Search

The performance of agricultural tires varies with the characteristics of both the terrain and the tractors on which they are mounted, which differently affect the rolling resistance, the traction capacity, and the slip. To reduce the variability of test conditions, CREA developed an original mobile test (MTB) bench which consists of a dynamometric single axle trailer pulled by a tractor and can be used both in traction performance tests (driving wheels) and in rolling resistance tests (driven wheels). A control system alternatively operates the adjustment of traction force or slip, so that each test is performed maintaining constant the desired values. The MTB underwent tests under different conditions (type of surface, pre-set values of force of traction and slip) aimed at verifying its accuracy and reliability. In a final test, two pairs of identical new tires were simultaneously mounted on the MTB and on the rear axle of the 2WD tractor that pulled it, to discover information on the different interactions occurring, under the same traction conditions, between the soil surface and each pair of tires, with reference to the relationship between the slips and the load transfers observed on the MTB and on the tractor rear axle. The results evidenced the capability of the MTB to guarantee repeatable test conditions, including field conditions, allowing comparison among the performance of different tires. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agricultural Engineering / Jurnal Keteknikan Pertanian is the property of IPB University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Grouser height and soil moisture content have a significant effect on the tractive performance of tracked vehicles. Paddy soil has the mechanical properties of both clay soil and sandy soil and can have a wide range of water content values, and it has a considerable influence on the tractive performance of tracked agricultural machinery. To study the influence of grouser height on the tractive performance of a single-track shoe under different soil moisture contents, a three-dimensional shearing model of the single-track shoe and the contact soil was established based on the ground vehicle mechanics theory, and an experimental platform with a soil bin, sensors, and a control system was established. Six preset levels of moisture contents (7%, 12%, 17%, 22%, 27%, and 32%) of paddy soil were prepared for the research experiment. The mechanical properties of the soil with different moisture contents were obtained through the use of a direct shear test, penetration test, and compaction test. The obtained physical parameters of the soil have special characteristics that are different from typical soil. Combined with the three-dimensional model and the obtained soil parameters, the parameters of the tractive performance, such as thrust, running resistance, and traction with different moisture contents were analyzed and calculated. The test results revealed that the thrust at different grouser heights shows a regular waveform growth trend with an increase in soil moisture content. The minimum value and the maximum value of thrust were obtained at moisture contents of 7% and 12%, respectively. The curve of different grouser heights of the running resistance shows similar changes with different moisture contents. The two peak points and inflection points of the fluctuation curve are for moisture contents of 17% and 27%. The change curve of the traction is highly similar to the curve of thrust. The maximum value of the traction was found at a moisture content of 12%, and the minimum value at 22% or 27%. Under different moisture conditions, tracked vehicles with higher grousers have better tractive performances. [ABSTRACT FROM AUTHOR]

Tracked tractors are better suited for agricultural production in hilly environments because of their excellent stability and flotation. The ground pressure in these environments is highly irregular owing to the ground slope, which has led to a lack of theoretical foundation and data support for the development of hillside tracked tractors (HTTs). Therefore, accurate prediction of the ground pressure at the track-soil interface on inclined terrain is important. In this study, sloped ground pressure prediction model composed of sloped terrain soil pressure-sinkage model was developed to analyse the distribution characteristics of the ground pressure of tracked tractors in agricultural operations on hillside slopes. Considering the influence of the slope angle, soil conditions, operating conditions, and important parameters of the tracked tractors (including mass, centre of gravity, and track gauge), the ground pressure prediction model used harmonic oscillator functions and peak-valley control primitive functions. To validate the proposed model, ground pressure tests of the experimental tracked tractor were conducted at different slope angles and operating conditions in an experimental platform integrating a "soil-machine-crop" system. The results showed that the maximum error between the predicted results and the test data under various slopes and operating conditions was approximately 6.3%, with an average error of approximately 4.7%; the consistency between the test results and the simulated results indicate that the model established in this study is accurate and credible. Based on the ground pressure model, the developed tractive performance prediction model for HTTs had high prediction accuracy for the slip rate and traction force in the climbing traction test. The developed theoretical model and results provide practical guidance for the structural design of advanced HTTs and manoeuvrability optimization. [Display omitted] • we develop a prediction model for distribution of grounding pressure of tracked tractors in hilly mountains. • The slope angle, the soil condition, and working conditions were considered in the model. • The model was expressed by the harmonic oscillation function and the peak-valley control function. • The ground pressure of the tracked tractor is multi-peak non-uniform distribution law. • The model is appropriate for the theoretical examination of tracked tractors performance. [ABSTRACT FROM AUTHOR]

In order to improve the applicability and prediction accuracy of the existing simulation test methods of vehicle tractive performance on sandy soil, the off-road tire model using the discrete element method (DEM) under each operating condition is separately established in this paper. The contact parameters of DEM model are calibrated by rubber-sand friction test and soil bin test combined with corresponding simulation test. On this basis, the tire-sand simulation model is calculated under straight and inclining driving conditions, and the variation law of drawbar pull, torque, tractive efficiency and sinkage is obtained. This paper proves the feasibility of DEM simulation in studying vehicle tractive performance, and also provides a systematic parameter calibration method for improving the accuracy of DEM simulation, which is of great significance to enrich vehicle testing methods.

