Oil Hydraulic Circuits Research Articles

Flow Loss of Pipe Fittings Used in Oil-Hydraulic Circuits

Flow Loss of Pipe Fittings Used in Oil-Hydraulic Circuits

A Mathematical Model of a Bladder-type Accumulator Considering Heat Conduction

Accumulator is an important component for oil-hydraulic circuits. It is used for storing energy, absorbing pulsation flow, and suppressing surge pressure. For predicting accumulator performance, mathematical models of the accumulator have been investigated by many researchers. In the mathematical models of accumulator, an equation of state of gas, thermodynamics, and heat transfer have been considered. The aim of this paper is to propose a mathematical model of bladder-type accumulator considering heat conduction effect inside rubber membrane. Experiments were carried out using a bladder-type accumulator which was connected to a piston-type accumulator. The bladder-type accumulator was prefilled first and then discharged, the piston-type accumulator was charged by the oil discharged from the bladder-type accumulator. Discharging process of the bladder-type accumulator and charging process of the piston-type accumulator were measured simultaneously. The accumulator model proposed was validated by measured date of the experiments.

Using a Kalman Filter to Estimate Unsteady Flow

A Kalman filter that estimates incompressible unsteady flow in a pipe is proposed in this paper. It is a steady-state Kalman filter based on amodel of pipeline dynamics, that is, an optimized finite element model developed by the author. Pressure signals at both ends of a target section of a pipe are input to the model of pipeline dynamics, and, as an output of the model, an estimated pressure signal at a mid-point in the pipe is obtained. The deviation between a measured and an estimated pressure signal at the mid-point is fed back to the dynamic model of the pipeline to modify state variables of the model, which are pressure and flow rate along the pipe. According to the Kalman filter principle, the state variables of the model are modified as to converge to real values. The Kalman filter is examined by experiment using an oil-hydraulic circuit. The unsteady flow and unsteady pressure of a delivery port of an oil-hydraulic pump are estimated by the Kalman filter. The performance of the Kalman filter is demonstrated, and its bandwidth is discussed.

전기 유압식 동력 조향시스템의 모델링 및 시뮬레이션에 관한 연구

EHPS는 탈엔진형 조향기술로 BLDC 모터를 통해 유압펌프를 작동시켜 조향력을 보조하는 동력 조향장치이다. EHPS는 BLDC 모터, 기어펌프 및 유압회로, 파워 스티어링 등으로 이루어진 전기전자, 유압 및 기계시스템의 복합적 시스템으로 모델링이 어렵다. 본 논문에서는 EHPS 시스템의 구성 부품을 수학적 모델링 하였고, AMESim을 이용하여 multi-domain 시스템의 시뮬레이션 모델을 구축하였다. 이를 활용한 다양한 시뮬레이션을 통해 개발 초기단계에서의 시행착오를 줄이고 완성도 높은 EHPS 개발 업무를 수행하는 데 도움을 줄 수 있을 것으로 사료된다. Electro-hydraulic power steering (EHPS) system is the power-assisted steering which operates the hydraulic pump by BLDC motors for assisting the steering force. EHPS consists of BLDC motor, gear pump, oil-hydraulic circuit and steering system. Since EHPS is a convergence system consisting of electricity and electronic, hydraulic and mechanical system, it is difficult to establish the simulation model. In this paper, the mathematical model of EHPS system components were presented, and the simulations of the multi-domain system were performed by using AMESim. The trial and error of development would be reduced by using this simulation results, and it would be helpful for developing high-quality EHPS.

油圧回路設計・動特性解析用シミュレーション・パッケージの基本機能と基本構造

油圧回路設計・動特性解析用シミュレーション・パッケージの基本機能と基本構造

油圧回路設計・動特性解析用シミュレーション・パッケージOHC-Simの改良

油圧回路設計・動特性解析用シミュレーション・パッケージOHC-Simの改良

210 ウインチ巻き下げ時のカウンタバランス弁の安定性に関する研究

In the oil-hydraulic circuit for the winch such as crane, the counter balance valve is used for putting a brake on the actuator. However, the oil-hydraulic circuit including the counter balance valve is instable, it is generally known to cause the oscillatory phenomenon easily. To provide stabilization of the counter balance valve, the damping of it is more effective in practice, however, it makes the response of the counter balance valve worse. Therefore the stability of the counter balance valve is developed on this study. At first, analysis model of the oil-hydraulic circuit for the winch including the counter balance valve is made and analysis result and experiment result are compared. Next, the stability of the counter balance valve is developed when the pattern of the variability orifice or annular clearance orifice of the counter balance valve is changed. In the consequence, it is approved that optimization of the damping of the counter balance valve provides stability and responsiveness of counter balance valve on a higher level.

