Solving 3D Geometric Constraints for Assembly Modelling

A geometric constraint solving method is presented that takes well-constrained mating conditions between a base and a mating component and directly transforms them into a 4 × 4 matrix that determines the relative orientation and location of the mating component with respect to the base component. In the proposed procedure, the 4 × 4 transformation matrix is determined by directly computing a rotation matrix TR and a translation matrix TL that define the relative orientation and location of the mating component, respectively. Thus, first, the rotation matrix is computed by solving a set of linear constraint equations associated with the orientation of two mating components. After repositioning the mating component by applying the rotation matrix TR, the translation matrix is calculated by solving a set of linear constraint equations associated with location. This new method is computationally very effective, since the transformation matrix for relative orientation and location of the mating component is algebraically derived directly from the linear equations associated with the mating conditions.     

双目CCD结构光三维测量系统中的立体匹配

在立体视觉中,比较了几种常见立体匹配方法,并针对存在的问题,提出了多种方法融于一体的高效立体匹配方法.首先将计算机构造的用于解相的光栅由投影仪投射到物体上,再将计算机构造的一系列黑白相间的编码光栅也由投影仪投射到物体上;然后将畸变栅线图像由摄像机采集到计算机中,用解相光栅进行解相得到折叠在[-π,π]区间内的相主值,用所述结构光编码方法进行相展开得到相位的周期,二者相加得到真实相位值.利用插值算法将具有相同相位的点拟合成连续曲线,从而实现了两幅CCD图像相同相位曲线的匹配,再根据外极约束条件,得到两幅图像点的匹配.在反向工程中,用该方法对电话接线筒进行三维测量,实验验证了该方法进行立体匹配的高效性和准确性.     

一种判别空间两线段干涉的快速算法

在多机械手系统中 ,机械手各杆状关节相互之间在运动过程中极易产生机械干涉 ,快速判别两杆状物体互相产生机械干涉的算法对多机械手系统的动态任务规划具有十分重要的意义。一般的研究方法都是把杆状物体简化为空间线段来进行分析和计算他们之间的距离或者具体的交点位置。实际上 ,判断两空间线段是否产生干涉只需要知道两线段是否存在交点 ,而不需具体计算交点的位置以及两空间线段之间的距离 ,就可判别其干涉状态 ,基于此本文提出了一个极为简单的计算方法 ,该方法利用解析几何中的理论 ,提出了几个基本定义 ,将空间的两杆状物体抽象为线段 ,然后投影到笛卡尔空间直角坐标的三个直角投影面 ,通过一些简单的加减乘除计算 ,就可判别两线段干涉状态。     

A new automatic reference and switching unit for calibration of high value resistors in the range 100 kΩ to 10 TΩ

We describe a Reference and Switching Unit (RSU), that, with a digital multimeter (DMM) and a dc voltage calibrator, constitutes a system for calibration of standard resistors in the range 100 kΩ–10 TΩ at measurement voltages up to 1000 V. This system represents an implementation of a DMM-based system already developed at IEN. We report the characteristics of the DMM-based system, the metrological and electronic features of the RSU, the uncertainty levels that can be achieved with the DMM-based and whit the RSU-based systems. Finally, we show the obtained results in order to check the compatibility of the two systems in the calibration of standard resistors in the range 1 GΩ–1 TΩ. The 2σ best measurement capabilities of the RSU-based system span from 6.3×10⁻⁶ for the calibration of a 100 kΩ standard resistor at 10 V, to 1.2×10⁻³ for the calibration of 10 TΩ standard resistor at 1000 V.