The performance of agricultural tires varies with the characteristics of both the terrain and the tractors on which they are mounted, which differently affect the rolling resistance, the traction capacity, and the slip. To reduce the variability of test conditions, CREA developed an original mobile test (MTB) bench which consists of a dynamometric single axle trailer pulled by a tractor and can be used both in traction performance tests (driving wheels) and in rolling resistance tests (driven wheels). A control system alternatively operates the adjustment of traction force or slip, so that each test is performed maintaining constant the desired values. The MTB underwent tests under different conditions (type of surface, pre-set values of force of traction and slip) aimed at verifying its accuracy and reliability. In a final test, two pairs of identical new tires were simultaneously mounted on the MTB and on the rear axle of the 2WD tractor that pulled it, to discover information on the different interactions occurring, under the same traction conditions, between the soil surface and each pair of tires, with reference to the relationship between the slips and the load transfers observed on the MTB and on the tractor rear axle. The results evidenced the capability of the MTB to guarantee repeatable test conditions, including field conditions, allowing comparison among the performance of different tires.

Abstract The paper attempts to analyze full load characteristics of over 500 combustion engines. Using statistical tools, the author determined the value of the coefficient of flexibility. Engine flexibility is the capability of the engine to adapt to varying loads. Importantly, in the investigations, the author took into account the parameters calculated in the course of the investigations on a chassis dynamometer, i.e., actual, not taken from technical specifications of brand new vehicles. Different stages of operating wear allow a better characterization of the population. Subsequent utilization of the results in tractive calculations is more reliable. The engines were divided into in six groups, depending on the type of fuel system: fuel injected gasoline and turbocharged gasoline, spark ignition LPG, naturally aspirated diesel and turbocharged diesel. However, engines running on alternative fuels are characterized with a greater flexibility than the fuel injected base engines. Conformity of flexibility of fuel injected and LPG IV generation engines have been observed, which confirms the appropriateness of engine adaptation to alternative fueling. Gasoline engine supercharging allowed a reduction of the maximum engine speed of the maximum torque, which extends the range of analyzable speeds for flexibility and consequently, the flexibility as such.

Grouser height and soil moisture content have a significant effect on the tractive performance of tracked vehicles. Paddy soil has the mechanical properties of both clay soil and sandy soil and can have a wide range of water content values, and it has a considerable influence on the tractive performance of tracked agricultural machinery. To study the influence of grouser height on the tractive performance of a single-track shoe under different soil moisture contents, a three-dimensional shearing model of the single-track shoe and the contact soil was established based on the ground vehicle mechanics theory, and an experimental platform with a soil bin, sensors, and a control system was established. Six preset levels of moisture contents (7%, 12%, 17%, 22%, 27%, and 32%) of paddy soil were prepared for the research experiment. The mechanical properties of the soil with different moisture contents were obtained through the use of a direct shear test, penetration test, and compaction test. The obtained physical parameters of the soil have special characteristics that are different from typical soil. Combined with the three-dimensional model and the obtained soil parameters, the parameters of the tractive performance, such as thrust, running resistance, and traction with different moisture contents were analyzed and calculated. The test results revealed that the thrust at different grouser heights shows a regular waveform growth trend with an increase in soil moisture content. The minimum value and the maximum value of thrust were obtained at moisture contents of 7% and 12%, respectively. The curve of different grouser heights of the running resistance shows similar changes with different moisture contents. The two peak points and inflection points of the fluctuation curve are for moisture contents of 17% and 27%. The change curve of the traction is highly similar to the curve of thrust. The maximum value of the traction was found at a moisture content of 12%, and the minimum value at 22% or 27%. Under different moisture conditions, tracked vehicles with higher grousers have better tractive performances.

• A SRTT tire was tested in traction mode and towing mode on loamy sand. • Test data on tire traction and soil response at slip ratios up to 30% was collected. • Effects of inflation pressure, normal load, and initial soil compaction were analyzed. • Multi-pass effects on tire traction and soil response were discussed. • A new multi-pass effect related to ripple formation and soil failure was discovered. Tire tractive performance, soil behavior under the traffic, and multi-pass effect are among the key topics in the research of vehicle off-road dynamics. As an extension of the study (He et al., 2019a), this paper documents the testing of a tire moving on soft soil in the traction mode or towing mode, with a single pass or multiple passes, and presents the testing results mainly from the aspects of tire tractive performance parameters, soil behavior parameters, and multi-pass effect on these parameters. The influence of tire inflation pressure, initial soil compaction, tire normal load, or the number of passes on the test data has been analyzed; for some of the tests, the analysis was completed statistically. A multi-pass effect phenomenon, different from any phenomenon recorded in the available existing literature, was discovered and related to the ripple formation and soil failure. The research results of this paper can be considered groundwork for tire off-road dynamics and the development of traction controllers for vehicles on soft soil. [ABSTRACT FROM AUTHOR]

