【作者】 陈斌；

【导师】 李建桥；

【作者基本信息】 吉林大学 ， 仿生科学与工程， 2010， 博士

【摘要】 月面环境下松软月壤是月球车车轮滑转、下陷而停滞不前的主要原因。因此,研究驱动轮与月壤间相互作用方式及其变化规律,对于提高月面探测车辆的通过性,从而保障月球车工作的可靠性具有重要意义。本文以火山灰和石英砂为主要原料制备了三种用于月面车辆试验用模拟月壤,利用研制的月壤—车轮土槽测试系统,对五种不同结构的月球车驱动轮在三种不同介质上的牵引特性进行对比试验,并分析不同车轮结构下模拟月壤的破坏失效形式、不同介质破坏形式、轮刺坑形状以及介质和车轮结构对车轮牵引性能的影响规律。分析了原始状态下模拟月壤圆锥指数(CI)分布情况,探究载荷及整备条件对CI值的影响规律,提出试验前模拟月壤一致性处理方法,在此基础上进行了被试刚性轮压痕试验和车轮压实土槽试验,根据车轮压痕面积、压痕深度以及车轮结构参数和行驶参数探讨车轮对模拟月壤CI值的影响,并计算了车辆圆锥指数作为评价月球车整车通过性指标和土壤—车轮系数作为评价月壤可行驶性指标。采用离散元方法细观分析了微重力环境下月壤力学参数变化对贯入阻力的影响规律和驱动轮结构参数,包括轮径、轮刺高度、轮刺宽度和轮刺数量对牵引性能的影响规律,并建立了车轮与模拟月壤相互作用有限元与离散元多尺度计算模型,在保证模拟精度的基础上,探讨提高模拟程序运算效率的途径。以上研究为月面探测车辆的驱动轮设计优化、模拟月壤一致性处理、原理样机通过性验证试验场地整备提供基础数据和测试方法。更多还原

