Development of a redundant anthropomorphic hydraulically actuated manipulator with a roll–pitch–yaw spherical wrist

The demand for redundant hydraulic manipulators that can implement complex heavy-duty tasks in unstructured areas is increasing; however, current manipulator layouts that remarkably differ from human arms make intuitive kinematic operation challenging to achieve. This study proposes a seven-degree-of-freedom (7-DOF) redundant anthropomorphic hydraulically actuated manipulator with a novel roll–pitch–yaw spherical wrist. A hybrid series–parallel mechanism is presented to achieve the spherical wrist design, which consists of two parallel linear hydraulic cylinders to drive the yaw/pitch 2-DOF wrist plate connected serially to the roll structure. Designed as a 1R PRRR-1S PU mechanism (“R”, “P”, “S”, and “U” denote revolute, prismatic, spherical, and universal joints, respectively; the underlined letter indicates the active joint), the 2-DOF parallel structure is partially decoupled to obtain simple forward/inverse kinematic solutions in which a closed-loop subchain “R PRR” is included. The 7-DOF manipulator is then designed, and its third joint axis goes through the spherical center to obtain closed-form inverse kinematic computation. The analytical inverse kinematic solution is drawn by constructing self-motion manifolds. Finally, a physical prototype is developed, and the kinematic analysis is validated via numerical simulation and test results.     

基于避障准则的双臂手移动机器人桁架内运动规划

针对桁架内移动的避障要求,研究双臂手移动机器人桁架内运动的规划方法。基于状态空间模型提出直角坐标空间下的六面心、八边心和八顶点搜索算法,避免了C空间内复杂度呈几何级数增长的问题,实现了末端无碰撞路径搜索。建立双臂手移动机器人三节臂的平面内避障准则,解决了机器人在桁架内运动时机器人臂与桁架杆的碰撞问题。根据平面内避障准则和臂形标志,求得了各个关节角的解析解,解决了数值解的不封闭问题。每个时刻末端姿态由通用旋转变换公式线性插值得到,在Matlab中仿真双臂手移动机器人桁架内的运动,验证了双臂手移动机器人在桁架内运动时避障方法的可行性。     

Estimating muscle fatigue of the biceps brachii using high to low band ratio in EMG during isotonic exercise

The principal objective of this study was to estimate biceps brachii muscle fatigue using the fatiguing time (FT) and the initial slope (S_init) of the high to low frequency band ratio (H/LFB) in EMG during isotonic exercise until the endurance time (ET) at which the subject could no longer follow the fixed speed. Surface EMG was measured on the biceps brachii muscle of ten subjects (5 males and 5 females) as the subject performed repetitive elbow contraction tasks. The first task was with no load (“no load” task). The other tasks were performed until exhaustion (“load” task) with a load weighted at 10%, 20% and 30% of the subject’s maximum voluntary contraction (MVC). We extracted decreasing parameters of the EMG, such as median frequency (MDF) and three types of H/LFB (H1; 95∼500Hz, H2; 150∼350Hz, H3; 470∼500Hz and LFB; 15∼45Hz). Statistical analysis was conducted to select an appropriate parameter. The FT was defined as the time at which the selected H/LFB became smaller than the threshold (50% at 10% MVC, 60% at 20% MVC, and 65% at 30% MVC) with respect to the initial value, and S_init was defined as the slope of the linear regression line using H/LFB from the onset of exercise to FT. In order to predict ET, we proposed using an analytical method that employed a multiple linear regression model with two independent variables, FT and S_init. The results from this novel model were compared with those of previously established methods. In the “no load” task, there was no FT in the MDF and three H/LFBs. In the “load” task, the MDF and three H/LFBs gradually decreased, but the H3/LFB decreased most rapidly. A significant difference between the “no load” task and the “load” task at a 95% significant level was only observed in H3/LFB. ETs of all subjects were predicted at an error of approximately 30.4%. This error was better than that obtained using other methods (34.8% by Mathiassen’s method, 39.7% by Ma?setti’s method). FT detected from H3/LFB was a useful indicator to distinguish the EMG in the “load” task from that observed in the “no load” task, and the ET of a subject could be predicted using FT and S_init. Therefore, the H3/LFB provides more information on muscle fatigue than the other features under isotonic conditions, and may be suited to specific experimental protocols in workplace fatigue studies.     

