• 대한기계학회논문집
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• 제18권3호
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• pp.738-750
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• 1994

The load-sensing hydraulic system which was developed to improve energy efficiency of conventional hydraulic systems has its own properties. The instability of system responses, linearity of a servo valve, robustness for variation of external load, and dynamic interference between hydraulic motors are such properties which have much to do with control properties of the system. The load-sensing hydraulic system has instability tendancy because the load-sensing mechanism makes a positive feedback loop between the motor part and the pump part. A flow property of the servo valve can be said to be linear because the flow through the valve has nothing to do with a load pressure and the flow is strictly proportional to a valve opening which is adjusted by a valve command signal. The resultant control property can be said to be robust because the steady-state control performance is independent to the load actuated on the motor shaft. In the case when one pump simultaneously drives more than two hydraulic motors, the pump outlet pressure is determined by a hydraulic motor of the largest load pressure among all of the hydraulic motors, and, thus, the other motors are dominated by the largest load pressure. That is, the other motors can be said to be interfered by the motor of the largest load pressure.

• Smart Structures and Systems
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• 제12권6호
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• pp.661-678
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• 2013

In this paper, a wireless sensing system for structural field evaluation and rating of bridges is presented. The system uses a wireless platform integrated with traditional analogue sensors including strain gages and accelerometers along with the operating software. A wireless vehicle position indicator is developed using a tri-axial accelerometer node that is mounted on the test vehicle, and was used for identifying the moving truck position during load testing. The developed software is capable of calculating the theoretical bridge rating factors based on AASHTO Load and Resistance Factor Rating specifications, and automatically produces the field adjustment factor through load testing data. The sensing system along with its application in bridge deck rating was successfully demonstrated on the Evansville Bridge in West Virginia. A finite element model was conducted for the test bridge, and was used to calculate the load distribution factors of the bridge deck after verifying its results using field data. A confirmation field test was conducted on the same bridge and its results varied by only 3% from the first test. The proposed wireless sensing system proved to be a reliable tool that overcomes multiple drawbacks of conventional wired sensing platforms designed for structural load evaluation of bridges.

• 유공압시스템학회논문집
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• 제6권3호
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• pp.16-22
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• 2009

This paper deals with the issue of robust position tracking control and energy-saving control for a valve-controlled cylinder system using speed-controlled fixed displacement pump. The whole feedback control system is composed of a pair of interconnected subsystems, that is, valve-controlled cylinder system and load-sensing control system. From experiments it is shown that position tracking control in the load sensing control system can accomplish significant reduction in input energy to pump comparing to a conventional valve-controlled cylinder system, while exhibiting the same position tracking control accuracy.

• 한국정밀공학회지
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• 제15권2호
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• pp.134-145
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• 1998

The purpose of this paper is to construct a computer simulation system which can analyze and design the hydraulic excavator Theoretical analyses are performed on the hydraulic circuit and attachment of excavator with load sensing system. Databases are constructed for control valve opening areas, horsepower control and for load sensing regulator. For hydraulic components modularized programming techniques are applied which is expected to be utilized for software development of fluid power system. Through simulation an information of any point in hydraulic circuit can be obtained.

• Geomechanics and Engineering
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• 제24권4호
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• pp.337-348
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• 2021

Brillouin Optical Frequency Domain Analysis (BOFDA) is a distributed fiber optic sensing (DFOS) technique that has unique advantages for performance monitoring of piles. However, the complicated production process and harsh operating environment of offshore PHC pipe piles make it difficult to apply this method to pile load testing. In this study, sensing cables were successfully pre-installed into an offshore PHC pipe pile directly for the first time and the BOFDA technique was used for in-situ monitoring of the pile under axial load. High-resolution strain and internal force distributions along the pile were obtained by the BOFDA sensing system. A finite element analysis incorporating the Degradation and Hardening Hyperbolic Model (DHHM) was carried out to evaluate and predict the performance of the pile, which provides an improved insight into the offshore pile-soil interaction mechanism.

