Journal of Terramechanics最新文献

Previously developed terramechanics models of wheel-soil interaction forces do not cover the full span of possible wheel states, including large slip angles and ratios. This paper synthesizes a model that covers the full range of slip and skid ratios and slip angles by building on classic terramechanics and soil failure models. The need for wheel and soil specific tuning is reduced through use of a closed-form model of soil flow around the wheel to determine the wheel-soil contact geometry. The terramechanics model is validated both with and without the soil flow model on two wheels in sand for slip ratios from −1 to 0.9 and slip angles from 0$°$ to 60$°$, showing good prediction of tractive forces, sidewall forces, and sinkage over a wide variety of states. The data from these experiments is also presented, as the only open source data set to cover both a high range of slip angles and slip ratios.

The interaction between soil and tire is a complex phenomenon influenced by various factors, such as soil properties, vertical load on the wheel, and tire characteristics. However, estimating stress at the tire-soil interface is a challenging task due to the unpredictable nature of soil. Existing models for investigating the wheel-soil interaction are based on soil mechanical parameters, which are highly variable and require significant time and resources to measure accurately. In contrast, the amount of wheel sinkage into the soil can be measured in real-time and is derived from the mechanical properties of the soil. Therefore, there is a need to establish a relationship between stress and wheel characteristics such as dynamic contact length and tire sinkage in soil. To address this issue, this study introduces an analytical method to estimate the dynamic contact surface between the tire and soil. A mathematical model is then proposed to estimate stress, assuming the contact surface and variable pressure at the interface between the soil and tire. The stress model is validated through experimental tests conducted at three different vertical load levels and four different wheel traffic levels in the soil bin, repeated three times.

In the article, a model for predicting the energy losses caused by the flexural vibrations of rubber tracks, rubber belts, and rubber-bushed metal link-tracks for off-road vehicles is proposed, and a test stand and an experimental procedure are developed to identify the mechanical parameters of this model. The track or belt is represented by a chain of discrete rigid links connected by revolute joints, and a discrete spring-element is placed in parallel with multiple Maxwell-elements in each joint to capture the flexural rigidity and damping of the real track or belt. The mechanical parameters of the joint are found by testing real tracks or belts under cyclic bending. The models consisting of three, four, or five Maxwell-elements per joint are the most successful in predicting the response of a sample rubber track to cyclic bending. The spring-damping properties of tracks and belts identified with the method discussed herein can be applied in simulation studies on the interaction of tracked vehicles and soil. Furthermore, vehicle elements such as rubber bushings for suspension systems, rubber torsion springs, and oil-filled and rubber torsion dampers can be tested with this method to find their spring-damping properties required by vehicle dynamics simulations.

Sliding plate has the problems of large sliding resistance and serious soil adhesion. Loach moves freely and flexibly in mud, has highly efficient lubrication and drag reduction effects. The sliding plate of rice direct seeding machine was selected as the research object and loach as the bionic prototype. The macroscopic and microscopic structure characteristics of loach were observed, the body surface of loach was covered by scales, which had a ridged non-smooth structure. The simulation analysis of the drag reduction performance of the non-smooth structure was carried out, the maximum drag reduction rate was 2.55% at the speed of 1 m/s. A bionic sliding plate of rice direct-seeding machine was constructed based on the non-smooth structure of loach body surface, and its working performance was simulated and analyzed. The results of orthogonal test show that the order of primary and secondary factors of bionic structure parameters affecting drag reduction rate was ribbed spacing > ribbed width > ribbed height. The optimal parameter combination was ribbing height 4 mm, ribbing width 4.5 mm, ribbing spacing, and the optimal drag reduction rate was 4.21%. The results of this study can provide theoretical support for bionic design of soil-engaging components in wet and soft paddy field.

Push–pull locomotion is an effective mobility mode for traversing loose lunar regolith and climbing sandy slopes. A rover with an active suspension can generate thrust from a set of anchored wheels by adjusting its wheelbase while driving the remaining wheels. This paper explores the relationship between the velocities of the rotational and translational suspension elements. Using a kinematic slip greater than 30%–40%, inchworming surpasses both the travel velocity and power efficiency of normal driving on slopes between 10°–20°. On a 20°slope, inchworming improves travel reduction from 98% to 85% and reduces normalized power consumption by a factor of eight. Experiments with NASA’s upcoming Volatiles Investigating Polar Exploration Rover show that increasing kinematic slip increases its travel velocity in a sink tank by 35%. Models using granular resistive force theory indicate that wheels driving at higher slip can generate greater tractive force and thus reduce the load on the anchored wheels. Otherwise, at lower driving slip, the load capacity of anchored wheels may be exceeded and result in oscillatory overall travel. These experiments suggest that there is further room to improve wheeled locomotion by intentionally inducing wheel slip, especially in articulated suspensions.

