Design of neural networks model for transmission angle of a modified mechanism

This paper discusses Neural Networks as predictor for analyzing of transmission angle of slider-crank mechanism. There are different types of neural network algorithms obtained by using chain rules. The neural network is a feedforward neural network. On the other hand, the slider-crank mechanism is a modified mechanism by using an additional link between connecting rod and crank pin. Through extensive simulations, these neural network models are shown to be effective for prediction and analyzing of a modified slider-crank mechanism’s transmission angle.     

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.     

尾鳍推进式水上自行车设计

介绍一种基于鲹科鱼类推进机理的水上自行车,主要结构由减速齿轮传动机构、曲柄滑块摇杆机构、方向指示针、支撑体和尾鳍组成。通过对相关机构运动学分析并运用ADAMS对其进行运动仿真,得出该设计机构能够满足设计要求。以上机构能使鱼尾摆动和暂停实现前进和转弯,机动性较好且省力效果显著。     

Synthesis of optimum slider-crank mechanismsCИ

For the spatial slider-crank mechanism formulas are obtained to allow the user determine the link sizes and slider offset for a predetermined stroke with an acceptable pressure angle at the extremes of slider travel as well as by a given angle between the crosshead guide of the slider and a plane in which the crank revolves. Formulas for determining the sizes of links of the plane slider-crank mechanism as a special case of the spatial mechanism are also presented. The particular cases of mechanisms havingequal angles of pressure as well as at extreme values of an angle between crosshead guide and the revolution plane of the crank are discussed. It is shown, that the plane mechanism case provides maximum slider travel when other things are equal.     

曲柄滑块机构的运动误差补偿

在实际的机械系统中,由于构件的加工、装配误差和磨损,机构系统中一定会存在误差。误差的存在会影响机械系统的稳定可靠性和运动精度,使得实际机构和理想机构之间存在运动误差。现代机械工业正向着高精度、高速度、高效率的方向发展,如何减小机械系统中的误差是一个关键问题。本文应用曲柄滑块机构为例,提出一种增加一个自由度的方法,把曲柄滑块机构改装成五杆机构,通过控制新增的自由度来减小系统误差的方法。运用开环运动补偿控制和PID闭环控制方法对五杆机构进行控制,从而提高系统的可靠性和运动精度。实验结果表明:所提出的方法能够有效的减小机构系统中的误差,提高了曲柄滑块机构的运动精度。     

偏置式曲柄滑块机构仿真与运动分析

综合利用函数法和矢量法,在S imu link环境下对偏置式曲柄滑块机构进行了仿真和运动分析。首先,通过函数法对偏置式曲柄滑块机构的运动特性进行分析,根据矢量法建立机构的运动学矩阵方程。然后,在S imu link软件环境下建立该方程的仿真模型,进行运动分析,得到了偏置式曲柄滑块机构的运动曲线。将函数法与矢量法相结合有助于更深入地了解机构的运动特性。     

一种考虑轴承缺陷影响的机构动力学分析方法

为有效地揭示轴承滚道缺陷特征对高速机构动态响应特性的影响规律,在多体动力学理论框架下提出一种考虑轴承缺陷影响的机构动力学分析方法。该理论采用力约束方法构建机构中滚动轴承转动副模型,通过分析轴承中各滚动体与滚道缺陷几何特征之间的接触关系,计算滚动体接触载荷并获取轴承转动副等效约束反力,探讨轴承缺陷激励对高速机构动态性能的影响规律。在此基础上,以含深沟球轴承的曲柄滑块机构为例,分析轴承滚道表面局部式缺陷和分布式波纹度缺陷对机构动力学特性的影响。研究表明,轴承滚道缺陷将引发轴承各滚动体接触动载荷突变。这种突变载荷经传播后,直接影响着机构中各构件的运动状态,对高速机构运动平稳性将产生严重影响。此外,该理论方法具有一般性,具有不同滚道几何缺陷特征的滚动轴承均可嵌入到本方法中,分析轴承转动副缺陷对各类机构动力学特性的影响。     

