【作者】 金大玮；

【导师】 李建桥；

【作者基本信息】 吉林大学 ， 仿生科学与工程， 2013， 博士

【摘要】 月球探测现在已经成为世界航天活动的重要组成部分，月球车在月球探测中起着至关重要的作用。我国首个月球探测计划“嫦娥工程”的第二阶段“落”，即是发射月球探测车，在月球上进行实地勘察。月球探测车必须具备较高的通过性，才能满足科学探测的需要。月球表面被松软的月壤所覆盖，重力是地球的1/6，这种条件并不利于月球车的通过。为使月球车完成探测任务，应在车辆—地面力学的基础上，考虑月球的实际环境，通过试验方法、理论方法、数值仿真方法等手段对月球车轮与月壤间的相互作用进行研究、预测。这些工作能够为月球车的通过性研究提供必要的理论基础和试验手段。针对月球探测车驱动轮的行驶需要，研制了轻载荷（外载荷不大于100N）月壤—车轮土槽试验系统。使用吉林大学自行研制的JLU-2a模拟月壤，对四种具有代表性构型的月球探测车驱动轮进行通过性土槽试验，研究月球车驱动轮的通过性能。总结车辆—地面力学传统模型，分析承压特性参数的测量误差对沉陷量、滚动阻力误差的影响，修正沉陷量与驱动扭矩的计算模型并验证公式的正确性。讨论光滑圆柱刚性轮行驶时，轮下法向应力与切应力的变化情况与轮上绝对速度竖直向下一点的位置对车轮受力的影响。最后通过有限元法分析轮刺宽度、高度对驱动轮通过性能的作用。考虑月球车实际负载以及月面重力场，研制轻载荷月壤—车轮土槽测试系统。轻载荷月壤—车轮土槽测试系统由土槽机械系统与土槽测控系统两部分组成。土槽机械系统采用土槽固定、被试车轮运动的形式；土槽测控系统可以完成测取被试驱动轮的驱动扭矩、水平位移、垂直位移、转动速度、滑转率等基础参数以及对土槽中模拟月壤表面位置定位的任务。因为加载方式为轻载荷，系统中的各种结构都被尽量简化以及轻量化，最大限度地减少机构间的摩擦并使用小量程传感器。试验时，以沉陷量、驱动扭矩、挂钩牵引力、牵引效率为试验指标。根据月球探测车的实际行驶情况确定垂直载荷的变化范围为0～100N、滑转率的变化范围为0～60%、车轮行驶速度在0～50mm/s之间变化。确定JLU-2a为试验用模拟月壤，有自然和松软两种整备状态。使用四个不同构型的试验驱动轮。试验结果表明，模拟月壤被四种驱动轮破坏的形貌特点与驱动轮的结构形状有很大关系；对由系统自动采集的有刺圆柱轮的沉陷量、驱动扭矩、滑转率进行初步分析，由于轮刺的作用这三个量随位移的增加而呈周期性的变化。对轻载荷月球车驱动轮通过性试验进行分析。光滑轮的轮辙产生具有水纹状或鱼鳞状的辙纹，辙纹的高度、宽度、边缘的压溃程度随滑转率的增加而增加。有刺轮的轮辙深度随滑转率的增加而增加，辙纹表面的宽度减少，刺坑周围月壤被扰动、挑土的现象会更严重。四种试验驱动轮的沉陷量、驱动扭矩、挂钩牵引力均随滑转率的增加而增加，牵引效率随滑转率的增加先增大后降低。速度的变化范围在15mm/s～35mm/s之间时，四种试验驱动轮的沉陷量、驱动扭矩、挂钩牵引力受速度变化的影响甚微，牵引效率则受速度的影响明显；光滑圆柱轮与有刺圆柱轮的挂钩牵引力、有刺鼓形轮的驱动扭矩随速度的增大而增大；四种试验驱动轮的牵引效率、光滑鼓形轮的驱动扭矩随速度的增大而减小。垂直载荷在30N～90N之间变化时，四种试验驱动轮的沉陷量、挂钩牵引力、驱动扭矩随垂直载荷的增加而增加；有刺圆柱轮、光滑鼓形轮的牵引效率随垂直载荷的增加而减少；光滑圆柱轮的滑转率低于30%时，牵引效率随垂直载荷的增加而减少；有刺鼓形轮的牵引效率的最大值随垂直载荷的增加而降低。四种试验驱动轮在松软状态时的沉陷量要大于自然状态时的沉陷量；光滑圆柱轮、有刺圆柱轮在自然状态时的驱动扭矩、挂钩牵引力、牵引效率高于松软状态；光滑鼓形轮、有刺鼓形轮松软状态时的驱动扭矩、牵引效率高于自然状态；光滑鼓形轮、有刺鼓形轮自然状态时的挂钩牵引力高于松软状态。对于四种试验驱动轮，有刺轮的沉陷量低于光滑轮的沉陷量；有刺轮的驱动扭矩、挂钩牵引力、牵引效率高于光滑轮的相应参数。分析车辆—地面力学的传统公式，确定适合修正的力学模型物理量。针对适合修正的沉陷量、滚动阻力模型，研究承压特性参数的试验误差对沉陷量、滚动阻力误差的影响。在适合月球车工作的参数变化范围内，n对沉陷量误差的影响要大于k c、k，、的输入误差对沉陷量、滚动阻力误差的影响可以忽略不计。进行相关统计分析，沉陷量相对误差的百分比误差为16%，置信水平为90%；滚动阻力相对误差的百分比误差为8%，置信水平为96%。根据月球车轮的行驶特点对沉陷量、滚动阻力模型进行修正，修正时要考虑滑转方面的修正、力学参数试验误差引起的误差方面的修正，除此以外，鼓形轮要考虑轮型方面的修正，有刺轮要考虑轮刺效应方面的修正。根据分析以及试验结果，给出修正后的模型，将四种试验驱动轮的修正后模型计算值与试验值进行对比，沉陷量误差在1%～19.7%之间；滚动阻力误差在1.5%～19.9%之间。分析光滑圆柱轮与月壤之间的相互作用关系。光滑圆柱轮与模拟月壤接触部分的法向应力与切应力随变形指数、摩擦模量、轮径的增大而增大，内聚模量、轮宽对法向应力与切应力几乎没有影响，内聚力对切应力影响甚微，切应力随摩擦角的增大而增大。在接触角介于0与最大法向应力所对应的接触角之间时，法向应力、切应力随滑转率的增大而减小；在最大法向应力所对应的接触角与最大接触角之间，滑转率对法向应力没有影响，切应力随滑转率的增大而增大。法向应力与切应力随沉陷量的增大而增大且沉陷量对应力影响显著。刚性轮轮缘上绝对速度竖直向下的一点与月壤接触时，在这点以上部分，月壤会作用一部分推土阻力在轮上，而这一点以下部分，月壤会有一定的附加牵引力推动车轮。如果这一点不与月壤接触，月壤作用在轮上的推土阻力较小，同时会施加一定的牵引力在车轮上。这一点的位置v与滑转率有关，随滑转率的增大而增大。 vmin随速度与垂直载荷的增大而增大。在低速的条件下，与月壤接触的最小角度变化不大，在滑转率介于20%～30%之间出现。通过ABAQUS软件自带的Druker-Prager本构模型对模拟月壤进行建模，设定相应条件后，针对趋势相同的轻载荷月球车轮通过性试验进行相应的仿真分析。仿真后的轮辙以及相应指标同试验结果相近，可以有效地对月球车轮通过性试验进行仿真模拟。仿真分析三种具有不同尺寸的轮刺对月球车轮通过性能的影响。在轻载荷、低速条件下，轮刺宽度的变化对轮辙的形貌、沉陷量、挂钩牵引力、驱动扭矩影响较小。轮刺高度增大时，轮刺“刨土”的现象较为严重，沉陷量、挂钩牵引力增大且波动较大，但是驱动扭矩没有明显变化。本文研究内容可以为月球车驱动轮的通过性预测以及设计提供技术参考以及理论基础。更多还原

