Research On UUV's Security Assessment Of Terrain Following And Navigation Mode Switching Control Method

Unmanned Underwater Vehicle(UUV)is a small-scale underwater carrier with a variety of high-tech involving disciplines such as Automation Technology,Computer Technology,Underwater Acoustic Technology,etc.it can execute underwater tasks by remote control or autonomous operation.UUV has very high application value in military,scientific investigation and civil domain,can execute many kinds of tasks such as underwater warfare,reconnaissance,submarine resource development,wreck salvage,etc.UUV's movement control technology is the basis of its realization of functions,and movement control technology in vertical plane is a special problem because UUV and submarine's movement in space is very different from other vehicles.This problem has great research value.UUV needs to sail at a set high following the terrain to perform tasks such as underwater pipe laying,topographic mapping,etc.Underwater terrain is complex and changeable,when UUV is doing terrain following navigation,some steep or slope-drastically-changed terrain will pose a threat to it.UUV's safety of navigation is the prerequisite for performing tasks,so there is much significance in research of UUV's safety of navigation.This paper proposes an switching control method of UUV navigation mode,it can evaluate UUV's safety of navigation and make UUV switch its status of navigation to control of fixed depth when the terrain becomes dangerous for terrain following UUV.When it becomes safe,UUV switches to terrain following status and continues execute tasks.This makes UUV's safety of navigation guaranteed.The specific research contents are as follows:First,this paper builds a fixed coordinate,a carrier's coordinate and the transformation relation between them.On this basis,UUV's kinematics model and dynamic model of 6-dof is built.According to the needs of the subject,the models are decoupled and simplified,and then a simplified model of UUV on vertical plane is gained.Second,this paper studies UUV's depth control based on its simplified model on vertical plane,designs a depth controller based on feedback gain back-stepping theory and analysis system's robustness.The control effect of the controller is verified by simulation on MATLAB.Third,this paper studies UUV's terrain following control,simply describes heavy anddifficult points in it.This paper deducts Serret-Frenet equation,and then obtains the model of UUV's terrain following error on the basis of it.UUV's terrain following guidance law and controller are designed and verified by simulation on MATLAB.Finally,this paper simply analyzed dangers UUV might encounter in different situations,and then uses fuzzy membership function to describe indexes of UUV's safety of navigation quantitatively.On this basis,the paper assesses UUV's safety of navigation and describes it quantitatively as a coefficient.Based on UUV's depth controller and terrain following controller,the paper brings up the switching controller of UUV navigation mode,and then verifies it by simulation on MATLAB.