飞机全电式前轮转弯系统设计与优化分析

由于全电飞机具有诸多优点,飞机前轮转弯系统必将向全电化这一方向发展。以飞机全电式前轮转弯系统为研究对象,基于飞机前轮转弯系统基本原理和机电一体化系统设计方法,针对前轮转弯系统对操作控制的要求,设计一套由蜗轮蜗杆式前轮转弯机构与兼具转弯和减摆功能的电传伺服操纵系统组成的全电式前轮转弯系统,并建立仿真模型,进行动态性能优化和仿真分析,对系统的各项功能进行检验,研究结果表明所设计的飞机全电式前轮转弯系统合理有效,能够满足工程应用要求。     

某无人机前起落架摆振动力学研究

针对某小型轮式起降无人机前起落架在滑跑过程中可能存在的摆振问题,首先,考虑其支柱前倾角、结构扭转及侧摆柔性、轮胎与地面作用特性等多个耦合因素,建立了前起的摆振动力学模型。其次,采用Matlab/Simulink对动力学模型进行了仿真分析,以阻尼参数的确定为例,得到了不同阻尼形式下的扭转、侧摆自由度的时域响应曲线,对比了库伦阻尼、线性阻尼、平方阻尼分别作用及组合作用下减摆效果。最后,研制了减摆器及无人机前起样机,并进行了外场滑跑试验。研究结果表明,无人机运行平稳,未发生摆振。线性阻尼和平方阻尼具有较好的减摆效果,既能够较快地耗散摆振能量,又不会产生过大阻尼力矩。     

单气室油气悬架阻尼特性分析

介绍了一种单气室油气悬架结构及工作原理,推导了该油气悬架阻尼特性数学模型,利用Matlab对油气悬架的阻尼力进行了理论计算,得到了油气悬架示功特性曲线,并结合台架试验数据进行了对比,验证了模型的有效性。然后,根据所建立的油气悬架阻尼特性数学模型,改变阻尼孔直径、激振频率、单向阀节流口过流面积等关键参数考察了油气悬架阻尼力的影响因素。研究结果表明:阻尼力随着激振频率的增大而增大,随着阻尼孔直径、单向阀节流口过流面积的增大而减小。     

前轮转弯减摆助力器故障分布的三参数威布尔分布模型

三参数威布尔分布具有很多优点,能充分地描述失效机理,非常适合于作为前轮转弯减摆助力器可靠性数据分析模型。基于使用阶段的随机截尾型可靠性数据,首先提出了采用最小二乘法和相关系数法相结合来估计三参数威布尔分布的参数,在此基础上,提出了基于三参数威布尔分布的前轮转弯减摆助力器可靠性数据分析的方法,最后进行了仿真试验研究。仿真试验结果表明,前轮转弯减摆助力器的三参数威布尔分布模型比两参数威布尔分布模型更为精确。研究成果为航空产品在使用阶段提供了一种更为精确的可靠性分析方法。     

单气室油气弹簧阻尼特性及其影响因素分析

针对某重型特种车辆平顺性研究中单气室油气弹簧阻尼特性的研究问题,基于薄壁小孔理论和范德瓦尔实际气体状态方程,同时根据单气室油气弹簧的结构特点和阻尼的组成建立了相应的阻尼力特性模型,并推导了阻尼系数方程。利用MATLAB软件进行仿真,研究了单气室油气弹簧阻尼特性以及激振频率、幅值、自身结构参数对阻尼系数速度特性的影响。研究结果表明:单气室油气弹簧阻尼特性具有较好的非线性,在压缩阶段的阻尼力较拉伸阶段的大,能够较好地缓解冲击,达到减振效果从而改善车辆行驶平顺性;激振频率和幅值属于外因,仅影响阻尼系数的取值范围,而对其取值及曲率几乎无影响;阻尼系数随活塞杆外径、油管直径的减小而增大,随油管长度的减小而减小。研究结果能对整车振动特性研究中阻尼参数的选取及油气弹簧阻尼特性设计优化等工作提供较为系统的理论支持。     

飞机前轮摆振影响因素分析

为了更好地分析飞机前轮摆振的影响因素,量化初始干扰因素值对临界摆振速度下飞机前轮摆振振幅的影响。基于线性假设,建立了飞机前轮摆振的动力学模型。在起落架结构参数固定的情况下,用特征值分析法求解出飞机摆振的临界滑跑速度。应用MATLAB/Simulink建立仿真框图,绘出飞机前轮摆角在临界滑跑速度下的时域曲线。在临界滑跑速度下,分析了各影响因素初始值对于飞机前进方向上稳定摆振振幅的影响,并提出初值影响因子的概念,计算得到各初始干扰因素的初值影响因子。最后,分析了在临界滑跑速度下,初始干扰因素的大小对飞机前轮稳定摆振频率的影响,并得出初始干扰因素的大小对飞机前轮摆振频率并无影响的结论。     

电动转弯系统减摆器的设计分析

对油液式减摆器的结构和工作原理进行分析,在飞机整个起飞、着陆剖面内的交变载荷下,油液阻尼及弹簧的减摆器结构实现了电动转弯系统主动转弯、滑跑纠偏以及防摆等方面的有机结合,可为相关设计提供参考。     

基于磁流变阻尼器的起落架摆振半主动控制

根据能量法建立了磁流变阻尼器等效线性阻尼系数与电压和振幅的函数表达式;建立了起落架摆振半主动控制的数学模型,采用最大能量耗散的控制策略实现了基于磁流变阻尼器的减摆;讨论了不同稳定距下,飞机滑跑时发生摆振的临界速度随垂直载荷的变化。仿真结果表明,在飞机滑跑速度范围内,磁流变阻尼器减摆性能明显优于油液式减摆器的减摆性能,能够完全抑制摆振,并且对某些系统参数的变化具有鲁棒性。     

飞机前轮转弯减摆助力器故障分析

论文针对某型飞机因前轮转弯减摆助力器卡滞,踩刹车修正滑跑方向失效,导致机轮爆破进行了分析;对改进该型前轮转弯减摆助力器的设计及外场使用有一定的借鉴作用     

旋翼试验台减摆器失效故障的一种模拟方法

提出了一种在模型直升机旋翼故障试验台上模拟减摆器失效故障方法。在桨叶摆振弹簧片上贴不同层数的粘弹性阻尼材料贴片，测试桨叶摆振衰减时间历程，分析其阻尼比变化情况，确定贴6层阻尼材料贴片后，桨叶摆振阻尼明显增大，同时发现变距摇臂机构也会产生较大的附加摆振阻尼。振动谱图表明，这种减摆器阻尼失效故障模拟方法是有效的，为桨叶减摆器失效研究提供了一个简捷、方便的平台。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

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...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

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.     

Non-monotonic material contrast in scanning ion and scanning electron images

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.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

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...     

分布动态载荷识别的抗噪处理

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.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

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。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

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....     

The laboratory simulation of abrasive wear

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.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

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.