The Control Method For The Roll Motion Of The AUV During The Diving Process

In the process of underwater vehicle dive from the surface,due to the disturbance of ocean environment such as waves and currents,its motion attitude will change significantly.The severe rolling motion will seriously affect the normal dive of underwater vehicle,and even destroy the structure of underwater vehicle.Therefore,it is necessary to control the rolling attitude of the underwater robot during its submergence.In order to study the rolling motion of underwater vehicle when it is disturbed by waves near the water surface,this paper takes the NPS AUV II underwater vehicle as the research object.It is a multi-wing autonomous underwater vehicle.The motion model of underwater vehicle in still water and the disturbance model of random waves are established respectively.Calculating the random wave disturbance force and disturbance moment of the underwater vehicle in low speed near the water surface,it is found that it is difficult to generate enough centralizing moment to reduce the disturbance of the random wave when the horizontal rudder of the underwater vehicle is controlled by the traditional roll reduction method.In order to solve this problem,this paper uses the working principle of the zero speed fin stabilizer to control the roll angle,uses the potential flow theory and the eddy force theory to analyze the lift force generated by the zero speed fin stabilizer.Based on the research of the zero speed fin stabilizer,a pair of horizontal rudders of the "NPS AUV II" underwater vehicle is considered to replace the zero speed fin stabilizer in order to achieve the purpose of roll reduction.Because of the non-linearity of the motion model,the time-varying of external disturbances and the strong coupling of the control system,the traditional control method is difficult to achieve the desired control effect.On the basis of previous studies,the variable structure sliding mode control theory is used to control the horizontal rudder,and the reaching law method is used to weaken the chattering of the sliding mode control system.Based on the fast power reaching rate and double power reaching rate,a fast double power combination function reaching rate is proposed and applied to the integrated variable structure controller of the rolling motion of the underwater vehicle.Based on the underwater vehicle hydrodynamic model,the horizontal rudder anti-rolling lift model and the variable structure sliding mode control system,the MTATLAB simulation of the underwater vehicle's near-surface rolling control system based on the active flapping of the horizontal rudder is carried out.Compared with the simulation results without the anti-rolling control system,it is found that the anti-rolling effect is obvious under different wave disturbances,and the anti-rolling effect of the underwater vehicle is obvious.The validity of the control strategy is verified by the fact that other parameters have little influence on the submergence.The simulation results show that the rolling control of underwater vehicle based on variable structure sliding mode control has certain theoretical significance and engineering value.