• 조명전기설비학회논문지
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• 제15권5호
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• pp.55-60
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• 2001

현재 대부분의 전동지게차 충전기는 3상의 일정전류제어와 일정전압제어 방식으로 운전되고 있으며, 이러한 충전방식은 충전기의 이용률을 저하시킬 뿐 아니라 축전지의 수명을 단축시키는 등의 단점을 가지고 있다. 이러한 문제점을 보완하기 위해서, 본 논문에서는 기존의 방식에서 일정전력제어 및 부가적인 제어모드를 첨가한 다중제어 충전방식을 제시하였다. 전체 제어시스템은 저가의 micro-controller를 적용하여 디지털화 시킴으로써 제어정도 및 신뢰성을 향상시켰으며, 제어장치의 소형화와 함께 저 가격화를 실현하였다.

• 대한안전경영과학회지
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• 제10권3호
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• pp.117-126
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• 2008

RFID system the key technology of ubiquitous era, has been emphasized in logistics. Logistic enterprises are required to apply RFID systems considering their investment costs, actual effectiveness, operational satisfaction and so on. For such a purpose, many applicable methods of RFID system have been developed A method that RFID tags are directly attached to products or pallets is utilized in most cases. However, this method requires expensive investment cost, frequent replacement of damaged tags for the small and medium (SM) third party logistics. In this paper, we analyze statistically the current status and requirements of SM third party logistics. Based on their requirements, we propose the realtime warehousing-delivery management by the method to attach a RFID tag to each warehouse rack, together with the economy analysis index in order to evaluate economical efficiency. Consequently, this method is expected to reduce Investment cost and to improve operational effectiveness and satisfaction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.22-25
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• 2001

In this paper, a fuzzy advance angle control method is described to drive an industrial low voltage SRM (Switched Reluctance Motor) for 10kW forklift truck. SRM has a highly non-linear characteristic that is due to change the rotor and stator. And low voltage SRM is designed that its phase resistance and phase inductance is very low to inject high current into the phase windings. In this reason, the proper current control is necessary to drive the low voltage SRM efficiently. SRM has positive torque at increasing inductance region and negative torque at decreasing inductance region. Due to this reason, the current has to be built up in the increasing phase inductance part as soon as possible. Therefore, the phase switch must be turned on before the phase inductance increases, and this angle is called as the advance angle. Also, the phase current has to be dropped before the phase inductance decreases. Fuzzy logic is a flexible and general-purposed method of implementing non-linear functions and as such it is useful in control applications. Consequently, we designed a fuzzy advance angle controller to control the phase current appropriately.

• 한국포장학회지
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• 제25권3호
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• pp.131-137
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• 2019

Carton clamps, one of forklift attachments, allow users to quickly handle shipping units such as unitized loads, large shipping cases, or crates without the requirement of pallets. As the use of palletless handling by clamp trucks increases, so does the need for simulation research on clamp truck handling. The frictional characteristics for various contact conditions of corrugated paperboards and their constituent boards were analyzed to obtain the data needed in the computer simulation for the handling of carton clamp truck. The overall mean of static-frictional coefficients between selected corrugated paperboards was 0.38 (±0.01), which was 1.3~1.6 times greater than 0.23~0.29 of the frictional coefficients between boards. The overall mean of static-frictional coefficients between the corrugated paperboards and the rubber contact pad was 0.82 (±0.02), which was about 1.1 to 2.8 times greater than 0.29~0.78 of the static-frictional coefficient between the linerboard and the rubber contact pad. The overall mean of kinetic-frictional coefficients between the corrugated paperboards was 0.35 (±0.01), and 0.76 (±0.02) between the corrugated paperboards and the rubber contact pad.

• 한국소음진동공학회논문집
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• 제24권3호
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• pp.236-246
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• 2014

This paper presents a hybrid rubber mount with magnet to isolate effectively the vibration in vehicle, forklift, and so on. The hybrid mount does not have any controller of the magnetic force. Dynamic stiffness of the mount is reduced by only magnetic suction according to the applied magnetic field and damping coefficient increased. Performance of conventional rubber mount with using electromagnet has been investigated by MTS Tester. The governing equation of the hybrid mount was derived and verified by comparison with experimental and theoretical results. The equation can be used practically and usefully in the design of the mount and analysis of the mounting system. The hybrid mount provides excellent performance in vibration isolation and its structure is very simpler than active with controller and a semi-active mount with a functional fluid. Furthermore, production cost of the mount using permanent magnets is very lower than that of the active mount with electromagnets. Therefore, commercial potential of the mount is very high.

