凸轮轮廓NURBS重构与工作特性优化研究

发布时间：2018-05-23 10:12

本文选题：凸轮轮廓 + NURBS重构　；参考：《山东农业大学》2014年博士论文

【摘要】：在自动机械中，凸轮机构主要用作传动、导向和控制元件，其运动、动力等工作特性对自动机械的精度、效率和速度有决定性影响。本文在全面分析国内外凸轮机构运动和动力特性研究的基础上，提出了一种新的凸轮机构设计和优化方法，该方法以非均匀有理B样条(non-uniform rational B-splines, NURBS)为工具，通过凸轮廓线、廓面NURBS重构，进一步改善和提高凸轮机构的运动和动力等工作特性，从而满足各类自动机械对高速、高精度工作的日益追求。 NURBS曲线曲面因其优良的全局表达性和强大的局部调控性，正逐渐引起工程界重视并在各领域得到应用。本文首先分析了NURBS曲线曲面的数学模型及其模型特性，设计了曲线曲面NURBS重构流程，，重点研究了NURBS曲线曲面控制参量节点矢量、权因子及控制顶点等各项参数的几何意义、对曲线曲面形状的影响及计算方法。其次，在研究NURBS曲线曲面重构方法的基础上，提出了凸轮廓面NURBS重构的设计方法。为提高空间凸轮廓面的建模和创成精度，利用直纹面和等距曲面理论分析了空间凸轮廓面的几何特性，基于单参数曲面包络理论，建立了空间凸轮廓面方程。利用空间分度凸轮廓面方程获取离散点云数据，实现了空间凸轮廓面NURBS重构，建立了空间凸轮参数化特征模型。基于该模型，进行空间凸轮分度机构运动特性优化与仿真，进而生成加工制造模型，实现空间凸轮NURBS廓面的仿真加工和四轴铣削NURBS高品质创成。再次，针对高速工况下凸轮机构动态特性变差的问题，利用NURBS曲线设计和优化凸轮机构从动件运动规律，进行高速凸轮廓线NURBS重构。采用动态分析方法，建立高速凸轮机构单自由度动态特性模型，推导了高速凸轮机构输入和动态输出之间的关系，获得了系统残余振动评价指标，由此建立了高速凸轮机构多目标动态特性优化模型。设计了集成禁忌搜索策略和变参数二次寻优思想的改进人工鱼群多目标优化算法。通过该算法对高速凸轮机构多目标动态特性优化模型寻优，以获取优化模型的Pareto最优解，藉此重构高速凸轮NURBS廓线，研究NURBS廓线高速凸轮机构的主振和余振响应，以降低系统的振动和冲击。最后，采用运动和动力性能集成优化方法，基于NURBS曲线进一步研究凸轮机构的动力接触特性。以摆动从动件固定凸轮机构为研究对象，分析了槽道凸轮残膜捡拾机构的工作特性，设计了适合机构的单停留修正正弦（Modifed Sine，MS）运动规律曲线，考虑运动副摩擦，建立槽道凸轮残膜捡拾机构的动力模型，根据赫兹接触理论得到槽道凸轮残膜捡拾机构的接触应力计算方程。采用NURBS曲线进行槽道凸轮残膜捡拾机构的运动特性设计，以接触应力和加速度为优化目标，利用改进人工鱼群算法进行多目标优化，优化结果和运动仿真表明：与单停留MS廓线相比，优化后NURBS廓线槽道凸轮残膜捡拾机构的加速度和接触应力较小，冲击和磨损较轻，提高了机构工作的可靠性和使用寿命。本文的研究结果为凸轮机构的设计与制造提供了一个新的方法和思路，对于提升我国中高端凸轮机构的研发水平，实现高端产品的国产化具有一定的理论研究价值和工程应用前景。
[Abstract]:In automatic machinery, the cam mechanism is mainly used as transmission, guidance and control elements, and its motion and dynamic characteristics have a decisive influence on the accuracy, efficiency and speed of automatic machinery. On the basis of a comprehensive analysis of the motion and dynamic characteristics of the cam mechanism at home and abroad, a new design and optimization method of the cam mechanism is proposed in this paper. The method uses the non-uniform rational B spline (non-uniform rational B-splines, NURBS) as a tool, through the cam profile and the reconstruction of the profile surface NURBS, to further improve and improve the working characteristics of the cam mechanism, such as motion and power, so as to meet the increasing pursuit of high speed and high precision work of various automatic machines.
Because of its excellent global expressiveness and strong local regulation, NURBS curve and surface are gradually attracting the attention of the engineering community and being applied in various fields. Firstly, the mathematical model and its model characteristics of NURBS curve and surface are analyzed. The NURBS reconstruction process of curve and surface is designed, and the control parameter node vector of NURBS curve and surface is studied. The geometric meaning of parameters such as quantity, weight factor and control point, and its influence on the shape of curve and surface and its calculation method are discussed.
Secondly, on the basis of studying the method of NURBS curve and surface reconstruction, the design method of NURBS reconstruction of cam profile is put forward. In order to improve the modeling and creating precision of the spatial cam profile, the geometric characteristics of the spatial cam profile are analyzed by the theory of the straight surface and the isometric surface. Based on the single parameter curved loaf theory, the spatial cam profile is established. Using the spatial indexing cam profile equation to obtain the discrete point cloud data, the spatial cam profile NURBS reconstruction is realized, and the spatial cam parameterized characteristic model is established. Based on this model, the motion characteristics of the spatial cam indexing mechanism are optimized and simulated, and then the processing model is generated to realize the simulation processing of the spatial cam NURBS profile surface. And four axis milling of NURBS high quality creation.