This paper provides a comprehensive review of the published literature on screw propulsion for off-road vehicles and amphibious transportation, from its origins in the 18th century to the present day. Additionally, this work describes the basis and elements of an archimedean scroll propulsion mechanism and discusses the most developed dynamic models available in the literature and their limitations. The paper also examines the need for a tested terramechanics dynamic model and explores potential future applications of screw propulsion technology for uncrewed ground vehicles and robotic planetary exploration.

Scene information plays a crucial role in motion control, attitude perception, and path planning for wheeled planetary rovers (WPRs). Terrain recognition is the fundamental component of scene recognition. Due to the rich information, visual sensors are usually used in terrain classification. However, teleoperation delay prevents WPRs from using visual information efficiently. End-to-end learning method of deep learning (DL) that does not need complex image preprocessing was proposed to deal with this issue. This paper first built a terrain dataset (consists of loose sand, bedrock, small rock, large rock, and outcrop) using real Mars images to directly support You Only Look Once (YOLOv5) to test its performance on terrain classification. Because the capability of end-to-end training scheme is positively correlated with dataset, the performance of YOLOv5 can be significantly improved by exploiting orders of magnitude more data. The best combination of hyperparameters and models was achieved by slightly tuning YOLOv5, and data augmentation was also applied to optimize its accuracy. Furthermore, its performance was compared with two other end-to-end network architectures. Deep learning algorithms can be used in the future planetary exploration missions, such as WPRs autonomy improvement, traversability analysis, and avoiding getting trapped.

Discrete element modelling (DEM) is widely used to estimate soil-tool interaction and tillage forces. To run an accurate simulation, it is essential to determine the appropriate DEM contact model and parameters. Although previous work has been introduced to determine the DEM contact model and parameters, the accuracy of numerical simulation is not high because of the soil differences when tillage tools operate in cohesion and adhesion soil in the middle and lower reaches of the Yangtze River in China. In this paper a Hertz-Mindlin with JKR Cohesion contact model and Linear Cohesion contact model were used to predict soil disturbance area and draft forces. The DEM parameters were determined using cone penetration, and uniaxial unconfined compression as an assisted test. The field experiment using sweep tool was used to validate the simulation results. A good agreement has been showed between simulation results and experiment results. Using verified model, the relative error for the predicted soil disturbance area at speeds of 0.50, 0.75 and 1.00 m/s were 5.3, 3.6 and 7.1 %, respectively. The maximum and average relative errors between simulated and measured draft forces were 6.98 and 3.91%, respectively. The effect of tillage depth and speed at soil disturbance area and draft forces were found which can provide some guidance for the selection of parameters during actual operation.

It is a well-known phenomenon that the color of sand changes due to moisture. As the moisture content increases, the sand will typically become darker. In our research, we are looking for the answer to the exact function according to which this darkening process changes and what relationship there may be between the different, initial (dry) soil colors and how this relationship can influence the evolution of the darkening process. Using the suitably chosen range of the color spectrum, we created a color parameter to characterize the color of the measured sandy soil, and then, in addition to determining the moisture content, we also looked for other uses of the color spectrum for sandy soil. Thus, based on the color spectrum and other input parameters, not only the moisture content can be calculated, but in the case of two components, the grain composition can also be determined.

A comprehensive plate-sinkage equation is necessary for the description of the load bearing capacity of soils. In the last century, several improvements to the existing equations were attempted but with limited success. The main aim of this paper is to verify, evaluate and develop a load bearing capacity theory of finite half space soil. Agricultural soils may be regarded as a finite half space in which the tilled soil layer is comparable to the loading diameter. Harder soil is found below the tilled soil layer and this hard soil can be considered as a rigid layer. A new consideration is the compacted cone-shaped zone developing under a loading device and its possible interaction with the rigid bottom surface. Theoretical and experimental investigations reported in this paper have shown that these approaches have facilitated deriving new relationships valid for finite half space. These include two independent variables and developing a dimensionless load bearing number. This paper introduces a new dimensionless plate-sinkage equation describing soil deformation in a general form.