Modeling And Adaptive Sliding Mode Control Of Autonomous Underwater Vehicle

The continual development of computer technology has enabled the expansion of advanced control into the field of autonomous underwater vehicles (AUVs), where potential uses include oceanographic research, environmental monitoring and military mine countermeasures. In this dissertation, through computer simulation, the problems of modeling, control and guidance of AUVs are presented.The first part of this dissertation addresses the problem of dynamically modeling of AUVs, and derives thrusters' two-dimension nonlinear dynamic model, which has axial flow speed and propeller rotational velocity as two state variables, voltage or current of motor as inputs, and thruster force and torque as output.The second part focuses on the nonlinear adaptive sliding mode control of AUVs in diving plane and steering plane. The requirement for having a simple controller which performs satisfactorily in the presence of dynamical uncertainties calls for a design using the sliding mode approach. In this controller, online parameters estimating algorithm is added to classical sliding mode controller to achieve both robustness and adaptability, to prevent noise and disturbances from causing parameter drift, a dead-zone is added to shut adaptation off for small tracking errors, and the adaptation law is modified to guarantee the estimated parameters in previously known ranges.The third part is devoted to the problem of speed/position's tracking control using sliding mode control approach. A cascaded architecture is adopted, where desired propeller rate of revolution is generated by solving a static 2nd order equation with a parameter of desired thrust force, which is the input of the speed/position tracking control.In the last part, depth schedule strategy based on fuzzy inference system (FIS), and line-of-sight guidance in horizontal plane in the presence of unknown current are studied.