电流变液技术在液压控制系统中的应用

电流变液是一种流变特性可受外加电场控制的智能材料,该文阐述了电流变液材料的组成、特性和作用机理,介绍了电流变液技术在液压控制系统中的应用.     

基于电流变效应的阀控系统研究

以液压控制理论为基础，以电场作用下表现为Bingham模型特征的电流变液体为工作介质对基于电流变效应的阀建立控制方程，对阀控缸系统进行动静态性能分析与仿真。首次建立以蠕动泵为动力源的基于电流变效应的单元件阀性能测试回路系统试验装置，并对该系统回路进行试验研究。理论分析与试验研究结果表明，影响电流变阀控系统的主要因素是电流变材料的性能参数和电极控制尺寸，基于电流变效应的阀的响应时间在毫秒量级之内。     

电流变材料在结构振动控制中的非线性特性及理论模型

半主动振动控制结合了主动和被动控制的优点,得到了广泛的应用。一种采用电流变材料在线实时改变支撑条件的镗杆被设计用来对切削颤振实现半主动控制。通过试验发现当电流变材料处于屈服前后临界状态时,其在系统中相当于一参数可控的干摩擦阻尼器,致使镗杆的动态特性表现出明显的非线性。根据试验结果对含有电流变材料的镗杆建立了数学模型,从理论上对电流变材料在结构振动中处于屈服前后临界状态的条件和动态特性进行了分析。     

电流变减振器仿真分析

电流变减振器是根据电流变材料具有电流变效应的特性,通过电场来控制电流变流体的流动特性,以实现阻尼力控制。从应用研究的角度出发,将电流变液减振器应用于汽车半主动悬架的减振,通过Matlab/Simulink仿真软件研究模糊控制用于变阻尼汽车半主动悬架控制的可行性。     

专利

一种机床切削颤振在线智能控制方法及其系统。用于精密柔性制造加工领域。系统包括利用电流变材料设计一种动态特性可以在线快速调整的智能型镗杆,向电流变材料施加高压电场的电斥变换器、计算机、电荷放大器及输入加速度信号的加速度传感器,加工系统动态特性在线调整主要依靠含有电流变材料的机械结构进新行。控制方法包括系统初始化、颤振识别和颤振控制三部分。该方法中采用CDM方法在线     

电流变材料抑振机构动态性能测试与分析

电流变材料在振动控制中表现出优良的阻尼抗振性能,但由于电流变材料在振动结构中随振动幅度、振动频率和施加电场强度的变化,其动态性能表现出明显的差异,使控制模型难于准确制定。通过对含有电流变材料的抑振机构进行动态性能测试试验,获取在不同电场强度和不同激振频率下的迟滞曲线,并结合所建立的迟滞曲线数学模型将电流变材料在结构振动控制中所表现出来的动态性能分为牛顿粘性液体、屈服前弹性体、屈服前粘弹体、非线性体和屈服后粘性体,同时,分析了电流变材料不同动态特性出现的条件及其对整个结构动态性能的影响。这种试验分析方法为有效制定电流变抑振机构的控制策略提供了科学依据。     

电控流变智能材料的研究进展及其设计

作为机电控制中的一类重要智能材料,电流变体近年来取得较大进展,较详细地综述了电流变材料的研究发展进程,提出了有关“核壳”型电流变复合固体颗粒材料设计的一些观点,并指出了电流变材料应重点解决的问题。     

自供能电流变弹性体减振器的设计与特性分析

新型智能材料电流变弹性体是电流变材料的衍生体,兼有电流变液和弹性体的优点,在主被动的振动控制领域中有着极大的应用前景。基于电流变弹性体的刚度和阻尼可电控调节的特性以及压电陶瓷的正压电效应,研制一种基于D33挤压模式的压电自供能电流变弹性体减振器,并对其在不同激励和场强下的振动响应特性进行实验分析。试验数据表明相比无场强条件下,在压电供电和1 000 V恒压的条件下能有效增大电流变弹性体结构阻尼,改变减振器振动响应谱峰值的频率和幅值,提高系统的隔振效果。     

电流变减振器用于铣床振动控制的试验研究

试验研究了电流变减振器在铣床颤振控制中的应用。试验发现，电流变减振器的刚度及阻尼随外加电场强度的增加而增大，主振系统的振幅随电场强度的增加而减小。试验表明电流变减振器具有控振效果明显、结构简单的特点。只要场强选取适当，采用电流变减振装置可以控制铣床刀杆系统的颤振。     

电流变阀及阀控系统的研究与分析

介绍了新型智能材料电流变流体(悬浮液型)在液力传输中的应用;运用电磁理论、流体动力学、Bing-ham plastic流体动力模型和静电极化理论,推导出电流变流体控制元件的控制方程,并根据电流变流体控制元件的设计准则,设计了平行平板和同心圆筒型两种电流变流体控制元件;运用现代控制理论和计算机仿真软件(Matlab)对电流变动力元件进行了静态分析,对电流变阀控液压系统进行研究分析。     

电流变夹层梁的动力稳定性分析

将电流变液等效为线性粘弹性材料，并假定在小变形情况下其储能模量和损耗因子与加在它上面的电场成正比，利用Hamilton原理和有限元方法建立电流变夹层梁的动力学方程。分析不同外加电场和厚度比情况下，电流变夹层梁的振动特性及动力稳定性。通过对单频轴向激励作用下电流变夹层悬臂梁的仿真计算显示，外加电场的增大能提高电流变夹层梁的刚度和阻尼损耗，减少不稳定区域的大小，而电流变层厚度的增加将使梁的固有频率降低，但提高了梁的稳定范围。表明合理设计电流变夹层梁可以有效抑制振动，提高系统的稳定性。     

Development of a laboratory test device for electrorheological fluids in hydrostatic lubrication

Electrorheological (ER) fluids exhibit changes in their rheological behaviour in the presence of an external electric field. Research and development activities related to ER fluids and their applications have increased dramatically during the last few decades. If commercialised, ER fluids could have a significant impact on hydraulic equipment, and be utilised in the automotive, marine, aerospace, robotics, and machinery industries. The objective of the present study is to demonstrate the feasibility of using ER fluids to produce ‘smart’ lubricants that can control friction and wear of sliding components. The ER lubricant effect is demonstrated using a unique test machine that utilises hydrostatic lubrication. It is found that the friction torque increases by as much as 30% when a voltage of 2000 V is applied to an ER fluid in the newly developed test machine.     

