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[Display omitted] • Tillage involves soil mechanical disturbance, in order to improve its structure. • Agricultural production directly depends on the tillage quality. • Soil quality critically influence environment and the efficiency in crop production. • Present paper is focused to modelling the soil particle size distributions. • Important task of soil tillage is to reduce the soil compaction to minimum. Tillage involves various complex mechanisms of mechanical disturbance of the soil, aimed to advance its physical structure by creating relevant conditions for growing crops Quality regulation of every specific tillage conception is critical for the soil physical parameters. Thus, the main goal of this work was to review approaches to the analysis of the quality of soil cultivation techniques. Relationships have been established between the basic operating parameters of the mechanization applied and the consequent particle size spreading of the soil. Supplementary, statistical indices of the distribution pattern of soil particles, based on higher-order dimensionless statistical parameters were estimated. The observed mass distributions of soil aggregates was the result of extremely complex and superimposed influences of soil type, field conditions, crop structure, equipment used, etc. At this stage, an accurate forecast of the impact of soil tillage techniques on the changes in composition and size distribution of soil aggregates based on mathematical modelling is very difficult. Further research will be continued to include wider range of soil types, agricultural mechanization systems and their operational regimes. [ABSTRACT FROM AUTHOR]

• SSPM can be installed on tractors computers to increase safety of their operation. • This program estimates critical slope angles of mobile agricultural machines. • The algorithm combines principles of theoretical mechanics and analytical geometry. • Output results are represented in two manners: graphic and numerical. • The algorithm is verified by experiment with a tractor model. This paper presents an analytical algorithm with appropriate software specified for the approximation of the allowed critical slope of the solid flat terrain that guarantees static and/or dynamic stability of the specified self-propelled agricultural machines and their aggregates. This algorithm assumes machine as a rigid body, having 3 or 4 contact points (defined by wheels or crawlers), under uniform motion at different constant velocities and radii of curvature trajectories. Using this algorithm, based on the principles of theoretical mechanics combined with 3D analytical geometry, the computer program SSPM (s tability of the s elf- p ropelled agricultural m achines) has been coded. This software is intended to facilitate the analysis, comparison and optimization of different configurations of self-propelled agricultural machines in operation on horizontal and sloped flat terrains at constant velocities and radii of trajectory with respect to their static and dynamic stability. It calculates critical pitch and roll angles of the self-propelled machine and the maximum allowed slope of the flat terrain under the given conditions. The algorithm and the appropriate SSPM software were experimentally verified using the platform and low-scale tractor model. Average difference between calculated and experimental critical values of roll and pitch angles were about 4° [ABSTRACT FROM AUTHOR]

Abstract: The paper discusses the problems in identifying parameters characterizing the interaction of a tyre with different ground surfaces. Corresponding methods of tyre–surface contact monitoring are proposed on the basis of the fuzzy sets theory. Cases of a wheel rolling on both a road and on deformable ground are considered with particular emphasis on the identification of the friction and rolling resistance parameters in relation to environmental properties and tyre loading modes. The theory developed is illustrated by examples of cascade fuzzy observers using the off-board and on-board information space. To verify the proposed theoretical propositions, the work also contains the corresponding results of the hardware- and software-in-the-loop simulation. These fuzzy computing procedures can be used in various control systems of cars, off-road vehicles, and agricultural machines as well as in applications of Intelligent Transportation Systems. This paper is an extended version of the work “Identification and Prediction of Tyre–Surface Interaction Parameters” presented at the 16th ISTVS Conference. [Copyright &y& Elsevier]

Abstract: Mathematical models capable of describing the interaction between traction devices and soils have been effective in predicting the performance of off-road vehicles. Such a model capable of predicting the performance of bias-ply tires in agricultural soils was first developed by Brixius [Brixius WW. Traction prediction equations for bias-ply tires. ASAE Paper No. 871622. St. Joseph, MI: ASAE; 1987]. When the soil and vehicle parameters are known, this model uses an iterative procedure to predict the tractive performance of a vehicle including pull, tractive efficiency, and motion resistance. Al-Hamad et al. [Al-Hamad SA, Grisso RD, Zoz FM, Von Bargen K. Tractor performance spreadsheet for radial tires. Comput Electron Agr 1994:10(1):45–62] modified the Brixius equations to predict the performance of radial tires. Zoz and Grisso [Zoz, FM, Grisso RD. Traction and tractor performance. ASAE Distinguished Lecture Series #27. St. Joseph, MI: ASAE; 2003] have demonstrated that the use of spreadsheet templates is more efficient than the original iterative procedure used to predict the performance of 2WD and 4WD/MFWD tractors. As tractors equipped with rubber-tracks are becoming popular, it is important that we have the capability to predict the performance for off-road vehicles equipped with rubber-tracks during agricultural operations. This paper discusses the development of an empirical model to accomplish this goal and its validity by comparing the predicted results with published experimental results. [Copyright &y& Elsevier]

