• 한국정밀공학회지
• /
• 제9권3호
• /
• pp.29-41
• /
• 1992

According to the recent increase of demands for multi-function and economics on hydraulic excavator, it is required that excavator should have simple operation, higher and operational efficiency, however the modeling of engine/pump system of excavator is not prescribed by the paper. So, in this paper the modeling of engine/pump system of excavator is suggested by identification method from step response and verified effectiveness of identification system by comparing with experimental results which was conducted using PID controller. To improve the problem of parameter variation and modeling error in the system, sliding mode control was introduced and new switching surface was designed. This control algorithm was applied to a hydraulic excavator by simulation, and its effectiveness was verified, and the results of variable structure system for the excavator system using a output component was compared with that of full state feedback when load disturbances and system paramenter variation exist.

• 동력기계공학회지
• /
• 제15권2호
• /
• pp.69-77
• /
• 2011

In this paper, an optimal PID sliding mode controller is proposed for the position control of electro-hydrostatic actuator(ERA) systems with system uncertainties and saturation in the motor. An ERA prototype is developed and system modeling and parameter identification are executed. Then, optimal PID and optimal anti-windup PID controller are designed based on identified system model by using optimization toolbox in MA TLAB/Simulink and the performance of the two control systems are compared by experiment. It was found that the optimal anti-windup PID control system has better performance than the optimal anti-windup PID control system.

• 한국정밀공학회지
• /
• 제15권1호
• /
• pp.87-93
• /
• 1998

Pressure ripples of hydraulic vane pump results from flow ripples due to pump geometry and reverse flow through the discharge port due to compressibility of fluid and result in vibration and noise of connected hydraulic elements. In a balanced type vane pump, cam ring curve is important factor to influence the flow ripples. Therefore, to reduce the flow ripple, it has been required that optimal selection of seal region by proper design of cam ring and each port position, and notches for preventing the excessive reverse flow. This paper has been performed analytical study of compression characteristics with major design parameter in side plate and cam ring. and examined into the role of notch and radius reduction ratio.

• Tribology and Lubricants
• /
• 제15권1호
• /
• pp.17-23
• /
• 1999

A Gerotor hydraulic motor is a planar mechanism consisting of a pair of rotors one of which encloses another rotor. The motion of the inner-rotor relative to the outer-rotor is produced by the pressure difference between the adjacent chambers. A design method of inner-rotor tooth profile using unit tangential vectors is presented in this work. Based on the relationships derived, the influence of the eccentricity of inner-rotor and the radius of circular arc tooth on the flow rate, torque and curvatures were investigated. It was shown that the flow rate and mean torque is proportional to eccentricity, but inversely proportional to the radius of circular arc teeth. Also, the maximum value of the equivalent curvature is increased as the eccentricity and the radius of circular arc teeth increased.

• Journal of Advanced Marine Engineering and Technology
• /
• 제27권3호
• /
• pp.388-394
• /
• 2003

Hydraulic system is difficult to obtain a suitable performance due to the nonlinearity load pressure change and system parameter variation. The requirement of control a1gorithm has been complex in order to satisfy the performance. The adaptive control is a control method which is suggested to achieve the control object under the plant characteristics change. In spite of the case that plant characteristics and the degree of variation are difficult to grasp. the adaptive control could keep the characteristics of closed-loop system generally. In this study. a method of combined generalized minimum variance adaptive control (GMVAC) and output error feedback is proposed, in order to solve the problem of non-minimum phase of plant and the vibration and overshoot in initial response. The control performance according to the variation of characteristics of plant is evaluated by changing the supply pressure. The experimental results show the effectiveness of the proposed scheme.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 B
• /
• pp.598-600
• /
• 1998

In this paper, a robust controller is proposed to achieve the accurate tracking for uncertain robot manipulators with hydraulic actuator dynamics. The parameter uncertainty can be quantified by the linear parameterization technique. A switching controller is proposed to guarantee the global asymptotic stability of the plant. In order to eliminate the chattering caused by the switching controller, a smoothing controller is proposed using the boundary layer technique around the sliding surface. It is shown that the smoothing controller guarantees the uniform ultimate boundedness of the tracking, error. The proposed controller shows good better tracking performance.

• Structural Engineering and Mechanics
• /
• 제53권2호
• /
• pp.297-309
• /
• 2015

The purpose of this work is to analyze the effect of structure parameter disturbance on the dynamic characteristics of a hydropower station powerhouse. A vibration model with a head-cover system is established, and then the general disturbance problem analysis methods are discussed. Two new formulae based on two types of disturbances are developed from existing methods. The correctness and feasibility of these two formulae are validated by analyzing the hydropower station powerhouse vibration model. The appropriate calculation method for disturbance of the hydropower station powerhouse vibration dynamic characteristics is derived.

