System Design And Key Parameter Optimization Of A Long-Voyage Underwater Glider

Underwater glider,as an autonomous underwater vehicle driven by buoyancy,travels in the seawater following a zigzag trajectory,which is widely applied in ocean observation due to its advantages of long endurance and low cost.With the development of marine research,higher requirements have been proposed for the endurance of underwater glider.Supported by national science and technology projects,this study proposes an engineering prototype of long-voyage underwater glider named Petrel-L,which can meet the strong demand for environmental monitoring in open ocean and deep sea.To improve the cruising ability of underwater glider,a gliding range model is established and the key parameters that greatly influence the gliding range are determined.The optimization design of these parameters is researched.The design optimization frameworks of key parameters within a single discipline or multiple disciplines are established respectively,through which the key design parameters are optimized and the cruising ability of Petrel-L is improved obviously.The achievements of this dissertation are described as follows:1.This dissertation proposes the optimization design methods of hydrodynamic shape and near-neutrally-buoyant pressure hull for underwater glider based on the gliding range model.First of all,a gliding range model considering the change of net buoyancy and ocean environment is established based on the dynamic model of steady motion in vertical plane,which improves the prediction accuracy of gliding range.Then,the optimization frameworks of the key units are established.1)In the hydrodynamic shape design,the complex engineering in hydrodynamic shape optimization is transformed into the optimization of mathematical model by response surface approximate technology,in which the coupling relationship among dimension parameters is considered.2)The mechanical model of the near-neutrally-buoyant pressure hull constructed with multiple intersecting spheres is established using thin shell theory,based on which the optimization model of the pressure hull is established.Finally,this dissertation studies the effects of the hydrodynamic shape optimization and near-neutrally-buoyant pressure hull optimization on the gliding range.2.The optimal control parameters in the whole life-cycle of underwater glider are obtained to maximize the gliding range.The control parameters of the underwater glider with different hotel loads are studied firstly.Then,a segmented control strategy is proposed based on the nonlinear trend of net buoyancy when Petrel-L moves in the seawater,the applicable conditions of which are studied.Finally,the variation trends of the key design parameters under the influence of the biofouling are analyzed by parameter identification.The effects of the changed parameters on the gliding range are studied,which can be partly remedied by control parameter optimization.3.This dissertation studies the application of multidisciplinary design optimization theory in the optimization design of underwater glider.Based on the cooperative division and distributed design architecture of Petrel-L,the multi-disciplinary design optimization framework of key parameters is established by integrating the response surface approximation technique and the collaborative optimization algorithm considering the coupling relationship of key parameters,based on which the key parameters are collaboratively optimized.4.The first Chinese long-voyage underwater glider is developed with a gliding range larger than 4000 km.A series of tests are carried out to verify the rationality and reliability of Petrel-L.The gliding range and working time of the Petrel-L underwater glider are increased from 1000-km scale and one month to 4000-km scale and ten months respectively,which improves the technical level of China’s far-reaching marine environmental monitoring.