平面3自由度并联机器人的动力学设计

从动力学角度分析一种平面3自由度并联机器人的设计问题.首先,基于Lagrange方程导出此平面3自由度并联机器人的动力学方程.然后,基于系统动力学方程提出机构参数设计的三点措施.例如,可以通过在系统中添加适当的平衡质量消除动力学方程中重力项和大部分耦合项的影响.采取这些措施对提高并联机器人系统的动态特性、易控性,以及增强系统运行的稳定性和精度等都具有重要作用.最后,通过算例验证这些措施在降低驱动力矩和减少系统能耗方面的可行性和效果.这些内容可为进一步研究此并联机器人的动力学特性、优化设计和控制等提供指导.采用的方法对其他多自由度多连杆机构的动力学分析和动力学设计具有重要的借鉴意义.     

一种自由度缩减和收敛加速的高效等几何拓扑优化方法

为提高等几何拓扑优化效率,提出了一种高效等几何拓扑优化方法,从自由度缩减和收敛加速两个方面对等几何拓扑优化进行加速。自由度缩减算法包括基于位移变化的自由度缩减和基于空单元的自由度缩减,收敛加速算法包括设计变量缩减和灰度抑制算法。二维和三维算例结果表明,所提出的高效等几何拓扑优化方法在保证优化精度的同时,相对于传统等几何拓扑优化方法的加速比为1.56～6.02,显著提高了等几何拓扑优化的效率,为产品结构的高效高质量设计提供了有力支撑。     

行星齿轮传动机构动力学分析

针对混合动力汽车行星齿轮减速机构,采用集中质量法构建其多自由度系统的动力学模型.在时变啮合刚度和齿频误差激励下,将多自由度振动系统的动力学方程转化为系统的状态方程和传递函数方程.采用变步长四阶Runge-Kutta法及机械阻抗法,借助MATLAB仿真工具箱,对振动系统进行了时域和频域数值仿真,获得了系统的动态响应和齿间动载特性.仿真结果表明,太阳轮浮动改善了齿间动载,使其在各行星轮上的分布趋于均匀;刚度波动幅值越大,系统振动越严重.     

并联机构的结构降耦原理及其设计方法*

机构学的难题之一是寻找机构拓扑结构学与运动学、动力学之间的映射规律。前期研究表明,降低机构的结构耦合度可直接降低机构运动学、动力学求解的难度,这揭示了机构拓扑结构学与运动学、动力学之间的关系之一,因此,如何降低机构的结构耦合度已成为机构拓扑结构优化的重要内容,但目前国内外研究很少。研究并联机构的结构降耦原理、设计方法及其应用。定义并联机构结构降耦的概念,澄清并揭示机构结构降耦与机构运动解耦之间的内在区别与联系。从并联机构支链本身的拓扑结构以及支链在动/静平台之间布置的拓扑结构两方面,提出保持并联机构自由度和方位特征不变而降低机构耦合度的两个结构降耦原理,据此,进一步提出了基于设计混合支链的、基于运动副复合的、基于方位特征支链主动化的三种结构降耦设计方法,并分别给出设计例子,得到相应的自由度和方位特征保持不变但耦合度降低的新机构,为其应用研究提供了优选机型。提出的机构结构降耦原理与设计方法,适用于所有的复杂平面和空间平面。     

四足机器人的腿部拓扑结构研究及其动力学仿真

对一种四足机器人的腿部机构设计方法进行探究。简析哺乳动物腿部关节分布,确立了四足机器人拓扑结构与自由度数目,用拉格朗日方程对其动力学简略推导,并建立虚拟样机。借助ADAMS动力学仿真软件,验证四足机器人虚拟样机在起立过程和对角步态的动力学规律。     

机电集成超环面传动二自由度控制器的设计

针对提出的新型机电集成超环面传动,建立了机电耦合动力学模型,推导了速度传递函数。设计了两组独立参数的二自由度(TDF)控制器,得到理想的响应特性,消除了系统稳态误差。分析了该传动特有的输出扰动规律,为消除扰动对控制系统的不利影响,求得了补偿电压。研究结果证明了控制器和补偿电压的有效性,对该种新型传动的实际应用具有指导意义。     

一种圆柱面平移和一转动并联机构的设计与分析

基于方位特征集（POC集）的并联机构拓扑设计理论与方法,设计了一种新型3自由度（DOF）的具有圆柱面平移和一转动（2T1R）的并联机构,并且对该机构进行了拓扑特性分析。主要包括：方位特征集、自由度和耦合度计算;对机构进行运动学分析,求解机构位置的正逆解,并对该机构进行了数值验证;基于机构位置的正逆解方程,分析了机构的工作空间及转动能力。为该机构后续的尺度优化、误差分析及动力学分析奠定了基础。     

多自由度振动台的发展与控制技术

该文介绍了国内外多自由度振动台的主要应用领域、需求状况和发展趋势;对超大规模多自由度振动台的并联机构进行运动学、动力学分析;分析了振动台台体的自振频率与加速度响应一致性之间的关系,介绍了振动台台体设计的基本原则,最后从自由度合成与分解、运动学分析、同步控制三个方面分析了超大规模多自由度振动台的控制方法。     

