考虑不确定性的激光切割机床主体机构多目标可靠性优化设计

发布时间：2018-04-05 13:49

本文选题：并联机构　切入点：多目标优化设计　出处：《山东理工大学》2017年硕士论文

【摘要】：并联机构在设计、制造、使用过程中存在着不确定性因素的影响,在忽视不确定性因素影响的多目标优化过程中,不确定性因素会在多个目标函数间传播累积,最终使得并联机构的需求性能产生波动,可靠性降低。因此,为了满足实际工程中对并联机构可靠性的要求,需将考虑不确定性的可靠性优化设计引入到并联机构的多目标优化设计中。本文以并联机构在激光切割机床主体机构方面的应用为例,将考虑不确定性的可靠性优化设计引入到激光切割机床主体机构的多目标优化设计中,以此提高激光切割机床的精度和可靠性。主要研究内容如下:(1)为了将并联机构优势与激光切割机床向着高速、精密的发展趋势相结合,本文以竖式3-PUU并联机构作为激光切割机床主体机构。对3-PUU并联机构进行运动学和动力学理论分析。包括互易螺旋理论为基础的运动特征分析,通过几何约束方程求得机构位置方程,采用三维极坐标搜索法得到该机构的工作空间图。以虚设机构法求得并联机构的Jacobian矩阵和Hessian矩阵,基于影响系数法对3-PUU并联机构进行运动学分析,通过牛顿-欧拉法建立3-PUU并联机构的逆动力学模型。(2)为了保证并联机构运动学和动力学理论分析的正确性,利用Matlab数值计算和Adams虚拟建模进行联合仿真,两种仿真形式所得曲线相吻合,保证了运动学和动力学理论分析的正确性和仿真结果的可靠性,同时验证了3-PUU并联机构用作激光切割机床主体机构的适用性,为性能指标的建立提供了正确的理论基础。(3)为了提高并联机构的整体性能,对其开展多目标优化研究。根据3-PUU并联机构的服役环境和性能需求,以工作空间、速度全域性能、加速度全域性能、惯性力全域性能等方面性能指标为目标函数,构建多目标优化数学模型。采用基于Isight的第二代非劣排序遗传算法(NSGA-II)对设计空间进行Pareto搜索,平衡各性能的实际需求,在可行性设计点中选取最优Pareto解,使得机构整体性能最优。(4)为了保证并联机构的可靠性要求,采用基于Isight的6 Sigma优化的方式来管理3-PUU并联机构中随机不确定性因素。首先运用概率论的方法分析量化不确定性因素,并建立考虑不确定性的多目标优化模型。然后在多目标优化的基础上,基于Isight对并联机构进行6 Sigma优化。最后通过可靠性分析对比6 Sigma优化前后需求性能的可靠度,经过对比可以得到6 Sigma优化所得优化结果更加可靠,更切合实际工程需求。本课题的研究不仅能够促进激光加工技术的发展,而且能够弥补并联机构传统优化设计中忽视不确定性因素影响的不足,使得并联机构设计优化更加接近工程实际,对提高我国并联机构的设计能力和设计质量具有一定的指导意义。
[Abstract]:In the process of design, manufacture and use of parallel mechanism, there are uncertain factors. In the process of multi-objective optimization, uncertainty factors propagate and accumulate among multiple objective functions.Finally, the demand performance of the parallel mechanism fluctuates and the reliability decreases.Therefore, in order to meet the requirement of reliability of parallel mechanism in practical engineering, it is necessary to introduce the reliability optimization design considering uncertainty into the multi-objective optimization design of parallel mechanism.Taking the application of parallel mechanism in laser cutting machine tool as an example, the reliability optimization design considering uncertainty is introduced into the multi-objective optimization design of laser cutting machine tool body mechanism.The accuracy and reliability of laser cutting machine are improved.The main research contents are as follows: (1) in order to combine the advantage of parallel mechanism with the developing trend of laser cutting machine towards high speed and precision, the vertical 3-PUU parallel mechanism is used as the main mechanism of laser cutting machine in this paper.The kinematics and dynamics of 3-PUU parallel mechanism are analyzed.The kinematic characteristic analysis based on the reciprocal helix theory is included. The position equation of the mechanism is obtained by geometric constraint equation, and the workspace diagram of the mechanism is obtained by using the three-dimensional polar coordinate search method.The Jacobian matrix and Hessian matrix of parallel mechanism are obtained by virtual mechanism method, and the kinematics of 3-PUU parallel mechanism is analyzed based on influence coefficient method.The inverse dynamic model of 3-PUU parallel mechanism is established by Newton-Euler method. In order to ensure the correctness of kinematics and dynamics theory analysis of parallel mechanism, Matlab numerical calculation and Adams virtual modeling are used for joint simulation.The curves obtained from the two simulation forms are consistent, which ensures the correctness of kinematics and dynamics theory analysis and the reliability of simulation results. At the same time, the applicability of 3-PUU parallel mechanism as the main mechanism of laser cutting machine is verified.In order to improve the overall performance of parallel mechanism, multi-objective optimization research is carried out.According to the service environment and performance requirements of 3-PUU parallel mechanism, a multi-objective optimization mathematical model is constructed by taking the workspace, velocity global performance, acceleration global performance and inertia force global performance as objective functions.The second generation noninferior sorting genetic algorithm (NSGA-IIs) based on Isight is used to search the design space for Pareto, to balance the actual demand of each performance, and to select the optimal Pareto solution in the feasible design point.In order to ensure the reliability of the parallel mechanism, a 6 Sigma optimization method based on Isight is adopted to manage the random uncertainty factors in the 3-PUU parallel mechanism.Firstly, the method of probability theory is used to analyze the uncertainty factors, and a multi-objective optimization model considering uncertainty is established.Then on the basis of multi-objective optimization, the parallel mechanism is optimized by 6 Sigma based on Isight.Finally, through the reliability analysis and comparison of the reliability of the requirement performance before and after 6 Sigma optimization, the optimization results obtained from the 6 Sigma optimization are more reliable and more suitable for practical engineering requirements.The research of this subject can not only promote the development of laser processing technology, but also make up for the deficiency of ignoring the influence of uncertain factors in the traditional optimization design of parallel mechanism, which makes the design optimization of parallel mechanism more close to the engineering practice.It has certain guiding significance to improve the design ability and design quality of parallel mechanism in our country.
【学位授予单位】：山东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG485

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