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<p>Design and analysis of multiple input autopilots using sliding modes in order to achieve accurate horizontal and vertical plane control of an autonomous underwater vehicle over a wide variation of speeds is presented. The simulated vehicle is equipped with two (fore and aft) sets of dive planes and two sets of rudders. In addition, two vertical and two horizontal thrusters are provided for control during low speed or hovering operations. The entire range of vehicle speeds from zero speed hovering to full speed ahead is divided into regions depending on control efficiency. Thrusters are used for low speed hovering, control surfaces for transition speeds. Linear quadratic regulator optimal control techniques coupled with the robustness properties of sliding mode control are utilized to provide the necessary control reversal which occurs during the transition from cruise to hover mode. Constant disturbances arising from underwater currents are effectively compensated resulting in accurate path keeping. As a consequence of the multiple input control methodology developed in this work, it is shown that both path and orientation accuracy can be achieved in moderate cross current environments. Finally, reduced order observers are designed in order to account for sensor absence or malfunction.
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<br>Subjects: Mechanical engineering; Marine engineering.; Autonomous Underwater Vehicles; AUV; Guidance Control</div>
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Hawkinson, Todd D.</div>
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