• 대한기계학회논문집
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• 제19권3호
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• pp.868-876
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• 1995

This study deals with a position control of an electro-hydraulic servo system which consist of cylinder and high speed on-off valves operated by microcomputer. The merits of PWM control of hydraulic equipment are the robustness of the high spee on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.463-463
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• 2000

A dual-stage positioner for fast and fine robotic manipulations is presented. By adopting the merits of both coarse and fine actuator, a desirable system having the capacity of large workspace with high resolution of motion is enabled. We have constructed an ultra precision XY positioner with dual-stage mechanism where the PZT driven fine stage is mounted on the motor driven XY positioner and applied it to fine tracking controls and micro-tele operations as a slave manipulator. We describe essential merits of the compound actuation mechanism and some control strategies to successfully utilize it with proper servo system design. Through experimental results, the effectiveness of the coarse/fine manipulation by the dual-stage positioner will be shown.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.529-539
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• 2005

The development of a fast, accurate, and inexpensive position-controlled pneumatic actuator that may be applied to various practical positioning applications with various external loads is described in this paper. A novel modified pulse-width modulation (MPWM) valve pulsing algorithm allows on/off solenoid valves to be used in place of costly servo valves. A comparison between the system response of the standard PWM technique and that of the modified PWM technique shows that the performance of the proposed technique was significantly increased. A state-feedback controller with position, velocity and acceleration feedback was successfully implemented as a continuous controller. A switching algorithm for control parameters using a learning vector quantization neural network (LVQNN) has newly proposed, which classifies the external load of the pneumatic actuator. The effectiveness of this proposed control algorithm with smooth switching control has been demonstrated through experiments with various external loads.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.515-520
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• 2001

Due to the high power to weight ratio and fast response under heavy load, the hydraulic systems are still applied to the development of many industrial facilities such as heavy duty construction vehicles, aerospace/military weapon actuating systems and motion simulators. Unlike the other actuators, single-rod hydraulic cylinder exhibits a lot different dynamic characteristics between the extending and retracting stroke because of the difference in pressure acting areas. In this research, in order to overcome this nonlinear feature, $H_{\infty}$ optimal controller was designed and implemented with DSP board that was specifically developed for the experiment. From the experimental result, we could confirm that the overall performance of single-rod hydraulic servo system is similar with the results as we expected in the design stage.

• 대한기계학회논문집A
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• 제21권8호
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• pp.1229-1240
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• 1997

The purpose of this study is to build up control scheme that promptly control pressure in a hydraulic cylinder having comparatively 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 too large considering the small volume of the hydraulic cylinder and the time delay of response of the PCV is comparatively long. Considering the above-mentioned characteristics of the object pressure control system, in this study, control system is designed with two degree of freedom control scheme that is composed by adding a feed-forward control path to I-PDD$^{2}$ control system, and a reference model is used on the decision of control parameters. And through some experiments on the control system with FF-I-PDD$^{2}$ controller, the validity of this control method has been confirmed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.267-269
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• 1996

Servo systems became indispensable to applications such as industrial robots and numerically controlled machinery. Especially, induction motor drives are widely used as ac-servo system owing to the fact that it is maintenance-free. At the present time, Quick torque control methods such as vector control have been employed that enables an induction motor to attain as quick torque response as a dc motor. However, these methods can not be realized without knowing several motor parameters accurately, because the methods need them to calculate flux or voltage command. Most of all, secondary resistance has to be identified accurately, because it's value varies greatly for operation of induction motors. In this paper, a new identification method of secondary resistance based on quick torque control system of induction motors is proposed. The proposed method is derived theoretically from motor circuit equation and can be realized very simply by detecting primary current and voltage command of the motor. Through the numerical simulation considered using PWM inverter, the validity of the proposed method was successfully confirmed.

• 드라이브 ㆍ 컨트롤
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• 제15권1호
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• pp.16-27
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• 2018

Hydraulic torque load simulator is essential to test and qualify the performance of various angle control systems. Typically a flapper-type second stage servovalve is applied to the load simulator, but here the direct drive servovalve, which is a kind of one-stage valve and affected by the large flow force, is applied. Since the torque load is applied not to the stationary shaft but to the rotating shaft of the angle control system, the controlled torque of load simulator is not accurate due to the rotating speed of the angle control system. A feedforward compensator is designed and applied to minimize the disturbance-like effect. A mathematical model is derived and linearized to analyze the stability, accuracy and responsiveness of the torque load simulator. The parameter effects of a controller, servovalve, hydraulic motor, rotating spring shaft are analyzed and summarized. The goodness of the linear analysis is verified by the digital computer simulations using both the linear and nonlinear mathematical models.

• 산업기술연구
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• 제40권1호
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• pp.19-23
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• 2020

In this paper, we proposed a PC-based CNC control system using EtherCAT-based servo drive and I/O device. The default communication of LinuxCNC is a parallel port, and data processing with high bandwidth is impossible. However, it is possible to apply various bandwidth devices through the application of EtherCAT, one of the industrial Ethernet communications with high bandwidth. Therefore, the hardware control method of LinuxCNC was applied through EtherCAT communication from the existing parallel port. Finally, through HAL configuration, I/O device operation check and 3-axis motion control proved the LinuxCNC system with EtherCAT.

• International Journal of Precision Engineering and Manufacturing
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• 제4권4호
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• pp.13-18
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• 2003

This paper presents the in-process compensation to control cutter ronout and to improve the machined surface quality. Cutter ronout compensation system consists of the micro-positioning servo system with piezoelectric actuator which is embeded in the sliding table to manipulate radial depth of cut in real-time. Cutting force feedback control was proposed in the angle domain based upon repetitive learning control strategy to eliminate chip load variation in end milling process. Micro-positioning control due to adaptive actuation force response improves the machined surface quality by cutter ronout compensation.

• 대한기계학회논문집A
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• 제25권3호
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• pp.478-485
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• 2001

A dynamic load simulator(DLS) which can reproduce on-ground the aerodynamic hinge moment of control surface is an essential rig for the performance and stability test of aircraft actuation system. By setting up load actuator as counter acting with the control surface driving actuator and designing an appropriate force control system for load actuator, DLS can be mechanized. Obtaining an accurate mathematical model for the DLS is the first step to successfully design an aerodynamic load replicati on system. Two theoretical models are presented and tested for their validities with the experimental results, which turns out to be not successful. An alternative way of using system identification approaches in investigated to develop a good nominal model for DLS dynamics, and suitable uncertainty bounds for this nominal model are proposed with the consideration of experimental results.