空间大角度刚性扭转导引的改进设计

为改善扭转导引的动力学性能,提高无链供弹系统的稳定性,对某供输弹系统的刚性大角度扭转导引进 行分析与改进。通过分析扭转导引的结构及现有问题,改进扭转导引的固定轴线和扭转角随轴线的变化规律,并建 立扭转导引的3 维模型,通过多体动力学仿真软件建立扭转导引的虚拟样机模型,仿真分析其在300 发/min 射频下 的运动规律。仿真结果表明：弹在改进后的扭转导引中的运动更稳定顺畅,验证了模型的准确性。     

钢管填充混凝土对内外法兰节点抗弯承载力特性影响研究

特大型钢管结构(如大跨越输电铁塔等)主材内力及直径均非常大,钢管接长后采用传统刚性法兰连接不能满足承载力要求且不经济。在钢管内外侧均设置连接螺栓,形成钢管内外法兰。并针对钢管填充混凝土与否,设计并制作钢管内外法兰及钢管混凝土内外法兰试件,开展2种内外法兰抗弯承载力性能试验、有限元模拟分析和抗弯旋转轴计算理论研究,考察其承载力特性、传力机理及旋转轴位置。分析加载过程中连接螺栓、钢管及混凝土应变的发展情况,得到法兰啮合面旋转轴位置及内外螺栓内力分布规律。研究表明,钢管混凝土内外法兰受弯时可以避免钢管发生局部屈曲,提高了法兰节点整体抗弯刚度;且随着荷载的增大,法兰板张开,混凝土开裂,螺栓发生颈缩破坏。钢管内外法兰及钢管混凝土内外法兰抗弯承载力设计时,连接螺栓旋转轴位置分别可取距离管中心0.6R,0.8R(R为钢管半径)。     

椭圆轴零件的工艺分析及夹具设计

通过典型的数控车零件的工艺分析,引出椭圆轴加工工艺分析、斜椭圆宏程序的编制及夹具的结构设计,充分考虑每一道工序的装夹问题,制定合理的加工工艺,达到便于装夹、便于加工、便于测量和保质保量的目的。     

整车验证模型五轴数控加工编程工艺规范研究

探讨了整车验证模型五轴数控加工工艺要点;基于先进CAM软件对整车验证模型五轴数控加工刀具路径编程工艺进行研究;提出了对该模型的五轴数控加工编程工艺规范化思路以及具体实施方案;基于Power MILL系统、易语言编程系统开发了整车验证模型五轴数控加工编程工艺模版库、刀具库和机床库。     

基于受力性能优化的大型钢筋混凝土拱桥设计实践

结合包头市北梁腾空区外环路东河大桥工程设计实践,为优化桥体受力性能,有效提升上、下部结构经济合理性,对多跨不对称钢筋混凝土连拱桥主要设计要点进行研究。主要包括拱上建筑造型优化设计、拱轴线形式优化设计、拱脚构造优化设计、拱上建筑变形缝设计等拱桥构造优化设计和拱桥安全施工流程设计。为同类工程提供参考、借鉴。     

浅谈郭公庄水厂的工艺设计及优化

郭公庄水厂是南水北调水进京后第一座接纳南水并处理南水的新建给水处理厂。郭公庄水厂采用澄清、臭氧—活性炭吸附、超滤膜过滤、紫外线加次氯酸钠消毒的处理工艺。通过对机械加速澄清池布置形式、设备选型、结构做法的优化设计,以及对活性炭吸附池改为炭砂滤池的工艺设计优化,使得该水厂在适应南水北调水源、工艺单元互补、方便运行管理、保证施工质量等方面有了进一步的提高,进而满足首都供水的安全和出水水质要求。     

Calculating the medial axis of a CAD model by multi-CPU based parallel computation

Computational efficiency is still a great challenge for the generation of the Medial Axis (MA) for complicated CAD models. Current research mainly focuses on CPU-based MA generation methods. However, most of the methods emphasize using a single CPU. The highly-efficient methods based on parallel computing are still missing. In this study, a parallel method based on multi-CPU is proposed for the efficient MA generation of CAD models using distance dilation. By dividing the whole model into several parts for which MAs are calculated in parallel and then combined, computational efficiency can be greatly improved in theory and the computation time can be reduced nearly K times if K CPUs are used. Firstly, an adaptive division method is proposed to divide the voxelized model into blocks which have nearly the same number of voxels to balance the computational burden. Secondly, the local Euclidean Distance Transform (EDT) is calculated for each block based on the existing distance dilation method. Thirdly, the complete inter-dilation method is proposed to compute the influence between different blocks to get a global EDT for each block. Finally, each block generates a sub-MA separately and then all the generated MAs are combined to obtain the final MA. The last three processes can be efficiently conducted in parallel by using multiple CPUs. Several groups of experiments are conducted which demonstrate the good performance of the proposed methods in terms of efficiency.     

Prediction and identification of rotary axes error of non-orthogonal five-axis machine tool

This paper proposes an efficient and automated scheme to predict and identify the position and motion errors of rotary axes on a non-orthogonal five-axis machining centre using the double ball bar (DBB) system. Based on the Denavit-Hartenberg theory, a motion deviations model for the tilting rotary axis B and rotary C of a non-orthogonal five-axis NC machine tool is established, which considers tilting rotary axis B and rotary C static deviations and dynamic deviations that total 24. After analysing the mathematical expression of the motion deviations model, the QC20 double ball bar (DBB) from the Renishaw Company is used to measure and identify the motion errors of rotary axes B and C, and a measurement scheme is designed. With the measured results, the 24 geometric deviations of rotary axes B and C can be identified intuitively and efficiently. This method provides a reference for the error identification of the non-orthogonal five-axis NC machine tool.     

LSMAT Least Squares Medial Axis Transform

The medial axis transform has applications in numerous fields including visualization, computer graphics, and computer vision. Unfortunately, traditional medial axis transformations are usually brittle in the presence of outliers, perturbations and/or noise along the boundary of objects. To overcome this limitation, we introduce a new formulation of the medial axis transform which is naturally robust in the presence of these artefacts. Unlike previous work which has approached the medial axis from a computational geometry angle, we consider it from a numerical optimization perspective. In this work, we follow the definition of the medial axis transform as ‘the set of maximally inscribed spheres’. We show how this definition can be formulated as a least squares relaxation where the transform is obtained by minimizing a continuous optimization problem. The proposed approach is inherently parallelizable by performing independent optimization of each sphere using Gauss–Newton, and its least‐squares form allows it to be significantly more robust compared to traditional computational geometry approaches. Extensive experiments on 2D and 3D objects demonstrate that our method provides superior results to the state of the art on both synthetic and real‐data.     

迭代最近点算法的改进策略

迭代最近点（Iterative Closest Point, ICP）算法是一种最为常见的点云配准方法，虽然配准精度高，但收敛速度慢，对含噪声、覆盖率较低点云的配准效果不佳。鉴于此，本文提出3种ICP算法的改进方法。针对含噪声的点云，采用概率ICP算法来抑制噪声点对配准结果的影响，提高配准精度；为了提高点云配准速度，采用坐标ICP算法实现点云的快速配准；针对低覆盖率点云，采用盒子ICP算法实现配准，可以大大提高配准精度和速度。通过兔子点云配准实验表明，3种改进的ICP算法在点云配准精度和速度方面都有很大程度的提高，均为有效的点云配准方法。