6自由度液压机器人的自抗扰控制

为提高6自由度液压机器人电液驱动系统的控制性能,针对电液位置伺服系统的非线性和不确定性,建立了6自由度液压机器人后臂电液位置伺服系统的数学模型,提出了3阶自抗扰控制方案,通过对系统内扰和外扰进行估计和补偿,实现对位置的控制。仿真结果表明,所设计的自抗扰控制器不仅能满足系统对快速性和准确性的要求,而且还能有效抑制负载突变或未知扰动对系统性能的影响,与传统PID控制相比,其具有更强地鲁棒性和抗扰动能力,能满足6自由度液压机器人控制系统动态性能的基本要求。     

60MN水压机电液伺服系统自抗扰控制研究

介绍了60 MN水压机电液伺服系统的组成及工作原理,针对电液位置伺服系统负载变化的复杂性,在分析了负载特性的基础上,提出了自抗扰的控制策略以提高电液伺服系统的可控性和鲁棒性,并对自抗扰控制器进行了结构分析与设计。最后采用MATLAB/Simulink建立了水压机电液伺服控制系统整体仿真模型,对不同负载变化频率下的自抗扰控制效果进行了仿真研究,结果表明:与PID控制器相比,自抗扰控制不仅提高了电液位置伺服系统的响应速度,有效地降低了系统的超调量,而且增强了控制系统的鲁棒性。     

大行程直线运动平台自抗扰控制

大行程直线运动平台是复杂的非线性时变系统,系统的不确定因素较多。针对平台运动过程中受到的内扰和外扰问题,采用线性自抗扰控制进行控制。建立系统的动力学模型,分析系统非线性的原因;将系统的速度、位移作为状态变量,设计一个线性自抗扰控制器。将异于积分标准性系统的部分视为系统的总扰动,并在控制器中进行补偿。在仿真与工程实验中,分别加载S形曲线、正弦曲线运动,并进行抗扰性实验,将实验结果与PID控制算法进行比较。实验结果表明:在外部条件相同的情况下,线性自抗扰控制器不仅响应速度快、精度高,并且具有较强的鲁棒性,具备较好的工程应用前景。     

电液力伺服系统参数自整定模糊PID控制器设计

针对飞机结构强度试验中常用的电液力伺服系统,讨论了系统组成和数学模型。利用MATLAB设计参数自整定模糊PID控制器以克服系统非线性和负载扰动的影响;通过系统辨识建模的方法,采用预报误差法得到系统ARMAX参数模型辨识结果;以辨识结果为对象对设计的参数自整定模糊PID控制器进行Simulink仿真。结果表明:相比常规PID控制器,采用参数自整定模糊PID控制器进行控制,系统具有更好的稳态精度、快速性和鲁棒性。     

机床用直线伺服系统改进型ADRC设计

针对永磁直线电机伺服系统存在纹波推力扰动、负载扰动、摩擦力扰动和其他不确定性扰动,文章提出了一种双闭环改进型自抗扰控制器优化设计方法.针对永磁直线同步电机(PMLSM)系统,设计了速度环和位置环自抗扰控制器,并对一阶自抗扰控制器(ADRC)进行了优化,在保证控制器性能的前提下,省略掉ADRC模型中的非线性跟踪微分器(TD)环节,同时为有效降低模型复杂程度,减小算法计算量,采用线性比例调节代替非线性状态反馈控制律(NLSEF),实现了永磁直线同步电机的改进型双闭环自抗扰控制.仿真结果表明,该自抗扰控制器能够很好的解决强耦合和非线性问题,能够提高系统的响应速度,减小稳态误差且无超调,对负载扰动、电机参数变化具有良好的鲁棒性.     

插装式比例节流阀自抗扰控制研究

为了克服插装式比例节流阀中流量增益非线性、液动力、摩擦力等多种非线性扰动对阀芯控制性能的影响,提出了三阶自抗扰非线性控制策略。以DN80大流量插装式比例节流阀为研究对象,通过系统辨识的方法建立了较准确的数学模型,并进行了验证。在此基础上设计了三阶自抗扰控制器,并对设计的控制器参数进行了整定优化。通过仿真和实验分别对插装式比例节流阀主阀芯的阶跃响应的快速性和抗干扰特性进行了研究。结果表明:采用自抗扰控制下的主阀芯在阶跃激励下的响应和抗干扰能力方面明显均优于PID控制,系统具有较好的动静态性能和鲁棒性。     