并联机构拓扑结构特征分析软件的框架设计及实现

基于方位特征(POC)方程的并联机构拓扑结构设计方法提出了机构POC、自由度和耦合度等拓扑结构特征指标,用于揭示并联机构结构学、运动学和动力学的一些基本特性,但其人工计算、分析过程冗长、复杂、费时,所以研究了拓扑结构特征指标计算机自动分析软件的总体框架及其实现流程。首先,提出了能自动识别支链运动副轴线关系的并联机构字符串描述模型,以及支链POC集的矩阵描述模型;基于此描述模型,研究了POC集"交"和"并"运算规则的算法,给出了机构POC、自由度和独立位移方程数的自动分析流程;接着,给出了并联机构拓扑结构最佳分解路线的算法,制定了机构耦合度自动化分析的实现流程。最后,利用VC++编程开发了程序,并对并联机构进行了实例计算,其结果与人工计算分析一致。该算法和程序有助于更多的机构学研究和设计人员,较易计算、分析并联机构的拓扑结构特征。     

基于方位特征方法的范例并联机构的拓扑特征分析及其启示与应用

机构拓扑结构特征是并联机构固有的拓扑不变量,反映了机构的结构学、运动学及动力学基本特性;剖析在设计与应用上较为成功的范例并联机构的拓扑结构特征,对并联机构的研究具有借鉴和启示作用。应用基于方位特征(Position and orientation characteristic,POC)的并联机构拓扑结构设计理论与方法,对2~6-DOF的34种范例并联机构,即已推广运用的8种著名并联机构Delta、Diamond、Tricept、Tri Variant、Exechon、Z3、H4、Steward以及26种具有潜在应用价值的并联机构,进行拓扑结构分析,分别给出其拓扑结构特征,并总结出共性规律。基于此,研发出5自由度混联检测平台和喷涂机器人。研究结果表明,应用基于POC的并联机构拓扑结构设计理论与方法,可较好地揭示出包括范例并联机构在内的所有机构的拓扑结构特征;而从中得到的机构设计与应用的一些共性规律,可对并联机构的理论研究、工业设计和应用提供重要参考和启示。     

A study on tracking error based on mechatronics model of a 5-DOF hybrid spray-painting robot

Industrial robots suffer from difficulties in predicting and guaranteeing tracking performance due to the complex dynamic behavior and inaccurate mechatronics model. This study investigates the tracking error and motion accuracy improvement based on a mechatronics model of a 5-degree of freedom hybrid spray-painting robot. The dynamic model of the robot is derived by using Lagrange equation, and an identification method is presented to identify the torque coefficient and joint friction synchronously. An accurate mechatronics model is established after the theoretical dynamic modeling and friction identification. The tracking error generation mechanism of the robot control system is studied, and its analytical equation is derived on the basis of a transfer function. A multichannel feedforward controller is synthesized to reduce the tracking error from different sources. The effectiveness of the proposed method in improving tracking accuracy is verified by physical experiments.

     

Nonlinear dynamic characteristics of geared rotor bearing systems with dynamic backlash and friction

Effects of the friction and dynamic backlash on the multi-degree of freedom nonlinear dynamic gear transmission system, which incorporate time varying stiffness, are investigated. Firstly, the relationship between gear central distance error and backlash is deduced and the dynamic backlash is defined, subsequently a multi-degree of freedom nonlinear dynamic gear transmission system is developed with dynamic backlash, friction and time varying stiffness. The nonlinear dynamic system is solved by the Runge-Kutta method. The results show that the friction force may enlarge the displacement magnitude and affect the high frequency parts significantly in frequency domain at low speed. But the RMS of the steady response is reduced on the effect of friction. The difference between the constant backlash and the dynamic backlash models is also discussed. The system may enter into previous chaotic motion due to the effect of dynamic backlash. Finally, no impact motion, single-side impact motion and double-side impact motion are also predicted in the new dynamic backlash model.     

多种群遗传优化的客车防侧翻鲁棒控制方法

为改善客车主动防侧翻能力,提出多种群遗传优化的防侧翻鲁棒控制方法。考虑车轮侧倾外倾、侧倾转向、悬架变形外倾和变形转向对轮胎侧偏特性影响,以及客车垂向与侧倾运动的耦合特性,建立6自由度客车侧翻动力学模型;针对客车的实际干扰及参数不确定性,以最大横向载荷转移率为控制目标,融合差动制动原理设计客车主动防侧翻的鲁棒控制方法;应用多种群遗传理论对控制器的权函数进行动态优化,增强控制系统的抗干扰能力;选取J-Turn及Worst-Case典型侧翻工况进行数值仿真,分析防侧翻控制方法对不同行驶工况的适用性、前轮转向干扰及路面干扰下的抗干扰稳定性以及簧载质量和车速变化时参数摄动鲁棒性。结果表明该方法能将客车侧翻危险速度提高75%以上,有效改善客车主动防侧翻能力;且对不同行驶工况、不同类型干扰及参数变化均有强鲁棒性。     

