Data‐Driven Kinematic Control for Robotic Spatial Augmented Reality System with Loose Kinematic Specifications

We propose a data‐driven kinematic control method for a robotic spatial augmented reality (RSAR) system. We assume a scenario where a robotic device and a projector‐camera unit (PCU) are assembled in an ad hoc manner with loose kinematic specifications, which hinders the application of a conventional kinematic control method based on the exact link and joint specifications. In the proposed method, the kinematic relation between a PCU and joints is represented as a set of B‐spline surfaces based on sample data rather than analytic or differential equations. The sampling process, which automatically records the values of joint angles and the corresponding external parameters of a PCU, is performed as an off‐line process when an RSAR system is installed. In an on‐line process, an external parameter of a PCU at a certain joint configuration, which is directly readable from motors, can be computed by evaluating the pre‐built B‐spline surfaces. We provide details of the proposed method and validate the model through a comparison with an analytic RSAR model with synthetic noises to simulate assembly errors.     

齿轮双球样板的设计方法

为了保证加工的齿轮质量,必须使用齿轮样板对齿轮测量仪器进行校准和检验,样板的精度及可溯源性至关重要.基于双球样板的理论基础,提出了双球样板的设计方法,给出了双球样板关键参数的设计公式,分析了双球样板的材料、结构及精度,并以该设计双球样板的方法为指导,研制了模数为2.268 1 mm、齿数40、压力角20°的双球样板,球体材料选用氧化锆,基座选用花岗石制作.经实验测试检测球的圆度为0.19μm,定心球的圆度为0.21μm,测试球心距为42.943 mm,制造的双球样板可以满足校准仪器的要求.     

Discharge coefficient for vertical sluice gate under submerged condition using contraction and energy loss coefficients

A novel method is suggested for the determination of flow discharge in vertical sluice gates with considerably small bias. First, in order to derive an equation for the discharge coefficient, energy-momentum equations are implemented to define the physical realization of the phenomenon. Afterward, the discharge coefficient is presented in terms of contraction and energy loss coefficients. Subsequently, discharge coefficient, contraction, and energy loss coefficients were determined through an implicit optimization technique on the data. Data analysis illustrated that there is a meaningful power relationship between the contraction and energy loss coefficients. Thereafter, dimensional analysis is performed and an explicit best-fit regression equation is developed for defining the energy loss coefficient. The obtained equations for contraction and energy loss coefficients were then used in the computation of the discharge coefficient and determination of the flow discharge in the vertical sluice gate. The performance of the developed approach is validated against the selected benchmarks existing in the literature.     

Non-polynomial cubic spline methods for the solution of parabolic equations

Second-order parabolic partial differential equations are solved by using a new three level method based on non-polynomial cubic spline in the space direction and finite difference in the time direction. Stability analysis of the method has been carried out and we have shown that our method is unconditionally stable. It has been shown that by suitably choosing the parameters most of the previous known methods for homogeneous and non-homogeneous cases can be obtained from our method. We also obtain a new high accuracy scheme of O(k ⁴+h ⁴). Numerical examples are given to illustrate the applicability and efficiency of the new method.     

Analysis of switched quantizer based on the quadratic spline functions

In this paper, an approximation of the optimal compressor function using the quadratic spline functions with 2L?=?8 segments is described. Since the quadratic spline with 2L?=?8 segments provides better approximation of the optimal compression function than quadratic spline with 2L?=?4 segments, capitalizing on the benefits of the obtained spline approximation, quantizer designing process is firstly performed for the so assumed number of segments and the Laplacian source of a unit variance. Then, to enhance the usability of the proposed model, the switched quantization technique is applied and a beneficial analysis is derived, providing insight in the robustness of the proposed quantizer performances with respect to the mismatch in designed for and applied to variances. Reached quality has been compared to another model from the literature, and it has been shown that the proposed model outperforms the previous model by almost 1.3?dB.     

矩形花键拉刀设计与制造问题的分析及解决方法

介绍了矩形内花键拉刀在设计、制造,使用过程中出现的各种问题时,分析拉刀键宽设计问题、制造中的质量问题、使用出现的问题,并一一提出解决的方法。     

间隙配合变轨距轮对与轨道间瞬态滚滑接触模拟研究

变轨距技术是实现不同轨距铁路联运的重要手段，我国相关研究仍在起步阶段。基于显式有限元法，建立包含渐开线花键副的三维变轨距轮对-轨道耦合瞬态分析模型，于时域内模拟速度高至400 km/h下的瞬态轮轨滚滑和花键间动态接触行为及其相互影响。模型充分考虑轮轨和花键副三维几何、系统高频结构振动等，引入时变牵引/制动转矩，采用集成库仑摩擦定律的"面-面"接触算法求解轮轨接触和花键接触。假设圆柱直齿渐开线花键，齿数取32，齿侧间隙恒0.1 mm，无激励下模拟结果表明，花键副的存在使得轮轨力波动范围大于传统轮对，例如，400 km/h下法向轮轨力波动幅值增加静载的3.7%。时速400 km/h和牵引系数0.05下，内外花键的径向和角向偏置使得花键左、右两侧各存在1个位置相对固定的承载区，各涉及5~6个键齿，承载面分别为II和I键齿工作面。瞬态法、切向接触应力极值发生在靠近一系悬挂侧的齿根或齿顶部，典型值分别为102 MPa和4.6 MPa，任一键齿的应力极值因不断有键齿进出承载区而波动上升和下降。牵引系数0.3时，左侧承载区消失，右侧承载区扩至18个键齿，相同时刻下的法、切向接触应力极值因承载齿数和总接触面积增加变为89 MPa和5.2 MPa。为变轨距机构中花键的强度和动力学分析及相关设计提供精确模拟手段。     

Quintic splines method for second-order boundary value problems

Abstract

We develop a numerical method for computing smooth approximations to the solution of a system of second-order boundary value problems associated with obstacle, unilateral and contact problems based on uniform mesh quintic splines. It is shown that this method gives better approximations than those produced by other collocation, finite-difference and spline methods. A numerical example is given to illustrate the applicability of the new method.     

基于多组合内容的图像识别机制

针对多组合内容图像的识别问题,提出了一种基于模糊推理融合机制的相似性距离度量算法的图像识别机制。首先,在分析现行图像识别方法的基础上,提出了薄板样条曲线TPS与模糊推理相结合的相似性距离度量机制的总体思路;其次,描述了基于形状上下文的变形图像的特征提取过程;而后讨论了薄板样条曲线TPS与模糊推理相结合的相似性距离度量机制,并将其应用在变形多组合内容图像的识别算法中。实验结果表明所提出的方法是有效的。     

Exact 3D boundary representation in finite element analysis based on Cartesian grids independent of the geometry

This paper proposes a novel Immersed Boundary Method where the embedded domain is exactly described by using its Computer‐Aided Design (CAD) boundary representation with Non‐Uniform Rational B‐Splines (NURBS) or T‐splines. The common feature with other immersed methods is that the current approach substantially reduces the burden of mesh generation. In contrast, the exact boundary representation of the embedded domain allows to overcome the major drawback of existing immersed methods that is the inaccurate representation of the physical domain. A novel approach to perform the numerical integration in the region of the cut elements that is internal to the physical domain is presented and its accuracy and performance evaluated using numerical tests. The applicability, performance, and optimal convergence of the proposed methodology is assessed by using numerical examples in three dimensions. It is also shown that the accuracy of the proposed methodology is independent on the CAD technology used to describe the geometry of the embedded domain. Copyright © 2015 John Wiley & Sons, Ltd.