共查询到20条相似文献,搜索用时 15 毫秒
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提出了一种提高扫略曲面三坐标加工速度的优化方法;在曲面加工中,经常使用比较昂贵的商业CAD/CAM软件来生成加工程序,对刀具位置和路径规划进行大量的计算;由于这些商业软件都基于一种比较可靠的算法,所以在功能上都具有相似的功能和效率;也就是说,现在使用的大多数的CAD/CAM系统,都是基于零件的几何特征来加工的;文中提出了主要集中在提出一种基于被加工零件精度自由曲面刀具路径生成方法,推导出前进步距函数,在给定加工误差和没有损失加工精度的情况下,计算出最大的CC(刀具接触点)点间的距离,来减少生成的CC点,减少加工时间,提高了加工效率。 相似文献
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本文给出时域辨识与频域辨识相互补充的一些事实。用频域准测对时域辨识作比较,可弄清不同时域辨识的频域意义。用时域辨识可获得传递函数估计的有意义的性质。本文还包括这些性质在最优输入设计上的应用。 相似文献
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国产品牌在可靠性和生产工艺上正在迎头赶上,其最大的优势是适合中国国情和用户的需要.可以进行特殊设计,用户界面友好,操作方便,价格便宜。最主要的是良好的售前售后服务和备品备件的提供,以及操作维护人员的培训工作,更是国外品牌的产品所无法比拟的。 相似文献
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<正>1前言通常,我们把用来驱动1kV以上交流电动机的中、大容量变频器称为高压变频器。按照国际惯例和我国国家标准,当供电电压大于或等于10kV时称高压,小于10kV时称中压。因此,相应额定电压1~10kV的变频器应分别称为中压变频器和高压变频器。但考虑到在这一电压范围内的变频器有着共同的特 相似文献
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本文总结了交-交变频调速和交流调压调速的优缺点。在不需增加任何硬件设备的情况下,将交一次变频调速和交流调压调速有机结合,用于分析煤矿绞车的运行特性,可以很好地实现煤矿绞车的起动、等速、减速、爬行等运行方式,弥补了有级变频时各个机械特性过渡点的大幅度跳变,实现了电磁物理量的平滑控制及机械特性的自然过渡。 相似文献
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代杰 《自动化与信息工程》2009,30(3):46-48
电梯作为现代高层建筑的垂直交通工具,得到了快速发展,其拖动技术已经发展到了调频调压调速,其逻辑控制也由PLC代替原来的继电器控制。文章在已有的通用变频器的基础上,采用PLC对电梯进行控制,通过合理的选择和设计,提高了电梯的控制水平,并改善了电梯运行的舒适感,使电梯达到了较为理想的控制效果。 相似文献
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通过对电机动态特性的研究和测试,介绍了采用智能采样环节的智能逆模控制器的工作原理,给出了它和一般PID调节器动态特性曲线的比较结果。 相似文献
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We analyze the asymptotic rates of convergence of Chebyshev, Legendre and Jacobi polynomials. One complication is that there are many reasonable measures of optimality as enumerated here. Another is that there are at least three exceptions to the general principle that Chebyshev polynomials give the fastest rate of convergence from the larger family of Jacobi polynomials. When $f(x)$ is singular at one or both endpoints, all Gegenbauer polynomials (including Legendre and Chebyshev) converge equally fast at the endpoints, but Gegenbauer polynomials converge more rapidly on the interior with increasing order $m$ . For functions on the surface of the sphere, associated Legendre functions, which are proportional to Gegenbauer polynomials, are best for the latitudinal dependence. Similarly, for functions on the unit disk, Zernike polynomials, which are Jacobi polynomials in radius, are superior in rate-of-convergence to a Chebyshev–Fourier series. It is true, as was conjectured by Lanczos 60 years ago, that excluding these exceptions, the Chebyshev coefficients $a_{n}$ usually decrease faster than the Legendre coefficients $b_{n}$ by a factor of $\sqrt{n}$ . We calculate the proportionality constant for a few examples and restrictive classes of functions. The more precise claim that $b_{n} \sim \sqrt{\pi /2} \sqrt{n} a_{n}$ , made by Lanczos and later Fox and Parker, is true only for rather special functions. However, individual terms in the large $n$ asymptotics of Chebyshev and Legendre coefficients usually do display this proportionality. 相似文献
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《Ergonomics》2012,55(8):627-635
Four groups of postmen were trained to type alpha-numeric code material using a conventional typewriter keyboard. Training was based on sessions lasting for one or two hours occurring once or twice per day. Learning was most efficient in the group given one session of one hour per day, and least efficient in the group trained for two 2-hour sessions. Retention was tested after one, three or nine months, and indicated a loss in speed of about 30%. Again the group trained for two daily sessions of two hours performed most poorly. It is suggested that where operationally feasible, keyboard training should be distributed over time rather than massed. 相似文献
