Research On Dynamic Modeling And Control Method Of A Two-part Underwater Towed System

In the information age,good underwater communication capabilities are an important guarantee for the deterrence of submarines.However,due to the obstruction of the water medium,it is difficult for submarines to conduct covert high-speed communication underwater.In order to solve this problem,buoy communication technology had been proposed.Submarines can communicae with satellites or shore stations by buoys at normal depths.However,the exposed part of conventional buoy is easily detected by radar.When buoy is towed,it will produce a trail.So the concealment of buoys is insufficient.In order to solve the problem of insufficient concealment of conventional buoys,this thesis combines a folding communication antenna with a towed vehicle with depth and attitude adjustment capabilities to replace conventional communication buoys.During the towing process,the towed vehicle can maintain a certain depth with the wave surface and the stability of its own attitude,so as to ensure its concealment and meet the working conditions of the communication antenna at a certain height above the water surface.In order to test the motion performance of the towed vehicle,this thesis uses the two-part towed system to simulate the motion of the submarine when the towed vehicle is been towing.The two-part towed system is composed of multiple parts so that it’s structure is complex.During the towing process,the two-part towed system has a large span in the depth and length directions,and the folding communication carried by the towed vehicle needs to be raised when performing communication tasks.This raising action will change the center of gravity and the moment of inertia of the towed vehicle.Therefore,in the process of establishing the dynamic model of the two-part towed system,this paper fully considers the interaction of the multi-body and the flexibility of the cable and the influence of the wave force..The sea conditions are changeable.In order to make the towed vehicle work normally in different sea conditions,this thesis studies the depth and attitude control strategy of the towed vehicle.According to the working conditions of the communication antenna,the towed vehicle needs to maintain a certain depth with the wave surface.In order to adapt to the wave conditions under different sea conditions,this thesis uses a fuzzy PID algorithm to control the depth of the towed vehicle.During the towing process,the attitude of the towed vehicle only needs to be stable and does not need to adapt to various wave conditions,so the PD algorithm is used to control the attitude of the towed vehicle.In order to obtain the accurate hydrodynamic coefficients of the towed vehicle,this thesis combines the towing test and fluid simulation to study the hydrodynamic coefficients of the towed vehicle.Based on the above work,this thesis conducted a simulation study on the control performance of the towed vehicle under different sea conditions.The research results show that the depth of the towed vehicle relative to the wave surface changes in the second,fourth and sixth sea conditions.Compared with when it is not controlled,it is reduced by more than 80%;the raising action of the folded communication antenna during the towing process hardly affects the depth control performance of the towed vehicle.The control strategy enables the towed vehicle to meet the working conditions of the communication antenna in the second and fourth sea conditions.In addition,the towed vehicle can effectively resist the interference of waves and other marine environmental factors during the towing process.The two-part towed system can simulate the movement of the submarine when the towed vehicle is been towed.