On the improvement design of dynamic characteristics for the roller follower of a variable-speed plate cam mechanism

Without modifying the cam contour, a cam mechanism with a variable input speed trajectory offers an alternative solution to flexibly achieve kinematic and dynamic characteristics, and then decrease the follower’s residual vibration. Firstly, the speed trajectory of cam is derived by employing Bezier curve, and motion continuity conditions are investigated. Then the motion characteristics between the plate cam and its roller follower are derived. To analyze the residual vibration, a single degree of freedom dynamic model of the elastic cam-follower system is introduced. Based on the motion equation derived from the dynamic model, the residual vibration of the follower is yielded. The design procedure to improve the kinematic and dynamic motion characteristics is presented and two design examples with discussions are provided. Finally, the simulations of the kinematic and dynamic models by ADAMS are carried out and verified that the design models as well as the performances of the mechanism are feasible.     

The sensitivity analysis of yaw rate for a front wheel steering vehicle: In the frequency domain

In this paper, the sensitivity analysis of yaw rate for a front wheel steering vehicle is performed in the frequency domain. A two degree of freedom system is used to represent a simple vehicle model in order to derive the system transfer function. The transfer function is defined between a steering angle input and a yaw rate output. This model shows the simplest lateral dynamic effect and is useful for understanding of the dynamic characteristics and control aspect of the target system. Vehicle mass, inertia, cornering stiffiness, and wheel base are selected as design variables. Sensitivity functions of the transfer function with repect to design variables are derived, and the results show that the response of the yaw rate always has stable minimum phase characteristics. The objective of this paper is the proposition of a base for re-design and new-design of the vehicle by checking the yaw rate variations with respect to the design variable change in the frequency domain. Finally, dominant design variables can be selected based on the sensitivity analysis.     

基于径向基函数的动网格技术应用研究

综合分析了基于径向基函数的动网格技术,利用紧支径向基函数构造位移插值函数,推导了位移传递矩阵,使得流场空间节点的位移插值只依赖于物面节点运动。通过一种基于贪婪算法的节点缩减算法与并行技术解决了该方法计算时间长、占用存储空间大的缺点。针对物面变形较大和构型复杂的情况,该技术可很好的完成网格变形。数值算例表明:应用该技术同时适用于结构以及非结构网格,且网格变形前后质量变化不大。     

Sensitivity analysis of side slip angle for a front wheel steering vehicle: a frequency domain approach

In this paper, sensitivity analysis of side slip angle for a front wheel steering vehicle is performed in the frequency domain. For the derivation of the transfer function, a simple vehicle model with two degrees of freedom is used in the initial modeling stage. This model exhibits the simplest lateral dynamic effect, and is useful for understanding the dynamic characteristics and control aspects of the target system. Vehicle mass, inertia, cornering stiffness, and wheel base are taken to be the design variables. Sensitivity functions of the transfer function with respect to the design variables are derived. From this study, we see that a transition speed exists in the frequency response of side slip angle. This implies that the characteristics are changed from minimum phase to non-minimum phase as the vehicle speed increases. The objective of this study is to propose a basis for design and re-design of the vehicle by checking the side slip angle variations with respect to design variable changes in the frequency domain. Finally, dominant design variables are suggested based on the sensitivity analysis.     

柔性递纸机构的动态设计方法研究

作为单张纸胶印机的关键部件——递纸机构的力学性能将直接影响着印刷的速度和印品的质量。本文以北京市第二印刷机械厂八开高速胶印机的摆动式递纸机构为工程背景 ,基于有限元理论 ,将运动周期离散化 ,建立的动力学模型为一系列系数时变的微分方程 ,并用 Newm ark方法求解其位移与应力的动态响应 ,为分析解决高速胶印机的磨损、振动和噪声等现象提供依据 ,也为柔性递纸机构的设计提供参考。     

OPTIMAL CONTROL OF THE FLEXI- BLE LINK MANIPULATOR WITH CONTROLLABLE LOCAL DEGREES OF FREEDOM

Although flexible manipulators own many potential advantages, one of their major disadvantages is the deterioration of the end-effector accuracy due to the flexibility. Therefore, how to reduce vibration is a significant problem. Inspired by the observation on the motion behaviors of animals, a new idea of decreasing motion deflection of the flexible manipulator is suggested. The concept of controllable local degrees of freedom is proposed and analyzed. By way of optimizing local motion provided by the controllable local degrees of freedom, the end-effector deflection of the flexible manipulator can be effectively decreased through dynamic coupling. The corresponding optimal method for vibration control of the flexible manipulator is put forward. The kinematic simulation is carried ant on a three-link flexible manipulator The corresponding results verify the feasibility of this method.     

自动调平试验台的机构结构设计分析

文中对自动调平试验台进行了机构分析,利用空间自由度分析方法,得出试验台的空间自由度,从而确定试验台的运动功能,进而确定原动件以及具有可以实现空间调平功能的结构.