【Abstract】 Lunar exploration has been the important part of space activity, and lunar rover play avital role in lunar exploration. The second stage of China lunar exploration project is―drop‖,that is, lunar rover dorps and carries out field survey on the moon. To satisfy the requirementof science exploration, lunar rover must have high traction ability. The surface of lunar iscoved of soft lunar regolith, the gravity of lunar is only one-sixthes gravity of earth, thecondition is not good for the traction ability of lunar rover. In order to fulfil explorationmission, the relationship between the lunar wheel and lunar regolith should be studied andpredicted by test method, theory method and numerical simulation based onterrainmechanics and real condition of lunar. The practices can provide necessary theorybasis and test method with the study of passing ability of lunar rover.The author is grateful for the financial supported by National Nature ScienceFoundation of China（No.50875107）, National High-tech Research and DevelopmentProgram of China（No.2010AA101401-3） and advanced project of Jilin University andChinese Academy of Space Technology. Firstly, Aimed at the requirement of lunar rover, theresearch developed light-loading soil bin equipment. The research used JLU-2a lunarstimulant which is developed by Jilin University, carried out soil bin test about tractionability for four lunar rover wheels with typical shape, studied the traction ability of the fourdriving wheels. Secondly, the traditional terrainmechnics is summarized, the effect ofmeasure errors of pressure characteristic parameters on sinkage errors is analyzed, thecalculation model of sinkage and rolling resistance are corrected, and the correctness of theformulaes are verified. Thirdly, the change of normal stresses and shear stresses under thesmooth cylinder wheel is analized, and the effect of the position where the velocity of thepoint on the wheel is downward on the forces acting on the wheel is analyzed. Finally, theresearch study the effect of the width and height of the lugs on the traction ability of thedriving wheels by FEM.On the consideration of the actual loading of lunar rover and gravity field of lunar, the reseach develops the light-loading soil bin system. The soil bin system is consistent ofmechanical system and measure and control system. The soil bin is fixed and the wheel canmove in mechanical system, and the measure and control system can fix the position on thesurface of the lunar stimulant, and measure driving torque, horizatla displacement, verticaldisplacement, rotation velocity, slip ratio. Beacause of light-loading, the structure issimplified and lightweight, the friction of mechanisms is reduced to the extent, and smallrange sensors are used. The research selects sinkage, driving torque, drawbar pull, tractionefficiency as test indexes. Based on the acual driving, the vertical loading changes from0to100N, slip ratio changes from0to60%, the velocity of the wheel changes from0to50mm/s.JLU—2a is selected as lunar soil stimulants in the test, the states