Dynamic Modelling and Design of a Servomechanism for Hydraulic Directional-Control Valves

This paper analyses a control strategy applicable in heaVy-duty hydraulic Systems,namely, the introduction of a servovalve to achieve smoother operation of direCtional-control valves that serve also as flow-control valves over two fanges of operating conditions. A mathematical model of the dynamics of the System is etallished and design criteria are obtained from a linearised form of that model. The influence of variations in tile axial force on the spool of the main valve is investigated, and the use of the resultS in the design of systems of the proposed kind is discussed.

Investigation of Semi-Active Hydro-Pneumatic Suspension for a Heavy Vehicle Based on Electro-Hydraulic Proportional Valve

Hydro-pneumatic suspension is widely used in heavy vehicles due to its nonlinear characteristics of stiffness and damping. However, the conventional passive hydro-pneumatic suspension can’t adjust parameters according to the complicated road environment of heavy vehicles to fulfill the requirements of the vehicle ride comfort. In this paper, a semi-active hydro-pneumatic suspension system based on the electro-hydraulic proportional valve control is proposed, and fuzzy control is used as the control strategy to adjust the?damping force of the semi-active hydro-pneumatic suspension. A 1/4?semi-active hydro-pneumatic suspension model is established, which is co-simulated with AMESim and MATLAB/Simulink. The co-simulation results show that the semi-active hydro-pneumatic suspension system can significantly reduce vibration of the vehicle body, and improve the suspension performance comparing with passive hydro-pneumatic suspension.

Research and Development of Electro‑hydraulic Control Valves Oriented to Industry 4.0:A Review

Electro-hydraulic control valves are key hydraulic components for industrial applications and aerospace,which controls electro-hydraulic motion.With the development of automation,digital technology,and communication technology,electro-hydraulic control valves are becoming more digital,integrated,and intelligent in order to meet the requirements of Industry 4.0.This paper reviews the state of the art development for electro-hydraulic control valves and their related technologies.This review paper considers three aspects of state acquisition through sensors or indirect acquisition technologies,control strategies along with digital controllers and novel valves,and online maintenance through data interaction and fault diagnosis.The main features and development trends of electro-hydraulic control valves oriented to Industry 4.0 are discussed.

RESEARCH ON THE PERFORMANCE OF NEW TYPE OF PROPORTIONAL PESSURE AND FLOW CONTROL VALVE

A new closed loop flow controlling principle through correcting the valve'sopening area while load pressure is changing is carried out. Further more a principle using only oneproportional valve to compound control pressure and flow is suggested. By using very simpleproportional throttle valve in structure, the functions that five kinds of proportional valves orany two of them combined possess can be complimented. After analyzing, comparing, and testing thedynamic and static characteristics of valve with different controlling principles and main valvestructure styles, the optimized structure styles and control methods are achieved.

Separate Control of High Frequency Electro-hydraulic Vibration Exciter

The working frequency of the conventional electro-hydraulic vibration exciters,which consist of a servo valve and a hydraulic cylinder,is generally restricted within a narrow range due to limited frequency response capability of the servo valve itself.To counteract such restriction,a novel scheme for an electro-hydraulic vibrator,controlled by a two-dimensional valve（2D valve） and a bias valve in parallel,is therefore proposed.The frequency,amplitude and offset are independently controlled by rotary speed,axial sliding of the spool of the 2D valve and axial sliding of the spool of the bias valve.The principle of separate control was presented and the regulation approach of frequency,amplitude and offset was discussed.A mathematical model of the hydraulic power mechanism for the proposed vibration exciter was established to investigate the relationship between the amplitude and the axial sliding of the 2D valve＇ spool,as well as that between the offset and the axial sliding of the bias valve＇s spool at various frequencies.An experimental system was built to validate the theoretical analysis.It is verified that the 2D exciter is capable of working smoothly in a frequency range of 5- 200 Hz.And its frequency,amplitude and offset can be controlled respectively by either closed loop or open loop method.There is a linear relationship between the output amplitude and the spool axial opening of the 2D valve until a point when the flow rate becomes saturate and the amplitude remains constant.The offset displacement of the cylinder＇s piston is linearly proportional to the axial displacement of the spool of the bias valve,when the valve opening is less than 25%.Thereafter,the slop of the offset curve decreases and tends to saturate.The proposed electro-hydraulic vibration controlled by the 2D valve not only facilitates the realization of high-frequency electro-hydraulic vibration,the high-accuracy of vibration can also be achieved by means of independent controls to the frequency,amplitude and offset.

