Journal of Terramechanics最新文献

In order to study the effect of contact length of tire on tractive performance of tractor, experiments were conducted using a single wheel tester fitted with 13.6–28 bias ply tire in a soil bin in soft soil condition. Contact length and contact width were measured at different normal loads (9.8 kN and 13.72 kN) and inflation pressures (83, 103, 124 and 138 kPa). Results showed that the contact length had higher influence on tire pulling ability and tractive efficiency as compared to contact width of the tire. An equation for predicting contact length was developed using XLSTAT software, with normal load and inflation pressure as an independent variables and contact length as a dependent variable. The model demonstrated high efficiency with a coefficient of determination (R²) 0.96, a percentage of variation 0.76 %, a root mean square error 10.841, and an adjusted R² 0.95. Additionally, a second-order polynomial equation was developed using curve fitter app to estimate drawbar pull of a tractor by keeping wheel slip and contact length as independent parameters. Validation with another set of data obtained for 14.6–28 tire yielded R² 0.93 and less than 4 % variation, thus indicated the model’s accuracy in predicting drawbar pull.

Legged robots exhibit superior adaptability to complex extraterrestrial environments compared to wheeled mobile robots. However, legged robots employed in planetary exploration face challenges in dealing with soft terrains. This paper focuses on investigating the issues of large foot sinkage and slip encountered by legged robots on soft terrain. Extensive experiments on quasi-static loading, loading with impact and tangential force have been carried out for both spherical and cylindrical feet. The variations in normal force, tangential force, and sinkage are meticulously recorded and analyzed. Foot-terrain interaction mechanics models are established to address scenarios involving substantial sinkage and sliding sinkage, leveraging the stress distribution characteristics of deformable soil. Accurate models are obtained through parameter identification utilizing experimental data, which can aid in the foot design of legged robots intended for planetary exploration. Based on the developed models and experimental data, a design optimization scheme for the coronal foot is proposed, leading to performance enhancements that are validated through experimental verification.

We propose a framework for discrete scientific data compression based on the tensor-train (TT) decomposition. Our approach is tailored to handle unstructured output data from discrete element method (DEM) simulations, demonstrating its effectiveness in compressing both raw (e.g. particle position and velocity) and derived (e.g. stress and strain) datasets. We show that geometry-driven “tensorization” coupled with the TT decomposition (known as quantized TT) yields a hierarchical compression scheme, achieving high compression ratios for key variables in these DEM datasets.

Vertical-axis rotary tillers are preferred over other soil-engaging tools for inter-culture operations due to their superiority in avoiding tillage pan formation, facilitating drainage, and operability at higher forward speeds. To optimize their design and operation, and to promote sustainable agricultural practices, a greater understanding of the kinematics, dynamics, and soil-structure interaction of vertical axis rotary tiller is required, along with the optimization of required energy. In this study, discrete element method (DEM) is used to analyse the interaction between soil and rotor blades, by incorporating the Hysteric Spring Contact Model along with linear cohesion model v2. Soil-rotor blade interaction DEM model is developed using Altair® EDEM® to analyse the effect of u/v ratio (2.13, 2.90, 3.70, and 4.44) and average operating depth (30 mm, 50 mm, and 70 mm) on draft and torque requirements for the rotor blade, as well as experimentally validating the simulation in a soil bin. In this study, lower u/v ratios in vertical axis rotary tillers demand higher torque for larger soil volumes. Additionally, torque rises with operating depth, owing to increased soil volume and strength. The simulated results closely followed the measured draft and torque for all combinations of u/v ratio and operating depth (R² 0.96 and 0.99). These findings indicate the DEM model as a dependable approach for modelling the performance of rotary tillers under different soil conditions.

