“三点一线式”传动系统设计与选取

为了解决双轴承座、减速电机三者不在同一直线上而引起设备功率大幅度耗损及减速电机容易损坏等问题,文中介绍了几种常用的解决方案,减少和消除"三点不在同一直线"带来的不利状况。     

基于几何约束的直线实时定位新方法

本文介绍了一种利用空间三条直线的图像信息和三条直线间的几何位置约束关系来确定物体姿态的新方法.使用的物体模型为在空间交于两点的三条非共面直线.这种方法的好处是数学表达式简单,易于求解.本文详细叙述了这种方法的具体实现过程.仿真实验表明,这种方法具有较高的定位精度和良好的实时性.     

3-RPS并联机器人的奇异位姿研究

奇异的运动学原理是物体上非共线三点的速度的三个法平面的交点,能落于该三点决定的平面上.这是物体上非共线三点的速度能确定此物体螺旋运动的充分必要条件.依据此原理得到一种新的判别并联机器人机构奇异的简捷方法.这里用此方法研究了3-RPS机构的奇异位姿.     

基于立体视觉和激光标记的空间物体位姿的快速定位算法

建立了一种4自由度双目立体视觉装置的传感器模型,根据空间两条相交射线唯一确定空间一点的原理,提出了在摄像机上加装激光源的方法,通过激光标记来解决目标物体上同一点在两幅CCD图像上对应点的快速匹配问题,从而很方便地求取目标物体的深度信息。最后,研究了目标物体空间位姿的图像定位算法,并通过确定的空间圆柱体位姿验证了该方法的正确性。     

匀速直线运动多面体4D干涉检测算法

已有的干涉检测算法采用在离散的时间点上进行求交的方法 ,效率和可靠性低 ,本文提出一种匀速直线运动多面体在时间和空间的 4维直线求交干涉检测算法 ,其检测效率与静止物体的干涉求交相同     

大R样板的测量

大R样板是指弦长短、弦高小、弦长与半径之比极小(一般可界定为1:10)的圆弧型面样板。其型面半径较大,一般都超过1000mm,有的甚至超过2000mm,而其有效弧段所含弦长一般不超过100mm,样板有效弧段几乎呈直线,而一般大R样板半径误差不允许超过0.25％,因此,要通过测量确定其地面半径相当困难。理论上,不在同一条直线上的三点可以确定一个圆。弦长弦高法就是基于这个     

基于3维点云欧氏聚类和RANSAC边界拟合的目标物体尺寸和方位识别

目标物体尺寸和方位识别是移动机器人在未知环境下实现自主搬运的关键技术,主要难点是如何从混有地面和周边环境信息的3维点云数据中提取物体信息,并准确识别其方位和尺寸。常用的方法是通过3维点云建立物体包围盒,但是现有的基于PCA(主成分分析)或基于边缘点云提取的包围盒建立方法对物体边缘点云噪声比较敏感。文中主要针对室内搬运场景中方形箱式物体,提出1种基于3维点云欧氏聚类和RANSAC(随机采样一致性)边界拟合的物体尺寸和方位识别算法。首先,采用点云截断、体素滤波降采样和离群点移除对数据进行预处理,然后采用基于K-D树的快速聚类算法进行物体与物体之间的分割,接着将分割后物体3维点云进行2维投影。由于投影后物体2维点云边缘点密度远高于内部点云密度,采用RANSAC算法对边缘点云进行直线拟合。该直线能够近似物体边缘点云分布的期望均值,受物体边缘点云噪声的影响较小。实验表明该算法精度较高、速度较快、鲁棒性好,可用于移动机器人物体搬运作业等领域。     

基于视觉的运动物体特征点参数测量方法研究

主要研究利用机器视觉的非接触式测量方法实现对运动物体特征点的轨迹、速度和加速度三个运动参数的测定。通过在运动物体上设定一个特征点,采用基于运动估计的模板匹配技术实时跟踪特征点在各个时间点的位置。通过对动态图像序列的分析和处理从而在线得到运动物体特征点的三个运动参数。为了实现实时在线测量,采用了基于运动估计的图像匹配算法加速了图像匹配算法的计算速度,实现实时在线测量。此算法计算一次位置点需要的时间为20ms,图像标定的精度为1μs,达到了实时在线测量的要求。测试结果表明:研究的基于运动估计的运动物体特征点测量算法运算速度快、可靠以及测试简单等特点。     

一种双目立体视觉技术中三维坐标点的改进求取算法

在双目立体视觉技术中,经过特征提取和立体匹配得到两两对应的像素点对,根据摄像机标定建立的物体空间坐标到像平面坐标对应的矩阵,利用最小二乘法求取物体三维空间点的坐标。但是,由于最小二乘法没有考虑所建立的超限定方程组所代表的几何意义,计算出的点坐标精度不高。本文提出一种考虑方程组所代表几何意义的方法,利用异面直线公垂线中点去逼近物体空间点。     