基于连杆理论的装载端口开门机构设计与运动学仿真

根据结构设计的型综合理论,提出一种将平行四连杆机构和曲柄滑块机构串联起来作为装载端口开盒装置、映射定位系统的驱动机构。利用MATLAB中SimMechanism模块建立了传统机构和新型机构的运动学仿真模型,通过分析比较两者的运动特性,验证了新型机构设计的合理性。     

模拟柔顺机构中柔顺杆件末端特征的2R伪刚体模型

柔顺机构是一种新型机构,其中包含的柔顺杆件会因为产生大变形而导致分析起来十分复杂。伪刚体模型能够简化柔顺杆件的大变形分析。基于伪刚体模型的原理,针对柔顺机构中的柔顺杆件,提出以末端转角参数化近似方法为基础的2R伪刚体模型。该模型用两个不同劲度系数的扭转弹簧连接3个不同长度的刚性杆件,并用特征半径系数表征刚性杆件的长度,用刚度系数表征扭簧的扭转能力,通过二维搜索得到模型的最优特征半径系数,应用线性回归方法得到模型的刚度系数。该模型能准确模拟柔顺机构中柔顺杆件的末端变形轨迹和变形角度。推导柔顺杆件和伪刚体模型变形时的应变能公式,通过数值对比,从能量角度评价伪刚体模型储存应变能的能力。     

全柔性机构与MEMS

柔性机构是一种新型机构。首先描述了柔性机构和全柔性机构的概念及特点,论述了它们与MEMS之间的关系。然后详细介绍了全柔性机构在MEMS领域内包括微装配、微操作等应用背景下的状况及前景。最后就对全柔性机构研究中的几个关键技术问题如机构的分析、设计及加工,柔性铰链的选择与设计,驱动器的选择及设计等进行了探讨。     

考虑铰链运动副间隙的机构运动可靠性分析模型

针对高速运动机构的特点,补充考虑铰链式运动副间隙的机构运动可靠性分析模型,并以曲柄滑块机构为例,应用非连续接触模型和连续接触模型,详尽分析运动副径向间隙和销轴位置的不确定性因素对机构运动可靠性的影响.     

The force transmissivity index of planar linkage mechanisms

In this paper, a new force transmissivity index (FTI) of planar linkage mechanisms is proposed. The index is used to quantitatively measure the force transmission quality from the input link to an output link. Traditionally, the transmission angle is used to measure the ability to transmit motion for planar four-bar linkages. However, the transmission angle is usually limited to be used at four-bar linkages due to the structural simplicity. For complex multi-loop mechanisms, it is often difficult to define the force transmissivity. Here we have established a procedure of force transmissivity analysis for planar linkage mechanisms. The method is based on the static force analysis and the concept of power flow path. It is found that the force transmissivity of a mechanism depends not only on the configurations of the mechanism, but also on the selection of the output link and the forms of the loading. We have compared the results based on the FTI with the results from the Jacobian matrix method and the joint force index (JFI) method for four-bar mechanisms. It shows that the proposed FTI can describe the force transmission performance more accurately than other methods do. It is concluded that the index can be used as a better measure of force transmissivity analysis for planar linkage mechanisms.     

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。     

按急回要求设计曲柄滑块机构的一种新解析法

提出了一种设计曲柄滑块机构的新方法。该方法通过求解一个简单的线性方程组，或直接利用文中给出的解析计算公式，可非常方便地设计出满足急回要求的各构件的运动尺寸。     

柔性机构的结构拓扑特征及其自由度分析

柔性机构是利用组成元素间的相对柔性来获得运动或力的一类机构。通过分析柔性机构的结构特点 ,本文提出了一个新的拓扑图来表示柔性运动链的结构拓扑特征 ,并给出了相应的矩阵表示 ,借助该矩阵中的信息 ,可以方便地对柔性机构进行自由度分析。并且指出柔性机构是一种变自由度机构 ,其自由度的数目与机构所受外力 (矩 )的大小和方位有关。     

