Papers by Author: Jian Qiao Li

Abstract: The cone index is one of the important indicators that can describe the comprehensive physical characteristics of lunar regolith. Its closely related to the sink and sideslip of lunar rover and also has widely used in prediction the trafficability, adhesion property, tractive performance of lunar rover. Based on component method, a kind of low gravity simulator, the tiltable test-bed has been built. This study has got the stable low gravity along axial direction and measured the penetration resistance characteristics of JLU-2 in different gravity through tests. The results shows that the gravity environment has an obvious impact on the cone index of lunar soil simulant, CI values reduce with the decreasing of gravity environment. Namely, in the low gravity condition, it shows weaker resistance ability for a foreign object to penetrate into. The result has important application value of prepare, optimize and risk assessment in walking mechanism of lunar rover and the sampling mechanism.

Abstract: The animal experimental is a fundamental equipment for biomechanics experimental, which attached to electric shock instrument, oxygen analyser or high speed recording system. The animal experimental has an advantage that it offers a single environment excluded the interfere from natural regimes. In this paper, a small animal observation experimental-bed was developed based on C++. The interface of control program was developed using Visual Basic 6.0 and the COM port communication between SCM LM3S8962 and PC was developed based on C++ Builder 6.0. The velocities of belt of the small animal experimental can run according to line, sinusoidal curves, triangular wave curves and square wave curves. Moreover, the control program provides a combined velocity based on above curves for satisfy the sophisticated experiment of locomotory small animals.

Abstract: According to two standards for soil test methods with liquid and plastic limit combined test, a liquid and plastic limit data treated system was developed using object-oriented visual programming Microsoft Visual C++6.0 based on analytical method. The flow char indicated that programs of the system used select structure and its nested structure as main its algorithm. Contrasted with manual graphic method, the liquid and plastic limit data treated system had high efficiency and reliable accuracy.

Abstract: The lunar soil simulants using for vehicle-terramechanics research on the ground need to expose in air containing water molecules for a very long time. The influence of the engineering properties of lunar soil simulant caused by air moisture should be determined. This paper has obtained the moisture absorption of JLU-1, JLU-2 and SNJ-4 using weighing method. The result indicates that the hydroscopicity of three lunar soil simulant are: SNJ-4>JLU-2>JLU-1, all less than 2%. It shows that even in saturation state, the moisture content of three specimens is very little. The length of storage time of lunar soil simulant in natural environment has little effect on its engineering properties. Lunar soil simulant after be made can be storaged well for a long time in the natural environment, and used for ground foundation test. The results can supply the reference to evaluate the engineering properties and formulate the suitability standards of lunar soil simulant.

Abstract: It is important to research the relationship between the lunar wheel and lunar soil in the circumstances of lunar surface in order that the lunar rover can work efficiently. Distinct Element Method (DEM) is an ideal method to analyze the relationship between lunar wheel and lunar soil. In this work, a prediction model for rigid-wheel and lunar soil is proposed, and the DEM model for lunar soil is found by the biax-test. The results show that the values of the simulation parameters in lunar soil are close to that of the real lunar soil after adjusting the micro simulation parameters. The Bekker’s model is used to calculate the pressure-sinkage, and the Janosi model is used to describe the shear characteristics. The plate-sinkage-test as well as the shear-test was simulated by PFC2D. The parameters of terra-mechanics were calculated based on the least square method. In the simulation, the value of K is 1635 kN/mn+2, n is 1.22 and k is 1.35 cm. After that, the soil bin system is simulated by the software PFC2D. Further, the tractive test which is checked out by the soil bin test and model calculation was simulated in PFC2D. Finally, by comparing the traffic ability of the nonrug-wheel with the rug-wheel, the results show that the slip radio is 0.52 of the rug-wheel and 3.21% of the nonrug-wheel under the traction load. The draw-bar pull is 121.67 N in the rug-wheel compared that of 7.71 N in nonrug-wheel under the slip is 10%.This indicates the rug-wheel can generate greater draw-bar pull and show better traffic ability than the nonrug-wheel under enough torque condition.