A modeling study of local equivalence ratio fluctuation in imperfectly premixed turbulent flames

The effect of fluctuation of Equivalence Ratio (ER) in a turbulent reactive field has been studied in order to check the global combustion characteristics induced by the local fluctuation. When the flow is premixed on a large scale, closer examination on a small scale reveals that local fluctuations of ER exist in an imperfectly premixed mixture, and that these fluctuations must be considered to correctly estimate the mean reaction rate. The fluctuation effect is analyzed with DNS by considering the joint PDF of reactive scalar and ER, followed by modeling study where an extension of stochastic mixing models accounting for the ER fluctuation is reviewed and tested. It was found that models prediction capability as well as its potential is in favor to this case accounting the local ER fluctuation. However, the effect of local fluctuation did not show any notable changes on the mean global characteristics of combustion when statistical independence between the reactive scalar and ER field is imposed, though it greatly influenced the joint PDF distribution. The importance of taking into account the statistical dependency between ER and combustible at the initial phase is demonstrated by testing the modeled reaction rate.     

电流变液静态屈服应力的实验研究

本介绍了一种新的电流变液静态屈服应力测试方法,通过一个阀型装置对基于沸石和硅油的电流变液静态屈服应力进行了测试,结果表明,电流变液的静态屈服应力与外加电场强度的平方成正比,并以此作为电流变液器件设计的一个依据。     

电流变阻尼器的频率自适应减振控制

在分析了影响电流变阻尼器的粘性阻尼和屈服阻尼的诸多因素后，提出利用多层电极结构来扩大阻尼器的可控范围。研制了一套可测试电流变阻尼器阻尼系数、响应时间和耗散功率的静特性测试系统。为了充分利用阻尼器的可控范围，对阻尼器与减振系统的匹配设计进行了研究。针对电流变阻尼器的阻尼力具有非线性的特点，提出了以平均阻尼匹配减振系统最佳被动阻尼的设计准则。最后利用电流变阻尼器对双层隔振系统，以正弦扫频信号作为激励，通过在线主导频率的识别，进行了自适应阻尼减振控制试验，结果表明共振频率和高频的振幅减振效果均达到３０％以上。     

电流变技术研究及展望

电流变液是一种新型智能材料,在机械领域有广阔的应用前景。介绍了具有高抗剪强度的电流变液材料配制,体积比率以及温度对电流变效应的影响,电流变液的拉伸、压缩和剪切力学特性、剪切作用下的动态响应,及一些应用基础研究。指出电流变效应机理的不清楚和力学性能的不准确描述是阻碍电流变液广泛应用的重要因素,是今后电流变技术研究中必须克服的问题。     

Fasting induces modifications of the endoplasmic reticulum in intestinal cells

The polymorphism of the endoplasmic reticulum (ER) in epithelial cells with different transport functions such as the enterocyte suggests that the ER may be involved in some way in molecular transport. To further access this possibility, we examined the ER from the intestine of winter flounder, Pseudopleuronectes americanus, a species which undergoes an annual fast of approximately 6 months' duration, a time during which previous work indicates nutrient carrier number does not change. Fish from June (feeding) and January (8–10 weeks fasted) were sampled. Tissues from the pyloric caeca, foregut, midgut, and hindgut were prepared for electron microscopy using two techniques of staining. Cell height was unaltered in any section, although microvillar length shortened variably. Cellular organization, including position of nuclei, number and distribution of mitochondria, and presence of basolateral membranes, did not change. The ER appeared equally abundant in June and January. However, use of the osmium impregnation technique, which is specific for ER cisternal contents, revealed a change in the impregnation of ER, from a heavily impregnated network in summer to little or no impregnation in winter. These results suggest that a shift in function of the ER had occurred when nutrient transport ceased, and supports a role of the ER in nutrient transport.     

Sliding mode control of a shear-mode type ER engine mount

This paper presents feedback control characteristics of a shear-mode type electro-rheological (ER) engine mount. The field-dependent yield stress of an arabic gum-based ER fluid is obtained using a couette type electroviscometer, and it is incorporated into the governing equation of motion of the ER engine mount, which is derived from a bond graph model. A sliding mode controller which directly represents the field-dependent damping force is formulated by taking into account the stiffness and damping properties of the systems as parameter uncertainties. The controller is then experimentally realized by imposing a semi-active actuating condition. The effectiveness of the proposed ER engine mount is demonstrated showing capabilities of isolating the vibrations due to sinusoidal and random excitations.     

电流变技术及其工程应用

介绍电流变技术及其工程应用，说明中国的研究状况，分析电流变技术具有广泛应用前景的原因，探讨电流变效应的成因及其影响因素；从分子运动学角度和电学性质方面解释电流变效应的复杂性，阐述电流变液体在电流变技术中基础性地位，提出电流变液体的工程要求；展望电流变技术在工业领域的应用价值；思考电流变技术工业化进行中出现的问题。