• Journal of Drive and Control
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• v.21 no.1
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• pp.22-30
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• 2024

Gearboxes designed for reciprocating motion operating mechanisms operate under conditions where both the load and speed undergo continuous variations. When conducting durability tests on gearboxes designed for such applications, operating the target gearbox under conditions similar to the intended usage is essential. The gearbox must be operated for the required number of cycles to validate its durability under conditions mirroring its intended usage. This study devised an accelerated test method for gearboxes, which reduces operating angles and operational strokes. The reliability of the accelerated test was verified by comparing the stresses imposed on the gears under general and acceleration conditions through multi-body dynamic simulations. The results confirmed that the maximum contact stress levels under normal and accelerated conditions were within a 0.1% error range, indicating a minimal difference in the gear damage rates. However, a difference in the maximum contact stress results between the normal and accelerated conditions was observed when inertial forces acted on the output shaft due to the operational acceleration of the gearbox. Therefore, when conducting this acceleration test, caution should be exercised to ensure that the operational load on the gearbox, which affects inertia, does not significantly deviate from the conditions observed under normal operating conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.736-741
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• 2017

This paper examines the design for improving the wiper system of rotorcraft. During rotorcraft operation, the wiping performance and excessive clearance can decrease. The wiper system consists of a wiper arm assembly, motor, convertor and flex drive. If there is a problem with the wiper system, the operation ability decreases because the operation is restricted in a rainy environment. There are two main causes of the problem of the wiper system: the lifting forces acting on the wiper arm in aircraft flight and the excessive gap of the components. To remedy these two problems, the wiper arm was improved. The improvements included increased contact pressure on the wiper arm (spring tension), improved gear clearance, and material and shape changes. Durability test, aircraft ground test and flight test were carried out to verify the improved shape, and it was confirmed that the wiping performance and clearance problems were solved. Currently, the rotorcraft is operated without problem by applying the improved shape, and this design improvement process will be a useful reference for future rotorcraft development.

• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.285-295
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• 2018

Purpose: The aim of this study is to develop a three-wheel riding cultivator for improving the performance of the current four-wheel riding cultivators in the market. Methods: A prototype three-wheel riding cultivator with the rated power of 15.5-kW, a primary hydrostatic and a two-speed selective gear transmission shifts, front/rear three-wheel drive, a hydraulic wheel tread adjustment, and the mid-section attachment of the major implements was designed and constructed. Its specifications and basic performance are investigated. Results: The maximum speeds of the prototype at the low and high stages were measured to be approximately 7.31, and 11.29 km/h in forward travel, respectively, and approximately 3.60, and 6.37 km/h in rearward travel, respectively. The minimum ground clearance is shown to be 670 mm. The rotating speeds of the power takeoff (PTO) shaft at the low and high stages are shown to be approximately 795 and 1,140 rpm, respectively. The tread of the rear wheels, the minimum radius of turning, and the maximum lifting height of the parallel link device are measured to be within 1,320-1,720 mm, 2.80 m, and 390 mm, respectively. Approximately 25.3% and 74.7% of the total weight of the prototype are distributed in the front and rear wheels on flat ground, respectively. When the tread of rear wheels increased from 1,320 to 1,720 mm, the left and right static lateral overturning angles increased from $33.4^{\circ}$ to $39.1^{\circ}$ and from $29.0^{\circ}$ to $36.1^{\circ}$, respectively. Conclusions: The prototype three-wheel riding cultivator showed a wide range of travel and PTO speeds, high minimum ground clearance, small minimum radius of turning, and easy control of the rear wheel tread. Further, the easy observation of cultivating operations by mid-mounting the implements can improve quality of work. Therefore, the prototype is expected to contribute to the riding mechanization of cultivating operations for various upland crops in Korea.

• Journal of Digital Convergence
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• v.17 no.11
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• pp.207-213
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• 2019

The fuel-cut coast-down driving mode is activated when the acceleration pedal is released with transmission gear engaged, and it's a default function for electronic-controlled engine of vehicles. The fuel economy becomes better because fuel injection stops during fuel-cut driving mode. A fuel-cut detection method is suggested in the study and it's based on the speed, acceleration and road gradient data from GPS sensor. It detects fuel-cut driving mode by comparing calculated acceleration and realtime acceleration value. The one is estimated with driving resistance in the condition of fuel-cut driving and the other is from GPS sensor. The detection accuracy is about 80% when the method is verified with road driving data. The result is estimated with 9,600 data set of vehicle speed, acceleration, fuel consumption and road gradient from test driving on the road of 12km during 16 minutes, and the road slope is rather high. It's easy to detect fuel-cut without injector signal obtained by connecting wire. The detection error is from the fact that the variation range of speed, acceleration and road gradient data, used for road resistance force, is larger than the value of fuel consumption data.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.511-519
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• 2021

Slewing bearing is applied to the transmission of rotational power of the body and turret in a special vehicle for anti-aircraft weapons that overcomes the enemy flight system approaching at low altitudes with rapid response fire. When the turret load and impact load generated when shooting are combined in performing the combat mission of a special vehicle, structural stability must be secured to achieve a successful function. Among the components of the slewing bearing, the stability of the components against the complex loads acting by the turret drive and shooting was evaluated by considering the shape and material characteristics of the ring-gear, roller, and wire-race. As a research method for stability evaluation, based on engineering theory, the strength characteristics of the components were examined by numerical calculations. Finite element analysis was performed on components using the ANSYS analysis program. The results of theoretical analysis and the results of finite element analysis were very similar. A structural stability evaluation for the slewing bearing, which was performed mainly on the analysis, confirmed that the design strength of the slewing bearing determined in the preliminary design in the early stage of localization development was sufficient.