Tractive performance is a key factor affecting the field mobility of unmanned vehicles. Presently, studies on the tractive performance of unmanned vehicles mainly focus on the tractive performance of a single wheel, but few studies have used the discrete element method to predict the tractive performance of vehicles. In this paper, a method based on dynamics and discrete elements is proposed to predict the traction performance of a vehicle. Based on the proposed method, the tractive performance of an unmanned vehicle in various field environments is obtained. Firstly, a numerical method for calculating the dynamic tractive performance of the vehicle on a flat road surface is proposed based on vehicle dynamics theory and terramechanics. According to the corresponding soil parameters, the tractive performance of the vehicle on three different sandy loams and three different clays is calculated. The mechanism of action between the wheels and the soil on sloped road is different from that on flat road, and the numerical calculation method is no longer suitable for predicting the tractive performance of vehicles on sloped roads. To predict the tractive performance of unmanned vehicles on various slope roads, the dynamic and discrete element method was used to simulate a sandy loam flat road, sandy loam pitch slope, sandy loam roll slope, light clay flat road, light clay pitch slope, and light clay roll slope. The vehicle dynamics model was established using dynamics software, and the tractive performance of the vehicle on six different roads was obtained through the coupling simulation of dynamics and discrete elements. [ABSTRACT FROM AUTHOR]

The interaction between off-road tires and granular terrain has a great influence on the tractive performance of off-road vehicles. However, the finite element method or the discrete element method cannot effectively study the interaction between off-road tires and granular terrain. The three-dimensional combined finite element and discrete element method is applied to handle this problem. In this study, a calibrated finite element method–discrete element method model is established, in which the finite element model of off-road tire is validated by stiffness tests, while the discrete element model of gravel particles is validated by triaxial compression tests. The calibrated finite element method–discrete element method model can describe the structural mechanics of the off-road tire and the macroscopic mechanical properties of the gravel road. Tractive performance simulations of the off-road tire on gravel road under different slip conditions are performed with the commercial software LS-DYNA. The simulation results are basically corresponded with the soil-bin test results in terms of granular terrain deformation and tractive performance parameters versus the slip rates. Finally, the effects of tread pattern, wheel load, and tire inflation pressure on tractive performance of off-road tire on granular terrain are investigated. It indicates that the calibrated finite element method–discrete element method can be an effective tool for studying the tire–granular terrain interaction and predicting the tractive performance of off-road tire on granular terrain. [ABSTRACT FROM AUTHOR]

In this work, an indoor soil-bin is designed to investigate the tire–terrain interaction mechanisms for the off-road tires rolling on the gravel terrain. The soil-bin test is carried out by the indoor soil-bin experimental device and the three-dimensional (3D) finite element (FE) and discrete element (DE) coupling method under the same particles conditions, respectively. First, with the indoor soil-bin measurement system, the repeatability of the soil-bin experiments is employed to validate the experimental device and the numerical models. Moreover, the tractive performance experiments of the off-road tires with two tread patterns, smooth and grooved interacting with gravel terrain, are performed at the slip of 10%, 20% and 30%, respectively, to obtain the tractive force and the rim sinkage. Second, the corresponding numerical models are also established, and simulated by the FE–DE coupling method, where the FEM and the DEM are used to describe the off-road tires and the gravel terrain, respectively. The tractive mechanisms of the off-road tires in interaction with the gravel terrain such as the tractive force and the rim sinkage are investigated numerically. Meanwhile, The dynamics and discontinuity of the gravel assembly are described by the presented approach. Besides, both the results of the simulations and experiments indicate that tread patterns and slip conditions have great influence on the tire tractive performance. Finally, the numerical simulations and the experimental results qualitatively show good agreements, which certifies the effectiveness of the FE–DE coupling method in the tractive performance analysis of tire–gravel terrain interactions. [ABSTRACT FROM AUTHOR]

Inspired by the superior fixed and traction characteristics of ostrich foot toenails, we devised, optimized and manufactured the single structure and group arrangement of a new-style bionic spike for sprint shoes to improve athletic performance. The tractive performance of the bionic spike was tested by finite element analysis and experimental verification. The optimized single structure of the bionic spike had a top slope angle of 13° and the radius of the medial groove of 7.3 mm. Compared with the conventional conic spike, the maximal and stable extrusion resistances of the single bionic spike decreased by about 25% and 40% respectively, while the maximal and stable horizontal thrusts increased by about 16% and 10%, respectively. In addition, the arrangement of the bionic spikes was also optimized. Compared with the conventional spike group, the maximal and stable extrusion resistances of the bionic spike group decreased by 11.0% and 6.2%, respectively, while the maximal and stable horizontal thrusts increased by 20.0% and 16.0%, respectively. The current results may provide useful mechanical information that can help develop a better design of athletic shoes with the potential for advanced performance. [ABSTRACT FROM AUTHOR]