Thirdly, in view of the problem of the dynamic characteristics of cam mechanism in high-speed working condition, the NURBS curve is used to design and optimize the motion law of the cam mechanism, and the NURBS reconstruction of the high-speed cam profile is carried out. The dynamic analysis method is used to establish the dynamic characteristic model of the single degree of freedom of the high-speed cam mechanism, and the input and dynamic output of the high-speed cam mechanism are derived. The evaluation index of the residual vibration of the system is obtained, and the multi-objective dynamic characteristic optimization model of the high-speed cam mechanism is established. The integrated tabu search strategy and the variable parameter two optimization thought are designed to improve the multi target optimization algorithm of the artificial fish group. The algorithm is used to optimize the dynamic characteristics of the multi target dynamic characteristics of the high-speed cam mechanism. In order to obtain the optimal Pareto solution of the optimized model, the NURBS profile of the high-speed cam is reconstructed, and the main vibration and the residual vibration response of the high-speed cam mechanism of the NURBS profile are studied in order to reduce the vibration and impact of the system.
Finally, based on the integrated optimization method of motion and dynamic performance, the dynamic contact characteristics of the cam mechanism are further studied based on the NURBS curve. The working characteristics of the cam mechanism with swinging follower are taken as the research object. The working characteristics of the grooved cam residual membrane pickup mechanism are analyzed, and the Modifed Sine, MS motion gauge suitable for the mechanism is designed. According to the Hertz contact theory, the contact stress calculation equation of the grooved cam residual film pickup mechanism is obtained according to the Hertz contact theory. The motion characteristics of the grooved cam residual film pickup mechanism are designed by using the NURBS curve, and the contact stress and acceleration are used as the optimization target and the modification is used. The artificial fish swarm algorithm is used for multi-objective optimization. The optimization results and motion simulation show that the acceleration and contact stress of the cam residual membrane pickup mechanism of the optimized NURBS profile slot channel are smaller than the single MS profile, and the impact and wear are lighter, and the reliability and service life of the mechanism work are improved.
The results of this paper provide a new method and idea for the design and manufacture of the cam mechanism. It has a certain theoretical research value and engineering application prospect for improving the R & D level of the middle and high end cam mechanisms in China and realizing the localization of the high-end products.
【学位授予单位】：山东农业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH112.2

【参考文献】