《机械工程学报》英文版2004年第17卷第2期目次、摘要预告

奇异的运动学法及其应用实例 李艳文 黄真 (燕山大学机器人研究中心 秦皇岛 066004)摘要:论证了奇异的运动学原理:物体上非共线三点的速度的三个法平面的交点,能落于该三点决定的平面上。这是物体上非共线三点的速度能确定此物体的螺旋运动的充分必要条件。依据此原理得到一种新的判别并联机器人机构奇异的简捷方法。这里用此方法分析了3-RPS机构,首次得到此机构的三维奇异轨迹和最一般奇异判别式,并用线几何、螺旋理论或雅可比矩阵作了验算以证明方法的有效性。关键词:并联机器人 3-RPS 运动学法 奇异研究中图分类号:TH112国家自然科学基金资助项目(50275129)     

METH0D USED IN SINGULARITY RESEARCH BASED 0N KINEMATICS AND ITS EXAMPLE IN APPLICATION

First the kinematic principle of singularity is proved, that is the intersecting point of threenormal planes of three velocities at three non-collinear points in a rigid body lying in the plane determined by the three corresponding points. It is a sufficient and necessary condition that the velocities ofthree non-collinear points in a rigid body can determine a screw motion of the body Based on thisprinciple, a simple and direct new method to distinguish the singularity of the parallel manipulator islered. Wth this new kinematic method, the 3-RPS parallel manipulator is studied. Its singularity lociare obtained for some orietations for the first time and verified with Grassmann line geometry andscrew theory and the force Jacobian matrix.     

METHOD USED IN SINGULARITY RESEARCH BASED ON KINEMATICS AND ITS EXAMPLE IN APPLICATION

First the kinematic principle of singularity is proved, that is the intersecting point of three normal planes of three velocities at three non-collinear points in a rigid body lying in the plane determined by the three corresponding points. It is a sufficient and necessary condition that the velocities of three non-collinear points in a rigid body can determine a screw motion of the body. Based on this principle, a simple and direct new method to distinguish the singularity of the parallel manipulator is derived. With this new kinematic method, the 3-RPS parallel manipulator is studied. Its singularity loci are obtained for some orientations for the fast time and verified with Grassmann line geometary and screw theory and the force Jacobian matrix.     

Singularity kinematics principle and position-singularity analyses of the 6-3 Stewart-Gough parallel manipulators

This paper presents a new principle and method of kinematics to analyze the singularity of Stewart-Gough parallel manipulators and addresses the property identification of the position-singularity loci of the 6-3 Stewart-Gough manipulators for special orientations. Based on the kinematic relationship of a rigid body, a necessary and sufficient condition that three velocities of three non-collinear points in a moving rigid body can determine a screw motion is addressed and some typical singular configurations of the 6-3 Stewart-Gough parallel manipulators are also addressed in detail. With the above-mentioned condition, a symbolic analytical polynomial expression of degree three in the moving platform position parameters, representing the position-singularity locus of the 6-3 Stewart-Gough manipulators for special orientations, is derived; and the property identification of the position-singularity loci of the 6-3 Stewart-Gough manipulator for these special orientations is investigated at length. It is shown that position-singularity loci of the 6-3 Stewart-Gough parallel manipulator for these special orientations will be a plane and a hyperbolic paraboloid, even three intersecting planes.     

Point-based Jacobian formulation for computational kinematics of manipulators

Computational kinematic analysis of mechanisms is a promising tool for the development of new classes of manipulators. In this paper, the authors present a velocity equation to be compiled by general-purpose software and applicable to any mechanism topology. First, the approach to model the mechanism is introduced. The method uses a set of kinematic restrictions applied to characteristic points of the mechanism. The resultant velocity equation is not an input–output equation, but a comprehensive one. In addition, the Jacobian characterizing the equation is dimensionless hence extremely useful for singularity and performance indicators. The motion space of the manipulator is obtained from the velocity equation. Angular velocities are compiled out of three non-collinear point velocities. The procedure is applied to a 3-DoF parallel manipulator to illustrate.     

敏捷卫星姿态机动的奇异最优控制

研究姿态机动的时间最优控制时,通常只考虑最优解为Bang-Bang控制的情况,假设了开关函数仅在有限个孤立点为零,本文对假设之外的奇异最优控制进行探讨。以球对称光学敏捷卫星为对象,根据姿态机动最优控制问题的数学模型,证明了开关函数的特殊性质。在不同边界条件下,结合一阶必要条件、广义勒让德-克莱伯西条件等,分析了最优控制包含奇异区间的所有情况,得到了奇异控制最优性的必要条件。结果表明,对于起止角速度为0,乃至起止角速度相同的所有工况,可以直接排除奇异控制最优的可能性,最优控制中各个分量在+1和-1之间切换;而起止角速度相异时,存在奇异控制最优的情况,且奇异分量的开关函数在全过程均为0,奇异阶数为无穷阶,文中给出了相应算例予以佐证。     

