Laboratory-experimental verification of calculation of force effects in tractor's three-point hitch acting on driving wheels

doi:10.1016/j.still.2012.10.007

Soil and Tillage Research

Volume 128, April 2013, Pages 81-90

https://doi.org/10.1016/j.still.2012.10.007 Get rights and content

Abstract

The paper deals with the determination of the tractor wheel load during tillage. Forces acting between tractor and implement significantly change the load of driving wheels. Mathematical description of simple model fails due to impossibility of determination these forces between the tractor and implement. The article describes the multi-body model used for calculation of resultant force and torque acting from the implement on a tractor as well as the forces acting between the wheels and the soil. Paper also shows the results of verification of calculations based on experimental measurements carried out in the laboratory and tests performed under the field conditions.

Highlights

► Model for calculation of force effects acting on a ploughing tractor is created. ► Forces are calculated on the base of forces measured in a three point hitch. ► Model also calculates forces acting in the contact of wheels with the terrain. ► Multi-body model is 3D and covers TPH kinematics (vertical and side movement). ► Laboratory and field verification experiment was realized.

Introduction

The study on determination of wheel loads of agricultural tractor during ploughing was motivated by the fact that loading of driving wheels of the tractor with attached by implements varies significantly (Bauer and Sedlák, 2003). Different loading of the driving wheels influences maximum traction force and thus also tractor's traction properties, it influences tyre slip and so fuel consumption, and last but not least it influences soil compaction and so also an environment.

The problem to determine the wheel load tractor during ploughing lies in the difficulty to quantify the forces acting between soil and tillage tool (Kolator and Białobrzewski, 2011, Karkee et al., 2010). To overcome this problem, these forces are not determined on the basis of mathematical models of soil–tool interaction but of forces exerted from the tool on the tractor are measured. Effects on the tractor are then calculated on the base of simple or more detailed models of the tractor and the three-point hitch (TPH).

Measuring systems used by different researchers in this area can be divided into three groups, according to positioning of the measuring sensors.

In the case of first type of the measuring system, the sensors are positioned directly on the ploughing unit (Chaplin et al., 1987). This system provides exact information on deformation of working implement and it is thus used especially for its design optimization. This system of measuring is rather expensive, since each plough must be equipped by sensors.

When using the second type of measuring system, the special frame attached by force sensors is utilized. The frame is positioned between the tractor and implement. This system is usable for different types of tractors and implements and thus it is popular among researchers (Chaplin et al., 1987, Godwin et al., 1993, Al-Jalil et al., 2001, Kasisira and Du Plessis, 2006). On the other hand, it has several weak points. The main disadvantage is a heavy frame, which increases the total weight of the implement. Another problem is represented by shifting the implement to the back. Due to these facts, the whole system does not exactly correspond to the real conditions during ploughing.

The third type of measuring is performed by installation of the force sensors directly on three-point hitch. Although this type of experiment is the most similar to the real conditions, it is used quite rarely for research purposes. Efficiency and reliability of this system is highly dependent on positioning of the sensors. Some researchers (Al-Janobi, 2000) positioned the sensors on upper link and lower links. The lateral forces cannot be determined by this system.

Mclaughlin et al. (1993) describes the experiment, when the three-point hitch is attached by five force sensors. The forces measured in individual links were transformed into rectangular coordinates. The problem is that this system considers only 2D kinematics of the mechanism and ignores the lateral forces. Another development of the mathematical model is presented e.g. in Bentaher et al. (2008) and Karkee et al. (2011). Model of the three-point hitch is partly developed to 3D. The resultant force is resolved in all three directions, but the side movement of the hitch is still neglected.

The measuring system used in the presented project measures the forces in the five sensors placed at rods of TPH. The mathematical model of the mechanism is 3D not only by considering acting forces but, also including the side movement which was neglected by the other authors.

