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Multi-hop communications are becoming more and more important due to its flexibility and potential to improve communication coverage and quality. In this paper, we discuss the robust transceiver optimization for multi-hop amplify-and-forward multiple-input multiple-output(MIMO) orthogonal frequency division multiplexing(OFDM) systems. In general, we consider a three-dimensional robust beamforming design, i.e.,frequency, spatial and relay domains. With inevitable channel estimation errors, in our work both weighted mean square error(MSE) minimization and minimizing maximum MSE are adopted as the performance metrics to design robust transceivers. Following the Bayesian robust philosophy, a robust transceiver design is proposed. The design is based on convex optimization, and the involved optimization variables are optimized alternatively. The proposed transceiver optimization algorithms can be applied to the network with arbitrary hops, arbitrary antennas and arbitrary subcarriers. At the end of this paper, the performance advantages of the propose design have been assessed by the numerical results. 相似文献
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WANG Wei YUN Chao ZHANG Ling GAO Zhihui Robotics Institute Beihang University Beijing China State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong University Xi'an China 《机械工程学报(英文版)》2011,(4):647-655
Off-line programming (OLP) system becomes one of the most important programming modules for the robotic belt grinding process, however there lacks research on increasing the grinding dexterous space depending on the OLP system. A new type of grinding robot and a novel robotic belt grinding workcell are forwarded, and their features are briefly introduced. An open and object-oriented off-line programming system is developed for this robotic belt grinding system. The parameters of the trimmed surface are read from the initial graphics exchange specification (IGES) file of the CAD model of the workpiece. The deBoor-Cox basis function is used to sample the grinding target with local contact frame on the workpiece. The numerical formula of inverse kinematics is set up based on Newton’s iterative procedure, to calculate the grinding robot configurations corresponding to the grinding targets. After the grinding path is obtained, the OLP system turns to be more effective than the teach-by-showing system. In order to improve the grinding workspace, an optimization algorithm for dynamic tool frame is proposed and performed on the special robotic belt grinding system. The initial tool frame and the interval of neighboring tool frames are defined as the preparation of the algorithm. An optimized tool local frame can be selected to grind the complex surface for a maximum dexterity index of the robot. Under the optimization algorithm, a simulation of grinding a vane is included and comparison of grinding workspace is done before and after the tool frame optimization. By the algorithm, the grinding workspace can be enlarged. Moreover the dynamic tool frame can be considered to add one degree-of-freedom to the grinding kinematical chain, which provides the theoretical support for the improvement of robotic dexterity for the complex surface grinding. 相似文献
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碳纤维复合材料与铝合金电偶腐蚀行为研究 总被引:4,自引:4,他引:4
采用全浸腐蚀、腐蚀失重测量、电偶电位和电偶腐蚀电流等试验研究方法.将T300/5222、T300/5405和T300/QY8911三种碳纤维复合材料与LY12CZ、71304和2D70三种铝合金相互偶接,研究由于电偶腐蚀的存在,对铝合金及复合材料腐蚀行为的影响,用SEM方法观察其腐蚀形貌.结果表明,碳纤维复合材料与铝合金的电偶腐蚀作用,促进了铝合金表面点蚀的形成与扩展,电偶作用使铝合金腐蚀的溶解速率明显加快,而与铝合金偶接的复合材料表面形貌基本无变化,复合材料与铝合金之间电偶腐蚀电流较大,二者之间电偶腐蚀十分严重. 相似文献
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针对野外低压架空输电线路开展了过电压防护试验研究。通过一次典型的多回击自然闪电引起的过电压并结合闪电定位资料,对输电线路不同位置的入户端及采集器前端的过电压大小、采集器前端电涌保护器(surge protective device,SPD)残压特性及入户端L线过电压和闪电回击电流之间的关系进行了分析和探讨。通过分析发现:近距离的闪电能在架空输电线路上产生几kV的感应过电压,过电压持续时间平均约1.0 ms,采集器前端安装SPD动作后,较远的入户端过电压波形也会受其影响;采集器前端SPD动作残压持续时间平均约218μs,比标准8/20μs冲击波试验持续时间长;入户端感应过电压、回击电流与距离有很好的线性拟合关系。 相似文献
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