用于结构光视觉传感器标定的特征点获取方法

提出了一种基于共面参照物自由移动来获取结构光视觉传感器标定特征点的新方法。该方法通过以摄像机三维坐标系为中介,将多个局部世界坐标系下的标定特征点统一到全局世界坐标系中,得到位于光平面上的非共线标定特征点的三维世界坐标。该方法降低了标定设备的成本,简化了结构光视觉传感器的标定过程,从而提高了结构光视觉传感器工程化应用的便捷性。实验表明,该方法切实可行     

基于多体系统动力学的重载凹底平车动态响应仿真分析

为研究重载凹底平车的动态响应特性,基于多体系统动力学软件SIMPACK,建立320 t凹底平车系统刚体与刚柔耦合体动力学模型,进行动态响应仿真分析,仿真计算空、重车在不同速度下的运行,获得中底架试验点处的加速度动态响应结果。与线路试验值比较发现,在空、重车试验点位置加速度值的变化中,刚柔耦合模型的峰值要比刚体模型值要大,但两种模型下的总体趋势相似,加速度最大值都是随着速度的提高而逐渐增大,并且在每一种速度下刚柔耦合模型的值均比刚体模型的要大。另外,在运行速度不断提高时,仿真得到的两种模型的加速度平均值在空、重车试验点位置也是随着速度增加而增大,与试验结果吻合很好。其中,刚柔耦合模型的加速度平均值比刚性模型的更接近试验值,说明刚柔耦合模型比较合理。同一级速度下,重车的动态响应比空车大。     

A successive approximation algorithm for the inverse position analysis of the general serial manipulators

A new fast numerical algorithm for the solution of the inverse position analysis of the serial manipulator is presented. With the algorithm, the inverse solution of the general serial manipulators can be achieved quickly under the desired precision when we know the position of the three non-collinear end-effector points, which is much easier to be measured than the orientation of the end-effector. The difference between the new numerical algorithm and the general iterative method is that it can search out the solution when the manipulator is at the singular configuration; and the initial configuration used in the successive approximation process may also be the singular configuration. So the convergence domain is bigger than that of the general iterative method. The position analysis of the general 6R serial manipulator is illustrated in the literature as an example and the simulation results to verify the efficiency of the proposed algorithm. Since the three non-collinear end-effector points can be selected at random, the algorithm can be applied to any other serial manipulator.     

Massenersatz durch punktmassen in räumlichen Getrieben

Dynamic and kinetostatic analysis of three-dimensional mechanisms (i.e. mechanisms with intersecting or skew axes) can be brought about by using mass points. The objective of this paper is to give simple ways of determining such mass points with respect to their quantity and position by means of matrix calculus.Two rigid mass systems will be in quadratic equivalence, if their total masses are equal and their centers of mass coincide and their second moments of mass are equal with respect to a common system of coordinates. Under equal initial conditions, the two bodies will then perform equal motions if equal forces are acting upon them. Thus the total mass of a given three-dimensional rigid body may be substituted for by a finite number of mass points in rigid interconnection (Fig. 1). A mass point of quantity m_i at a point P_i(x_i, y_i, z_i) is determined by four defining quantities (m_i, x_i, y_i, z_i). The condition of equality of the total masses leads to one equation, the coincidence of the centers of mass results in three equations, and six equations follow from the equality of the second moments of mass. Thus the condition of quadratic equivalence will result in a system of non-linear equations (equation (4)) consisting of 1 + 3 + 6 = 10 scalar equations. These must be satisfied by four defining quantities per mass point. Nevertheless a three-dimensional body cannot be substituted for by three mass points with 3 × 4 = 12 defining quantities, since these three mass points are always on the same plane and so can only substitute for a mass system on one plane. The minimum number of mass points necessary is four. Of the total 4 × 4 = 16 defining quantities, 16 ? 10 = 6 can be chosen freely. After introducing suitable values for these six quantities, the ten unknown quantities can be calculated in a definite and explicit way (equations (6)–(15)) in spite of the above-mentioned system of equations being non-linear. It is not necessary to calculate the principle axes of inertia.As two further instances the substitution of a mass system on one plane by three mass points and the substitution of a rectilinear mass system by two mass points is discussed.     

带工程约束的点匹配算法

在基于三维测量点的刚体姿态计算中,刚体的最佳姿态往往需要让刚体的某些关键点满足约束要求。以往的点匹配算法从不考虑原始测点带有工程约束的问题,获得的姿态参数不能满足工程实际的需要。介绍一种带工程约束的点匹配算法,该算法利用多目标优化模型,把两点对称、多点在同一平面上、多点在同一直线上等工程约束引入到点匹配的优化目标函数中,利用牛顿非线性最优化方法求解6个姿态参数。利用权值矢量实现对多个约束进行同时控制的误差分配求解,为带工程约束的刚体最佳姿态计算提供一套有效的解决方案。