Traction Performance Research Articles

Analysis of rigid tire traction performance on a sandy soil by 3D finite element–discrete element method

A 3D simulation method was developed to investigate the tire–sand interactions, where the discrete element (DE) and finite element (FE) methods were coupled. An algorithm for the contact of FE and DE was introduced. The Hertz–Mindlin theory was applied to calculate the contact force among elements. A 3D numerical model was established based on the soil-bin experiment to validate the feasibility of the method in the analysis of the tire–sand interactions. The traveling process of the smooth tire on the sandy soil was simulated and the traction performance parameters of the tire under different slip values (0%, 10%, 20%, 30%, 40%, 50% and 60%) were obtained. The overall trend of the drawbar pull versus the slip ratio is qualitatively in agreement with current experimental results. The result also proved the feasibility of the 3D FE–DEM in the simulation of the tire–sand interactions.

Experimental Study on Shear Strength of Alfalfa Grassland at High Soil Bulk Density

Grasslands are the important supplementary source of food. Shear strength at high soil bulk density grassland was studied to improve the traction performance and develop the crop yield. Shear force and shear displacement are tested at different vertical loads. Results indicated that with the increasing of shear displacement, shear force was found to show a parabolic trend of first increasing then decreasing. Moreover, larger vertical load would lead to steeper shear force curve against shear displacement. It also should be noted that, the maximum shear stress showed a parabolic increase trend following the increasing of the normal stress. This is the theoretical basis of matching appropriately tractor and implement system to maximize the traction performance and reduce tire slip.

English

Improving the traction performance of the electric railway vehicles requires an analysis to reduce their aerodynamic resistance. These vehicles cannot be set in motion without an external power source, which demonstrates that the supply system is a key-element to their operation. The power source is located on the rooftop which basically results in an increase of their aerodynamic resistance. The present study discusses the aerodynamic resistance of the electric railway equipment such as pantographs, automatic circuit breaker, insulators, etc. The analyze is based on the equipment installed on the electric locomotive LE 060 EA of 5100 kW which is operational in Romania, emphasizing the pantographs role in capturing of electricity.

Co-Simulation Study of Synchronous Control Technology for Independent Electric Drive Vehicle

The slip-judgment method of threshold value was made for all-wheel independent electric drive vehicle through the analysis of the relationship of steering kinematics, which based on detecting speed and current of wheel-motor. The speed coordinated control of motor was used as synchronous control method. Models of vehicle dynamics and synchronous control were respectively constructed in Adams and Matlab/Simulink, which composed the model of mechanical-electric collaborative simulation. The synchronous control process of vehicle that running on bisectional road was analyzed, the result shows that synchronous control based on power control strategy reduces slip-wheel motors power consumption and increases other motors output power and torque through reducing the motor speed to average speed of normal wheel-motor. Improves the traction performance and stability of vehicle, also reduces the wheel wear and drivers control difficulty. The method has advantages of low cost, wide applicability, good controllability, high reliability etc., provide the reference of synchronization technology for independent electric drive military vehicle.

Research Trends for Performance, Safety, and Comfort Evaluation of Agricultural Tractors: A Review

Department of Biosystems Machinery Engineering, Chungnam National University, Daejeon, Korea Machinery Technology Group, Advanced RD Revised: January 28th, 2014; Accepted: January 28th, 2014 Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO’s) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

Soil mapping to assess workability in central Italy as climate change adaptation technique

