Research On Anti-disturbance Control And Fault-Tolerant Controe For Remotely Operated Vehicie

Remotely operated vehicles,as important tools for the development of marine resources,is highly valued for their advantages such as high efficiency,safety,and suitability for various environments.However,the underwater environment is complex and changeable,which brings challenges for the control of vehicles.As a result,developing efficient,accurate and stable control methods for the remotely operated vehicle with unknown disturbance and thrusters fails becomes current research hotspots.This thesis aims to develop a control method for a lightweight remotely operated vehicle with six degrees of freedom.To address the challenge of unknown disturbances,we have designed a nonlinear disturbance observation-based linear quadratic tracker for the vehicle.Additionally,we have considered the control problem arising from thruster failure and have developed a multi-model switching control method to address this scenario.This article first analyzed the underwater working environment of ROV,established its kinematic and dynamic models,and conducted a theoretical analysis of the propulsion system model.With the developed nonlinear mathematical model,we use the first-order Taylor expansion to linearize the model,which provide a foundation for the subsequent control method design.This article analyzed the disturbances encountered by the remotely operated vehicle during underwater motion and found that the disturbances are nonlinear and slow time-varying.Therefore,we designed a nonlinear disturbance observer to estimate the unknown disturbance.The estimated disturbance is regarded as the true value in the derivation of the linear quadratic tracker based anti-disturbance control law.Simulation results indicate that this approach can effectively mitigate disturbances from the external environment.This article analyzed the motion characteristics of the remotely operated vehicle under various thruster failure scenarios,and established corresponding mathematical models and control laws for these scenarios.We designed a motion characteristics based switching algorithm to automatically locate which thruster is failed.The switching algorithm is integrated into the multiple model control method and the simulation results demonstrate the effectiveness of this approach in maintaining stable control of the underwater vehicle when thruster failed.Finally,This article built a remote-controlled unmanned underwater vehicle experimental platform to evaluate the effectiveness of our proposed control method.The experiment that conducted on this platform results show that the nonlinear disturbance observer based linear quadratic tracker and motion characteristics based multiple model switching control worked well in practical environments and demonstrated that our control method improve the stability of ROV.