基于复杂零件夹紧表面的夹紧力全区域规划

发布时间：2018-01-22 07:18

本文关键词： 夹紧力力的存在性力的可行性阈值离散化迭代　出处：《南昌航空大学》2017年硕士论文　论文类型：学位论文

【摘要】：研究机械加工过程中夹紧力的合理规划是保证加工质量的核心环节,对于实现加工过程中夹紧力的可靠性和工件的精密化至关重要,为此构建了全区域夹紧力变向迭代规划算法。根据工件在装夹布局中的受力状态以及工件与装夹元件之间接触力的方向约束条件,分别依据夹紧力大小与夹紧点位置的未知和已知情况,结合线性规划技术分别建立了有静摩擦力和无静摩擦力的力的存在性和力的可行性分析方法。在夹紧力存在的条件下,通过离散夹紧表面为点集的方法,逐点地以一定步长正向从最小值开始选取夹紧力的大小,根据当前值与上一次取值之间可行性的差异,确定下一次取值的步长及其方向,若可行性相同则以相同步长继续正向取值,否则步长减少、反向取值,直至步长的绝对值小于阈值,建立全区域夹紧力的变向迭代规划算法,该算法将连续型的夹紧力设计问题转化为离散型,并将连续的待装夹表面转化为点集,不仅适合于形状复杂的工件,而且还利于计算机实现夹紧力的自动化设计。对于当单一夹紧力不能使工件在加工过程中稳定,需要多点装夹的情况。提出了多夹紧力迭代规划算法。通过用合力和投影角度表达每个夹紧力。并以判断该合力下是否至少存在一组夹紧力组合使工件稳定为迭代标准。若此次迭代标准与上次相同时,则迭代步长和迭代方向不变。若不同则迭代步长缩小并反向迭代。直至步长的绝对值在给定的阈值范围内。针对迭代规划算法的参数选取问题,本文以最少的计算次数为目标函数,运用遗传算法将迭代规划算法中的三个参数进行优化。旨在提高算法的效率。基于复杂零件夹紧表面的夹紧力全区域规划不仅适用于具有复杂表面的工件,而且能够避免工件处于非稳定状态下优化模型的求解过程。提高了计算效率,使夹紧点与夹紧力的选取有了一个计算标准,为复杂工件装夹布局方案的合理设计提供了基础理论。多夹紧力迭代规划算法则能搜寻出多个夹紧力共同作用下每个夹紧力的取值范围,为需要多点装夹的工件的夹紧力选取提供力选取标准。
[Abstract]:To study the reasonable planning of clamping force in machining process is the core link to guarantee the quality of machining, and it is very important to realize the reliability of clamping force and the precision of workpiece in the process of machining. For this purpose, an iterative programming algorithm for the whole area clamping force is constructed. According to the stress state of the workpiece in the clamping layout and the direction constraint condition of the contact force between the workpiece and the clamping element. According to the magnitude of clamping force and clamping point position unknown and known. Combining with linear programming, the existence and feasibility analysis method of static friction force and non-static friction force are established respectively. Under the condition of the existence of clamping force, the discrete clamping surface is used as the point set method. According to the feasibility difference between the current value and the last value, the step size and direction of the next value are determined according to the feasibility of selecting the clamping force from the minimum to a certain step. If the feasibility is the same, the same step size will continue to take forward value, otherwise the step size will be reduced, the reverse value, until the absolute value of step size is less than the threshold, the variable direction iterative programming algorithm of the whole region clamping force will be established. The algorithm transforms the continuous clamping force design problem into the discrete one, and transforms the continuous clamping surface into the point set, which is not only suitable for the complex workpiece. It is also helpful for the computer to realize the automatic design of clamping force. When the single clamping force is not able to make the workpiece stable in the process of processing. An iterative programming algorithm for multiple clamping forces is proposed. Each clamping force is expressed by the resultant force and projection angle, and it is determined whether there is at least one set of clamping forces under the combined force to make the workpiece stable. If this iteration standard is the same as the last time. Then the step size and the direction of iteration are unchanged. If not, the step size of the iteration is reduced and the iteration is reversed. The absolute value of the step size is within a given threshold. The parameter selection problem of the iterative programming algorithm is addressed. This paper takes the least number of calculations as the objective function. Genetic algorithm is used to optimize the three parameters of the iterative programming algorithm. In order to improve the efficiency of the algorithm, the whole area planning of clamping force based on the clamping surface of complex parts is not only suitable for the workpiece with complex surface. Moreover, it can avoid the process of solving the optimization model in unstable state, improve the calculation efficiency, and make the selection of clamping point and clamping force have a calculation standard. The iterative programming algorithm of multiple clamping forces can find out the value range of each clamping force under the combined action of multiple clamping forces. The selection standard of clamping force is provided for multi-point clamping workpiece.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG75

【参考文献】