一种新型柔性直线导向机构及其运动精度分析

Roberts机构是一种近似直线机构,由于机构中不存在交叉的杆件,使得它适合应用在一体化加工的柔性机构中,从而设计出大行程高精度的柔性直线导向机构。单个Roberts机构可由四个参数完全决定几何特征,其中轨迹点P的位置参数对机构运动直线度的影响最大。文中通过对Roberts柔性机构的伪刚体模型进行分析,说明了对应某一行程,轨迹点P的位置存在最优解使其运动直线度最高,并给出一种直线度等值线图方法确定最优解的大概位置,最后借助有限元方法进行进一步的优化。单个Roberts机构只能提供点的直线运动,可将两个Roberts机构进行并联得到一个柔性导向机构。本文对这种柔性导向机构进行了设计加工、仿真以及试验,结果表明这类柔性导向机构可以在毫米级行程时,垂直运动方向上的偏移小于1um。     

基于伪刚体模型法的全柔性机构位置分析

柔性机构是一种依靠构件元素的弹性变形传输所希望运动的机构。具有集中柔度的全柔性机构是其中的一种类型，其特征是机构中传统形式的铰链全部被柔性铰链所代替。对它的研究，近年来也已成为一个热点。为探索这类全柔性机构的运动学问题，首先建立起柔性铰链变形刚度模型。在此基础上，提出了一种扩展的伪刚体模型法，很好地解决了机构的位置正、反解问题。     

基于变胞铰链的并联机构结构设计与构型分析

为了拓展变胞机构的种类,提出了一种变胞运动单元,该变胞单元采用三个旋转关节,并且三个旋转关节可以通过位置调节形成等效球铰、虎克铰以及转动副。与传统的锁定运动副来实现变胞功能的变胞单元相比,此变胞单元三种构型的切换只需对轴线位置调整,无需额外增加关节锁死电机。通过研究由线矢量构成的螺旋系统的相关性,揭示了变胞运动单元构态变化的基本原理。提出了可用于构造新型变胞并联机构的支链构型设计方法,并基于螺旋的互易性分析了各支链构型所必须满足的几何约束条件。提出了两种变胞并联机构,通过不同的支链装配形式可将其从6自由度构型转换为3自由度构型,并对支链安装形式进行改进,构造出了具有3自由度平移模式和3自由度转动模式的并联机构。对变胞支链作为中心支链组装而成的并联机构的构型及对应的运动类型进行了分析,获得了六种不同构型的并联机构。     

混合型三维减振平台主体机构的运动及受力分析

采用三平移并联机构3-RRRP(4R)作为三维减振平台主体机构.论述了采用柔性关节与普通关节混合型的主体机构的结构,对原机构主动副采用常用转动副加扭簧装置外,其余转动副采用簧片结构,消除了运动副间隙,提高了减振灵敏度.对该机构进行了位置正解、反解分析和力学分析,并讨论了运动学工作空间.运用当量摩擦圆概念来近似替代柔性关节,分析带柔性关节机构的力学工作空间.对该机构的整体力平衡进行了讨论,提出了解决整机力平衡的方法.     

A novel analytical model for flexure-based proportion compliant mechanisms

This paper proposes a novel analytical model for flexure-based proportion compliant mechanisms. The displacement and stiffness calculations of such flexure-based compliant mechanisms are formulated based on the principle of virtual work and pseudo rigid body model (PRBM). According to the theory and method, a set of closed-form equations are deduced in this paper, which incorporate the stiffness characteristics of each flexure hinge, together with the other geometric and material properties of the compliant mechanism. The rotation center point for a corner-filleted flexure hinge is investigated based on the finite element analysis (FEA) and PRBM. An empirical equation for the rotational angle is fitted in this paper in order to calculate accurately the position of the end-point of the flexure hinge. The displacement proportion equation for such mechanisms is derived according to the new approach. Combining the new proposed design equation and the existed stiffness equation, a new proportion compliant mechanism with corner-filleted flexure hinges is designed by means of the least squares optimization. The designed models are verified by finite element analysis.     

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.     

Integrating mechanism synthesis and topological optimization technique for stiffness-oriented design of a three degrees-of-freedom flexure-based parallel mechanism

This paper introduces a new design approach to synthesize multiple degrees-of-freedom (DOF) flexure-based parallel mechanism (FPM). Termed as an integrated design approach, it is a systematic design methodology, which integrates both classical mechanism synthesis and modern topology optimization technique, to deliver an optimized multi-DOF FPM. This design approach is separated into two levels. At sub-chain level, a novel topology optimization technique, which uses the classical linkage mechanisms as DNA seeds, is used to synthesize the compliant joints or limbs. At configuration level, the optimal compliant joints are used to form the parallel limbs of the multi-DOF FPM and another stage of optimization was conducted to determine the optimal space distribution between these compliant joints so as to generate a multi-DOF FPM with optimized stiffness characteristic. In this paper, the design of a 3-DOF planar motion FPM was used to demonstrate the effectiveness and accuracy of this proposed design approach.     

