薄壁件镜像加工的稳定性预测及基于主动支撑的振动控制研究

Mirror milling is a new technology for high performance milling process of large-scale thin-walled workpiece. Multidisciplinary research on the key scientific problem of this project, i.e., dynamic deflection reduction and vibration suppression during the milling process of large-scale thin-walled workpiece, is conducted through theoretical analysis, numerical simulation and experimental investigation. The main research contents are of the following 3 aspects: (1) dynamic modeling and stability analysis of mirror milling process, (2) chatter monitoring of mirror milling process using time-frequency analysis technology, and (3) adaptive control of support head for suppression of machining caused deformation and vibration. The dynamic model is to be set up based on the theory of flexible multibody system dynamics. A full discretization method will be used for prediction of milling stability and machining error. A chatter identification method based on online time-frequency analysis of accelerometer signals is to be presented. A support head with variable stiffness and variable damping is to be designed. Machining dynamics guided milling parameter optimization method and active control of the support head are to be developed for the purpose of machining deformation reduction. The achievements of this project will enrich the research contents of machining dynamics and provide theoretical and technical support for the dynamic deflection reduction and vibration suppression during the milling process of large-scale thin-walled workpiece.

镜像铣削是解决大型薄壁件高效精密加工的新一代技术。本项目围绕“薄壁件镜像加工中的振动抑制”这一核心科学问题，拟采用理论分析、数值计算和实验验证相结合的研究思路，从(1)铣削动力学建模与稳定性分析、(2)颤振的监测及(3)主动支撑头的自适应控制等三个方面开展深入研究,在柔性多体动力学框架下建立“刀具-工件-支撑”的动力学模型，探索铣削过程的动力学本质，提出考虑支撑情况下镜像铣削加工过程稳定性分析和动态加工误差预测方法，建立基于时频分析的铣削颤振监测方法，实现基于主动变阻尼、变刚度支撑的振动抑制。重点突破如下基础理论和关键技术：(1)基于柔性多体动力学的“刀具-工件-支撑”工艺系统建模方法；(2) 基于主动支撑的变阻尼、变刚度振动抑制方法。研究成果将充实和发展大型薄壁件加工的基础理论，为解决该类零件加工的振动和变形难题提供新的思路和技术方案。

针对薄壁件镜像加工中的工件刚度较低，容易发生颤振，项目在薄壁件铣削动力学建模及稳定性分析、薄壁件铣削颤振早期预报、薄壁件铣削颤振主动控制等方面进行了深入研究，具体包括以下四个部分：.(1) 针对薄壁件铣削失稳动力学问题，建立了薄壁件铣削动力学模型，发展了基于半离散法与精细积分法的薄壁件铣削稳定性分析方法，并探究了薄壁件铣削颤振失稳的不同路径。.(2) 针对薄壁件铣削颤振的早期预报问题，提出了兼具高分辨率时频分析与高精度信号分解功能的迭代非线性调频分量分解（INCMD）算法，并利用该方法建立了基于波内调制特征提取的薄壁件铣削颤振早期预报流程。.(3) 针对薄壁件铣削颤振的主动控制问题，设计并建模了针对低刚度薄壁工件的主动支撑系统，引入了考虑受控系统时滞特性的时滞状态反馈控制器，并利用了微分求积法在参数空间中快速搜索控制器的最优增益。仿真与实验结果表明，与其他同类型控制策略相比，最优时滞状态反馈控制器将有助于最大限度地扩大薄壁件铣削系统的稳定域、且将大幅降低作动器的能耗。.(4) 针对薄壁件铣削颤振早期预报算法与主动控制策略的综合设计问题，基于LabVIEW平台开发了软件系统，把早期预报与主动控制两大模块融合在了一起。在机床执行薄壁件铣削加工任务的过程中，当且仅当实时计算的颤振指标值超出警报阈值时，控制器才会自动开启。实验结果表明，基于该系统，薄壁件铣削颤振在孕育阶段即可得到消除，而真正的稳定铣削过程不会受到干扰，且作动系统的能耗可降到最低。此外，实验结果验证了在控制系统仿真中得到的所有结论。