• 한국정밀공학회지
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• 제15권1호
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• pp.109-116
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• 1998

This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone (MPWMD). The pneumatic system using on-off valves has advantage of simple construction and low cost compared with a system with servo-valves. The performance of the proposed control method is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control compared to the conventional PWMD algorithm. It is also shown that the use of the proposed MPWMD algorithm for the position control significantly reduces the number of valve switching and noise.

• 한국정밀공학회지
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• 제13권6호
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• pp.102-113
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• 1996

An experimental and theoretical study on a pneumatic servo system has been conducted using on-off valves and a pneumatic cylinder. A V/I converter has been designed for rapid rising and falling of the solenoid current, which significantly improves the positioning accuracy and settling time of the servo system by shortening the valve opening time. Pulse width modulation was modified to operate on-off valves effectively. A state feedback controller which feeds back position, velocity and acceleration is used to control the system. The influence of controller gains on the system performance is studied to develop a scheme that automatically adjusts the gains using fuzzy logic theory. It is shown experimentally that the proposed fuzzy logic tuner works satisfactorily. A new method for measurements of valve effective areas is proposed, and a partially polytropic model is applied to simulation of the pneumatic system. Simulated results show good agreement with experimental data.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1619-1625
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• 1997

This paper concerns a 2-axis PR type pneumatic manipulator system translating in vertical and rotating in horizontal directions. A simplified linear model is mathematically formulated similar to the pneumatic acturators in dynamic responses in order to devise an appropriate position control scheme. A PD controller preceding the on/off solenoid valve turns out not only economical but also effective in reducing rise time and amplitude of limit cycles, if its control gains are determined on the basis of frequency response. And, additional implementation of symmetric or asymmetric deadband at the PD controller output greatly helps minimize valve opening numbers, positional error, and undesirable direction-dependent property due to the gravitational load. Such a control concept is synthesized through numerical simulations and next applied to the experimental set-up, featuring enhanced positional servo characteristics.

• 제어로봇시스템학회논문지
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• 제9권3호
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• pp.196-203
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• 2003

Recent increase in accessibility to the internet makes it easy to use the internet-connected devices. The internet could allow any user can reach and command any device that is connected to the network. But these teleoperation systems using the internet connected device have several problems such as the network time delay, data loss and development cost of an application for the communication with each other. One feasible solution is to use local and external network line for the network time delay, transmission control protocol for data loss and Java language to reduce the development period and cost. In this study, web-based remote control system using Java language is newly proposed and implemented to a pneumatic servo control system to solve the time delay, data loss and development cost. We have conducted several experiments using pneumatic rodless cylinder through the internet and verified that the proposed remote control system was very effective.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.820-825
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• 1996

This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone. The pneumatic system using on-off valves studied in this paper has advantage of simple construction and low cost compared with a system with servo-valves. The performance of proposed control system is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control and to prevent on-off valves from unnecessary switching.

• Journal of Welding and Joining
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• 제22권4호
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• pp.43-49
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• 2004

Conventional method for electrode force application in resistance spot welding(RSW) processes is to use pneumatic cylinder. However, due to its inherent problems in pneumatic power system such as compressibility of air and poor transient response characteristics, new electrode force system with servo control are recently introduced in RSW machine. This machine is called “servogun”. The purpose of this study is to evaluate performance of servogun in case of spot welding of aluminum alloy. Aluminum alloy(A5052) sheets are spot welded using pneumatic gun and servogun. Both results are compared by means of macro cross-section etching test and tensile shear strength test. Numerous previous research have reported nugget with many voids and cracks are not uncommon defects in spot welds with aluminum alloy. The experimental results show similar defects in case of pneumatic gun. In contrast, use of servogun considerably reduced generation of voids and cracks. In case of step-wise increased forging force at the end of welding cycle with servogun, crack-free and void-free nuggets have been observed. The performance of servogun has been also verified by series of tensile shear test. Higher strength values have been achieved with servogun in comparison to that of pneumatic gun.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1215-1220
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• 2008

The aim of this paper is to perform a finite element analysis that will have the ability to predict the seal performance characteristics, such as deformation, contact load and friction and also is to provide a means of potential seal designs, which can reduce the time and cost of designing the performance of the seal. The material property tests of elastomer seal are performed to obtain the hyperelastic properties and The Mooney-Rivlin constants are determined from these test results. A 2D modelling of the seal cross section is performed to simulate the contact behavior between the seal on the piston and the cylinder bore under operation conditions. The deformation behavior, contact load and friction of an elastomer seal is analyzed by a finite element method which performs three analytic phases of interference fit, the variations of pneumatic pressure and piston movement under the operational conditions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1012-1017
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• 2003

The development of a fast, accurate, and inexpensive position-controlled pneumatic actuator that may be applied to a variety of practical positioning applications with various external loads is described in this paper. A novel modified pulso 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 standard PWM technique and that of the novel modified PWM technique shows that the control performance is significantly increased. A state feedback controller with position, velocity and acceleration feedback is successfully implemented as the continuous controller. Switching algorithm of control parameter using learning vector quantization neural network (LVQNN) is newly proposed. which estimates the external loads of the pneumatic actuator. The effectiveness of the proposed control algorithms are demonstrated through experiments with various loads.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.160-170
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• 2006

If hydraulic pump controlled by mechanical type regulator has more than one control function, the construction of regulator will be very complicated and control performance falls drastically. It is difficult to have more than one control function for hydraulic pump controlled by electronic type hydraulic valve due to the inconsistency of controllers. This paper proposes a multi-function control technique which controls continuously flow, pressure and power by using EPPR(Electronic Proportional Pressure Reducing) valve in swash plate type axial piston pump. Nonlinear mathematical model is developed from the continuity equation for the pressurized control volume and the torque balance for the swash plate motion. To simplify the model we make the linear state equation by differentiating the nonlinear model. A reaction spring is installed in servo cylinder to secure the stability of the control system. We analyze the stability and disturbance by using the state variable model. Finally, we review the control performances of flow, pressure and power by tests using PID controller.