【Abstract】 There are three parts in China lunar exploration namely detection around the moon, dropping to the moon surface and returning to the earth with samples respectively, and the lunar rover is an important equipment especially for the second part in Chang e lunar exploration project. Recently some academies and universities have developed different lunar rovers in China but the traffic ability research and the research on interaction between wheel and lunar soil is still at its infancy. Past research focused on the following parts: first, the kinds of lunar soil simulant are very single in terramechanics on moon making it hard to provide sufficient data in designing the walking mechanism of lunar rover, second, most researches are on investigation of the traction of single driving wheel, thus the lunar soil factor is ignored in the interaction between wheel and lunar soil, third, the research on how to ensure the lunar soil uniformity in every experiment is not done, and the research on the influence of structure parameters and driving parameters to lunar soil cone index is also not done. Overally, the evaluation standard on trafficability characteristic of the whole lunar rover is not established. So there is need for a further study aiming at the aforementioned problem. This work will complement well research on the interaction between wheel and lunar soil.The authors are grateful for the financial support by the Key Project of Chinese Ministry of Education (No. 107035) and the Key Project of Chinese National Natural Science(No. 50875107), the Corporative Project with The aerospace system engineering Shanghai and China Aerospace Science and Technology Corporation, and the 985 Project of Jilin University.The research contents included the following aspects. First, the research simulates three kinds of lunar soil for the lunar terramechanics test, develops the soil bin equipment and designs five kinds of wheels for lunar rover, and based on the soil bin test in laboratory, research on the traction ability of the lunar rover is done. Second, the research analyses the cone index of lunar soil simulant. It includs the distribution of cone index of lunar soil simulant in original state, the influence of soil treatment to the cone index of lunar soil simulant such as shaking press soil velocity, loosing soil velocity and blading soil velocity, the influence of structure parameters and running condition of rigid wheel to cone index of lunar soil simulant. Third, the research provids mobility index and vehicle cone index as evaluation of lunar rover passing ability, and the clay-tire numeric as lunar soil traffic ability evaluation. Finally, the research uses the DEM (Discrete Element Method) software to simulate soil bin test and observes the lunar soil particles changing under micro-gravity. The test includes two parts. First, the influence of lunar soil mechanical parameters to penetration resistance is analyzed based on the result of cone penetration test. Second, the influence of driving wheel’s parameters structure to traction property. The DEM simulation test reveals the relationship between wheel and lunar soil under micro-gravity. The continuum/discontinuum multiscale analytical system of the interaction between rigid wheel and lunar soil by coupling discrete elements and matrix module is established based on it, and it has the much higher computation efficiency.Three lunar soil simulants are used during the test. They are named as follows: Soil sample1: The basic material of this lunar soil simulant is the eruption that was mined from Jingyu district, Jilin province. This lunar soil simulant is red, powdery after drying and milling. Soil sample2: this lunar soil simulant is prepared by Jilin University and is black. Soil sample3: quartz sand that was mined from Shouling district, Hebei province. It can be used in wear experiment, and is white. The parameters of soil sample 2 are within the expected range of lunar soil after analyzing, and are close to those of JSC-1.The research has analyzed how to ensure that the lunar soil is uniform in every experiment. The test result shows that the cone index of lunar soil simulant is dispersed, and the fluctuation range of cone index ranges by 20%. The cone index of lunar soil simulant is divided into three sections: surface stable section, media fluctuation section and deep stable section. The loosing soil velocity and blading soil velocity have influence on cone index of lunar soil simulant. The length of surface stable section increases with the growth of blading soil velocity and loosing soil velocity, and this phenomenon is explained from two aspects: gravity and particle fluidity.Through experiment, the influence of quasi-static load to the length and the average cone index value of surface stable section. The regression equation was established, which is y = 0. 00327x+9.12and y = 0. 037x+773.28, the significance levels of two equations are 0.01, and confience level is 99%.The passing ability of six-wheeled suspension system lunar rover is analyzed by calculating mobility index and vehicle cone index, and the test result shows that the six-wheeled suspension system lunar rover has higher passing ability with teeth-wheel. The test results show that with the growth of contact area between wheel and lunar soil, the compact is decreased to luar soil. it can reduce the rolling resistance, and the grouse pass through the weak surface of lunar soil, and interact with deep particle, which can improce thrust force.Through caculating the tire-clay factor of stimulant lunar soil and sandy, the regression equation is established, which is y = 0 .183lnx?0.376and y = 0. 101lnx?0.202, the significance levels of two equations are 0.05, and confience level is 95%.the test result shows that the traction performance of wheel when it passes soil sample 2 is higher than soil sample 3. The drawbar coefficient of wheel is to increase with the growth of the clay-tire numeric, and increasing range is from 27.3% to 68.4% when the clay-tire is under 80.The research introduces the DEM to terra-mechanics because the DEM is more feasible and superior to the FEM in simulating the interaction between the wheel and the lunar soil. The penetration test is simulated by the PFC2D, too. The simulant result is different from soil bin test result, which could be caused by the difference between 2D and 3D to simulant test and the lunar soil simulant particles in the soil bin are affected by particle fluidity and earth gravity. This simulant test also studies the influence of the friction coefficient, density and penetration velocity to penetration resistance. The result of the simulation test shows that penetration resistance increases with the increase of the friction coefficient, density and penetration velocity. The fiction coefficient changes particles friction force and density changes the particle number contact with hardness instrument. The penetration velocity affects the moving time of hardness instrument, which causes the increase of the penetration force, and that causes obvious difference with soil bin test result, but it is limited by PFC2D.Soil–wheel interaction especially soil deformation caused by the wheel motion is investigated by PFC2D simulation. Characteristics of lunar soil deformation are summarized focusing on the behavior of displacement and distribution of velocity. The results show that the force on the wheel concentrates in the grouser of wheel, and it is described by thrust force in horizontal direction and lifting force in vertical direction. The sinkage of wheel is mainly caused by grouser effect, and it contains two aspects: wheel-spin sinkage and penetration sinkage. Shapes of the velocity distribution in simulation have onward flow area and back flow area, which is divided by critical point. The relative velocity of wheel has the same direction with the horizontal velocity of particles before critical point that causes horizontal force to push lunar soil particles forward, and the direction is opposite behind critical point that adds thrust to push lunar soil particles backward. The influence of wheel structure parameters to traction performance of wheel is studied by experimental optimum design. The test results show that the DP increases with the increase of wheel diameter, and sinkage reduces. The DP and sinkage increase with the increase of the length and width of grouser. The DP and sinkage have cyclical fluctuation with the increase of number of grouser. The wheel structure parameters are optimized by orthogonal test. The results show that increase of wheel diameter has good effect on improving the DP, and it determins the factors and optimal combination that affecting DP, which is A>B>C>D and A3B3C1D2. According to optimization test, the DP can reach up to 135.21N when the wheel diameter is 300mm, the wheel height is 20mm, the wheel width is 5mm, and the number of wheel grouser is 18.Based on DEM software PFC2D?, the continuum/discontinuum multiscale analytical system of the interaction between rigid wheel and lunar soil by coupling discrete elements and matrix module is proposed. Through comparing particles’equilibrium time using the multiscale model and the DEM model when balancing stress and dissipating energy among particles, it can be seen that the multiscale numerical model can greatly save time. Through a kind of driving wheel-soil bin test using two numerical models, and comparing the simulation results with the soil-bin test results, the high accuracy and the computation efficiency of the multiscale model are validated.更多还原