This work aims to determine a complete set of input parameters of the DEM-FEM coupling model, which ensures us obtain more realistic simulation results of the tire-terrain interactions. Firstly, we investigate the macroscopic responses of the gravel sample, the stress-strain curves and deformations, which is finished by the triaxial tests at different confining pressures of 25 kPa, 50 kPa and 100 kPa. Then, the microscopic input parameters of the numerical simulations are obtained by iteratively adjusting the coupling model parameters, which are employed to meet the macroscopic responses of the triaxial tests. Finally, the traction behavior researches of an off-road tire on gravel terrain are carried out by the DEM-FEM coupling model with the calibrated microscopic input parameters mentioned above. The predicted traction performance parameters such as the vertical reaction force, tractive force and tire sinkage are qualitatively in agreements with the corresponding experimental results. The effectiveness of the calibration method using numerical triaxial tests is validated in traction behavior of tire-terrain interactions. Unlabelled Image • Triaxial tests are performed to measure bulk behavior of the gravel assembly. • Numerical triaxial tests with flexible boundary are simulated by the DEM-FEM. • A complete set of model parameters is determined by bulk calibration approach. • The validity of parameter set is verified by analysis of tire-terrain interaction. [ABSTRACT FROM AUTHOR]

• Tire, soil, and tire-soil tests were completed to a passenger car tire and loamy sand. • Test data on tire off-road traction at a wide range of slip ratio has been collected. • Combined effect of inflation pressure and slip on traction and rut depth was analyzed. • Effect of soil compaction on effective rolling radius and rut depth has been analyzed. • Parameterization data for soil model and terramechanics model was collected. Tire performance over soft soil is of interest for automotive and geotechnical engineers; the automotive engineers are mainly interested in tire tractive performance, and geotechnical engineers are concerned with the effects of the traffic brought by the tire to the soil. This two-part paper documents a series of tire and soil tests (Part I) and the application of their test data to the study of tire tractive performance over soft soil (characterized by drawbar pull) and to the model parameterization (Part II). Part I of this paper details the series of tests that are comprised of static tire deflection tests, static tire-soil tests, soil properties tests, and dynamic tire-soil tests, and describes the influence of tire inflation pressure or soil compaction level on the test data. The experimental approach presented herein produces parameterization and validation data that can be used in tire off-road traction dynamics modeling and terramechanics modeling. [ABSTRACT FROM AUTHOR]

• Magic Formula (MF) was extended for large inflation pressure changes. • MF parameterization by genetic algorithm was compared with that by geometric feature. • A bulk density estimation model was parameterized by the data from soil tests. • An adapted Bekker's model parameterization was done by the data from tire-soil tests. The parameterization of terramechanics model for the tire off-road traction dynamics modeling relies exclusively on the plate-sinkage test and shear test (not using a tire as the shear tool), according to the existing literature. However, the plate-soil interaction cannot be considered the same as the tire-soil interaction (Plackett, 1985). Part II of this paper investigates whether the tire-soil test can be used to parameterize terramechanics model. The parameterization of the modified Bekker's model, the Magic Formula tire model, and a bulk density estimation model, using the data from the series of tire and soil tests presented in Part I of this paper (He et al., 2019), is discussed in detail herein. The parameterization approach presented herein can be used to develop tire off-road dynamics models. [ABSTRACT FROM AUTHOR]

The research on the interaction between off-road tires and soft ground is of great significance to improve the travel performance of off-road vehicle on soft ground. The interaction between tire and soft ground can not be described by the finite element method or the discrete element method effectively. A FEM-DEM model in which the off-road tire is modeled by the finite elements and the gravel road is modeled by the discrete elements was established based on the indoor single wheel soil bin test. The proposed model can be used to accurately describe the complex mechanical properties of off-road tire and the granular features of gravel road. The tractive performance of off-road tire on gravel road at different slip rates is simulated by using the combined finite element-discrete element method in LS-DYNA. The tractive performance parameters of off-road tire, such as tire tractive force and rim sinkage, at different slip rates were obtained and investigated. The numerically simulated results are basically corresponded with the experimental results, which verifies the validity of the combined finite element and discrete element method in studying the interaction between tire and soft ground. [ABSTRACT FROM AUTHOR]

According to the design requirements and characters of mining truck,an optimum mathematical model of transmission is set up to maximize actual power under the precondition of reliability. The transmission of mining truck is optimized by using optimization toolbox of MATLAB. With the visual display of the optimum results,several performance indexes such as the driving force,stand-by power and actual power are compared with the original design and among the optimum model,thus can provide an alternative option. Compared with original design,a good optimization effect is obtained from the optimum model of transmission.

