Design,modelling and experimentation of a novel compliant translational dwell mechanism

Journal of Mechanical Science and Technology - A partially compliant novel translational double dwell mechanism is presented in this article. The designed mechanism consists of initially straight...     

液压驱动单腿跳跃机器人柔顺着地分析与控制

为缓解液压驱动足式机器人动态步态行走时着地瞬间足端冲击对机器人系统及其运动控制的影响,提出了一种基于关节运动规划的机器人柔顺着地控制方法。以液压驱动单腿跳跃机器人为研究对象,分析机器人足端着地冲量,通过选择合适的机器人着地姿态和减小机器人着地前足端速度实现机器人柔顺着地,为此在空中相进行余弦速度曲线关节运动轨迹规划,以及着地相进行余弦函数关节运动轨迹规划。将该方法分别应用于基于MATLAB/Simulink软件建立的仿真模型和试验样机进行单腿竖直跳跃控制实验,仿真和试验结果显示采用该方法的机器人跳跃控制消除了足端着地瞬间地面作用力在膝关节液压缸无杆腔形成的液压冲击,实验结果表明提出的基于关节运动规划的机器人柔顺着地控制方法合理可行。     

Design,simulation and testing of an isotropic compliant mechanism

In this paper, the concept of isotropic compliance is extended to the field of compliant mechanisms. Starting from the design of a rigid-body mechanism, a planar compliant system is determined by applying the rigid-body replacement method. The static behaviour of the isotropic compliant mechanism is validated by finite element simulations and experimental tests. The extension of the proposed method to the Euclidean Space E(3) is discussed.     

Design of a stiffness-adjustable compliant linear-motion mechanism

A stiffness-adjustable compliant linear-motion mechanism (CLMM) is desired in practical applications. In this paper loads are applied at the secondary stage of a paired double parallelogram (DP-DP) to adjust stiffness, based on the analysis of a combination of parallelograms. Pre-loaded parallelograms and loading springs are utilized to solve the loading problem in practical applications, and the redundant degree of freedom (DOF) is restricted to a certain extent. Meanwhile, the parasitic motion of the primary stage is diminished by arranging the configuration symmetrically. Furthermore, a model, capable of predicting stiffness characteristics, is developed through an energy approach based on the relation between applied forces and internal forces, and a Lagrange multiplier is exploited to deal with the constraints. Finally, the analytical model is verified by finite element analysis (FEA) and experiments, and the errors caused by parasitic motion are corrected for this analytical model.     

Design of a low-cost nano-manipulator which utilizes a monolithic, spatial compliant mechanism

This paper presents the design of a novel, low-cost nano-manipulator which uses a six-axis compliant mechanism which is driven by electromagnetic actuators. The mechanism's monolithic, planar geometry is easily fabricated via planar manufacturing processes, enables compact packaging and incorporates a flexure mechanism for achieving small transmission ratios. The manipulator tolerates ±1 mm actuator misalignment with less than 0.1% full-scale position error. Measurements over a 100 nm × 100 nm × 100 nm work volume show resolution better than our measurement capability of 5 nm and open-loop parasitic errors less than 5 nm. Measurements over a 100 μm × 100 μm × 100 μm work volume show open loop errors less than 0.2% full-scale. The mechanism's equilateral symmetry and planar geometry make it possible to limit thermal drift in position and orientation to less than 23 nm and 4 μrad over a 30 min start up period. The nano-manipulator, built at US$ 2000 cost (excludes electronics), is used as an ultra-precision fiber optic aligner.     

多间隙运动副平面连杆机构动态特性研究

采用非线性弹簧力和非线性阻尼描述含间隙运动副元素的碰撞接触过程，以此为基础建立了多间隙运动副平面连杆机构动力学模型；通过数值仿真研究了多间隙运动副对平面连杆机构动态特性的影响，进而讨论了在高速机构设计中应采取的设计方法；并首次指出了高速运转条件下，运动副元素由于弹性变形而存在的连续变形接触现象和多间隙运动副之间的相互影响特性。     

Design and development of compliant mechanisms for electromagnetic force balance sensor

Compared with the lever-type amplifier, the rhombus-type amplifier has attracted more attention by virtue of large displacement amplification ratio, compact structure, and linear output displacement. In this paper, a novel electromagnetic force balance sensor (EFBS) based on the rhombus-type amplifier is presented to measure the mass with high precision. First, the structure and operating principle of the EFBS are described, and the requirements for the design and manufacture of the amplifier are put forward. Then, the analytical models of the two-stage rhombus-type amplifier are given out, and two guiding mechanisms are analyzed and modeled. Furthermore, the validity of the established model is verified by finite element analysis (FEA). Thanks to the theoretical guidance, an electromagnetic force balance sensor based on the two-stage rhombus-type amplifier and double parallelogram flexure mechanism is designed and tested. The experimental results demonstrate that the developed EFBS can measure the mass of the objects with high precision, and also verifies the correctness of the analytical model. This provides a new concept for the structural design of the EFBS.     

