实现高载荷下机翼前缘形状变化的柔性机构优化设计

为使柔性机构在高载荷作用下能实现预期的形状变化,提出了柔性机构的二次优化设计方法。以柔性机构的变形边界与目标边界间的最小平方差(LSE)为优化目标。采用遗传算法(GA),对柔性机构进行全局优化,求得其初始拓扑解;再采用约束随机探索法进行二次优化,求得柔性机构尺寸的精确解。以柔性机构实现机翼前缘形状变化问题为例,运用MATLAB7.1进行编程计算。结果表明,通过对GA初始拓扑解的二次优化,最小平方差下降了31.48%。最后运用ANSYS验证其变形结果基本一致。     

基于连续蚁群算法的3-RPS并联机构正解

为了避免传统数值方法求解并联机构正解问题的弊端,提出了一种将并联机构正解问题转化为目标函数优化问题的求解方法。并联机构正解的核心问题是求解一组多元耦合非线性方程组,以此为依据建立了并联机构正解的目标函数优化模型,并提出了一种简单的连续蚁群算法来求解该优化模型。以求解3-RPS并联机构正解为例进行了仿真分析。结果表明,该算法具有良好的全局寻优功能,能够避免初始值和局部极小值对计算结果的影响,不用计算雅可比矩阵及其逆阵,且计算精度满足并联机构正解的要求。     

Type Synthesis of 1T2R Parallel Mechanisms Using Structure Coupling-Reducing Method

Direct kinematics with analytic solutions is critical to the real-time control of parallel mechanisms.Therefore,the type synthesis of a mechanism having explicit form of forward kinematics has become a topic of interest.Based on this purpose,this paper deals with the type synthesis of 1T2R parallel mechanisms by investigating the topological structure coupling-reducing of the 3UPSUP parallel mechanism.With the aid of the theory of mechanism topology,the analysis of the topological characteristics of the 3UPSUP parallel mechanism is presented,which shows that there are highly coupled motions and constraints amongst the limbs of the mechanism.Three methods for structure coupling-reducing of the 3UPSUP parallel mechanism are proposed,resulting in eight new types of 1T2R parallel mechanisms with one or zero coupling degree.One obtained parallel mechanism is taken as an example to demonstrate that a mechanism with zero coupling degree has an explicit form for forward kinematics.The process of type synthesis is in the order of permutation and combination;therefore,there are no omissions.This method is also appli cable to other configurations,and novel topological structures having simple forward kinematics can be obtained from an original mechanism via this method.     

二维微执行器几何非线性拓扑优化设计与试验

多自由度柔顺机构在微动精密定位和精密操作等领域有广泛的应用,并且柔顺机构拓扑优化后所得机构都是锯齿状跳跃边界的几何图像,不能直接应用于工程实际,因而对多自由度柔顺机构拓扑优化、提取与试验研究就显得十分必要。基于此,以二维微执行器为例,进行多自由度柔顺机构几何非线性拓扑优化、拓扑图提取与试验研究。首先,给出了考虑耦合抑制输出的多输入多输出柔顺机构几何非线性拓扑优化数学模型及优化算法。其次,针对柔顺机构性能特点,给出了一种拓扑提取方法。提取过程包括灰度图像二值化、密度等值线方法边界近似和曲线重构三个部分。最后,以二维微执行器为基础,采用线切割加工工艺,研制了二维微执行器原型,并对其位移性能进行了试验测试,结果表明,该二维微执行器试验结果与理论分析结果基本吻合,达到了设计要求,同时也验证了所提方法的有效性。     

Workspace optimization and kinematic performance evaluation of 2-DOF parallel mechanisms

This paper presents the kinematics and workspace optimization of the two different 2-DOF (Degrees-of-Freedom) planar parallel mechanisms: one (called 2-RPR mechanism) with translational actuators and the other (called 2-RRR mechanism) with rotational ones. First of all, the inverse kinematics and Jacobian matrix for each mechanism are derived analytically. Then, the workspace including the output-space and the joint-space is systematically analyzed in order to determine the geometric parameters and the operating range of the actuators. Finally, the kinematic optimization of the mechanisms is performed in consideration of their dexterity and rigidity. It is expected that the optimization results can be effectively used as a basic material for the applications of the presented mechanisms to more industrial fields.     

