ARTIFICIAL NEURAL NETWORKS FOR CONTROL AND MODELLING OF AN UNMANNED UNDERWATER VEHICLE

Due to their highly non-linear hydrodynamics and the unknown environmental conditions in which they operate, the control of Unmanned Underwater Vehicles (UUVs) poses serious difficulties for most classical design methods. This thesis investigates the use of Artificial Neural Networks (ANNs) when applied to the modelling and control of a UUV whilst following a varying seabed terrain and at differing surge velocities. Different control procedures are examined and their relative merits discussed in relation to the problem. The results of using an ANN to model the depth dynamics of the UUV at a single operating point and using this network model to train an ANN controller by use of Error Backpropagation are presented. In addition, a different control strategy is investigated, whereby, an ANN controller is trained by using the full mathematical model of the UUV and linear transfer function representations of its depth dynamics at specific operating points. The relative performances of using a feedforward ANN controller and a recurrent ANN controller are compared over different profiles as well as contrasting the relative merits of using Error Backpropagation, Chemotaxis and Alopex, as applied to the controller training task. In addition, the robustness of the optimum controller in the presence of disturbances and missions over unfamiliar terrain and at varying surge velocities are considered.The Royal Naval Engineering Colleg

Development of a Rockoon Launch Platform and a Sulfur Fuel Pulsed Plasma Thruster CubeSAT

Amateur rocket launches are unable to reach heights much above 30 km due to the high drag of the dense lower atmosphere. Using a balloon to rise to an altitude of 30 km before launching is one means to increase a rockets range. An overview of the concept and a summary of the launch history for the University of Washington rockoon (rocket / balloon) program are given. Such a system will be capable of providing an inexpensive and reduced complexity launch method for student projects. Additionally, the university has recently opened a CubeSAT laboratory to give students hands-on experience with satellite hardware. Once in orbit, CubeSAT missions are limited, in part, due to an inability of low power thrusters to offset atmospheric drag. Recent results show that a coaxial sulfur-fuel Pulsed Plasma Thruster can provide a impulse/energy ratio of 20 mN/kW from a 10 J discharge, double of what a similar geometry Teflon variant is capable of. This increase in performance can provide CubeSATs the propulsion necessary for station-keeping in orbit. With launches planned over the next five years, the University of Washington aims to launch a 3U CubeSAT from a rockoon on a suborbital flight as a student project