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计算机技术与PLC控制在机电实训装置中的应用 总被引:7,自引:0,他引:7
今天的工业控制,学习和掌握PLC控制技术和变频调速技术是必须的。我们研制的这套PLC综合控制实训装置,既能进行大量的开关自动控制,又能进行模拟量的变频调速闭环自动控制,满足了工程类学生的综合设计应用和创新研究能力的培养,增强了人才适应社会的能力。 相似文献
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In everyday life, people use their mobile phones on-the-go with different walking speeds and with different touch input techniques. Unfortunately, much of the published research in mobile interaction does not quantify the influence of these variables. In this article, we analyze the influence of walking speed, gait pattern, and input techniques on commonly used performance parameters like error rate, accuracy, and tapping speed, and we compare the results to the static condition. We examine the influence of these factors on the machine learned offset model used to correct user input, and we make design recommendations. The results show that all performance parameters degraded when the subject started to move, for all input techniques. Index finger pointing techniques demonstrated overall better performance compared to thumb-pointing techniques. The influence of gait phase on tap event likelihood and accuracy was demonstrated for all input techniques and all walking speeds. Finally, it was shown that the offset model built on static data did not perform as well as models inferred from dynamic data, which indicates the speed-specific nature of the models. Also, models identified using specific input techniques did not perform well when tested in other conditions, demonstrating the limited validity of offset models to a particular input technique. The model was therefore calibrated using data recorded with the appropriate input technique, at 75% of preferred walking speed, which is the speed to which users spontaneously slow down when they use a mobile device and which presents a trade-off between accuracy and usability. This led to an increase in accuracy compared to models built on static data. The error rate was reduced between 0.05% and 5.3% for landscape-based methods and between 5.3% and 11.9% for portrait-based methods. 相似文献
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酒精生产废糟液处理过程中的生化工序是治污生产中的一个重要环节.其主要作用是在供氧充足的情况下,生化菌将从上工序(厌氧工序)未处理完的有机物转化成二氧化碳和水.为满足供氧的需要,本工序要求生化池内混合液中溶解氧的含量控制在2~4mg/l范围内,溶解氧的含量则通过鼓风机鼓风量来调节.在风机的鼓风曝气下,经充氧的混合液以一定的流速流经填料,固定在填料上的生物膜直接受到上升气水混合液的强烈搅动,加深生物膜的更新速度,促使微生物快速新陈代谢,提高活性.鼓风量不足,达不到生化菌的生活条件;鼓风量太大,除造成溶解氧过大外,还造成动力消耗浪费. 相似文献
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提出一种新型加权融合算法.首先,根据倍频等长信号间频率的倍数生成倍频修正矩阵,对倍频等长信号频谱进行同频化处理,使之达到同频等长信号频谱的分析效果.然后,针对倍频等长信号的相位不连续问题,设计具有相位连续特性和噪声对消特性的相位补偿矩阵,对同频化的倍频等长信号频谱进行加权融合,使之近似达到与倍频等长信号长度相同的相位连续信号频谱的分析效果.最后,通过谱峰搜索加权融合频谱获得高精度的频率估计值.算法分析与仿真实验表明:与现有方法相比,本算法精度较高,计算量较小,抗噪性强,普适性好. 相似文献
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中文文本的关键词提取是自然语言处理研究中的难点。国内外大部分关键词提取的研究都是基于英文文本的, 但其并不适用于中文文本的关键词提取。已有的针对中文文本的关键词提取算法大多适用于长文本,如何从一段短中文文本中准确地提取出具有实际意义且与此段中文文本的主题密切相关的词或词组是研究的重点。 提出了面向中文文本的基于词或词组长度和频数的关键词提取算法,此算法首先提取文本中出现频数较高的词或词组,再根据这些词或词组的长度以及在文本中出现的频数计算权重,从而筛选出关键词或词组。该算法可以准确地从中文文本中提取出相对重要的词或词组,从而快速、准确地提取此段中文文本的主题。实验结果表明,基于词或词组长度和频数的中文文本关键词提取算法与已有的其他算法相比,可用于处理中文文本,且具有更高的准确性。 相似文献
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基于PLC的电机转速实时监测系统 总被引:1,自引:1,他引:1
本文介绍了一种电机转速计算机实时监测的方法.它利用了PLC及其配套的A/D转换模块进行数据采集和转换,在VB环境下实现计算机与PLC的串行通讯.经过实验,实现了电机转速的数字和曲线显示,给出了应用程序和实验结果. 相似文献
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本文介绍了一种电机转速计算机实时监测的方法。它利用了PLC及其配套的A/D转换模块进行数据采集和转换,在VB环境下实现计算机与PLC的串行通讯。经过实验,实现了电机转速的数字和曲线显示,给出了应用程序和实验结果。 相似文献