<div> <p><span style="font-family:arial,helvetica,sans-serif;">In this paper soil conventional tillage (CT) in two adiacent on-farm sites, hilly and plain fields, was carried out in comparison with direct-seeding + fertilizing at very low water content. The quality and quantity of work were evaluated through machine performance, fossil-fuel energy requirements and carbon dioxide emissions from agricultural machinery. The fields were previously sampled and mapped to investigate spatial variability of soil properties, to find soil quality indicators and to asses soil workability. The results revealed good traction performance during CT operations (slip values were lower than 15%). During plowing, time efficiency of the wheeled tractor was 40% lower with respect to the tracked tractor. Global energy employed was of the same magnitude for the tracked and wheeled tractor (220 kWh ha<sup>-1</sup>) while was significantly lower (52 kWh ha<sup>-1</sup>) for direct-seeding+fertilizing. The degree of crushing of the soil caused by CT required further energy employed (98 kWh ha<sup>-1</sup>) to seedbed preparation. Fossil-fuel energy requirements from agricultural machinery were significantly lower during direct-seeding+fertilizing (0.52 GJ ha<sup>-1</sup>) with respect to the conventional soil tillage (2.30 GJ ha<sup>-1</sup>). Wheat yield of direct seeded field and the total cost of the crop cycle (€/ha) were 9% and 16% lower respectively than the values recorded on fields under conventional tillage.</span></p> </div> <p> </p>

Using a modified version of the Magic Formula to describe the traction/slip relationships of tyres in soft cohesive soils

The tractive force/slip relationships of pneumatic tyres are required as inputs to vehicle performance prediction models such as the NATO Reference Mobility Model. They can also be used to calculate the tractive efficiency and work output of vehicles such as farm tractors, especially important when the vehicles are performing high drawbar pull operations; the effects of altering tyre size, tyre pressure and ballast can be predicted. The so-called Magic Formula is widely used for describing the force/slip relationships of pneumatic tyres on hard road surfaces. The coefficients in the Magic Formula are derived from experimental measurements. Relationships are then developed to describe the coefficients as functions of normal load on the tyre. The paper describes how the Magic Formula can be adapted to describe the tractive force/slip relationships of tyres in soft cohesive soils. The coefficients are made functions of Mobility Number instead of normal load. Mobility Number is an empirical system for estimating the tractive performance of tyres in soft soils at a single value of slip. The method could be extended to cover lateral tyre forces or other soil types if suitable experimental data is available.

Preliminary study on compressed air powertrain of a rescue vehicle for mine accidents

This paper investigates the feasibility of applying a compressed air powertrain to mine rescue vehicles, which require strict explosion-proof and flame-proof characteristics. Based on both simulation and preliminary tests of a single-cylinder air-powered engine prototype, the concept of compressed air powertrain for a rescue vehicle is proposed. Compared to conventional internal combustion engines, the exhaust emissions of the proposed air-powered engine concept are innoxious and its gas temperature is very low, which guarantees the safety and explosion-proof requirements. Preliminary selection and matching of both a transmission and final gear reduction are carried out, considering vehicle traction and air consumption performance characteristics. Simulation results show that given properly designed drivetrain gear ratios, the air-powered rescue vehicle can reach a speed of 7 km/h with gear 1 on a 30% slope road. Compared to current products, its feasibility in driving mileage and traction performance are further confirmed.

Durability test on an agricultural tractor engine fuelled with pure biodiesel (B100)

The performance of a 118-kW tractor fuelled by pure biodiesel was monitored during a long-term field experiment with approximately 800 h of engine function. The objective was to demonstrate that B100, a pure biodiesel fuel, is a viable alternative to traditional diesel oil in terms of long-term mechanical reliability. A bench test on the new engine, performed by attaching a test stand to the power take-off of the tractor, showed an expected reduction in power (-9%) and torque (-7%) and an increase in specific consumption (+13%) when biodiesel was used as a complete substitute to diesel oil. Furthermore, with the same setup, the exhaust gas had a Bosch smoke index equal to 50% of the value for the same engine fuelled with diesel oil. After these initial tests, the tractor was set up for normal field operations, in which both the engine curves and lubricant quality were periodically monitored. These surveys indicated no significant reduction in engine performance; however, the lubricant was consequently diluted and contaminated by biodiesel, which caused the lubricant properties to considerably worsen. However, on the basis of the chemical-physical analysis, reducing the oil change interval from 200 h (manufacturer's indications for the engine when operating with diesel oil) to 100 h would compensate for this progressive quality decline. At the end of the trials, the engine was disassembled to check the condition of its components; wear and lacquer-like coating phenomena were observed, and their levels were acceptable. The obtained results demonstrated that B100 can effectively substitute for diesel oil in a standard compression-ignition engine: the power change is not perceptible during normal operation of a tractor, and no particular problem will arise in the engine during its life if the lubricant is changed every 100 h.

