• 소음진동
• /
• 제8권4호
• /
• pp.700-705
• /
• 1998

Recent past work has demonstrated that hydraulic semiactive vibration absorbers hold the promise of providing an ideal means of mitigating structural vibration. This paper examines a factor that must be treated when designing a hydraulic semiactive vibration absorber for application to a full scale structure; fluid compressibility. An expanded and consistent dynamic model of the flow process is first established. A simple feedback control is then tested on a single degree of freedom laboratory structure to verify the findings.

• 드라이브 ㆍ 컨트롤
• /
• 제18권4호
• /
• pp.65-71
• /
• 2021

In this paper, the development of a vibration reduction device for hydraulic breakers was studied. Generally, a hydraulic breaker generates shock vibrations while working. When using vibration-proof rubber, shock vibrations are reduced, but without this, shock vibrations are repeatedly generated. Such repeated shock vibrations not only lower the fatigue strength of hydraulic breakers and excavators equipped with them but also increase the fatigue of the workers. This paper proposes the possibility of reducing shock vibration by using a dynamic vibration absorber.

• International Journal of Fluid Machinery and Systems
• /
• 제8권4호
• /
• pp.318-326
• /
• 2015

A valve-less electro-hydraulic servo steering device (short: VSSD) for ships was chosen as a study object, and its mathematic model of hydraulic shock was established on the basis of flow properties and force balance of each component. The influence of system structure parameters, changing rate of motor speed and external load on hydraulic shock strength was simulated by the method of numerical simulation. Experiment was designed to test the hydraulic shock mathematic model of VSSD. Experiment results verified the correctness of the model, and the model provided a correct theoretical method for the calculation and control of hydraulic shock of valve-less electro-hydraulic servo steering device.

• 터널과지하공간
• /
• 제23권6호
• /
• pp.521-537
• /
• 2013

EGS지열발전을 위한 수리자극시 발생되는 미소진동은 투수율 증가의 범위를 파악하는 유용한 수단이 되기도 하지만 지반진동으로 인하여 지상구조물 및 환경에 영향을 미친다. 본 연구는 EGS 지열발전의 수리자극에 의하여 발생하는 미소진동의 안전관리 기준을 수립하기 위하여 지반진동이 건축구조물 및 인체환경에 미치는 영향과 각국의 허용기준을 발파진동을 중심으로 조사 하였다. 또한 유럽과 미국에서 지열발전의 수리자극에 의한 미소진동의 연구사례를 조사 검토하여 포항 EGS 수리자극에 의한 지반진동의 관리 기준에 필요한 자료와 그 대처방안을 제시 하였다.

• International Journal of Fluid Machinery and Systems
• /
• 제4권2호
• /
• pp.289-306
• /
• 2011

In the development of very high head pumped storage projects, one of the critical problems is the strength of pumpturbine runners. Data obtained by stress measurements of high head pump-turbine runners indicated that dynamic stress due to the vibration of runner might be detrimental, possibly to cause fatigue failure, if the runner were designed without proper consideration on its dynamic behaviour. Numerous field stress measurements of runners and model tests conducted with hydrodynamic similarity revealed that the hydraulic excitation force developed by the interference of rotating runner blades with guide vane wakes sometimes would induce such heavy vibration of runner. Theoretical and experimental investigations on both the hydraulic excitation force and the natural frequencies of runner have been conducted to explore this forced vibration problem.

• 드라이브 ㆍ 컨트롤
• /
• 제18권3호
• /
• pp.8-15
• /
• 2021

A rear axle steering (RAS) system is attached to the rear of medium and large commercial vehicles that transport large cargo. The existing RAS systems are driven by electro-hydraulic actuator (EHA), and most commercialized EHAs consist of electric motors, hydraulic pumps, relief valves, prefill valves and cylinders. The prefill valve required for such EHAs is a type of check valve with extremely low cracking pressure that should not allow RAS to have noise or vibration, and the prefill valve prevents system negative pressure as well as unstable operation. Most papers on this topic rely on experiments to predict valve performance, and theoretically detailed modeling of valves or pipelines is performed, but it is very rare to evaluate hydraulic vibration characteristics by analysing everything from hydraulic pumps to valves comprehensively. In this study, we proposed an experimental circuit that can predict the performance of the prefill valve. The study also analysed the pressure-flow pulsation that is transmitted to the valve through the pipeline, and how the transmitted pressure-flow pulsation affects the valve vibration.

• 한국소음진동공학회논문집
• /
• 제14권10호
• /
• pp.1021-1028
• /
• 2004

Developed friction snubbers changes the shock or vibration into a heat energy by mechanical friction. Snubber is divided into friction snubbers and hydraulic snubbers according to the operation types. However, hydraulic snubber has a lot of problems caused by temperature, humidity, radioactivity, and viscosity of hydraulic fluid. In these respects, to solve these problems, not only do friction snubber supplement lacks of hydraulic snubber but has also simpler structure than hydraulic snubber. In this paper, friction snubber used sponge iron by friction material is experimentally compared with general friction snubber In this results, the experiment verifies friction function and produce the manufacture condition for the effective friction snubber development.

• 대한기계학회논문집A
• /
• 제30권1호
• /
• pp.52-59
• /
• 2006

The vibration of hydraulic piston pumps is induced by the periodically changing cylinder chamber pressure whose waveform is significantly influenced by valve plate geometry. In this study, the force input to the housing of a bent-axis type hydraulic piston pump was computed by deriving the dynamic equations of its piston and cylinder barrel. The vibration intensity of the pump was represented by the acceleration amplitude of its housing. In order to comparatively evaluate the influence of valve plate geometry on the vibration of pump housing, two different types of valve plate were tested. The computed results showed good agreement with the experimental data, indicating that the vibration acceleration of pump housing is rather dependent on the variation amplitude of balance coefficient than the changing slope or overshoot of cylinder chamber pressure. It was also confirmed that the design effect of valve plates could be directly examined out by monitoring the vibration acceleration of pump housing.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 춘계학술대회 논문집
• /
• pp.273-277
• /
• 1995

Many hudraulic components have nonlinearities to some extent. These nonlinearities often cause the time delay, thus degrading the performance of the hydraulic control systems and making it difficult to modelthem. In this paper, a new vibration isolation control algorithm that eliminates the necessity of a sophiscated modeling of hydraulic system was proposed. The algotithm is a hybrid type control shecheme consisting of a linear controller and a hetero-synaptic neural network controller. Using this control scheme, simulations and experiments were performed for 1 DOF(Degree of freedom) and 2 DOF vibration isolation. The hybrid type control algorithm can isolate the base vibration signifcantly rather than linear control algorithm. And from the weights in hetero-synaptic neural network, we can get the 2nd equivalent differentialmodel of the hydraulic control system with on-line control operation. This equivalent model provides us with much information, such as stability and the characteristics of the control system.

• 한국정밀공학회지
• /
• 제27권12호
• /
• pp.33-40
• /
• 2010

Vibration of a hydraulic excavator's body and boom occurs when the boom quickly stops after upward or downward motion. The main objective of this research is to present an idea of suppressing the vibration. Three parameters which affect the vibration are defined and analyzed thoroughly and a heuristic method suppressing the vibration is presented in this paper. Experimental results show that the proposed method works very well.