Mathematical description of the model was created using a multi-body formalism. The model and the measuring system was verified by comparing the results obtained by the algorithm with the results obtained from experimental measurements in laboratory and, subsequently, measurements performed during real ploughing.

Section snippets

Materials and methods

Forces measured in discrete times in the three-point hitch links were selected as input data for determination of the resulting force and the resulting moment acting on the tractor from implements. As a result of exertion of these forces vary tractor wheel loads and horizontal forces acting on the tyres touch the ground.

Following problems must be solved for determination these forces and moments:

•
mechanism kinematics. The result is a position of the three-point hitch in the space.
•
static

Results and discussion

Comparison of measured magnitude and components (in the direction of stand coordinate system) of loading force Fm with force FIMPL calculated by mathematical model from signals measured by sensors placed on TPH was made. Relative deviations between calculated and measured values are plotted in Fig. 8. Deviations are determined by following equations: $Δ Fm = Fm - FIMPL$ $Δ Fxm = Fxm - eFIMPLx \cdot FIMPL$ $Δ Fym = Fym - eFIMPLy \cdot FIMPL$ $Δ Fzm = Fzm - eFIMPLz \cdot FIMPL$ where eFIMPLx, eFIMPLy, eFIMPLz are components of unit direction

Conclusions

The authors developed an algorithm that uses forces measured in TPH to calculate resultant load force and moment of the implement acting on a tractor. Also, it calculates forces acting in the contact of wheels with the terrain. This algorithm is based on a multi-body model of a tractor equipped with TPH. The model is three-dimensional and covers TPH kinematics including vertical and side movement. The forces are determined on the basis of static balance. Verification measurement in laboratory

Acknowledgements

This work was part of the project DOPSIT Reg. No. CZ.1.07/2.3.00/20.0226 funded under the Operational Programme Education for Competitiveness and by European Regional Development Fund in the framework of the research project NETME Centre – New Technologies for Mechanical Engineering, project reg. No. CZ.1.05/2.1.00/01.0002, under the Operational Programme Research and Development for Innovation.

References (12)

A. Al-Janobi
A data-acquisition system to monitor performance of fully mounted implements
Journal of Agricultural Engineering Research
(2000)
H.F. Al-Jalil et al.
Design and performance of an adjustable three-point hitch dynamometer
Soil and Tillage Research
(2001)
H. Bentaher et al.
Three-point hitch-mechanism instrumentation for tillage
Biosystems Engineering
(2008)
R.J. Godwin et al.
A triaxila dynamometer for force and moment measurements on tillage implements
Journal of Agricultural Engineering Research
(1993)
M. Karkee et al.
Study of the open and closed loop characteristics of a tractor and a single axle towed implement system
Journal of Terramechanics
(2010)
M. Karkee et al.
Parameter estimation and validation of a tractor and single axle towed implement dynamic system model
Computers and Electronics in Agriculture
(2011)

There are more references available in the full text version of this article.

Cited by (31)