形状记忆合金驱动的曲柄滑块机构多目标优化设计

提出了一种应用于水下机器人方向舵、滑块为原动件的曲柄滑块传动机构,形状记忆合金差动驱动是该机构的突出特点.分析了形状记忆合金差动驱动的曲柄滑块机构运动机理,基于形状记忆合金驱动器的变形能力和力学性能,采用多目标优化设计理论和算法,对形状记忆合金差动驱动的滑块行程和作用在滑块上的初始驱动力进行了综合优化,得到了曲柄滑块机构的结构优化参数,同时为形状记忆合金差动驱动器的性能参数设计提供了理论依据和设计准则.虚拟样机仿真试验验证了机构良好的驱动和传动性能.     

On Generating Expected Kinetostatic Nonlinear Stiffness Characteristics by the Kinematic Limb-Singularity of a Crank-Slider Linkage with Springs

Being di erent from avoidance of singularity of closed-loop linkages, this paper employs the kinematic singularity to construct compliant mechanisms with expected nonlinear sti ness characteristics to enrich the methods of compliant mechanisms synthesis. The theory for generating kinetostatic nonlinear sti ness characteristic by the kinematic limb-singularity of a crank-slider linkage is developed. Based on the principle of virtual work, the kinetostatic model of the crank-linkage with springs is established. The influences of spring sti ness on the toque-position angle relation are analyzed. It indicates that corresponding spring sti ness may generate one of four types of nonlinear sti ness characteristics including the bi-stable, local negative-sti ness, zero-sti ness or positive-sti ness when the mechanism works around the kinematic limb-singularity position. Thus the compliant mechanism with an expected sti ness characteristic can be constructed by employing the pseudo rigid-body model of the mechanism whose joints or links are replaced by corresponding flexures. Finally, a tri-symmetrical constant-torque compliant mechanism is fabricated,where the curve of torque-position angle is obtained by an experimental testing. The measurement indicates that the compliant mechanism can generate a nearly constant-torque zone.     

空间相机均力输出式调焦机构

为了补偿空间相机因所处复杂运载环境和空间运行环境导致的焦平面偏移,研制了一套利用均力输出组件驱动,正反双曲柄滑块机构传动,直动组件导向的新型高精度调焦机构。介绍了其结构组成和运动原理,并对其误差来源及影响因素进行了深入分析。该调焦机构采用两点支撑方式,两支撑点均力输出且无同步性误差,机构内应力小,运行平稳,调焦精度高;运动副采用预压消间隙措施,有效消除配合间隙,无空回,重复精度高。在模拟空间环境条件下,对其各项参数进行了测试。试验结果表明,该调焦机构可在±1.77mm间调焦,直线定位精度大于±8μm,重复性优于±2μm;同步性误差小于±4μm,重复性优于±3μm;调焦行程范围内调焦反射镜转角精度优于±5″,重复性优于±1.5″。得到的结果能够满足空间相机在复杂空间环境下的成像需求。     

曲柄滑块急回机构的设计研究

给定行程速比系数K时,如何设计出最大压力角为最小的曲柄滑块机构,或者给定许用压力角时,如何设计出行程速比系数K为最大的曲柄滑块机构?这是设计者希望解决的优化设计问题。文中采用黄金分割法,编制出简单的QBASIC程序,可以迅速解决上述问题。     

快速反射镜中柔顺传动机构应用与研究现状

从柔顺传动机构自身运动特点出发,介绍了应用在快速反射镜中较典型的柔性支承传动结构,对国外早期几款比较有特点和现阶段较为先进的快速反射镜从驱动方式、结构布局、支承传动、工作原理等方面进行了介绍和分析。针对目前柔顺传动机构的研究情况,归纳了应用在快速反射镜中柔顺传动单元的设计方法、空间机构构型、刚度分析以及整体动力学分析方法等。最后对快速反射镜中柔顺传动机构的研究和发展方向作出了总结。