【作者】 彭鹏；

【导师】 王太勇；

【作者基本信息】 天津大学 ， 机械工程， 2021， 硕士

【摘要】 五轴联动数控加工可实现对刀具姿态的柔性控制,是加工复杂结构尤其含有曲率急变曲面零件的重要手段,在国防、运输和航天等领域有着广泛应用。由于增加的两个旋转轴,使得刀具在两刀位点间会存在非线性运动从而产生非线性误差,该误差不仅存在于刀尖点,也存在于刀轴方向上,不同的加工工艺对这两种误差的敏感度不同,如果对其没有针对性的优化则会影响加工精度和加工效率。对此本文主要研究内容包括:1.根据两类误差关联因素的不同,提出一种在后处理阶段和数控系统实时插补阶段分别控制刀轴方向非线性误差(TONE)和刀尖点非线性误差(TTNE)的策略,以实现在最终的加工中两类非线性误差的同步控制。2.在刀轴方向非线性误差控制中首先分析了该误差的成因,给出了通用计算方法,并提出了以误差阈值反推刀具姿态矢量坐标步长来插值角度坐标的方法,实现控制误差的同时最小化刀位点数量,从而最大化加工效率。3.在刀尖点非线性误差的计算算法中,面向不同类型五轴机床提出一种基于旋量理论的空间分区域解耦刀尖轨迹通用几何计算方法,该方法引入四个标准坐标系,按规则建立后将五轴机床划分为三个以旋转关节界定的空间区域,并通过对刀尖理论与实际轨迹的同一区域转换对比,充分解释了各类结构五轴机床的刀尖点非线性误差成因。对于刀尖点非线性误差的控制采用针对不同刀位点以允许误差所对应的进给速度作为数控系统速度规划元目标速度的方法,实现在实时加工中该误差的自适应控制。在最后的实验环节,以刀具姿态为AC角度为例在MATLAB软件中分别以单段和多段刀位路径两种方式验证了刀轴方向非线性误差的计算与控制算法,并横向对比了最新文献以体现本文控制算法的优势。以AC双转台结构、BC双摆头结构和B摆头C转台结构三种代表性配置的五轴机床在VERICUT软件中验证了刀尖点非线性误差的计算算法,在MATLAB中结合S型加减速算法验证了该误差的控制算法。最后还进行了两种误差同步控制的总体对比实验。总体结果表明本文提出的一组针对两类非线性误差的控制流程与算法在控制误差的同时最大化加工效率,可应用于大多数结构五轴机床的加工中。更多还原

【Abstract】 Five-axis computer numerical machining(CNC)can flexibly control the tool orientation.It is an important machining method for complex structures,especially parts with sharply changing curvatures.It is widely used in the fields of national defense,transportation and aerospace.Due to the two additional rotary axes,the tool will have nonlinear movement between the two tool positions,resulting in nonlinear errors.The error not only exists at the tool tip point,but also in the tool orientation.Different machining techniques have different sensitivity to these two errors.If there is no targeted optimization for nonlinear errors,it will affect the machining accuracy and efficiency.The main research contents of this paper include:1.According to the difference of the two types of error-related factors,a strategy is proposed to control the tool orientation nonlinear error(TONE)and the tool tip nonlinear error(TTNE)in the post-processing stage and the real-time interpolation stage of the CNC system respectively.Realize the synchronous control of two types of nonlinear errors in the final machining.2.The cause of the TONE has been analyzed,a general calculation method is given,and a method of interpolating the tool orientation angle coordinate by using the errorlimited value to determine the tool orientation vector coordinate step is proposed to realize the TONE’s control.The number of cutter location points is minimized to maximize machining efficiency.3.A general geometric calculating method based on the screw theory is proposed to determine the TTNE value for five-axis machine tools with various configurations by partitioning machine tool spatial zones and decoupling the tool tip trajectory.The method introduces four standard coordinate systems.The five-axis machine tool is divided into three space areas defined by the rotary joint after setting the standard coordinate systems.By comparing the theoretical and actual trajectory of the tool tip in the same area,it fully explains the TTNE of the five-axis machine tool with various structures.For the control of TTNE,the feed rate corresponding to the allowable error is used as the target feedrate of the numerical control system during two cutter location points to realize the adaptive controlling of the error in real-time machining.After the theoretical deduction,taking the tool orientation as AC angle’s form as an example,the calculation and control algorithm of the TONE were verified in MATLAB software in two ways of single-segment and multi-segment tool path,and the latest paper’s method was compared to this paper’s to reflect the advantages of the control algorithm in this paper.The five-axis machine tool with three representative configurations such as AC table-tilting,BC spindle-tilting and B spindle/C table-tilting structure has verified the calculation algorithm of the TTNE in the VERICUT software,and combined the S-type acceleration and deceleration algorithm in MATLAB verifies the error control algorithm.Finally,the overall comparison experiment of two kinds of error synchronization control is carried out.The overall results show that a set of control procedures and algorithms for two types of nonlinear errors proposed in this paper can maximize the machining efficiency while controlling the errors,and can be applied to the machining of most structural five-axis machine tools.更多还原