Stewart平台6-UPS并联机构动力学建模与仿真

以6-UPS并联机构为研究对象,推导了并联机构的动力学方程.在给定动平台运动轨迹的情况下,用龙格库塔方法求解动力学微分方程.计算结果验证了并联机构动力学建模正确,控制器设计合理.     

一种刚柔结合并联机构及其动力学分析

并联机构由于铰链的存在,使得其理论上的高精度高刚度的特点受到很大影响.本文在一种4自由度并联机构基础上,附加柔索随动机构,构建了一种刚柔结合的并联机构,通过预紧减少传动间隙,并对新机构的相关特性进行了分析.对该机构采用D-H坐标对该机床各支链进行了表述,采用牛顿-欧拉法建立了机构的动力学模型.最后采用Matlab对该动力学模型进行了仿真分析.     

复合驱动并联机构的动力学建模与仿真分析

针对一种■自由度复合驱动并联机构的刚体动力学建模问题,采用拉格朗日法结合虚功原理建立刚体动力学模型并进行仿真分析。首先,在考虑存在次闭环的情况下,采用闭环矢量法对并联机构进行运动学分析,推导出机构各构件质心的线速度和角速度;其次,采用拉格朗日法结合虚功原理建立复合驱动并联机构的刚体动力学模型,为复合驱动并联机构驱动力的求解及后续动力学仿真分析奠定了基础;最后,基于MATLAB软件和ADAMS软件对该并联机构进行动力学仿真分析,在给定相同末端轨迹的情况下,对比两种软件得到的驱动力变化曲线,仿真结果验证了所建动力学模型的正确性。文中不仅为■自由度复合驱动并联机构控制系统的搭建打下了基础,也为其他复合驱动并联机构的动力学建模分析提供了理论依据。     

一种新型自行车机器人机构设计及其建模

针对自行车机器人运动的侧向不稳定性,模仿人骑自行车的动力学特征,充分利用并联机构的结构紧凑、刚度大、响应速度快、承载能力强的特点,提出了一种基于2-RHR型冗余驱动并联机构进行自行车机器人侧向稳定调节的方法,系统地阐述了并联机构侧向调节方式的可行性和优越性.最后,运用第一类拉格朗日方程建立了系统动力学模型,为进一步的动力学及控制策略研究奠定了基础.     

基于牛顿-欧拉法的4-UPS-UPU并联机构动力学方程

采用牛顿-欧拉法建立了空间并联机构的动力学方程,用于研究4-UPS-UPU五自由度空间并联机构的刚体动力学建模。分析了4-UPS-UPU并联机构的支链受力和动平台受力情况,基于牛顿-欧拉法推导出了该并联机构的刚体动力学方程。利用Matlab分别对动平台在空载和加载条件下的驱动力进行理论计算,得到了该机构5个驱动杆的驱动力。最后,利用ADAMS对4-UPS-UPU并联机构虚拟样机进行了动力学仿真分析。结果表明:并联机构在Z轴为0.95m的平面内按半径为0.01m的圆轨迹运动时,驱动杆1受力最大,空载时最大值达-760.6N,加载时最大值达-889.7N。理论计算结果和虚拟样机仿真结果基本一致,验证了理论模型的正确性。该项研究为4-UPS-UPU五自由度并联机构物理样机的制造奠定了理论基础,也为其他空间并联机构刚体动力学建模提供了思路。     

并联机构机电耦合动力学计算

并联机构动力学模型是一个多输入、多输出、非线性、强耦合的复杂机电系统,目前还没有一个成熟的并联机构动力学建模和仿真计算方法.针对三自由度并联机构,建立了包括机械机构、伺服电机一体化的动力学模型.最后在设计好的运动平台轨迹下,计算了移动腿的位移、驱动电机的负载转距;分析了移动腿的误差.计算机仿真结果展示了控制器对机构位移和伺服电机转距良好的控制.     