of the lunar soil stimulantsare natural and soft. The four driving wheels with diffirent shape are used. The appearancecharacteristic has relation with the shape of the driving wheel. The sinkage, driving torqueand slip ratio which are directly gotten from the cylinder wheel with ruts by the soil binsystem are analyzed, these parameters periodically change with the increase of displacementbecause of the lugs.The research analyzes traction ability test of lunar driving wheel. The ruts of smoothwheel have characteristic of water traces or fish scale traces, and the height, width anddegree of damage of edge increase with slip ratio. The depth of the ruts of the wheels withthe lugs increase with slip ratio, width of the lugs decreases with slip ratio, and the lugs stirup more lunar stimulant around the ruts. The sinkage, driving torque, drawbar pull increasewith slip ratio, and tractive efficiency increase firstly, then decrease with slip ratio.Little influence has variation of velocity on the sinkage, driving torque and drawbar pull ofthe four wheels as the velocity changes from15mm to25mm, but lager influence on tractiveefficiency. Drawbar pull of smooth cylinder wheel and smooth drum wheel increase withvelocity, the same as the driving torque of drum wheels, but tractive efficiency of the fourwheels and driving torque of the smooth drum wheel decrease with velocity. As verticalloading changes from30N to90N, the sinkage, drawbar pull, driving torque increase withvertical loading, and tractive efficiency of cylinder wheel with ruts and smooth drum wheeldecrease with vertical loading increases. As slip ratio is smaller than30%,tractive effiencydecrease with vertical loading, the maximum value of tractive efficiency decrease with thevertical loading increases. The sinkage of the four wheels in the state of soft is larger thanthat in the state of nature. Driving torque, drawbar pull and tractive efficiency of smoothcylinder wheel and cylinder wheel with lugs in the state of nature are lager than those of soft. Driving torque of smooth drum wheel and drum wheel with lugs in the state of soft is largerthan that of nature. Drawbar pull of smooth drum wheel and drum wheel with lugs in thestate of nature is larger than that of soft. To the four wheels, the sinkage of the wheels withlungs is smaller than that of smooth wheel, and driving torque, drawbar pull and tractiveeffiency of the wheels with lugs are larger than those of amooth wheel.After summrizing the traditional terrainmechanics formulas, the research determines themechanical models which are fit to be modified. Aimming at sinkage and rolling resistancemodels, the influence of pressure characteristic parameters errors on the erros of sinkage androlling resistance is analyzed. The influence of n on the errors of sinkage and rollingresistance is larger thank candk on those within variaration range which the lunar rovercan work. The relative