The robust design of parallel spherical robots

In this paper a robust methodology, reported in a previous work, is applied to the design of the unactuated joints of a spherical three-degree-of-freedom parallel robot, the Agile Wrist (AW). Robustness is needed because of the extremely difficult task of manufacturing a spherical mechanism with all its joint axes concurrent at a single point. In order to account for the unavoidable manufacturing errors, it is proposed here to replace the unactuated revolute (R) joints of an existing design by cylindrical (C) joints. The latter function even in the presence of nonconcurrent axes. A procedure, based on dual numbers, is used to solve the inverse kinematics of the entire mechanism in order to determine the rotations and translations of each C joint. Based on statistical results of the kinematic analysis, the C joints are suitably dimensioned.     

Vision/force control of parallel robots

In this paper, force and position control of parallel kinematic machines are discussed. Cartesian space computed torque control is applied to achieve force and position servoing directly in the task space within a sensor-based control architecture. The originality of the approach resides in the use of a vision system as an exteroceptive pose measurement of a parallel machine tool for force control purposes. Three different mechanical structures with different degrees of freedom are considered to validate the approach.     

Analysis of the dynamic stress of planar flexible-links parallel robots

This paper presents a method for the dynamic stress analysis of planar parallel robots with flexible links and a rigid moving platform. The finite element-based dynamic model of flexible parallel robots is proposed. The relation between elastic deformations and elastic displacements of the flexible links is investigated, considering the coupling effects of elastic motion and rigid motion. The elastic deformations of links are calculated. Considering the effects of bending-shearing strain and tensile-compression strain, the dynamic stress of the links and its position are derived by using the Kineto-Elastodynamics theory and the Timoshenko beam theory. Due to the flexibility of the links, the dynamic stresses are well illustrated through numerical simulation. Compared with the results of the finite element software SAMCEF, the numerical simulation results show the good coherence and advantages of the analysis method. The dynamic stress analysis is demonstrated to have a significant impact on the analysis, design and control of flexible parallel robots.     

A robust forward-displacement analysis of spherical parallel robots

The forward-displacement analysis of spherical parallel robots (SPRs) is revisited. A robust approach, based on the input–output (I/O) equation of spherical four-bar linkages, is proposed. In this approach, the closed-loop kinematic chain of a SPR is partitioned into two four-bar spherical chains, whose I/O equations are at the core of the analysis reported here. These equations lead to a trigonometric equation in the joint angles, which is solved semigraphically to obtain the joint variables for the determination of the moving plate orientation. Examples are included to demonstrate the application of the method.     

多约束条件下的机器人时间最优轨迹规划

提出了一种工业机器人时间最优轨迹规划及控制的新方法。对于笛卡尔空间中给定路径上的离散路径点,通过运动学逆解求得与之对应的关节节点序列,采用三次样条插值方法构造各关节位移、速度、加速度均连续的轨迹。在考虑关节空间中速度、加速度、加加速度约束条件的同时,确保机器人在笛卡尔空间各离散路径点处满足由给定路径所决定的速度约束条件,减小机器人运动路径与给定路径之间的误差。采用序列二次规划法求解上述非线性约束优化问题,进而规划出沿特定曲线方程运动的机器人时间最优轨迹。最后将上述算法应用于剪带机器人,证明了该算法的有效性和可行性。     

6-3-3并联机构尺度的优化综合

提出了以满足6-3-3并联机构使用功能为准则的尺度综合优化建模方法,即以功能要求的任务轨迹为动平台运动规划路径,以尺度参数和任务轨迹在工作空间的定位参数为设计变量,以机构空间结构尽可能紧凑,而工作空间尽可能大为目标函数、工作空间涵盖任务轨迹、主动件移动范围和关节转角不超过设定极限值为约束,建立优化模型并通过软件编程实现该模型的求解。最后,给出了一个算例。     

6-SPS并联机器人的奇异位形分析

以并联机构在奇异位形下产生的微小位移与关节约束和结构约束的关系为基础,研究了具有重合球铰中心的6-3式和6-4式并联机构的奇异位形,分别得到这两种机构奇异位形的三阶和四阶判别行列式及奇异位形的特殊情形。最后给出瞬时运动的位移螺旋。     

3-RTT并联机器人奇异位形空间分析

采用基于机构瞬时运动分析的方法,建立了3—RTT并联机器人的奇异位形判别阵。分析了3—RTT机器人处于奇异位形时机构所满足的几何条件。编制了基于三维搜索算法的奇异位形空间分析程序,时实例进行搜索计算和分析,给出了3-RTT机器人的奇异位形空间的图形,并对其分布规律进行了分析。     

3-RRRT并联机器人工作空间与灵巧度的分析

旨在研究和分析3-RRRT并联机器人的工作空间和灵巧度。运用了齐次坐标系法对3-RRRT并联机器人机构进行了分析，给出属于工作空间点的判别条件，并进行了数值仿真；给出了3-RRRT并联机器人灵巧度的计算公式，并进行了数值仿真。     

并联机器人动态滑模轨迹跟踪控制研究

并联机器人是机器人研究与应用的重要部分,它具有刚度大、承载能力强、位置误差不积累等一系列优点,但它本身高度的非线性和强耦合}生,使对其精确控制极为困难.针对以交流伺服电机驱动的六自由度并联机器人机构,分析了其运动学逆解,进行了轨迹规划,设计了动态滑模变结构控制算法,建立了机器人支路的仿真模型,完成了对支路的期望运动轨迹的跟踪.仿真结果表明该算法系统抗干扰能力强,具有快速有效跟踪期望轨迹的优良性能.     