Many studies on tractive performance of tractor tires have been carried out to solve soil-wheel interaction problems in the last decades. The purpose of this study is to experimentally determine effects on tractive performance of radial and bias-ply drive tires at three different tire lug heights, axle loads and inflation pressures. The experiments were carried out in stubble field conditions. To obtain sufficient performance data, a new single wheel tester was designed and manufactured. Travel reduction, net traction ratio and tractive efficiency varied from 3.3% to 34.1%, 0.24 to 0.93 and from 0.27 to 0.78 respectively depending on drawbar pull. The effects of tire type, lug height, dynamic axle load and inflation pressure on tractive efficiency were found significant P

To evaluate the tractive performance of tracked trencher on seafloor surface, a new shear stress-displacement empirical model was proposed for saturated soft-plastic soil (SSP model). To validate the SSP model, a test platform, where track segment shear test can be performed in seafloor soil simulacrum (bentonite water mixture), was built. Series shear tests were carried out. Test results indicate that the SSP model can describe the mechanical behavior of track segment with good approximation in seafloor soil simulacrum. Through analyzing the main external forces applied to seafloor tracked trencher during the uniform linear trenching process, a drawbar pull prediction model was deduced with the SSP model. A tracked walking mechanism of the seafloor tracked trencher prototype was built, and verification tests were carried out. Test results indicate that this prediction model was feasible and effective; moreover, from another side, this conclusion also proved that the SSP model was effective.

Highlights • A proper assessment of the bottom and side thrusts of the track system is essential. • Previous prediction models for the soil thrust tend to underestimate the side thrust. • Punching shear failure takes place along the side of the track system. • A prediction model for the side thrust is developed based on the punching shear theory. Abstract The track system is generally applied for heavy off-road vehicles. While moving on the off-road, the track system horizontally transmits an engine torque to the soil-track interface, resulting in slip displacement and an associated soil thrust acting as a traction force. As soil thrust is developed on the bottom and the side of the track system (hereinafter referred to as "bottom thrust" and "side thrust", respectively), it is imperative to evaluate both the bottom thrust and the side thrust to assess the off-road tracked vehicle's performance. Unlike the bottom thrust, however, the mechanisms of the side thrust have not been fully understood. To address this, this study aimed to evaluate the side thrust for off-road tracked vehicles. A new mechanism for the side thrust was theoretically investigated based on the punching shear theory. A series of model track experiments were conducted on a model track system with silty sand. From the experiment results, the shapes of the failure surface were observed, and the side thrust was measured for verification purposes. Particular attention was given to the development of a side thrust prediction model for the heavy off-road tracked vehicles based on the proposed mechanism. [ABSTRACT FROM AUTHOR]

It is very important for exploring that the lunar rover enhances the tractive performance. Tractive performance could be measured by these parameters such as sinkage, drawbar pull, driving torque, motion resistance and slip when the lunar wheels move. The parameters could be gotten by soil bin test. The soils in the bin are mined in volcano. The variation of the parameters with the vertical load and velocity is analyzed in the paper, slip ratio is below 18%, the motion resistance increases with the velocity, but slip ratio is greater than 18%, the parameter decreases with the increasing velocity. Meanwhile, the rutting of the wheel of lunar rover is simulated by fem. [ABSTRACT FROM AUTHOR]

This paper proposes an experimental method of predicting the traction performance of a small tracked mobile robot. Firstly, a track-terrain interaction model based on terramechanics is built. Then, an experimental platform of the tracked robot is established, on which the measurement methods of the parameters that influencing the accuracy of the prediction model are introduced and the data post-processing are improved, including drawbar pull, slip ratio, sinkage, track deformation and so on. Based on the experimental data, several key terrain parameters are identified. With the tracked robot platform, the drawbar pull-slip ratio relationship is tested, and the effects on drawbar pull considering different kinds of terrain and the influence of the grousers are analyzed as well. The research results provide a reference for the experimental study on the traction performance of small tracked robots. [ABSTRACT FROM AUTHOR]

Conventional ground-wheeled vehicles usually have poor trafficability, low efficiency, a large amount of energy consumption and possible failure when driving on soft terrain. To solve this problem, this paper presents a new design of transformable wheels for use in an amphibious all-terrain vehicle. The wheel has two extreme working statuses: unfolded walking-wheel and folded rigid wheel. Furthermore, the kinematic characteristics of the transformable wheel were studied using a kinematic method. When the wheel is unfolded at walking-wheel status, the displacement, velocity and acceleration of the wheel with different slip rates were analyzed. The stress condition is studied by using a classic soil mechanics method when the transformable wheel is driven on soft terrain. The relationship among wheel traction, wheel parameters and soil deformation under the stress were obtained. The results show that both the wheel traction and trafficability can be improved by using the proposed transformable wheel. Finally, a finite element model is established based on the vehicle terramechanics, and the interaction result between the transformable wheel and elastic–plastic soil is simulated when the transformable wheel is driven at different unfold angles. The simulation results are consistent with the theoretical analysis, which verifies the applicability and effectiveness of the transformable wheel developed in this paper. [ABSTRACT FROM AUTHOR]