Tricept并联机构的弹性动力学性能

针对Tricept并联机构在加工过程中的振动现象,文中对其弹性动力学性能开展了研究。利用动态子结构综合法建立了基于Lagrange方程的Tricept并联机构的弹性动力学模型。根据Tricept并联机构自身结构特点对其进行单元划分,分别利用有限单元法构造各支链弹性单元动力学模型,并结合变形协调条件和动力学约束,建立整机弹性动力学解析模型。根据该弹性动力学模型,得到了Tricept并联机构在其工作空间内的固有频率特性和末端刚度。所建立的模型便于探讨机构结构参数对系统动态特性的影响规律,从而为这类并联机构的动态设计提供理论依据。     

空间刚柔耦合并联机构系统的频率特性分析

对空间刚柔耦合并联机构系统的固有频率特性进行分析.建立一种空间有限元梁单元新模型,基于有限元法和Lagrange 方程导出有限元梁单元的运动微分方程.通过分析动平台运动参量与运动支链间的运动关系,得到刚柔耦合并联机构系统的运动学约束条件,并由Newton-Euler方程得到系统动平台的动力学模型.根据系统的运动学约束条件和动平台的动力学模型,经过各个单元运动微分方程的有机组装,导出刚柔耦合并联机构系统的整体动力学方程.在此基础上,通过算例3-RRS刚柔耦合并联机构系统的频率特性分析,总结空间刚柔耦合并联机构系统的固有频率与机构基本参量之间的内在规律.结果显示,刚柔耦合并联机构系统的结构尺寸、支链中杆件的截面参量和材料参量等对系统的固有频率都有显著影响.研究对进一步研究刚柔耦合并联机构的动态特性和机构优化设计具有重要的指导意义.     

基于凯恩方程的并联运动平台多刚体动力学建模

运动范围大、精度高的并联运动平台是对接机构综合试验台的重要子系统.由于该并联运动平台的液压缸的质量较大而负载质量较小,因此在进行并联运动平台的受力分析时必须建立起包含液压缸影响的多刚体动力学模型.本文先建立了并联运动平台的运动学方程,然后运用凯恩方程推导了并联运动平台的多刚体动力学模型,最后运用该模型对并联运动平台的受力进行了仿真计算,计算结果表明液压缸的质量和惯量对并联运动平台受力的影响很大、不允忽略.所得结果可作为对接机构综合试验台并联运动平台优化设计的依据.     

6-SPS型并联机构的混合坐标动力学建模

研究6-SPS型并联机构的动力学建模方法,提出了一种新颖的混合坐标动力学建模方法,根据6-SPS型并联机构特点,以四元数和笛卡尔坐标来定义6根支杆和动平台的方位及位置坐标,然后运用第一类拉格朗日方程建模方法建立了6-SPS型并联机构动力学模型,所建立的动力学模型形式简洁,体现了并联机构各向同性的特点,而且又发挥了四元数在数值计算上的优越性,因此具有适合计算机大规模编程计算的优点.     

A flexure-based mechanism and control methodology for ultra-precision turning operation

This paper presents the methodology for modeling and control of a high precision flexure-based mechanism for ultra-precision turning operation. A high performance piezoelectric actuator is used to driven the flexure-based mechanism. A parallel flexure hinge mechanism is utilized to guide the moving platform and to preload the piezoelectric actuator. A high resolution capacitive sensor is used to measure the displacement of the flexure-based mechanism for closed-loop control. With consideration of the driving circuit, the dynamic model of the flexure-based mechanism has been established. The effect of the driving circuit on the dynamic response of the precision mechanism is investigated. Experimental tests have been carried out to verify the established model and the performance of the flexure-based mechanism.     

并联机构动力学建模及控制策略的研究

在总结并联机构动力学分析目标的基础上,对并联机构的动力学建模方法,包括拉格朗日方法、牛顿-欧拉法、虚功原理、凯恩方程法等进行了比较研究,并对控制策略的研究现状进行了综述。     

Connection Method for Dynamic Modelling and Simulation of Parallel Kinematic Mechanism (PKM) Machines

The design of a PKM (parallel kinematic mechanism) machine usually concentrates on a kinematic analysis but its dynamic control behaviour is not paid equal attention, so there is a need to model a PKM machine dynamically. This paper presents a connection method for dynamic modeling of a PKM machine by introducing active and passive matrices. Using computer algebra, this method makes the dynamic modeling processes available, even though the kinematic constraint Eq. cannot be solved as analytical solutions. The modeling is used succesfully for a planar PKM machine, called PAMELA (parallel mechanism with linear actuators). Using dynamic modeling and simulation, we can anticipate the dynamic behaviour of the PAMELA machine and develop a suitable algorithm for the motion control. This enables a better dynamic configuration of the PAMELA machine to be obtained. As a consequence, it speeds up the design process and reduces the development cost before a physical machine is built. RID=" ID=" <E5>Correspondence and offprint requests to</E5>: Dr Q. Huang, Department of Manufacturing Systems, The Royal Institute of Technology, 100 44 Stockholm, Sweden. E-mail: qhu&commat;cadcam.kth.se     

