Nonlinear Programming Methods for Real-Time Control of an Industrial Robot

The optimal control of an industrial robot is considered as a parametricnonlinear control problem subject to control and state constraints. Based onrecent stability results for parametric control problems, a robust nonlinearprogramming method is proposed to compute the sensitivity of open-loopcontrol solutions. Real-time control approximations of the perturbedoptimal solutions are obtained by evaluating first-order Taylor expansionsof the optimal solutions with respect to the parameter. The proposednumerical methods are applied to the industrial robot Manutec r3. Thequality of the real-time approximations is illustrated for perturbations inthe transport load.     

利用三角形及其九点圆的摄像机标定

提出基于三角形及其九点圆的摄像机标定方法.利用了三角形九点圆中其九个点的特殊性,并且利用透视投影变换保二次曲线不变性,得到其像点在像平面共椭圆,从而可以通过九点的映射关系将透视投影变换的非线性问题线性化.图像分割和角点提取的误差会直接影响标定的精度,在此三角形及其九点圆中的点特别是算法中的关键点三角形顶点和垂心都是三条直线的交点,减小图像分割与提取时造成的误差.DLT方法的不精确就源于图像分割和角点提取的误差,方法克服了DLT方法的不足.张的方法无法保证单应性矩阵的正交性,因此为了保证正交性和提高精度需要优化.与传统方法相比操作简单,应用九点圆定理,仿射变换的引入将透视投影非线性问题线性化,避免了参数之间的非线性方程求解,降低了参数求解的复杂性,因此其定标过程快捷,准确.模板的构造,减少了图像分割和交点提取误差,算法实现保证旋转矩阵的正交性.综合上述分析,理论上表明方法的有效性.同时实验表明,标定方法操作简单,不需要计算机视觉的专业知识,快速,精度高,鲁棒性好.     

Machine interference in automated cells

This paper presents a simulation and an analytical modeling of the machine interference problem in manufacturing cells. Each machine experiences two types of stoppage which are to be served by a robot. Several combinations of the distributions of the stoppages, service distributions, and service disciplines are studied. We determine the optimal number of machines assigned to the robot under different operating conditions such that the expected total cost of the manufacturing cell is minimized.This research is based on Mr. Norton's M.S. thesis, which was conducted at Rutgers.     

基于激光雷达数据SVM分类的室内环境识别研究

语义地图构建对移动机器人导航与规划具有重要意义,而环境分类是语义地图构建的核心问题。目前所采用的环境分类方法匹配率较低,已成为语义地图构建所面临的主要问题。对此笔者提出了一种基于支持向量机的分类方法,该方法利用激光雷达数据提取环境几何特征,训练SVM分类器对机器人工作空间模式进行识别,并将所提算法用于室内环境的语义分类。实验结果表明,该分类方法具有较高的识别率,可有效地实现语义地图构建。     

模糊逻辑在机器人逆运动学求解中的应用

冗余机器人逆运动学求解的方法很多，多数都不能很好的满足实时控制的要求，本文运用模糊逻辑的思想，构造了一种逆运动学求解方法，其计算量较其它方法大大减小，且满足实时控制的要求，仿真结果也证明了该方法的可行性。     

空间机器人组装超大型结构的动力学分析北大核心CSCD

超大型航天结构具有超大柔性、超低固有频率的特点,空间机器人在轨组装时应尽可能避免激起超大型结构的柔性振动.空间机器人组装超大型结构模块的过程分成抓捕阶段、位姿调整与稳定阶段、安装阶段和爬行阶段.通过对安装阶段的动力学与控制研究,提出共线安装的轨迹规划方法,有效避免了柔性结构振动.首先,采用自然坐标法和绝对节点坐标法建立主结构-空间机器人-待组装结构的在轨组装系统动力学模型.然后,将共线安装的要求转化为空间机器人的轨迹规划约束,要求空间机器人质心到主结构/待组装结构的距离保持不变,实现共线安装的轨迹规划.数值仿真表明:提出的组装方法在组装过程中可有效避免超大型结构的横向运动,降低夹持力矩.最后,分析了系统参数对组装过程动力学响应的影响,为超大型航天器的在轨组装提供了参考.     

带时间窗的车间搬运机器人路径优化建模及算法研究

本文以车间搬运机器人为研究对象,在考虑时间窗的前提下,求解机器人进行物料配送和成品回收场景下的路径优化问题。提出一种强化学习遗传蚁群算法,首先利用扫描法求解初始搬运机器人的数量,并将子路径节点的几何中心设置为虚拟节点,利用嵌入遗传算子的蚁群算法求解连接虚拟节点的最优路径,再利用强化学习算法求解子路径的最优结果;最后将基本成本、运输成本和时间惩罚成本的加权和作为目标解,并最终求出满足约束条件的最优解。通过与基准问题求解结果对比,验证了强化学习遗传蚁群算法的优越性。     

Dynamics and trajectory planning of a planar flipping robot

In this paper, a new planar one-legged robot model is firstly proposed, which, unlike previous one-legged robot with springy legs, consists of three revolute joints. Then a novel manner of one-legged locomotion (i.e., ballistic flip) is designed for this robot. A complete flipping gait cycle is composed of four phases: two stance phases and two flight phases. During flight phases, no active control is needed on the knee joint. Rotational motion and translational motion is decoupled from each other in flight phases. Landing of the robot is regarded as an inelastic impulsive impact. During stance phases, the robot model can be simplified as a two-degree-of-freedom rigid manipulator. Based on analysis of kinematics and dynamics of the flip robot, trajectory planning of cyclic flip gait is formulized as a problem of numerical optimization subject to nonlinear constraints such as positive reaction force of ground and finite torque of the joints. One potential application of the flipping robot is space exploration, which urgently requires the legged locomotive robots to be light-weighted and energy efficient.     

Homoclinic Chaos in 2-DOF Robot Manipulators Driven by PD Controllers

The existence of Smale horseshoes in the dynamics of twodegrees of freedom (2-DOF) robot manipulators with viscous damping anddriven by classical proportional-derivative (PD) controllers is proved.The situation where an actuator failure occurs is also analyzed. Thecontrollers correspond to the classical PD and the PD with gravitycompensation. They are considered as non-Hamiltonian perturbations of anundriven 2-DOF robot; then a technique developed by Holmes and Marsden,which uses a combination of a reduction scheme and Melnikov's methodwith an energy balance argument, is applied.     

The effect of initial geometric imperfection on the nonlinear resonance of functionally graded carbon nanotube-reinforced composite rectangular plates

The purpose of the present study is to examine the impact of initial geometric imperfection on the nonlinear dynamical characteristics of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) rectangular plates under a harmonic excitation transverse load. The considered plate is assumed to be made of matrix and single-walled carbon nanotubes (SWCNTs). The rule of mixture is employed to calculate the effective material properties of the plate. Within the framework of the parabolic shear deformation plate theory with taking the influence of transverse shear deformation and rotary inertia into account, Hamilton’s principle is utilized to derive the geometrically nonlinear mathematical formulation including the governing equations and corresponding boundary conditions of initially imperfect FG-CNTRC plates. Afterwards, with the aid of an efficient multistep numerical solution methodology, the frequency-amplitude and forcing-amplitude curves of initially imperfect FG-CNTRC rectangular plates with various edge conditions are provided, demonstrating the influence of initial imperfection, geometrical parameters, and edge conditions. It is displayed that an increase in the initial geometric imperfection intensifies the softening-type behavior of system, while no softening behavior can be found in the frequency-amplitude curve of a perfect plate.