基于线性自抗扰的并联液压系统同步控制北大核心

针对并联液压系统的强耦合、非线性、以及内外不确定性扰动造成同步性差的问题,提出基于线性自抗扰控制的同步控制策略。首先,基于流量连续性方程建立并联液压系统的压力与负载微分模型;然后,基于自抗扰控制理论,变换系统的状态空间方程,并将参数不确定性、扰动不确定性、模型不确定性等视作“总扰动”,设计了三阶线性自抗扰同步控制器;最后,在AMESim中搭建了并联液压系统模型,并导入MATLAB/Simulink模块,通过联合仿真验证了所提控制方法的有效性,进一步地与PID控制进行比较。结果表明,基于线性自抗扰的同步控制策略下的并联液压系统的同步精度高,鲁棒性强,为对并联液压系统同步性要求较高的重载工业工程提供了新的控制思路。     

交流永磁同步系统的自抗扰控制研究

为了提高控制系统的鲁棒性,给出了交流永磁电机的速度环自抗扰控制方案.该控制方案不需要精确电机参数就可以实现扰动补偿,控制器的设计也不需要建立电机和负载的精确数学模型.自抗扰控制器利用其内部的扩张状态观测器可以估计出系统的内外扰动,据此将电机等效为由一个非线性系统构成的串联对象,设计出一阶自抗扰控制器实现对电机的转速控制.实验结果表明,自抗扰控制器对电机模型的不确定性和外部扰动变化具有较强的适应性和鲁棒性,控制系统具有优良的动态性能.     

电液位置伺服系统低阶自抗扰控制研究

电液位置伺服系统是一种时变非线性、外部扰动未知且数学模型复杂的高阶系统,对其采用的高阶自抗扰控制方法,需要整定参数较多,模型结构复杂,在实际工程应用中难以实现。针对这个问题,对电液位置伺服系统的一阶和二阶自抗扰控制(ADRC)性能进行研究,实现电液位置伺服系统的低阶自抗扰控制。基于Simulink建立的电液位置伺服系统的低阶自抗扰控制系统,给定阶跃和正弦信号指令,并对系统施加一个负载扰动力,分析系统的响应速度、准确性和抗干扰能力。结果表明,一阶和二阶自抗扰控制都可以使电液位置伺服系统达到稳定状态,且二阶非线性自抗扰控制系统响应速度更快,控制精度高,鲁棒性更强。     

电液位置伺服系统高增益自抗扰控制

针对电液位置伺服系统采用自抗扰控制策略时,存在因系统阶数过高导致状态观测器需观测的变量多、观测信息相位滞后以及易引起系统响应滞后及超调等问题,采用高增益自抗扰控制方案。对系统模型进行降阶处理,以简化控制器结构,减少待整定参数;在传统扩张状态观测器的基础上,进一步对系统总扰动的微分信号进行观测,观测系统扰动的变化趋势,产生有效的超前补偿信号,从而提高系统控制性能及抗扰能力。最后,通过MATLAB与AMESim进行联合仿真。结果表明：该控制方案相比于传统自抗扰控制,系统超调量降低85%,响应速度提高47.7%,并有效提高了系统抗干扰能力,具有更优良的动态及稳态性能。     

Influence of metal ions on the formation of artificial zinc rusts

The artificial rust particles were prepared from ZnCl₂ solutions dissolving Al(III), Fe(III), Fe(II), Ni(II), Co(II) and Mg(II) at different atomic ratios from 0 to 0.3 in metal/Zn. With increasing metal/Zn the crystal phases of the products turned following as ZnO → a mixture of ZnO and Zn₅(OH)₈Cl₂ · H₂O (ZHC) → ZHC. Al(III) most facilitated the formation of ZHC but Mg(II) and Fe(III) produced no ZHC. The morphology of the formed particles varied following as agglomerate → fine → rod → sheet → irregular with the increase of metal/Zn. The sheet and irregularly shaped particles were identified as ZHC and the other particles as ZnO.     

NiAl－Fe金属间化合物合金的正电子寿命谱

测量了塑性金属间化合物合金Ｎｉ（５０）Ａｌ（３０）Ｆｅ（２０），Ｎｉ（５０）Ａｌ（２０）Ｆｅ（３０）和Ｎｉ（６０）Ａｌ（２０）Ｆｅ（２０）单晶和多晶的正电子寿命谱．基于正电子寿命谱的特征参数引入了正电子双区域捕获模型，并讨论了这些合金微观结构与力学性能之间的关系．     

NiAl—Fe金属间化合物合金的正电子寿命谱

测量了塑性金属间化合物合金Ｎｉ５０Ａｌ３０Ｆｅ２０，Ｎｉ５０Ａｌ２０Ｆｅ３０，Ｎｉ６０Ａｌ２０Ｆｅ２０单晶和多晶的正电子寿命谱。基于正电子寿命谱的特征参数引入了正电子双区域捕获模型，并讨论了这些合金微观结构与力学性能之间的关系。     

Effect of dislocation density on the low temperature aging behavior of an ultra low carbon bake hardening steel

Strain aging was studied in an ultra low carbon (ULC) steel with a total carbon content of 20 ppm (wt.%) in order to identify the process stages and mechanism of bake hardening in this type of steel. The effects of dislocation density, varied by means of uniaxial tensile prestraining (1–10%) on the aging kinetics were investigated within an aging temperature range of 50–170°C. The aging was evaluated by means of strength measurements and the determination of interstitial carbon content after aging using a piezoelectric composite oscillator operating at 40 kHz. The interaction between interstitial carbon and dislocations was examined through amplitude dependent internal friction measurements. The influence of dislocation density on the aging behavior have been discussed with reference to the kinetics and mechanism of the aging process.     