Load characteristics analysis of tractor drivetrain under field plowing operation considering tire-soil interaction
2023, Soil and Tillage Research
The drivetrain of a tractor is prone to fatigue failure under heavy load plowing operations. The load variation of its transmission shafting is affected by the "machine-soil" interaction environment, especially the tire-soil interaction. Therefore, a load transfer model of a tractor plowing operation composed of a drivetrain model, tire-soil interaction model, and tractor dynamics model was established, to analyze the load characteristics of the transmission shafting. For verifying the proposed model, the field plowing process was carried out experimentally. The driving wheels and shafting were discussed as influenced by the slip rate variation in the tire-soil interaction model. The fitting distribution characteristics of cycle average and range of transmission shafting in the rain-flow domain were obtained. The results showed that the established model can accurately simulate the speed and dynamic load characteristics of the tractor plowing operation. The driving wheel loads increased with the increase of slip rate except for the motion resistance. When the slip rate exceeded 25 %, loads of the transmission shafts changed steadily. The reliability of fit R² of the statistical distribution for transmission shafting load was greater than 0.94. The mean and variance of rear-drive half shaft torque were the largest, where fatigue failure was more likely to occur. The above theoretical model and results provide practical guidance for structural optimization design, fatigue durability analysis and reliability loading test of the tractor drivetrain.
Intelligent ballast control system with active load-transfer for electric tractors
2022, Biosystems Engineering
Citation Excerpt :
The tractor is the basic power unit for the whole process of agricultural production. At present, diesel engines provide the main motive power to drive the tractors, but it has problems with low fuel utilisation, high fuel consumption, and excessive exhaust emissions (Mileusnić, Petrović, & Đević, 2010; Porteš, Bauer, & Čupera, 2013; Janulevičius & Damanauskas, 2015). Much research and development has recently involved integrating electric drive technology into agricultural machinery with electric powered tractors becoming representative of intelligent and green agricultural equipment (Moreda, Muñoz-García, & Barreiro, 2016; Lagnelöv et al., 2021).
For agricultural tractors fixed ballast cannot provide high-efficiency traction under time-varying resistance in the field. Combining the characteristics of electric tractors with high-weight battery packs, this paper develops an intelligent ballast control system including a battery position adjustment (BPA) mechanism and an active ballasting control method. A tractor traction performance prediction model was developed to predict traction performance parameters and load-transfer in real time. The movement of the battery pack enables load-transfer based on the BPA. To ensure the lowest sliding rate of optimal tractive efficiency, an active ballasting control method based on a particle swarm optimisation algorithm was proposed that enabled control of the optimal battery position. The results of MATLAB/Simulink simulation indicate that the traction resistance after grading and pre-treatment not only reduced the frequency of change in the resistance signal but also retain the original trend. The results of a hardware in the loop test showed that the average tractive efficiency in the mode of active ballasting mode higher than that of the no ballasting mode (increased by 6.6%) and fixed ballasting mode (increased by 4.7%). The mean wheel slip in active ballasting mode was lower than that of the no ballasting mode (decreased by 10.3%) and the fixed ballasting mode (decreased by 4.9%). In addition, the front axle dynamic load distribution ratio in active ballasting mode was always greater than 0.2, which ensured the operational stability of the tractor. This study provides theoretical support and technical reference for optimising the traction performance of electric tractors.
Differences in the wheel loads and contact pressure of the in-furrow and on-land rear tractor tyres with mounted and semi-mounted ploughs
2022, Soil and Tillage Research
Citation Excerpt :
SAMS software, a general tool for solving kinematics, statics and dynamics of steady and transient states of spatial mechanisms (Porteš, 1997), was used for both forming and solving the equations by multibody formalism. A detailed model of the tractor, including the laboratory-experimental verification of the calculation of the force effects in the tractor’s three-point hitch acting on the drive wheels has been published already (Porteš et al., 2013). Determining the contact area between the tyre and the field surface - especially in the furrow - is technically difficult.
The aim of the article is to demonstrate the effect of setting the length of the upper link of the three-point hitch on the change in the load of the in-furrow wheel and the on-land wheel of the tractor during ploughing. Furthermore, attention is paid to the load on the rear wheels together with the tyre inflation pressure and their effect on the contact pressure under the tractor wheels. The tractor’s inclination, in combination with the force and moment effects of ploughing, may not always lead to large differences in the contact pressures of the rear in-furrow and on-land wheels. The results for the tractor-mounted plough set showed the possibilities of balancing the load on the rear wheels of the tractor when changing the length of the upper link of the three-point hitch. For semi-mounted ploughs, changing the length of the link will not affect the difference in the load on the rear wheels of the tractor. The kinematic linkage of the semi-mounted plough suspension transmits the moment from the plough support wheel and loads the wheel in the furrow more. The results further document that the proper suspension of the ploughs and, in particular, the appropriate choice of tyre inflation pressure can achieve substantial changes in the contact pressure under the rear wheels of a plough tractor.