Many studies on tractive performance of tractor tires have been carried out to solve soil-wheel interaction problems in the last decades. The purpose of this study is to experimentally determine effects on tractive performance of radial and bias-ply drive tires at three different tire lug heights, axle loads and inflation pressures. The experiments were carried out in stubble field conditions. To obtain sufficient performance data, a new single wheel tester was designed and manufactured. Travel reduction, net traction ratio and tractive efficiency varied from 3.3% to 34.1%, 0.24 to 0.93 and from 0.27 to 0.78 respectively depending on drawbar pull. The effects of tire type, lug height, dynamic axle load and inflation pressure on tractive efficiency were found significant (P<0.01) by the performed variance analysis and LSD tests. Radial tires provide better tractive performance compared with bias-ply tires. The tractive efficiency increased especially with increasing dynamic axle load and decreased with increasing tire inflation pressure. Tire dynamic axle load was the major contributory factor on tractive performance as compared with other independent variables. For a given drawbar pull, it was observed that tractive efficiency of radial tire can be maximized by selecting appropriate levels of lug height, dynamic axle load and inflation pressure. [ABSTRACT FROM AUTHOR]

Shear stress–displacement model is very important to evaluate the tractive performance of tracked vehicles. A test platform, where track segment shear test and plate load test can be performed in bentonite–water mixture, was built. Through analyzing existing literatures, two shear stress–displacement empirical models were selected to conduct verification tests for seafloor suitability. Test results indicate that the existing models may not be suitable for seafloor soil. To solve this problem, a new empirical model for saturated soft-plastic soil (SSP model) was proposed, and series shearing tests were carried out. Test results indicate that SSP model can describe mechanical behavior of track segment with good approximation in bentonite–water mixture. Through analyzing main external forces applied to test scaled model of seafloor tracked trencher, drawbar pull evaluation functions was deduced with SSP model; and drawbar pull tests were conducted to validate these functions. Test results indicate that drawbar pull evaluation functions was feasible and effective; from another side, this conclusion also proved that SSP model was effective. [ABSTRACT FROM AUTHOR]

We have been developing a simulation program for use with soil–wheel interaction problems by coupling Finite Element Method (FEM) and Discrete Element Method (DEM) for which a wheel is modeled by FEM and soil is expressed by DEM. Previous two-dimensional FE–DEM was updated to analyze the tractive performance of a flexible elastic wheel by introducing a new algorithm learned from the PID-controller model. In an elastic wheel model, four structural parts were defined using FEM: the wheel rim, intermediate part, surface layer, and wheel lugs. The wheel rigidity was controlled by varying the Young’s Modulus of the intermediate part. The tractive performance of two elastic wheels with lugs for planetary rovers of the European Space Agency was analyzed. Numerical results were compared with experimentally obtained results collected at DLR Bremen, Germany. The FE–DEM result was confirmed to depict similar behaviors of tractive performance such as gross tractive effort, net traction, running resistance, and wheel sinkage, as in the results of experiments. Moreover, the tractive performance of elastic wheels on Mars was predicted using FE–DEM. Results clarified that no significant difference of net traction exists between the two wheels. [ABSTRACT FROM AUTHOR]

Steel and rubber are two kinds of materials which are often used for the tracks of off-road vehicles. The objective of this study was to compare tractive performances of steel and rubber grouser shoes under different soil moisture contents. In this study, the tractive performance of single grouser shoe was predicted by soil parameters and three-dimensional shearing model. The soil used in this study was clay soil, and ten different soil moisture contents ranged from 8.58% to 54.36% were applied for investigation of soil parameters. For each soil moisture content, the penetration test, direct shearing test, density and soil moisture content measurement have been performed to obtain the required soil parameters. The experimental results showed that thrust and running resistance of steel single grouser shoe had similar trends to those of rubber single grouser shoe. The thrust of rubber single grouser shoe was always greater than that of steel single grouser shoe with the increase of soil moisture content, and as well as the running resistance. However, the traction of rubber single grouser shoe had a different trend to that of steel single grouser shoe. The traction of steel single grouser shoe was always greater than that of rubber single grouser shoe at any given moisture content except at the stage of less than 15% moisture content. From the experimental results, it can be concluded that the steel single grouser shoe performed better than rubber single grouser shoe in traction for the soil used in this study. [ABSTRACT FROM AUTHOR]

In order to utilize energy in the most efficient way in off-road vehicles, soil–wheel interaction should be investigated carefully since considerable amount of energy is lost due to tractive performance. In this study, the effects of radial tire on tractive performance at three different tire lug heights, axle loads and inflation pressures were experimentally determined. To obtain sufficient performance data, a new single wheel tester was designed and manufactured. Prior to experiments, properties of stubble field were determined. The tractive efficiency was found to increase with increasing dynamic axle load while decreasing with increasing tire inflation pressure. Dynamic axle load of the tire was the major contributory factor in the traction performance as compared with other independent variables. Seven different Artificial Neural Network and two types of Support Vector Regression models have been designed to predict the tractive efficiency. To evaluate the success of system, various statistical measures such as Mean Absolute Error, Root Mean Squared Error and Coefficient Determination have been used. The results show that the Artificial Neural Network model trained using Levenberg–Marquardt algorithm has produced more accurate results. [ABSTRACT FROM AUTHOR]

