Zhang Honghan

Mission and motion control of AUV for terrain survey mission using discrete event system theory

This paper presents the mission and motion control method of an Autonomous Underwater Vehicle (AUV) for ocean terrain survey. The motion modes of AUV in the terrain survey mission are analyzed and defined, including: way-point tracking motion and trajectory tracking motion. For terrain survey mission, AUV needs to track a series of points and paths in horizontal plane and keeps depth in vertical plane. The motion control of AUV in the two motion modes are introduced briefly. Because of series of paths in terrain survey mission for AUV to track, so, there must be a mission control as path changed. When AUV sails from one path to another path or from one point to another point, its state is changed which may be cause poor tracking result. In order to keep optimal terrain survey task, this paper proposes a mission control method using discrete event system (DES) theory by treating the path change as an event transition. Petri net (PN) formalism is used to model and describe the whole mission, specially, when the path changes. At last, simulations in normal and degraded situations are established to verify the method mentioned above. The simulation results indicate that the method is feasibility and effectiveness for AUV.

Research on depth control based on output disturbance observer for UUVs maneuvering near the surface

Frequent changes of depth caused by the ocean wave generate lots of problems in the motion control of Unmanned Underwater Vehicles (UUVs) when operated near the surface, such as wear and tear of the motors, consumption of energy and so on. In order to solve these problems, this paper have tried to eliminate the disturbance of depth signal through estimating it according to nonlinear output disturbance observer based on the model of ocean wave. Then the stability of the observer was proved by Lyapunov theory. At last, the observer was implemented in the simulation of the depth control system and the results show the effectiveness and practical significance of the method.