微小线段高速加工的轨迹优化建模及前瞻插补技术研究

发布时间：2018-12-06 08:26

【摘要】：高速加工技术在航空航天、汽车、模具等制造业中应用广泛,是提高加工质量和效率的重要手段,国际生产工程学会(CIRP)将高速加工技术确定为21世纪制造技术的中心方向之一。微小线段是叶轮、叶片、模具等复杂曲面零件加工路径的最广泛表达形式,微小线段路径高速加工已成为复杂曲面零件高速加工核心技术之一。微小线段路径中转角一阶不连续特性会导致频繁加减速,成为数控机床高速平稳运动的瓶颈。连续微小线段转角速度平滑和跨段速度规划是连续微小线段插补的最大难题,至今仍是先进数控系统制造商用于提高曲面加工效率和质量的热点技术。本文提出了一种G~2连续B样条全局光顺算法及插补技术,以及一种基于转角误差分配的连续微小线段转角局部光顺和转角速度优化方法,实现了基于前瞻窗口的连续微小线段实时光顺、转角速度优化和综合约束下跨段自适应速度规划,将上述方法集成于开放式数控系统中,实现了微小线段轨迹的高速加工,验证了本文所提出方法的有效性和实用性。主要研究内容和创新性成果如下:(1)提出了微小线段路径G~2连续全局光顺和线性/样条混合路径跨段加减速方法。运用三次B样条插值拟合算法实现了微小线段路径的数据压缩和G~2连续全局光顺;提出了基于减速特征方程的S曲线加减速策略,在满足机床加减速特性和刀路轨迹几何特性对进给速度及加速度约束下,对生成的线性/样条混合路径进行了跨段前瞻速度规划。该方法适用于短而数量多的密集线段路径和转角很小的平缓路径,可大幅提高进给速度平稳性和加工效率。勺模加工实验中,与不采用该方法相比,该方法提高加工效率约4倍。(2)建立了三轴线性刀具路径转角误差分配模型和转角速度优化方法。以获取最优转角过渡速度为目标,将系统设定精度分配为光顺近似误差和插补弓高误差,在误差约束下,用Bézier过渡曲线对(BTP)实现了线性路径转角的光顺,同时考虑机床各轴伺服能力约束,运用前瞻功能实现了微小线段刀路的实时插补。面具加工实验中,与不采用转角误差分配模型方法相比,在保证轨迹精度前提下,该方法可以将加工时间缩短25%。(3)建立了五轴工件坐标系下的线性刀具路径的转角误差分配模型和工作坐标下的线性刀具路径的G~2连续实时拟合方法。将系统设定精度分配为刀尖点和刀轴点的光顺近似误差和插补弓高误差,在线段连接处插入两条三次Bézier曲线,将工作坐标下的线性刀具路径实时拟合为G~2连续的双样条轨迹。该算法满足了近似误差约束、参数化同步约束和曲率连续约束等条件,进一步综合考虑曲线过渡误差与插补误差、最大切向加速度/加加速度、机床各轴伺服能力等约束条件,进行了自适应速度规划,实现了五轴微小线段的高速加工。通过仿真和实验,该算法在五轴线性刀具路径光顺、转角速度平滑、转角轨迹精度控制方面具有良好的效果。(4)研究了通过给伺服电机施加正反方向激励获取机床各轴速度-加速度包络图的实验方法。通过对包络图中速度和加速度可行范围分析,采用最大值匹配法和自适应匹配法,得到了优化的最大速度和最大加速度约束值,并将约束值应用于数控系统插补运算。(5)开发了基于多线程并发执行管理调度机制的开放式数控系统,并对本文高速微小线段插补算法进行了集成应用。将三次B样条全局光顺算法和基于转角误差分配模型Bézier转角过渡算法集成应用在广州数控GSK27全数字总线式高档数控系统中,实现了模具的高速加工。将基于五轴转角误差模型工件坐标系局部光顺算法和辨识的参数集成应用于广州数控GSK25i五轴联动加工数控系统中,应用于模具高速铣削和复杂空间曲线零件加工。
[Abstract]:High-speed machining technology is widely used in the manufacturing of aerospace, automobile, and mould. It is an important means to improve the processing quality and efficiency, and the International Institute of Production Engineering (CIRP) has identified the high-speed machining technology as one of the center of the manufacturing technology in the 21st century. The small line segment is the most widely used form of the machining path of complex curved surface parts such as the impeller, the blade, the die and the like, and the high-speed machining of the micro-segment path has become one of the core technologies of the high-speed machining of the complex curved parts. The discontinuous characteristic of the corner in the path of the micro-segment can lead to frequent acceleration and deceleration, which becomes the bottleneck of the high-speed and smooth movement of the numerical control machine. Continuous micro-segment rotation angular velocity smoothing and cross-section speed planning are the most difficult problem for continuous micro-line segment interpolation, and is still a hot spot technology for advanced numerical control system manufacturers to improve surface processing efficiency and quality. The invention provides a G-2 continuous B-spline global fairing algorithm and a interpolation technique, The method is integrated in the open-end numerical control system to realize the high-speed processing of the trace of the micro-segment, and the validity and practicability of the proposed method are verified. The main research contents and innovative results are as follows: (1) The method of continuous global fairing and linear/ spline hybrid path cross-section plus speed reduction is proposed. The data compression and G ~ 2 continuous global fairing of the path of the micro line segment are realized by using the cubic B-spline interpolation fitting algorithm, and the S-curve plus speed reduction strategy based on the deceleration characteristic equation is proposed, and the acceleration and deceleration characteristics of the machine tool and the geometric characteristics of the path of the tool path are met, A cross-segment forward speed planning is carried out on the generated linear/ spline mixing path. The method is suitable for a short and large number of dense line segment paths and smooth paths with small corners, and