The main hydraulic pump is a device that generates the hydraulic pressure needed for the K2 tank. It is a pressure-compensated swash plate piston pump that generates the hydraulic power necessary to drive the hydraulic device. Hydraulic pump design changes were made due to frequent failures of the hydraulic pump. As a result of checking the operation records of the hydraulic pump, about 71% of the total engine operation time was in a stationary state where hydraulic pressure was not needed. This has the problem of constantly running when the engine is started, consuming unnecessary endurance time, and generating high noise. In this study, ISG(Idle Stop & Go) was applied to improve operation method. When applying ISG, the pressure can be reduced to about 85% or less in an environment where the operation of the main hydraulic pump is not necessary. So, the lifespan of the main hydraulic pump increases as a result of ISG application, thereby reducing the waste of national funds due to maintenance costs. Also, it is expected to contribute to improving combat power by reducing crew fatigue due to noise reduction.

This paper develops a flow control block for a hydraulic system of a tunnel boring machine. The flow control block is a necessary component to ensure stability in the operation of the hydraulic system. In order to know the pressure distribution of the flow control block, the flow analysis was performed using the ANSYS-CFX. It was confirmed that the pressure and flow rate were normally supplied to the hydraulic system even if one of the four ports of the flow control block was not operated. In order to evaluate the structural stability of the flow control block, structural analysis was performed using the ANSYS WORKBENCH. As a result, the safety factor of the flow control block is 1.54 and the structural stability is secured.

In this paper, the design of hydraulic system for leveling control of a large vehicle was developed. The hydraulic system for leveling control was consisted of four hydraulic actuators and two gravity referenced inclinometer. In order to verify the effectiveness of leveling system via simulation, Hydraulic actuators, vehicle and control algorithm were modeled using ADAMS which is a commercial dynamic analysis software for multi-body system. The test and simulation results of hydraulic actuator were compared and it showed the properness of simulation model. The effectiveness of hydraulic system and leveling control algorithm were verified via simulation results.

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.

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

Experimental analysis has been carried out to investigate oil temperature control characteristics of the hydraulic system in a special vehicle. Hydraulic system performance is largely affected by oil temperature, and there are considerable malfunctions in the system for high temperature conditions caused by heavy load and continuous operation. Oil pressure in the hydraulic system decreases with oil temperature, and its variation rate becomes less steep as oil temperature increases. There is severe time delay for oil temperature control due to the operation of heat exchanger system, and it depends on the oil flow rate and pressure in the system. These results in this study can be applied to the design of automatic thermal control system in the special vehicle hydraulic system.

Experimental analysis has been carried out to investigate thermal characteristics of hydraulic system in special vehicles. Hydraulic system performance is largely influenced by oil temperature, and there are considerable performance decline and malfunctions in the system for high temperature conditions caused by heavy load and continuous operation. Transient oil temperature and pressure variation are analyzed and heat generation rates in the several main system parts are compared for various flow rates. With the start of system operation oil temperature gradually increases, and viscosity deceases by about 70% as temperature increases from 20℃ to 80℃. Operation pressure in the hydraulic system decreases with oil temperature, and its variation rate becomes less steep as oil temperature increases. Heat generation rate in hydraulic pump also depends on the oil temperature, and it reaches maximum near 50℃. These results in this study can be applied to optimal design of efficient hydraulic system in special vehicles.

케이블 구조시스템의 경우 자기 평형 상태를 유지하기 때문에 장력이 손실된 특정 케이블을 재긴장을 하지 않으면 구조엔지니어가 요구한 하중보다 더 큰 하중이 다른 케이블에 전달되어 손상을 야기 할 수 있다. 또한, 턴버클을 이용한 재긴장 방법이 기존에 널리 적용되고 있지만 정확한 장력조절과 대구경 케이블에는 적절하지 못하고 인장재의 하중의 크기를 측정하는 것이 어렵다. 따라서 효과적으로 재긴장 할 수 있는 유압식 볼팅 접합부를 개발하고 인장력을 실시간으로 확인할 수 있는 모니터링 시스템을 적용하였다. 본 논문에서는 개발된 시스템의 현장 적용성 실험과 결과를 제시하였다.

This study describes a hydraulic fluid property compensator under the various operating conditions. Because hydraulic fluid systems have much more excellent features than other control systems, they are used in many fields. However, the characteristics of hydraulic fluid are changed due to various operating conditions. This phenomenon is called uncertainty. Especially, bulk modulus is considered as the most dominant parameter in this study. In order to overcome the uncertainty ∞ control technique will be used for this study. Designed controller using the ∞ control technique, is adopted for the hydraulic fluid multistage double acting oil pressure cylinder. Repetition operation test gives from 5 to 8 percent errors in moving position.