State-of-the-art on theories and applications of cable-driven parallel robots

Cable-driven parallel robot (CDPR) is a type of high-performance robot that integrates cable-driven kinematic chains and parallel mechanism theory. It inherits the high dynamics and heavy load capacities of the parallel mechanism and significantly improves the workspace, cost and energy efficiency simultaneously. As a result, CDPRs have had irreplaceable roles in industrial and technological fields, such as astronomy, aerospace, logistics, simulators, and rehabilitation. CDPRs follow the cutting-edge trend of rigid–flexible fusion, reflect advanced lightweight design concepts, and have become a frontier topic in robotics research. This paper summarizes the kernel theories and developments of CDPRs, covering configuration design, cable-force distribution, workspace and stiffness, performance evaluation, optimization, and motion control. Kinematic modeling, workspace analysis, and cable-force solution are illustrated. Stiffness and dynamic modeling methods are discussed. To further promote the development, researchers should strengthen the investigation in configuration innovation, rapid calculation of workspace, performance evaluation, stiffness control, and rigid–flexible coupling dynamics. In addition, engineering problems such as cable materials, reliability design, and a unified control framework require attention.     

并联机器人研究现状

并联机器人是一类全新的机器人,它具有刚度大、承载能力强、误差小、精度高、自重负荷比小、动力性能好、控制容易等一系列优点,因而扩大了整个机器人的应用领域。本文综述了并联机器人的研究现状;包括并联机器人的特点,运动学建模,动力学建模,应用状况等。     

ON THE DYNAMIC MODELING AND CONTROL OF 2-DOF PLANAR PARALLEL MECHANISM WITH FLEXIBLE LINKS

The object of study is about dynamic modeling and control for a 2 degree-of-freedom (DOF) planar parallel mechanism (PM) with flexible links. The kinematic and dynamic equations are established according to the characteristics of mixed rigid and flexible structure. By using the singular perturbation approach (SPA), the model of the mechanism can be separated into slow and fast subsystems. Based on the feedback linearization theory and input shaping technique, the large scale rigid motion controller and the flexible link vibration controller can be designed separately to achieve fast and accurate positioning of the PM.     

基于SimMechanics的三自由度并联打磨机构动力学分析与仿真

针对一种新型三自由度并联打磨机构进行了运动学和动力学分析,并借助于MatLab/SimMechanics 工具箱的系统动态建模功能,搭建了一精确的仿真平台.结果表明:当并联打磨机构末端受广义力矢量作用时,在仿真平台上对系统进行Lagrange方法的动力学仿真分析,示波器跟踪动平台中心点的位置、速度及加速度,从而获得驱动...     

一种6-DOF冗余驱动并联机器人模型分析与运动控制

主要研究8输入6-DOF冗余驱动并联机器人的动力学特性和运动控制方法,首先描述了该机器人的运动学约束条件,并分析其运动学特性;随后采用拉格朗日法建立机器人动力学模型,并设计模糊自适应PID控制器。最后运动学模型、动力学模型及模糊PID控制器进行了仿真,验证了模型的正确性和控制方法的有效性,为并联机器人参数选取和控制方案制定提供依据。     

Compound Impedance Control of a Hydraulic Driven Parallel 3UPS/S Manipulator

The hydraulic parallel manipulator combines the high-power density of the hydraulic system and high rigidity of the parallel mechanism with excellent load-carrying capacity. However, the high-precision trajectory tracking control of the hydraulic parallel manipulator is challenged by the coupling dynamics of the parallel mechanism and the high nonlinearities of the hydraulic system. In this study, the trajectory control of a 3-DOF symmetric spherical parallel 3 UPS/S manipulator is evaluated. Focusing on the highly coupling and nonlinear system dynamics, a compound impedance control method for a hydraulic driven parallel manipulator is proposed, which combines impedance control with the spatial motion characteristics of a parallel manipulator. The control strategy is divided into the inner and outer loops. The inner loop controls the impedance of the actuator in the joint space, and the outer loop controls the impedance of the entire platform in the task space to compensate the coupling of the actuators and improve the tracking accuracy of the moving platform. Compound impedance control does not require force or pressure sensors and is less dependent on modeling precision. The experimental results show that the compound impedance control e ectively improves the tracking accuracy of the moving platform. This research proposes a compound impedance control strategy for a 3-DOF hydraulic parallel manipulator, which has high tracking precision with a simple and cheap system configuration.