电液步进油缸特性的理论分析及试验研究

针对在高炉和连铸机等重工业恶劣工况下,采用传统液压伺服系统,抗油液污染能力低、可靠性差等问题,依据直接位移反馈闭环控制原理,结合数字化控制方式,开发了步进式电液控制液压缸。阐述了电液步进缸的工作机理,并对其进行数学建模和理论分析,建立了系统传递函数方框图。在试验台上对电液步进缸的内泄漏流量、十脉冲精度、一步精度、重复位置精度和频率响应等静动态性能进行测试,结果表明,电液步进缸在开环状态下也具有较高的控制精度和响应速度,可靠性高、抗油液污染能力强。     

电液步进液压缸在结晶器调宽系统的应用

在钢坯连铸生产过程中,结晶器在线快速调宽技术是提高生产效率和金属收得率的关键。对现有的几种结晶器调宽方式进行了对比分析。对电液步进液压缸的结构特点、工作原理、特性及应用进行了详细介绍。设计了一种基于电液步进缸控制的结晶器调宽系统。改进后的结晶器调宽系统可以满足在线快速调宽要求,电控系统采用开环控制,简单可靠。具有控制精度高,响应速度快,抗干扰能力强,易于维护和故障率低等特点。经过一年半的热负荷运行,各项性能指标均达到设计要求。     

电液步进缸的跟随特性研究

电液步进缸的电液作动器能够有效减少液压系统的重量,降低管路噪声,优化流量脉动,控制溢流噪声,使得电液步进缸得到广泛的研究和应用。但是电液步进缸的跟随特性不能满足某些工程场合的需求。为了提高电液步进缸的跟随特性,根据评价跟随特性的稳态误差指标及稳态误差产生原因,推导出了基于电液步进缸稳态误差的时域模型,并提出参数调整结构。在此基础上对电液步进缸的可变参数Kf进行调整,利用AMESim软件仿真分析电液步进缸典型运动状态下合适的Kf数值,最后通过对电液步进缸进行空载和加载试验获得稳态误差的实验结果。结果表明,电液步进缸的稳态误差在要求的范围内,证明了电液步进缸稳态误差时域模型的正确性以及控制算法的有效性和稳定性。     

电动缸试验过程梯形螺母咬死的解决方案

电动缸是把伺服电机与传动丝杠设计成为一体的模块产品，可以实现平移、旋转、压紧等运动。在产品出厂前需求完成行程范围测试、承载能力测试、传动精度测试及磨合试验等多个测试项目。实际在测试中经常出现活塞杆运行超出行程范围，造成梯形螺母与端盖或轴承衬套咬死的情况。该文通过分析电动缸的结构及工作原理，提出了防止梯形螺母咬死的解决方案，改进了行程限位相关结构，搭建了专用加载试验台，通过样机试验验证，方法可靠，满足电动缸功能性能试验要求。     

电液伺服阀动态特性测试研究

本文采用控制理论研究电液伺服阀的动态特性测试问题。提出了用闭环方法测试电液伺服阀的精度条件,设计了不同类型的低通滤波网络,提出了选择高性能动态测试油缸的要求,分析计算了具有深度电流反馈的伺服放大器,最后分析了测试系统中各环节的匹配关系。     

浅谈插装式比例阀在步进梁式加热炉速度控制上的应用

该文针对步进梁式加热炉升降运动惯量大且执行机构在工作过程中负载变化复杂的特点，通过优化电液比例阀的基准及斜坡给定等相关参数，确保了步进梁升降回路四缸高精度同步控制、平稳运行、准确定位。     

一种步进缸控制阀的制造方法

一种步进缸控制阀的制造方法陈晓静１步进缸的工作原理与技术要求图１所示的一种电液步进缸，是在普通的差动缸的活塞内部设置一套控制螺杆和阀套组成的。与其地形式的步进缸相比，这种步进缸结构最简单。压力油Ｐ＿ｓ从Ｃ口进入缸的有杆腔后到达Ａ控制口，回油控制口Ｂ直...     

