A Method Of Nonlinear Observer And Output Feedback Control For UUV

In recent years,the great need of the development and utilization of marine resources and other urgent needs to explore the oceans,have greatly contributed to the underwater vehicle research and development.With the help of experienced technical staff,ROV,whose work scope is relatively small,can complete the task nearby the mother ship.At the same time,the cost of ROV is extremely high.But UUV,relatively inexpensive,can work independently off the mother ship in a certain range.Then UUV technology has been a hot and key research of underwater vehicle.We need to fully understand the UUV dynamic characteristics and design reasonable control method,both of which are very important for the UUV to improve their own ability.The complex marine environment and the high degree of nonlinearity of UUV model make the motion control method research for UUV particularly important.This paper mainly focuses on problem of lower control precision of the controller,which is caused by the current environment disturbance in the program of UUV movement.First,we establish the kinematics model of the research object,as the basis for following research.Then the nonlinear observer and the output feedback controller are proposed separately,and both of them are verified by simulation.First of all,based on the analysis of the rigid forces and moments,and hydrodynamic forces and moment,the UUV kinematics equations are established.After having analyzed the model of environmental force and current force,the UUV integrated system model is given and it will be the basis of the following observer and controller design.Secondly,a mathematical model of nonlinear observer is designed.As the small volume of UUV limits its carrying capacity,UUV may not fully obtain its pose information.At the same time,the underwater environment is complex and changeable,with many uncertain disturbances.Therefore,the motion states of UUV are difficult to be measured and the real-time control of the UUV is difficult to be realized.Through the combination of Lyapunov stability theorem and the genetic optimization algorithm of gain matrices,the nonlinear observer is designed.The observer can effectively estimate the UUV's motion states and the current speed by using the measurement information of UUV,and provide state estimations for the design of output feedback controller.Simulation results prove that the observer has good estimation performance.Thirdly,aiming at the problem of UUV trajectory tracking,on basis of the kinetic model of the UUV system,a sliding model controller based on constant velocity reaching law is designed.The nonlinear observer provides the UUV's motion states.The system is proved asymptotic stability through the Lyapunov stability proof.The simulations show that,in the condition of the accurate model,the designed controller has better control effect;whereas the change of model parameters will cause the system robustness reduce.Finally,based on the designed sliding model controller,utilizing the superior performance of LS-SVM,which can approximate any nonlinear function and effectively avoid the local optimal problems in neural network,the sliding model controller is improved and optimized.The adaptive sliding mode control law is obtained,after having the weight adjustment law of SVM through the Lyapunov stability proof.Meanwhile,the designed controller does not need the accurate model,and has a strong robustness and self adaptability for the model uncertainty and external disturbance.Simulation results show that the designed controller has good performance.