Pseudo-rigid-body model for corrugated cantilever beam used in compliant mechanisms

Common compliant joints generally have limited range of motion, reduced fatigue life and high stress concentration. To overcome these shortcomings, periodically corrugated cantilever beam is applied to design compliant joints. Basic corrugated beam unit is modeled by using pseudo-rigid-body method. The trajectory and deformation behavior of periodically corrugated cantilever beam are estimated by the transformation of coordinate and superposition of the deformation of corrugated beam units. Finite element analysis（FEA） is carried out on corrugated cantilever beam to estimate the accuracy of the pseudo-rigid-body model. Results show that the kinetostatic behaviors obtained by this method, which has a relative error less than 6%, has good applicability and corrugated cantilever beam has the characteristics of a large range of motion and high mechanical strength. The corrugated cantilever beam is then applied to design a flexible rotational joint to obtain a larger angle output. The paper proposes a pseudo-rigid-body model for corrugated cantilever beam and designed a flexible rotational joint with large angle output.     

Compliant Mechanism Synthesis by Using Elastic Similitude

Compliant mechanisms have several advantages, especially smaller number of elements and therefore less movable joints. The flexural members furthermore allow an integration of special functions like ba...     

Stiffness Analysis of Corrugated Flexure Beam Used in Compliant Mechanisms

Conventional flexible joints generally have limited range of motion and high stress concentration. To overcome these shortcomings, corrugated flexure beam(CF beam) is designed because of its large flex...     

空间机器人捕获航天器操作的避撞柔顺无源神经网络H∞控制

研究了空间机器人在轨捕获非合作航天器过程避免关节受冲击破坏的避撞柔顺控制问题。为此在关节电机与机械臂之间配置了一种柔顺机构--旋转型串联弹性执行器(RSEA),可通过其内置弹簧的变形来吸收捕获过程目标航天器对空间机器人关节产生的冲击能量;结合所设计的开、关机控制策略可保证关节冲击力矩受限在安全范围内。首先利用拉格朗日方法及牛顿-欧拉法分别获得了捕获前空间机器人及目标航天器的分体系统动力学模型;之后,结合冲量定理、系统运动几何关系及力的传递规律,建立了捕获后两者形成混合体系统的动力学模型,并计算了碰撞过程的冲击力矩;最后,基于无源性理论提出了一种神经网络鲁棒H∞避撞柔顺控制策略以实现失稳混合体的镇定控制。数值仿真结果表明,配置柔顺空间机器人在捕获碰撞阶段最大可减小61.9%的关节冲击力矩,最小也可减小47.8%;而在镇定运动阶段,各关节冲击力矩均受限在安全范围内,实现了对关节有效地保护。     

精确直线可展机构及其动力学分析

将Hart直线机构和剪叉机构相结合,提出一种仅含转动副的直线可展单元,并设计得到一种精确直线可展机构。根据机构结构学分析理论,阐述可展机构的模块化组成原理,将机构的组成分解为底部模块、中部模块和顶部模块,3种模块均由直线可展单元构成;对单个直线可展单元进行运动学建模,结合机构的模块化组成原理,推导得到任意模块间的运动学递推关系,求解得到多层模块条件下机构的整体运动学模型,运用Lagrange方程构建机构的整体动力学模型;以3层可展机构为例,对其进行动力学数值计算和虚拟仿真,验证所建运动学和动力学模型的正确性和有效性。通过给定末端执行器的输出运动规律,求解得到机构所需的驱动力矩,结果表明：末端执行器为正弦加速度曲线时,机构在整个工作周期内无冲击,运动稳定性好。     

压电位移放大机构的力学解析模型及有限元分析

研究了压电位移放大机构的运动学和动力学建模问题。基于能量守恒原理和弹性梁弯曲理论推导了桥式位移放大机构的位移放大比等静力学解析模型;在此基础上,通过拉格朗日方程建立了桥式位移放大机构的固有频率解析模型。通过有限元计算验证和分析了提出的解析模型的可行性和优越性,并与国内外典型的位移放大比数学模型进行了比较。结果表明:由于本文提出的模型考虑了位移放大机构的拉伸和弯曲变形,并且摒弃了国内外普遍采用近似几何关系进行数学推导的思路,因此所建立的位移放大比解析模型精度更高;固有频率解析计算结果与有限元模态分析结果的相对误差约为5%。得到的结果显示:本文给出的建模方法以及位移放大比、固有频率等解析模型可为柔性机构的优化设计和研制提供依据和参考。     