Study on Valve Management of DEH for Steam Turbine

Valve management is one of the major functions of DEH for steam turbine. It has an important practical significance for the security and economy of the steam turbine. This paper starts from the valve configuration figure of the domestic-type 300 MW steam turbine, and then makes a simple comparison between the two types of valve governing modes. In order to realize the valve control, the structure of control system has been established, in which the roles of the mathematical functions are discussed. On the basis of the experiment of valve flow characteristic, this article carries out a quantitative study on the functions of the valve management and the parameter tuning method. Through a serious corrections, the sequence valve flow characteristic curve is obtained, which can provide significant guidance on the research of valve management of the similar steam turbines.

微小流量旋转直驱伺服阀传控特性分析与优化

针对无人机、战术弹、支线民航等小型飞行器航空发动机燃油计量系统与推力矢量系统微小流量的伺服控制需求,就旋转直驱伺服阀偏心球副传动接口与非全周节流阀口等关键结构进行了尺寸约束设计分析,并就节流阀口宽度、球副偏心距以及驱动电机转动惯量等重要参数进行了优化分析,给出了伺服阀结构设计的优化区间。在此基础上,研究提出了电机转角与电流双闭环控制方法,幅频响应实测结果与理论分析较为一致,200 Hz以上高频响应满足实际需求,且双闭环控制方法大幅降低了伺服阀响应超调并提升了稳定性。

船用三通调节阀流-固耦合噪声数值模拟

针对船用PN10DN32三通调节阀噪声声压频谱、声指向性等声学特性规律不明确,噪声声压级是否满足使用要求的问题,基于流-固耦合理论,同时考虑流-固耦合面及流体域内的脉动声学激励源,开展阀门噪声数值模拟研究。分别对三通调节阀在80%及60%开度阀外1 m处的噪声进行数值模拟,分析研究噪声声压频谱特性及声指向性规律。结果表明:80%及60%开度下的噪声声压级分别为49.14 dB(A)、50.79 dB(A),均小于60 dB(A)的噪声限制,满足使用要求。该文为船用三通调节阀噪声数值模拟提供了理论及方法参考。

A differential control method for the proportional directional valve

For the proportional directional valve controlled by two proportional solenoids, the normal control method(NCM) energizes only one solenoid at a time. The performance of the valve is greatly influenced by the nonlinearity of the proportional solenoid, such as dead zone and low force gain with a small current, and this effect cannot be eliminated by a simple dead-zone current compensation. To avoid this disadvantage, we propose the differential control method(DCM). By employing DCM, the controller outputs differential signals to simultaneously energize both solenoids of the proportional valve, and the operating point is found by analyzing the force output of the two solenoids to make a minimum variation of the current force gain. The comparisons of the valve response characteristics are made between NCM and DCM by nonlinear dynamic simulation and experiments. Simulation and experimental results show that by using DCM, the frequency response of the valve is greatly enhanced, especially when the input is small, which means that the dynamic characteristics of the proportional valve are improved.

高压阀口液动力补偿控制策略仿真分析

直动式比例伺服阀是一种新型的单级伺服阀,采用比例电磁铁或线性力马达直接驱动滑阀运动,具有成本低、频响高、抗污染能力强等优点,广泛应用于注塑机进给控制、轧机板厚控制系统等高速高精度液压控制系统中。传统的直动式比例伺服阀采用PID控制策略实现阀芯的精确位置控制,在高压大流量工况下(供油压力达到20 MPa、流量大于100 L/min),阀芯受到液动力扰动变得更加剧烈,易出现响应速度慢、阀芯抖动的现象,影响了比例伺服阀的控制精度。为了解决大液动力扰动的问题,提出了一种基于指数收敛干扰观测器的滑模控制器。通过建立阀芯动力学模型来设计滑模控制器,保证阀芯位置的高动态跟踪性能;使用基于指数收敛的干扰观测器,估计阀芯动力学模型中液动力的不确定性扰动,解决高压大流量工况下的阀芯液动力扰动补偿问题。搭建了比例伺服阀系统的联合仿真模型进行仿真验证,结果表明,提出的控制器可以解决高压大流量工况下阀芯液动力扰动对阀芯位置控制的干扰问题。