基于约束函数的变胞机构变胞方程

变胞机构拥有多个变换的稳态和变胞态,其拓扑构态描述与分析是变胞机构结构学的难点。采用数学分析方法,探索全面、简便而准确地描述和分析变胞机构构态拓扑结构的问题。根据运动副约束的特征,定义反映运动副类型、级别、自由度、方位、性质及其随时间变化情况等诸多特征信息的参数——运动副约束函数,采用矩阵法构建以约束函数为元素的机构变胞源运动链邻接矩阵。针对合并构件、分离构件、改变构件性质、新增运动副、消除运动副及改变运动副性质等六类机构变胞方式,分别定义相应的机构变胞函数和变胞矩阵,建立相邻稳态之间变胞态的机构变胞方程。应用实例表明,所定义的运动副约束函数、运动链邻接矩阵、变胞矩阵和变胞函数等概念能简便、广泛地描述变胞机构的构态特征,基于约束函数的机构变胞方程能准确地描述和分析机构相邻稳态之间变胞态的变换过程,为变胞机构的结构分析提供一种新的途径和方法,并为进一步的变胞机构运动学和动力学分析以及机构综合研究提供理论基础。     

基于转动约束策略的柔顺机构拓扑优化

柔顺机构在航天航空、生物医疗、及仿生机器人等高新科技领域的精密微机械系统中拥有巨大的应用潜力。目前,拓扑优化是柔顺机构构型设计的主要方法之一。为了解决传统柔顺机构拓扑优化设计中存在虚铰的问题,首先,将旋转角引入柔顺机构构型设计中,以旋转角为观测指标,分析拓扑优化结果中存在虚铰的原因。其次,通过约束设计域内的旋转角平方的平均值不超过许用值,建立无铰链式柔顺机构拓扑优化模型,并且利用伴随法推导与之相应的灵敏度分析列式。最后,采用反向位移机构与柔性夹钳这两个经典算例的拓扑优化设计验证了所提优化模型的可行性和有效性。研究结果表明：基于转动约束策略获得的具有类桁架构型无铰链式柔顺机构,虽然在输入位移与输出位移方面表现出一定程度的减少,但避免了局部应变过大、应力集中问题的出现。     

FORWARD KINEMATICS ANALYSIS FOR A NOVEL 5-DOF PARALLEL MECHANISM USING TETRAHEDRON CONFIGURATIONS

Forward kinematics analysis of a novel 5-DOF parallel mechanism using tetrahedron configurations is presented. Such mechanism is suitable to many tasks requiring less than 6 DOFs. It consists of a movable platform connected to the base by five identical 6-DOF active limbs plus one active limb with its DOF being exactly the same as the specified DOF of the movable platform, which leads to its legs' topology 4-UPS/UPU. Based on the tetrahedron geometry, both closed-form solution with an extra sensor and numerical method using iterative algorithm are employed to obtain the forward kinematics solutions of the mechanism. Compared with the conventional methods, the proposed closed-form solution has the advantages in automatically avoiding unnecessary complex roots and getting a unique solution for the forward kinematics. Finally, an example shows that the proposed numerical algorithm is so effective that it enables a real-time forward kinematics solution to be achieved and the initial value can be chosen easily.     

Spring-joint method for topology optimization of planar passive compliant mechanisms

There is seldom approach developed for the initial topology design of flexure-based compliant mechanisms. The most commonly-used approaches, which start with an existing rigid-body mechanism, do not consider the performances between different topologies. Moreover, they rely heavily on the rigid-body topology, therefore limit the diversity of compliant mechanisms topology. To obtain the optimal initial topology of such mechanisms directly from problem specifications without referencing to the existing mechanism topologies, a spring-joint method is presented for a restricted class of the serial passive flexure-based compliant mechanisms, which are the building blocks of parallel compliant mechanisms. The topology of the compliant mechanisms is represented by a serial spring-joint mechanism（SSJM） that is a traditional rigid-body mechanism with a torsional spring acting on each joint, and is described by position vectors of the spring-joints. A simplified compliance matrix, determined by the position vectors, is used to characterize the tip of the SSJM kinematically, and is optimized to ensure the desired freedoms of the compliant mechanisms during optimization. The topology optimization problem is formulated as finding out the optimal position of the spring-joints in a blank design domain with an objective function derived from the simplified compliance matrix. In design examples, syntheses of the compliant mechanisms with both single freedom and two decoupled freedoms are presented to illustrate the proposed method. The proposed method provides a new way for the initial design of flexure-based compliant mechanisms.     