FUNCTIONS, FUNCTIONING AND OPTIMIZED POSITIONING OF PRESSURE CONTROL VALVES IN OIL-HYDRAULIC CIRCUITS

The pressure control valves can perform different functions in the hydraulic systems, such as: establish maximum pressure, reduce pressure in some circuit lines, and establish sequence movements, among other functions. The main operation of these valves consists of providing a balance between pressure and the force load on a spring. Most of these valves can be positioned in many different levels, between totally open and totally closed, depending on the flow and on the pressure differential. The pressure control valves are usually named according to their primary functions, e.g., lock wire valve, sequence valve, safety valve, etc. and, their basic function is limit or to determine the pressure of the hydraulic system for the attainment of a certain function of the equipment in motion. They are also classified by the type of connections, by the size and by the selected pressure band. Instead of relief and security, discharge, counterbalance, sequence, reducing and shock suppressor valves represent the pressure control devices. In this paper, oil-hydraulic circuits are suggested for practical lessons of Hydraulic and Pneumatic Commands where they regulate valves of pressure, by acting in the following situations: limiting the maximum pressure of the system, determining a level of pressure, determining two different levels of pressure, determining at the same time two distinct levels of pressure, unloading the pump. The functions of these devices will be discussed and analyzed as an attempt to improve their position in the circuit.

Simulation of the Dynamic Characteristics of a Pneumatic Circuit by OHC-Sim

OHC-Sim is a simulation package for design of an oil-hydraulic circuit and analysis of its dynamic characteristics. To make the design and the improvement processes of an oil-hydraulic circuit more effective and systematic, OHC-Sim had been developed with the support of JFPS and has been enhanced in the research committee in JFPS. OHC-Sim is executable on personal computers in Windows® environment, and provides easy design and improvement of an oil-hydraulic circuit based on the simulated results. However, in order to enhance the use of OHC-Sim, it is desirable that the simulation of the dynamic characteristics of a pneumatic circuit becomes executable on OHC-Sim. In this study, to enhance OHC-Sim to the simulation of a pneumatic circuit, the bond-graph models for pneumatic components are discussed. And, by using the user-customized function, these bond-graph models are registered to OHC-Sim, and the simulation of dynamic characteristics of a pneumatic circuit is carried out.

F-1338 OHC-Simによる水圧駆動システムの動特性のシミュレーション(J29-3 知能ロボット)(J29 センサ・アクチュエータシステムとその知能化 : 実環境で活躍するメカトロニクスをめざして)

The development of the water hydraulic drive system is expected to solve the environmental problem. This paper deals with the dynamic characteristics of the water hydraulic drive system using tap water as a operating liquid, whose research and development is required from the view point of the environmental assessment and resources saving. The system using in the experiment is similar to a typical oil-hydraulic circuit consisting of a vortex pump, a relief valve, an electro-magnetic type on-off valve and a single rod cylinder. The step responses of pressure, piston displacement and load force in the operation condition of a low pressure as a tap water are obtained. And the dynamic characteristic was analyzed by a simulation program "OHC-Sim"

125 低圧における水圧駆動システムの動特性

This paper deals with the dynamic characteristics of the water hydraulic drive system using tap water as a operating liquid, whose research and development is required from the view point of the environmental assessment and resources saving. The system using in the experiment is similar to a typical oil-hydraulic circuit consisting of a vortex pump, a relief valve, an electro-magnetic type on-off valve and a single rod cylinder. The step responses of pressure, piston displacement and load force in the operation condition of a low pressure as a tap water are obtained experimentally and the fundamental characteristics of a water hydraulic drive system are discussed

Minimax Design with Consideration of Uncertain Variation of Design Variables. 1st Report. Multiobjective Optimization using Fuzzy Decision.

