Research On Motion Control Of Observation ROV At Low Velocity

There are a large number of reservoirs,dams and wading bridges in China,and the country spends huge amounts of money to inspect these facilities every year to maintain their normal functions.Traditional detection methods are mostly carried by divers with professional equipment for detection.With the continuous reduction of the cost of ROV,ROV is gradually applied in the detection of water conservancy facilities.Aiming at the working environment of Underwater Bridge and dam detection,an observation ROV is developed to replace the inspection work of divers.On this basis,this paper makes the following main research:(1)In this paper,according to the research status of ROV and the characteristics of underwater detection environment,and combined with the advantages and disadvantages of the primary observation ROV developed by the team,the overall scheme of the observation ROV is formulated.The mechanical structure and the hardware and software of the control system are introduced.The mechanical structure mainly includes frame structure,thruster arrangement and sealed cabin,and the strength of sealed cabin is checked by Workbench.The hardware and software system of the observation ROV control system is described,the core hardware is selected,and the software module function is explained.(2)Two coordinate systems are established to describe the kinematics of the observation ROV,and then the forces experienced during the movement of the observation ROV are analyzed,including inertial matrix,Coriolis force,fluid resistance,restoring force and cable force;combined with observation ROV The structural characteristics of the ROV are required to be simplified to establish the six-free kinematics and dynamic equations of the observation ROV.Combined with the structural characteristics of the observation ROV,the necessary simplifications were made to establish the six free kinematics and dynamic equations of the observation ROV.(3)In order to achieve precise control of the observation ROV,the hydrodynamic system of the observation ROV must be obtained.The theoretical basis,turbulence model and grid of CFD simulation calculation are briefly described.Simplify the model,and then use Fluent to simulate and observe the resistance of the ROV in different directions.The least squares method is adopted to fit the resistance to obtain the linear and quadratic damping terms,and the additional mass is calculated by the empirical formula.(4)The depth trajectory tracking control of the observation ROV on the vertical plane is studied.In order to obtain the dynamic equation of the observation ROV on the vertical plane,two decoupling methods are introduced,and finally the error decoupling based on the ROV model is adopted.The adaptive control,backstepping method,sliding mode control and nonlinear disturbance observer(NDO)are introduced,and an adaptive backstepping sliding mode controller based on NDO is designed.Simulink is used for simulation experiments.The simulation results show that the controller has good control effects on fixed-value disturbance and time-varying disturbance,and NDO has a good online observation effect on external disturbance.(5)Finally,in order to verify the rationality of the design.The observation ROV was manufactured,the key components were tested individually,and the electronic and power sealed cabin were tested.After passing the single commissioning,the pool test is carried out,and the commissioning results basically meet the expected requirements.The research results of this paper provide systematic guidance for the development of observational ROVs,acquisition of system parameters,motion control on the vertical plane,and physical production.At the same time,it has guiding significance for the development and control of other types of ROVs.