDPE pipe. This is about half the result obtained from previous studies on hydrogen permeability through MDPE at Massey University which was undertaken at room temperature. The reason for this discrepancy is likely to be the lower ambient temperature during the measurement at Totara Valley, which can be supported with the Arrhenius equation. It was furthermore measured that the power loss due to hydrogen diffusion through the pipeline walls during the fuel cell operation is about 1.5 W at the current system operation mode. A techno-economic analysis of the system was undertaken applying the micro-power optimisation software HOMER as a simulation tool. Two operation modes of the system were investigated, the load following and the peak demand compensating. The simulation results reveal that the durability and the cost of the electrochemical energy conversion devices; electrolyser and fuel cell, are the main hurdles which need to be overcome on the path in introducing hydrogen based energy systems like HyLink. Finally, economic optimisation modelling of the small-scale system by best component alignment was performed. It was found that the electrolyser capacity down-rating of 80% in relation to the wind turbine capacity, leads to a minimal system levelised cost. In addition to this, the impact of various wind turbine/electrolyser subsystems and pipeline storage capacities on the fuel cell capacity factor and on the system levelised cost in the load following operation mode was analysed. The outcomes can be useful for further HyLink related energy system planning.

Distributed generation has the potential to reduce the supply-demand gap emerging in New Zealand’s electricity market. Thereby it can improve the overall network efficiency, harness renewable energy resources and reduce the need for upgrading of existing distribution lines. A typical New Zealand rural community consisting of three adjacent farms at Totara Valley near Woodville represents a demonstration site on distributed generation for Massey University and Industrial Research Limited. Local renewable energy resources are being used for the purpose of sustainable development. Alternative micro-scale technologies are being combined to achieve a valuable network support. This paper is an in-depth report on the implementation process of the HyLink system; a system which utilises hydrogen as an energy carrier to balance and transport the fluctuating wind power. The report documents its development from the laboratory stage to commissioning at Totara Valley, which was carried out under direction of Industrial Research Limited. The PEM electrolyser’s performance at different stack temperatures was investigated. It was found that hydrogen production increases at the same voltage with a higher stack temperature. This is due to the improved kinetics of the electrochemical reactions and decreased thermodynamic energy requirement for water electrolysis. The electrolyser efficiency measurement at the half of its maximal power input (247 W) resulted in 65.3%. Thereby the stack temperature attained less than half of the allowed limit of 80°C. The capture of the excess heat by insulation can improve the electrolyser’s efficiency. Pressure tests were performed on the 2 km long pipeline at Totara Valley using hydrogen and natural gas in order to test their permeability. The results were compared with previous studies at Massey University and with data obtained from the industry. The hydrogen permeability was measured to be 5.5 * 10[to the power of]-16 mol m m[to the power of]-2 s[to the power of]-1 Pa[to the power of]-1 for a 2 km MDPE pipe. This is about half the result obtained from previous studies on hydrogen permeability through MDPE at Massey University which was undertaken at room temperature. The reason for this discrepancy is likely to be the lower ambient temperature during the measurement at Totara Valley, which can be supported with the Arrhenius equation. It was furthermore measured that the power loss due to hydrogen diffusion through the pipeline walls during the fuel cell operation is about 1.5 W at the current system operation mode. A techno-economic analysis of the system was undertaken applying the micro-power optimisation software HOMER as a simulation tool. Two operation modes of the system were investigated, the load following and the peak demand compensating. The simulation results reveal that the durability and the cost of the electrochemical energy conversion devices; electrolyser and fuel cell, are the main hurdles which need to be overcome on the path in introducing hydrogen based energy systems like HyLink. Finally, economic optimisation modelling of the small-scale system by best component alignment was performed. It was found that the electrolyser capacity down-rating of 80% in relation to the wind turbine capacity, leads to a minimal system levelised cost. In addition to this, the impact of various wind turbine/electrolyser subsystems and pipeline storage capacities on the fuel cell capacity factor and on the system levelised cost in the load following operation mode was analysed. The outcomes can be useful for further HyLink related energy system planning.

