Dynamic Simulation Of Lunar Soil Sample Bag Reshaping Process

Lunar soil sample bag reshaping process is an important part of Chinese Lunar Exploration Program Phase III.It is often the case that the points on sample bag are overlapped or failed to winding in the experiment.For this situation,system equation about the sample bag reshaping system is built to analyze the pattern of motion and the factors affecting sample bag slide,providing a reference for the sample bag reshaping system successfully proceeding.Firstly,based on the characteristics of the system,the parameters at the inlet of the winch are selected as the system description variables and the system equation is established by the velocity relationship between the winch and the sample bag.The arc length of the sample bag to be rolled into the winch is calculated,and the accretive chord method in the calculation geometry is chose to interpolate the transition section sample bag.According to the system motion equation,it is able to calculate the optimal movement speed of the guide sleeve and to judge whether the sample bag is overlapped.Secondly,mechanical factors influencing the sample bag reshaping process are analyzed.Considering the virtual power theory,tensile force of the sample bag at the inlet of winch is calculated.And based on the tensile force of this point,the dynamics equation about the sample bag on winch is established.To solve the equation,the contact force between sample bag and winch is available.If the contact force in normal direction is less than zero,the sample bag will be divorced from winch,and if the contact force in radial direction is less than sliding friction,the sample bag will slide from the winch.Finally,a simulation software is developed by MATLAB for this lunar soil sample bag reshaping system,which can calculate the overlapping points of the sample bag on winch,feature points arc length coordinates of the system,the drag torque of the winch,and failure time and points of the sample bag reshaping under different parameter settings.After analysis of the effect of different velocity and structure parameters,conclusions are reached that the overlapping condition of the sample bag is sensitive to the velocity of guide tube,and the tensile force of sample bag and the sliding friction are the key factors influencing the sample bag reshaping process.Based on the conclusions,suggestions for reducing the failure risk are presented.