• Korean Journal of Agricultural Science
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• v.49 no.4
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• pp.937-948
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• 2022

Agricultural operations are performed in uneven environments by attaching an implement on the 3-point hitch of a tractor. A high load is thus placed on the 3-point hitch, and fatigue and failure of the hitch may occur during agricultural operations. In this study, a dynamic simulation model was developed to predict the load occurring on the eyebolt of a 3-point hitch, which is the main damaged component. The simulation model was developed and validated using agricultural data as simulation input and validation data. The dynamics model was developed using the specifications of a 78 kW class tractor. A measurement system was constructed to measure the simulation input and validation data. The simulation model was validated using a traction load on an eye bolt, which was measured during plow tillage operation. The measurement results showed that the average traction load on the left and right lower link and the top link were 8,099.97, 4,943.06, and 636.11 N, respectively. The simulation results and the measured traction load on the left eyebolt were respectively 610.30 and 597.15 N. The simulation results and measured traction load on the left eyebolt were respectively 1,179.78, and 1,145.06 N. The error between the simulation and measurement data was roughly 2% on the left eyebolt and 3% on the right eyebolt.

• Journal of Power Electronics
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• v.16 no.1
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• pp.362-373
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• 2016

The on-line measurement of high-power IGBT collector current is important for the hierarchical control and short-circuit and overcurrent protection of its driver and the sensorless control of the converter. The conventional on-line measurement methods for IGBT collector current are not suitable for engineering measurement due to their large-size, high-cost, low-efficiency sensors, current transformers or dividers, etc. Based on the gate driver, this paper has proposed a current measuring circuit for IGBT collector current. The circuit is used to conduct non-intervention on-line measurement of IGBT collector current by detecting the voltage drop of the IGBT power emitter and the auxiliary emitter terminals. A theoretical analysis verifies the feasibility of this circuit. The circuit adopts an operational amplifier for impedance isolation to prevent the measuring circuit from affecting the dynamic performance of the IGBT. Due to using the scheme for integration first and amplification afterwards, the difficult problem of achieving high accuracy in the transient-state and on-state measurement of the voltage between the terminals of IGBT power emitter and the auxiliary emitter (u_Ee) has been solved. This is impossible for a conventional detector. On this basis, the adoption of a two-stage operational amplifier can better meet the requirements of high bandwidth measurement under the conditions of a small signal with a large gain. Finally, various experiments have been carried out under the conditions of several typical loads (resistance-inductance load, resistance load and inductance load), different IGBT junction temperatures, soft short-circuits and hard short-circuits for the on-line measurement of IGBT collector current. This is aided by the capacitor voltage which is the integration result of the voltage uEe. The results show that the proposed method of measuring IGBT collector current is feasible and effective.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.447-452
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• 2001

An automated system is developed to perform fatigue crack growth tests under constant effective stress intensity factor range ${\Delta}K_{eff}$. In the system, crack length and crack opening load are measured in real-time by using the unloading elastic compliance method. The system consists of two personal computers, an analogue electrical subtraction circuit, a stepping motor, a stepping motor driver, a PIO board, and the application software used to integrate the whole system. The performance of the developed system was tested and discussed performing constant ${\Delta}K_{eff}$ crack growth tests on a CT specimen of 7075-T6 aluminum alloy. The performance of the system is found to be strongly dependent on the accuracy of measurements of crack opening load. Besides constant ${\Delta}K_{eff}$ testing, the system is expected to be successfully applied for automation of various fatigue tests.

• Journal of the Semiconductor & Display Technology
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• v.3 no.2
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• pp.23-26
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• 2004

Thin film is one of the most general structures used in micro-electro-mechanical systems (MEMS). To measure the mechanical properties of SU-8 film, tensile testing was adopted which offers not only elastic modulus but also yield strength and plastic deformation by load-displacement curve. Tensile testing system was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• Smart Structures and Systems
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• v.3 no.3
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• pp.373-384
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• 2007

For structural health monitoring (SHM) of civil infrastructures, displacement is a good descriptor of the structural behavior under all the potential disturbances. However, it is not easy to measure displacement of civil infrastructures, since the conventional sensors need a reference point, and inaccessibility to the reference point is sometimes caused by the geographic conditions, such as a highway or river under a bridge, which makes installation of measuring devices time-consuming and costly, if not impossible. To resolve this issue, a visionbased real-time displacement measurement system using digital image processing techniques is developed. The effectiveness of the proposed system was verified by comparing the load carrying capacities of a steel-plate girder bridge obtained from the conventional sensor and the present system. Further, to simultaneously measure multiple points, a synchronized vision-based system is developed using master/slave system with wireless data communication. For the purpose of verification, the measured displacement by a synchronized vision-based system was compared with the data measured by conventional contact-type sensors, linear variable differential transformers (LVDT) from a laboratory test.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.201-208
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• 2000