仿袋鼠机器人分布式柔性脚的设计与研究

根据袋鼠的生物结构特征,建立了具有柔性脚的仿袋鼠跳跃机器人的刚柔混合模型。利用柔性机构易于实现连续光滑变形及质量轻,易于控制等特性,将其应用于仿生跳跃机器人领域,来实现跳跃机器人在不同跳跃速度下的脚部轮廓变形。文中根据跳跃机器人在不同跳跃速度下的脚部轮廓曲线,以连续体结构拓扑优化为出发点,建立多目标优化函数,采用移动渐近线法,实现脚部的拓扑结构优化。结合实例仿真结果表明:具有柔性变形能力的柔性脚有助于提高机器人在着地过程中的落地稳定性,增大起跳时间和调整起跳角度,并有效地起到缓冲和储能作用。     

Design and control of a 3DOFs parallel actuated mechanism for biped application

In this paper, a novel approach to carry out the design of a three degrees of freedom (3DOF) actuated mechanisms for humanoid robots joints is presented. Instead of common serial mechanism, a more robust parallel mechanism was developed. This kind of structure gives the terminal body the ability to move within a cone from the nominal position and permits unlimited rotation about the cone pointing axis. Kinematic analysis are presented in this paper. A biped robot ROBIAN with parallel hip and ankle mechanisms was developed and experimental tests were carried out to evaluate the performances of the adopted structure.     

Design of a slider-crank leg mechanism for mobile hopping robotic platforms

Legged locomotion has been widely researched due to its effectiveness in overcoming uneven terrains. Due to previous efforts there has been much progress in achieving dynamic gait stability and as the next step, mimicking the high speed and efficiency observed in animals has become a research interest. The main barrier in developing such a robotic platform is the limitation in the power efficiency of the actuator: the use of pneumatic actuators produce sufficient power but are heavy and big; electronic motors can be compact but are disadvantageous in producing sudden impact from stall which is required for high speed legged locomotion. As a new attempt in this paper we suggest a new leg design for a mobile robot which uses the slider-crank mechanism to convert the continuous motor rotation into piston motion which is used to impact the ground. We believe this new mechanism will have advantage over conventional leg mechanism designs using electronic motors since it uses the continuous motion of the motor instead of sudden rotation movements from stall state which is not ideal to draw out maximum working condition from an electronic motor. In order to control impact timing from the periodic motion of the piston a mechanical passive clutch trigger mechanism was developed. Dynamic analysis was performed to determine the optimal position for the mechanical switch position of the clutch trigger mechanism, and the results were verified through simulation and experiment. Development of a legged locomotion with two degrees of freedom, slider-crank mechanism for impact and additional actuation for swing motion, is proposed for future work.     

Constraint-force-based approach of modelling compliant mechanisms: Principle and application

Numerous works have been conducted on modelling basic compliant elements such as wire beams, and closed-form analytical models of most basic compliant elements have been well developed. However, the modelling of complex compliant mechanisms is still a challenging work. This paper proposes a constraint-force-based (CFB) modelling approach to model compliant mechanisms with a particular emphasis on modelling complex compliant mechanisms. The proposed CFB modelling approach can be regarded as an improved free-body- diagram (FBD) based modelling approach, and can be extended to a development of the screw-theory-based design approach. A compliant mechanism can be decomposed into rigid stages and compliant modules. A compliant module can offer elastic forces due to its deformation. Such elastic forces are regarded as variable constraint forces in the CFB modelling approach. Additionally, the CFB modelling approach defines external forces applied on a compliant mechanism as constant constraint forces. If a compliant mechanism is at static equilibrium, all the rigid stages are also at static equilibrium under the influence of the variable and constant constraint forces. Therefore, the constraint force equilibrium equations for all the rigid stages can be obtained, and the analytical model of the compliant mechanism can be derived based on the constraint force equilibrium equations. The CFB modelling approach can model a compliant mechanism linearly and nonlinearly, can obtain displacements of any points of the rigid stages, and allows external forces to be exerted on any positions of the rigid stages. Compared with the FBD based modelling approach, the CFB modelling approach does not need to identify the possible deformed configuration of a complex compliant mechanism to obtain the geometric compatibility conditions and the force equilibrium equations. Additionally, the mathematical expressions in the CFB approach have an easily understood physical meaning. Using the CFB modelling approach, the variable constraint forces of three compliant modules, a wire beam, a four-beam compliant module and an eight-beam compliant module, have been derived in this paper. Based on these variable constraint forces, the linear and non-linear models of a decoupled XYZ compliant parallel mechanism are derived, and verified by FEA simulations and experimental tests.     

