具有耦合分支的两转动两移动并联机构分析与优化

提出了具有耦合分支的两转动两移动并联机构。基于李群理论分析了机构自由度,该机构动平台能输出两个转动运动和两个移动运动;采用闭环矢量法对机构进行了位置分析,求得位置反解;通过速度分析得到机构的雅可比矩阵,在雅可比矩阵基础上对机构的奇异位形进行了分析;采用虚功原理建立了机构的刚度模型,并进行了刚度性能分析;为消除内部奇异产生的刚度退化,在机构上增加了冗余驱动分支,并对添加冗余驱动分支前后机构的刚度、工作空间等性能进行了对比分析。以工作空间内刚度平均值为目标对冗余驱动机构进行了尺度优化设计,结果表明,优化后的冗余驱动机构的刚度性能得到明显提升。

连续体并联抓取机器人的结构设计及运动学分析

为扩大并联机构在抓取操作领域的应用,提出一种非刚性的连续体并联抓取机器人,并对其进行了结构设计及运动学分析.相较于传统的刚性并联机器人,连续体并联抓取机器人以弹性杆式的连续体结构作为运动支链,具有更高的运动柔顺性;末端抓取装置采用远程驱动,使机器人在结构上更具轻量化.运用等效D-H法建立了机器人的运动学模型,求解了正、逆解及雅克比矩阵,并利用Matlab绘制其工作空间.在三维建模的基础上,利用Adams进行了机器人虚拟样机的运动学仿真.结果表明:三自由度的连续体并联抓取机器人具有较大的工作空间和良好的运动性能,能够实现大范围抓取操作任务.

基于仿人并联手指机构的机器人灵巧手设计与性能研究

为满足工业上对机器人灵巧手灵巧度高、承载能力强和精度高的要求,提出一种具有2T1R运动类型的仿人并联手指机构,并设计一种基于仿人并联手指机构的机器人灵巧手.对并联手指机构进行了自由度、运动学的分析,并用Adams对运动学分析进行了验证;利用机构的约束条件,确定了并联手指机构的工作空间;根据所建立的雅克比矩阵,研究了并联手指机构的奇异性与灵巧性,分析了力的传递性质;建立了灵巧手的抓取模型,分析了灵巧手协调操作的自由度、运动学和空间.通过研究分析,验证了灵巧手可行性与实用性,运动及性能方面可以满足工业生产的需求.

基于功能仿生并联机械腿的全向步行机器人

基于运动功能仿生设计了一种新型三自由度耦合并联机械腿并且应用到足式全向步行机器人当中,并对机器人整机性能进行了研究分析.首先,建立了运动学模型,应用几何法分析了运动学正逆解,利用逆解搜索法得到了可达工作空间.然后,采用虚功原理计算了驱动关节静力矩,规划了四足机器人的全向步态和足端轨迹.最后,完成了虚拟样机仿真分析并制作了原理样机,进行了样机的步态实验.通过分析可知:机构具有良好的稳定性和加速度连续性,其足端具有2R1T三自由度的运动特性;全向运动可以有效地解决在空间受限制的情况下无法完成转向的问题.

基于并联手指结构的多功能灵巧手的设计与研究

为满足工业生产对机器人末端夹持器灵巧性和承载能力的要求,设计了一种基于并联手指结构的多功能灵巧手。对手指机构的运动学、工作空间、奇异性进行了分析,对灵巧手的承载能力进行优化,并通过ADAMS仿真进行了验证。样机实验说明灵巧手具有理想的工作空间和较好的自适应性,可以实现对不同形状物体的随形抓取,适应柔性化工业生产的要求。

Multi-objective Optimization of a Parallel Ankle Rehabilitation Robot Using Modified Differential Evolution Algorithm