基于混合类电磁机制算法的机械臂逆运动学解

机械臂的逆运动学问题可转化为等效的最小化优化问题,并采用数值优化方法求解。提出一种基于类电磁机制(Electromagnetism-like mechanism,EM)和模式搜索(Pattern search,PS)数值求解机械臂逆运动学问题的混合类电磁机制算法(Hybrid electromagnetism-like mechanism,HEM)。该方法利用修改的类电磁机制(Revised electromagnetism-like mechanism,REM)与模式搜索方法各自特性相互融合平衡算法对解空间的全局探索和局部开发能力,基准函数测试结果表明该算法改善了全局搜索性能及寻优解的可靠性。在此基础上以6自由度TX60型号史陶比尔工业机械臂为例,考虑以机械臂末端位姿误差构建适应度函数并采用上混合类电磁机制算法数值求解,仿真结果表明,与其他方法比较,该方法用较少的适应度值计算次数下就能搜索到期望精度的寻优解,并且能搜索到所有可能关节角逆解的潜在能力,验证了该方法的有效性。     

Method for six-legged robot stepping on obstacles by indirect force estimation

Adaptive gaits for legged robots often requires force sensors installed on foot-tips, however impact, temperature or humidity can affect or even damage those sensors. Efforts have been made to realize indirect force estimation on the legged robots using leg structures based on planar mechanisms. Robot Octopus III is a six-legged robot using spatial parallel mechanism(UP-2UPS) legs. This paper proposed a novel method to realize indirect force estimation on walking robot based on a spatial parallel mechanism. The direct kinematics model and the inverse kinematics model are established. The force Jacobian matrix is derived based on the kinematics model. Thus, the indirect force estimation model is established. Then, the relation between the output torques of the three motors installed on one leg to the external force exerted on the foot tip is described. Furthermore, an adaptive tripod static gait is designed. The robot alters its leg trajectory to step on obstacles by using the proposed adaptive gait. Both the indirect force estimation model and the adaptive gait are implemented and optimized in a real time control system. An experiment is carried out to validate the indirect force estimation model. The adaptive gait is tested in another experiment. Experiment results show that the robot can successfully step on a 0.2 m-high obstacle. This paper proposes a novel method to overcome obstacles for the six-legged robot using spatial parallel mechanism legs and to avoid installing the electric force sensors in harsh environment of the robot’s foot tips.     

双稳态平面并联机构

以提高多自由度并联机构的运动性能为目标,探索柔顺双稳态机构在克服并联机构力奇异问题中的应用。提出一种双稳态凸轮柔顺机构,利用双稳态机构在非稳态位形的非零内力,为并联机构提供柔顺过驱动输入,利用柔顺过驱动输入消除并联机构在运动奇异和力奇异位形时的运动或操作力不确定性。以平面五杆2-DOF并联机构为例进行了机构工作空间分析、运动奇异位形分析、以及力奇异位形分析。计算结果证明采用提出的双稳态凸轮柔顺机构能实现该平面2-DOF机构奇异位形的控制。     

基于组合优化算法的6R机器人逆运动学求解

针对逆运动学求解存在的多解、精度低及通用性差等问题,提出了一种适用于各类6R工业机器人求逆解的组合优化算法。根据经典D-H法建立了机器人运动学模型,以最小化位姿误差为目标,结合运动平稳性原则构造了逆解问题的目标函数,以线性加权和法设计了适应度函数。通过混沌映射初始化种群、收敛因子非线性更新、自适应惯性权重位置调整及引入模拟退火策略等4种措施得到了一种改进的鲸鱼优化算法,并用于逆运动学求解。组合算法将鲸鱼算法求解的结果作为初始值,再利用Newton-Raphson数值法迭代出满足精度要求的运动学逆解。仿真试验结果表明：改进后的鲸鱼算法求解性能得到了较大提高,相比于直接利用鲸鱼算法进行逆运动学求解,组合优化算法具有求解速度快、稳定性好、精度高的特点,证明了该算法求逆的可行性与有效性。     

考虑力传递性能的力觉反馈手控器的优化设计

对机构力传递性能进行研究,并提出力传递能力概念。建立一种综合机构工作空间、运动学性能和力传递性能的多目标优化函数,并应用于一种三平动自由度的手控器机构优化设计。对机构优化结果进行工作空间、机构雅可比条件数和力传递性能分析,确定基本结构参数和动力驱动参数,进一步完成样机制作。优化和研制过程为高性能手控器的研制提供了参考。     