can greatly improve the feeding speed stability and the processing efficiency. In the ladle mold processing experiment, the method can improve the processing efficiency by about 4 times compared with the method without using the method. and (2) a three-axis tool path angle error distribution model and an angular velocity optimization method are established. in ord to obtain that transition speed of the optimal rotation angle as the target, the system setting precision is assign as the smooth approximation error and the interpolation arch high error, under the error constraint, the light of the linear path angle is realized by the B-Bezier transition curve pair (BTP), and the servo capability constraint of each axis of the machine tool is taken into account, and the real-time interpolation of the micro-segment knife path is realized by using the forward-looking function. in the mask processing experiment, the processing time can be shortened by 25%, compared with the method that does not adopt the corner error distribution model method, and the processing time can be shortened by 25% under the premise of ensuring the track precision. and (3) establishing a G-2 continuous real-time fitting method of a linear tool path under a five-axis workpiece coordinate system and a linear tool path under the working coordinate. The system setting accuracy is assigned as the light-to-close approximation error of the nose point and the knife-axis point and the high-error of the interpolation bow. Two cubic B-spline curves are inserted at the joint of the line segment, and the linear tool path under the working coordinate is fitted into the G-2 continuous double-spline track in real time. The method satisfies the conditions of approximate error constraint, parametric synchronization constraint and curvature continuous constraint, and further comprehensively considers the constraint conditions of the curve transition error and the interpolation error, the maximum tangential acceleration/ acceleration, the servo capability of each axis of the machine tool, and the like, and carries out the self-adaptive speed planning, and the high-speed machining of the five-axis micro-segment is realized. Through the simulation and experiment, the algorithm has good effect in the five-axis tool path fairing, the smooth rotation speed and the angle track precision control. (4) The experimental method of obtaining the velocity-acceleration envelope of each shaft of the machine tool by applying the positive and negative direction excitation to the servo motor is studied. By analyzing the feasible range of velocity and acceleration in the envelope graph, the maximum speed and the maximum acceleration constraint value are obtained by using the maximum matching method and the adaptive matching method, and the constraint value is applied to the interpolation operation of the numerical control system. (5) The open-end numerical control system based on multi-thread concurrent execution management and scheduling mechanism is developed, and the high-speed micro-segment interpolation algorithm is applied in this paper. The three-time B-spline global light-smoothing algorithm and the angle-based error distribution model B-Bezier-angle transition algorithm are integrated and applied in the full-digital bus-type high-end numerical control system of the Guangzhou numerical control GSK27, and the high-speed machining of the die is realized. The local fairing algorithm and the identification parameter integration of the workpiece coordinate system based on the five-axis corner error model are applied to the CNC GSK25i five-axis linkage processing numerical control system, and is applied to the machining of high-speed and complex space curve parts of the die.
【学位授予单位】：上海交通大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG659

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