• 한국기계기술학회지
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• 제13권2호
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• pp.45-54
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• 2011

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. Among the various suspension systems, an active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. In the process of the linearization for the nonlinear active suspension system, the frequency dependent damping method is used for the exact modelling to the real model. The pressure control valve which is controlled by proportional solenoid is the most important component in the active suspension system. The pressure control valve has the dynamic characteristics with 1st order delay. Therefore, It's necessary to adopt the lead compensator to compensate the dynamics of the pressure control valve. The sampling time is also important factor for the control performances. The sampling time value is proposed to satisfy the system performances. After the modelling and simulation for the pressure control valve and vehicle dynamic, the performances of the vehicle ride quality and the stability are enhanced.

• 한국정밀공학회지
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• 제18권7호
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• pp.40-45
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• 2001

This paper proposes a methodology for the small-displacement-movement of a piston and develops a hybrid control algorithm for the precision position control of a pneumatic rodless cylinder. The pneumatic system uses the voltage-proportional solenoid valves to minimum valve switching since the on/off type valves are create diffculties for accurate position control and induce a lot of valve switching. For the accurate position control a methodology for the small-displacement-movement of the piston is developed and identified experimentally. The main consideration on the development of the hybrid control law is to eliminate a stick-slip phenomenon in the pneumatic control system. This paper addresses these critical issues and presents experimental results for the pneumatic control system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.636-639
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• 1996

We have developed a part of hydraulic stroke sensing cylinder using magnetic sensor that can detect each position under severe construction fields. In this paper, for evaluating the developed cylinder under various environment condition, thermal control systems and two hydraulic systems to be coupled consist of. The former is composed of an heater case, temperature sensor, and interface circuits which include SCR(silicon controlled rectifier) for the control of the voltage's phase. The latter is composed of an hydraulic cylinder for position control with solenoid valve (ON/OFF motion) and a load cylinder with proportional reducing valve. To obtain the various performance evaluation, it is carried out under high temperature condition in thermal system controlled by using Ziegler-Nichols PID tuning method and artificial disturbances such as impulse or constant force. The results show that the developed cylinder has good performance under the various environment condition.

• 유공압시스템학회논문집
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• 제4권1호
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• pp.18-24
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• 2007

The continuously variable transmission (CVT) of which speed ratio can change continuously in a fixed range has the benefits of low fuel consumption and exhaust gas because it enables the engine of a vehicle to operate in a high efficiency range regardless of vehicle speed. The speed ratio of belt type CVT is controlled by adjusting line pressure. The one of the line pressure control methods, mechanical-hydraulic control is usually adopting VDT's control method, in which the secondary solenoid valve has two functions both a regulator and a line pressure controller. However, this control method could not show the high performance of CVT with optimal driving capability because of the limitation of simple control algorithm, and it could not gain market share sufficiently in spite of the advantage of CVT with low fuel consumption. On the other hand, the electro-hydraulic control method gives the enhancement of power performance and low fuel consumption by implementing various driving mode using the proportional control or PWM control. The key of CVT technique is to develop a control algorithm of the electro-hydraulic solenoid valve in order to implement the speed ratio efficiently. In this paper, the line pressure control algorithm is proposed and the hydraulic system is controlled using metal belt type CVT test rig and the embedded ECU platform.

• 산업기술연구
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• 제29권B호
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• pp.107-113
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• 2009

For the environmental safety of the operating room and patient healthcare, the closed type rebreathing system is widely adopted. In order to reduce the anesthesia gas during surgery, the mixing ratio of anesthesia gas with breathing air should be precisely controlled. Generally, the breathing air passes through the vaporizer to mix the anesthesia gas, but there is a difficulty in controlling the mixing ratio precisely. In this paper, the stand-alone style vaporizer is designed and the operating characteristics are investigated. The vaporizer measures the temperature and pressure in the vaporizing chamber and chamber temperature is precisely controlled by proportional controlled heater. Exact quantity of anesthesia media is feeded by PID controlled peristaltic pump and vaporized gas is mixed with breathing air flow by PWM controlled solenoid valve. The experimental result shows that the vaporizer has an excellent command following performances that it can be applied to the low flow anesthesia system.

• 드라이브 ㆍ 컨트롤
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• 제10권4호
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• pp.7-13
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• 2013

A tractor is a farm vehicle that is designed to provide a high tractive effort at low speed. It is used for versatile agricultural tasks such as hauling a trailer, tillage, mowing and construction work. As the intensity of work increases, tractors equipped with automatic transmission become popular due to the work convenience. Though manual and power shuttle transmissions are produced by domestic corporations, development for full-automatic power shift transmissions has never been challenged, and so related technology level is quite low. This paper gives a survey of the automatic transmissions from advanced foreign company, which includes layout of gear train, the way hydraulics controls clutches and brakes, electronic control system. The results are expected to be utilized as a basis in the development of original power train design for tractor.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.27-32
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions fur passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed. It is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper which offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-offbecomes smooth when the fixed orifice size increases. Damping forces are measured with the change of the solenoid current at the different piston velocities to confirm the maximum hysteresis of 20N, linearity, and variance of damping farce. The damping farce variance is wide and continuous, and is controlled by the spoof opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• 드라이브 ㆍ 컨트롤
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• 제17권2호
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• pp.55-62
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• 2020

There are two types of IMV for MCV, the spool type and the poppet type. The spool type is used in the existing excavator MCV and easily meets large-capacity flow conditions, but has a flow force problem which affects the spool control. The poppet type stably blocks the flow and has excellent rapid response. However, the larger the capacity, the larger the diameter of the poppet needed, requiring a strong spring to withstand the oil pressure. In this study, a bi-directional three-stage IMV for MCV that can be used in medium and large hydraulic excavators was proposed. This is a poppet type, enabling bi-directional flow control and resolves the problem of proportional solenoid suction force limitation. To investigate the validity of the proposed valve, the system was mathematically modeled and the static and dynamic characteristics were investigated through the simulation using commercial software. It has been concluded that the reverse flow is possible in a regeneration circuit and that the proposed IMV can be used to perform various excavation modes.

• 한국기계가공학회지
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• 제15권3호
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• pp.93-101
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• 2016

This study presents a simple genetic algorithm to systematically design a PID controller for a hydraulic positioning system operated by a proportional solenoid valve. The inverse dead-zone compensator with nonlinear characteristics is used to cancel out the dead-zone phenomenon in the hydraulic system. The object function considering overshoot, settling time, and control input is adopted to search for optimal PID gains. The designed PID controller is compared with the LQG/LTR controller to check the performance of the hydraulic positioning system in the time and frequency domains. The experimental results show that the hydraulic servo system with the proposed PID controller responds effectively to the various types of reference input.

• Journal of Advanced Marine Engineering and Technology
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• 제27권3호
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• pp.412-420
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• 2003

This study describes the merits of PWM control of hydraulic system using high speed on-off valves. Generally, Electro-hydraulic valves can be classified into two classification: valves which are controlled by analog signal and which are controlled by digital. The former includes hydraulic servo valves and proportional valves which require A/D converters as interface to digital computer and too costly and sensitive to oil contamination because of complexity in structures. The latter includes high speed on-off valves which do not require A/D converters because they are normally operated in a pulse width modulation(PWM) method, and are low in price and robust to oil contamination because of their simple structures. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using 2/2way high speed on-off valves and to give a criterion for the stability of this system. The nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are simulated.