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Parasitic rotation evaluation and avoidance of 3-UPU parallel mechanism

Haibo QU, Yuefa FANG, Sheng GUO

《机械工程前沿（英文）》 2012年第7卷第2期页码 210-218 doi: 10.1007/s11465-012-0317-4

摘要：

Based on the prototype of 3-UPU (universal-prismatic-universal joint) parallel mechanism proposed by Tsai [ ], the parasitic rotation evaluation is performed and calculated the bound of instability of SNU Seoul National University 3-UPU parallel mechanism. Through analysis of the terminal constraint system of the 3-UPU parallel mechanism, the equation about the parasitic rotation and limited clearance is presented. Then the norm of possible parasitic rotation is employed to evaluate the mechanism stability with limited clearance. The higher this number the worst is the pose, the lower it is the best it is. And the contour atlas of parasitic rotation is obtained, which can be used for further analysis and design. With the practice experiment result of SUN 3-UPU parallel mechanism, we find it’s bound of instability, which indicates there will appear the parasitic rotation when the number exceeds the bound. Finally, the method for avoidance of possible parasitic motions is presented by adding redundantly actuated limbs.

关键词： parallel mechanism 3-UPU (universal-prismatic-universal joint) parasitic motions limited clearance redundantly actuated limbs

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Cusp points and assembly changing motions in the PRR-PR-PRR planar parallel manipulator

《机械工程前沿（英文）》 2023年第18卷第2期 doi: 10.1007/s11465-022-0743-x

摘要： Most parallel manipulators have multiple solutions to the direct kinematic problem. The ability to perform assembly changing motions has received the attention of a few researchers. Cusp points play an important role in the kinematic behavior. This study investigates the cusp points and assembly changing motions in a two degrees of freedom planar parallel manipulator. The direct kinematic problem of the manipulator yields a quartic polynomial equation. Each root in the equation determines the assembly configuration, and four solutions are obtained for a given set of actuated joint coordinates. By regarding the discriminant of the repeated roots of the quartic equation as an implicit function of two actuated joint coordinates, the direct kinematic singularity loci in the joint space are determined by the implicit function. Cusp points are then obtained by the intersection of a quadratic curve and a cubic curve. Two assembly changing motions by encircling different cusp points are highlighted, for each pair of solutions with the same sign of the determinants of the direct Jacobian matrices.

关键词： planar parallel manipulator assembly changing motions cusp points quartic polynomial discriminant of repeated roots

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Self-motions of 3-RPS manipulators

Josef SCHADLBAUER, Manfred L. HUSTY, Stéphane CARO, Philippe WENGERY

《机械工程前沿（英文）》 2013年第8卷第1期页码 62-69 doi: 10.1007/s11465-013-0366-3

摘要：

Recently a complete kinematic description of the 3-RPS parallel manipulator was obtained using algebraic constraint equations. It turned out that the workspace splits into two components describing two kinematically different operation modes. In this paper the algebraic description is used to give a complete analysis of all possible self-motions of this manipulator in both operation modes. Furthermore it is shown that a transition from one operation mode into the other in a self-motion is possible.

关键词： 3-RPS-manipulator singularity self-motion

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Singularity loci of an orthogonal spherical two-degree-of-freedom parallel mechanism

Jialun YANG, Feng GAO,

《机械工程前沿（英文）》 2009年第4卷第4期页码 379-385 doi: 10.1007/s11465-009-0075-0

摘要： Singularity analysis plays an important role in the design of robots, especially for parallel robots. In this paper, the direct and inverse kinematics of an orthogonal spherical two-degree-of-freedom parallel mechanism is proposed based on the modified Euler angles. All the singular poses of the mechanism are achieved through the direct kinematic analysis. Self-motions, which are different from the general spherical 5 parallel mechanisms, are also discussed. Singularity loci in the joint space and Cartesian space are plotted according to the Jacobin of the mechanism. Result shows that the singularity loci at the joint space are two circles and one line, whereas at the Cartesian space are a circle.

关键词： 2-DOF orthogonal spherical parallel mechanism singularity loci self-motions

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Harvesting biomechanical energy in the walking by shoe based on liquid metal magnetohydrodynamics

Dan DAI, Jing LIU, Yixin ZHOU

《能源前沿（英文）》 2012年第6卷第2期页码 112-121 doi: 10.1007/s11708-012-0186-x

摘要： A liquid metal magnetohydrodynamics generation system (LMMGS) was proposed and demonstrated in this paper for collecting parasitic power in shoe while walking. Unlike the conventional shoe-mounted human power harvesters that use solid coil and gear mechanism, the proposed system employs liquid metal (Ga In Sn ) as energy carrier, where no moving part is requested in magnetohydrodynamics generators (MHGs). While walking with the LMMGS, the foot alternately presses the two liquid metal pumps (LMPs) which are respectively placed in the front and rear of the sole. As a result, the liquid metal in the LMPs (LMP I and II) is extruded and flows through the MHGs (MHG I and II) in which electricity is produced. For a comparison, three types of LMMGSs (LMMGS A, B and C) were built where all the parts are the same except for the LMPs. Furthermore, performances of these LMMGSs with different volume of injected liquid metal were tested respectively. Experimental results reveal that both the output voltage and power of the LMMGS increase with the volume of injected liquid metal and the size of the LMPs. In addition, a maximum output power of 80 mW is obtained by the LMMGS C with an efficiency of approximately 1.3%. Given its advantages of no side effect, light weight, small size and reliability, The LMMGS is well-suited for powering the wearable and implantable micro/nano device, such as wearable sensors, drug pumps and so on.