基于DMP的双臂机器人装配策略研究

针对双臂机器人装配规划难题,提出了基于动态运动基元的双臂协调运动和装配策略.首先,分析双臂机器人运动空间,建立双臂运动约束模型,使每条手臂不仅满足自身任务要求,还满足双臂之间的相对位姿约束,然后将双臂之间的相对位姿约束与动态运动基元方法结合,使得生成的机械臂运动轨迹可以达到自避障的效果.其次,根据装配任务需求,分析双臂...     

基于人体动作姿态识别的机器人仿人运动*

以关节式机器人为对象,进行机器人仿人运动研究。从人体动作姿态识别、人-机动作映射、机器人运动控制等方面,详细阐述机器人仿人运动算法。提出人体动作姿态识别方法,利用Kinect传感器捕获人体运作的关节点位置信息,在建立人体基准坐标系的基础上,为了得到描述肩、肘运动的动作信息,计算人体手臂动作的关节角度,实现人体动作姿态的识别。在分析人体肩、肘等关节和机器人机构差异性的基础上,建立人体手臂与四自由度机械手臂的人-机动作映射规则。针对机器人自由度较少,无法完全复现人体运动的情形,分析、比较不同控制策略的优缺点和适用性,寻求适合机器人操作的复现控制策略。关节式机器人接收运动控制指令,执行相应的关节运动,从而实现机器人仿人运动。相关试验验证了人体动作姿态识别和机器人仿人运动控制算法的有效性。研究成果对于提高机器人控制和操作的简单易用性、提高人机交互能力具有借鉴意义,对于扩展机器人应用领域具有实践意义。     

欠驱动余度机械臂的无碰撞运动规划与控制

基于周期运动的非线性动力学分析,发现欠驱动机械臀在小幅振动输入条件下有运动漂移现象,即当欠驱动机械臂的主动关节小幅振动时,被动关节的平衡位置将发生漂移。基于这一现象提出了被动关节位置控制的余弦函数小振幅控制方法:把人工势场方法引入冗余度机械臂的避障运动规划,提出了欠驱动冗余度机械臂的虚拟模型运动规划方法:把以上两种方法有机结合,提出了一种欠驱动冗余度机械臂的避障运动规划和控制方案,对平面三连杆欠驱动机械臂进行了仿真,仿真结果表明这一方法是可行的。     

Manipulability analysis of underwater robotic arms on ROV and application to task-oriented joint configuration

This paper describes the task-oriented manipulability of tele-operated robotic arms mounted on a remotely operated vehicle (ROV) and its application to task-oriented joint configurations. The main purpose of the study is to reduce the tele-operator’s burden in performing underwater tasks by enhancing the functionality of the manipulator. Even though a manipulator has 6 degrees-of-freedom (DOF), which is proper DOF to work in Cartesian workspace, the manipulator might have redundancy according to task types and order of task-priority. This paper focuses on the problem to utilize the redundancy by introducing a scalar function as an object of optimization. The scalar function is composed of a taskoriented manipulability measure (TOMM) and joint limit measure (JLM). Using sequential quadratic programming (SQP) with the object function, we obtained optimal postures of the manipulator for a given position constraint of the end-effecter. Adopting the scalar function as a performance index, we solved a redundancy resolution problem based on the pseudo inverse of the task-oriented Jacobian matrix.     

Online qualitative nugget classification by using a linear vector quantization neural network for resistance spot welding

Real-time estimation of weld quality from process data is one of the key objectives in current weld control systems for resistance spot-welding processes. This task can be alleviated if the weld controller is equipped with a voltage sensor in the secondary circuit. Replacing the goal of quantifying the weld quality in terms of button size by the more modest objective of indirect estimation of the class of the weld, e.g., satisfactory (acceptable, “normal” button size), unsatisfactory (undersized, “cold” welds), and defects (“expulsion”), further improves the feasibility of the mission of indirect estimation of the weld quality. This paper proposes an algorithmic framework based on a linear vector quantization (LVQ) neural network for estimation of the button size class based on a small number of dynamic resistance patterns for cold, normal, and expulsion welds that are collected during the stabilization process. Nugget quality classification by using an LVQ network was tested on two types of controllers; medium-frequency direct current (MFDC) with constant current controller and alternating current (AC) with constant heat controller. In order to reduce the dimensionality of the input data vector, different sets of features are extracted from the dynamic resistance profile and are compared by using power of the test criteria. The results from all of these investigations are very promising and are reported here in detail.     