Abstract: The pressure-sinkage characteristics and the shear-strength characteristics of lunar regolith are the important influence factors to the trafficability of lunar rover. The performance curves and parameters of JLU luanr soil simulant were obtained by pressure-sinkage tests and shear-strength tests in the ground gravity-environmental load (1g) and the lunar gravity-environmental load (1/6g). The results show that, for the pressure-sinkage characteristics, the compression-strength of the JLU-1 is strongest, followed by the JLU-3, and the JLU-2 is the weakest. In different load levels, the deformability index n increases as the bulk density increases. The kc increase as the state becoming more and more compact,The k of JLU-1 is the largest of all, followed by JLU-3 next, JLU-2 has the smallest.The load levels have no significant effect to the tendency of n, kc and k. For the shear-strength characteristics, the shear resistance of JLU-2 is the weakest. JLU-1 has the greatest cohesion c of the three lunar soil simulant, followed by JLU-3, the c of JLU-2 is the smallest.The c of the same lunar soil simulant in natural state is greater than it in soft state. Compared with JLU-1 and JLU-3, JLU-2 has the smallest internal friction angle .The influence of the load levels to the the cohesion c internal friction angel is not obvious. The  mesured in the lunar load is wider than it in the ground load. This study will supply fundamental reference and foundation on the research and optimization of the lunar rover traveling mechanism in the authentic lunar environment.

Abstract: The lunar surface is covered with the deposit of regolith which is loose and dry powder. In the earth condition, the mechanical properties of lunar soil simulant from eruption powder will greatly influence the precision and reliability of the rover test results. This article measures the parameters by means of the vertical load which is representing the pressure generated by vehicle wheel, and the formula of vertical pressure-sinkage relationship: p=[k_с/b+k_φ]*zⁿ. It was discussed that the value of n, k_с, k_φ changed under three different velocities and four different radiuses of circular plates. Because these parameters are sensitive to bulk density of lunar soil simulant, the paper could only discuss the range of k_сk_φ and n, and the results of the measurement are n= 0.698~ 1.123, k_с= 0.524~ 5.928, k_φ= 0.124~ 1.926. The lunar soil will make the poor trafficability for lunar rover. This article could provide basis and criterion for evaluation rover behavior at the surface of moon and design the wheel parameters of lunar rover.

Abstract: The powder with size distribution was made from eruption to be used for the simulant of lunar soil. One of the most important factors is shear property, to simulate lunar soil behavior under the rover wheels. Therefore, it is necessary to measure the shear parameters of the simulant. The direct shear detector with controlled sample weight was used for selecting suitable method to obtain the shear parameters of the simulant, and finding effect actors for the measurement. Results found that the parameters changed greatly with the powder bulk density (or unit weight), and the calibration was vitally important for measuring cohesion of the powder.

Abstract: The adhesion and the compressibility of the soft soil will vary as the earth gravity changes. In this study, the pressure-sinkage characteristics in low gravity conditions were investigated by three-dimensional Discrete Element Method (DEM). The data of the DEM parameters were obtained by analyzing the pressure-sinkage relationship embedded in laboratory testing data. The pressure-sinkage experiments of the sample soil in different gravities were simulated by using the software PFC3D. Using the Bekker formula, the values of pressure-sinkage parameters were obtained. The results show that, when the earth gravity changes from one sixth of the standard earth gravity to the standard earth gravity, the sinkage exponent increases lineally. The cohesive module of deformation increases along the conic trend. The low gravities have a sensitive affect on the data of the frictional module of deformation, and the data distribute beside a line. The change laws of the pressure-sinkage parameters provide instructions for the optimization design of vehicles working in low gravity field planet.

Abstract: The simulation system between smooth rigid wheel and lunar soil by Discrete Element Method (DEM) was established and validated. Three section structures of smooth rigid wheel, including flat, concave and convex structures were designed. The effects of these three different wheel section structures on dynamic mechanical behaviors of lunar soil simulant were simulated by PFC2D^®. The simulation results indicated that the concave section structure of smooth rigid wheel has the best anti-sinkage ability, the convex section structure has the good anti-sinkage ability, and the flat section structure has the worst anti-sinkage ability.