共查询到20条相似文献,搜索用时 62 毫秒
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激振器的偏置控制是控制激振器围绕偏离液压执行元件(液压缸或液压马达)平衡位置特定距离振动。该文提出了一种高频激振的2D阀控缸电液激振器的偏置控制方法,该方法是通过一个与2D激振阀并联的四通阀实现流量偏置控制的。应用流体动力学和系统动力学理论建立激振器数学模型,非线性仿真分析偏置对活塞位移波形的影响及偏置量与偏置阀开口间的关系;最后,搭建实验平台,分析实际位移波形和实际偏置量变化情况,验证理论分析的准确性。研究结果表明:理论分析与实验结果一致,即提出的偏置控制方案可行,可实现偏置量的独立、精确控制。 相似文献
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《液压与气动》2015,(7)
由于电液高频疲劳试验机采用传统的电液伺服阀难以达到较高的激振频率,为了解决这个问题,采用一种特殊结构的2D激振阀来控制液压缸,从而提高电液高频疲劳试验机的激振频率。该2D激振阀具有双运动自由度,控制阀芯旋转可实现激振频率控制,控制阀芯轴向运动可实现激振幅值控制。由于2D激振阀的转阀特性,无法引入一个偏置信号实现对激振中心平衡位置的偏置控制,因此在对称液压缸上并联一个数字伺服阀,通过改变数字伺服阀的开口大小和方向就可以实现激振器振动中心位置的偏置。基于激振频率与激振幅值控制原理设计了一种采用DSP控制的控制器,该控制器能控制电液高频疲劳试验机的激振频率与激振幅值。同时,实验室已有的控制器能控制并联的数字伺服阀开口大小,从而达到偏置控制的目的。基于电液高频疲劳试验机的工作与控制原理搭建实验平台并做实验。结果表明:该电液高频疲劳试验机的控制系统可实现高达2500 Hz的激振频率,谐振频率为980 Hz,在该频率可进行高频率、大载荷的疲劳实验。 相似文献
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电液激振试验台是在振动机架上安装电液激振器,由激振器产生激振力,作用在实验对象的某一局部区域,使其产生强迫振动。该文根据液压马达的大功率、大扭矩的特点,提出了一种由马达驱动高频激振阀的新型电液激振试验台研究方法。该方法主要是通过液压马达对2D激振阀阀芯的旋转进行驱动,采用流量阀控制进入马达的流量达到控制阀芯转速的目的。应用流体动力学和系统动力学理论建立电液激振试验台数学模型,对建立的试验台进行实验研究,同时测得液压缸活塞输出的激振力波形。实验表明:该试验台可以大幅度地提高激振频率,达到1200Hz以上的激振频率,激振输出波形近似为一正弦波。马达驱动2D阀的新型电液激振试验台是提高液压振动的激振频率的有效途径。 相似文献
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研究2D高频转阀控制液压缸实现谐振疲劳试验新方法。提出2D高频转阀控制单出杆液压缸谐振疲劳试验方案,2D高频转阀阀芯可以双自由度运动,阀芯旋转运动可以控制系统激振频率,阀芯轴向滑动可以控制系统输出载荷力幅值,液压缸无杆腔初始容积变化可以控制系统谐振频率。建立2D高频转阀、单出杆液压缸和阀控缸系统的数学模型,建立阀控缸系统的Simulink非线性仿真模型,仿真研究液压缸无杆腔定初始容积时阻尼对系统输出载荷力幅频特性、相频特性和系统流量的影响,及谐振工况时载荷力波形失真度和载荷力幅值控制方法。试验结果验证了电液谐振疲劳试验新方法的可行性。该方案能有效提高电液疲劳试验的谐振频率,拓展电液高频疲劳试验机在工程领域的应用范围。 相似文献
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电液激振器作为疲劳试验机的关键部件,其发展趋势是向着高频率发展的同时,能保证其较大的激振力输出,以满足工程试验对激振器的高频率大激振力的需求,为此电液激振器的谐振特性研究显得尤为重要。电液激振器系统是由2D阀驱动单出杆液压缸活塞以某一振动中心位置作周期性往复运动。根据流体力学和系统动力学的理论对该系统进行数学建模。通过实验研究与分析发现,随着电液激振器的激振频率的上升,激振力的输出会逐渐减小,但在中间的某个频率段激振力会突然增大,且输出波形更趋近于正弦波,因此可以确定在这一频率段激振器发生了谐振。 相似文献
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Clarence W.DE SILVA 《Instrumentation》2019,(4):72-84
An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t... 相似文献
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INTEGRAL EQUATION METHOD'S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES 总被引:1,自引:0,他引:1
LI Cheng ZHENG Yanping 《机械工程学报(英文版)》2008,21(6):115-118
The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value. 相似文献
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30 keV Ga+ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z2, and shows a non-monotonic relationship between contrast and Z2. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z2, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory. 相似文献
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This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an... 相似文献
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分布动态载荷识别的抗噪处理 总被引:2,自引:2,他引:0
针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性. 相似文献
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针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。 相似文献
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The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar... 相似文献
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The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods.... 相似文献
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J. A. Williams 《Lubrication Science》1997,3(3):267-306
Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface. 相似文献
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CHEN Sunyi 《机械工程学报(英文版)》2007,20(6):13-17
A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion. 相似文献