Performance analysis and simulation of an autonomous underwater vehicle equipped with the collective and cyclic pitch propeller

There is a growing need within marine sciences and engineering that requires the torpedo shaped Autonomous Underwater Vehicles (AUVs) being capable of accomplishing various complex surveillance missions, including scientific, commercial and military applications. Be-sides the traditional research on the control and navigation of an AUV, the propulsion system study becomes more and more essential to increase the manoeuvrability and efficiency of AUV. The conventional propulsion system with fixed pitch propeller (FPP) and control surfaces at the aft end is the predominant propulsion type used by AUVs. This propulsion configuration has the shortcoming of insufficient low-speed manoeuvrability since the control surface manoeuvring forces are only generated when the vehicle is in motion. This is one of the fundamental limiting factors for the current torpedo shaped AUVs. The development of new propulsion system enabling both low speed and cruising speed operations could expand the typ-ical operational envelope of an underwater vehicle and pave the way for the new applications. This thesis focuses on the characteristic analysis of an innovative propulsion system called the Collective and Cyclic Pitch Propeller (CCPP) and the manoeuvring performance of an AUV equipped with CCPP. In the CCPP mechanism, the angles of each propeller blade can be positioned periodically during a rotation in both collective and cyclic pitch setting. CCPP has the capability to provide continuous propulsive force and manoeuvring forces simultaneously. The primary task of the thesis was to explore the feasibility of a prototype CCPP to an under-water vehicle by numerically conducting the comparison between the AUV equipped with CCPP and FPP in standard manoeuvring tests. Initially, the Experimental Fluid Mechanics approach was utilised to investigate the performance and derive the mathematical models of the CCPP and FPP. Two separate experimental apparatus were designed and implemented in this research for CCPP and FPP system. In the first experiment, the dynamic modelling of FPP using the four-quadrant model was proposed based on experimental data. The second exper-imental study involved the extensive investigation of the CCPP to establish its hydrodynamic characteristics. A series of comprehensive bollard pull and captive model tests were designed and conducted to evaluate the propulsion performance. Furthermore, the research developed a numerical simulation program called AUVSIPRO to examine the performance and manoeuvring characteristics of an AUV equipped with the CCPP as well as conventional configuration FPP. The Gavia AUV was used as the research platform and its mathematical model with non-linear hydrodynamic coefficients were defined using the theoretical approach. Standard manoeuvring tests of marine vehicles were fully presented in the simulation program to analyse the manoeuvrability. In addition, the results from the experiments and simulation were utilised in the comparison study between the CCPP and conventional configuration applied to AUV. Finally, the controller design for an AUV equipped with a CCPP was conducted. The two-stage system identification method was proposed to develop the linear system model, which was applicable for the control design. The optimal state feedback algorithm was presented as the control strategy. The propulsion systems for AUV have been subject to an increased focus with respect performance and manoeuvrability. This research is an exploration into the feasibility and viability of CCPP propulsion system for a torpedo shaped AUV and contributes to the areas related to the development of propulsion system for an underwater vehicle.