Research On Homing Technology Of Unmanned Underwater Vehicles Based On Forward-looking Sonar

With the growing demand for marine resources and the rapid development of imaging sonar technology,the use of imaging sonar for underwater target detection and recognition has become a focus in the world.Unmanned and autonomous technology is an important direction of development of minehunting equipment,and homing technology of unmanned underwater vehicles is a key technology for autonomous minehunting.Therefore,the research on homing technology of unmanned underwater vehicles is imminent.This paper used forward-looking sonar to explore homing technology of unmanned underwater vehicles,homing of unmanned underwater vehicles can be divided into three parts: image preprocessing,target detection and recognition,homing control of vehicles.The main contents and methods of this paper are as follows:Firstly,the operation mode and imaging principle of forward-looking sonars were expounded.Sonar images and visible images were contrasted.The statistical characteristics of sonar images and the characteristics of targets in forward-looking sonar images were analyzed and summarized.Secondly,the image preprocessing method for forward-looking sonar images was studied.The image segmentation was performed by the piecewise linear gray level transformation.Filtering method which is commonly used for engineering applications was analyzed by the filter evaluation function,and then median filter was selected.Thirdly,a further research on the underwater targets detection and recognition was proposed,which is the difficult point.According to the characteristics of forward-looking sonar system,a method combined template matching and image sequence detection was proposed for multi-target detection.The weakness of traditional clustering-based image segmentation was analyzed,and Otsu method was improved.Invariant moments are chosen as recognition characteristics.Finally,the simulation of the homing control of the unmanned underwater vehicle were carried out.Based on the theory of homing,the components of the heading controller were analyzed and modeled.The mathematical model of the heading controller was designed,and the controller was built by Simulink,the heading control simulation was carried out under both the ideal state and the sea wave disturbance.The measured data processing and computer simulation results show that the proposed method has high underwater targets detection probability,and can meet the real-time requirement of engineering application.The designed heading control system has better control effect that can guide the unmanned underwater vehicle accurately.The results of this paper lay a good foundation for unmanned autonomous minehunting technology.