Research On Mechanism Performance And Soft-landing Dynamic Of Landing Gear In Mars Lander

Mars exploration is the new exploration boom of extraterrestrial exploration missions in recent years,following the moon exploration.It represents the top technology of space exploration at present.The most core component of mars lander is the landing gear,used to realize the soft-landing.A landing gear with good preference or not directly determine the success or not of the soft-landing of the mars probe,even affects the carry-on of the whole exploration mission propert.However,the mechanical design and soft landing performance(cushion and stability performance duiring soft-ladning)should been given higher requestion for landing on Mars,due to the crucial envirorment,such as lots of rocks with different shape and big vulume,dust and floating material on Mars suface,and,long circumuniation time between Earch and Mars.Therefore,some reseaches on Mars lander had been investigated in this paper,including mechanical perference,buffer perference during soft-landing,the bear capablity of the Mars soil and the soil&footpad force relation,the adaptability on difference ground surfaces.The detailed contents are introduced as follows:To obtain the motion performance of the landing leg in Mars lander,the research on the motion workspace,singularity analysis and footpad trajectory of landing leg are carried out.Firstly,the mechanism displacement constraint equation is bulit based on four generalized buffer coodinates,and validated by the CAD model.Secondly,the workspace of the landing gear are analyzed in three states,and the boundary and restriction of the footpad position and each joint are obtained in different states.meanwhile,the Jacobian matrix of the landing gear is solved by numerical integration.The results show that there is no singular point in the landing gear workspace.In addition,a solution method based on four generalized buffer coodinate is proposed to calculate the trajectory of the foot pad in space.The feasiblity on the method are validated using the comparsion anlysis on the footpad position between measured and calcaluted results in certain landing case.Parametric analysis and design on the landing gear of Mars lander is carried out using the explicit finite element method and DOE method.Firstly,the principle of explicit finite element method is introduced,and the energy terms leaded error during calculation are analyzed.An energy/mass conservation criterion based on the generalized energy method is proposed to improve the reliability of the FEM simulation.The FE-model of the landing leg is bulit and analyzed based on this criterion.Comparison analysis between simulation result and test are shown the FEM mode is rationality.In addition,three response surface funcions with severn design parameters are bulit using the DOE(Design of experment)software Design-Expert,based on the validated FEM model.The two most sensitive parameters and its change rules for the related response index are obtained in each response objective index,using Sobol’s global sensitve analysis method.At last,two multi-objective designs are carried out to obtained the design parameters,based on the three response surface functions.The comparsion analysis are taken between the design goal and the calculated result obtained from FEM model using the related design parameters.The analsys results ars shown that the functions fit well with each design objective,then the goal for design of landing gear model quickly is achieved.To obtain the force relation between footpad and soil duiring or after soft-landing,the physical and mechanical performance parameters and its rangement,constitutive model of the Mars soil and Mars soil simulant are investigated.The influence of soil parameters under three different constitutive models are studied by using DOE method.Based on Bekker bearing theory and Janosi soil shear model in terramechanics,the estimation model on the vetical bearing capacity and horizontal dragging capacity of footpad under static condition are established.And the influence on the the vetical bearing capacity and horizontal dragging capacity of footpad are analyzed in the different parameters terms.Moreover,two kinds of soil sampling fields are obtained,based on the modified finite element model validted by the data from VIKING lander.The dynamic response of the footpad in the process of vertical and oblique impact is carried out.The maximum load and invasion displacement of the footpad are analyzed under different speed,mass,angle and sampling field.Meantime,the dynamic response of the soil in the impact process are given.At last,the influence of design parameters of footpad on bearing capacity of footpad are studied in the B sampling field soil modelFor obtaining the adaptability of the lander in the complex grounds,six typical special ground forms are proposed based on the published Mars surface characteristics.Its corresponding ground models are established using finite element method.The ground adaptability of the landing leg in the six ground forms are analyzed,and the results showed that the structure and buffer performance of the landing gear meet the design requirements.Moreover,under the soil sampling field A/B soil models,the landing buffering capacity of the Mars lander,the invading state of its footpads in two soil models are studied under three extreme Loadcases.The results show that the landing buffer performance of the Mar lander meets its design requirements.Also,despite the large invasion of the footpads,the distance from the cabin to the ground still meets the requirements.