Design and fabrication of miniature compliant hinges for multi-material compliant mechanisms

Multi-material molding (MMM) enables the creation of multi-material mechanisms that combine compliant hinges, serving as revolute joints, and rigid links in a single part. There are three important challenges in creating these structures: (1) bonding between the materials used, (2) the ability of the hinge to transfer the required loads in the mechanism while allowing for the prescribed degree(s) of freedom, and (3) incorporating the process-specific requirements in the design stage. This paper presents the approach for design and fabrication of miniature compliant hinges in multi-material compliant mechanisms. The methodology described in this paper allows for the concurrent design of the part and the manufacturing process. For the first challenge, mechanical interlocking strategies are presented. For the second challenge, the development of a simulation-based optimization model of the hinge is presented, involving functional and manufacturing constrains. For the third challenge, the development of hinge positioning features and gate positioning constraints is presented. The developed MMM process is described, along with the main constraints and performance measures. This includes the process sequence, the mold cavity design, gate selection, and runner system development. A case study is presented to demonstrate the feasibility of creating multi-material mechanisms with miniature hinges serving as joints through MMM process. The approach described in this paper was utilized to design a drive mechanism for a flapping wing micro air vehicle. The methods described in this paper are applicable to any lightweight, load-bearing compliant mechanism manufactured using multi-material injection molding.     

刚性机构与柔性机构性质的探讨

简单介绍了柔性机构及其性质,分析和研究了由拓扑优化得到的力和位移反向器的典型模型,发现在模型构件为刚体条件下,模型的几何增益和机械增益能达到极大即力和位移的输出效率最大。以桁架机构的位移反向器作为基本模型,分析得到有关模型的几何增益的优化目标函数,对目标函数进行了数值优化计算,得到模型的尺寸参数,用结构力学的方法对得到的机构模型进行计算分析。     

微创外科手术机器人多自由度手指机构设计与研究

微创外科手术机器人多自由度手指机构是在满足微创手术要求的前提下,专为外科手术机器人系统研制开发的具有多个自由度的机构。该机构拥有侧摆,俯仰,旋转,夹持4个自由度,采用驱动电机与各个执行关节分离的结构形式,具有夹持灵活性好,质量轻,夹持力大,结构简单等优点,对手指机构的指尖夹持力、关节耦合关系等关键技术进行了研究,为微创外科手术机器人的进一步研制奠定基础。     

Modeling and analysis of an over-constrained flexure-based compliant mechanism

Bridge-type micro-displacement amplifier with flexure hinges is a classic displacement amplification mechanism. Existing theoretic models cannot predict its amplification ratio and input stiffness accurately and make it very difficult to confirm the amplifier’s performance and error compensation by means of these models, which is very significant in ultra-precision positioning. This paper focuses on the development of design equations that can accurately calculate the ideal displacement amplification ratio and input stiffness of the amplifier based on the thought of statically indeterminate structure. Force Method, Maxwell–Mohr Method, principle of superposition and deformation compatibility are used together to establish uncanonical linear homogeneous equations. The analytical results are verified by FEA simulations. The influence of the geometric parameters on the amplifier performance is investigated. It is noted that amplifier performance is more sensitive to the longitudinal distance of flexure hinges. Besides, two same-sized amplifiers with the opposite output directions can be clearly differentiated by these equations.     

空间集中连杆杆件操纵机构的设计和运动学仿真

根据集中连杆杆件操纵机构的基本设计思想，设计了空间集中连杆杆件操纵机构，利用UG建模，用动力学仿真软件ADAMS对其进行了运动学仿真分析。分析结果显示：该空间集中连杆杆件操纵机构的变速，转向和换向操纵机构互不干涉，结构设计合理，可显著提高设计质量，降低开发费用。     

基于并联机构的车辆多维减振座椅的设计

车辆系统的振动是典型的多自由度振动,多自由度减振座椅的减振性能是乘员的乘座舒适性的关键。基于并联机构的多维运动原理,构造出一种新型的具有3自由度的汽车并联减振座椅。对该3自由度的汽车并联减振座椅的主体并联机构建立运动学模型,进行了位置理论分析,最后通过ADAMS软件建立减振座椅振动模型并进行减振性能仿真,验证了该减振座椅系统具有良好的减振效果。     

重型单片液压升降台的设计与研制

针对大载荷、大行程升降台的发展要求,从液压驱动、剪刀撑结构入手,结合当前舞台设备的发展需要,阐述了重型单片液压升降台的设计研制,其设计满足各种演艺场所中对升降台台面越来越大、升降载荷越来越重的要求。     

集中柔度全柔性机构变形分析及仿真

柔性铰链四杆机构在精密机械中的应用日益广泛.采用伪刚体模型法对具有集中柔度的全柔性铰链四杆机构进行了分析,利用MATLAB编写了外载荷与杆件转角关系的Newton迭代法程序.同时用有限元方法建立了全柔性铰链四杆机构模型,并用ANSYS进行了仿真.给出了两种方法的计算实例,对所得结果进行了讨论,分析了误差产生的原因.     

平面柔性机构的结构型式及其自由度分析

平面柔性机构自由度的分析可为选择其驱动器提供依据,平面柔性机构由刚性构件、刚性运动副、柔性构件、柔性铰链四个元素组成,不同元素的不同组合得到不同的柔性机构型式,理论上共计15类,工程应用型计11类,在分析单一柔性构件自由度及其影响因素的基础上,基于“伪刚性机构”的思想,提出了两个及两个以上元素组成柔性机构的自由度计算原则,并根据此计算原则对11类工程应用性的平面柔性机构给出了实例机构的自由度计算.