Dynamics Modeling And Optimization Design Of Spacecraft Separation Device

With the development of aerospace industry,modern satellite technology has made continuous progress,its application scope is more and more widely,and more and more functions can be achieved,that is,the precision instruments carried by satellites also increase.In order to reduce the potential safety hazard caused by the increase of size and mass of the satellite,and with the progress of space technology,the development of small satellite system with short cycle,light weight and low cost has become one of the research emphases.Connecting and separation device is the executive mechanism to connect the spacecraft cabin or two spacecraft,and to unlock and separation the spacecraft arrived at the formal orbit.The rapid development of small satellites makes the separation technology become a key link in the launch mission,the high-precision components carried on the small satellites are easy to be damaged due to the shock vibration generated when entering the predetermined orbit for separation.Although the traditional pyrotechnic separation technology can complete the unlocking task,it has some disadvantages such as large impact,poor reliability and easy to produce pollutants for the small satellite with light mass.Non-pyrotechnic separation device is a new device aimed at the shortcomings of conventional pyrotechnic device,there are some advantages like high reliability,low shock,no pollutant and reusable,etc.But the process of contact and friction in the implementation of action of non-pyrotechnic device is extremely complicated,thus non-pyrotechnic separation technology has become an important and urgent demand in aerospace field.In this paper,a non-pyrotechnic device has been researched,the device uses shape memory alloy as trigger resource and it is safe and reliable,the task of connecting and separation between the star and arrow is accomplished through the relative movement of the segment nuts and the bolt.The main research contents are as follows.(1)Research on actuation principle and force analysis of the separation device.Firstly,the structure of the non-pyrotechnic separation device is analyzed,and it is divided into nut assembly and bolt assembly according to the overall structure of the separation device.The operating principle and mechanism of the unlocking and separation process of the separation device are described.Since shape memory alloy spring is used as the driving source of the separation device,in order to analyze the force characteristics of the separation device in the process of working,the four modules of pin ball unlocking,nuts separation,thread connection and bolt pre-tightening are studied,which lays a foundation for the subsequent simulation and optimization work.(2)Research on the contact dynamics of the separation device.The hysteretic damping contact model proposed by Lankarani and Nikravesh is studied.The calculation method about the parameters of contact force model based on Hertz contact theory is determined,and the contact stiffness calculation expression is established for the parts of the separation device which have impact.In order to ensure the reliability and accuracy of the modeling and simulation,the restitution coefficient,power exponent and approach velocity in the contact model are studied to determine the influence of the parameters on the contact process.(3)Research on dynamics modeling and simulation of separation device.Targeting the process of unlock and separation for the no-pyrotechnic separation device based on memory alloy spring as a research object,combined with the movement principle analysis and the contact theory analysis of the separation device,the multi-body dynamics software ADAMS is used to establish its dynamic model.It can effectively simulate the connecting,actuation,separation process of the separation device and the calculation results of the acceleration response are consistent with the actual results.According to the established model,the influence of the SMA spring and the preload of bolt on the impact response is studied,and the influence degree of the stiffness coefficient of the four spring elements in the separation device on the impact response is studied by using the design of experiment method,providing reference for the optimization work.(4)Research on optimization design of spring in the separation device.The multidisciplinary optimization software Isight and ADAMS are integrated to establish the spring optimization model.The Kriging approximation model is established as a substitute for the original time-consuming simulation model.The optimization mathematical model of spring stiffness is set up,and multi-island genetic algorithm is employed for the optimization of spring stiffness.The acceleration response of the separation device is reduced about 6.7%after optimization,and the proportional error between approximation model and simulation results is about 0.74%.The size of the separation spring is further optimized combined with the optimization results,and the optimization mathematical model is established to reduce the overall mass of the spring.The optimal size value is obtained under the condition that the constraints are satisfied,and the impact response of the separation device is still reduced by5.3%.This paper targets the process of unlock and separation for the no-pyrotechnic separation device based on memory alloy spring as a research object and a series of studies on contact analysis,dynamics modeling and simulation,approximation modeling and optimization are carried out based on the contact theory,multi-body dynamics and optimization algorithm.Finally,the impact response of the separation device is improved to some extent and the simulation modeling and optimization analysis of the paper can provide reference for the development of the separation device.