• 대한조선학회논문집
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• 제57권6호
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• pp.373-380
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• 2020

We have developed the hybrid prototype load cell structures. These developed load cell structures may increase the reliability of the load sensing by deriving the load values through the double sensing method through the vertical maximum deflection and bending stress of the simple beams. For this purpose, the structure design was performed so that the load value, the deflection and stress value could be output to the same value through the optimal structure design. The structurally designed dimensions reaffirmed the accuracy of the design through the structural analysis program and the matching of the load value and the deflection value. Based on the designed structural dimension, the prototype form was constructed through laser cutting and production using hot rolled steel materials. The developed prototype load cell structure can be used as good educational material in various subjects such as material mechanics, steel structure design, measurement engineering, and mechatronics engineering. It is also believed that the measurement system ideas can inform the occurrence of errors in the event of a problem, and if a major accident caused by a sensing error is predicted, it will show good utilization to prevent accidents.

• 전기전자학회논문지
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• 제27권3호
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• pp.308-312
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• 2023

게이트 전류 감지 구조는 LDO 레귤레이터가 오버슈트 또는 언더슈트 상황 발생 시 출력전압의 레귤레이션을 보다 효과적으로 제어하기 위해 제안되었다. 기존의 전형적인 LDO 레귤레이터는 부하전류가 변화할 때 레귤레이션 전압 변화가 발생한다. 하지만 게이트 전류 감지 구조를 이용하여 패스 트랜지스터에 있는 게이트 단자 전류를 공급/방전 함으로 인해 패스 트랜지스터의 동작 속도를 더욱 향상시킬 수 있다. 게이트 전류 감지 구조를 이용한 LDO 레귤레이터의 입력전압은 3.3 V ~ 4.5 V 이며 출력 전압은 3 V이고 부하 전류는 최대 250 mA의 값을 갖는다. 시뮬레이션 결과, 부하 전류가 250 mA 까지 변화할 때 약 9 mV의 전압 변화 값을 확인하였다.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.466-471
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• 2014

An asynchronous optical packet-switching (AOPS) node with load-balancing capability can achieve better performance in reducing the high packet-loss ratio (PLR) and time delay caused by unbalanced traffic. This paper proposes a novel dynamic load-balancing algorithm for an AOPS node with limited buffer and without wavelength converters, and considering the data flow distribution and service levels. By calculating the occupancy state of the output ports, load state of the input ports, and priorities for data flow, the traffic is balanced accordingly. Simulations demonstrate that asynchronous variant data packets and output traffic can be automatically balanced according to service levels and the data flow distribution. A PLR of less than 0.01% can be achieved, as well as an average time delay of less than 0.46 ns.

• 드라이브 ㆍ 컨트롤
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• 제21권1호
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• pp.53-58
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• 2024

With the recent development of intelligence and automation technologies for construction machinery, the demand for safety and efficiency of road-cutting operations has continued to increase. In response to this, a double-blade road cutter has been developed that can automatically cut roads. However, a double-blade road cutter has a load difference between the two blades due to the ground and wear conditions of the cutting blades. The difference in load between the two blades distorts the direction of travel of the cutter. In this study, a vision sensor-based driving guide technology was developed to correct the driving path of road cutters. In addition, we developed a load-sensing technology that detects blade loads in real-time and controls driving speed in the event of overload.

• Journal of Biosystems Engineering
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• 제18권4호
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• pp.358-370
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• 1993

In Korea, fruit grading has been mainly done manually, and manual grading depends on human sense. Thus it is subjected to human error and is not always as consistent as would be desired. Therefore, a study on the development of fruit grader was initiated to improve the consistency of fruit grading. The sensitivity for fruit weight of the conventional spring type weight grader has a tendency to decrease by physical characteristics of spring which is used as a weight sensing unit. This study was carried out to develop weight measuring device for establishing the base of weight sensing unit of electronic weight grader. This device consists of a weight sensor using load cell, data acquisition system, and a microcomputer containing program to calculate fruit weight. The weight measuring device using load cell was developed to increase sensitivity of fruit weight. The result of this study showed that the weight sensing unit of electronic weight grader contributed to the improvement of performance of weight measuring device.