Pressure control of hydraulic servo system using proportional control valve

The purpose of this study is to develope a control scheme for the hydraulic servo system which can rapidly control the pressure in a hydraulic cylinder with very short stroke. Compared with the negligible stroke of the cylinder in the system, the flow gain of the proportional pressure control valve constituting the hydraulic servo system is relatively large and the time delay on the response of the valve is quite long. Therefore, the pressure control system, in this study tends to get unstable during operations. Considering the above mentioned characteristics of the system, a two-degree-of-freedom control scheme, composed of the I-PDD²… feedback compensator and the feedforward controller, is proposed. The reference model scheme is used in deciding the parameters of the controllers. The validity of the proposed control scheme is confirmed through the experiments.     

铰接转向机构液压传动的动载分析

根据运动学和动力学原理 ,对铰接转向机构的恒流液压系统进行了研究 ,并在实例计算的基础上得到结论。为达到等速转向 ,消除动载 ,必须按照一定的规律去改变油缸在转向过程中的供油量     

船舶阀门遥控系统的选用与分析

分析了电动、气动以及液压驱动方式的船舶阀门遥控系统的性能。比较了各种驱动方式的性能与特点。介绍了广泛应用的液压驱动阀门遥控系统的组成。提出了根据舰船实际需要选择阀控系统的具体建议。     

A study on the improvement of release application characteristics of pneumatic brakes for freight train

We have performed experimental studies for the improvements of pneumatic brake systems of freight trains. Currently, most of the freight trains operated by the Korean National Railroad have either empty-load or diaphragm type brake systems. In this study, appropriate methods that the air pressure characteristics in both type of brake systems are in accordance with each other have been investigated. We have also performed running tests using a 30 car-train set to design optimum capacity of a quick release valve. The test results show that the quick release valve is considerably effective in shortening the release time of the diaphragm type brake system. In the case of a normal brake application, the diaphragm type brake system with the quick release valve reduces the release time to 34% of that of the system without the quick release valve. This release time is almost equivalent to that of the empty-load type brake system. Accordance of braking performance in different types of brake systems in a train set is expected to prevent wheel flats and to reduce maintenance costs.     

Realization of direct flow control with load pressure compensation on a load control valve applied in overrunning load hydraulic systems

This paper presents the realization of direct proportional flow control with load pressure compensation feature on a LCV (load control valve). Proportional flow control performance means the flow through the LCV is proportional to the pilot pressure in the control stroke. Proportional flow control decides the overrunning load lowering speed control performance of the whole system. The load pressure compensation feature means when the load pressure is too high, the flow of the LCV can be restricted about the maximum rated flow. The load pressure compensation feature is important to the safety of the system. That is because large flow means undesired fast lowering speed, which will cause accident in applications, especially those large mass overrunning load systems. In this paper, the flow control performance was simulated and the parameter relationship of the orifices was derived, which is the base for the optimizing of the compensation orifice. In addition, load pressure compensation feature was simulated and the compensation orifice size was optimized. Finally, an LCV built according to above methods was tested on a test rig. Experiment data validates the methods presented and the realization of direct flow control with load pressure compensation feature gives guidance for the direct flow control performance development of other valves.     

Research on back- pressure compensation characteristics of a pilot-assisted load control valve applied in overrunning load hydraulic systems

This paper reports the research of proportion flow control with back-pressure compensation feature on an LCV (load control valve). The back-pressure compensation feature means when back-pressure rises, flow of the LCV can be unchanged or lower. The back-pressure compensation feature is very important to the safety of the system, because high back-pressure will make the main valve open larger and lowering speed be undesired faster. In this paper, static equilibrium equations of LCV were established and influence relationship of back-pressure and other parameters was derived. In addition, back-pressure influence was simulated, based on above analysis a preliminary optimization scheme was proposed and tested. After that, the method of back-pressure compensation was proposed and has been verified by simulation. Finally, an LCV with back-pressure compensation feature was tested on the test rig. Experiment data validates that the main flow of the LCV with back-pressure compensation method was lower under a higher back-pressure and the pilot pressure control region was unchanged.     

基于模糊控制的六面顶压机压力控制系统建模与仿真

将先进的电液比例控制技术与计算机控制技术相结合,对六面顶金刚石压机压力控制系统进行了设计,建立了该压力控制的数学模型.运用常规PID控制器的设计方法,设计出了模糊自适应PID控制器,并在MATLAB环境下进行仿真实验.结果表明,采用该控制算法,系统的调节时间缩短,响应速度加快,适应能力和鲁棒性得到提高,系统具有更好的动态特性和稳定性,有效地减少了压力的波动.     

轮齿压力角对齿面接触强度的影响分析

运用赫兹接触理论,分析了轮齿压力角对齿轮接触强度的影响,得出了轮齿强度随压力角的变化规律。发现轮齿压力角的增大,齿面接触正应力和工作剪应力均减小,对提高齿轮强度和防止齿面点蚀极为有利,为重载齿轮的设计提供了理论依据。     

A study on the characteristics of in-cylinder intake flow in spark ignition engine using the PIV

In this study, to investigate m-cyhnder tumble or swirl intake flow of a gasoline engine, the flow characteristics were examined with opening control valve (OCV) and several swirl control valves (SCV) which intensify intake flow through steady flow experiment, and also turbulent characteristics of m-cyhnder flow field were investigated by 2-frame cross-correlation particle image velocimetry (PIV) method In the investigation of intake turbulent characteristics using PIV method, the different flow characteristics were showed according to OCV or SCV figures The OCV or SCV installed engine had higher vorticity and turbulent kinetic energy than a baseline engine, especially around the wall and lower part of the cylinder Above all, SCV B type was superior to the others About energy dissipation and reynolds shear stress distribution, a baseline engine had larger loss than OCV or SCV installed one because flow impinged on the cylinder wall It should be concluded, from what has been said above, as swirl component was added to existing tumble flow adequately, it was confirmed that turbulent intenstty was enlarged, flow energy was conserved effectively through the experiment In other words, there is a suggestion that flow characteristics as these affected to m-cyhnder combustion positively     

