• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1993.10a
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• pp.1127-1136
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• 1993

A mathematical model has been developed for the simulation of static stability of agricultural tractors. The model was based on Reichmann's model but modified to improve its shortcomings for practical applications. Two examples of model simulation were presented and showed its usefulness in evaluating the control and stability loss boundaries.

• Journal of Biosystems Engineering
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• v.37 no.3
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• pp.131-139
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• 2012

In this study, we developed a simulation program for the prediction of tractive performance of a tractor, by applying a widely used empirical model for tractive performance prediction of single tire, Brixius. The tractive performance prediction program can readily predict and estimate tractive performance according to various soil conditions and different specifications of tractors. The program was developed with the considerations of tractor's specification-related parameters (e.g., weight, tire size, and wheelbase of the tractor), a soil parameter (i.e., cone index which represents the soil strength), and operating conditions of the tractor (e.g., theoretical speed and driving types such as 2WD and 4WD). Also, the program was designed to provide tractive performance prediction results of tractors such as gross traction, motion resistance, net traction, and tractive efficiency, in the form of not only numerical values but also graphical visualization. To evaluate the feasibility of the program, we input three different soil conditions (which have different cone indexes each other) and tractor operating conditions to the program and analyzed the tractive performance from each input condition. From the analysis, it can be concluded that the developed program can be effectively utilized to predict the tractive performance under various soil conditions and driving types of tractors with different specifications.

• Journal of Biosystems Engineering
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• v.39 no.4
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• pp.261-266
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• 2014

Purpose: This study was conducted to serve as a basis for strengthening policy support and R&D to improve the domestic and international competitiveness of domestic agricultural machinery. Levels of satisfaction among farmers and service engineers were analyzed regarding the current quality of agricultural machinery and the primary consumers' propensity for replacement purchases. Methods: A survey was carried out targeting farmers in over 150 townships and 300 villages in South Korea who collectively used 711 tractors, 286 rice transplanters, and 221 combine harvesters. Furthermore, agricultural machinery service engineers from 20 different after-services were surveyed regarding the quality of main components in domestic agricultural machinery versus those in imported agricultural machinery. Results: The farmers' overall quality satisfaction ratings for tractors, rice transplanters, and combine harvesters ranged from 57.1% to 62.6% in consideration of operating performance, failure rate, and durability. Compared with imports, satisfaction ratings for domestic agricultural machinery were 19.1%p to 38.1%p lower for quality. Regarding engines, transmissions, hydraulics, planters, reapers, threshers, and electrical components, only 5.3% to 25.0% of service engineers indicated that domestic agricultural machinery was higher in quality compared with imports. By contrast, 33.3% to 78.9% of those surveyed indicated that domestic components were lower in quality compared with imports. Intent to purchase replacement agricultural machinery at the end of their respective products' lifecycles was indicated that they planned to purchase imported tractors, rice transplanters, and combine harvesters comprised 25.2%, 46.9%, and 43.9%, respectively. This clearly shows that a very high percentage of farmers were satisfied, particularly for transplanters and combine harvesters. Conclusions: The level of desire for purchasing imported agricultural machinery was very high among those who expressed intent to purchase replacement machinery. Therefore, strong policy support and R&D for domestic agricultural machinery is critical for improving competitiveness on the domestic and foreign markets.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2003.07a
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• pp.43-63
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• 2003

1) 명칭 농ㆍ임업용 트랙터 및 기계류(Tractors and machinery for agriculture and forestry) 2) 작업범위 동물과 관련하여 모든 기준이 되는 전자/전기적 측면과 전자신분인식장치를 포함하여 사용되는 원예, 조경, 관개 및 기타 관련 분야의 장비뿐만 아니라, 농ㆍ임업 분야에서 사용되는 트랙터, 기계류, 장치, 초지 작업 및 관련 장비에 대한 표준화 (중략)

• Journal of Biosystems Engineering
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• v.16 no.4
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• pp.355-362
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• 1991

The objective of this study was to develop an electronic-hydraulic depth control system. Simulation was carried out to investigate the responses of the control system, and indoor experiments were carried out to confirm the simulation results of the control system. Field experiments were carried out to compare the newly-developed electronic-hydraulic depth-control system with the existing mechanical-hydraulic position control system in terms of the performance of depth control. The electronic-hydraulic depth control system showed better performance than the existing mechanical-hydraulic hitch control system for the forward speeds of tractor less than 7 km/h. It is concluded that the new control system could be adapted to the existing tractors with slight modifications to the conventional mechanical-hydraulic hitch control systems.