基于形状变化的冗余机械手可操作性分析

受冗余机械手的可操作性理论和可操作性椭圆的启发,提出形状变化可操作性理论和形状变化可操作性椭圆。可操作性表示了冗余机械手在形状给定的前提下,它的每一个关节产生速度的性能;形状变化可操作性表示了当冗余机械手的手臂末端被给定任务时,其余中间关节产生速度的性能,即是形状变化性能,手臂末端执行给定的任务,如轨道追踪,因此不具备形状变化可操作性。对可操作性椭圆和形状变化可操作性椭圆进行比较和分析。通过对七关节机械手在二维平面内的轨道追踪和障碍物回避的实例分析、以及对三维空间内的不同姿势(即不同形状)下的七关节机械手所对应的不同形状变化可操作性椭圆的比较分析,能够认识到形状变化可操作性理论的提出对于评估和设计冗余机械手的结构和形状有着重要的实际意义。     

双臂机器人轴孔装配的分级控制

设计了双臂协调进行轴孔装配的分级控制器。该控制器由管理级和执行级组成,管理级在进行主臂的期望运动路径规划的同时,根据采样到的主臂信息,对从臂进行期望关节运动角的递推,而执行级只需执行管理级输出的期望值。执行级的控制方式与普通单臂机器人控制方式一样。仿真结果表明所设计的分级控制器能顺利完成双臂的协调轴孔装配作业。     

一种面向航天需求的仿生柔性机械臂的设计

针对航天器舱内环境的障避实际需求,基于自然界象鼻的内部肌肉结构分布特点,设计一种多冗余自由度仿生柔性机械臂。该机械臂由8个柔性关节组成,每个柔性关节具有3个自由度,相比传统机械臂,具有结构紧凑、刚度较高、运动灵活、操作空间广泛等特点。针对所提出的单个柔性关节与多个关节组成的仿生柔性机械臂进行运动学建模分析。利用制作的仿生柔性机械臂,进行航天避障任务试验,验证了该机械臂结构的可行性。     

Design and static performance of high speed machining centre with “direct drive”

“Direct drive” is an ideal method for speeding machine tools. In the structure of a CNC machining centre with “direct drive”, the linear motor’s primary and secondary parts are assembled into the worktable and machine bed respectively to directly drive the worktable. The built-in rotary motor is assembled in the spindle to realize the main transmission system of the machine tool “direct drive”. All mechanical transmission elements in machine tools are eliminated. High speed, efficiency, and accuracy are easily obtained. However, in this type of “direct drive” machining centre, the magnetic attraction force between the primary and the secondary linear motors and the dynamic impact at acceleration and deceleration are directly imposed on the machine tool, and influence the performance of the machining centre. This paper analyzes the special demands of “direct drive” on the machine centre, and introduces a new structure of the machining tool. The worktable and machine bed are optimized to meet the special demands of “direct drive”. Static performance simulation on the machining centre is done to reveal an ideal result.     

新型送料机械手及其工作空间分析

设计了一种用于冲压生产线的新型送料机械手。该机械手由大臂、小臂和端拾器依次串联而成,其中大臂为六自由度6-PSS并联机构构型,小臂即延长臂为一个直线移动机构。绘制了机械手的工作空间,分析了该机械手主要几何参数对其工作空间大小的影响规律,根据两压机间送料的要求,选取了机械手的几何参数,并设计了该机械手的虚拟样机。该机械手具有横向移动速度快和工作空间大等特点,可用于冲压线上工件的输送或现代工业其他送料场合。     

A Further Discussion on Trends in the Development of Advanced Manufacturing Technology

This paper is a supplement to “Trends in the Development of Advanced Manufacturing Technology” (Yang and Wu in Chin. J. Mech. Eng., 39: 73, 2003) but delves deeper into it. It first points out the strategic status of manufacturing industry in state development. Then, a detailed analysis is given on the features and trends in the development of advanced manufacturing technology in a total of 12 points from three aspects: “precision,” “extreme,” and “culture” from the aspect of the product itself; “green,” “rapidness,” “saving,” and “efficiency” during the manufacturing process; and “digit,” “auto,” “integration,” “networking,” and “intelligence” in view of the manufacturing method. In addition, it emphasizes that all the above aspects should be based on two base points: “manufacture” and “machinery.” Finally, it puts forth the guiding ideologies for the development of advanced manufacturing technology and the aspects China should give priority to in development, while stressing on the principles of independence, innovation and “human orientation.”     

