Design of Adaptive Controllers for Autonomous Underwater Vehicle

Abstract

Autonomous Underwater Vehicle(AUV) has been becoming much popular in recent years. Lot of research work has been going on in developing AUV for a wide range of applications. AUV has been utilised in detecting the leakages in oil/gas pipe lines which were laid under the sea. AUV can search for different type of elements present under the sea. AUV is able to examine the life of plants and different organisms under the sea. AUV is self-propelled vehicle.
The thesis develops mathematical model for AUV. Thesis discusses the derivation of Dynamics and Kinematics of AUV. Then open loop mode of operation of AUV has been carried out by providing the required inputs under proper and specific environmental conditions. Simulation results are obtained using MATLAB/Simulink. Results have been discussed.
AUV has six degree of freedom. Its Dynamics are highly nonlinear and coupled. Normal conventional controllers like PID controller can’t be used in such situation. There is an essence of special controller like adaptive controller.
Model Reference Adaptive Controller(MRAC) has been used in controlling the path following task of AUV. Model reference adaptive controller(MRAC) has been designed using Lyapunov’s stability theory approach. In this thesis, the controller has been designed using Lyapunov’s stability theory. This adaptive controller is designed in continuous time mode.
The same MRAC controller which has been designed in continuous time has been redesigned to get the accurate results in discrete time mode. Simulink model has been developed for model reference adaptive controller in discrete time. Results are obtained. The obtained results are being compared with that of MRAC in continuous time.
In order to get more accurate results for the path following of AUV there is an essence of design of another adaptive controller. And that controller has to be more robust and more accurate and has to decrease controller output signal effort when compared to the already designed MRAC controllers (both continuous time type and discrete time type). Fuzzy controller is capable of fulfilling the above mentioned criteria. Finally, another adaptive controller has been designed for the path following task of AUV which is Fuzzy controller.
The Simulink model has been developed for the path following task of AUV using fuzzy controller. The obtained results of fuzzy controller are compared with that of MRAC controllers.