• Korean Journal of Agricultural Science
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• v.37 no.1
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• pp.113-121
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• 2010

Land consolidation ratio for rice paddy fields reached to 64.7% as of 2008 in Korea, and this also accelerated automation of field machinery. Especially, research on autonomous tractors has been continuously conducted. Tillage is one of the labor-, energy-, and time-consuming field operations. Most important requirements for autonomous tractors would be travelling path planning and electronic system to control the tractor to follow the path. The instruction of computer was required to conduct the tillage operation in field with unmanned traveling tractor. This instruction was coincidently used in the control of the traveling path and the motion of tractor. The objectives of the study were 1) to characterize and model tillage operating sequence, turning pattern, and 2) to develop tillage path formation programs for autonomous tractor and evaluate the performance.

• Journal of Biosystems Engineering
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• v.23 no.6
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• pp.539-548
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• 1998

This study was intended to develop a load spectrum acting on a transmission of agricultural tractors. Transmission loads were measured at the input shaft of the transmission and final drive shaft of the tractors. The measurement were conducted in five field conditions at two speed levels under plowing operations in Korea. Two torque transducers were developed for the respective load measurements and other necessary instrumentations were made to collect the data and store them in a data logger. The time-histories of the torque loads were analyzed and transformed into the load spectra using the rainflow counting and Smith-Watson-Topper methods. Comparisons of the load spectra developed under different conditions were made to investigate their characteristics. The effects on the load levels of soil and plowing speeds were also investigated. Finally, a load spectrum combining the results of the spectrum analysis was developed and proposed as a load source for the reliability test of transmissions.

• Journal of Biosystems Engineering
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• v.17 no.4
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• pp.326-335
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• 1992

This study was carried out to develop a measurement and analysis system of ride vibrations of tractors. The system consists of a portable digital computer, a PCL-812 PG interface card for A/D conversion, two accelerometers, two signal conditioners, a DC-AC power inverter and a DC power supplier. The computer programs installed in the system for data acquisition and analysis were also developed. It was intended that the system should be cheap enough to be afforded by college laboratories but reliable in its functions of measurement and analysis. Characteristics of the components and methods used in the system development were discussed.

• Journal of Drive and Control
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• v.15 no.3
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• pp.36-42
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• 2018

Agricultural tractors require frequent shifting to improve operation efficiency, and PST (Powershift Transmission) is considered as a suitable transmission. However, due to the inherent characteristics of the PST, shocks arise during shifting, which imparts a negative effect on the operator. Therefore, in order to improve the transmission performance of the tractor PST, researches on various methods including the hydraulic system circuit, the engine input speed control, and the mechanical system of the transmission are steadily being conducted. In this study, in order to reduce the impact of PST on a shift based on SimulationX software, we analyzed the characteristics of the input signal of PCV (Pressure Control Valve) through sensitivity analysis and verified the simulation model through actual vehicle test. Optimization was performed for minimizing the shift shock for some of the parameters of the input signal at constant temperature and RPM conditions.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.1-9
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• 2010

A mathematical model was developed to predict the fuel consumption rate consumed by agricultural tractors under arbitrary loaded conditions. The model utilizes the measured data on the fuel consumptions at the full load and at the rated engine speed with partial loads, which can easily be obtained from the official OECD tractor test reports. It was found from the analysis of the measured fuel consumption data that the fuel consumptions at two different speeds does not change with power. The model was developed based on this fact and validated with the measured data of the 159 tractor test reports. The fuel consumptions predicted by the model were compared with those measured under the partially loaded conditions specified in the official OECD tractor test code II. The percent errors of the predicted fuel consumptions were in a range from 0.36 to 2.86% which assured that the developed fuel consumption model can be used practically to predict the fuel consumptions at any speed and power combinations. It was also shown that the developed model predicts the fuel consumption rate better than the Grisso's model.