Tracking Control Of A Remotely Operated Underwater Vehicle With Time Delay And Actuator Saturation

In the process of exploring the ocean,due to the harsh underwater environment,humans cannot directly complete deep-sea tasks,so the underwater robot has increasingly been recognized due to their flexibility and autonomy.With the expansion of the application scope of underwater robots,the research on control strategies has gradually become an important subject in the application of underwater robot.The purpose of the tracking control system is to require the remotely operated vehicle to track the desired points according to the control instructions.At the same time,the accuracy and stability of its control system is improved during the tracking process.This will be provided important practical significance for developing underwater robot technology.However,it is challenging for the tracking control of underwater robot due to time-varying delay in cyber channels and actuator saturation in physical channels.Based on the above problems,this paper considers the constraints of communication channels and physical channels,and develops tracking control strategies for underwater robots.The main research works of this paper are as follows:(1)For the complexity of underwater environment,the time-varying delay in the communication channel is inevitable.Inspired by this,this research work takes the time-varying delay into consideration and a model-free controller is designed to enforce the position tracking.In order to improve the tracking performance of underwater robot,the Takagi-Sugeno(T-S)fuzzy rules are used to adjust the controller gain dynamically.(2)For the position tracking control problem of multiple autonomous underwater vehicles,considering the close coupling relationship between multi-level control subsystems and the influence of time delay in communication network,we design a distributed formation controller to stabilize the time-varying multi-ROV system.For the proposed controllers,Lyapunov-Krasovskii functions are constructed to analyze the stability,and then sufficient conditions for asymptotic stability are presented.(3)For the time-varying delay in cyber channels and actuator saturation in physical channels,a control strategy considering time delay and saturation constraints is proposedto ensure the stability of the control system.By defining multiple sets of intersected parallel surfaces,a new convex hull expression is proposed.Then in the space surrounded by multiple sets of parallel surfaces,the saturated function can be expressed as a convex combination of actual feedback and auxiliary feedback.According to the position error and velocities,delay-dependent stability conditions is established.By analyzing the stability conditions,the estimation of DOA is presented.Furthermore,the optimization of DOA is developed to maximize the estimation of DOA.