• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.12
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• pp.111-116
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• 2019

With the recent acceleration of industrial technologies and active research, wearable robot technologies have been applied to various fields. To study the utility of wearable robots, basic research on kinetic mechanisms of the human body, bio-signal analysis, and system control are essential. In this study, we investigated the basic structure of a wearable system and the operating principles of a driving mechanism. The control system and supporting structure, which comprise the driving mechanism, were designed and manufactured. Motion and load analyses were performed simultaneously for the design of the kinematic drive, and the driving mechanism was constructed by analyzing walking motion. The operating conditions of the cylinder were verified by stride via driving experiments. Further, the accuracy and responsiveness of the system were confirmed by comparison with actual motion, and the system safety was validated by applying loads.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.81-85
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• 2010

This paper deals with the issue of motion control of a single rod cylinder-load system using simple adaptive control (SAC) method. Prior to controller design, the experiment of open-loop response has been performed. Based on it, design parameters of transfer function are obtained. The effect of parallel feedforward compensator has been investigated by computer simulation, suppressing the oscillatory motion. Through experiments it is conformed that the SAC method gives good tracking performance compared to the PD control method.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.3
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• pp.110-120
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• 1996

The purpose of this study is to build up the control scheme that promptly controls the pressure in a hydraulic cylinder having small control volume, using a PCV(proportional control valve) and a digital computer. Object pressure control system has the character to be unstable easily, because the displacement-flow gain of the PCV is so large considering comparatively small volume of the hydraulic cylinder and the time delay of response of PCV is long. Considering the above-mentioned characteristics of the object pressure control system, in this study, a control system is designed with two degree of freedom scheme that is composed by adding a feed-forward control path to I-PD control system, and the reference model is used to decide control parameters. And through some experiments on FF-I-PD, the validity of this control method is confirmed.

• Tribology and Lubricants
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• v.11 no.1
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• pp.44-49
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• 1995

Friction characteristic of an engine crankshaft bearing is affected by revolution speed, applied loads, and viscosity of lubrication. So, experimental investigation is required to observe the friction characteristics using these factors. Hydraulic cylinder, servo controller system which can be modified the applied load, and test rig for the observation of the characteristics of engine crankshaft bearings were designed and fabricated, and some experiments were performed. Friction torque, journal locus and circumferential temperature variation of crankshaft bearing were measured according to applied load, revolution speed, and oil inlet temperature.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1993.12a
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• pp.57-62
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• 1993

To increase the fuel economy, a reduction of friction loss is important in engines. Experimental investigations have been required for reducing the friction loss of crankshaft bearings. Hydraulic cylinder, and servo control ler system which modified the applied load, and test rig for the observation of the characteristics of engine crankshaft bearings were designed and fabricated. Experiment is performed. Friction torque, journal locus and circumferential temperature variations of crankshaft bearings were measured with appling load, revolution speed, and oil inlet temperature, etc.

• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.6
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• pp.347-353
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• 2019

Electric-hydraulic sever cylinders are used in many offshore applications such as wind energy farms, solar farms and plants. Jack-up barges are often used for these offshore system operations. Jack-up barge control is up/down by hydraulic cylinder position control. Working in harsh environments can lead to changes in internal parameters. This nonlinearity makes precise control difficult. In order to overcome the problems, we proposed a method of unknown-parameter estimation algorithm based on measurements obtained by system. In this paper, we employee Unscented Kalman filter (UKF) to estimate states and unknown-parameter from augmented nonlinear equation. Performance of estimation results is verified in simulation on an environments of Matlab. The estimation results of the state and unknown-parameter show that the estimation error of unknown-parameter is reduced according to decreasing the state estimation error.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.305-314
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• 2009

The purpose of this paper was to design an effective control system of 1-axis exciter for a seat vibration test of agricultural tractors using MATLAB simulation. The developed simulation model was composed with a hydraulic pump, a hydraulic servo valve, a hydraulic cylinder and load system. Also it was verified by comparing the simulation results with experimental results of actual control system in order to optimize the control performance. And in order to improve its control performance, the designed PID controller in this research was tuned using Ziegler-Nichols 2nd law and zero's moving method of PID controller's transfer function. As the result of these research, the developed position control system was able to control the system's position accurately within 5% errors.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.48-48
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• 2010

소형 공조장치용 냉매 압축기 부품인 기계식 제어 밸브는 에어컨 컴프레서의 핵심부품이고 년간 수백만 개가 국내에 수입된다. 이를 국산화 하기 위하여 진공로 속에서의 브레이징 공정이 수반되는 외국제품의 제조공정을 탈피하여 진공 속에서 DC 프로젝션 용접을 수행하는 기법을 개발하였다. 실린더 형상의 캡과 케이스를 맞대고 그 사이에 박판을 삽입한 상태에서 butt welding 방식으로 진행되는 본 공정에서는, 생산성이 높고 서보가압 장치를 사용하여 soft touch 를 구현하므로 프로젝션이 손상되지 않은 상태에서 통전이 시작되고 2 단 가압 및 프로파일 가압이 가능하므로 링(ring)형상의 너깃이 축대칭으로 안정적으로 형성되기 때문에 실린더 내부의 밀봉성능이 우수함을 확인하였다. 진공로 속에서 본 가압장치를 설치하여 간편한 방법으로 실린더 내부의 진공상태를 유지할 수 있기 때문에 진공로 속에서의 브레이징 공정이 적용되는 외국제품보다 생산성이 월등함을 알 수 있다. 본 연구에서 개발된 링 프로젝션(ring projection) 용접기법은 초소형 및 소형 실린더 형상의 부품 내부를 진공으로 유지해야 하는 산업현장에서 당장 적용될 수 있는 혁신적인 용접공정이라 판단된다.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.79-87
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• 1999

In this study, a new type of flow control valve which is SMA actuated flow control valve is presented. The flow control valve is actuated by a small motion of shape memory alloy. The performance of this valve as a position control component is analyzed by computer simulation. A variable structure control technique is applied for the position control by the flow control valve. The position control performance of the valve is evaluated on the step responses of a PID control by a electrohydraulic servo valve. For the simulation study, first, the mathematical model of a hydraulic system, which is consisted of the flow control valve and a hydraulic cylinder, is formulated. This mathematical model and the designed variable structure control algorithm are then combined by the MATLAB software. The same sequence of work is carried out for the PID position control system with a electrohydraulic servo valve. The simulation results show the validity of the new type of flow control valve as a variable position control component.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.6
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• pp.58-65
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• 1999

The spinning machine has been developed for a bus and truck wheel disc which is manufactured by spinning process method. This machine has the mechanical structure with bed, 2-column, cross head, 2-vertical slide, 2-horizontal slide with forming roller, clamp slide and main spindle similar to large size vertical lathe. Main spindle attached the mandrel is rotated about 500rpm drived by 280kW power DC motor, and a rotating black material pressed on the mandrel with the clamp slide is spinformed by 2-forming rollers which are attached inner end of the 2-horizontal slides. The 2-vertical and 2-horizontal slides are actuated by the hydraulic cylinder which is controlled by the servo valve individially, and these servo valves are controlled by control signal of the CNC controller which is computed with position signal feedbacked from the encoder sensor. The developed machine can manufacture wheel disc of various section profile without mandrel change because section profile is easily modified using program editing in the CNC controller processor. The wheel disc manufactured by spinning process method has many advantages that the endurance is increased by 2 times and the weight is decreased by 30% compared with a conventional disc.