Distributed generation has the potential to reduce the supply-demand gap emerging in New Zealand’s electricity market. Thereby it can improve the overall network efficiency, harness renewable energy resources and reduce the need for upgrading of existing distribution lines. A typical New Zealand rural community consisting of three adjacent farms at Totara Valley near Woodville represents a demonstration site on distributed generation for Massey University and Industrial Research Limited. Local renewable energy resources are being used for the purpose of sustainable development. Alternative micro-scale technologies are being combined to achieve a valuable network support. This paper is an in-depth report on the implementation process of the HyLink system; a system which utilises hydrogen as an energy carrier to balance and transport the fluctuating wind power. The report documents its development from the laboratory stage to commissioning at Totara Valley, which was carried out under direction of Industrial Research Limited. The PEM electrolyser’s performance at different stack temperatures was investigated. It was found that hydrogen production increases at the same voltage with a higher stack temperature. This is due to the improved kinetics of the electrochemical reactions and decreased thermodynamic energy requirement for water electrolysis. The electrolyser efficiency measurement at the half of its maximal power input (247 W) resulted in 65.3%. Thereby the stack temperature attained less than half of the allowed limit of 80°C. The capture of the excess heat by insulation can improve the electrolyser’s efficiency. Pressure tests were performed on the 2 km long pipeline at Totara Valley using hydrogen and natural gas in order to test their permeability. The results were compared with previous studies at Massey University and with data obtained from the industry. The hydrogen permeability was measured to be 5.5 * 10[to the power of]-16 mol m m[to the power of]-2 s[to the power of]-1 Pa[to the power of]-1 for a 2 km MDPE pipe. This is about half the result obtained from previous studies on hydrogen permeability through MDPE at Massey University which was undertaken at room temperature. The reason for this discrepancy is likely to be the lower ambient temperature during the measurement at Totara Valley, which can be supported with the Arrhenius equation. It was furthermore measured that the power loss due to hydrogen diffusion through the pipeline walls during the fuel cell operation is about 1.5 W at the current system operation mode. A techno-economic analysis of the system was undertaken applying the micro-power optimisation software HOMER as a simulation tool. Two operation modes of the system were investigated, the load following and the peak demand compensating. The simulation results reveal that the durability and the cost of the electrochemical energy conversion devices; electrolyser and fuel cell, are the main hurdles which need to be overcome on the path in introducing hydrogen based energy systems like HyLink. Finally, economic optimisation modelling of the small-scale system by best component alignment was performed. It was found that the electrolyser capacity down-rating of 80% in relation to the wind turbine capacity, leads to a minimal system levelised cost. In addition to this, the impact of various wind turbine/electrolyser subsystems and pipeline storage capacities on the fuel cell capacity factor and on the system levelised cost in the load following operation mode was analysed. The outcomes can be useful for further HyLink related energy system planning.

Distributed generation has the potential to reduce the supply-demand gap emerging in New Zealand’s electricity market. Thereby it can improve the overall network efficiency, harness renewable energy resources and reduce the need for upgrading of existing distribution lines. A typical New Zealand rural community consisting of three adjacent farms at Totara Valley near Woodville represents a demonstration site on distributed generation for Massey University and Industrial Research Limited. Local renewable energy resources are being used for the purpose of sustainable development. Alternative micro-scale technologies are being combined to achieve a valuable network support. This paper is an in-depth report on the implementation process of the HyLink system; a system which utilises hydrogen as an energy carrier to balance and transport the fluctuating wind power. The report documents its development from the laboratory stage to commissioning at Totara Valley, which was carried out under direction of Industrial Research Limited. The PEM electrolyser’s performance at different stack temperatures was investigated. It was found that hydrogen production increases at the same voltage with a higher stack temperature. This is due to the improved kinetics of the electrochemical reactions and decreased thermodynamic energy requirement for water electrolysis. The electrolyser efficiency measurement at the half of its maximal power input (247 W) resulted in 65.3%. Thereby the stack temperature attained less than half of the allowed limit of 80°C. The capture of the excess heat by insulation can improve the electrolyser’s efficiency. Pressure tests were performed on the 2 km long pipeline at Totara Valley using hydrogen and natural gas in order to test their permeability. The results were compared with previous studies at Massey University and with data obtained from the industry. The hydrogen permeability was measured to be 5.5 * 10[to the power of]-16 mol m m[to the power of]-2 s[to the power of]-1 Pa[to the power of]-1 for a 2 km MDPE pipe. This is about half the result obtained from previous studies on hydrogen permeability through MDPE at Massey University which was undertaken at room temperature. The reason for this discrepancy is likely to be the lower ambient temperature during the measurement at Totara Valley, which can be supported with the Arrhenius equation. It was furthermore measured that the power loss due to hydrogen diffusion through the pipeline walls during the fuel cell operation is about 1.5 W at the current system operation mode. A techno-economic analysis of the system was undertaken applying the micro-power optimisation software HOMER as a simulation tool. Two operation modes of the system were investigated, the load following and the peak demand compensating. The simulation results reveal that the durability and the cost of the electrochemical energy conversion devices; electrolyser and fuel cell, are the main hurdles which need to be overcome on the path in introducing hydrogen based energy systems like HyLink. Finally, economic optimisation modelling of the small-scale system by best component alignment was performed. It was found that the electrolyser capacity down-rating of 80% in relation to the wind turbine capacity, leads to a minimal system levelised cost. In addition to this, the impact of various wind turbine/electrolyser subsystems and pipeline storage capacities on the fuel cell capacity factor and on the system levelised cost in the load following operation mode was analysed. The outcomes can be useful for further HyLink related energy system planning.