Large Swath And High Resolution Satellite Integrated Structure Multi-objective Optimization Design

Large-swath and high-resolution optical satellites can quickly achieve large-area regional coverage and detailed investigation due to their large field of view,high-resolution imaging capability which makes it an important development direction in the field of Earth observation.Under the limited weight constraint,the Satellite structure design needs to meet multiple design goals at the same time,and these goals are sometimes mutually influential or conflicting,which makes the multi-objective optimization difficult.This type of problem is called multi-objective optimization which is an important issue in structure design.The large-swath and high-resolution satellite named KF satellite studied in this paper has a payload of camera with three-mirror anastigmat optical system.The satellite platform designed centered the optical camera weighs about 180 kg and is responsible for supporting the other sub-systems whose weight are over 1120 kg,and for providing support for satellite optical cameras and sub-systems,withstanding and transmitting external loads like axial and lateral overloads,as well as harmonic excitation loads,micro-vibration loads,etc.and maintaining stability.It needs to satisfy multiple design goals such as strength,stiffness,dynamic performance and vibration isolation performance.Integrated structure design is adopted in this article and it's beneficial to realize the benign distribution of design constraints.Hence each subsystem can focus on their main design tasks,maximize satellite imaging performance and reduce design redundancy,weight and size of the satellite,and finally achieve design specifications.In this paper,for KF satellite structure,based on the design concept of structural integration,the multi-objective optimization design method adopting genetic algorithm is used to propose for the optimization design of the satellite platform structure.For the requirements of the overall vibration isolation performance of the satellite,non-optical micro-vibration integrated modeling analysis and test methods is proposed for multi-objective isolation design.This paper mainly studies the followings.(1)Multi-objective optimization theory analysis of satellite structure design.Firstly,the wide-satellite integrated structure of the research object is equivalent to the two-degree-of-freedom spring damping model,and the influence of the connection stiffness and connection damping of each subsystem on the frequency response characteristics of other sub-systems is analyzed.Secondly,the generation and suppression method of micro-vibration theory is explained.Then,the multi-objective genetic algorithm and its applicability are expounded,and the algorithm is used to optimize the multi-objectives of the KF satellite camera truss.The result is verified by experiments.Finally,the research framework of step-by-step multi-objective optimization of satellite structure is discussed,and the main design goals of each design stage are determined.(2)Studying satellite topology structure topology,multi-objective size optimization and analysis of satellite dynamic performance using FEM.Firstly,using the variable density method,achieving the minimum flexibility of X/Y/Z direction as a goal,the initial structure form is obtained.Then the effect of the truss cross-section size and the cross-section size of the honeycomb sandwich plate on the dynamic response is described.Having minimum reponse of key position of the optical camera under the sinusoidal vibration excitation in the X/Y/Z directions as the design goal,and the NSGA-II is used in the Isight environment.After iteratively computed,the optimal size of the Pareto optimal solution,that is,the 19 design variables of the platform structure is obtained and the platform mass is 177.7kg.Finally,the FEM is used to analyze the dynamic characteristics of the satellite and results show that the strength and stiffness requirements are met.(3)A non-optical micro-vibration integrated modeling and analysis method for large TMA optical systems was proposed for the first time,and the multi-objective optimization and implementation of the vibration isolation device structure was carried out.Firstly,the principal of the cause of reaction wheel vibration and the influence on the imaging are expounded.The optical amplification factor and the detailed modeling method of the image shift caused by the displacement of the mirror of the optical system are given.Taking the image shift of Y as an example,the influence degree of the main mirror,the secondary mirror,the three mirror and the folding mirror on the image shift is analyzed.The NSGA-II multi-objective optimization GA in Isight environment was used to optimize the structure of the vibration isolation device,and the optimized dimensions of 12 relevant design variables were obtained and vibration isolation was implemented.(4)Ground dynamics tests of KF satellites were carried out to verify the effectiveness of the integrated structural design.Firstly,sinusoidal vibration test.The vibration table is used to simulate the low-frequency excitation of the launch phase,and the frequency response of the satellite integrated structure is obtained.The result satisfies the requirement that the amplitude of the sinusoidal vibration of the equipment is less than 8g.Then,the micro-vibration test is proposed,and the non-optical micro-vibration test scheme is proposed.The suspension method of the quasi-zero stiffness principle is used to test the image shift caused by the reaction wheel.The X-direction image shift is less than 0.228 pixels and the Y-direction image shift is less than 0.237 pixels,which indicates that the micro-vibration design requirements are basically met,and the vibration isolation design is effective.