Simulation and experimental validation of a modified terramechanics model for small-wheeled vehicles

The ability to model and predict vehicle performance over deformable terrains, which is typically done using terramechanics, is important for planetary exploration, military operations, and off-road vehicle design. This paper details the development of a new vehicle-terrain model that specifically addresses some of the limitations of traditional terramechanics when applied to Unmanned Ground Vehicles (UGVs) with small wheel diameters. Assumptions and limitations of the classical Bekker terramechanics model for wheeled locomotion are discussed. A novel pressure-sinkage model that was recently developed by the authors is detailed and shown to improve sinkage and compaction resistance models significantly. These models are implemented in a numerical simulation, which is used to predict the tractive performance of an experimental UGV. Field tests carried out on sandy terrain are described, and the results are used to validate the simulated predictions.

Experimental investigation of vehicle mobility using a novel wheel mobility number

The wheel mobility number is a dimensionless variable used to predict the combined effect of tire and soil parameters on tractive performance. As the mobility number increases, the tractive performance improves. The wheel mobility number depends on soil strength, tire load, and tire geometry (width, diameter, section height, and deflection). The main purpose of this paper is to investigate the effect of tire and soil parameters on vehicle mobility. For this purpose, the soil strength is obtained experimentally using an electronic cone penetrometer. The tire geometry is obtained by experimental testing at different loads, from 2 to 6kN. This includes the effect of the variation of tire inflation pressure from 100 to 250kPa on tire section height and tire width. The tire inflation pressure, tire width, and wheel diameter are used as independent variables to investigate the relative wheel numeric. The effect of the soil strength, tire load, and tire geometry, as dependent variables, on the wheel mobility number, is also investigated. The results show that the mobility number increases when soil strength and tire diameter increase, and tire width, tire load, and tire pressure decrease. Based on theoretical analysis and experimental testing, a proposed wheel mobility number is introduced. It depends on the wheel numeric and the square root of the difference between the tire section height and the tire deflection, divided by the tire diameter. Using the proposed wheel mobility number, the vehicle mobility is predicted and a very good correlation with experimental data is obtained.

A Mechanistic Approach to Topsoil Damage due to Slip of Tractor Tyres

Tractor traction tyres interact with soil by a system of normal and tangential stresses along the soil-tyre contact surface. In this interaction both soil and tyre deform according to their own stress-strain relationships. Soil deformation results in the formation of a rut as well as in topsoil displacement along the soil-tyre contact surface. The topsoil displacement depends on shear stress which soil undergoes at contact with tyre. The shear stress-displacement relationship characterizing the soil layer which interacts with the traction tyre has been studied for a long time as it strongly affects the relationship between traction force and wheel slip, usually referred to as traction performance of the soil-wheel system (Becker, 1956; Janosi and Hanamoto, 1961; Wills, 1963; Wong and Preston-Thomas, 1983)

Traction performance simulation for mechanical front wheel drive tractors: towards a practical computer tool

An analytical model to simulate the traction performance of mechanical front wheel drive MFWD tractors was developed at the Agroscope Reckenholz-Tänikon ART. The model was validated via several field tests in which the relationship between drawbar pull and slip was measured for four MFWD tractors of power ranging between 40 and 123 kW on four arable soils of different texture (clay, clay loam, silty loam, and loamy sand). The pulling tests were carried out in steady-state controlling the pulling force along numerous corridors. Different configurations of tractors were considered by changing the wheel load and the tyre pressure. Simulations of traction performance matched experimental results with good agreement (mean error of 8% with maximum and minimum values of 17% and 1% respectively). The model was used as framework for developing a new module for the excel application TASCV3.0.xlsm, a practical computer tool which compares different tractor configurations, soil textures and conditions, in order to determine variants which make for better traction performance, this resulting in saving fuel and time, i.e. reducing the costs of tillage management.