This publication series describes the development of the Hohenheim Tyre Model – an approach that considers the properties of high volume, agricultural tyres. The research project was conducted in accordance with the V-Model, which proposes a standardised development methodology for mechatronic systems. The previous publication described amongst others the model structure and parameterisation. This paper elucidates the validation, which is an essential part of the V-Model. Validation received special attention and is divided into three parts. First, three-dimensional tyre behaviour on level surfaces was investigated. Within the second step, single tyre behaviour is validated during obstacle passages. Similar obstacles were then used in the final step that shows up the correlation between measured and simulated whole vehicle behaviour. Throughout the validation a very high level of accuracy is achieved. [ABSTRACT FROM AUTHOR]

Fatigue life of agricultural machinery is strongly affected by the surfaces that these machines operate on. In the present paper a sensor-frame was developed to acquire road and field profiles in absolute geo-referenced coordinates. The sensor-frame was validated by measuring discrete trapezoidal bumps with known dimensions resulting in a root mean squared (RMS) error of 6–8 mm. Profiles were acquired from a country road and from a mowed grass field. Using the quarter-car vehicle model, the movement of an agricultural vehicle was simulated for various speeds. The resulted vertical loads were rainflow-counted and the accumulated fatigue pseudo damage was calculated using Palmgren–Miner linear rule. Based on the derived Power Spectrum Density (PSD), the profiles were classified according to ISO 8608 standard. Two methodologies were followed to model and create a number of synthetic realisations for each profile: Direct Spectrum Estimate (DSE) and ISO based modelling. Simulating the produced synthetic profiles with the quarter-car vehicle model, the corresponding pseudo damage was calculated. The accumulated damages from the DSE models were closer to the corresponding ones from the measured profiles. ISO based models could not model the profile irregularities, which proved to contribute the largest part of the accumulated fatigue damage. [ABSTRACT FROM AUTHOR]

Abstract: This paper develops a yaw dynamic model for a farm tractor with a hitched implement, which can be used to understand the effect of tractor handling characteristics for design applications and for new automated steering control systems. Dynamic equations which use a tire-like model to capture the characteristics of the implement are found to adequately describe the tractor implement yaw dynamics. This model is termed the “3-wheeled” Bicycle Model since it uses an additional wheel (from the traditional bicycle model used to capture lateral dynamics of passenger vehicles) to account for the implement forces. The model only includes effects of lateral forces as it neglects differential longitudinal or draft forces between inner and outer sides of the vehicle. Experiments are taken to verify the hitch model using a three-dimensional force dynamometer. This data shows the implement forces are indeed proportional to lateral velocity and that differential draft forces can be neglected as derived in the “3-wheeled” Bicycle Model. Steady state and dynamic steering data are used for implements at varying depths and speeds to quantify the variation in the hitch loading. The dynamic data is used to form empirical transfer function estimates (ETFEs) of the implements and depths in order to determine the coefficients used in the “3-wheeled” Bicycle Model. Changes in a single parameter, called the hitch cornering stiffness, can capture the various implement configurations. Finally, a model that includes front wheel drive forces is derived. Experiments are taken which provide a preliminary look into the effect of four-wheel drive traction forces, and show a difference with two-wheel versus four-wheel drive, on the yaw dynamics of a tractor with the hitched implement. [Copyright &y& Elsevier]

Abstract: The study of tillage tool interaction centers on soil failure patterns and development of force prediction models for design optimization. The force-deformation relationships used in models developed to date have been considering soil as a rigid solid or elasto-plastic medium. Most of the models are based on quasi-static soil failure patterns. In recent years, efforts have been made to improve the conventional analytical and experimental models by numerical approaches. This paper aims at reviewing the existing methods of tillage tool modeling and exploring the use of computational fluid dynamics to deal with unresolved aspects of soil dynamics in tillage. The discussion also focuses on soil rheological behaviour for its visco-plastic nature and its mass deformation due to machine interaction which may be analyzed as a Bingham plastic material using a fluid flow approach. Preliminary results on visco-plastic soil deformation patterns and failure front advancement are very encouraging. For a tool operating speed of 5.5ms−1, the soil failure front was observed to be about 100-mm forward of the tool. [Copyright &y& Elsevier]

Abstract: During the past decades the author has continually worked on and perfected his conception of the interaction between the soil and the wheel. First, this work is summarized in this paper. The author then describes his conception of the mechanical interaction between them and clarifies the connection between the kinematic and dynamic processes that take place when a tractor is exerting pull. He shows by means of his kinematic model how the peripheral force is developed. Finally, he derives the appropriate equations for the computation of the peripheral force and the drawbar pull for both two-wheel-drive and four-wheel-drive tractors. Practical experience has proven that the concept is correct and the method is practical. [Copyright &y& Elsevier]