船用合流型三通调节阀声流固耦合声学特性研究

针对合流型三通调节阀噪声声压频谱、声指向性等声学特性规律不明确的问题,基于声流固耦合理论,以PN50 DN250三通调节阀为研究对象开展声学特性研究。基于k-ε模型分析阀门定常流动,在定常流动收敛的基础上开展LES非定常流动分析,并导出流固耦合面及流体域内的时域脉动信息作为噪声激励源,开展三通调节阀不同工况下的声学特性研究。搭建三通调节阀流噪声试验台,试验工况下数值模拟噪声与实测噪声声压仅相差1.85 dB(A),验证声流固耦合数值模拟方法的准确性。分别数值模拟阀门实际工况下80%及60%开度下的噪声声学特性,总结出阀门噪声声压级分别为51.18和54.13 dB(A),验证三通调节阀噪声满足使用要求,提出的声流固耦合数值模拟方法可为合流型三通调节阀声学特性分析提供一定参考。

电液控换向阀流场仿真与响应面预测

大流量电液控换向阀是支架液压系统的关键控制元件之一,仿真手段对于换向阀的流动特性分析具有重要意义,然而流体仿真存在计算复杂度高、仿真时间较长的问题,对于要求实时高效流动特性分析的场合并不适用。因此,针对大流量电液控换向阀在不同阀口开度、不同入口压力、不同流量下的流场分布情况进行了仿真分析,发现换向阀入口压力随阀口关闭值呈指数上升趋势,随流量增加呈上升趋势,与出口压力值接近正比关系,并且阀口关闭位移越大换向阀入口附近涡流越剧烈。在换向阀流场仿真的基础上采用均匀抽样方法进行试验设计,提出并建立了基于多维勒让德正交多项式的响应面模型,采用均方根误差、决定系数和经过调整的决定系数,验证了响应面模型替代Fluent仿真模型进行流场分析的准确性和快速性,通过前期少量的流场仿真数据建立响应面模型,实现了大流量电液控换向阀流动特性的实时高效预测。

两通压力补偿器测试方法的研究

介绍一种ZDC两通压力补偿器的结构及工作原理,以及两通压力补偿器串联在比例换向阀进油口的流量输出稳定性原理。根据原理分析两通压力补偿器的常见故障,包括:主阀芯无动作、弹簧端面磨损或者断裂、梭阀阀芯卡阻。设计了一种两通压力补偿器的测试方法,能够测试流量与控制信号、压力与控制信号特性曲线。该方法能够快速、准确地诊断两通压力补偿器的常见故障部位,为设备疑难故障分析和两通压力补偿器的修复提供技术参考。

谷物联合收获机底盘自动升降液压系统设计与试验

针对小型谷物联合收获机在丘陵区作业倾斜角度大、通过性差等问题,开展谷物联合收获机底盘自动升降液压系统设计与试验。本研究设计了底盘自动升降液压系统总体结构,对内置位移传感器液压缸、比例换向阀等关键部件进行设计和选型,提出了基于横向倾斜角度伸缩液压缸进行调平和升降的方法,采用自动调平控制和手动调平两种调平模式对底盘进行调平。应用AMEsim开展液压系统的仿真分析,发现换向时液压缸压力与流量稳定,位移速度平稳。设计了以PLC控制器和PID控制方法为核心的调平控制策略,通过调节液压缸长度实现对底盘的姿态调节,并开展静态调平试验。结果表明:比例换向阀开度范围为20%~45%时,能有效控制液压缸伸缩速度;调节时间随倾斜角度增加而增加,在倾斜角度7.7°范围内的总体调节误差低于0.5°,可满足谷物联合收获机对底盘横向调平的需求。该研究提出了依据横向偏角实现调平的液压系统和控制方法,为小型谷物联合收获机底盘调平液压系统设计提供参考。