电液步进油缸的控制

在概要介绍电液步进油缸的工作原理和特点的基础上,叙述了其基本控制电路的组成和设计要点。     

步进电动机开环驱动

根据步进电机的转速与脉冲频率直接相关,通过恒流斩波、PWM脉冲调宽及细分控制方法,得到很好的输出效果。单片机开环控制步进电动机,进行速度调节、转向控制,介绍了STR672—080芯片控制四相步进电动机,实现16细分,使步进电动机近似匀速运动。同时对采用细分控制的精密注射泵进行实验精度测定,得到细分控制的平均精度达到99．9％以上。     

结晶器液压调宽控制系统研究

阐述了单流板坯连铸机结晶器液压调宽系统的设计、软硬件配置及控制方法。通过控制系统设计与调试,实现了结晶器液压调宽系统冷调宽的目标。     

数字伺服步进液压缸的建模分析

建立了用于六自由度运动模拟器的数字伺服步进液压缸的数学模型。该数字液压缸包括二相混合式步进电动机、四边滑阀、阀控非对称缸、细分驱动器和机械反馈机构等部分。建模和分析中考虑了阀芯受力、步进电机非线性、间隙和死区及摩擦力等问题。基于建模分析，在MATLAB／Simulink环境中对数字伺服步进液压缸系统进行了数值仿真。     

叉车起升液压缸挠度模拟试验研究

参考液压缸试验方法与叉车运行工况,选择起升液压缸承载时挠度变化对密封性能的影响为研究对象,提出了一种适用于起升液压缸挠度模拟的试验方法。通过试验台试验和门架台架试验对比,验证了本试验方法的优越性,为减少起升液压缸的故障发生和降低整机返修率提供了一套性能检测平台。     

Suitability and environ mental compatibility of rapeseed oil based hydraulic fluids for agricultural machinery

Hydraulic fluids based on rapeseed oil tend to oxidise and hydrolyse, especially at temperatures above 80°C. Long-term testing, with thirty-seven agricultural machines, of an Esso PFL hydraulic fluid was carried out to investigate the suitability of rapeseed oil based hydraulic fluids. The operating conditions, notably the kind of work being done and the thermal regime of the hydraulic fluids, were monitored for each machine. Oil refill quantities, repairs, and maintenance were also documented. Samples of the hydraulic fluids were analysed for technical characteristics and element content. Unused rapeseed oil based hydraulic fluids are more rapidly biodegradable and less toxic than mineral oil based hydraulic fluids. However, hydraulic fluids most often come into contact with the environment when they are used, either through accidents or through oil dripping from the hydraulic couplers. It was, therefore, the purpose of a second research project to investigate the environmental impact of rapeseed oil based hydraulic fluids in the course of use. Four rapeseed oil based hydraulic fluids were tested in the field on eight agricultural machines. The relevant operating conditions, such as thermal changes and pressure load, were monitored, and oil samples were analysed, as in the first project. Biodegradability was tested with the CEC L-33-A-94 test and the OECD 302 B test (the Zahn-Wellens method). Aquatic toxicity was determined by different test systems: waste water bacteria, photobacteria, plankton alga, garden cress, Daphnia, and Leuciscus. It was found that, generally, the candidate hydraulic fluids were suitable for use in the machines tested. It was also found that high biodegradability and low ecotoxicity were constant properties throughout the test period. Thus, the hydraulic fluids tested are suitable for application in agricultural machinery.     

Heat removal analysis on steel billets and slabs produced by continuous casting using numerical simulation

Simulation of a continuous casting process (CCP) is very important for improving industrial practices, reducing working times, and assuring safety operating conditions. The present work is focused on the development of a computational simulator to calculate and analyze heat removal during continuous casting of steel; routines for reading the geometrical configuration and operating conditions were developed for an easy management. Here, a finite difference method is used to solve the steel thermal behavior using a 2D computational array. Conduction, radiation, and forced convection equations are solved to simulate heat removal according to a steel position along the continuous casting machine. A graphical user interface (GUI) was also developed to display virtual sketches of the casting machines; moreover, computational facilities were programmed to show results such as temperature and solidification profiles. The results are analyzed and validated by comparison with industrial trials; finally, the influence of some industrial parameters such as casting speed and quenching conditions is analyzed to provide some recommendations in order to warrant safety operating conditions.     

