基于复杂曲面铣削纹理变化改善的五轴机床几何误差补偿方法研究

Geometric error compensation has been becoming an important way to improve the accuracy of five-axis machining economically and effectively. For the existing technologies, tool poses are adjusted without considering the limitation of cutter contact points. What’s worse, the change of the machined surface textures caused by NC code modification in existing technologies has not yet been taken seriously. In fact, surface textures directly affect the mechanical performance and the physical property of the workpiece. With all the considerations, this proposal intends to study on geometric error compensation of five-axis machining where the tool orientations adjustment is driven by the improvement of the machined surface texture changes, which aims at improving the surface quality of workpieces as well as the accuracy of five-axis machining. At first, the transform mechanism of axis motion of five-axis machine tools with cutter contact points and the spatial trochoidal path of cutting edge are established. On these basis, the influences of axis motion modification during error compensation on the machined surface textures are proposed. Secondly, the integrated analytic geometric error model of five-axis machine tools is established, including the mathematical modeling of error components, the description of physical properties of error components and the representation of the integrated errors caused by local geometric errors of different axes. Thirdly, control strategies of changes of the machined surface textures are established, including the limiting method of cutter contact trajectories based on information of cutter contact points and the restricted regions of tool rotation angle and tool tilt angle. Finally, one optimization method of tool orientations is established according to chicken swarm optimization (CSO) for geometric error compensation. After that, one smoothing strategy of whole tool poses is developed. With all methods, the geometric error compensation system of five-axis machine tools is constructed. As a consequence, the changes of the machined surface textures can be improved while geometric errors of five-axis end milling are reduced. The implementation of this proposal can further enhance the accuracy of five-axis machine tools and surface texture quality of workpieces.

几何误差补偿是提高五轴加工精度经济有效的重要手段。现有技术在修正刀位时没有考虑刀触点限制，且对引起的曲面纹理变化缺乏认识与关注。而曲面纹理直接影响到工件机械性能和物理性能。本项目拟以提高曲面表面质量和五轴加工精度为目标，开展由曲面纹理变化改善来驱动刀具姿态修正的五轴几何误差补偿方法研究。依据基于刀触点的五轴运动量生成机制和关于刀具姿态角的切削刃三维摆线轨迹，探索误差补偿中运动量改变对曲面纹理影响机理；从误差元素性质描述、运动轴误差贡献值计算和误差元素数学建模入手，建立五轴机床高精度几何误差解析模型；引入刀触点信息提出刀触点保障策略，并结合曲面纹理的刀具姿态角可接受范围制定曲面纹理变化的控制策略；提出基于鸡群算法的刀具姿态优化方法和整体刀路光顺策略，搭建兼顾曲面铣削纹理变化控制的五轴几何误差补偿系统，在降低几何误差同时改善曲面纹理变化。本项目顺利实施将进一步提高五轴铣削精度和零件表面质量。

五轴机床在复杂曲面加工制造方面具有独特优势，已经广泛应用于航天、航空、航海、汽车、国防等领域，五轴高精度加工直接体现了一个国家的先进制造水平。几何误差和热误差补偿是提高机床精度和性能的主要手段之一，然而补偿中不加约束随意调整刀位会造成曲面纹理形貌发生意料之外的变化，曲面纹理形貌直接影响到工件机械性能和物理性能。本项目综合考虑曲面铣削纹理变化改善来开展五轴机床误差补偿方法的系统性研究。首先，构建了“曲面刀触点轨迹—刀具位姿—五轴铣削运动量”三者映射关系，阐明铣削运动量变化对曲面刀触点位姿影响机制；分析曲面纹理形貌形成机理建立曲面纹理上切削刃点表达式，构建曲面纹理形貌数字化预测模型，从而揭示误差补偿对曲面纹理形貌影响机制。然后，建立机床平动轴几何误差四路激光快速完整测量辨识方法，构建能够反映运动轴本身误差对机床精度影响的误差贡献值模型，提出以运动轴为对象的误差灵敏度分析方法，获得机床工作空间综合误差高精模型。在此基础上，提出了考虑机床不同热源影响基于数量自动化确定的温度敏感点选取方法，建立基于加权集成和CSO-RBF的主轴热误差模型。接着，建立曲面纹理形貌评价指标包括表面质量、纹理形貌质量和纹理整体走势三类指标并提出各类指标数字化提取方法；构建曲面纹理形貌质量评定及分类方法，获得每类曲面纹理形貌的刀具旋转角和倾斜角范围。最后，建立误差补偿中规划的刀触点轨迹保障策略，结合曲面纹理变化可接受程度的刀具旋转角和倾斜角范围，实现误差补偿中曲面加工纹理的约束和改善；在此基础上，建立整体刀路评价指标，提出刀具姿态优化和刀路光顺策略，构建曲面加工纹理变化改善约束下的五轴机床误差补偿系统，在降低误差影响同时保障曲面纹理形貌质量。本项目最终搭建了曲面纹理分析—机床误差测量—误差补偿—曲面加工及检测一体化系统，对于提高高端数控机床加工精度、丰富和完善先进制造理论无疑具有十分重要的学术研究意义，拥有广阔的市场前景。