并联机构的六维鼠标研制开发

详细阐述了一种以并联机构为力敏元件的微型六维鼠标的设计与开发工作,分析了其设计思想和工作原理,阐述了在鼠标的力敏元件微型化方面所采取的措施,介绍了整个鼠标的系统构成,并将其用于虚拟6—SPS并联机器人控制系统中,控制结果表明该六维鼠标设计制造是成功的。     

Fuel optimal control of parallel hybrid electric vehicles

A mathematical model for fuel optimal control and its corresponding dynamic programming (DP) recursive equation were established for an existing parallel hybrid electric vehicle (HEV). Two augmented cost functions for gear shifting and engine stop-starting were designed to limit their frequency. To overcome the problem of numerical DP dimensionality, an algorithm to restrict the exploring region was proposed. The algorithm significantly reduced the computational complexity. The system model was converted into real-time simulation code by using MATLAB/RTW to improve computation efficiency. Comparison between the results of a chassis dynamometer test, simulation, and DP proves that the proposed method can compute the performance limitation of the HEV within an acceptable time period and can be used to evaluate and optimize the control strategy. __________ Translated from Journal of Shanghai Jiaotong University, 2006, 40(6): 947–951, 957 [译自: 上海交通大学学报]     

Developing the mechanisms of parallel structure with five degrees of freedom designed for technological robots

The paper deals with the problems of kinematic and force analysis of a technological robot with a parallel structure, which is a development of the well-known METROM scheme that corresponds to five degrees of freedom. In contrast to the prototype, this mechanism only has three kinematic chains, which leads to an increase in the working area due to a decrease in the possibility of mutual interference between the kinematic chains.     

Some investigations into development of nozzle and suction system for air blast shot peening machine

Shot peening is an important surface enhancement process, which helps in assuring satisfactory fatigue life and reliability of the automotive, aerospace and marine components. One of the most important factors affecting shot peening performance is the type of shot peening machine. This paper presents an innovative design of a laboratory-based air blast shot peening machine. This machine has a vertical nozzle suction system to take the advantage of gravity feed as well as the feed created by suction of the pressurized air. Special attention was paid to the design of the nozzle and the mixing chamber so as to obtain adequate suction of shots. The performance of the machine was evaluated by carrying out various shot peening tests on AISI 1045 steel specimens. The tests included microscopic examination of coverage with ×10 magnification lens, fatigue and wear resistance. The wear resistance of the peened AISI 1045 material increased by 3.5 times the unpeened one. The fatigue tests showed improvement in fatigue life of the workpiece up to about four times. Besides, there was an increase in yield and torsional strength of the workpiece by about 1.5 times.     

平面3-RRR并联机器人运动分析的计算机模拟逼近法

提出一种新的平面3自由度并联机器人运动分析方法,计算机模拟逼近法。运用该方法进行了速度和加速度分析。先采用CAD的几何约束、尺寸约束、尺寸方程和尺寸驱动技术,构造平面3—RRR3自由度机器人的模拟机构。再用两个相同且彼此靠近的平面3自由度机器人模拟机构,构造速度模拟机构,求解动平台上确定点的速度和角速度。最后用两个相同且彼此靠近的平面3—RRR机器人速度模拟机构,构造加速度模拟机构,求解动平台上确定点的加速度和角加速度。计算机模拟结果与解析法的结果比较表明,该方法具有简单、快捷、直观、求解精度高的优点,而且可以完成复杂机构的运动分析,为多自由度机构运动分析提供了更有效的工具。     

平面两自由度驱动冗余并联机器人的运动及灵巧性分析

研究一种平面两自由度驱动冗余并联机器人的运动学求解,同时探讨了该并联机器人机构的工作空间,并绘制了工作空间的各种形状,在此基础上分析了该并联机器人机构的灵巧性,利用特例在其工作空间内绘制了灵巧性性能图谱,这些图谱是该并联机器人的机构设计的重要参考依据。     

Delta机器人的尺度综合方法研究

尺度综合是并联机器人运动学设计的最终目标.为此,本文针对Delta机器人提出了一种最优尺度综合方法.首先对机构进行运动学分析得到局部灵活度的性能评价指标,其次将局部性能评价指标综合为全域性能指标,并将尺度综合问题归结为一类参数优化问题.上述方法对这类高速轻型并联机器人以及其它并联机构的运动学设计理论有一定指导意义.     

新型三坐标并联动力头工作空间分析

工作空间是并联构型装备性能评价的一项重要指标.基于逆运动学模型,给出新型三坐标并联动力头A3头的可达工作空间和灵活工作空间的定义,并根据工程实际限制,列出了杆长、关节转角、电主轴干涉和奇异性等约束条件,进而利用数值搜索法确定出满足约束条件的工作空间和灵活工作空间的边界,为动力头的详细结构设计提供了理论依据.