Full-scale tests were carried out within the broader framework of a study of an operational mechanical mine clearance system. This system is made up of a tracked machine pushing a mine clearance plow that scarifies the soil to approximately 30 cm depth. This study examines the capacity of the tractor to move on a disturbed soil. This paper presents motion resistance tests and drawbar pull tests on four types of soil. The soils have been chosen to be scientifically representative of the broad distribution on our planet: a sand (frictional soil), a silt (cohesive soil), a silty gravel (coarse-grained soil), and a silty sand (cohesive soil). The tests are performed in two configurations: on compacted soils and on soils scarified with an experimental plow. The results of each test condition are described. The effects of the soil type, its state, and the speed of the tested vehicle are presented. Using these results and, in addition, full-scale tests of scarification, we present an operational analysis determining the mobility of a tracked vehicle on broken soil. This method makes it possible to calculate the maximum speed of a mechanical mine clearance system for the whole range of soils tested. [Copyright &y& Elsevier]

Both experience and research warn that heavily loaded wheels of agricultural transport vehicles and heavy machinery may cause severe compaction damage to the farmland. A remedy consists of reducing both the wheel load and the contact pressure.Early in the 1990s, the author suggested an experimental examination of the problem of soil compaction under fully controlled conditions. The ensuing research program, which was sponsored by the Grant Agency of the Czech Republic, included a series of experiments with loaded wheels carried out in the experimental grounds of the Czech University of Agriculture and, subsequently, their physical modelling in the laboratory of the Department of Motor Vehicles, Technical faculty. This program has corroborated the idea that physical modelling under controlled conditions, complemented by an adequate evaluation procedure, has a promising potential to predict full-scale ground compaction and become a sound basis for practical measures. This paper describes the laboratory equipment, testing technique, and the way of evaluating the compaction potential of tires in terms of soil dry bulk density, leading to a Compaction Number (CN) rating of individual tires. Practically, the CN rating is supposed to be included in agricultural tire catalogues to complement the load capacity/inflation pressure values for hard ground (e.g., ETRTO specifications based on tire strength and wear). [Copyright &y& Elsevier]

Enhancement of the potential root growth volume is the main objective of farmers when they establish a conventional tillage system. Therefore, the main function of primary tillage is to increase soil’s structural macroporosity. In spite of this, during secondary tillage operations on these freshly tilled soils, the traffic on seedbeds causes significant increases in soil compaction. The aim of this paper was to quantify soil compaction induced by tractor traffic on a recently tilled non consolidated soil, to match ballast and tyre size on the tractors used during secondary tillage. The work was performed in the South of the Rolling Pampa region, Argentina. Secondary tillage traffic was simulated by one pass of a conventional 2WD tractor, using four configurations of bias-ply rear tyres: 18.4×34, 23.1×30, 18.4×38 and 18.4×38 duals, two ballast conditions were used in each configuration. Soil bulk density and cone index in a 0 to 600 mm profile were measured before and after traffic. Topsoil compaction increased as did ground pressure. Subsoil compaction increased as total axle load increased and was independent from ground pressure. At heavy conditions, topsoil levels always showed higher cone index values. From 150 to 450 mm depth, the same tendency was found, but with smaller increases in the cone index parameter, 22 to 48%, averaging 35%. Finally, at the deepest layer considered, 600 mm, differential increases due to the axle load are great enough as to be considered similar to those found in the upper horizon, 36 to 64%, averaging 55%. On the other hand, bulk density tended to be less responsive than cone index to the traffic treatments. Topsoil compaction can be reduced by matching conventional bias-ply tyres with an optimized axle weight. [Copyright &y& Elsevier]

This paper discusses the loading of a typical central Anatolian soil by the most commonly used corn and wheat production agricultural equipment. It further describes the effect that loading and soil conditions have on soil strength, namely compaction, and proposes techniques for minimizing undesired soil compaction. Experiments were carried out on a typical central Anatolian medium-textured imperfectly drained clay loam soil (Cambisol). Three different tillage methods and subsequently the same field operations were used for each rotation. Shear strength, penetration resistance, bulk density and moisture variations were detected in four sampling periods at each rotation. Tillage reduced the soil strength with the mouldboard plough causing the greatest loosening. However, natural processes and the vehicular traffic caused the soil to be re-compacted to about the same values as before. In any of the cases the obtained parameters did not exceed the critical values for plant growth except the penetration resistance in the 20–30 cm depth layer during corn production. [Copyright &y& Elsevier]