Researches Of Key Technologies And Control Methods Of Working Boat Davit

The working boat davit is a special type of hoisting equipment on ships. Its function is tolaunch and recovery working boat on mother ship. The launch and recovery of the workingboat when the mother ship is rolling in complex sea states can be carried out safely with it,which is impossible for ordinary davits. The working boat davit is absolutely necessary forisland capture, supply on the sea, persons rescue, patrol and escort of the navy. It has broadapplication prospects. As the working environment of the davit is complex, the launch andrecovery of the boat must be safe. It means that the problem of attitude control when theworking boat is prepared to be lifted and the problem of violent swings reducing when theworking boat is in the air must be solved. To meet the requirements of wave motioncompensation technology and swing reducing technology, developing the davit that can beused safely in high sea state by studying control methods of wave motion compensationsystem and swing reducing system, simulating the performance and carrying out relevantexperiments is not only an important development in theories of wave motion compensationtechnology and swings reducing technology of the davit, but also of great significant to thetechnology developments of domestic marine equipments, the defence of maritime rights andinterests and it satisfies the needs in military.The paper summarizes the principle of the working boat davit and key technologies oflaunch and recovery the boat in high sea state, the present situations were analysed and thedirection and content of the paper was determined which based on consulting manydocuments that are domestic or abroad. The influences of the ship to attitude of the workingboat and the effects of the wave compensation system were analysed according to differentprocesses of launch and recovery. The nonlinear model of ship motion is built which providesthe foundation of the analysis of the wave motion compensation system. The mathematicalmodels of rolling and heave of the working boat with the wave motion compensation systemactive were built and the mathematical model of the wave motion compensation system wasbuilt, with provide the foundation of simulation of the system. The mathematical model ofviscous damping devise and the dynamic model of the swing reducing system were built onthe basis of the principle of the damping swing reducing system, which laid the foundation ofthe study of the damping swing reducing system.To control the attitude of the boat on the water, the hydraulic winch system of the wavemotion compensation system using tension dissipation compensation technology wasdeveloped, and the mathematical model of the wave motion compensation system was built. Based on the analysis of the relative motions between the boat and the mother ship, theanalytic method of the maximum design velocity of the wave compensation was proposed,and the velocity characteristic of the system was studied. The effects of the structureparameters were discussed and the parameters were optimized by using the particle swarmoptimization algorithm (PSO). The rationality of the parameters was corroborated bysimulation.The mathematical model of the passive damping swing reducing system was built on thebasis of its principle, and the viscous damping swing reducing system was designed based onvibration analysis, and the performance indexes of the swing reducing system were proposed.The effects of the damper, the weight of the boat and the position of the hoisting point werestudied based on the working condition analysis of the system. The simulations showed thatthe damper parameters designed by ship motion, the weight of the boat and the position of thehoisting point worded well.As the limitations of the passive swing reducing system, the active swing reducing systemwas proposed, and the mathematical models of the system ware built. As the system isunderactuated, the active swing reducing controller is designed and the control method wasstudied. What are mentioned above provide the foundation of the active swing reducingsystem.The experiments of wave compensation system and swing reducing system are carried outby using the ship motion simulation equipment. The indexes of compensation characteristicsare obtained, and the method that control the attitude of working boat by using wavecompensation technology and swing reducing technology proves to be effective.