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钱冠龙 《机械设计与制造工程》2001,30(1):23-25
从提高钢筋挤压连接设备工作效率的几条途径(即提高泵站输出流量、加大挤压钳输出力、实现设备自动控制等)入手,围绕80MPa超高压液压系统提高流量、加大元件尺寸后引出的系统发热、密封效果差、元件寿命低、故障率高等技术难题,阐述了在解决这些难题时大流量、大吨位高效钢筋挤压连接设备其结构、材料、加工技术等方面的设计思想和技术措施。该设备产品已在国内外数百个大中型工程建设项目中得到应用,效果良好。 相似文献
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现代气动技术理论与实践第一讲:气动元件的流量特性 总被引:1,自引:0,他引:1
0前言 设计气动系统时,准确地把握电磁阀、调速阀等元件的流量特性非常重要。流量特性表示元件的空气流通能力,将直接影响气动系统的动特性。在元件选型时如弄错流量特性.将可能导致气动执行元件达不到预期的输出力或输出速度。 相似文献
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针对大流量高速开关阀(流量450L/min、关闭时间8ms)阀芯冲击和振荡问题,设计了阀芯挤压油膜缓冲器,利用挤压油膜的非线性输出力和非线性阻尼对阀芯末端行程进行缓冲,在不影响阀关闭时间的情况下,大大减小阀芯冲击,消除阀芯振荡,使阀平稳关闭,从而显著提高阀的使用寿命、可靠性和密封性能。仿真和实验结果表明:当油膜厚度约为0.1mm时,缓冲器具有最佳缓冲效果,阀芯关闭过程接近理想状态。该阀流量大、响应速度快,阀芯缓冲方案新颖,在大功率、快速性场合具有重要应用价值。研究成果对其他液压元件的设计研究具有理论指导和借鉴价值。 相似文献
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在液压传动的机械设备中,有的液压执行元件在一个不长的工作周期內要求有一个或几个高压大流量的输出?杂谡庵止た?如何从技术经济指标的角度,特别是节能的意义上满足系统峰值流量和压力的要求,这是设计人员必须认真考虑的问题。解决这一问题的方法是泵、蓄能器联合供油。当系统所需的流量较小时,泵输出的油液一部分输向系统,而多余的部分输向蓄能器,把液压能储存起来;而在液压执行元件需要高压大流量的时候,蓄能器和泵一起向系统输油,满足执行元件的要求。这样泵的传动功率就可减少,对节省能耗和减少投资都有好处。 相似文献
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钢筋连接套内锥螺纹加工装置桂林电子工业学院(541004)伍世荣钢筋锥螺纹连接技术是近年来应用日趋广泛的一种新的钢筋连接技术,其连接元件是一个两端带内锥螺纹的连接套。钢筋规格不同,其连接套的尺寸也不同,图1所示为钢筋规格为28mm的连接套。连接套筒... 相似文献
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1 引言在我国超高压液压压力是以高于 32MPa作为划分界限的。超高压液压技术对密封的要求极为严格 ,这是因为在间隙相同的条件下 ,超高压力下的泄漏量比常用压力大几倍甚至几十倍。另外 ,由于超高压设备的流量较小 ,即便是微量的泄漏也会对液压系统升压和保压性能产生很大的影响 ,同时 ,密封元件的性能对超高压系统的安全使用关系重大。在超高压力下 ,密封元件受到强烈的挤压 ,易产生塑性流变。这要求密封元件具有较高的强度。对普通的密封圈 ,理论上已不适合超高压系统密封的要求 ,但目前在使用中 ,国内尚无定型的超高压密封元件 ,只有根… 相似文献
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分析一种感应电机直接转矩控制中转子磁链的观测方法,并对转子磁链及磁链转差进行数学建模分析,在此基础上估算出电机转速.通过仿真结果可以看出,这种方法能够提高低速观测精度,增强系统鲁棒性,受电机参数变化影响不大,算法简单直观,便于实现. 相似文献
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Energy efficiency improvement of electrical motor drives has recently become a very interesting subject. Several methods have been proposed in the literature to improve the efficiency of permanent magnet synchronous machine (PMSM) with sinusoidal back-EMF. These methods are not precise and appropriate for brushless DC machine (BLDCM) with trapezoidal back-EMF. As a unique solution, this work introduces a flux controlled based loss minimization algorithm suitable for BLDCM that considers iron loss as well as influence of back-EMF harmonics; consequently promotes efficiency of machine. In this regard, the loss model of PMSM is extended based on multiple reference frame analysis to include back-EMF harmonics of BLDCM. As an advantage, proposed modified loss model does not require any additional data about the dimensions of machine that makes it suitable for industrial motor drive applications. The Proposed loss model is validated through experimental tests in different operating conditions. Afterward, by applying direct torque and indirect flux control of BLDCM as the control technique, d-axis current in the rotor reference frame is controlled to reduce the air gap flux and consequently iron loss of the machine. Finally, a procedure is presented to determine the optimum d-axis current which maximizes the efficiency. Effectiveness of proposed control system is evaluated using simulation results in MATLAB/Simulink and experimental results on a practical prototype. It is indicated that depending on the operating conditions, about 2% to 11% of efficiency improvement would be achieved in the proposed method. 相似文献
