叶片前后缘机器人砂带磨抛加工机理与技术基础研究

Focusing on the poor quality and the insufficient flexibility caused by the manual and multi-axis CNC machine tools grinding and polishing of leading and trailing edges of blade, respectively, a set of theory and method concerning the belt grinding and polishing of blade edges based on the industrial robot is proposed in this proposal. Aiming at the two major problems in the actual machining, the research on key mechanism and technology is carried out. Firstly, the theoretical methods including the hand-eye visual calibration, distance functions, etc., are employed to investigate the on-line measurement system calibration, path generation without scanning interference, point-cloud matching, thereby breaking the issues such as grinding chatter, over / less wear caused by the uneven allowance (Problem 1); Secondly, an optimization model of material removal rate based on the allowance distribution of blade edges is established, and then a precision force-position control method is proposed through rational planning of grinding path and effective control of workpiece gesture, aiming to solve the issues such as machining deformation of blade edges, local burn caused by the difficult-to-controlled contact force (Problem 2); Thirdly, a closed-loop controlled robotic grinding and polishing system platform is built to complete the grinding and polishing tests of the edges of different types of turbine blades and aviation blades. Through the above research, the theoretical methods, key technologies and processing solutions of "online measurement - allowance optimization - quality control" in robotic grinding and polishing of blade edges are expected to be applied in enterprise production.

针对当前手工磨抛叶片前后缘所导致的叶片质量差，以及多轴数控机床磨抛所带来的柔性不足，本项目提出一套基于工业机器人的叶片前后缘砂带磨抛理论与方法，并重点围绕实际加工中的两大难题，开展核心机理和工艺技术基础研究。应用手眼视觉标定、距离函数等理论方法，研究在线测量系统快速标定、扫描无干涉轨迹生成、点云-曲面模型高效匹配的新方法，突破传统方法受磨抛加工余量不均匀（问题1）所引起的颤振、加工波纹、过/欠磨等问题；建立基于加工余量分布的叶片边缘材料去除率优化模型，通过合理规划磨抛路径并有效控制工件姿态，提出力位精密控制方法，解决磨抛接触力难以控制（问题2）从而造成叶片边缘加工变形、局部烧蚀等问题；搭建全闭环控制机器人磨抛系统平台，完成不同型号汽轮机叶片、航空叶片边缘磨抛工艺试验。通过以上内容研究，形成叶片边缘机器人磨抛“在线测量-余量优化-质量控制”的理论方法、关键技术和工艺方案，应用于企业批量生产。

机器人砂带磨抛加工叶片进排气边缘主要面临加工余量不均匀和接触力难以控制难题，从而限制叶片机器人磨抛技术的应用推广。本项目从叶片前后缘机器人磨抛在线测量、加工余量优化与控制、磨抛路径优化与工件姿态控制、磨抛加工表面完整性控制等四个方面开展研究工作。提出了基于重定位的叶片机器人磨抛系统手眼标定方法，标定算法拟合误差仅为0.068mm，较现有主流标定方法分别降低47.7%和38%，解决了目前手眼标定方法中多次引入机器人定位误差这一突出问题；建立了基于余量分布的叶片边缘材料去除率模型，模型精度较传统去除率模型最高提升33.6%，并结合工艺参数和加工方式优化策略，解决了叶片切入端和切出端的欠磨和过磨问题；提出了一种基于材料去除廓形模型的机器人砂带磨抛加工自适应轨迹规划算法，加工时间较现有的轨迹规划算法降低68%，被认为是在保证加工精度和质量前提下用以提升叶片加工效率的有效方法；提出了一种基于PI/PD主动力/位混合控制和PID被动力控制方法，结合基于Kalman滤波的主被动力控制信息融合方法，力控制误差小于3N，平均偏差缩减至0.16N，实现了叶片法向磨抛力的高精度控制；叶片机器人砂带磨抛加工试验结果表明叶片的平均轮廓误差仅为0.0194mm，前后缘的平均轮廓误差分别为0.0319mm和0.0342mm，均小于叶片所允许的误差0.08mm，叶片的平均表面粗糙度Ra值小于0.3μm，满足叶片表面粗糙度Ra<0.4μm的加工质量要求。通过以上内容研究，解决了现有加工中的两大难题，形成了叶片边缘机器人磨抛“在线测量-余量优化-质量控制”的理论方法、关键技术和工艺方案，为各类中小型叶片边缘的精密磨抛加工提供了全新的解决方案。