• 산업경영시스템학회지
• /
• 제36권3호
• /
• pp.1-7
• /
• 2013

This paper is a case study of reliability assessment with field warranty data of Clutch Master Cylinder (CMC) in hydraulic clutch system. We estimate lifetime distribution using field warranty data which contain much useful information for understanding reliability of the system in the real-world environments. However, the estimated parameters are far from existing reference values, which seems to be caused right censored field warranty data. To modify the parameters, we use the information of the durability test which is performed to verify that the lifetime of the item meets the required level. After that, we can observe that the modified parameters are closer to the existing reference values. This case study shows a possible idea to supplement lack of right censored field warranty data and its applicability.

• 물과 미래
• /
• 제29권1호
• /
• pp.129-139
• /
• 1996

수공구조물의 계획과 설계에 있어서 수문자료에 대한 적정분포형을 선정하는 것은 매우 중요하며, 선정된 분포함수가 실측자료의 통계학적 특성을 잘 나타내고 있는가를 검토하는 것은 필수적인 과제이다. 본 연구에서는 전국 22개 지점, 7개 지속기간의 강우자료에 대하여 2변수 및 3변수 gamma, 2변수 및 3변수 lognormal, Gumbel, 2변수 및 3변수 log-Gumbel, GEV, log-Pearson type III, 2변수 및 3변수 Weibull, 4변수 및 5변수 Wakeby 분포를 적용하여 모멘트법, 확률가중 모멘트법, 최우도법 등으로 각 분포형의 매개변수를 추정하고, 적합성 조건을 검사하였다. 각 매개변수 추정법에 의하여 추정된 매개변수를 이용하여 10,000번 모의 발생하여 분리효과를 검토한 결과 매개변수 적합성을 고려한 경우 모멘트법에서는 log-Pearson type III 분포, 확률가중 모멘트법에서는 log-Pearson type III와 GEV 분포, 최우도법에서는 GEV 분포가 분리효과를 가장 작게 나타냈으며, 2변수 분포형의 경우 모두 분리효과가 크게 나타났다.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제22권3호
• /
• pp.27-41
• /
• 2017

This study dealt with the characteristics and the interrelations of hydrogeological parameters such as hydraulic conductivity, dispersivity and effective porosity of unconsolidated sediments for providing the basic data necessary for the planning of the management and preservation of groundwater quality in the Nakdong River Delta of Busan City, Korea. Groundwater quality in this area has been deteriorated due to seawater intrusion, agricultural fertilizer and pesticide, industrial wastewater, and contaminated river water. The physical properties (grain size distribution, sediment type, sorting) and aquifer parameters (hydraulic conductivity, effective porosity, longitudinal dispersivity) were determined from grain size analysis, laboratory permeability test and column tracer test. Among 36 samples, there were 18 Sand (S), 7 Gravelly Sand (gS), 5 Silty Sand (zS), 5 Muddy Sand (mS), and 1 Sandy Silt (sZ). Hydraulic conductivity was determined through a falling head test, and ranged from $9.2{\times}10^{-5}$ to $2.9{\times}10^{-2}cm/sec$ (0.08 to 25.6 m/day). From breakthrough curves, dispersivity was calculated to be 0.35~3.92 cm. Also, effective porosity and average linear velocity were obtained through the column tracer test, and their values were 0.04~0.46 and 1.06E-04~6.49E-02 cm/sec, respectively. Statistical methods were used to understand the interrelations among aquifer parameters of hydraulic conductivity, effective porosity and dispersivity. The relation between dispersivity and hydraulic conductivity or effective porosity considered the sample length, because dispersivity was affected by experimental scale. The relations between dispersivity and hydraulic conductivity or effective porosity were all in inverse proportion for all long and short samples. The reason was because dispersivity was in inverse proportion to the groundwater velocity in case of steady hydrodynamic dispersion coefficient, and groundwater velocity was in proportion to the hydraulic conductivity or effective porosity. This study also elucidated that longitudinal dispersivity was dependent on the scale of column tracer test, and all hydrogeological parameters were low to high values due to the sand quantity of sediments. It is expected that the hydrogeological parameter data of sediments will be very useful for the planning of groundwater management and preservation in the Nakdong River Delta of Busan City, Korea.