Dimensional synthesis is one of the most difficult issues in the field of parallel robots with actuation redundancy. To deal with the optimal design of a redundantly actuated parallel robot used for ankle rehabilitation, a methodology of dimensional synthesis based on multi-objective optimization is presented. First, the dimensional synthesis of the redundant parallel robot is formulated as a nonlinear constrained multi-objective optimization problem. Then four objective functions, separately reflecting occupied space, input/output transmission and torque performances, and multi-criteria constraints, such as dimension, interference and kinematics, are defined. In consideration of the passive exercise of plantar/dorsiflexion requiring large output moment, a torque index is proposed. To cope with the actuation redundancy of the parallel robot, a new output transmission index is defined as well. The multi-objective optimization problem is solved by using a modified Differential Evolution（DE） algorithm, which is characterized by new selection and mutation strategies. Meanwhile, a special penalty method is presented to tackle the multi-criteria constraints. Finally, numerical experiments for different optimization algorithms are implemented. The computation results show that the proposed indices of output transmission and torque, and constraint handling are effective for the redundant parallel robot; the modified DE algorithm is superior to the other tested algorithms, in terms of the ability of global search and the number of non-dominated solutions. The proposed methodology of multi-objective optimization can be also applied to the dimensional synthesis of other redundantly actuated parallel robots only with rotational movements.

Theory of Degrees of Freedom for Parallel Mechanisms with Three Spherical Joints and Its Applications

The analysis of degrees of freedom（DOF） of a moving platform is the fundamental problem in kinematics of parallel mechanism. However, many problems should be considered to correctly perform the DOF calculation by using the traditional DOF criterion, and it is difficult to find a DOF criterion suitable for all kinds of mechanisms. A rule that can be used to determine the position and orientation of the moving platform is presented. Based on the proposed rule, a new form of DOF criterion is proposed, which is suitable for a class of parallel mechanisms with three spherical joints attached to the moving platform. The basic types of generalized limb structures are given based on the possible dimension of achieving the center of spherical joint attached to the moving platform, and the general steps of analyzing the DOF are presented. This proposed formula simplifies the DOF analysis of parallel mechanisms with spherical joints attached to the moving platform, and plays an important role in structural synthesis of such parallel mechanisms.

Structural Synthesis of a Class of 2R2T Hybrid Mechanisms

Conventional overconstrained parallel manipulators have been widely studied both in industry and academia,however the structural synthesis of hybrid mechanisms with additional constraints is seldom studied,especially for the four degrees of freedom（DOF） hybrid mechanisms.In order to develop a manipulator with additional constraints,a class of important spatial mechanisms with coupling chains（CCs） whose motion type is two rotations and two translations（2R2T） is presented.Based on screw theory,the combination of different types of limbs which are used to construct parallel mechanisms and coupling chains is proposed.The basic types of the general parallel mechanisms and geometric conditions of the kinematic chains are given using constraint synthesis method.Moreover,the 2R2T motion pattern hybrid mechanisms which are derived by adding coupling chains between different serial kinematic chains（SKCs） of the corresponding parallel mechanisms are presented.According to the constraint analysis of the mechanisms,the movement relationship of the moving platform and the kinematic chains is derived by disassembling the coupling chains.At last,fourteen novel hybrid mechanisms with two or three serial kinematic chains are presented.The proposed novel hybrid mechanisms and construction method enrich the family of the spatial mechanisms and provide an instruction to design more complex hybrid mechanisms.

Reconfigurable parallel mechanisms with planar five-bar metamorphic linkages

This paper presents the idea of constructing reconfigurable limbs by integrating metamorphic linkages as subchains.The planar five-bar metamorphic linkages that have three phases resulting from locking of motors are considered.Under the assumption that the constraint exerted by the reconfigurable limb can switch between no constraint,a constraint force,and a constraint couple,the output motions of the metamorphic linkage in its two planar four-bar linkage phases are identified.By adding an appropriate joint to planar four-bar linkages with translational output,four planar five-bar linkages that can be employed in the construction of reconfigurable limbs are enumerated.Serial chains that can provide a constraint couple and a constraint force are synthesized based on screw theory.Reconfigurable limbs that have three configurations associated with the three distinct phases of the metamorphic linkages are assembled with planar five-bar metamorphic linkages and serial chains with four degrees of freedom.A class of reconfigurable parallel mechanisms are constructed by connecting a moving platform and a base with three identical reconfigurable limbs.The degrees of freedom of the reconfigurable parallel mechanism in different configurations with the metamorphic linkages in different phases are given.Finally,the actuation scheme for this kind of mechanisms is addressed.