• Journal of Biosystems Engineering
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• v.16 no.4
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• pp.346-354
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• 1991

Turning behavior of tractor-trailer system was studied to guide the tractor and trailer. Based upon kinematic relationship between the tractor and the trailer, a mathematical model was developed and analyzed by computer simulation. A field test was carried out to verify the mathematical model. Following conclusions were drawn from this study. 1. A mathematical model and a simulation program for turning behavior of tractor-trailer system were developed. 2. The results of the field tests showed that the RMS errors were less than 0.33m and the mathematical model based upon kinematic relationship can be used for mapping guidance system for tractor and trailer. 3. As the steering angle was increased, the turning radius was decreased. When the tractor travelled at the low speed, the travel speed of the tractor did not affect turning radius but did affect running time and stability for steering. 4. When the tractor travelled under the critical velocity, the towed trailer followed smoothly. When the the tractor travelled faster than the critical velocity, the towed trailer oscillated. The critical velocity was determined from the specification of the tractor and the trailer.

• Journal of Drive and Control
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• v.17 no.1
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• pp.27-36
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• 2020

The aim of this study is to design a simulation model for an electric All-Wheel-Drive (AWD) tractor to evaluate the performance of the selected component and agricultural work ability. The electric AWD tractor consists of four motors independently for each drive wheel, and each motor is combined with an engine generator, a battery pack, and reducers. The torque data of a 78 kW-class tractor was measured during plow tillage and driving operation to develop a workload cycle. A simulation model was developed by using commercial software, Simulation X, and it used the workload as the simulation condition. As a result of simulation analysis, the drive system, including an electric motor and reducers, was able to cope with high load during plow tillage. The SOC (State of Charge) level was influenced by the output power of the motor, and it was maintained in the range of 50~80%. The fuel consumed by the engine was about 18.23 L during working on a total of 8 fields. The electric AWD tractor was able to perform agricultural work for about 7 hours. In the future study, the electric AWD tractor will be developed reflecting the simulation condition. Research on the comparison between the simulation model and the electric AWD tractor should be performed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5357-5365
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• 2013

In this paper, we propose that a model based design for a electric tractor system by using ASM(Automotive Simulation Models). Before developing a realistic electric tractor, it is essential that defining the capacities of power sources and optimizing the parameters of electric tractor. In additionally, because the electric tractor must have not only driving function but also working function, two PMSM are used at electric tractor. ASM which is based on simulink and Carsim were used to design a electric system and powertrain of electric tractor. For verifying the electric tractor system, we compared the design parameters such as max power, state of charge, drive distance, velocity which were carried out by the simulation and experimental method. The predicted results by the development model were in good agreement with the simulation results. According to simulation of tractor, it is possible to arrange the advanced research of dynamical characteristic of tractor and present the guidelines for the electrical driving system.

• Journal of Drive and Control
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• v.17 no.2
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• pp.19-27
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• 2020

The purpose of this study was to suggest design criteria for the HMT (hydro-mechanical transmission) of a 55 kW-class agricultural tractor, develop a simulation model, and evaluate its performance such as axle rotational speed, tractor speed, and power transmission efficiency. In this study, the HMT comprised a compound planetary gear and a HSU (hydro-static unit), and the compound planetary gear comprised two planetary gear sets. The HMT has three gear stages, and the maximum tractor speed was selected as 40 km/h. The simulation time was set at 2736 hours considering the lifetime of the tractor, and the simulation was performed for each gear stage at the engine-rated power conditions. As a result of the simulation, the axle rotational speeds for each gear stage were 39, 77, and 158 rpm, respectively. The range of tractor speed for each gear stage were 1.05-10.22 km/h, 10.74-20.17 km/h, and 20.70-41.40 km/h, respectively. The APE (absolute percentage gear) for the tractor's maximum speed between target value and simulation results were 2.20%, 0.85%, and 3.50%, respectively. Also, the power transmission efficiency for each gear stage were 0-75%, 72-81%, and 69-81%, respectively. The simulation results for the power transmission efficiency of the HMT were similar with the results of the previous research. This was a basic study on the development of the HMT for an agricultural tractor. In future studies, it is necessary to develop a tractor platform and evaluate the performance. The comparison between the simulation model and the HMT tractor should be performed.

• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.298-309
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• 1990

A mathematical model was developed to simulate sideways overturning of agricultural tractor-trailer systems. Sideways overturn of a tractor-trailer system was described by oscillatory motions of the tractor with respect to the first and second tipping axes, and of the trailer with respect to the drawbar hitch point when either the tractor or trailer rides over an obstacle on slopes. By a computer simulation, critical slope angles of the ground on which the tractor-trailer system is likely to sideways overturn were evaluated under the given operational conditions. Validity of the proposed mathematical model was proved by comparing the results of computer simulation and experiment with a model tractor-trailer system. A close agreement was observed between the two results.