数字液压缸非线性建模仿真与试验研究

以航天器转运平台使用的数字液压缸为研究对象,根据其结构特点和内部闭环控制原理,综合考虑步进电机旋转、丝杠螺旋反馈、阀芯轴向受力、液压缸上的摩擦力这些非线性因素影响,在Simulink中建立精确的数字液压缸非线性模型,并通过试验验证了模型的准确性。利用模型重点分析定位精度的影响因素,结果表明：供油压力波动会降低定位精度;减小步进电机频率可以提高定位精度。同时根据仿真及试验提出了通过调整输入脉冲量提高精度的方法,可以满足转运平台工作时的精度要求。     

Nonlinear Mathematical Modeling and Sensitivity Analysis of Hydraulic Drive Unit

The previous sensitivity analysis researches are not accurate enough and also have the limited reference value, because those mathematical models are relatively simple and the change of the load and the initial displacement changes of the piston are ignored, even experiment verification is not conducted. Therefore, in view of deficiencies above, a nonlinear mathematical model is established in this paper, including dynamic characteristics of servo valve, nonlinear characteristics of pressure-flow, initial displacement of servo cylinder piston and friction nonlinearity. The transfer function block diagram is built for the hydraulic drive unit closed loop position control, as well as the state equations. Through deriving the time-varying coefficient items matrix and time-varying free items matrix of sensitivity equations respectively, the expression of sensitivity equations based on the nonlinear mathematical model are obtained. According to structure parameters of hydraulic drive unit, working parameters, fluid transmission characteristics and measured friction-velocity curves, the simulation analysis of hydraulic drive unit is completed on the MATLAB/Simulink simulation platform with the displacement step 2 mm, 5 mm and 10 mm, respectively. The simulation results indicate that the developed nonlinear mathematical model is sufficient by comparing the characteristic curves of experimental step response and simulation step response under different constant load. Then, the sensitivity function time-history curves of seventeen parameters are obtained, basing on each state vector time-history curve of step response characteristic. The maximum value of displacement variation percentage and the sum of displacement variation absolute values in the sampling time are both taken as sensitivity indexes. The sensitivity indexes values above are calculated and shown visually in histograms under different working conditions, and change rules are analyzed. Then the sensitivity indexes values of four measurable parameters, such as supply pressure, proportional gain, initial position of servo cylinder piston and load force, are verified experimentally on test platform of hydraulic drive unit, and the experimental research shows that the sensitivity analysis results obtained through simulation are approximate to the test results. This research indicates each parameter sensitivity characteristics of hydraulic drive unit, the performance-affected main parameters and secondary parameters are got under different working conditions, which will provide the theoretical foundation for the control compensation and structure optimization of hydraulic drive unit.     

基于变分模态分解和鲁棒性独立成分分析的内燃机缸盖振动信号分离

针对缸盖振动信号中燃烧信号和活塞敲击信号在时频域混叠严重难以分离的问题,用基于VMD和RobustICA的方法分离各独立源信号。通过试验测量内燃机单通道缸盖振动信号,首先对测得的信号进行消除趋势项及滑动平均等预处理,用VMD算法对预处理后的信号进行分解;然后用RobustICA算法提取独立成分,并用组合模态函数法对时域和频域相似性较高的分量成分进行组合;最后结合频谱分析、连续小波变换、相干函数法及倒拖试验对分离得到的结果进行识别验证。研究结果表明：在不同的试验工况下,该方法可以有效地从缸盖振动信号中分离出燃烧信号和活塞敲击信号。     

变距双滑块曲柄驱动结晶器非正弦波形及参数

针对现有液压驱动的连铸机结晶器非正弦振动技术同步性较差、伺服缸偷停和维修量大,以及机械驱动的连铸机结晶器振动装置非正弦振动振幅和特有的波形偏斜率在线不可调的问题,研究开发一种新型的变距双滑块曲柄驱动结晶器非正弦振动发生装置。该装置与以往机械式驱动的非正弦振动发生装置不同,随着变距δ的变化波形函数振幅A和偏斜率也随之变化,实现了结晶器非正弦振动的波形偏斜率、振幅和振动频率均能在线可调,为拉坯速度和振动参数的精确同步控制创造了条件。实现的波形更加符合连铸结晶器振动的机理,在上升期具有较小且较恒定的上升速度,在下降期具有较大的负滑脱速度和较小的负滑脱时间,有利于提高铸坯质量和拉坯速度。驱动装置尺寸小、波形调节简单,投资少,特别便于现有连铸机改造,是一种较理想的连铸机结晶器振动发生装置。