• Journal of Electrochemical Science and Technology
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• 제9권3호
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• pp.184-194
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• 2018

In this paper, we propose a rapid-charging system for the lithium-ion battery (LIB) packs used in electric forklifts. The battery offers three benefits: reduced charge time, prolonged battery life, and increased charging efficiency. A rapid-charging algorithm and DC/DC converter topology are proposed to achieve these benefits. This algorithm is developed using an electrochemical model, which controls the maximum charging current limit depending on the cell voltage and temperature. The experimental use of a selected 18650 LIB cell verified the prolongation of battery life on use of the algorithm. The proposed converter offers the same topological merits as a conventional resonant converter but solves the light-load regulation problem of conventional resonant converters by adopting pulse-width modulation. A 6.6-kW converter and charging algorithm were used with a forklift battery pack to verify this method's operational principles and advantages.

• 드라이브 ㆍ 컨트롤
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• 제17권3호
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• pp.47-56
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• 2020

As a shift control of automatic transmission was managed with the electronic control unit (ECU), shift quality which is a measure of shift shock during gear change has markedly improved. However, the initial clutch pressure control of the clutch filling phase should continue to rely on the predetermined control input since the input and output speeds are unchanged until the shifting process attains the inertia phase. It is critical to minimize the clutch response time and control the clutch pressure accurately at the end of clutch fill to achieve quick shift response and smoothness. Advanced transmission companies have adopted an auto calibration method which establishes the databases for the clutch piston fill-up attributes and the frictional characteristics of the disks. In this study, a distinctive auto calibration algorithm for forklift transmission under development is proposed and verified with the real-vehicle test. The experimental calibration results showed consistent turbine dynamics at the initial stage of shifts with the properly calibrated clutch-fill control parameters. By using this technique, it is necessary to finalize the shift control for the various operation conditions.

• 드라이브 ㆍ 컨트롤
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• 제14권4호
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• pp.71-78
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• 2017

The power train of hydro-mechanical continuously variable transmission (HMCVT) for 8-ton class forklift includes hydro-static units, hydraulic multi-wet disc brake & clutches and complex helical & planetary gears. The helical & planetary gears are key components of HMCVT's power train wherein strength problems are the main concerns including gear bending stress, gear compressive stress, and scoring failure. Many failures in power train gears of HMCVT are due to the insufficient gear strength and resonance problems caused by major excitation forces, such as gear transmission error of mating gear fair in the transmission. In this study, wherein excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate the power train gears' critical speeds. Mode shapes and natural frequencies of the power train gears are calculated by CATIA V5. These are used to predict resonance failures by comparing the actual working speed range with the critical speeds due to the gear transmission errors of HMCVT's power train gears.

• 산업경영시스템학회지
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• 제44권4호
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• pp.145-153
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• 2021

Automated Guided Vehicle (AGV) is commonly used in manufacturing plant, warehouse, distribution center, and terminal. AGV is self-driven vehicle used to transport material between workstations in the shop floor without the help of an operator, and AGV includes a material transfer system located on the top and driving system at the bottom to move the vehicle as desired. For navigation, AGV mostly uses lane paths, signal paths or signal beacons. Various predominant sensors are also used in the AGV. However, in the conventional AGV, there is a problem of not turning or damaging nearby objects or AGV in a narrow space. In this paper, a new driving system is proposed to move the vehicle in a narrow space. In the proposed driving system, two sets of the combined steering-drive unit are adopted to solve the above problem. A prototype of AGV with the new driving system is developed for the comparative analysis with the conventional AGV. In addition, the experimental result shows the improved performance of the new driving system in the maximum speed, braking distance and positioning precision tests.

• 드라이브 ㆍ 컨트롤
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• 제20권1호
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• pp.41-47
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• 2023

The aim of this study was to develop a method for installing strain gauges on moving, lubricating oil-filled, and sealed parts, such as drive shafts of equipment, including construction machinery. A measuring device was constructed using an embedded CPU and an IoT sensor to measure the strain of the strain gauge, which allowed for the measurement of axial torque and axial force, and subsequent analysis. To verify the performance of the developed device, the axial torque and axial force of the forklift were measured during operation using a strain gauge attached to the inside of the drive shaft. This study confirmed the possibility of measuring and analyzing the strain of a moving part, such as the inside of a drive shaft, which is sealed and filled with hydraulic oil.