This paper presents a new design method for systems which have uncertain variation in their design variables. We convert the design problem of above systems to a multiobjective optimization problem which improves a nominal performance and a difference between the nominal performance and the worst one. A minimax problem between a system designer and the variation of the design variables is solved with a new iterative method to get the worst performance. As a numerical example, we investigate a design problem which improves a transient response of an oil hydraulic circuit. The validity of the proposed method is demonstrated by this example.

INTRODUCTION OF INNOVATIVE PROGRAM OHC-SIM FOR OIL-HYDRAULIC CIRCUIT SIMULATION

OHC-Sim is an innovative program for oil-hydraulic circuit simulation, which is being developed with the support ofJapan Hydraulics and Pneumatics Society (JHPS). OHC-Sim includes a user friendly GUI (Graphical User Interface) inMicrosoft Windows 95 environment. OHC-Sim provides not only easy design of oil hydraulic circuits, but also quickevaluation of dynamic performance.

気泡の存在する油圧システムの過渡現象の数値解析 張力の働くガスモデル

Absolute negative pressure phenomena occasionally occurs in oil hydraulic circuits containing throttles and pipelines. Here, a new simple simulation technique is proposed by using an SSS (Simple-Stable-Simulation) element which is introduced to solve the nonlinear part including a throttle, in consideration of the surface tension of a contained lumped bubble. This element can be standardized under SSS devices (subroutines). The devices can also treat the systems including distributed parameter systems, under a Runge-Kutta main loop. The simulated results show good agreement with the experimental results.

油撃とポペット弁の相互作用に関する研究

A poppet valve is used solely as a check valve and also included as a pilot part in various kinds of control valves in oil hydraulic circuits; therefore, it is very important to clarify its characteristics.The purpose of this paper is to search the behavior during tens ms when it responds to a quick flow change. In this research, a check valve is used as one of the examples of poppet valves. The composition where an oil hammer influences the valve is treated as one of examples of a quick change in pressure and flow velocity. The composition is an important part of the intensifier using an oil hammer which the authors have been developing and also the result will provide fundamental data to clarify the dynamic characteristics of a hydraulic system with a poppet valve.The transient phenomena are researched by experiments and simulations. For the analysis by simulation, fundamental equations concerning a check valve and those by the characteristics method concerning a pipeline are presented. They are solved simultaneously using the Runge-Kutta methods. The effects of the spring, mass of the poppet, and volume and length at the connective parts on a peak generated pressure is clarified.

Surge reduction in oil hydraulic lines using branch pipes.

Surge phenomena in fluid lines often produce vibrations and noises, or even result in system breakdown. In order to absorb the surge waves, accumulators are conventionally employed in oil hydraulic circuits. In the present paper an attempt to utilize branch pipes for decreasing pressure surge is experimentally tested. The idea depends on the fact that a pipe which branches from the main line and has a dead end dissipates transient waves without affecting the steady-state flow. It has turned out that although branch pipes cannot completely eliminate surges, they are from the practical point of view useful enough to diminish surge pressures, having their own advantages over the conventional accumulator in several aspects.

Oil Hydraulic Circuit Design Expert System as an Integrated Intelligent CAD

Oil Hydraulic Circuit Design Expert System as an Integrated Intelligent CAD

A study of instantaneous flow rate measurement in a high-frequency region, based on hydraulic pipe line dynamics.

Concerning the dynamic characteristics of oil hydraulic pipe lines, experimental research from the view point of focusing on the unsteady flow rate through a pipe is insufficient because of the lack of adequate flowmeters. The authors develop a new system to measure the unsteady flow rate of oil through a circular pipe. The sampling frequency of the measurement is 1.28 kHz. The frequency responses and the transient responses of the oil hydraulic pipe lines are obtained by measuring the flow rate through a certain cross-section of the pipe and the pressure at the section simultaneously. The experimental results are compared with the theoretical results, which are calculated by making use of the so-called frequency dependent friction model. As a result, it is verified for the first time that the theory predicts the rate of the instantaneous flow rate measuring system is sufficient for the general dynamic test of oil hydraulic circuits and equipment.