Design Of Underactuated AUV Control System And Research On Trajectory Tracking

Oceans account for more than 70% of the earth's surface.They are rich in underwater organisms and resources,Which are the most important resource treasury for human beings.The development and utilization of oceans are of great significance for the present age.Autonomous Underwater Vehicle(AUV)plays an important role in ocean development.For cost savings and weight reduction,AUV is usually designed as an under-actuated system.Underactuated AUV has the advantages of high reliability,low energy consumption and high propulsion efficiency.Its control system performance and trajectory tracking control ability are the basis and guarantee for successfully completing a variety of underwater tasks.However,under-actuated AUV has strong non-linearity and strong coupling,and underwater operations are vulnerable to external disturbances such as ocean currents.Therefore,the research of underactuated AUV control system design and trajectory tracking control has important scientific significance and social value.Firstly,according to the actual needs,the overall design of the AUV control system is carried out,the control system framework is built,and the communication scheme is determined,the hardware and software design of the AUV control system are carried out,and some modules are tested.The test results show that the designed module has good stability.In order to improve the anti-jamming and attitude adjustment ability of under-actuated AUV,a gravity center assistant adjustment system is designed.Secondly,the kinematic coordinate system of AUV is established,and the six-degree-offreedom kinematic and dynamic equations of AUV are given.According to the actual characteristics of AUV,the mathematical model of AUV is simplified,and the simplified horizontal and vertical motion models are obtained,which lays a foundation for the follow-up study of AUV trajectory tracking control.Thirdly,the back-stepping sliding mode controller is designed by combining the backstepping method with the sliding mode variable structure control method.Serret-Frenet coordinate system is used to describe the trajectory tracking error,and the horizontal and vertical trajectory tracking controllers are established respectively.The designed back-stepping sliding mode controller is compared with the current conventional method.The simulation results show that the designed backstepping sliding mode controller has good robustness.Finally,considering the influence of complex disturbances,an adaptive fuzzy logic system is added to the backstepping sliding mode control to identify the complex disturbances on-line,to improve the motion quality of the system when it reaches the switching surface and weaken the sliding mode chattering.A backstepping adaptive fuzzy sliding mode controller is designed for the horizontal and vertical surfaces respectively,and the designed controller is compared with the improved backstepping sliding mode controller.The simulation results verify the effectiveness and robustness of the designed controller.