Research On Obstacle Avoidance Technology Of Semi-submersible Unmanned Vehicle

At present,the topic of maritime rights and interests is heating up all over the world,and the utilization of Marine resources has become an important indicator of a country ’s development.Intelligent unmanned craft,with its outstanding advantages of small size,good concealment and small casualties,has important application value in such fields as national defense,Marine physical environment monitoring,port security and intelligence gathering,and is the forefront of competition among international maritime powers.As a member of the large family of unmanned craft,semi-submersible unmanned craft has become a hot topic in China due to its unique navigation mode,its advantages of effectively reducing the impact and influence of the sea surface wave area and good invisibility.At present,there is still a certain gap between domestic and foreign research on semi-submersible unmanned boats,especially in the aspect of obstacle avoidance of semi-submersible unmanned boats,the research is still relatively few.In this paper,aiming at this problem,the obstacle avoidance function of self-developed semisubmersible unmanned boats is studied.The main contents are as follows:A digital representation method of obstacle signals is presented.When the semisubmersible unmanned craft is sailing,it is necessary to consider not only the influence of obstacles above the water surface on its safety,but also the obstacles below the water surface.In view of the above situation,infrared sensors are used for obstacle detection above the water surface,and ultrasonic sensors are used for obstacle detection below the water surface.In order to directly and quickly characterize the detection signals of semisubmersible unmanned vehicle sensors,the sensor signals were firstly fused with the relevant knowledge of signal fusion,and the specific rules of sensor signal fusion were proposed.Then the sensor signal is digitized.Finally,the detection signal of the sensor is characterized by two hexadecimal digits.An obstacle avoidance strategy for semi-submersible unmanned craft is proposed.According to the obstacles encountered by semi-submersible unmanned craft during navigation and in combination with the International Regulations for Preventing Collisions at Sea,four types of obstacles are defined,namely,encounter,pursuit,left crossing and right crossing.Then,according to the actual navigation condition of the semi-submersible unmanned craft,three obstacle avoidance scenarios are defined: no obstacle,single obstacle and multiple obstacles.Finally,according to the above four encounter types and three obstacle avoidance scenarios,obstacle avoidance strategies are given for each case.In order to ensure the fast and stable tracking reference trajectory of semisubmersible unmanned vehicle,a trajectory tracking control method based on MPC is proposed.Firstly,the motion model of the new semi-submersible unmanned vehicle was established,and then the MPC objective function and system constraints were constructed based on the actual parameters.Finally,the trajectory tracking problem of semisubmersible unmanned vehicle was transformed into the optimal value problem.The control algorithm is analyzed by simulation software.The simulation results show that the trajectory tracking control method based on MPC can guarantee the fast and stable tracking of reference trajectory of semi-submersible unmanned craft.Design and implementation of obstacle avoidance control system for semisubmersible unmanned craft.In this paper,STM32F103ZET6 is adopted as the main control chip of the obstacle avoidance control system,which is combined with the power module,obstacle detection module,motor drive module,electronic compass module and other auxiliary devices to form the obstacle avoidance control system of semisubmersible unmanned vehicle to achieve the obstacle avoidance function.Finally,the obstacle avoidance control system is tested and verified.The results show that the obstacle avoidance control system is stable and reliable,and the obstacle avoidance strategy is safe and feasible.After theoretical research and experimental verification,the obstacle avoidance system proposed in this paper can achieve the obstacle avoidance function of semi-submersible unmanned vehicle,which has certain reference significance for future research on obstacle avoidance control of semi-submersible unmanned vehicle.