Meng Zou

Effects of Load Type on the Mechanical Properties of the JLU Series Lunar Soil Simulant

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.

Bionic Design for Reducing Adhesive Resistance of the Ridger Inspired by a Boar’s Head

The main feature of the boars head used to root around for food is the front part, which is similar to the ridger in terms of function, load, and environment. In this paper, the boars head was selected as the biological prototype for developing a new ridger. The point cloud of the head was captured by a 3D scanner, and then, the head surface was reconstructed using 3D coordinates. The characteristic curves of the front part of the boars head were extracted, and then, five cross-sectional curves and one vertical section curve were fitted. Based on the fitted curves, five kinds of bionic ridgers were designed. The penetrating resistances of the bionic ridgers and traditional ridger were tested at different speeds in an indoor soil bin. The test results showed that bionic ridger B had the best penetrating resistance reduction ratio of 16.67% at 4.2 km/h velocity. In order to further evaluate the performance of the best bionic ridger (bionic ridger B), both the bionic ridger and traditional ridger were tested in a field under the same working conditions. The field results indicate that the bionic ridger reduces penetrating resistance by 6.91% compared to the traditional ridger, and the test results validate that the bionic ridger has an effect on reducing penetrating resistance.

An Experimental Study on the Gait Patterns and Kinematics of Chinese Mitten Crabs

Despite the many studies on eight-legged animals and the importance of their mechanics of terrestrial locomotion, the mechanical energy of crabs in voluntary locomotion on uneven, unpredictable terrain surfaces has received little attention thus far. In this paper, motion video images of Chinese mitten crab (Eriocheir sinensis Milne-Edwards) locomotion on five types of terrains were recorded using a high-speed three-dimensional (3D) recording video system. The typical variables of locomotion such as gait patterns, duty factor, mechanical energy of the mass center, mass-specific rate of the total mechanical power of the mass center, and percentage recovery, were analyzed. Results show that the Chinese mitten crab uses random gaits instead of the alternating tetrapod gait with the increasing terrain roughness. The duty factors of the rows of the leading legs are greater for all terrains than those of the rows of the trailing legs. On smooth terrain, the duty factors of the rows of the trailing legs are greater than that on rough terrains. Kinematic measurements and calculations reveal that similar to mammals, birds, and arthropods, the Chinese mitten crab uses two fundamental gaits to save mechanical energy: the inverted pendulum gait and the bouncing gait. The bouncing gait is the main pattern of mechanical energy conservation. The low probability of injury and energy expenditure due to adaptations to various terrains induce the Chinese mitten crab to modify the mass-specific rate of the total mechanical power of the mass center. The statistical results of percentage recovery also reveal that the Chinese mitten crab has lower energy recovery efficiency over rough terrains compared with smooth terrains.

Pressure-Bearing Parameter Identification for Martian Soil Based on a Terramechanics Model and Genetic Algorithm

AbstractA wheel-terrain interaction mechanics model based on terramechanics and simplified force and moment reconstruction is introduced. The model comprises pressure-bearing parameters (combined d...

Experimental Study of Torque Using a Small Scoop on the Lunar Surface

Chinese missions to the moon are planned to sample the regolith and return it to the earth. Microscale excavators may be good candidates for these missions, as they would significantly reduce the launch mass. Thus, it is necessary to research the interaction between the scoop and the regolith being sampled. We present the development of a simple apparatus to measure excavation torque. All tests were conducted using TYII-2 regolith simulant with gravels. The test results show that, under loose regolith conditions, the penetrating angle and the bulk density had a great influence on the excavation torque, while the rotating speed had little effect. However, when the bulk density was compact, the rotating speed did influence the excavation torque. The excavation torque increased sharply when the scoop encountered the gravels; actually, some of the parameters will influence the value of the torque such as the diameter, quantity, and position and inbuilt depth of the gravels. When the excavation torque sharply increases, the operation should be immediately stopped and checked.

The Liquid and Plastic Limit Data Treated System Based on VC

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.

Mechanics of Locomotion Energetics in Chinese Mitten Crab Eriocheir sinensis Milne-Edwards

The study on the locomotion mechanism in laboratory has defined performance limits for animals presently. But it is more significant for investigating mechanics of animals in their free state. In order to study the locomotion properties of Chinese mitten crabs Eriocheir sinensis Milne-Edwards on one flat terrain and four kinds of rough terrains, a high speed 3-D video recording system was used to record motion video images of crabs. The gait pattern, average speeds, the mechanical energy of the mass center and percentage energy recovery were investigated with motion analysis system. The results showed that Chinese mitten crabs used alternating tetrapod gait on flat terrain and with increasing of terrain roughness, the regularity of gait tend to be less conspicuous. Crabs used two fundamental models of energy exchanging patterns: the inverted pendulum gait and the bouncing gait and the bouncing gait was the main energy saving and conserving pattern. Keywords-biomechanics, Chinese mitten crab, rough terrain, gait, mechanical energy, percentage energy recovery

Experimental Study of Hygroscopicity of Lunar Soil Simulant

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.

Development of Experimental-Bed for Observation of Locomotory Small Animals

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.

Tests on Effect of Gravity and Soil Density on Soil Cone Index

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.