Aimed at the problems of motion planning for autonomous underwater vehicle（AUV） in unknown environment

a behavior-based approach of obstacle avoidance and goal approaching is raised.Behavior dynamics is applied to design the goal approaching module and obstacle avoidance module.Using the macro behavior

behavior modules in the horizontal plane are fused.As to the behavior design in the vertical plane

fuzzy theory is applied to construct the fuzzy membership function for the input "depth" and "height"

to establish the reasoning rules obtaining the referenced depth from the input sailing depth and the height to the bottom and further to get a practical exact referenced depth by fuzzification.Simulation results show that the behavioral model has a better correct and effective response to the external environment

and is helpful to improve the adaptability of AUV to the environment.