Traction performance simulation for mechanical front wheel drive tractors: towards a practical computer tool

An analytical model to simulate the traction performance of mechanical front wheel drive MFWD tractors was developed at the Agroscope Reckenholz-Tänikon ART. The model was validated via several field tests in which the relationship between drawbar pull and slip was measured for four MFWD tractors of power ranging between 40 and 123 kW on four arable soils of different texture (clay, clay loam, silty loam, and loamy sand). The pulling tests were carried out in steady-state controlling the pulling force along numerous corridors. Different configurations of tractors were considered by changing the wheel load and the tyre pressure. Simulations of traction performance matched experimental results with good agreement (mean error of 8% with maximum and minimum values of 17% and 1% respectively). The model was used as framework for developing a new module for the excel application TASCV3.0.xlsm, a practical computer tool which compares different tractor configurations, soil textures and conditions, in order to determine variants which make for better traction performance, this resulting in saving fuel and time, i.e. reducing the costs of tillage management.

Testing of Agricultural Tractor Engine using Animal-fats Biodiesel as Fuel

Purpose: Performances of a tractor diesel engine fueled by three different animal fats biodiesels were evaluated comparing with light oil tractor in terms of power, fuel consumption rate, exhaust gases, particulate matter amount and field work capacity. Methods: Animal fats based on pig biodiesel were manufactured manually and tested for its engine performance in the tractor diesel engine and fuel adoptability in the field works. Four different fuels, three different content of biodiesel (BD20, BD50, BD100) and light oil, were prepared and tested in the four strokes diesel engine. Power output, fuel consumption rate and exhaust gases of the four fuels in the diesel engine were compared and discussed. Results: Power output of light oil engine was the greatest showing 5.3% difference between light oil and BD100, but 0.37% better power than BD20 engine power. Less exhaust gases of <TEX>$CO_2$</TEX>, CO, <TEX>$NO_X$</TEX> and THC were produced from animal fats biodiesel than light oil, which confirmed that biodiesel is environmental friendly fuel. For fuel adoptability in the tractor, biodiesel engine tractor showed its fuel competitiveness comparing with light oil for tractor works in the faddy field. Conclusions: With four different fuel types of animal-fats biodiesel, performances of a four cylinder diesel engine for tractor were evaluated in terms of power, exhaust gases, particulate matters (PM) and field work capacity. No significant differences observed in the engine performances including power output and exhaust gases emission rate. No significant power difference observed between the various fuels including light oil on the engine running, however, amounts of noxious exhaust gases including <TEX>$CO_2$</TEX> and <TEX>$NO_X$</TEX> decreased as biodiesel content increased in the fuels. Field performances of animal-fats biodiesel tractor were investigated by conducting plowing and rotary operation in the field. Tilling and rotary performance of light oil tractor and BD20 tractor in the field were compared, in which about 10% travelling speed difference on both operations were monitored that showed light oil tractor was superior to BD20 tractor by 10%. Animal-fats can be an alternative fuel source replacing light oil for agricultural machinery and an environmental friendly fuel to nature.

Tests on Effect of Gravity and Soil Density on Soil Cone Index

The cone index is one of the important indicators that can describe the comprehensive physical characteristics of lunar regolith. Its closely related to the sink and sideslip of lunar rover and also has widely used in prediction the trafficability, adhesion property, tractive performance of lunar rover. Based on component method, a kind of low gravity simulator, the tiltable test-bed has been built. This study has got the stable low gravity along axial direction and measured the penetration resistance characteristics of JLU-2 in different gravity through tests. The results shows that the gravity environment has an obvious impact on the cone index of lunar soil simulant, CI values reduce with the decreasing of gravity environment. Namely, in the low gravity condition, it shows weaker resistance ability for a foreign object to penetrate into. The result has important application value of prepare, optimize and risk assessment in walking mechanism of lunar rover and the sampling mechanism.

