基于TPS54340的多功能数控电源

设计并实现了一种基于DC/DC转换器的多功能数控直流电源,将12~30 V的输入波动电压变换为3.3~10 V的稳定电压输出,并通过电流串联反馈实现恒流,使该电源具备稳压源和恒流源功能;单片机作为核心实现数字化控制,通过2片12位高精度D/A转换器分别控制稳压源和恒流源的输出,并可由键盘设定输出数值,还能步进调节。该电源输出稳定、纹波小、效率高,可作为中间级DC/DC转换电源或特种电源使用,有较高的实用价值。     

精密直流恒流源开发

开发了一种基于电流闭环反馈控制的数控直流恒流源,介绍了该电路的设计思路.提出由D/A转换器输出为粗调,数字电位器输出为微调的组合D/A输出信号的新方法.将该D/A组合输出信号做为电流环给定值,最小给定值可达0.01 mA.实验结果表明,该电路简单,调整方便,控制精度高,稳定性能好,纹波系数小,具有广泛的应用前景.     

基于单片机仿真功能的数控直流稳压电源设计

通过数控直流稳压电源设计实例介绍了Proteus在单片机仿真开发中的实践应用。数控直流稳压电源采用高可靠性的AT89C51单片机作为核心控制芯片,系统由具有8位分辨率的双通道A/D转换芯片ADC0808、电流输出型8位D/A转换器DAC0832、电流放大模块电路、显示模块电路组成。通过Proteus软件成功实现了数控直流稳压电源的设计仿真过程,经仿真表明,利用Proteus软件进行仿真设计可极大地简化单片机程序在目标硬件上的调试工作。     

基于单片机的数控直流电流源设计与实现

介绍利用单片机系统、D/A与A/D转换器和恒流源电路实现输出范围为20～2000mA的数控直流电流源的设计,文中给出了数控直流电流源设计框图和主要电路.采用负反馈闭环控制系统,提高了电流源的输出精度.经测试表明,所设计的电流源具有性能可靠、精度高的优点.     

高精度A/D转换器的设计与实现

高精度A/D转换器实际测量中有着广泛的工程应用,其中三斜积分式A/D转换电路具有结构简单、线性度好的优点。为实现高精度设计,对积分过程的精确控制和高位数计数器的设计尤为关键。该设计为16位高分辨率的双积分式直流A/D转换器,积分电路采用普通元器件实现,利用89S51单片机及FPGA器件实现数字计数及显示功能,同时采用89S51单片机编程实现直流电压表量程的自动转换、自动校零和液晶显示等功能。     

基于MSP430F169的数控直流电流源设计

介绍了一种数控直流电流源的方案,给出了硬件组成和软件流程.采用负反馈闭环控制系统进行稳流,以MSP430F169单片机为核心控制电路,利用其内置的12位D/A模块产生稳定的控制电压、12位A/D模块完成电流测量.该电流源还具有电流可预置、可步进调整以及LCD液晶同时显示电流预置值和实测值等功能.测试表明：系统性能可靠、纹波电流小、控制精度高、实用性强.     

高精度智能定硫仪的设计

为了测量煤中硫的含量,设计了基于库仑滴定法的高精度智能定硫仪.对智能定硫仪的结构和工作原理进行了介绍,重点分析了仪器的数据采集模块、电解电流控制模块和炉温控制模块.该仪器采用12位串行A/D转换器对4路输入信号进行采集,通过冷端补偿和PID控制实现了炉温的高精度测量与控制,并采用D/A转换器对电解电流进行精确控制,最后对测量数据的精密度和准确度进行了检验.测试结果表明,用该仪器测量低硫煤时标准偏差为0.012%,测量高硫煤时标准偏差为0.027%,精度远高于国家标准.     

高频响双向开关式恒流源设计

针对"现有模拟式恒流源只能单向输出且效率低,而已有的数控式恒流源系统复杂、成本高、响应速度又比较慢"的普遍不足,提出了一种新颖的基于模拟PWM控制器的双向高频响开关式恒流源电路。该方案采用了脉宽调制控制器芯片MCP1630和集成功率H-桥L6201P作为核心,由设定输入电压和高边电流采样反馈所形成误差通过MCP1630内PI闭环实现了电流可控调节。实验测试结果表明,该电流源满载输出范围达±2 A,电流调节精度±5%F.S,响应频宽超过700 Hz;该电流源响应快,功耗和成本低,适应于高速双向比例电磁铁驱动要求。     

数控直流电流源的设计

采用电流采样反馈调整控制技术,控制过程是利用达林顿管TIP122组成恒流源,结合放大电路,MD转换电路,单片机最小控制系统,D／A转换电路等构成电流可预置并能实时显示电流大小的闭环系统。通过发射极取样电阻将电流转化成电压,利用A／D转换电路将实际值输入到单片机,由单片机与预设值进行比较调整,利用D／A转换电路控制基极电位,以达到控制电流稳定输出的目的。通过以7805、7812为核心将市电进行降压、整流、滤波等环节输出稳定直流电压来对该系统的各模块供电。由于采样之后,单片机进行反馈调整控制,使该系统具有可靠性好,精度高,稳定性好等优点。     

基于STC12C5A60S2单片机的简易电阻测试仪设计

为了实现对微小数值的电阻进行准确和高精度的测量,本文设计了以STC12C5A60S2单片机为核心,利用直流电压源和运算放大器组成一个多值恒流源,实现多量程电阻精确测量。利用单片机内部集成的A/D转换器对被测电阻两端的电压进行采样,通过数值比对,自动控制各个电阻档位继电器的开关,实现量程自动切换功能。用键盘输入筛选电阻阻值及误差值,通过单片机对步进电机的控制来实现电位器阻值的变化,由LCD12864显示测量数据和变化的曲线,符合筛选条件时,系统发出声音提示,实现准确、快速筛选电阻。     

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.