• Journal of Biosystems Engineering
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• v.27 no.6
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• pp.479-490
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• 2002

A dynamic model of a power shuttle transmission was developed and its validity was verified using the experimental data obtained from a transmission test bench. A 40㎾, 4WD tractor was also modeled using an application software EASY5 to investigate parameters and their effects on the power shifting performance. For a tractor model, the manual reverse gear was replaced by a power shuttle transmission. The tractor model also included an engine, main-gears for transmission, wheels, differentials and planet gears. Using the tractor model, the effects of the parameters such as modulating pressure and time, engine speed, tractor speed. tractor weight. reverse to forward speed ratio and torsional damper on the transient characteristics at starting and shuttle shifting were investigated by the computer simulation. The transient characteristics were represented by variations in clutch pressure, torque transmitted to input shaft and driving wheels, and power transmission capacity of the clutch. It was found that the modulating pressure and time affected most significantly the torque transmission and shifting time. The input torque, axle torque, power transmission capacity of the clutch and transmission time all increased with increase in engine speed, tractor speed. tractor weight and ratio of reverse to forward speeds. However, the axle torque decreased with tractor speed. Both the axle torque and power transmission capacity of the clutch also decreased with the ratio of reverse to forward speeds.

• 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.18 no.4
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• pp.305-316
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• 1993

Fuel efficiency in tractor operations dep6nds on the selection of transmission gears and upon the engine being operated at or near maximum torque much of time. The objective of this study was to develop automatic control systems for tractor transmission ratio and governor setting so that the engine is operated at or near maximum torque as much of time as possible. An indoor test unit, which can be used to simulate tractor operation, was built in order to investigate the system design parameters and test the performance of the control system designed. The test-unit consists of engine, gear-type transmission, dynamometer, and control systems for transmission ratio and engine speed. Governor setting lever was controlled by a step motor, and the clutch and transmission levers were controlled by hydraulic cylinders and solenoid valves. The control systems showed good time responses which are assumed to be suitable for optimal tractor operation. The time required for shifting gears from clutch disengagement to engagement was about 1 second, which is almost the same as that for manual shift. And the settling time for engine speed control system was about 5 to 6 seconds.

• Journal of Biosystems Engineering
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• v.38 no.3
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• pp.171-179
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• 2013

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.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.380-384
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• 2014

This study focused on identifying the major noise source in a tractor cabin using experimental methods. The noise levels in a tractor cabin for different engine revolution speeds were analyzed to identify the noise source. The results showed that the power steering unit (PSU) was the major noise source in a tractor cabin. The PSU was moved to the outside from the inside of the cabin in order to reduce the noise in the tractor cabin. As a result, the noise levels on the left and right sides of the operator in the tractor cabin were reduced by 6.8 and 3.9 dB, respectively. Finally, the window method was introduced to evaluate the contribution of the transmission noise. The orders of significance in the tractor noise were the front, bottom, and left area, successively.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.4
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• pp.114-121
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• 2002

This paper describes the control system of the toroidal traction driver continuously variable-speed transmission(CVT) fur a tractor. The instrumentation system, the hydraulic power control system and the principle control scheme were introduced. Experimental tests in the bench and the tractor were conducted to validate the performance of the CVT utilizing the proposed controller. The speed of the vehicle was continuously changed to follow the speed set by driver under various operating conditions. Given the reduction ratio of the variator from 2.0 to 1.0, the settling time was about just 0.52 seconds which was satisfactory value for working with the tractor. It was also proved that the tractor could work with continuously variable speed under heavy load disturbances.

• Journal of Biosystems Engineering
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• v.19 no.4
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• pp.291-300
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• 1994

It is desired to operate tractor engines at or near maximum torque much of the time in field operation to increase fuel efficiency. To do this it is necessary to reduce engine speed and to shift gears to higher ratios as frequently as possible. Because of load variations in most drawbar work and inconvenience in gear shift, however, gear-type transmission are usually set in one ratio at unnecessarily high engine speeds, and engine-torque variations are used to compensate for changes in drawbar load. As a result, the most of time the tractor is not operated efficiently in terms of fuel consumption and work output. The objective of this study was to develop an automatic control system which is able to operate a tractor equipped with gear transmission under the optimal condition in terms of fuel efficiency with automatic governor setting and gear shift. An indoor experimental test set which can be used to simulate tractor operation, control engine speed and transmission ratio was developed in the previous paper. In this paper, the performance of the optimal operation system is reported. Through a series of tests, it was found that the automatic control system for optimal operation of tractors with gear transmission had a satisfactory performance.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.354-358
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• 1996

At design stage of the TRXI agricultural tractor transmission (New product of TongYang Moolsan Co., Ltd), the noise and vibration of the transmission were analyzed theoretically for the optimal design of the transmission . For this analysis, the finite element model was developed using a commercial computer software, ANSYS. The noise and vibration of the TRXI transmission housing were predicted by the modal analysis. Natural frequency of the TRXI transmission housing was ranged from 12.53Hz(1st mode ) to 30.05Hz(5th mode). The fifth mode took place at the bearing metal in the area of rear transmission housing and was very close to the gear mesh frequency (30.5Hz) of low rang gear at the low creep shifting . Based on the results , the bearing metal of the range shift housing was reenforced with the rib at design stage.

• Journal of Drive and Control
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• v.10 no.2
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• pp.30-36
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• 2013

Tractor is a farm vehicle that is designed to provide a high tractive effort at low speed. It is used for versatile agricultural tasks such as hauling a trailer, tillage, mowing and construction work. Most older tractors use a manual transmission. However, as the intensity of work increases, tractors equipped with automatic transmission become popular due to the work convenience. In order to give the operator a large degree of control in field work, 24 gears with automatic 8-speed and manual 3-speed are arranged in transmission. This paper deals with the gear train that is designed for 8-speed automatic transmission by the engagement of multi-disk clutches. The gear ratio for each speed as well as power transmission mechanism is analyzed through velocity analysis. In addition, constraints of mesh gear ratio are derived by investigating the power flow path in velocity diagram for the given 8-speed gear ratio.

• 연구논문집
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• s.32
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• pp.35-43
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• 2002

This study was performed to develop accelerated life test method of machanical parts using cumulative damage theory that used to model the fatigue of parts that receive variable load. The cumulative damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the cumulative damage theory, because test time can shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7. This accelerated test method was used to develop accelerated test method of gear reducer, hydraulic hose and bearing as well as agricultural tractor transmission and it is considered to be applied comprehensively to machanical parts the fatigue of which is happened by load or pressure etc.