关键词： human energy harvesting liquid metal wearable magnetohydrodynamics generator parasitic power in shoe

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过程强化装置中双偏心转子的运动分析

朱瑞林,朱国林

《中国工程科学》 2012年第14卷第10期页码 90-96

摘要：

当偏心转子绕定轴旋转时，实际上只有其几何圆心作简谐振动（正/余弦运动），某些情况下由转子驱动的构件（如活塞）并不能作同样的简谐振动，因此在一些过程设备上应用双偏心转子时，会引起一些相关问题，如压力变化问题。为此，在分析一种过程强化装置中所采用的双偏心转子的运动规律的基础上，发现了由于偏心转子所驱动的两活塞的运动不完全对称，可能引起设备内介质压力变化的原因，并提出了相应的解决措施。

关键词：转子活塞简谐振动

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Fast forward kinematics algorithm for real-time and high-precision control of the 3-RPS parallel mechanism

Yue WANG, Jingjun YU, Xu PEI

《机械工程前沿（英文）》 2018年第13卷第3期页码 368-375 doi: 10.1007/s11465-018-0519-5

摘要：

A new forward kinematics algorithm for the mechanism of 3-RPS (R: Revolute; P: Prismatic; S: Spherical) parallel manipulators is proposed in this study. This algorithm is primarily based on the special geometric conditions of the 3-RPS parallel mechanism, and it eliminates the errors produced by parasitic motions to improve and ensure accuracy. Specifically, the errors can be less than 10^-6 . In this method, only the group of solutions that is consistent with the actual situation of the platform is obtained rapidly. This algorithm substantially improves calculation efficiency because the selected initial values are reasonable, and all the formulas in the calculation are analytical. This novel forward kinematics algorithm is well suited for real-time and high-precision control of the 3-RPS parallel mechanism.

关键词： 3-RPS parallel mechanism forward kinematics numerical algorithm parasitic motion

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A comprehensive analysis of a 3-P (Pa) S spatial parallel manipulator

Yuzhe LIU,Liping WANG,Jun WU,Jinsong WANG

《机械工程前沿（英文）》 2015年第10卷第1期页码 7-19 doi: 10.1007/s11465-015-0324-3

摘要：

In this paper, a novel 3-degree of freedom (3-DOF) spatial parallel kinematic machine (PKM) is analyzed. The manipulator owns three main motions (two rotations and one translation) and three concomitant motions (one rotation and two translations). At first, the structure of this spatial PKM is simplified according to the characteristic of each limb. Secondly, the kinematics model of this spatial PKM is set up. In addition, the relationship between the main motions and concomitant motions is studied. The workspaces respectively based on the outputs and inputs are derived and analyzed. Furthermore, the velocity model is put forward. Two indexes based on the velocity model are employed to investigate the performance of this spatial PKM. At last, the output error model can be obtained and simulated. The comprehensive kinematics analysis in this paper is greatly useful for the future applications of this spatial PKM.

关键词： parallel mechanism concomitant motions kinematics workspaces error model

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Analysis and design of pulse frequency modulation dielectric barrier discharge for low power applications

Tang-tang GUO,Xing-liang LIU,Shi-qiang HAO,Chi ZHANG,Xiang-ning HE

《信息与电子工程前沿（英文）》 2015年第16卷第3期页码 249-258 doi: 10.1631/FITEE.1400185

摘要： For low power dielectric barrier discharge (DBD) used in small-size material treatment or portable devices, highstep transformer parasitic capacitance greatly influences the performance of the resonant converter as it is of the same order of magnitude as the equivalent capacitance of DBD load. In this paper, steady-state analysis of the low power DBD is presented, considering the inevitable parasitic capacitance of the high-step transformer. The rectifier-compensated first harmonic approximation (RCFHA) is applied to linearize the equivalent load circuit of DBD at low frequency and the derived expressions are accurate and convenient for the analysis and design of the power supply. Based on the proposed linear equivalent load circuit, the influence of transformer parasitic capacitance on the key parameters, including the frequency range and the applied electrode voltage, is discussed when the power is regulated with pulse frequency modulation (PFM). Also, a design procedure is presented based on the derived expressions. A prototype is constructed according to the design results and the accuracy of the design is verified by experimental results.

关键词： Dielectric barrier discharge Rectifier-compensated first harmonic approximation Parasitic capacitance Power converter design