The usage of active front axle suspension on tractors with mechanical front wheel drive started only one-two decades. The suspended front axle changes the shock parameters of the tractor and this also affects the traction parameters. During our research we wanted to find out how the major traction parameters (drawbar force, velocity, tractive performance, wheel slips) change due to the active front axle suspension. By using the results of field tests we verified that the active front axle suspension reduces the slip significantly, in other words it increases the value of the possible drawbar force at a given slip. It was also proved that on the chassis more moderate shock waves develop. Due to this, the range of the different traction parameters (statistical dispersion) will be more moderate. This results in more constant, less fluctuating drawbar force and the tractor will be able to deliver higher tractive performance. [ABSTRACT FROM AUTHOR]

Abstract: This paper reviews the cultivation practices and tractive performance using wheeled tractors, and how these interact with soil management, in lowland intensive rice production. The paper explores the issues of long term sustainable soil use, the energy inputs required, environmental impact and changes in approach to agronomy and links these to the tractor operations carried out as part of rice production. The paddy soil environment demonstrates very significant changes in soil properties with depth, in particular soil density, penetrometer resistance, soil structure and pore interconnectivity, water content and movement, and soil biology. This is related to the management of the soil hard pan in relation to machinery operations and machinery use. One of the issues appears to be that the hard pan can be deeper than required with consequently unnecessarily high energy inputs. The tractive performance of wheeled tractors on different surface conditions is considered with respect to tractive efficiency and maintenance of a soil hard pan that has the required characteristics for sustainable production. Alternatives to conventional tyres, cage wheels and tracks, are considered. The cultivation operations are evaluated in relation to soil management, crop requirements and energy use. Variation in hard pan characteristics may be disadvantageous and provides opportunities for precision operations. [Copyright &y& Elsevier]

Traction experimental setups have been used extensively for tractive performance and soil compaction experiments. Various traction test setups were designed and developed for performing researches on traction mechanic of tires used in agricultural tractors. Those test setups can control peripheral tire speed, travel reduction and dynamic axle load. By the development of these experimental setups, more sensitive and accurate data acquisition opportunity was provided by means of advanced measurement systems beside the gained ability of performing experiments in different grounds. These setups utilize computer systems which feeds back in order to control forward speed, inflation pressure, dynamic axle load, travel reduction and net traction. In this study, designed and implemented experimental setups dedicated to traction performance experiments of drive tires used for agricultural tractors are described and reported. [ABSTRACT FROM AUTHOR]

Abstract: An instrumented drive axle is introduced for a prototype tractor using in field research on tractor and implement performance. This mechanism was developed to determine whether such an instrumented drive axle is practical. The drive axle was equipped with a set of transducers to measure wheel angular velocity, rear axle torque and dynamic weight, as well as tire side forces. Measuring the drawbar pull acting on the tractor provides data for calculating net traction, motion resistance and chassis resistance for each driven wheel. [Copyright &y& Elsevier]

Abstract: The paper presents an analysis and quantitative evaluation of the effect of soil conditions on tractive performance of off-road wheeled and tracked vehicles. The results of this study indicated that to accurately calculate the tractive performance of a vehicle in a given soil condition, soil properties and parameters and their changes as functions of soil moisture content and density should be taken into account. An effective Tractive Performance Analytical (TPA) model which takes into consideration the effect of soil conditions on tractive performance of the vehicles is developed. The TPA model uses invariant soil parameters that can be given or measured before the calculations by routine methods of classical soil mechanics. Soil parameters can also be obtained by recommended empirical equations using four physical soil parameters measured in the field with hand held instruments without time consuming and costly plate or vehicle tests. The model was validated in different soil conditions and compared with other models used in terramechanics for tractive performance predictions. The paper includes also an analysis of capabilities and limitations of the observed models. [ABSTRACT FROM AUTHOR]

This paper describes the results of a study of the correlation between the performances of wheels for lunar vehicles predicted using the Nepean wheeled vehicle performance model (NWVPM), developed under the auspices of Vehicle Systems Development Corporation, Ottawa, Canada, and the corresponding test data presented in 'Performance evaluation of wheels for lunar vehicles', Technical Report M-70-2, prepared for George C. Marshall Space Flight Center, National Aeronautics and Space Administration (NASA), USA, by the US Army Engineer Waterways Experiment Station (WES). The NWVPM was originally developed for design and performance evaluation of terrestrial off-road wheeled vehicles. The purpose of this study is to assess the potential of the NWVPM for evaluating wheel candidates for the new generation of extra-terrestrial vehicles. Two versions of a wire-mesh wheel and a hoop-spring wheel, which were considered as candidates for lunar roving vehicles for the NASA Apollo program in the late 1960s, together with a pneumatic wheel were examined in this study. The tractive performances of these wheels and of a 4×4 test vehicle with the pneumatic wheels on air-dry sand were predicted using the NWVPM and compared with the corresponding test data obtained under Earth's gravity and previously documented in the above-named report. While test data on wheel or vehicle performances obtained under Earth's gravity may not necessarily be representative of those on extra-terrestrial bodies, because of the differences in gravity and in environmental conditions, such as atmospheric pressure, it is still a valid approach to use test data obtained under Earth's gravity to evaluate the predictive capability of the NWVPM and its potential applications to predicting wheel or wheeled rover performances on extra-terrestrial bodies. Results of this study show that, using the ratio (P20/W) of the drawbar pull to normal load at 20 per cent slip as a performance indicator, there is a reasonable correlation between the predictions and experimental data. This indicates that the NWVPM has the potential as an engineering tool for evaluating wheel candidates for a future generation of extra-terrestrial vehicles, provided that appropriate input data are available. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we describe a mathematical model designed to allow for the determination of the mechanical relationship existing between soil characteristics and the primary design factors of a tracked vehicle, and to predict the tractive performance of this tracked vehicle on soft terrain. On the basis of the mathematical model, a computer simulation program (Tractive Performance Prediction Model for Tracked Vehicles; TPPMTV) was developed in this study. This model took into account the characteristics of the terrain, including the pressure-sinkage, the shearing characteristics, and the response to the repetitive loading, as well as the primary design parameters of the tracked vehicle. The efficacy of the developed model was then confirmed via comparison of the drawbar pulls of tracked vehicles predicted using the simulation program TPPMTV, with those determined as the result of traction tests. The results indicated that the predicted drawbar pulls, with the change in slip, were quite consistent with the ones measured in the traction test, for the changes in the weight of the vehicle, the initial track tension, and the number of roadwheels within the entire slip range. Thus, we concluded that the simulation program developed in this study, named TPPMTV, proved useful in the prediction of the tractive performance of a tracked vehicle, and that this system might be applicable to the design of a vehicle, possibly enabling a significant improvement in its functions. [Copyright &y& Elsevier]

