Research On Fixed Depth Motion Control Of Towed Underwater Vehicle

The towed underwater vehicle(TUV)is connected to the towed ship by a towed cable with signal and energy transmission functions.Compared with the traditional autonomous underwater vehicle,it has the advantages of unlimited range,good depth stability and high reliability.It has a broad application prospect in the civil field of underwater resources development and utilization,deep-sea scientific exploration,as well as the national defense field of territorial sea prevention and control.Because the working environment of TUV is complex and changeable,and the traction force is difficult to control because of the change of sea condition,the whole motion system has the characteristics of time-varying,nonlinear and coupling between towed ship and cable and underwater vehicle,so the mechanism modeling and analysis is very difficult,so the depth control is difficult to realize accurately,which makes the TUV not widely used.In view of the above reasons,this thesis takes the TUV as the research object,aiming at the problems of its motion system modeling,solution and depth determination.Then,the solution method for the whole system model is proposed,and the auto disturbance rejection and depth determination motion control strategy is optimized based on the immune genetic algorithm(IGA).The simulation model is built on the MATLAB simulation platform,and the experimental analysis is carried out to verify the feasibility of the model analysis solution and control method.The main contents of this paper are as follows:(1)The basic composition of the TUV system is introduced,and the relevant conversion relationship between the towed cable and the underwater vehicle in their respective motion coordinate system is analyzed.The mathematical model of the TUV motion system is derived by combining the stress analysis,and the vertical plane motion mathematical model of the system is further derived based on this.At the same time,the whole mathematical model of the system is solved by finite difference method;(2)Currently,the fixed depth motion control of TUV generally has the problem of low accuracy.The depth motion controller based on ADRC is designed and the parameter optimization of ADRC is analyzed.Through the parameter optimization analysis experiment and dynamic experiment verification,the controller can suppress the depth overshoot of the vehicle well,and the wing motion amplitude of the vehicle is small.The optimal combination of ADRC parameters is the key to improve the performance of ADRC;(3)There are many ADRC parameters,manual adjustment is difficult,and some parameters are coordinated.According to the characteristics of genetic algorithm,such as simple coding and genetic operation,unrestricted optimization,strong parallel and global search ability,it is used in ADRC parameter tuning.Because genetic algorithm is easy to fall into local minimum value and premature,so immune algorithm and genetic algorithm are combined to optimize ADRC.The dynamic experiments show that the local convergence and global convergence of the optimization process index,as well as the depth overshoot and depth fluctuation amplitude of the optimized controller performance index,ensure the better optimization effect of IGA;(4)The model reliability of the TUV and the performance of the fixed-depth controller are comprehensively and systematically verified.The steady-state motion of the TUV is simulated,and its influence on system depth and tension is analyzed experimentally from three aspects of towing speed,towing cable density and towing cable resistance coefficient,so as to verify the reliability of the model.From two aspects of deep-water navigation and near-surface navigation,the deep-setting motion of the TUV was simulated in multiple working conditions,and the performance of the designed three controllers(PI,ADRC and ADRC optimized by IGA)was verified by experiments.The experimental results verify that the working characteristics of the model of the TUV system established in this thesis are consistent with the reality,and the target that the maximum dynamic deviation of the depth,the amplitude of the depth fluctuation and the amplitude of the wing motion are smaller when the ADRC optimized by IGA is used to carry out multi-mode depth setting motion;The purpose of this thesis is to use some new algorithms and theories to design the controller of the TUV motion system,so as to make the dynamic control system of the wing motion amplitude,depth fluctuation amplitude and other better dynamic characteristic parameters of the vehicle,so as to meet the functional requirements of people.