멸치초망용 챗대의 유압 권양장치를 개발하기 위하여 모형 챗대와 그물을 실물의 1/5크기로 제작하여 챗대를 권양할 때의 장력을 측정하고, 이를 토대로 권양기 3종을 설계 제작하여 그 성능을 시험한 결과를 요약하면 다음과 같다. 1. 챗대를 건양하는데 가장 큰 장력이 작용할 때는 챗대 끝이 수면 하 4m에 있을 때이었고, 이 때 챗대줄에 작용하는 장력은 187.5kgf이었다. 2. 멸치초망 어업에 적합한 권양기의 조건은 어탐중 챗대가 움직이지 않아야 하며, 그 방법으로 감속기나 전자브레이크를 장치하는 것보다 시간 경과에 따른 누수량이 적은 것을 사용하는 것이 바람직하였다. 3. 시험에 사용된 권양기 중 최적의 권양기에 있어서 압력차 δP를 130kgf/ cm2으로 고정하였을 때, 권양기에 감겨지는 챗대줄의 권양속도는 2m/sec로서 재래식 방법보다 0.48m/sec 빠르게 나타났으며, 양망당 약 1.6톤의 멸치를 어획할 수 있다. 4. 권양기 2대를 설치함으로써 조업인원 2명을 절감할 수 있었다.

Our status of off-shore stow-net fishery is in face with many difficult problems; the lack of fisherman by evading the 3-D occupation, the safety accident by unskilled crew and old type fishing system. In order to solve those problems, it is necessary to save the man power and ensure the safety of fishing work by the effective utilization of power and automatization of fishing gear system. This is consists of the side drum driven by main engine, the net hauler, the bow and stern capstan, jib crane etc. Therefore, we suggest the design on unification of power device of fishing gear system as follows; (1) fishing system by uni-hydraulic power and (2) fishing system by electric motor and electro-hydraulic power.

Counter balance valve is used as one part of hydraulic motor brake system. The function of this valve is to protect over-run or free falling of inertia load. But occasionally the brake system with counter balance valve makes some undesirable problems such as pressure surges or vibrations. These problems may hurt system safety and driver's conformability. Nevertheless, studies on dynamic characteristics of hydraulic system including counter balance valve are very rare, so further accumulation of research results are required. In this study, for the purpose of easy estimation about dynamic characteristics of hydraulic system including counter balance valve, precise formulation describing fluid dynamics and valve dynamics under various boundary conditions were made. The equations obtained in the preceding process include some parameters that must be got experimentally. Flow coefficients of valve and choke are the most significant ones among the parameters. So these parameters are obtained experimentally in this study, and experimental equations obtained from the experimental data were used for numerical calculation. The equations were analysed by numerical integration using Runge-Kutta method, because the equations contain various nonlinear terms. From the numerical analysis, it was verified that the dynamic response of counter balance valve and pressure variation at each elements can be estimated very easily. So the analysing method developed in this study enabled very easy estimating the relation between the performances of counter balance valve and various physical parameters related to the valve. Conclusively, it is said that the results obtained in this study can be used very usefully to develop a new type counter balance valve or to apply the valve to actual hydraulic system for various industrial equipments.

The backdrivable servovalve is a desirable component for force and interaction control of hydraulic actuation systems because it provides direct force generation mechanical impedance reduction by its own inherent backdrivability. However, high parametric uncertainty and friction effects inside the hydraulic actuation system significantly degrade its advantage. To solve this problem, this letter presents a disturbance-adaptive robust internal-loop compensator (DA-RIC) to generate ideal interactive control performance from the backdrivable-servovalve-based system. The proposed control combines a robust internal-loop compensator structure (RIC) with an explicit disturbance estimator designed for asymptotic disturbance tracking, such that the controlled system provide stable and ideal dynamic behavior for impedance control, while completely compensating the disturbance effects. With the aid of a backdrivable servovalve, we show that the proposed control structure can be implemented based on a simplified nominal model, and the controller enables implementation without accurate knowledge of the target system parameters and disturbances. The performance and properties of the proposed controller are verified by simulation and experiments.

For dismantling heavy structure under special environment in radioactivity, there are many problems which should be tele-operated and feedback a cutting force for cutting a thick structure such as concrete. When operator dismantles a thick heavy concrete structure, it is in sufficient to judge whether robot is contacting or not with environment by using only vision information. To overcome this problem, force feedback and impedance model based bilateral control are introduced. The sliding mode control with sliding perturbation observer (SMCSPO) based bilateral control is applied and surveyed to a single rod hydraulic cylinder in this paper. The sliding mode control is used for robustness against a disturbance. The sliding perturbation observer is used for estimation of a reaction force such as cutting force. The bilateral control is executed using the information of reaction force estimated by SMCSPO. The contribution of this paper is that the estimation method and bilateral control of the single rod hydraulic cylinder are introduced and discussed by experiment.

In order to achieve a force controller with high performance, an accurate torque servo is required. However, the precise torque servo for a double vane rotary actuator system has not been developed till now, due to many nonlinear characteristics and system parameter variations. In this paper, the torque servo structure for the double vane rotary actuator system is proposed based on the torque model. Nonlinear equations are set up using dynamics of the double vane rotary hydraulic actuator system. Then, to derive the torque model, the nonlinear equations are linearized using a taylor series expansion. Both effectiveness and performance of the design of torque servo are verified by torque servo experiments and applying the suggested torque model to an impedance controller.