The traction mechanics of a vehicle was developed based on the track-terrain interaction mechanism. The vehicle was tested on three different terrains: terrain I, terrain II, and terrain III. The tractive effort of the vehicle increased 14 per cent when the moisture content of the terrain increased from 59.85 per cent to 81.06 per cent. A traction coefficient of 48 per cent of the vehicle's gross weight justified the vehicle's optimum design for the Sepang peat terrain. Less variability of the vehicle's tractive effort for straight motion in the range of 7.5 per cent to 13.2 per cent and for turning motion in the range of 9 per cent to 11.5 per cent between the predicted and measured tractive effort on the peat terrain III for different loading and operating speeds substantiate the validity of the developed mathematical model. [ABSTRACT FROM AUTHOR]

This paper describes the results of a detailed investigation into the effects of initial track tension (i.e. the tension in the track system when the vehicle is stationary on a level, hard surface) on soft ground mobility of tracked vehicles. The investigation was carried out using the latest version of an advanced computer simulation model, known as NTVPM, developed under the auspices of Vehicle Systems Development Corporation. The results show that the initial track tension has significant effects on the peak normal pressure and mean maximum pressure on the track-terrain interface, sinkage of the track, and the drawbar pull and tractive efficiency of a vehicle on unprepared terrain. The impact of initial track tension on tractive performance is however dependent upon vehicle design features, including suspension characteristics. This investigation demonstrates that the simulation model NTVPM can play a significant role in the detailed evaluation of the design of tracked vehicles from a traction perspective. [ABSTRACT FROM AUTHOR]

A Trelleborg Twin 421 Mark II 600/55-26.5 steel-reinforced bias-ply forwarder drive tire at inflation pressures of 100 and 240 kPa and dynamic loads of 23.9 and 40 kN was used at 5% travel reduction on a firm clay soil. Effects of dynamic load and inflation pressure on soil–tire contact pressures were determined using six pressure transducers mounted on the tire tread. Three were mounted on the face of a lug and three at corresponding locations on the undertread. Contact angles increased with decreases in inflation pressure and increases in dynamic load. Contact pressures on a lug at the edge of the tire increased as dynamic load increased. Mean and peak pressures on the undertread generally were less than those on a lug. The peak pressures on a lug occurred forward of the axle in nearly all combinations of dynamic load, inflation pressure, and pressure sensor location, and peak pressures on the undertread occurred to the rear of the axle in most of the combinations. Ratios of the peak contact pressure to the inflation pressure ranged from 0 at the edge of the undertread for three combinations of dynamic load and inflation pressure to 8.39 for the pressure sensor on a lug, near the tire centerline, when the tire was underinflated. At constant dynamic load, net traction and tractive efficiency decreased as inflation pressure increased. [Copyright &y& Elsevier]

This study was aimed at investigating traction performance of a cage wheel for use in swampy peat soils in Indonesia. The tests were conducted in a soil bin filled with peat soil taken from the swampy areas. A set up was developed to measure tractive performance of a single cage wheel. Deep sinkage and high wheel slip were identified as the major problems of using the existing cage wheel design in swampy peat soils. The results revealed that increasing the lug angle from 15 to 35° and the length of lug improved the tractive performance of the cage wheel significantly, while increasing the number of lugs from 14 to 18 and width of lug did not improve the tractive performance significantly. A cage wheel with lug size 325×80 mm, 35° lug angle, 14 lugs (26° lug spacing), with 2 circumferential flat rings installed on the inner side of the lugs, out performed the other settings for use with power tillers in swampy peat soils. [Copyright &y& Elsevier]