Research On Depth Control Of An Underactuated UUV With State Delay

The accurately control of the depth is very important to guarantee the research or military tasks,such as detecting and exploiting of marine resources,monitoring the ocean environment,mapping the seafloor.With the development of the intelligence,miniaturization and diversification of UUV,the control system has become more and more complexity.Based on the distributed control system of the Network Control System,the control systems structure design of UUV is the research direction at the present,which has the important significance on the control theory and the engineering application of the UUV.To overcome the state delay of the depth control system cased by the application of the NCSs,the further study will be carried out,and the suitable controller will be designed to make the depth control system achieve the better control performance.Firstly,the network communication structure of the lab UUV was described in detail,and combined the time-delay model of NCSs and the the six degree of freedom mathematical model of the under-actuated UUV,the mathematical model of the depth control system with the state delay was derived.Then the model of the ocean current disturbance was also analyzed.Secondly,to overcome the nonlinearity of UUV control systems,the Takagi-Sugeno(T-S)fuzzy method and NCS's model was combined to establish the fuzzy interval delay model of the depth control system,as T-S fuzzy model can approximate any smoothing nonlinear functions;Then by using the Parallel Distributed Compensation(PDC)designed the state feedback controller and through choosing the appropriate Lyapunov-Krasovskii function,the state feedback gains of each fuzzy rules were calculated to protect the stability in the format of Linear Matrix Inequality(LMI).Thirdly,to sove the depth control system for the underactuated UUV with the time-varying delay and the external disturbance,the adaptive sliding mode controller based on T-S fuzzy model was designed;By using T-S fuzzy model,the time-varying delay model of the depth control system was established to overcome the nonlinearity,the external disturbance;Then based on the thought of global sliding mode,a type of integral sliding surface was designed,and it was proved by a new Lyapunov-Krasovskii function with fuzzy weighing matrices;Furthermore,based on the adaptive control scheme,an adaptive sliding mode controller was designed to sove the unknown parameter of the external disturbances.Finally,to verify the stability of the state-feedback controller and the adaptive slidingmode controller,the numerical simulations based on MATLAB/Simulink were carried out;The following performance of the underactuated UUV was shown under the different time delay and the ocean current disturbances.Meantime the validity and correctness of the proposed methods were verified.