基于扩展雅可比矩阵的冗余液压驱动四足机器人运动控制

针对冗余液压驱动四足机器人运动学逆解问题,提出一种基于扩展雅可比矩阵的冗余液压驱动四足机器人运动控制方法.该方法既能解决冗余自由度带来的逆解多解问题,还能使机器人足端入地角度满足摩擦锥要求避免足端滑动.首先,规划机器人足端轨迹得到机器人足端速度,在分析机器人足端入地角度对机器人运动性能影响的基础上,结合机器人腿部结构几何关系,建立扩展雅可比矩阵,确立机器人关节角度速度和足端速度的映射关系,即得到机器人关节角度的解.然后,在对角步态下,通过仿真对传统的梯度投影法和提出的扩展雅可比矩阵法进行对比,理论分析及仿真表明传统的梯度投影法存在误差累积,且在实时性上不如扩展雅可比矩阵法.最后,实验验证了基于扩展雅可比矩阵逆运动学分析方法的可行性和有效性.     

用于丝驱动连续体机器人的实用运动学研究

针对单段及多段连续体机器人运动学问题,提出分段常曲率与粒子群算法相结合的完整正逆运动学分析方法.以双段丝驱动连续体机器人为研究对象,首先设计含平移段的机器人样机;然后利用分段常曲率方法建立驱动空间与关节空间的相互映射,根据齐次变换得到关节空间至工作空间的正映射关系;最后利用线性递减权重粒子群算法实现工作空间至关节空间的逆映射.对双段连续体机器人的运动学进行仿真及逆运动学求解耗时测试,并在研制样机上进行了实验验证.仿真结果说明了所提运动学研究方法的合理性及逆运动学求解的快速性,实验结果显示位置平均误差小于双段连续体机器人本体长度的6.22％,验证了所提运动学的有效性.     

连续型机器人运动学仿真和操控系统设计

为了适应越来越复杂的非结构化环境,设计了一种基于球铰链连接和柔性支撑杆结合的线驱动连续型机械臂,并基于常曲率模型的假设建立连续型机器人的运动学模型,研究连续型机器人驱动映射关系,利用MATLAB进行运动学和驱动映射的仿真,仿真结果表明连续型机器人的空间优越性。搭建三关节连续型机器人样机平台,基于连续型机器人的特点设计末端关节跟随手柄操作模式,并在样机平台上实验验证,实验结果表明了运动学模型和驱动映射关系的合理性和正确性以及操控方式的可行性。     

工业码垛机器人运动学仿真

码垛机器人的运动学分析是实现码垛控制的前提和基础.针对码垛机器人的结构特点,运用空间几何方法对码垛机器人的运动学特性进行理论分析,建立驱动关节与末端执行器的映射关系.利用INVENTOR和ADAMS软件建立了码垛机器人参数化虚拟样机模型,进行运动学仿真.同时,对码垛机器人码垛轨迹仿真优化.实验结果证明,新型工业码垛机器人具有良好的运动学特性,符合现代码垛作业的要求.新提出的机器人仿真分析方法,对进一步提高码垛机器人技术的设计水平,具有促进和借鉴作用.     

线驱动模块化七自由度机器人轨迹跟踪控制

阐述了一种线驱动与常规串联驱动相结合的混合设计方法．这种设计方法融合了线驱动并联机构和模块化串联机构的优点，而且混合驱动机器人的工作空间大于完全线驱动机器人的工作空间．文章首先介绍了混合驱动机器人的机构设计，也就是机器人的肩关节采用模块化串联结构，而肘、腕关节采用线驱动结构．然后利用几何分析的方法来解机器人前向运动学问题．在分析驱动线长与关节角之间变换关系的基础上，分别利用速度法和关节角增量法来计算机器人逆向运动学解．最后，使用VC++实现混合驱动机器人对直线运动轨迹进行跟踪的仿真，从而证明了文章所描述的设计方法的正确性．     

基于节点支路链矩阵的配电网动态拓扑分析方法研究与应用*

针对配电网中现有拓扑分析方法运算复杂、速度较慢、重用性较差,以及当配网规模扩大或开关状态改变时,不易及时地反映网络拓扑信息等问题,提出基于支路链矩阵的配电网动态拓扑分析方法。在系统正常运行时,采用特殊节点法将配电网划分多个支路链子图,以节点-支路链矩阵描述配网拓扑结构,借助邻接矩阵标记法与深度优先搜索原则结合完成更新后的拓扑网络的电气岛连通性分析。当支路动态变化时,根据支路属性利用方向深度优先搜索法快速地修改网络拓扑结构,局部更新节点-支路链矩阵。多个实例结果表明该方法可适应多种配电网接线结构,搜索过程中节点数量明显减少,降低了算法复杂度,提高了拓扑分析速度,为不同配网结构动态分析提供了一种有效的方法。     