Theoretical analysis of the forces and torques acting on a tractor during ploughing
2021, Journal of Terramechanics
Citation Excerpt :
This affects the quality of the ploughing and fuel consumption. The dependence between the input forces, measured on a three-point hitch, and the output forces, seven independent forces acting between the ground and the tractor wheels, are described in the papers (Porteš et al., 2012; Porteš et al., 2013). This dependence, between the input and output forces, is solved by SAMS software, see (Porteš, 1997).
This paper presents a physical model of a four-wheeled tractor during ploughing. In this model, the wheels are approximated by ideal non-oscillating harmonic oscillators. The velocity of the tractor is considered to be constant, i.e., the tractor is in an equilibrium state of forces and torques. The equilibrium state is described by Euler’s laws of motion. Finally, an infinite approximation of the wheel stiffness is performed and an exact solution of the forces is presented.
Development of an easily adaptable three-point hitch dynamometer for agricultural tractors. Analysis of the disruptive effects on the measurements
2019, Soil and Tillage Research
Citation Excerpt :
On the other hand, dynamometer coupling joints should adapt to different implement dimensions. The use of any double frame three-point-hitch dynamometer implies a disruptive effect on the forces acting on the tractor (Portes et al., 2013), due to its mass and to the backward implement displacement. Optimisation studies have been carried out in order to minimize the mass and the longitudinal dimension of the dynamometer.
The quantification of all the forces and moments between a tractor and an implement, when linked through the three-point hitch, is interesting for different purposes, including the optimization of the implement design, the evaluation of the tractor settings or the application in precision agriculture. This work presents the development of a new double frame dynamometer to measure them. The design has been focused in the mechanical optimisation of it while making it easily adaptable to a wide range of tractors and implements.
A mathematical model has been developed to determine the forces and the moments at the different couplers between bodies of the tractor-dynamometer-implement system, taking into account the mechanical characteristics of the dynamometer and the inclination of the terrain where the tractor is working. Then the disruptive effect of the dynamometer on the forces acting on the tractor can be evaluated. Resultant longitudinal force between implement and soil is also determined, taking into consideration the inclination of the terrain and the mass of the implement. A prototype of the dynamometer has been built up and some initial field tests have been carried out to validate the design and the functionality of the dynamometer.
Observation of load transfer from fully mounted plough to tractor wheels by analysis of three point hitch forces during ploughing
2017, Soil and Tillage Research
Citation Excerpt :
The change in the tensile force in upper link was realised by changing its length. Because direct measurement of the tractor’s wheel loads during ploughing is difficult, we used a mathematical model for its calculation, which was experimentally verified and published by Porteš et al. (2013). Another objective was to determine the influence of upper link length on the fuel consumption per ploughed area, and performance (ha/h).
During in-furrow ploughing the wheel running in the furrow exposes the soil to greater risk of undesired compaction of the subsoil. This fact is due to a different load placed on the rear axle wheels of the tractor. The wheel moving in the furrow is loaded more than the wheel moving on the land. This fact is also reflected in fuel consumption and performance.
The aim of this paper was to analyse the possibility of eliminating the problem with different loads of the rear wheels by changing the length of the upper link of the three-point hitch. We also studied the impact of adjustments made on the economics of ploughing. During the experimental ploughing carried out for three lengths of the upper link, we have indirectly evaluated the load on the wheels. In the course of ploughing the exerted forces were measured by the strain gauge sensors attached to each link of the three-point hitch. These measured forces we used to calculate the load on individual tractor wheels using a verified algorithm that uses a multibody tractor model.
The results show that the large difference between the loads on the left and right rear wheels typical for in-furrow ploughing can be reduced by adjusting the length of the upper link of three-point hitch from the original 5 kN–1 kN. Changing the wheel load resulted in reduction of fuel consumption per ploughed area by 13.7% and increased performance, namely the area ploughed per unit time, by 6.45%.

View all citing articles on Scopus

View full text