Research On Hydrodynamic Performance And Precise Control Of Underwater Robot Under The Combined Operation Of Propellers And An Umbilical Cable

The application of cable-controlled underwater robotic systems has become increasingly popular in scientific research,ocean observation and operations,underwater engineering construction,and even military applications.However,the complex and variable underwater environment,such as sudden changes in water flow,pose great challenges for predicting the dynamic response of underwater robots,umbilical,and control thrusters.The underwater robot system also faces difficulties in maintaining its position and accurately heading along planned paths.When we study the motion of underwater robots in large scale space using computational fluid dynamics(CFD)methods,we will also face the problems of how to use accurate control strategies,what CFD technology to use to avoid consuming a lot of computing resources and long computing time,so that the underwater robot can achieve the target position manipulation of the robot when moving in large scale space.Therefore,a numerical calculation model and motion control model,including the main body,umbilical cable,and control mechanism of the underwater robot,are constructed within the framework of coupled theory.Taking this as the starting point,the hydrodynamic and control problems that must be solved for the sudden change of incoming flow and the wake generated by the propeller of the working mother ship on the posture of the underwater robot and the precise spatial positioning of the underwater robot during large-scale space motion are solved,It is of great significance for the research and application of underwater robots.The main research object of this paper is to solve the position and attitude control control of the underwater robot in the special underwater flow environment such as sudden flow in different directions and propeller wake of the working mother ship,as well as the precise control and positioning of large-scale space movement.By combining the retraction and release of cables with the propulsion of ducted propellers as the main control method,some hydrodynamic numerical simulation and control methods that must be solved for the precise spatial positioning of cabled remote controlled underwater robots in large-scale space operations are achieved The main research direction is to carry out research on the structural form that underwater robots should adopt in their thesis.This article mainly conducts a series of research work around the determined research direction:Based on the research direction and specific structural forms of underwater robots developed in this article,a hydrodynamic mathematical model of a cable remote-controlled underwater robot system was constructed to match it.In this model,the hydrodynamic characteristics of the underwater vehicle are simulated by the six degrees of freedom motion equation of the submarine,and the dynamic action of the umbilical cable on the underwater vehicle is described by the catenary equation.Add control modules to the constructed hydrodynamic mathematical model to establish the system’s hydrodynamic and control models.According to the requirements of the underwater robot control task studied in this article,incremental PID technology is adopted as the core algorithm of the control module.Based on the operational requirements of the underwater robot,the preliminary configuration of the underwater robot has been established,and the design has been further improved based on the calculation and analysis results of several typical movements.A vertical ducted propeller has been added to the stern of the underwater robot body to better provide lifting and sinking force.Using the established hydrodynamic and control model of the cable remote-controlled underwater robot system,the depth tracking of the underwater robot in special underwater flow environments such as sudden changes in incoming flow in different directions was explored through numerical simulation.The results showed that the depth tracking algorithm was effective in maintaining the original depth of the underwateThree attitude correction control strategies were proposed to address the issue of attitude imbalance during the lifting and sinking motion of underwater robots: stern tube propeller adjustment control strategy,longitudinal center of gravity adjustment system control strategy,and variable center of buoyancy adjustment system control strategy.The control effects of these three strategies were analyzed and compared.Through the use of these control means,it can induce it to produce the required pitching torque,so as to achieve the purpose of manipulating the pitching angle adjustment of the underwater robot,so as to realize the attitude control of the robot.In response to the significant impact of the wake generated by the rotation of the propeller of the working mother ship and the accompanying fixed inflow on the posture of the underwater robot,a depth maintenance algorithm and a pitch adjustment strategy of the robot’s stern duct propeller are used to reduce the impact of the wake wake on the posture of the underwater robot.The underwater robot maintains depth stability and balance of the pitch angle under the control algorithm adjustment,Further validated the effectiveness of the depth preserving algorithm and attitude adjustment strategy.Using the established hydrodynamic and control model of the cable remote-controlled underwater robot system,the technical means that should be adopted for precise motion and positioning of underwater robots in large-scale space were studied through numerical simulation.After research,a “towing+cable retraction and release action+speed and steering control of ducted” propellers method for large-scale spatial precise motion and positioning of underwater robots was proposed.A motion path was planned based on the target position,and the motion was divided into five stages: uniform towing,uniform deceleration and ascent,small distance fine-tuning in the X direction,90 ° turning to the right,and precise motion in the Y direction.This enables the underwater robot to accurately move to the target position in all three directions: X,Y,and Z,And turning the bow to the predetermined angle and maintaining posture balance when reaching the target position,achieving precise positioning and multi degree of freedom motion of the underwater robot during large-scale motion.