Design and simulation of fuzzy inference based multiple PID controllers for 6-dof unmanned underwatter vehicle

Abstract

Unmanned underwater vehicles are currently being utilised for scientific, commercial and military underwater applications. These vehicles require autonomous guidance and control systems in order to perform underwater tasks. Modelling, simulation and control ofthese vehicles are still major active areas ofresearch and development. This thesis explores the design of a control system for a 6-Dof unmanned underwater vehicle. The thesis consists oftwo phases; the first involves the design ofthree single decoupled PID controllers for surge, yaw and depth. Then it is shown that it is not possible to cover the entire range of operations of UUV using only single controller by simulation using MATLAB SIMULINK. The second phase is concerned with the design ofmultiple PID controllers covering the entire range of UUV operation, as well as the fuzzy inference based supervisor design to switch between the different controllers as the operations conditions vary. The design ofthe PID controllers are based on MATLAB PID tuning algorithms which is a robust response time tuning algorithms that allows for faster design process with robust gain values. It is shown that these new tuning methods as well as graphical tuning interface overcome the adhoc and time consuming process offinding the PID gains. Further it is shown that fuzzy gain scheduling using fuzzy inference mechanism is a valid method for controlling a UUV with nonlinear dynamics. It can be concluded that new tools such as MATLAB tuning algorithms and Fuzzy toolbox allows for fast and accurate design of controllers for highly complex systems as well as the viability offuzzy inference multiple controllers as a method for UUV control with desired response characteristics. Finally the author recommends an actual vehicle implementation and testing as future work to be carried out.