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针对新型往复式定子永磁的直线电机,首先简要介绍了其基本结构,然后从定子绕组磁链入手,详细地讨论了该类型直线电机的运行原理以及包括控制电流在内的各种变量的波形等,并利用机电能量转换的基本原理分析了其电磁力的产生机制。为了说明这种类型电机的特点,采用类比的方法利用Flux-MMF图进一步讨论了其与目前流行的各种类型机电一体化电机如开关磁阻电机、双凸永磁电机以及无刷直流电机的异同,得出了许多重要结论。在此基础上,对这种往复式定子永磁的直线电机的动态数学模型进行了探讨。最后,给出了这种类型电机的样机并设计了相应的驱动器系统,给出了相应的实验波形和实验结果。 相似文献
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人字齿轴辊自动堆焊机 总被引:1,自引:0,他引:1
目前能实现自动化堆焊设备少,且使用效果差、劳动强度大、能耗高,针对轴辊齿面硬度高、耐磨性好、耐疲劳性强和特殊的齿形要求,提出了基于堆焊技术和PLC技术人字齿轴辊自动堆焊机的设计思路,阐述了人字轴辊自动堆焊机的整体设计,介绍了自动堆焊机焊接系统、送丝装置、焊剂输送系统和工件回转机构等设计与制作过程。实践表明,该自动堆焊机具有运行稳定、加工的齿形多样、堆焊层质量高、能实现补焊和修复特点,并实现轴辊循环再利用。 相似文献
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Diamagnetic loop (DL), which consists of two poloidal loops inside the vacuum vessel, is used to measure the diamagnetic flux during a plasma discharge in the Korea Superconducting Tokamak Advanced Research (KSTAR) machine. The vacuum fluxes in the DL signal can be compensated up to 0.1 mWb by using the coefficients, which are obtained from experimental investigations, in the vacuum flux measurements during vacuum shots under same operational conditions of magnetic coils for plasma experiment in the KSTAR machine. The maximum error in the diamagnetic flux measurement due to the errors of the coefficients was estimated as ~0.22 mWb. From the diamagnetic flux measurements for the ohmically heated circular plasmas in the KSTAR machine, the stored energy agrees well with the estimated kinetic energy within the discrepancy of 25%. When the electron cyclotron heating, the neutral beam injection, and the ion cyclotron resonance heating are added to the ohmically heated limiter plasmas, the additional heating effects can be clearly observed from the increase of the stored energy evaluated in the DL measurement. 相似文献
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无速度传感器矢量控制的速度推算 总被引:1,自引:0,他引:1
通过测量定子每相的电压和电流值,推测出速度是实现无速度传感器矢量控制的一条途径,其中磁链的精度是速度推算的重要环节。通过构造全维状态观测器来提高转子电流和磁链的推算精度,同时使用速度自适应辩识和Rs自适应辩识来进一步提高电流和磁链的推算精度,并完成速度推算,从而可以对感应电机实现高性能的矢量控制。 相似文献
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Abdelkarim Ammar Abdelhamid Benakcha Amor Bourek 《The International Journal of Advanced Manufacturing Technology》2017,91(5-8):1631-1641
This paper presents an improved direct torque control (DTC) method for induction motor (IM) drive. The main drawback of the conventional DTC is the use of hysteresis comparators which leads to high torque and flux ripples. The improvement in this paper includes using the space vector modulation to preserve a constant switching frequency and to reduce totally flux and torque ripples. Besides, the torque and stator flux regulation will be done based on model reference adaptive control (MRAC) strategy to ensure a robust control against external disturbance and less sensitivity from machine parameter variation unlike the conventional proportional-integral (PI) controllers. Furthermore, a design of an adaptive observer based on Lyapunov stability is presented for speed/flux and load torque estimation. The observer can improve the control performances and decrease the cost and increase reliability of the global control system by reducing the number of sensors. The proposed strategy will be examined under simulation tests using Matlab/Simulink and experimental implementation with real-time interface (RTI) based on dSpace 1104 board. 相似文献