Research On Control For Manned Submersible Vehicles Based On Disturbance Characteristic Analysis

With the increasing development of marine resources,the manned submersible vehicle has gradually become an essential platform for deep-sea operations.In order to ensure that the manned submersible can perform various complex tasks accurately and safely,it is very important to design a high-precision robust controller.However,the operating environment of the manned submersibles is complex and uncertain.Its control performance can be affected by many factors,such as the highly nonlinear,time-varying dynamics of the submersibles themselves,tides in deep sea,and unpredictable external disturbances.Meanwhile,the thruster fault of the manned submersible may occur in the working process,which will lead to the submersible performance degradation and even safety accidents.Therefore,the main research content of this thesis is to realize the precise trajectory tracking control of the manned submersibles under multi-source disturbances,and to realize the fault tolerant control under the thruster faults.Aiming at the "JIAOLONG" manned submersible system affected by the model uncertainty and unknown external environment disturbances in the actual operation process,a trajectory tracking control method of the manned submersible based on the disturbance characteristic index of sign function is designed in this thesis to achieve accurate trajectory tracking.Then,in order to reduce chattering phenomenon and avoid overestimation of the control gain,a new adaptive sliding mode control method based on sector disturbance characteristic index is designed.On this basis,considering that the thruster fault may occur in the manned submersibles,the fault tolerant control is further studied.Different from the conventional active fault tolerant control method,the proposed fault tolerant control method is based on the disturbance characteristic index and thrust allocation,which can utilize the disturbance energy to compensate the thrust loss of the faulty thrusters.The main research and innovative contributions of this thesis are as follows:(1)Aiming at the problem that the manned submersibles are affected by the factors such as model uncertainty and unknown external environment disturbances,a trajectory tracking control method of the manned submersible based on the disturbance characteristic index of sign function is proposed.Firstly,in combination with Lyapunov theory,the relationship between the disturbances and system performance is analyzed,and the beneficial or detrimental effects of the disturbance on the system are judged.On this basis,the beneficial disturbances can be selectively used and the detrimental disturbances can be eliminated.Finally,through numerical simulation,it is verified that the proposed control method can improve the performance of the system by using beneficial disturbances.(2)Considering the chattering phenomenon caused by the sign function used in the above control method and the overestimation of the control gain in the conventional adaptive control methods,an adaptive sliding mode control method based on the sector disturbance characteristic index is proposed,such that the tracking error of the submersible system can converge to the neighborhood of the origin in a finite time.Compared with the sign function index,the sector disturbance characteristic index proposed in this method can effectively suppress chattering.The adaptive method can not only avoid the overestimation of the control gain,but also relax the requirement of uncertain boundary in the controller design.Finally,the superiority of the proposed adaptive sliding mode control method is verified by the numerical simulations.(3)Considering the manned submersible system with thruster fault,a fault tolerant control method based on the disturbance characteristic index and thrust allocation is proposed.This method can not only reduce the priority of faulty thrusters by means of thrust distribution,but also use beneficial disturbance energy to compensate the missing thrust of faulty allocation,so as to maintain the original control effect as far as possible and achieve the effect of energy saving.Through numerical simulation,it is shown that the proposed method still has good control effect when the thruster fault occurs in the manned submersible,and the control energy required is less than the conventional fault tolerant control method.