基于最大应力约束的柔顺机构拓扑优化设计

采用拓扑优化方法获得柔顺机构构型容易出现类铰链结构,导致应力集中、疲劳可靠性差。为了抑制类铰链结构,提出了一种基于最大应力约束的柔顺机构拓扑优化设计方法。采用改进的固体各向同性材料惩罚模型（Solid isotropic material with penalization,SIMP）,以柔顺机构的互应变能最大化作为目标函数,采用P范数方法对所有单元的局部应力凝聚化成一个全局化应力约束,利用自适应约束缩放法使得P范数应力更加接近最大应力,以机构的最大应力和体积作为约束,建立柔顺机构最大应力约束拓扑优化模型,采用全局收敛移动渐近线算法求解柔顺机构最大应力约束拓扑优化问题。结果表明,采用P范数方法进行柔顺机构最大应力约束拓扑优化设计,能够有效抑制类铰链结构。随着应力约束极限值减少,获得机构构型由集中式柔顺机构逐渐转变为分布式柔顺机构,应力分布更加均匀,但机构的互应变能逐渐减小。     

Manufacturing of multi-material compliant mechanisms using multi-material molding

Multi-material compliant mechanisms enable many new design possibilities. Significant progress has been made in the area of design and analysis of multi-material compliant mechanisms. What is now needed is a method to mass-produce such mechanisms economically. A feasible and practical way of producing such mechanisms is through multi-material molding. Devices based on compliant mechanisms usually consist of compliant joints. Compliant joints in turn are created by carefully engineering interfaces between a compliant and a rigid material. This paper presents an overview of multi-material molding technology and describes feasible mold designs for creating different types of compliant joints found in multi-material compliant mechanisms. It also describes guidelines essential to successfully utilizing the multi-material molding process for creating compliant mechanisms. Finally, practical applications for the use of multi-material molding to create compliant mechanisms are demonstrated.     

纳米级精度柔性机器人的设计方法及实现研究

从材料、几何结构、柔性铰链、驱动器、运动与负载及加工等几个方面总结了面向精密作业的柔性机器人设计准则。对柔性机器人的设计方法进行了探讨。以精密作业中的具体应用为例，依据这些设计方法与准则，从机械本体和驱动器控制2个方面详细描述了可实现纳米级精度的3自由度柔性机器人样机设计的具体实现过程，设计结果满足任务要求。     

铰链点可互换的近似直线机构综合方法及解域研究

基于拐点圆极点理论,给出了一种可以综合出无穷多铰链四杆近似直线机构的方法。用解析法证明了该方法综合出近似直线机构的一个连架杆的固定铰链点和对应动铰链点可以互换,铰链点互换前后得到的两个机构具有相同的鲍尔点和直线方向,另外一个连架杆不变。推导了综合曲柄摇杆直线机构的公式,并绘制了曲柄摇杆机构解域图。计算示例表明该方法简单有效,能迅速综合出曲柄摇杆直线机构,且综合出的机构动铰链点和固定铰链点可互换。所得到的近似直线机构为实际工程应用提供了更多选择。     

Application of the TRIZ creativity enhancement approach to design of passively compliant robotic joint

The essence of the conceptual design is getting the innovative projects or ideas to promise the products with best performance. It has been proved that the theory of inventive problem solution (TRIZ) is a systematic methodology for innovation. The design of a passively compliant robotic joint as an engineering example is illuminated in this paper to show the significance and approaches of applying TRIZ into getting the creative conceptual design ideas. In the robotic joints with passively compliance, the joints are composed of mechanical components such as springs and dampers as internal elements, which absorb the excessive collision force. Passive compliant joints with springs and dampers ensure a smooth contact with the surroundings, especially if robots are in contact with humans, but the passive compliant joints cannot determine precisely the position of the members of the joint or direction of the collision force. The main aim of this work is to show a systematic methodology for innovation as an effective procedure to enhance the capability of developing innovative passive compliant robotic joint and to overcome the main design problems. The TRIZ method will be utilized in order to eliminate the technical contradictions which appear in the passively compliant robotic joint.     

Constraint Force Analysis of Metamorphic Joints Basedon the Augmented Assur Groups

In order to obtain a simple way for the force analysis of metamorphic mechanisms, the systematic method to unify the force analysis approach of metamorphic mechanisms as that of conventional planar mec...     

Partially compliant spatial slider-crank (RSSP) mechanism

In this study, a novel compliant mechanism, “partially compliant spatial slider-crank (RSSP)” is proposed. All possible configurations of compliant RSSP mechanisms are classified and discussed. A method is derived to determine deflection of the multiple-axis flexural hinge for all positions of the crank. A design procedure for partially compliant RSSP mechanisms is introduced. In order to prove the feasibility of the proposed mathematical model, a real model is built and it is shown that results are consistent.