SHeRo: Scalable hexapod robot for maintenance,repair, and operations

Improper maintenance, repair, and operations of societal centric structures can lead to catastrophic failures that drastically affect global economy, the environment, and everyday life. Due to the remote, cramped and highly irregular environmental nature of these structures, routine manual procedures and operations can be rather tedious, dangerous, and hazardous for humans. Automating maintenance, repair, and operations removes human workers from having to crawl within highly cluttered and constrained spaces, breathing in stale air mixed with fumes from welding or particulate from repair work, and provides higher reliability and consistency in the repair work. This paper introduces SHeRo, a scalable hexapod robot designed for maintenance, repair, and operations within remote, inaccessible, irregular, and hazardous environments. The scalability of the design enhances traditional hexapod robot designs by incorporating two prismatic joints into each leg. A detailed discussion on the design and realization of SHeRo is provided. An analysis on the stability and workspace of SHeRo is presented and a dynamic criterion is developed to integrate the concepts of robot stability and constant orientation workspace into a stable workspace. The analytical solution of the lateral stable workspace of SHeRo is derived along with a metric for comparing stable workspace between different robot configurations. A simulated demonstration and two physical experimental demonstrations are presented showing the advantage of introducing scalability into the hexapod robot design along with the workspace enhancement and flexibility of the scalable hexapod robot.     

Ergonomic Analysis of Mobile Cart–Assisted Stocking Activities Using Electromyography

Workers in grocery stores are exposed to numerous musculoskeletal risks that can be reduced using assistive devices while performing stocking tasks. A regional grocery store has recently deployed a mobile cart without comprehension of its ergonomic impact on workers, which this article investigates using normalized electromyography data (%MVC). This article studies not only ergonomic impact based on %MVC values but also work performance represented by a muscle force metric (MFM). The results from this study showed highest muscle groups in %MVC and MFM were the erector spinae and triceps. Interestingly, muscle activations on erector spinae were reduced when mobile cart is used. %MVC and MFM distribution for value‐added‐ and non‐value‐added subtasks were slightly different, with larger differences observed for non‐value‐added tasks. Video recordings revealed higher work performance when the mobile cart is used. In future research, the number of participants will be increased to further validate the results from this study.     

On the position analysis of a new spherical parallel robot with orientation applications

In this paper, we propose a new spherical parallel robot for celestial orientation, and rehabilitation applications (TV satellite dish, tracking systems, solar panels, cameras, telescopes, table of the machine tools, ankle, shoulder, wrist and etc.). The proposed robot can completely rotate about an axis. After describing the robot and its inverse position analysis, using the genetic algorithm, the dimensional optimization to maximize the workspace of the robot is performed. The workspace analysis shows that the proposed robot has a relatively large workspace. Also, singularity analysis represents that the manipulator is a singularity-free workspace. It is a great advantage of the proposed robot. Next, an optimal approach is proposed for solving the direct position problem of the robot. According to the geometry of the robot, two coupled trigonometric equations are obtained through using a special form of Rodrigues' rotation formula. Next, the two coupled equations are transformed to a 8-degrees polynomial using the Sylvester's Dialytic elimination method. Finally, a numerical example for the robot with an asymmetric structure is given with eight real solutions. Therefore, the polynomial being minimal and the proposed approach is optimal. This greatly decreases computational time, which is necessary for dynamics, control and simulation.     

Numerical solution for designing telescopic manipulators with prescribed workspace points

In this paper a numerical solution is proposed for designing telescopic manipulators when workspace is prescribed through few suitable points. An algorithm is outlined by using an algebraic formulation for the workspace boundary and numerical solution is worked out by using a Newton–Raphson technique to solve a proper design problem. Numerical examples are reported to discuss computational efforts and solution characteristics.     

Workspace and statics analysis of 4-UPS-UPU parallel coordinate measuring machine

A novel 4-UPS-UPU spatial 5-Degree of freedom parallel coordinate measuring machine (PCMM) is presented. The workspace of the measuring machine is analyzed by using polar coordinate searching method. The force balance equation and statics transfer matrix of the measuring machine are established. The statics analysis of the 4-UPS-UPU PCMM is realized by taking the PCMM with load and no-load as example, and the numerical verification and virtual simulation verification of the results of driving force are carried out. The research can provide a theoretical basis for the optimal design and manufacturing of 4-UPS-UPU PCMM.     

3-PUU并联机构工作空间分析与优化

提出了一种新型3-PUU并联机器人,对该机器人进行运动学分析,得到了3-PUU并联机器人的运动学反解,在此基础上,分析了移动副和虎克铰对工作空间的限制。采用三维极限搜索法求解了工作空间,并对该并联机器人的工作空间进行了优化分析。结果表明:优化后的工作空间明显增大,该种机器人具有较好的实际应用前景。     

液压支架油缸内壁缺陷修复机械臂的运动学分析与仿真

针对矿用液压支架油缸内壁局部缺陷修复,设计一种能深入液压支架油缸筒内进行内壁修复的焊接机械臂。基于改进D-H参数建模方法,对设计的内表面修复焊接机械臂进行运动学建模,并求解了内表面修复焊接机械臂的正、逆运动学。借助MATLAB软件,采用蒙特卡洛法,对该焊接机械臂的有效工作空间进行了仿真分析,利用Robotics Toolbox工具箱对油缸内壁缺陷修复机械臂进行关节轨迹规划,通过仿真得到各关节的角位移、角速度、角加速度曲线。仿真结果表明：该机械臂运行平稳,轨迹连续,满足运动学要求。     

机构约束条件下Delta机器人工作空间建模与计算方法

为了简单快捷地计算带有机构约束的Delta并联机器人的工作空间,提出一种新的Delta并联机器人工作空间的数值算法,并在算法中加入了球铰、万向节等机构约束对Delta型并联机器人工作空间的影响。首先建立Delta并联机器人工作空间计算的理论数学模型,然后建立球铰、万向节机构的角度约束数学模型,最后利用MATLAB编程求解并用离散点作图表示以及进行实验验证。利用该算法可以计算带有机构约束的Delta并联机器人的工作空间,通过对自主开发的Delta并联机器人的操作分析,验证了该方法的有效性。     

一种新型3-RRRS六自由度并联机构的位置与作业空间分析

提出一种新型3-RRRS并联机构,进行了机构自由度、位置正反解、工作空间和灵活度研究.根据运动学逆解原理,建立了机构的位置反解方程,并利用参数代换建立了正解方程组.初步确定了机构作业空间的约束条件;同时求出了反映机构输入输出映射关系的雅可比矩阵.