Active Control of Tool Deflection and Chatter During Precision Milling Operations Using Magnetic Bearing Spindles

这笔赠款将用于确定使用小直径立铣刀进行精密加工应用的准静态和动态误差补偿的可行性。这些主动控制方案的原动机将是一种商用的磁悬浮主轴，转速为70,000 rpm。这种主轴能够产生微型铣刀所需的高表面速度，可以调整旋转中心以补偿刀具偏转，并具有提供主动抖动补偿所需的高带宽。控制策略将有两种模式：刀具偏转的低频路径修正和颤振的高频补偿。用于定位磁力轴承主轴的控制器需要进行重大修改才能实现上述算法。与该主轴配套的控制器可以感应转子的位移，并控制电磁铁电流，使主轴绕惯性中心旋转。该项目将增加一块高速处理板来实现所提出的控制策略，即估计动态刀具偏转的大小和方向，并修改主轴转子设置点以补偿这些静态和动态偏转。如果成功，该项目中展示的技术将提高加工塑料光学和机械零件注射模具等精密表面的能力。但这些结果将有更广泛的应用，包括广义刀具偏转补偿的科学基础，主动减少颤振对表面光洁度的影响，以及磁轴承的高带宽控制。此外，还将开发实时频率分析技术来分析位移信号，并提取高频分量用于颤振检测和校正。预计这些结果将立即应用于高精度和全尺寸的高速铣削应用。

This grant will be used to determine the feasibility of quasi-static and dynamic error compensation for precision machining applications using small diameter end mills. The prime mover for these active control schemes will be a commercially-available, magnetically-suspended, 70,000 rpm spindle. Such a spindle is capable of creating the high surface speeds needed for miniature milling tools, can adjust the center of rotation to compensate for tool deflection, and has the high bandwidth necessary to provide active chatter compensation. The control strategies will have two modes: low-frequency path correction for tool deflection and high-frequency compensation for chatter. The controller used to position the magnetic bearing spindle will require major modifications to implement the algorithms described above. The controller supplied with this spindle senses the rotor displacements and manipulates electromagnet currents to keep the spindle rotating around the inertial center. A high-speed processing board will be added to implement the proposed control strategy of estimating the magnitude and direction of dynamic tool deflections and modifying the spindle rotor setpoint to compensate for these static and dynamic deflections.If successful, the techniques demonstrated in this project will improve the capability to machine precision surfaces such as injection molds dies for plastic optical and mechanical parts. But the results will have much broader applications including a scientific basis for generalized tool deflection compensation, actively reducing the effects of chatter on surface finish, and high-bandwidth control of magnetic bearings. In addition, real-time frequency analysis techniques will be developed to analyze the displacement signals and extract high-frequency components for chatter detection and correction. It is anticipated that these results will have immediate application to both high-precision and full-scale, high-speed milling applications.