柔性关节机械臂避障路径自动控制数学建模

针对柔性关节机械臂在避障完成后位姿与目标位姿存在一定偏差的问题,提出柔性关节机械臂避障路径自动控制数学建模方法。将五次B样条曲线作为柔性关节机械臂避障路径规划的基础,在避障任务中引入速度修正项,通过关节角和关键点避障速度确定速度修正项取值。建立避障路径自动控制数学模型,利用该模型控制柔性关节机械臂在到达目标位置过程中实现障碍物精准规避,完成柔性关节机械臂避障路径自动控制。实验结果表明,所提方法能够减小位姿误差,平稳关节波动,实际应用效果较好。     

线驱动拟人臂机器人逆向运动学分析

基于最新人臂仿生理论和并联机器人研究的成果,提出一种线驱动7-DOF冗余手臂的设计方案.线驱动机构具有高刚度、高精度、高负载能力的优点,可以克服常规串联机构的缺点.介绍这种新型线驱动拟人臂机器人具体的结构,利用旋量理论描述机器人运动,在绳索张力条件的约束下,分析肩关节的工作空间.针对7-DOF机器人的逆运动学求解问题,先采用关节速度再分配法求关节速度逆解;然后与Paden-Kahan子问题法相结合,取得具有冗余控制的位置逆解,求出在给定位姿时各关节角的角度;再由关节角与绳长的关系解出各关节处驱动绳索的长度,并分析肩关节运动对腕、肘关节的耦合影响.最后在ADAMS下进行仿真,采用直线插补算法,动画图形实时显示机器人的运动情况,证明逆向运动学算法的正确性.     

变电站轮式巡检机器人机械臂避障路径规划方法

变电站工作环境特殊且复杂,为保证巡检机器人在执行巡检任务的同时,能更好、更安全地进行作业,提出面向轮式巡检机器人的机械臂避障路径规划方法。利用八叉树结构建模技术,架构巡检机器人工作环境的三维模型与环境更新模型。确定机械臂与环境关系,建立机械臂运动学模型,根据末端执行器位姿的已知与未知情况,完成运动学模型的正解与反解计算。基于关节位姿的三维坐标,设定机械臂连杆不碰撞障碍物为必要条件,依据六次多项函数式解得的关节角速度与角加速度连续轨迹,通过更改非固定参数值,调整机械臂的移动轨迹,最后,利用贝塞尔曲线平滑处理路径。仿真试验结果表明,所提方法路径精度更优越,避障效果更理想,符合变电站巡检的实时性需求。     

基于非线性微分方程的机械臂运动位置控制方法

针对当前机械臂运动位置控制方法存在机械臂关节节点位置的跟踪效果差和机械臂运动位置控制能力差的问题,提出基于非线性微分方程的机械臂运动位置控制方法。首先对机械臂动力学进行分析,获取内部三连杆结构作用原理和机械臂动力学目标函数,再利用坐标求权矩阵重构机械臂动力学目标函数,获取机械臂相关的非线性微分方程,将非线性微分方程的输出结果,即机械臂动力学参数代入 CPG 神经网络中,构建机械臂运动控制模型。实验结果表明,所提方法的械臂关节节点位置跟踪效果好、机械臂运动位置控制能力强。     

柔性机器人动力奇异问题的研究

对柔性机器人的动力奇异问题进行了研究。首先分析了柔性机器人产生动力奇异的原因,确定了激振力的方向、激振力的大小、阻尼的大小、在共振区间内激振力频率与机器人固有频率的相对变化速度以及机器人固有频率的大小是影响动力奇异的因素;然后提出了机器人动力奇异的判定依据和避免动力奇异的措施;最后以一末杆为柔杆的空间三杆机器人为例,验证了理论分析的正确性。     

一种七自由度机械臂的研制

冗余度机器人相比较非冗余度机器人具有消除不可避免的奇异位形、躲避任务空间障碍、克服关节运动极限等优点。介绍设计了一种新型的七自由度机械臂,其结构设计是在6R机械臂的基础上增加一个自由度,是一种典型的冗余度机械臂。阐述了该机械臂的结构设计标准,并在此基础上构建各连杆坐标系,计算了主要部件的转动惯量并据此选择了电机和谐波减速器,最后在有限元分析软件ANSYS中对关键部件进行了有限元分析。仿真结果表明,所设计的部件性能达到设计要求。