基于格网模型的等高线算法

提出了一种通过格网模型生成等高线的方法.通过计算规则格网模型中顶点的符号来确定等高线与格网中棱的交点数目,根据交点的数目和格网中心点的符号确定等高线的跟踪方向,对等高线上的点用样条曲线连接可得等高线.实验结果表明,此算法正确、有效,运行效率高.     

降雨分析系统的设计与算法

等值线是反映空间地理信息数据关系的最重要的表现方式之一,但编程实现等值线的绘制并用其进行GIS软件的二次开发却并不容易。在实际开发降雨分析系统的基础上介绍了在数据可视化和地理信息系统中非常重要的等值线绘制和轮廓图填充算法,并且给出了基于动态链接库和XML技术的模块化系统整体架构。实际的绘制效果与计算速度可与美国GoldenSoft公司的著名软件Surfer相媲美。降雨数据来源包括以数据库和文件存储的一切实测、遥感数据。该系统已在杭州、温州、上虞、金华、台州等多个地市的防汛抗旱部门投入使用,改变了原先等值线主要由手工绘制的情况。本系统可以同样用于等高线的绘制。     

Application of self-tuning fuzzy controller for a Cartesian manipulator on unknown contours

Owing to the relative difficulty in achieving contour tracking on 3D objects, this study presents a novel compliant motion controller by applying the self-tuning fuzzy control to have a Cartesian manipulator implement contour tracking on unknown contours. A data fitting method is also developed to reduce the noise errors of the measurement. Moreover, the radius compensating method is used to correct the measured data. The Cartesian manipulator is tested and calibrated beforehand. Results in this study demonstrate the feasibility of the control strategy proposed herein.     

数控伺服系统跟踪及轮廓误差分析

分析了数控加工中伺服系统跟踪误差和轮廓误差的计算方法,详细讨论了双轴数控加工中轴跟踪误差和轮廓误差之间的关系。指出了多轴加工中轮廓误差建模和误差控制方法的理论意义和应用价值。     

Development of High Strength and Toughness Non-Heated Al–Mg–Si Alloys for High-Pressure Die-Casting

Based on the 3 factors and 3 levels orthogonal experiment method, compositional effects of Mg, Si, and Ti addition on the microstructures, tensile properties, and fracture behaviors of the high-pressure die-casting Al-x Mg-y Si-z Ti alloys have been investigated. The analysis of variance shows that both Mg and Si apparently infl uence the tensile properties of the alloys, while Ti does not. The tensile mechanical properties are comprehensively infl uenced by the amount of eutectic phase(α-Al + Mg_2Si), the average grain size, and the content of Mg dissolved into α-Al matrix. The optimized alloy is Al-7.49 Mg-3.08 Si-0.01 Ti(wt%), which exhibits tensile yield strength of 219 MPa, ultimate tensile strength of 401 MPa, and elongation of 10.5%. Furthermore, contour maps, showing the relationship among compositions, microstructure characteristics, and the tensile properties are constructed, which provide guidelines for developing high strength and toughness Al–Mg–Si–Ti alloys for high-pressure die-casting.     

火炮身管膛线加工的轮廓一致性保证技术

通过对火炮身管膛线加工过程的分析,提出膛线自动加工控制过程中膛线轨迹一致性保证技术,包括膛线方程数据细分归一处理方法、运动过程换向点校验修正技术、动态过程的轨迹验证。从定点采样过程数据看,整个过程Z／C联动轨迹的轮廓一致性能得到很好的保证,确保多次循环下轨迹的绝对重复。     

基于双模同步预测的机械臂末端轮廓精确跟踪控制

为减小机械臂末端在进行轨迹跟踪运动时的轮廓误差,提出一种机械臂轮廓误差同步预测控制策略。该策略将操作空间轮廓误差映射到关节空间,从而定义机械臂各关节的同步行为,有效减小了末端轮廓误差,提高了机械臂各关节的运动协调性。为解决常规预测控制器不能保证系统稳定的问题,提出双模同步预测控制方法,通过在预测时域外切换到局部控制率来保证控制器的稳定性。实验结果表明:所设计的控制器能有效减小末端轮廓误差并使关节输出力矩更加平稳。     

Distortion and residual stresses in electron beam-welded hydroelectric turbine materials

Heavy-section assembly of hydroelectric turbine runner materials using single-pass, autogenous EBW was demonstrated to penetrate a 90-mm-thick butt joint. The welding-induced distortions and residual stresses were characterised to understand the impact of the materials and process conditions (e.g. preheating and/or PWHT). Using 3D optical measurements, the angular distortions of EB-welded UNS S41500 and CA6NM steels were determined to be 0.13° and 0.38°, respectively. The longitudinal residual stresses, measured through the contour method, had a M-shaped distribution throughout the thickness with minimum (～?500?MPa) compressive stresses in the FZ and maximum (～600?MPa) tensile stresses in the HAZ. After PWHT, the tensile and compressive stresses reduced to ～100?MPa.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

A systematic approach to design high-performance feed drive systems

A systematic design methodology for the mechatronic system composed of mechanical and control subsystems is proposed to design high-speed and high-precision feed drive systems. Strict mathematical modeling and identification processes of the subsystems are performed in this paper. Parametric studies and circular motion experiments in the x–y table are conducted to investigate the influence of interactions on the performance of feed drive systems. Based on analyses of the system performance according to design and operating parameters, a nonlinear constrained optimization problem including the relevant subsystem parameters of the feed drive system is formulated. The multi-objective optimization procedure and normalization technique are introduced in the design process. A Pareto optimum solution set is applied to investigate the relationships between objective functions. The effectiveness of the proposed design methodology is verified through numerical case studies.