Modeling and Simulation for a Tractor Equipped with Hydro-Mechanical Transmission

Purpose: A simulator for the design and performance evaluation of a tractor with a hydro-mechanical transmission (HMT) was developed. Methods: The HMT consists of a hydro-static unit (HSU), a swash plate control system, and a planetary gear. It was modeled considering the input/output relationship of the torque and speed, and efficiency of HSU. Furthermore, a dynamic model of a tractor was developed considering the traction force, running resistance, and PTO (power take off) output power, and a tractor performance simulator was developed in the co-simulation environment of AMESim and MATLAB/Simulink. Results: The behaviors of the design parameters of the HMT tractor in the working and driving modes were investigated as follows; For the stepwise change of the drawbar load in the working mode, the tractor and engine speeds were maintained at the desired values by the engine torque and HSU stroke control. In the driving mode, the tractor followed the desired speed through the control of the engine torque and HSU stroke. In this case, the engine operated near the OOL (optimal operating line) for the minimum fuel consumption within the shift range of HMT. Conclusions: A simulator for the HMT tractor was developed. The simulations were conducted under two operation conditions. It was found that the tractor speed and the engine speed are maintained at the desired values through the control of the engine torque and the HSU stroke.

The Sliding Mode Control for Traction Control System Based on Variable Optimal Slip Ratio

In this paper, the concept of intelligent tire and road surface information measurement methods are introduced, and the sliding mode algorithm for traction control system based on intelligent tire is proposed. By applying braking torque onto the driving wheels, the slip rates are adjusted to maintain within the optimal region on different road surface, and the optimal longitudinal traction is achieved. According to the simulation results on the CARSIM and MATLAB co-simulation platform of several working conditions, the TCS based on sliding mode control method improves the traction performance on different road surface effectively.

DESEMPENHO OPERACIONAL DE UM TRATOR AGRÍCOLA EM FUNÇÃO DA LASTRAGEM, PRESSÃO DE INFLAÇÃO E DESGASTE DO PNEU

Objetivou-se com o presente trabalho avaliar o desempenho operacional de um trator agrícola operando com pneus novos e desgastados em três condições de lastragem e três pressões de inflação dos pneus. O experimento foi realizado na unidade experimental pertencente ao Departamento de Zootecnia da Universidade Federal de Lavras, apresentando teor de água do solo de 25,6% e 14,97 T ha-1 de matéria seca no momento da realização dos testes. Utilizou-se um trator 4x2 TDA, com potência de 65,62 kW (88 HP) no motor. Os pneus foram do tipo R1, com as seguintes características: diagonal (dianteiros: 12.4-24; traseiros: 18.4-30), sendo que, a altura média das garras dos pneus novos foi de 30 e 35 mm para os pneus dianteiros e traseiros respectivamente, enquanto os pneus desgastados as garras mediram 18 mm e 4,5 mm, respectivamente. O delineamento experimental foi de blocos casualizados, em esquema fatorial 2x3x3, com 18 tratamentos e 3 repetições. Os resultados evidenciaram vantagens para o trator quando equipado com pneus novos. A patinagem foi maior quando usado pneus novos devido ao aumento da força e potência na barra de tração.

Plowing Performance Simulation and Analysis for Hybrid Electric Tractor

According to plowing operation characteristics, a case study on a parallel HET (hybrid electric tractor) with the torque combinator is conducted to develop a plowing operation performance simulation system. The mathematical models of drive equilibrium, battery, power combinator and control system are established respectively. A simulation system for evaluating the tractive performance, fuel economy, battery characteristics and controller performance of HET is developed in the environment of MATLAB/Simulink. Simulation results suggest that: in this HET, the output torque and traction vary in a large range with the variations in the operation modes and SOC level of the battery; in the common interval of SOC (0.4~0.7), compared with the traditional tractor, HET can achieve larger output torque with a fuel consumption reduction of 18% ~20% in discharge mode; with the capability of keeping the battery charge-discharge stage stable and guaranteeing the SOC variation in a small range, the controller meets with the requirements of plowing operation and benefits the stability of the tractor power and the extension of battery life cycle.