Journal of Terramechanics最新文献

The discrete element method has recently become a popular tool for developing soil models to be used for modelling the tillage process, which involves using working tools. The research aims to evaluate the parameters of the contact model particles when modelling tillage with large–sized working tools using the discrete element method. The paper presents the results of calibration of the physico-mechanical parameters of the particles of the soil environment model described using the discrete element method. The model is used for modelling the tillage process using moldboard plow. The parameters of the simulated particles to be studied are the Poisson's ratio, coefficients of static and dynamic friction of particles, Young's modulus, surface energy, particles' diameter, coefficients of static and dynamic metal friction of particles. Calibration was carried out according to the horizontal, vertical and transverse components of the traction resistance of the plow body. The obtained dependences of the components of the plow body traction resistance on soil moisture and surface energy help select parameters for the Hertz-Mindlin contact model while modelling the behavior of the soil environment when interacting with the working tools of tillage and sowing machines.

Elucidation of power characteristics of an unmanned tracked vehicle for autonomous transportation of agricultural payloads in greenhouse constructions leads to appearance of an applied research in this study. This novel aim has been chosen based on operational requirement of the vehicle. Hence, it can be highlighted that this paper is initiative study described results of power efficiencies (motion, slip, and tractive power efficiencies) of the vehicle. To this aim, various payloads mounted on a trailer (1–5 kN) were towed by the vehicle through diverse drive speeds (0.17–0.5 m/s). Results illuminate that vehicle drive speed and payload weight had consequential contribution to vehicle motion and tractive power efficiencies. While, vehicle slip power efficiency mainly depended on payload weight. Linear regression approximations demonstrate that dual cumulative contributory effect of the drive speed and payload weight on the motion power efficiency (84.98–97.69 %) and tractive power efficiency (78.62–92.92 %) was antagonist and synergetic, respectively. Meanwhile, the slip power efficiency (81.71–98.36 %) linearly dropped with augmentation of payload weight. Resultant slip and motion power inefficiency were associate with vehicle motion power loss in amplitude of 0.39–67.98 and 2.65–14.03 W, respectively. Consequently, tractive power inefficiency was associate with vehicle motion power loss in amplitude of 3.15–82.01 W. This amplitude spotlights that 3.35–43.62 % of vehicle motion power inevitably wasted inside track-surface interface in agricultural towing tasks. Overall, numerical and analytical descriptions of the results as well as practical suggestions provide appropriate guidelines for vehicle supervisor in order to optimize power characteristics.

Machine learning (ML) models are developed to predict draft for mouldboard ploughs operating in sandy-clay-loam soil. The draft of tillage tools is influenced by soil cone-index, tillage-depth, and operating-speed. We used a three-point hitch dynamometer to measure draft force, a cone penetrometer for soil cone-index, rotary potentiometers for tillage-depth, and proximity sensors for operating-speed. Draft requirements were experimentally measured for a two-bottom mouldboard plough at three different tillage-depths and various operating-speeds. We developed prediction models using recent ML algorithms, including Linear-Regression, Ridge-Regression, Support-Vector-Machines, Decision-Trees, k-Nearest-Neighbours, Random-Forests, Adaptive-Boosting, Gradient-Boosting-Regression, Light-Gradient-Boosting-Machine, and Categorical-Boosting. These models were trained and tested using a dataset of field measurements including soil cone-index, tillage-depth, operating-speed, and corresponding draft values. We compared the measured draft with the commonly used ASABE model, which resulted in an R² of 0.62. Our ML models outperformed the ASABE model with significantly better performance. The test data set achieved R² values ranging from 0.906 to 0.983. These results demonstrate that the developed ML models effectively capture the complex nonlinear relationship between input parameters and draft of mouldboard plough.

Soil compaction is one of the major problems in modern agriculture. Thus, the workability of a soil reflects to its ability to accept the traffic of agricultural machinery and implements. Water content and compaction are factors that influence the rheological behavior of the soil. the representation of soil shows limitations regarding the behavior of the tire-soil interface and its resistance to deformation is both influenced by the different forms of loading application along a tire path on a soil particle. This paper presents a study of the impact of multiple wheel passage, the wheel velocity, and the weight applied to the wheel on the agricultural soil represented by the cone index. To do this, we were inspired to launch an investigation for soil compaction determination at three levels of wheel load, three levels of velocity and at tillage, first, second and third passages of wheel with three replications on clayey sandy mixed grain soil. The results of this study shows that the greatest soil compaction occurred at the highest wheel load (1000 N), the lowest speed (0.1 m/s) and the highest number of passes (third pass), this leads to minimize multiple passes and or follow the same path, also, keeping the load on the ground as low as possible (weight of the machines), and working at high speed in agricultural fields.

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.