一种多自由度蟑螂机器人的运动学分析

建立了仿生蟑螂机器人在三腿支撑状态下的等效并联模型,运用旋量理论和指数积公式,对其运动学进行了分析;提出了利用Paden-Kahan子问题法数值求解机器人六自由度腿的关节角位移的逆运动学方法,前向运动学的求解首先根据机体的自然约束建立两条描述前向运动学的支路,然后利用其等价关系,结合指数积公式推导得到机体位姿;在Matlab下对提出的运动学算法进行了验证,为后续的运动学分析和轨迹规划奠定了基础。     

面向复杂地形的四足机器人步态生成方法

为实现四足机器人在凹凸地形上稳定运动并能选择最大步长的目的,提出了基于稳定裕度的步态规划方法;基于研究对象,建立四足机器人的运动学方程及逆运动学方程,将机器人足端的位置映射为各关节的关节变量;提出工作空间矩阵的概念,将所需克服的地形高度反映到工作空间矩阵中,并选择最优步态区域;依据四足机器人的立足点在质心坐标系下的空间坐标,以纵向稳定裕度为约束条件,在工作空间矩阵中计算机器人摆动腿的最大步长并规划机械腿的运动轨迹;针对所提出的方法,分别利用MATLAB和ADAMS进行仿真验证;在MATLAB环境中计算并验证质心的水平投影是否在立足点形成支撑多变形内,而ADAMS平台分析机器人在复杂地形上的位移变化及姿态变化。仿真结果表明机器人的质心始终在支撑多边形内,机器人的躯干姿态基本保持不变且运动速度匀速,所提出的方法能够保证机器人稳定行走,为四足机器人的稳定运动提出依据。     

空间机器人连续运动轨迹控制建模和仿真研究

基于地面机器人常用的D-H 建模方法和空间机器人（SR）满足的动量守恒和角动量守恒原理,提出 了SR 连续运动轨迹控制建模算法．首先基于地面机器人雅可比矩阵的思想和D-H 法,建立了适用于空间机器人 的运动学模型;其次研究了空间机器人的广义雅可比矩阵计算及其连续运动轨迹控制的有效算法;最后通过计算 机仿真验证了所提出算法的有效性．本文基于D-H 方法的SR 概念模型和运动学模型可推广到包含旋转关节和平 移关节的树型结构链杆的任何SR．     

面向手势动作捕捉的传感器设计及主从手运动映射

本文针对人手和机器人灵巧手在运动学上尺寸的不一致现象带来的主从手指尖运动空间映射的不一致性进行研究.基于聚氨酯拉伸应变传感器构建了测量手指关节弯曲角度的数据手套.通过建立主从手的运动学模型,基于旋转矩阵理论及正向运动学提出了一种指尖运动轨迹计算方法及手势动作捕捉算法.基于正向运动学及逆向运动学的指尖运动映射算法建立了主从手的指尖运动空间轮廓.建立虚拟实验场景,分别针对关节角度映射算法、手势动作捕捉算法及指尖运动映射算法进行了一系列试验.通过实验得出基于聚氨酯的拉伸应变传感器具有良好的时间响应特性及电学稳定性,基于手势动作捕捉算法能够获取主从手的指尖运动空间轮廓,指尖运动轨迹的计算误差控制在2.8 mm以内.结果证明了基于手势动作捕捉算法以及指尖运动映射算法能够实现主从手指尖运动空间的一致性.     

基于Octomap的仿人机器人局部环境与能力图模型算法

基于3D点云数据的机器人三维空间能力图模型算法存在体素网格搜索计算量大的问题，由于OcTree在三维空间细分时的层次化优势，提出一种基于Octomap的局部环境与能力图模型算法。首先，根据NAO机器人的关节组成、正向运动学、逆向运动学和刚体坐标变换，对NAO仿人机器人构建全身二叉树状运动学模型；其次在此基础上使用前向运动学在笛卡儿空间计算离散的三维可达点云，并将其作为机器人终端效应器的基础工作空间；然后重点描述将点云空间表示转化为Octomap空间节点表示的方法，尤其是空间节点的概率更新方法；最后提出根据节点几何关系进行空间节点更新顺序选择的优化方法，从而高效地实现了仿人机器人能力图的空间优化表示。实验结果表明，相对于之前的原始Octomap更新方法，优化后的算法能降低近30%空间节点数，提高计算效率。     

A comparison between the Denavit–Hartenberg and the screw-based methods used in kinematic modeling of robot manipulators

This paper aims to integrate didactically some engineering concepts to understand and teach the screw-based methods applied to the kinematic modeling of robot manipulators, including a comparative analysis between these and the Denavit–Hartenberg-based methods. In robot analysis, kinematics is a fundamental concept to understand, since most robotic mechanisms are essentially designed for motion. The kinematic modeling of a robot manipulator describes the relationship between the links and joints that compose its kinematic chain. To do so, the most popular methods use the Denavit–Hartenberg convention or its variations, presented by several author and robot publications. This uses a minimal parameter representation of the kinematic chain, but has some limitations. The successive screw displacements method is an alternative representation to this classic approach. Although it uses a non-minimal parameter representation, this screw-based method has some advantages over Denavit–Hartenberg. Both methods are here presented and compared, concerning direct/inverse kinematics of manipulators. The differential kinematics is also discussed. Examples of kinematic modeling using both methods are presented in order to ease their comparison.     

