Research For Passive Control For Longitudinal Vibration Of Lifting Pipe In Deep Sea Mining System

Abstract:The current situation is growing increasingly that terrestrial resources shortage, rapid development of science and technology. Extracting marine resource is the strategic target for all nationalities, and it is of far-reaching significance for the emerging Chinese nation fulfilling "China Dream" especially.The deep-ocean mining system includes the mining platform, the lifting pipe subsystem and minerals-collector. And the mining ship, the lifting steel pipe, the middle-module, the lifting pump and lifting hose are the important part of the lifting subsystem. This paper deals with the heaving-motion of mining ship and the longitudinal vibration of lifting steel pipe based on1000m trial system of deep-ocean Mining. The method is provided that applying vibration absorbers at the position of pump and middle-module. This paper deduces the longitudinal vibration characteristics of lifting subsystem by Galerkin Theory with or without vibration absorbers at pump and middle-module. And variable metric method of BFGS is used to solve the problem of design optimization of vibration absorbers in water for the first time. In order to verify the simulation results, the model experiment system of reducing longitudinal vibration with vibration absorber method is established. The study of this paper provide technical references for deep-ocean mining and trial, and a new proposal for strengthening safety of mining.The main contents of this paper are following:1. According to the environment of ocean in Chinese marine mining areas, the wind, wave and current acting on the deep-ocean mining system are analyzed, especially for the environment forces of the lifting pipe subsystem in a certain depth sea. And the harmonic motion equation of mining ship in wave is deduced with empirical equations of Moor.2. Galerkin Theory is adopted to study the longitudinal vibration of mining ship in heave motion. The dynamic equations of lifting pipe subsystem are deduced, and simulated in the different sea conditions. The variation rule of longitudinal vibration and axial stress is obtained at the position of pump and middle-module for lifting pipe system with wave frequency.3. To solve the longitudinal vibration of lifting pipe subsystem for mining ship, the method of applying vibration absorbers is proposed. The changes of longitudinal vibration and axial stress for the lifting pipe subsystem at the position of pump and middle-module with Galerkin Theory. The simulation results show the effectiveness of the vibration absorbers method for reducing the longitudinal vibration, especially better successful with all vibration absorbers at position of pump and middle-module.4. Different effects of reducing the longitudinal vibration appear with different parameters of vibration absorbers. Then a two-degree-of-freedom system composed of a main vibration system and a vibration absorber in the water has been considered. The optimal condition for vibration absorber has been determined with interior penalty function method and variable metric method of BFGS. The results that six parameters affecting the optimal condition of vibration absorber in the water instead of four parameters in air are obtained for the first time. These conclusions enrich content of optimization theory for parameters of vibration absorber, and have prepared design parameters for the model experiment system of reducing longitudinal vibration with vibration absorbers.5. The specific design scheme of model experiment system for reducing longitudinal vibration with vibration absorber is proposed. This includes:a Stewart6-DOF platform simulating the motion of mining ship, a classic Voigt type of spring-damping for vibration absorber, and a size of the storing reservoir with2.6m×2.6m×3m for experiments. A lot of model experiments are done with several wave cycles. The results of experiments display good performance with the simulation. The correctness of simulation results is verified by experiment. And that showed the vibration absorber method is efficient for reducing the longitudinal vibration of lifting pipe subsystem.