Nonlinear control of autonomous underwater vehicle in shallow water environment
observer is proved to be globally asymptotically stable (GAS). Simulations are conducted to demonstrate the performance of proposed observers. With these observer designs, we can derive different output feedback controller for various mission requirements. • Station keeping controller designs: The mission of station keeping is to maintain the position of an AUV at a fixed point in shallow water environments by counteracting external wave disturbances. Based on some separation principle and
... principle and observer backstepping techniques, two output feedback controllers are developed, respectively. The nonlinear output feedback controllers are shown to maintain the AUV at a fixed position by effectively counteracting high frequency wave disturbance. The stability of the proposed observers are proven by using Lyapunov stability analysis. Simulation results of a representable AUV show that the output feedback controller indeed performs well with good stability and robustness properties. With these designed approaches, AUVs can be used for Mine Countermeasures (MCM) for force protection and counter-terrorism with precision requirement. iii • Dynamic positioning controller design: An energy efficient control strategy for AUVs operating at low speed motion in shallow water environment is formulated and an observer backstepping controller is designed to maintain AUVs at a position without counteracting the wave disturbances. Also using the Lyapunov stability analysis, the GES of the whole observer-controller system is proven. Case study and simulation results are presented to show the performance of the output feedback controller. • Trajectory tracking controller design: An output feedback controller for trajectory tracking for high speed AUVs in shallow water area concerning the energy efficiency problem is developed. The global exponential stability (GES) of the observer-controller system is proved by Lyapunov stability theory. Simulation results are also presented to demonstrate the performance of the proposed controller.