【作者】 陈斌；

【导师】 李建桥；

【作者基本信息】 吉林大学 ， 农业机械化工程， 2007， 硕士

【摘要】 2004年,我国正式启动“嫦娥工程”,这标志着我国正式开展对月球的探测活动,作为了解月球最直接的一种方法是将月球探测车送上月球,通过其在月面的实际行走和采集月表的土壤样品等勘探作业,获取其地形、地貌、矿产资源信息,因此以刚性轮为接地部件的月球探测车必须能够适应复杂的月球地形环境、具有良好越障通过性,以保证月球车探测车能够完成各种任务。月球探测车通过各种地面和地形的能力包括支承通过性和越障通过性。支承通过性指在松软土壤上可靠行驶的性能,该性能取决于月球土壤性能;越障通过性指克服几何障碍(如垂直台阶、弹坑、壕沟)的性能,该性能与月球探测车的车轮结构密切相关。本文根据地面车辆力学的相关理论对刚性车轮与沙土相互作用的力学特性和试验方法进行了深入的分析和研究。本文阐述了月壤的物理及力学特性,并在力学特性中引入了月壤的承压、剪切力学模型,同时进行了试验用土的剪切试验,测量了试验用土的内聚力、内摩擦角、含水量和孔隙比等参数。参照地面车辆系统的研究方法,对月球车车轮进行了动力学分析,并建立了刚性轮在月面行驶时的挂钩牵引力模型,并得出了刚性轮的径宽比是影响其挂钩牵引力的重要因素。对试验所需月球车车轮性能测试系统,机械结构及驱动电机及主要传感器进行设计及选择。利用该设备进行了试验分析,选用正交试验优化设计方法,考察径宽比、垂直载荷和水平速度对挂钩牵引力的影响。试验结果表明,影响挂钩牵引力的影响因素依次是:径宽比,水平速度,垂直载荷;刚性轮的挂钩牵引力随径宽比增加而增加;分析试验结果得到了刚性轮挂钩牵引力随各因素的变化规律。利用有限元分析软件ANSYS,对刚性轮与沙土相互作用过程进行了三维有限元模拟分析。从接触应力和位移矢量等角度,进一步揭示了大径宽比的刚性轮具有较小的行驶阻力,从而为月球车通过性能的提高提供了设计依据和模拟试验方法。更多还原

【Abstract】 Lunar rover, named planet detect robot, can proceed long-term practical exploration in place of the astronaut. But lunar rover do not hold enough traversing ability to ensure its normal work,when driving in the lax road. Generally, it can cross obstacles which height of these is smaller than the diameter of carwheel, and only step over the deep ditch which width of it do not exceed the diameter of wheel.Thus it can be seen, the performance of the lunar rover depends mostly on the performance of the lunar rover’s wheel.So it is important to study the mechanical performance of the wheel of lunar rover. Now some universities and institutes of China have made some samples of the lunar rovers and theirs wheels, but until now the wheel’s mechanical performance is seldom researched and tested. The paper is organized as follows:Firstly , introducing various index of describing its physical characteristic then the mechanical characters of the soil are separated to press-sinkage character and shear character based on Bekker’s theory, and common press- sinkage and shear models are introduced. These basic theories are helpful to construct the rigid wheel with sandy soil model. Some parameters of soil used for experiments are measured by shear experiments .By passing to check against, its various parameter indexs are close to lunar soil, it can be used for experimenting.The tractive trust is one of the key factors of vehicle moving. Based on the confirming drawbar pull of lunar rover, using related theories of the ground mechanics and the soil mechanics, I analyze various resistance and driving force of its subjecting to when the lunar rover driving on the surface of the moon. Finally I build the lunar rover dynamics model, then I have a conclusion that drawbar pull relate to the ratio of diameter to width of wheel.To study the performance of the wheel further, we design a test-bed. This test system can measure the followed mechanics parameters: drawbar pull、torgue and sinkage etc. at the same time try to imitate the lunar rover have the ability of crossing obstacle and come through various ground and geography normally, under the moon environment.This system has the function of the changed angle.It can measure the biggest angle of the slope that the lunar rover overcome upgrades.According to above design request, we have chosen the electrical motor and the direction electrical motor. Based on displacement and drawbar pull, we select displacement sensor and pull/press sensor and checked the driving capability and the distance demand .Experiment shows that the sensor can satisfy the performance requirement.Orthogonal test optimization is adopted in the rigid wheel passing ability test, which the primary and secondary factor is the ratio of diameter to width of wheel, the level speed and the load. I get the optimal combination is ratio of diameter to width of wheel is 3, speed at 3.6m/min and plumb load is 30N. One equation was obtained based on the one factor regression experiment. The rigid wheel equation between ratio of diameter to width of wheel and drawbar pull is: y = -11.758x2 + 81.729x - 58.512. Concluded by the orthogonal experiment, the quadratic equation between drawbar pull and these three factors was: y=-2.39+1.882Z1-0.03Z2+0.053Z3-0.006Z1Z2 -0.003Z1Z3-0.001Z2Z3-0.33Z12+0.001Z22Using ANSYS software to analyze three dimensional finite element model of rigid wheel and sandy soil contacting process. This method cannot only provide physical parameters that cannot be measured in experiments, but also modify the parameters of structure and movement conveniently. The method can shorten the development period of lunar rover and improve the testing technique. ANSYS simulation involves three parts: modeling, solution and analysis. The model of the contact of the rigid wheel with sandy soil was established after Studying on the interaction between rigid wheel and sandy soil. Element type, material and same parameters were defined. The model was meshed, limited conditions were added and resolution parameters were setup. Afterwards, the procedure of the contact of the rigid wheel with sandy soil was simulated. The simulation result was analyzed through powerful postprocess functions. 3D stress nephogram and Y direction stress curve through the path node for the driving soil were obtained. The simulating results showed that: the average stress on 200x100 rigid wheel surface was 0.251 KPa, the average stress on 250x200 rigid wheel surface was 0.267 KPa and the average stress on 300x100 rigid wheel surface was 0.238 KPa. The stress of the bigger rigid wheel with ratio of diameter to width of wheel reduced 10%coKParing with the smaller one. This shows the bigger rigid wheel can decrease rolling resistance and be helpful to lead sandy soil movement under moving lunar rover, which is useful to improve lunar rover trafficability.更多还原