Operating robot manipulators through kinematic singularities using a continuously sliding mode control

Planning the motion of end-effectors of robot manipulators can be carried out more directly in the Cartesian space compared to the joint space. Yet, Cartesian paths may include singular configurations where conventional control schemes suffer from excessive joint velocities and loss of tracking accuracy. The difficulties arise because the Jacobian matrix that is used to establish a linear relation between the velocities in the task and joint spaces loses rank at singularities. The problem can be resolved by using a local second-order approximation of robot kinematics for the joint velocities, which is called Resolved Motion Quadratic Rate Control. In this article, we present a control strategy based on this approach and a recently developed variable structure control scheme. The controller receives Cartesian inputs whenever the manipulator is outside the singular domain. Otherwise, it uses resolved motion quadratic rate control to compute the required joint inputs. Numerical simulation is performed to show that the proposed control scheme provides accurate tracking of the desired motion without inducing excessive control activity when operating robot manipulators through singular configurations. © 1994 John Wiley & Sons, Inc.     

An algorithmic approach to coordinate transformation for robotic manipulators

Coordinate transformation is one of the most important issues in robotic manipulator control. Robot tasks are naturally specified in work space coordinates, usually a Cartesian frame, while control actions are developed on joint coordinates. Effective inverse kinematic solutions are analytical in nature; they exist only for special manipulator geometries and geometric intuition is usually required. Computational inverse kinematic algorithms have recently been proposed; they are based on general closed-loop schemes which perform the mapping of the desired Cartesian trajectory into the corresponding joint trajectory. The aim of this paper is to propose an effective computational scheme to the inverse kinematic problem for manipulators with spherical wrists. First an insight into the formulation of kinematics is given in order to detail the general scheme for this specific class of manipulators. Algorithm convergence is then ensured by means of the Lyapunov direct method. The resulting algorithm is based on the hand position and orientation vectors usually adopted to describe motion in the task space. The analysis of the computational burden is performed by taking the Stanford arm as a reference. Finally a case study is developed via numerical simulations.     

A normal form augmentation approach to adaptive control of space robot systems

In this paper, we model a free-floating space robot system as anextended robot which is composed of a pseudo-arm representing the base motion resulting from six hyperthetic passive joints, and a real robot arm. The model allows us to categorize the space robot as an under-actuated system, and reveal fundamental properties of the system. Through input-output linearization of the model, we demonstrate a non-trivial internal dynamics, and propose an adaptive control scheme based on a normal form augmentation approach. This approach overcomes two fundamental difficulties in adaptive control design of space robot systems, i.e., nonlinear parameterization of the dynamic equation, and uncertainty of kinematic mapping from Cartesian space to joint space.     

A Fuzzy Qualitative Framework for Connecting Robot Qualitative and Quantitative Representations

This paper proposes a novel framework for describing articulated robot kinematics motion with the goal of providing a unified representation by combining symbolic or qualitative functions and numerical sensing and control tasks in the context of intelligent robotics. First, fuzzy qualitative robot kinematics that provides theoretical preliminaries for the proposed robot motion representation is revisited. Second, a fuzzy qualitative framework based on clustering techniques is presented to connect numerical and symbolic robot representations. Built on the $k-{{bb AGOP}}$ operator (an extension of the ordered weighted aggregation operators), k-means and Gaussian functions are adapted to model a multimodal density of fuzzy qualitative kinematics parameters of a robot in both Cartesian and joint spaces; on the other hand, a mixture regressor and interpolation method are employed to convert Gaussian symbols into numerical values. Finally, simulation results in a PUMA 560 robot demonstrated that the proposed method effectively provides a two-way connection for robot representations used for both numerical and symbolic robotic tasks.      

New inverse kinematic algorithms for redundant robots

New inverse kinematic algorithms for generating redundant robot joint trajectories are proposed. The algorithms utilize the kinematic redundancy to improve robot motion performance (in joint space or Cartesian space) as specified by certain objective functions. The algorithms are based on the extension of the existing “joint-space command generator” technique in which a null space vector is introduced which optimizes a specific objective function along the joint trajectories. In this article, the algorithms for generating the joint position and velocity (PV) trajectories are extensively developed. The case for joint position, velocity, and acceleration (PVA) generation is also addressed. Application of the algorithms to a four-link revolute planar robot manipulator is demonstrated through simulation. Several motion performance criteria are considered and their results analyzed.