Traditional plowing efficiency control methods are difficult to balance the tillage efficiency and uniform plowing depth, and the impact of the motor temperature rise on the control accuracy cannot be ignored during electric tractor operations. Therefore, a plowing drag-adaptive operation control method considering the motor temperature rise was proposed for an electric tractor equipped with a sliding battery pack. Firstly, a field-oriented control model with temperature compensation for the PMSM was developed based on the obtained winding resistances and flux links at different temperatures. Then, the driving torque and battery displacement were regulated to adapt the drag variation by the fuzzy neural network algorithm, allowing joint control of the speed and slip rate, and the simulation analysis was performed. Finally, a field plowing test was conducted. The results showed that the traction efficiency is increased by 23.33 % compared with those without control, and when the motor temperature rises, it can be compensated for temperature to output the required torque accurately, and the average relative errors in both speed and slip rate are reduced. The proposed method can improve the slip and greatly enhance the plowing operational stability, which provided technical support for the automatic precision operation of electric tractors.

The working parameters of vibratory rollers have an important effect on the compaction quality. The traditional method of obtaining the best working parameters through field tests is time-consuming and laborious. In order to determine the best working parameters more conveniently and accurately, a mechanical-hydraulic-finite element co-simulation method is proposed in this paper. This method considers the effect of the hydraulic system on vibration compaction and makes the simulation result as close to the actual condition as possible. By analyzing the change of soil stress and settlement, the effect regulation of working parameters on compaction quality is obtained. The results show that the proposed co-simulation method can accurately reflect the real conditions, and the best compaction quality can be achieved when the walking speed is 3 km/h, the vibration frequency is 24 Hz, and the amplitude is 2.5 mm. The research provides a reference for improving the compaction quality and compacting-related simulation.

Planetary surface exploration rovers are required to have the ability to travel over uneven ground such as sandy or rocky terrain. In addition, to maintain long-term functionality under severe mass constraints, the rover must be highly reliable with a simple configuration. The reduction in the number of actuators will also contribute to a reduction in the number of electrical components involved and improve reliability. This paper proposes a lightweight and simple traveling and steering mechanism that combines a path-following system based on the difference in rotational speed of the left and right wheels when traveling in a curve and a passive Ackermann mechanism without an actuator, assuming a small exploration rover of a size and mass that can be mounted on a Japanese launch vehicle. We also propose a correction method to improve the path-following performance. We also developed a prototype wheeled rover of the target size and weight, and tested and evaluated the effectiveness of the proposed method in following the target path and overcoming obstacle on simulated soil.

Instrumented single tire soil bin testing was conducted on a rigid surface and artificial soil by vertically loading a radial tire (LT235/75R15) to two tire vertical loads (6 kN and 8 kN) inflated to three levels of tire inflation pressure (179, 241, and 283 kPa). Lowering the tire inflation pressure by 37 % resulted in 26 % (6 kN vertical load) and 39 % (8 kN vertical load) greater contact lengths (P < 0.05). The 2-D contact area on artificial soil (initial bulk density of 1.51 Mg/m³) was significantly affected (P < 0.05) by tire inflation pressure for each load case. Increasing the load significantly affected the tire’s contact length on soil (P = 0.0010); however, tire inflation pressure did not significantly affect the contact length on soil (P = 0.0609). Soil rut depth and tire-soil deformed volume were not significantly affected by vertical load and tire inflation pressure. Measured tire contact area on soil surface was 3.3 times the contact area on the rigid surface, suggesting tire-soil interaction interface properties on deformable soil are better than using the gross flat plate for evaluating low ground pressure tire technology effects on traction and reducing soil compaction.

Rubber tracked running gears are widely used in high-mobility Unmanned Ground Vehicles (UGV) to increase obstacle negotiation possibility in urban and rural terrain. The paper proposes a method of assessing the mobility level of the light UGV‘s tracked running gears in terms of their ability to overcome terrain obstacles. A model of rubber track system was created in the MSC ADAMS environment. A track-ground contact was also modeled, defining the traction force based on the Wong equations. For four different chassis models (rigid construction, bogies solution – rigid and elastically mounted to the frame and rocker-bogie construction), with two track tension variants, the ability to overcome five terrain obstacles was checked, taking into account three different types of soil. The solutions were accessed on the basis of parameters of general efficiency of overcoming obstacles, driving force and slip values, as well as the distribution of track pressures on the ground. The best solutions for each criterion were indicated. The simulation results showed an improvement in the driving properties with the use of elastically suspended elements. The results also emphasized the negative impact of increased track tension on overcoming obstacles and the impact of ground characteristics on the slip values of the running gear.