仿生移动机器人并联机构运动学正解的鱼群算法求解

基于改进的人工鱼群算法,提出了并联机构运动学正解的求解方法。构建了仿生移动机器人处于支撑状态的并联机构模型,应用螺旋理论计算了该并联机构的空间机构自由度,构建了仿生移动机器人并联机构的运动学正解模型,利用鱼群算法对正解模型的约束方程组进行设计。对鱼群算法所用数学模型进行了构建,对改进后的人工鱼群行为进行了算法描述。仿真结果表明,该人工鱼群算法具有良好的寻优性能,满足仿生移动机器人并联机构正解模型的求解要求。     

四足机器人对角小跑步态动态稳定步行足端非连续约束及动力学建模

将四足机器人对角小跑步态周期分为摆动相和支撑相,采用D-H坐标法进行四足机器人运动学建模分析,提出基于质心运动定理分析腿机构处于支撑相的足端非连续约束力,通过力雅可比矩阵建立足端约束力与关节广义驱动力的映射关系。考虑足端与环境间的非连续约束,建立了具有变拓扑机构、非连续约束等特征的四足机器人非线性动力学模型,并通过虚拟样机仿真验证了动力学理论分析的正确性,为提高四足机器人非结构环境的机动性和动态稳定性研究提供了参考。     

模切机肘杆机构连杆的有限元分析

针对MP1040B型模切机肘杆机构中的连杆在使用中破损故障时有发生,在运动学和动力学分析的基础上,利用有限元方法进行了强度分析,结果表明,当在正常模切力2 450 kN时连杆的强度满足要求,当在极限模切力3 136 kN时连杆的强度不满足要求,分析结果为结构的改进或材料的选择提供了依据.     

多输入多输出柔顺机构拓扑优化及输出耦合的抑制

多自由度柔顺机构在微动精密定位和精密操作等领域有广泛的应用,因而研究多自由度柔顺机构的拓扑优化方法就显得十分必要。给出了一种多输入多输出柔顺机构拓扑优化设计的新方法。首先,推导了描述多输入多输出柔顺机构柔性的互应变能公式和描述机构刚性的应变能公式,研究了抑制耦合输出的策略,进一步给出了描述输出耦合效应的计算公式,在此基础上建立了考虑抑制输入输出耦合效应时柔顺机构的多目标拓扑优化设计模型。其次,基于改进的优化准则法给出了优化模型的有效求解算法。最后,通过算例说明了该方法的正确性和有效性,研究结果表明,拓扑优化后柔顺机构可以按照预定的要求运动,其输出耦合现象得到了有效抑制。     

基于并行策略的多材料柔顺机构多目标拓扑优化*

多材料柔顺机构能够让设计者充分利用各种材料的优良属性,在力,位移,以及能量转移等方面获得更大的设计自由度,因而受到重视。针对受到广泛研究的柔顺机构,结合多目标拓扑优化的方法,提出相应的基于并行策略的求解模型。该方法的核心是将一个复杂的多材料多目标问题离散成为单材料子问题,然后并行求解,再根据整体目标的需要,对所有子问题的解进行调整以得到原始问题的解。针对多目标情形,提出新的材料与输出目标关系,从而在将多材料问题离散成单材料子问题的同时,也将多目标问题离散成单目标子问题。对所有的单材料单目标子问题采用各向同性材料的刚度插值-惩罚法并行独立求解。以上方法有其独特优势：在理论和实践上都比较简单,可以处理任意多种材料,可以避免零碎的拓扑结构因而有利于制造。通过算例说明了此方法的有效性。研究结果表明,该方法在某些输出需要特定材料的设计场合更具优势。     

冗余驱动Tricept并联机构的驱动优化

对冗余驱动3自由度Tricept并联机构的逆运动学和逆动力学进行分析,基于牛顿—欧拉法建立机构的逆动力学方程。针对冗余驱动方式下机构主动关节之间驱动力分配不唯一的特点,研究机构按预期轨迹运动时的驱动优化问题,提出最小化驱动器最大瞬时驱动功率和最大瞬时驱动力的优化方法。结合实例分析机构驱动力2范数优化、最小化最大驱动力优化和最小化最大驱动功率优化的效果,并与非冗余驱动方式进行对比。分析显示,冗余驱动能够较显著地降低驱动器的瞬时负载和瞬时输出功率,并可结合驱动力2范数优化、最小化最大驱动力以及最小化最大驱动功率的优化效果分析,选取适当的驱动方式以实现驱动器瞬时负载与瞬时输出功率的均衡与优化。