error of sinkage is16%, and confidence level is90%. The relativeerror of rolling resisitance is8%, and confidence level is96%. On the consideration of slipand the test errors of mechanical parameters, the research modifies the sinkage model androlling resistance model. Furthermore, the research need consider the shape of the wheelsand luggs when the models are modified. Based on ananlysis and the results, the modifiedmodels are given. The errors of sinkage is from1%—19.7%, the errors of rolling resistance is1.5%～19.9%.The research analyzes the relationship between smooth wheels and lunar soil simulants.The normal stresses and shear stresses which exist between the smooth cylinder wheel andlunar soil simulants increase with deformable index, friction modulus and radius of wheels,cohesive modulus and width of wheels have the little influence on normal stresses ans shearstresses, cohesion has little effect on shear stresses, shear sress increase with friction angle.The normal stresses and shear stresses increase when slip ratio decrease when comtact angleis between0and the value where the maximum normal stress. Between the contact valuewhere the maximum normal stress is and the maximum contact angle, the shear stressesincrease with slip ratio, but slip has no influence on shear stresses. The normal stresses andshear stress increase with sinkage and sinkage has larger influence on stresses.There must bea point whose absolute velocity is downward on the brim of the rigid wheel. If the point hascontact with lunar soil simulants, the lunar soil simulants apply bulldozing resistance on thewheel below the point, meanwhile, the lunar soil simulants exert additional traction on thewheel above the wheel. If the point has no contact with the lunar soil simulants, the lunarsoil simulans apply smaller bulldozing resistance on the wheel, meanwhile, a little traction is applied on the wheel. The position of the point has relation with slip ratio, vincreaseswith slip ratio. θ_vmin is increase with velocity and vertical loading decrease. The change ofθ_vmin is not large on the condition of low velocity, θ_vmin occurs when slip ratio changesfrom20%to30%.The research has simulation analysis on traction ability test which is in chapter2andchapter3after modeling on lunar soil stimulant by Druker-Prager constitutive model ofABAQUS and determining corresponding conditions. Simulation ruts and data are similar totest results, it represents that traction ability test of lunar wheels could be availably simulated.The research analyze the effect of lungs with three diffirent dimentions on traction ability oflunar wheels. The change of width of lugs have no influence on pattern, sinkage, drawbarpull and driving torque on the condition of light-loading and low velocity. As the height ofthe lugs increase, the lugs lift seriously rack the soil, sinkage and drawbar pull increase, butdriving torque has little change.更多还原