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高速并联抓拿机械手性能分析及优化设计

作者:润色论文网  来源:www.runselw.com  发布时间:2019/9/24 9:52:48  

摘要:高速并联机械手在完成抓拿、搬运、分拣等重复性工作时,由于高速及高加速的原因,会产生一定幅度的振动和波动,从而影响机械手的工作精度。本文根据方位特征集(POC)理论,分别提出了两种可实现三平移(3T)运动和三平移一转动运动(SCARA)的高速并联抓拿机械手机构,对两种机构的运动学、动力学及刚度等性能进行了深入系统的研究,为高速并联机械手的优化设计及进一步工程应用奠定了理论基础。主要研究内容如下:

(1)提出三平移运动和三平移一转动两种新机构,运用封闭矢量法结合杆长约束求解其运动学正、反解方程,推导出速度和加速度矢量方程,并通过算例对运动学方程进行验证。

(2)分析机构各构件的速度、加速度以及在虚位移下的广义力,根据虚功原理建立两种机械手机构的逆动力学模型,采用Creo软件建立机构的虚拟模型,并通过ADAMS软件仿真验证了机构逆动力学模型的正确性。

(3)考虑机构各构件、运动副的弹性变形对机械手执行器末端的影响,根据虚拟弹簧法和螺旋理论,建立两种机构的刚度矩阵,分析机械手的线性刚度和扭转刚度特征,采用MATLAB编程绘制了机构的刚度曲线。通过有限元模型的变形分析验证了刚度模型的正确性。

(4)采用极坐标搜索法分别绘制两种机械手机构的工作空间以及规则任务工作空间,分析了机构在任务工作空间中的奇异性、灵巧度、运动/力传递性能、最大加速性能及刚度性能。

(5)研究了两种机械手机构的运动、动力及刚度性能评价指标及其数学表达式。以机械手的高速性能指标为约束,采用差分进化算法对其进行尺度参数优化,分别得到机构工作空间最优、加速性能最优及刚度性能最优时的结构参数。通过对比分析优化前后的性能图谱,表明本文所采用的性能指标算法及优化方法具有一定理论参考价值。

When high-speed parallel manipulatorcompletes repetitive work such as grasping, handling and sorting, due to thereasons of high speed and high acceleration, it will produce a certainamplitude of vibration and fluctuation, thus affecting the working accuracy ofthe manipulator.According to the theory of POC, two kinds of high-speedparallel grasping manipulators are proposed, which can realize threetranslations (3T) and three translations-one rotation (SCARA). The kinematics,dynamics and stiffness of the two mechanisms are studied systematically, whichlays a theoretical foundation for the optimization design and furtherengineering application of high-speed parallel manipulators. The main researchcontents are as follows:

(1) Two new mechanisms, 3T and 3T1R, areproposed. The closed vector method is used to solve the forward and inversekinematics equations, and the velocity and acceleration vector equations arederived. The kinematics equations are verified by an example.

(2) The velocity, acceleration andgeneralized force of each component of the mechanism under virtual displacementare analyzed. The inverse dynamics models of the two mechanisms are establishedaccording to the principle of virtual work. The virtual model of the mechanismis established by Creo software. The correctness of the inverse dynamics modelof the mechanism is verified by ADAMS software simulation.

(3) Considering the influence of theelastic deformation of components and pairs on the end of the manipulator, thestiffness matrices of the two mechanisms are established according to thevirtual spring method and the helix theory. The linear stiffness and torsionalstiffness characteristics of the manipulator are analyzed. The stiffness curvesof the manipulator are drawn by using MATLAB programming. The correctness ofthe stiffness model is verified by the deformation analysis of the finiteelement model.

(4)The polar coordinate search method isused to draw the workspace of two kinds of robot mechanisms and the regularworkspace respectively. The singularity, dexterity, motion/force transferperformance, maximum acceleration performance and stiffness performance of themechanism in the task workspace are analyzed.

(5)The motion, dynamic and stiffnessperformance evaluation indexes and their mathematical expressions of two kindsof mechanisms are studied. Constrained by the high-speed performance index ofthe manipulator, the differential evolution algorithm is used to optimize itsscale parameters, and the structural parameters are obtained when theworkspace, acceleration and stiffness of the manipulator are optimal. Bycomparing and analyzing the performance maps before and after optimization, itshows that the performance index algorithm and optimization method adopted inthis paper have certain theoretical reference value.

关键词:高速并联机械手;运动学;动力学;刚度;优化设计

high speed parallel manipulators;kinematics; dynamics; stiffness; performance analysis; optimization design

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