• Korean Journal of Agricultural Science
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• v.43 no.1
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• pp.116-126
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• 2016

The objective of this study is to predict the fuel efficiency of an agricultural tractor. The fuel efficiency of the tractor during rotary tillage was predicted using numerical modeling. A numerical model was developed using Simulation X. Based on tractor power flow, numerical modeling consisted of an engine, transmission, PTO (power take off), and hydraulics. The specifications of major components utilized in the numerical model were the same as those of a 71 kW tractor (field test tractor). The load that was inputted for fuel efficiency prediction into the simulation model was obtained from a field test. Fuel efficiency predictions were conducted by comparing field test results and simulation results. In addition, it was performed by dividing the rotary tillage and steering section. Main results are as follows: first, t-values of engine torque were measured to be 0.31 in the rotary tillage and 0.92 in the steering section. Second, t-values of fuel consumption were measured to be 0.51 and 5.41 in the rotary tillage and the steering section, respectively. Finally, t-values of fuel efficiency were measured to be 1.72 and 40 in the rotary tillage and the steering section, respectively. The results show no significant differences with t-values of less than 5% in the rotary tillage. But, it shows significant differences in the steering section. Therefore, simulation for accurate fuel efficiency prediction requires a suitable algorithm or detailed design of the simulation model in the steering section.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1157-1165
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• 1993

The influence of tire characteristics is investigated by the simulation of an agricultural tractor. First the simulation of the tire is discussed. Different models are proposed and evaluated on their validity and their applicability . Also the practical measurement of some parameters is discussed. In a second paragraph the tractor model used in presented. In a second paragraph the tractor model used is presented. In the third part some results of the simulation are communicated . Beside the normal motions along and around the lateral axis, special attention is attracted on the hop. But one of the conclusions is that the simulation of hop is not possible without non-linear elements.

• Journal of Biosystems Engineering
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• v.29 no.5 s.106
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• pp.395-406
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• 2004

Most of tractors in the world have manual gear transmission, and some of small tractors have hydrostatic trans-mission(HST). Since the HST is expensive and has low power efficiency, it is being used for only small garden tractors. The continuously variable transmission(CVT) is an alternative to the HST or power-shift gear transmissions. The driver of the CVT tractor doesn't have to operate a shift lever since the CVT controller automatically controls the speed of tractor. Thus, it is much easier to operate the CVT tractor. For the easy and stable control of the CVT tractor, an appropriate control algorithm should be developed and the dynamic modeling should be carried out before making the prototype of CVT controller. This study was conducted to develop a simulation model of the CVT control system needed to develop a PID control algorithm. The simulation model consisted of variator dynamics, hydraulic system and control computer. And the simulation model was verified by experiment. The results obtained in this study can be utilized in the design of CVT tractors for practical use, but a lot of field tests and improvement of softwares would be necessary.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.549-560
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• 1998

The dynamic model of a tractor-trailer system developed in the first part of this paper was verified in this article by comparing the simulated acceleration responses of the system with actually measured ones. A commercially available tractor and a trailer were used for the verification test. Values of the model parameters were measured or theoretically derived if the measurement was practically impossible. The tractor-trailer system was operated with different forward speeds over three equally spaced half-sine bumps on the flat concrete surface. Results of the verification tests showed that autospectra of the measured and simulated accelerations of the tractor-trailer system agreed well up to the frequencies slightly feater than the fundamental frequencies of the ground excitations and at the frequencies of engine excitations. The mean of normalized errors of the simulated responses to the measured ones was estimated to be less than 10% for all the test runs. The peak responses in the autospectra also coincided well both in the frequency and magnitude.

• Journal of Biosystems Engineering
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• v.22 no.4
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• pp.421-432
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• 1997

This study was conducted to investigate dynamic characteristics of agricultural tractor with a particular interest in ride vibrations when it is subjected to various excitation forces. As the first part of it this paper describes development of dynamic model of a tractor-trailer system and its equations of motions. An 3 dimensional 16-degree-of-freedom dynamic model for a tractor-trailer system was developed and its equations of motions were derived, which will be used to investigate the effects of irregular ground surface and excitation forces due to the engine mounted on the tractor. And the excitation forces were also formulated analytically. The transition matrix method and QR algorithm were proposed for numerical solution of the equation of motions fur the developed model. The later parts of the study will include a proof of the model and optimization from which tractors can be designed to minimize the ride vibrations. This will be presented in the second and third papers to be followed shortly.