Proportional directional valve based automatic steering system for tractors

Most automatic steering systems for large tractors are designed with hydraulic systems that run on either constant flow or constant pressure. Such designs are limited in adaptability and applicability. Moreover, their control valves can unload in the neutral position and eventually lead to serious hydraulic leakage over long operation periods. In response to the problems noted above, a multifunctional automatic hydraulic steering circuit is presented. The system design is composed of a 5-way-3-position proportional directional valve, two pilot-controlled check valves, a pressure-compensated directional valve, a pressurecompensated flow regulator valve, a load shuttle valve, and a check valve, among other components. It is adaptable to most open-center systems with constant flow supply and closed-center systems with load feedback. The design maintains the lowest pressure under load feedback and stays at the neutral position during unloading, thus meeting the requirements for steering. The steering controller is based on proportional-integral-derivative(PID) running on a 51-microcontroller-unit master control chip. An experimental platform is developed to establish the basic characteristics of the system subject to stepwise inputs and sinusoidal tracking. Test results show that the system design demonstrates excellent control accuracy, fast response, and negligible leak during long operation periods.

有限空间下圆柱螺旋组合弹簧优化设计

增大弹簧复位力可提高换向阀弹簧复位的可靠性,考虑电液换向阀主阀弹簧复位动作,以弹簧复位力最大为目标,建立了有限安装空间约束条件下圆柱螺旋组合弹簧优化模型,对双弹簧进行了优化设计,并结合实际试验条件搭建了换向阀图形化仿真模型,仿真所得换向阀主阀复位过程负载口压力动态变化与试验测试结果一致性较好,验证了设计方法的有效性。

电比例换向阀自抗扰控制策略

对煤矿设备中应用的电比例换向阀展开研究,基于建模与辨识得到阀的传递函数模型,研究阀的位置控制算法,并提出自抗扰控制(ADRC)策略。仿真结果验证了所提算法要优于逆模型控制与传统的PID控制器,为提升煤矿装备电液系统性能及同类型换向阀性能优化提供了参考。

水下电液复合控制系统方向控制阀技术现状

方向控制阀是水下电液复合控制系统的核心部件。以方向控制阀为研究对象,首先介绍水下生产控制系统的国际标准对方向控制阀的具体规定,了解方向控制阀的脱锁压力、性能要求、泄漏测试及清洁度要求等;其次分析国外知名厂家生产的方向控制阀的设计参数、结构原理及解决方案等,介绍了国外知名特种化学品公司提供的特制液压油;再次总结了国内方向控制阀的技术研究现状;最后结合我国海洋油气田开发迫切需求,提出方向控制阀研制建议,为方向控制阀国产化奠定基础。

基于STM32的比例阀控气缸位置伺服控制器

传统的工控机控制系统具有成本高、功耗高、体积大、操作复杂等特点,针对这些问题,提出了一种基于嵌入式技术的比例方向阀控气缸位置伺服控制方法。首先,分析了气动位置伺服控制器的实际需求,设计了控制器的最小系统、主控板、模数扩展板和数模扩展板的硬件电路;然后,在集成开发环境Keil MDK下,使用C语言进行了嵌入式软件编写,在跨平台嵌入式软件编程环境Qt下,使用Visual C++语言进行了上位机软件编写;最后,为了验证气动位置伺服控制器的有效性,搭建了比例方向阀控气缸位置伺服控制实验平台,利用所开发的嵌入式气动位置伺服控制器,分别进行了气缸的定位控制和轨迹跟踪实验。实验结果表明:该伺服控制器能够简单、有效地实现气缸位置控制的目的,在跟踪频率为0.5 Hz的参考轨迹时,轨迹跟踪最大误差约为4.6 mm;在跟踪频率为0.25 Hz的参考轨迹时,轨迹跟踪最大误差约为3.1 mm。研究结果表明:该位置伺服控制方法具有良好的控制性能,能够适用于对控制精度要求不是特别苛刻的场合。

特高压直流输电系统中送端LCC换流站的电压平衡控制策略

与高压直流输电相比,特高压直流输电拥有更高的电压等级,能够以更低的经济成本实现稳定、高效的大规模电力输送。该文针对特高压直流输电系统中送端换流站的高低压阀组所存在的电压不平衡问题,分析电压不平衡现象产生的机理,并提出一种基于电压变化量对换流阀组电流参考值进行动态修正的电压平衡控制策略。然后,基于PSCAD/EMTDC搭建特高压直流输电系统的电磁暂态仿真模型,通过在稳态时切除/投入电压平衡控制策略及送端功率阶跃和送端交流系统故障3种不同工况,观测系统的动态响应特性。结果表明,所提电压平衡控制策略简单有效,且在不同工况和不同交流系统强度下都具备较好的控制效果。