中文摘要：

由于所携带能源总量的限制，目前水下自航行器（Autonomous underwater vehicle，AUV）不能满足长时间海洋环境测量的要求。为了有效地减少能耗，解决AUV工作时间短的问题，提出一种具有变浮力系统、能够着陆坐底的小型AUV。该AUV通过着陆坐底实现定点测量，可以利用有限的能源实现长时间的海洋环境监测。基于此，对AUV的着陆策略进行研究。在对注水自由下沉着陆策略进行分析的基础上，分析水舱注水量与着陆速度、着陆时间以及着陆俯仰角的关系。最终选择控制注水着陆策略作为AUV的水下着陆方案，并基于模糊控制设计着陆控制器。该方法根据AUV距离海底的高度和俯仰角通过模糊推理来控制AUV水舱的注水量，可以使AUV以较短的时间着陆于海底，同时又将着陆速度和着陆俯仰角控制在很小的范围内，满足了AUV安全着陆的要求。仿真和水域试验结果证明了采用该着陆策略的可行性。

英文摘要：

The current autonomous underwater vehicle（AUV） cannot meet the requirement of long time ocean environment measurement owing to the limitation of the onboard electric power. In order to reduce the power consumption effectively to solve the problem of AUV＇s working time being too short, a small buoyancy changing AUV with the capacity of soft landing and bottom-sitting is developed. This AUV can realize the function of measuring at fixed point by landing and sitting on the seafloor, so it can carry out long time ocean environment measurement with the limited power. Based on this, the landing strategies of AUV are discussed. Based on the discussion of the landing strategy of free fall with water injection, the relationships between the landing velocity, landing time, landing pitch angle and the injected water volume are analyzed. Finally, the strategy of landing with controlled water injection is selected. Then landing controller based on fuzzy control is designed. In this method the injected water volume is adjusted by fuzzy inferences according to the distance to the seafloor and the pitch angle of AUV. This can guarantee that AUV will land on the seafioor in shorter time. At the same time, the landing velocity and the landing pitch angle can be kept in a very small range. This can meet the requirement for AUV to land on the seafloor safely. The feasibility of this strategy has been verified by the results of simulations and sea experiments.