Research And Implementation Of Path Tracking System For Unmanned Surface Vessels

Unmanned surface vessel is a surface ship capable of navigating,controlling and completing tasks independently.Compared with the traditional ships,USV has the characteristics of small volume,unmanned,quick reaction,flexible concealment,and strong endurance,so it is widely used in monitoring and rescue of natural disasters,hydrology monitoring in the disputed sea areas,the exploration of marine resources,and the construction of unmanned war platform.The core technology of USV lies in its autonomy,which is mainly embodied in two aspects: USV has independent planning ability,can plan a reasonable route according to the task and operation environment,and can adjust the route dynamically according to the danger and obstacle;it helps realize path tracking control and enables USV to track autonomous planning paths.This paper aims at the design and implementation of the path tracking control system for USV.The modeling method,path tracking control algorithm,hardware platform design and implementation are studied.The specific research contents are as follows:1.The modeling method of unmanned surface vessel is studied.Based on the analysis of gravity,buoyancy,hydrodynamic forces and thrust of propellers on USV,a dynamic model of USV is constructed on the basis of the momentum theorem and the momentum moment theorem of the rigid body.According to the actual operation situation,the model is simplified reasonably,and the two order linear K-T equation is constructed.2.A path tracking control method based on line of sight guidance(LOS)and PID heading controller is proposed in order to solve the problem of USV’s path tracking control.Aiming at parameter determination of PID heading controller,we use the mode that setting the initial values off-line and dynamically adjusting on-line.The initial values of off-line setting make the controller enter the better control state quickly.The on-line dynamic adjustment makes the controller adapt to the modeling error,the model nonlinearity and the dynamic interference.The PID parameters are adjusted off-line by multi population genetic algorithm(MPGA).This method solves the problem that traditional genetic algorithm is prone to fall into local optimal,and enhances the global optimization ability of the algorithm.A fuzzy method is used to realize the dynamic adjustment of the PID control parameters.The fuzzy method takes the heading difference and the change rate as the input,adjusts the PID control parameters according to the fuzzy rule,and enhances the adaptability of the controller.For the problem of overadjustment of the fuzzy adaptive PID method,improvement measures are taken to improve the continuous tracking ability of the controller according to the dynamic adjustment of the error and its change rate.3.The design and implementation of hardware and software for USV’s path tracking control system is completed.It mainly completes the circuit design and software programming of the core board,including power supply module which is used for power supply and management of the whole system,D/A module which is used for the control of propeller,serial communication which is used to realize the data interaction between the sensor and the communication equipment,serial port expansion which is used to solve the problem of insufficient serial communication resources in F28335 chips,and SD card storage which is used to store critical data at runtime.Based on the core board,the whole program structure of USV and the upper computer is designed and implemented.4.The path tracking control algorithm is simulated,and the hardware circuit and program of the design are partially verified by experiments.The simulation results show that the PID controller set by MPGA has fast responing speed,no overshoot and no steady-state error.The improved fuzzy adaptive PID algorithm enhances the stability of the controller.The path tracking control algorithm designed can track the straight line path when the sensor is in error,and filtering the sensor data can help improve the stability of the track control system.The experimental results show that the designed circuit and program can work normally.