Model predictive force control for multi-axis rough milling

力是铣削过程中最重要的工艺变量，因为它决定了生产率（通过进给速度）、产品质量（通过刀具位移）和工艺安全性（关于刀具破损）。模型预测控制（MPC）使用显式过程和机器模型来确定短时间范围内的未来机器行为，并相应地控制过程。它能够在工艺的技术极限下实现安全、无超调、最佳控制。这样的系统已被开发为双轴铣削过程的原型。在这个项目中，一个多轴铣削控制系统将被开发和系统地检查。为此目的，工作台测力计的测量信号必须在过程期间进行校正，例如其惯性和工件质量的变化。这引入了额外的不确定性，应通过过程模型的连续校准（“识别”）来考虑这些不确定性。由于MPC使用模型系数作为反馈回路，这使得能够进行鲁棒控制。MPC控制沿着刀具路径的进给，但机床的行为沿此路径沿着变化。这是因为不同的机床轴参与运动-特别是在多轴铣削中。在控制中也必须考虑这种非线性行为。本课题的目的是开发和研究一种多轴粗加工力闭环控制系统。假设控制器在力的任何参考下操作多轴铣削过程而不超过它-与工具的条件无关。该系统是基准的控制方法，这是已经建立在切割技术的研究。

Force is the most important process variable in the milling process, because it determines productivity (via the feed rate), product quality (via the displacement of the tool) and process safety (with regard to tool breakage). A model predictive control (MPC) uses an explicit process and machine model to determine the future machine behavior for a short time horizon and controls the process accordingly. It enables for a safe, overshoot-free, optimal control at the technological limit of the process. Such a system has been developed as a prototype for the biaxial milling process. In this project, a control system for multi-axis milling is to be developed and systematically examined. For this purpose, the measurement signal of a table dynamometer must be corrected during the process, e.g. of its inertia and of the change in the mass of the workpiece. This introduces additional uncertainties, which should be considered through a continuous calibration ("identification") of the process model. Since the MPC uses the model coefficients as the feedback-loop, this enables for a robust control. The MPC controls the feed along the tool path, but the behavior of the machines varies along this path. This is because different machine axes are involved for a movement - especially in multi-axis milling. This nonlinear behavior must also be taken into account in the control. The aim of the project is to develop and research a closed-loop force control system for multi-axis roughing. It is assumed that the controller is operates a multi-axis milling process at any reference of the force without exceeding it - independent of the condition of the tool. The system is benchmarked to a control method, which is already established in the research of cutting technology.