Deployment Dynamics and Optimization Design of Space Net System
Author:Gao Qing Yu
Supervisor:tang qian gang zhang qing bin
The accelerated pace of space exploration has resulted in a rapid growth in the number of space debris,which poses a tremendous threat to the usability and sustainability of the orbital resources.It is necessary to take Active Debris Removal(ADR)to solve the space debris problem.Space net system is a kind of removal method for large-scale non-cooperative space debris,which is the hot issue in the field of space debris removal.It has advantages of long operating distance,large fault-tolerant range and flexible application.The working process of space net system is divided into three phases: deployment,capture and deorbiting.The deployment phase is the most complicated phase,which is a typical high-dimensional nonlinear large deformation phase,involving variable mass dynamics,rigid-flexible coupled multi-body dynamics and nonlinear stability problems.Study on the modeling of the deployment dynamic of space net is the key to simulate and optimize the space net system.In this paper,numerical simulation and experimental research on the dynamics and optimization of space net system are carried out.Some achievements have been obtained.(1)The fine modeling technology of flexible cables is studied.First,the geometric nonlinear characteristics and modelling methods of flexible cables are introduced.Then,the mass-damping-semi spring model of cable element is established.Last,a pseudoflexible finite element cable model considering the cable bending is established based on the mass-damping-spring model,and further extended to the triangular element and the rhombus element.The simplified cable model that is suitable for large-scale calculation and considering bending characteristics is obtained.(2)The deployment dynamics of space net system and experiment verifying method.First,the body’s equation of motion in earth coordinate system and the node equation of motion in orbital coordinate system are deduced.Then,the dynamic model of space net deployment process is established based on the reduced cable model,and verified by a series of tests such as the cable parameters test,the net resistance test and the net deployment performance test.The test results show the validity and usability of the model.Last,the differences between space and earth of the net deployment phase is analyzed based on the model.(3)Numerical simulation of the deployment phase of space net system is carried out.First,the evaluation indexes of space net performance is established based on the mission performance and the design requirements.Then,a two-stage launching and multi-point pulling scheme of space net is proposed and verified by numerical simulation and ground tests.Last,the property of different net topology configuration and the shape control method is studied.(4)The multi-objective optimization design of space net system is studied.First,the multi-objective problem of space net system is proposed.Then a multi-objective optimization framework for this problem is set up to carry out this optimization design based on the Kriging modelling technology and MOEA/D-EGO optimization algorithm.Last,establish a multiobjective optimization example model of space net capture system based on objectives of on-orbit capture capability and system cost,results of which can be useful to the design of space net system.(5)Integrated simulation of the space net system for the whole capture process.First,the dynamic models of space net system for deployment,capture and deorbiting phases are respectively established.Then,an integrated simulation framework of space net system is established based on parametric modeling method,which is used to integrate and solve the whole process of space net system.It is convenient to carry out the whole process optimization design of space net system in later research.In this paper,the deployment dynamics of space net system is discussed.The study consists of four parts: the cable /net dynamic modeling and test set-up methods,the analysis of the key problems in the space net design,the multi-objective optimization design for the system and the whole process integration technology.Research results show important guiding significance and engineering value for the development of space net removal technology.