A study on the design of electromagnetic valve actuator for VVT engine

Electromagnetic valve (EMV) actuation system is a new technology for improving fuel efficiency and at the same time reducing emissions in internal combustion engines. It can provide more flexibility in valve event control compared with conventional variable valve actuation devices. The electromagnetic valve actuator must be designed by taking the operating conditions and engine geometry limits of the internal combustion engine into account. To help develop a simple design method, this paper presents a procedure for determine the basic design parameters and dimensions of the actuator from the relations of the valve dynamics, electromagnetic circuit and thermal loading condition based on the lumped method. To verify the accuracy of the lumped method analysis, experimental study is also carried out on a prototype actuator. It is found that there is a relatively good agreement between the experimental data and the results of the proposed design procedure. Through the whole speed range, the actuator maintains proper performances in valve timing and event control.     

为提高承载能力的槽轮机构的研究

文中提出了两种为提高承载能力而做了结构改进的槽轮机构,论述了该机构的设计方法。经实践证明,与普通槽轮机构相比,该机构承载能力高,寿命长,适合于重载。该机构进一步开拓了槽轮机构的应用范围,具有广泛的应用前景。     

A numerical study on the characteristics of transient flow in a pressure regulator resulting from closure of the pressure control valve

This study investigates characteristics of transient flow and the possibility of freezing in a pressure regulator and the rear connecting pipe of the pressure regulator during the closing process of the pressure control valve (PCV), which is an essential element in the operation of a natural gas pipeline network. For this purpose, the study develops a numerical model for the PCV and its rear connecting pipe by applying computational fluid dynamics method. The analysis is conducted in each of two cases: (1) a steady-state analysis in the case of normal operation and (2) an unsteady-state analysis in the case of emergency closure in problematic situations. First, we closely examine characteristics of internal flow in the pressure regulator and the rear connecting pipe when the PCV operates regularly with a 50% opening ratio in a steady state. Afterwards, unsteady-state analysis examines characteristics of transient flow, such as lowered pressure and temperature, velocity change, etc., of rear flow in the pressure regulator when the PCV is closed because of trouble in the pressure control system.     

谐波齿轮传动中柔轮载荷分布规律分析研究

提出了关于谐波齿轮传动装置中,柔轮啮合区内载荷分布规律的实验与分析新方法。包括三部分：首先,在载荷状态下,通过安装在刚轮径向方向上三个可装、的活齿,测得大量的啮合数据;其次,通过数学统计方法获得啮合区内切向力Ft和径向力Fr的实验曲线;最后,应用函数逼近法获得载荷区内载荷分布方程。     

单片机控制的电压和无功功率综合自控系统

本文介绍了适用于电力系统各种等级变电站的无功功率综合自控制系统的具体实现方法。该系统以ＡＴ８９Ｃ５２单片机为核心,实现系统的在线闭环控制。给出了系统的总体方案和系统的硬件结构框图以及软件流程。针对系统特点,提出了许多抗干扰措施,实践结果表明这些措施是有效的。     

A study on the speed control performance of a servo-pneumatic motor and the application to pneumatic tools

In this study, the performance of the rotational speed control of a proportional-valve-controlled pneumatic motor is investigated. The main application field of the proposed prototype is the pneumatic tools, which are currently very important manufacturing devices. Generally speaking, it is usually quite difficult to obtain a satisfactory and precise speed control of a servo-pneumatic motor at a low rotational speed because of the nonlinear deadband and stick-slip friction inside the proportional valve. Therefore, the fuzzy-sliding mode controller is proposed. Experiment results show that the fuzzy-sliding mode controller is superior to the traditional PID controller, especially when the command input is set at a low rotational speed. This newly designed prototype may be utilised to develop advanced pneumatic tools.     

A study on the deposit formation in the cylinder and intake valve of a S. I. Engine

A spark ignition engine with port fuel injection (P.F.I.) system was used to accumulate cylinder head deposit (C.H.D.), intake valve deposit (I.V.D.), and piston top deposit (P.T.D.) on an engine dynamometer. In this study, the effect of base gasoline on I.V.D. was examined. The deposit forming tendency and the influence of the fuel component for decreasing deposits have been experimentally examined. The amount of I.V.D. has been observed to increase linearly with the engine operating time. It is also observed that the amount of valve deposit with newly blended gasoline is less than that with base gasoline.     

A study on the behavior characteristics of diesel spray by using a high pressure injection system with common rail apparatus

The effects of change in injection pressure on spray structure in high temperature and pressure field have been investigated. The analysis of liquid and vapor phases of injected fuel is important for emissions control of diesel engines. Therefore, this work examines the evaporating spray structure using a constant volume vessel. The injection pressure is selected as the experimental parameter, is changed from 22 MPa to 112 MPa using a high pressure injection system (ECD-U2). Also, we conducted simulation study by modified KIVA-II code. The results of simulation study are compared with experimental results. The images of liquid and vapor phase for free spray were simultaneously taken by exciplex fluorescence method. As experimental results, the vapor concentration of injected fuel is leaner due to the increase of atomization in the case of the high injection pressure than in that of the low injection pressure. The calculated results obtained by modified KIVA-II code show good agreements with experimental results.