Axial load distribution in model piles was measured by fiber Bragg Grating(FBG) sensor to investigate a possibility of analyzing the load transfer mechanism by Fiber Optic sensor system. Since FBGs of different wave lengths can be multiplexed in an optical fiber, the installation of sensor system and the measurement of strains are relatively simple, compared with consisting strain gages. In this study, FBG sensors and electric strain gages were embedded in the same piles and the distributions of load transfer by two sensor systems were measured. It was observed from the test results that the variations of axial load by both systems showed insignificant difference and that the measurements by FBG were smoother than those by strain gage. Under the environments of laboratory testing, survival rate of embedded FBG system was higher than that of strain gage. Therefore, it was concluded that the use of FBG sensor has a great potential for the measurement of load transfer for pile foundation.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.1803-1804
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• 2006

The purpose of this paper is to implement a Labview based TFDR Real Time system through the instruments of Pci eXtensions for Instrumentation(PXI). The proposed load impedance measurement algorithm was verified by experiments via the implemented real time system. The TFDR real time system consisted of the reference signal design, signal generation, signal acquisition, algorithm execution and results display parts. To implement real time system, all of the parts wore programmed by the Labview which is one of graphical programming languages. In the application software implemented by the Labview we were able to design a suitable reference signal according to the length and frequency attenuation characteristics of the target cable and controled the arbitrary waveform generator(ZT500PXI) of the signal generation part and the digital storage oscilloscope(ZT430PXI) of the signal acquisition part. By using the TFDR real time system with the terminal resistor on the target cable, we applied to the load impedance measurements. In the proposed load impedance algorithm a normalized time-frequency cross correlation function and a cross time-frequency distribution function was employed to calculate the reflection coefficient and phase difference between the input and the reflected signals.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1107-1114
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• 2005

The running condition of multi-system air conditioner is prone to vary largely as it is designed for individual conditioning in each space of middle and small sized buildings. This leads to overcooling in case of partial load run, while the lack of capacity happens in case of full load run. Besides these, there exist such problems as instabilities due to the uneven refrigerant distribution caused by fluctuation of load and the change in piping line. Based upon the basic study on the function characteristics found in parts needed for maximized system working design in order to troubleshoot, the system functioning pattern should be identified through the different tests with various operating circumstances and the analysis models should be developed. With this ground, the control logic has to be made to have a control over capacity and make possible the efficient distribution of refrigerant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1204-1209
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• 2005

In-situ measurement was made to evaluate chiller performance and thermal storage density of an ice thermal storage system. The system belonged to a big hotel and the measurement was conducted during late October. Owing to very small cooling load, the data logging was possible for a single thermal storage cycle. However, operation history of the chiller showed a relatively good spectrum of data for performance evaluation. COP and thermal storage density were calculated. The COP at full load was about 4.07, which was lower than $4.8\~6.4$ of new chillers. The measured storage density was about $10.9RT-h/m^3\;(=152MJ/m^3)$, which also was lower than a criterion of normal performance $(above\;13.0RT-h/m^3\;or\;181MJ/m^3)$. The study result provides technical basis for quantitative ESCO business scenario.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.17-26
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• 2010

Maintenance of the roads and bridges is a major issue for all road administrators around the world, and various initiatives are being implemented in each region for the purpose of controlling the ever increasing road maintenance cost while ensuring the safety of the vehicles driving. Efforts for such initiatives have also been made in Asia and initiatives for managing heavy-weight vehicles have recently gained momentum in Korea and Japan. We have developed a technology for unevenly installing bar-shaped sensors (piezo quartz sensors) to enable dynamic axle load measurement at a highly accurate level, and have estimated our measurement accuracy of axle load/gross weight, etc. on an actual road. The measurement accuracy of the axle load/gross weight varies significantly depending on the number of sensors installed. In our implementation, the target accuracy was set to below ${\pm}5%$ for gross weight measurement so that automatic regulation can be applied. We have achieved our target by installing 8-point measurement system. However, to have this technology widely accepted, it was necessary to reduce the system size so that it can be easily implemented. Therefore, we have estimated the relationship between the measurement accuracy and the system size (number of measurement points), and have come up with the proposal of 3-point measurement as an optimum number of measurement points, and have estimated its performance on an actual road. Additionally, we evaluated the relationship between the measurement accuracy and vehicle velocity.