Mars Spacecraft Power System Development Final Report

Development of optimum Mariner spacecraft power system for application to future flyby and orbiter mission

Modeling and Analysis of Power Processing Systems

The feasibility of formulating a methodology for the modeling and analysis of aerospace electrical power processing systems is investigated. It is shown that a digital computer may be used in an interactive mode for the design, modeling, analysis, and comparison of power processing systems

Fault studies on synchronous generators with rectifier excitation

Imperial Users onl

New Approaches in Automation and Robotics

The book New Approaches in Automation and Robotics offers in 22 chapters a collection of recent developments in automation, robotics as well as control theory. It is dedicated to researchers in science and industry, students, and practicing engineers, who wish to update and enhance their knowledge on modern methods and innovative applications. The authors and editor of this book wish to motivate people, especially under-graduate students, to get involved with the interesting field of robotics and mechatronics. We hope that the ideas and concepts presented in this book are useful for your own work and could contribute to problem solving in similar applications as well. It is clear, however, that the wide area of automation and robotics can only be highlighted at several spots but not completely covered by a single book

Characterisation and Design of Novel Non-Foster Circuits for Electrically Small Antennas

PhDThere is a demand for broadband electrically small antennas that cover large frequency bands without any requirement of reconfiguration techniques. This is particularly true at low frequencies (VHF/UHF), where wavelengths are long and antennas are physically large. The fundamental gain-bandwidth limitation was related to the electrical size of passive electrically small antennas by Wheeler and Chu; their result implied that an electrically small antenna exhibits high quality factor which limits the bandwidth. Additionally, the gain-bandwidth limitation was related to impedance matching conditions by the Bode-Fano criteria, which restricts available bandwidth using conventional reactive elements. A non-Foster circuit approach has been presented which delivers a broadband input impedance match and also overcomes the aforementioned fundamental limits. These non-Foster impedance circuits can be realised by negative impedance converters (negative inductance and/or capacitance). The thesis also explores the advantages and challenges of antenna impedance matching using negative impedance circuits based on two topologies: (1) conventional transistorbased circuits, and (2) a novel resonant tunnelling diode approach. The advantages of non-Foster circuits in the implementation of broadband small antennas include wideband performance around one-tenth of the self-resonant frequency and overcoming of the fundamental limits associated with passive antennas. Diode-based circuits are more compact, easily configurable, less sensitive to stability, have low power consumption and are less complex as compared to the transistor based designs. These features makes it a potential candidate for array and meta-material applications. However, there are few challenges for non-Foster circuit integration with an antenna due to high noise figure, which affects the system channel capacity and receiver performance in a communication system. A detailed design procedure has been developed to mitigate the effects of noise and instability and also, the system performance and measurement of the non-Foster circuit integrated antennas have been discussed

Evaluation of two prototype three phase photovoltaic water pumping systems

Bibliography: p. 221-223.Two prototype three phase AC photovoltaic pump systems (Solvo, ML T) and a DC PV pump (Miltek) were tested on a farm borehole in Namibia (latitude 21°6', longitude 17°6'). The PV array consisted of twelve modules (636Wpeak) mounted on a single-axis passive tracker. The depth of the water was 75m and a progressive cavity pump with a self-compensating stator was used in all the tests. Customised data acquisition was designed to measure performance characteristics through a range of operating conditions (mainly steady state); a secondary data acquisition system was used to capture samples of high frequency signals. The data allowed detailed analysis of system, subsystem and component performance, as well as performance evaluation over Standard Solar Days. The focus of the investigation was evaluation of the AC prototypes, in terms of performance, other technical factors, reliability and economic criteria. The analog-based DC system served as a basis for comparison. Both AC systems employed microprocessor control and PWM variable-frequency variable-voltage inversion. Efficiencies, optimality, stability, start-up behaviour, non-productive operating modes and protection were examined. A number of recommendations were proposed for improvements in the basic control algorithms, monitoring and managing non-productive modes, improved protection, layout and user diagnostic features