Effect of solution heat treatment on galvanic coupling between intermetallics and matrix in AA7075-T6

Susceptibility to localised corrosion is strongly affected by heat treatments performed on Al-Zn-Cu-Mg alloys. In order to study how galvanic coupling between intermetallics and matrix is affected by solution heat treatment, AA7075-T6 and solution heat treated AA7075 have been characterised by means of scanning electron microscopy and scanning Kelvin probe force microscopy. Solution heat treatment strongly increased the Volta potential difference between the intermetallics and the surrounding matrix showing a strong increase in galvanic coupling. This is explained by Zn and Mg enrichment of the matrix caused by dissolution of strengthening particles during solution heat treatment.     

Characterizing corrosion behavior under atmospheric conditions using electrochemical techniques

AC and DC electrochemical experiments were performed as a function of humidity and contaminant concentration in an effort to identify the range of atmospheric environments where corrosion processes could be detected and possibly quantified. AC measurements exhibited two time constants at 25% relative humidity (RH), possibly indicating the ability to resolve both electrolyte resistance and interfacial impedance. Galvanic current measurements were sensitive to the presence of Cl_2(g) at 30% RH and electrochemical transients were detected at both 30% and 50% RH levels, also indicating sensitivity to interfacial processes. Higher humidity levels allowed better quantification due to decreasing electrolyte and interfacial impedances.     

A study on the deactivation of an IrO2–Ta2O5 coated titanium anode

The deactivation of an IrO₂–Ta₂O₅ coated titanium anode was studied during an accelerated life test at 2 A cm⁻² in 1 mol dm⁻³ H₂SO₄ solution using CV, EIS, SEM and EDX. The changes of voltammetric charge, double layer capacitance, oxide film resistance and charge transfer resistance of oxygen evolution with time during the electrolysis were monitored. The morphology and surface composition of the oxide anode before and after electrolysis test were analysed. A comprehensive process of deactivation of the oxide anode was proposed based on the test results and analysis.     

Electrochemical behaviour of amorphous and nanoquasicrystalline Zr-Pd and Zr-Pt alloys in different environments

The corrosion behaviour of melt spun amorphous and nanoquasicrystalline Zr₇₀Pd₃₀ and Zr₈₀Pt₂₀ alloy ribbons has been investigated using potentiodynamic polarization study in NaCl, H₂SO₄ and NaOH solutions at different concentrations. The amorphous and nanoquasicrystalline alloys show better corrosion resistance than Zr in all the solutions studied. Both the alloys are susceptible to chloride attack and pitting has been observed. Complete passivation has been observed in H₂SO₄, while gradual break down of passivating layer occurs in NaOH. In general, nanoquasicrystalline state in both the alloys shows better corrosion resistance than amorphous state in all the solutions studied.     

Corrosion behaviour of powder metallurgical and cast Al-Zn-Mg base alloys

The behaviour of Al-Zn-Mg base alloys produced by powder metallurgy and casting has been studied using potentiodynamic polarisation in 0.3% and 3% NaCl solutions. The influence of alloy production route on microstructure has been examined by scanning electron microscopy, Auger electron spectroscopy and secondary ion mass spectrometry. An improvement in performance of powder metallurgy (PM) materials, compared with the cast alloy, was evident in solutions of low chloride concentration; less striking differences were revealed in high chloride concentration. Both powder metallurgy and cast alloys show two main types of precipitates, which were identified as Zn-Mg and Zr-Sc base intermetallic phases. The microstructure of the PM alloys is refined compared with the cast material, which assists understanding of the corrosion performance. The corrosion process commences with dissolution of the Zn-Mg base phases, with the relatively coarse phases present in the cast alloy showing ready development of corrosion.     

Characteristics and lacquer adhesion on dip and CDC chromium passivated tinplate

Chromium passivation and lacquering are typically used to improve the corrosion resistance of tinplate in packed food. In this work, the nature of the chromium passivation layer formed during dip or CDC passivation treatments, as a function of operational parameters, and its influence on lacquer adhesion, was investigated using electrochemical polarisation, XPS, Auger and lacquer peel-off tests. It was found that dip passivated tinplate provide the best lacquer adhesion, and that the adhesion on CDC treated tinplate could be improved by buffering or lowering the pH of the chromium (VI) solution.