Design And Research Of Unmanned Surface Vehicle Path Following Control System

Unmanned Surface Vehicle(USV)plays an increasingly important role in the military and civil fields related to the ocean,and path following control is also a key technology to realize the precise navigation of USV according to the given desired path.Therefore,it is of great significance to research the path following control system for improving the level of intelligence and autonomy of USV.When USV travels in complex ocean conditions,it will be influenced by environmental factors such as wind,wave and current,and USV itself has the characteristics of underactuated,so it is very challenging to design the path following control system with high following accuracy,fast response speed and strong anti-interference capacity.In the design and research of USV path following control system,there are two problems that need to be solved: the control of heading and the design of guidance strategy of USV.In the presence of external interferences such as wind,wave and current,an improved Integral Line-ofSight(ILOS)guidance strategy is firstly proposed,which calculates the desired heading angle according to the given desired path,and then an ADRC heading controller based on the Improved Grey Wolf Optimization(IGWO)algorithm is proposed,which make the actual heading angle track the desired heading angle,so as to realize the path following control of USV.The main works of this thesis are:Firstly,the background and significance of design and research of USV path following control system are expounded,and the research actuality of USV,grey wolf optimization algorithm,heading control and path following control at home and abroad are summarized in this thesis.Afterwards,USV is regarded as a dynamic system,and the USV three-degree-of-freedom horizontal motion model and the responsive steering model are established by adopting the method of mechanism modeling.Finally,considering the influence of environmental factors on USV navigation,the interference mathematical models of wind,wave and current are established,which lay a theoretical foundation for the control of heading and the design of guidance strategy.In the control of USV heading,considering the advantages and disadvantages and improvement measures of classical PID control,an ADRC heading controller based on the IGWO algorithm is proposed.First according to the USV steering model,the second-order nonlinear Active Disturbance Rejection Control(ADRC)is used to control the heading angle.Then in order to reduce the complexity of ADRC parameter tuning,the IGWO algorithm is proposed.The Dimension Learning-Based Hunting(DLH)search strategy which associated with selection and update steps is adopted in the algorithm.By solving the benchmark function,it is verified that compared with the GWO algorithm,PSO-GWO algorithm,CGWO algorithm and HGWO algorithm,the IGWO algorithm has stronger exploration and development capacity,it can effectively get rid of the local optimal solution,and has better optimization effect.The MATLAB simulation is carried out in the absence of external interferences and in the presence of wind and wave interferences.It is indicated by the result that the ADRC heading controller based on the IGWO algorithm can meet the requirements of high-precision heading control,with fast response speed and strong anti-interference ability.In the design of USV guidance strategy,considering the influence of the timevarying drift angle caused by external interferences on the performance of the path following control system,an improved ILOS guidance strategy is proposed.Firstly,the integral term is added to form the ILOS guidance strategy on the basis of the traditional LOS guidance strategy.Secondly,the forward looking distance is selected as a function of the speed and lateral tracking error.Finally,the drift angle is estimated and compensated by combining the dimensionality reduction state observer.The Lyapunov stability theorem is used to prove that the guidance subsystem is uniformly asymptotically stable.Given the desired straight path and curve path,the MATLAB simulation is carried out in the presence of wind and wave interferences.It is indicated by the result that the path following control system based on the improved ILOS guidance strategy has faster following speed,higher following accuracy and stronger anti-interference than the path following control system based on the LOS guidance strategy and ILOS guidance strategy.