Design and analysis of turnover platform for welding robot北大核心CSCD

A turnover platform for welding robot was designed for the application of welding robot with lower accuracy requirement, which was of low cost and higher position accuracy. In this turnover platform, the pneumatic motor was used as the power output, and the indexing mechanism with high accuracy was the transmission system with high transmitting ratio based on worm and wheel. The position information was acquired by using the photoelectric encoder, and the turnover motion with high accuracy was realized through the closed-loop controller. Simulation results showed that the maximum speed of the welding platform approached 14 r/min, and the platform could meet the requirements of most welding products. Such a turnover platform can offer the application program of the welding robot with low cost for the middle and low level products, and reduce the cost of welding robot and improve welding productivity.     

设计的进化与价值

<正>一、前言设计是人们对于装备制造、工程建设、经营管理和服务创新的创意设想、计划和计算,是将信息、知识和技术转化、集成为整体解决方案并实现价值的发明创造,是一切有目标创新实践的先导、准备与关键环节。设计决定着创新创造的方向、目标、路径和价值。设计创新引领推动人类社会的文明和进步,设计的知识技术、价值理念、人才团队、方式环境也随着人类文明进化而发展。从旧石器时代起,我们的祖先已利用天然材料,朦胧地构想制作     

La<Subscript>1−x</Subscript>Ag<Subscript>x</Subscript>FeO<Subscript>3</Subscript>/halloysites nanocomposite with enhanced visible light photocatalytic performance

La_1?xAg_xFeO₃/halloysites nanotubes (HNTs) nanocomposite was synthesized by sol–gel method. It was characterized by X-ray diffraction, transmission electron microscope, Fourier transform infrared spectroscopy and UV–visible diffused reflectance spectroscopy measurements. The photo-activity of the La_1?xAg_xFeO₃/HNTs nanocomposite was evaluated via degradation of methylene blue (MB) under visible-light irradiation. The results showed that the HNTs with unique pore structure favored the adsorption of organic molecules. Adequate Ag⁺ doping improved the absorption ability for visible light. The La_0.95Ag_0.05FeO₃/HNTs demonstrated the best photocatalytic performance, which achieved as high as 99 % for MB degradation exposed 2 h irradiation. However,further increasing of Ag⁺ doping gradually reduced the photocatalytic activity. The nanocomposite catalyst showed outstanding recyclability after eight cycles which still remained up to 90 %.     

Precise identification of moving vehicular parameters based on improved glowworm swarm optimization algorithm

This paper proposes an indirect method for the identification of moving vehicular parameters using the dynamic responses of the vehicle. The moving vehicle is modelled as 2-DOF system with 5 parameters and 4-DOF system with 12 parameters, respectively. Finite element method is used to establish the equation of the coupled bridge–vehicle system. The dynamic responses of the system are calculated by Newmark direct integration method. The parameter identification problem is transformed into an optimization problem by minimizing errors between the calculated dynamic responses of the moving vehicle and those of the simulated measured responses. Glowworm swarm optimization algorithm (GSO) is used to solve the objective function of the optimization problem. A local search method is introduced into the movement phase of GSO to enhance the accuracy and convergence rate of the algorithm. Several test cases are carried out to verify the efficiency of the proposed method and the results show that the vehicular parameters can be identified precisely with the present method and it is not sensitive to artificial measurement noise.     

基于Opencv的絮体颗粒跟踪与沉速测量系统研究

针对饮用水处理过程混凝剂投加量对处理结果的直接影响,提出了一个以絮体的沉降速度(作为主控,等效粒径、数量等参数作为辅控的多源数据融合的混凝剂投药模型。本文基于Open CV机器视觉库,以VS2010为平台,采用C++语言,编写絮体检测和沉降速度测量在线系统的软件,实现了絮体各个参数和沉降速度的实时监测。     

基于Fluent的圆柱齿轮流量计的密封性仿真分析

通过对圆柱齿轮流量计进行二维简化建模,用Fluent仿真软件的ICEM CFD模块进行网格划分,利用Fluent仿真软件对圆柱齿轮流量计进行了计算和密封性的仿真分析,得出了其速度矢量分布图,并且给出了各泄漏量的计算公式和每种泄漏所占泄漏总量的百分比,即为以后的整个流量计的设计提供理论依据。,提高流量计的寿命具有重要意义。同时还省去了大量的人工计算过程,极大地加快了计算速度。     

Composite bending-dominated hollow nanolattices: A stiff,cyclable mechanical metamaterial

Manufacturing ultralight and mechanical reliable materials has been a long-time challenge. Ceramic-based mechanical metamaterials provide significant opportunities to reverse their brittle nature and unstable mechanical properties and have great potential as strong, ultralight, and ultrastiff materials. However, the failure of ceramics nanolattice and degradation of strength/modulus with decreasing density are caused by buckling of the struts and failure of the nodes within the nanolattices, especially during cyclic loading. Here, we explore a new class of 3D ceramic-based metamaterials with a high strength–density ratio, stiffness, recoverability, cyclability, and optimal scaling factor. Deformation mode of the fabricated nanolattices has been engineered through the unique material design and architecture tailoring. Bending-dominated hollow nanolattice (B-H-Lattice) structure is employed to take advantages of its flexibility, while a few nanometers of carbonized mussel-inspired bio-polymer (C-PDA) is coherently deposited on ceramics’ nanolayer to enable non-buckling struts and bendable nodes during deformation, resulting in reliable mechanical properties and outperforming the current bending-dominated lattices (B-Lattices) and carbon-based cellulose materials. Meanwhile, the structure has comparable stiffness to stretching-dominated lattices (S-Lattices) while with better cyclability and reliability. The B-H-Lattices exhibit high specific stiffness (>10⁶?Pa·kg^?1·m^?3), low-density (～30?kg/m³), buckling-free recovery at 55% strain, and stable cyclic loading behavior under up to 15% strain. As one of the B-Lattices, the modulus scaling factor reaches 1.27, which is lowest among current B-Lattices. This study suggests that non-buckling behavior and reliable nodes are the key factors that contribute to the outstanding mechanical performance of nanolattice materials. A new concept of engineering the internal deformation behavior of mechanical metamaterial is provided to optimize their mechanical properties in real service conditions.     

基于数字兆欧表自动切换档位的研究与实现

随着电力、电气设备的日益复杂化,对于其安全性能也有了更高的要求,数字兆欧表作为测量绝缘阻值的重要工具,已在工业领域中广泛应用;为了满足测量精度以及兆欧表的可靠性,通过基于S3C2440的嵌入式平台,提出了一种基于数字兆欧表的自动切换档位的实现方案,以达到更加精确的测量;此方案通过判断采集到的电压值选择相应的采样电阻来实现,并结合硬件平台和软件设计,分别介绍了驱动程序和应用程序的编写与测试,并很好地应用到了实际电路中;经测试,能够达到预期的效果,测量精度高,测量误差控制在±2%。