磁悬浮铣削电主轴转子-刀具变质量不平衡系统动态特性研究

Study on Dynamic Characteristics of Magnetic Suspension Milling Motorized Spindle Rotor-tool Variable Mass Unbalance System

针对磁悬浮铣削电主轴在切削过程中因切屑进入刀具容屑槽中而导致“刀具-主轴”系统质量变化,进而引起系统回转精度不稳定的问题,以变质量质点理论为依据建立“切屑-刀具-主轴”系统的变质量动力学模型。分析系统的不平衡质量变化时所引起的系统振动,进而导致磁悬浮轴承定/转子间气隙磁场不均所产生不平衡磁拉力,并利用等效磁路法建立不平衡磁拉力模型。利用Riccati传递矩阵法求解磁悬浮铣削电主轴转子-刀具系统的稳态动力学模型,得到系统的模态参数和初始偏心质量影响下的不平衡响应。考虑铣削力、变质量力、切屑质量不平衡离心力和不平衡磁拉力等因素,采用Newmark-β算法求解磁悬浮铣削电主轴转子-刀具变质量系统的瞬态动力学模型。对系统从起动到切削过程的动态响应进行仿真分析,结果表明,质量不平衡是影响磁悬浮铣削电主轴转子-刀具系统稳态响应的主要因素;在切削过程中,变质量力是影响系统瞬态响应的主要因素;不平衡磁拉力对系统响应的影响与系统的稳定性成负相关与系统的振幅成正相关。

Aiming at the rotation accuracy instability problem of "tool-the main shaft" system caused by the mass change of "tool-spindle" system caused by the chip entering into the chip tolerance slot during the cutting process of magnetic suspension milling motorized spindle, a dynamic model of "chip-tool-spindle" system was established based on variable mass point theory. The vibration of the system caused by the change of the unbalance mass was analyzed, and the unbalance magnetic force was generated due to the uneven magnetic field in the air gap between the stator and rotor of the magnetic suspension bearing. A model of the unbalance magnetic force was established by using the equivalent magnetic circuit method. The Riccati transfer matrix method was used to solve the steady-state dynamic model of rotor-tool system in magnetic suspension milling motorized spindle, and the unbalance response of the system under the influence of the modal parameters and the initial eccentric mass was obtained. The milling force, the variable mass force, the chip mass unbalanced centrifugal force and the unbalanced magnetic pull force were considered,and the Newmark-β algorithm was used to solve the transient dynamic model of the rotor-tool variable mass system. The dynamic response of the system from starting to cutting process is simulated and analyzed. The results show that, mass unbalance is the main factor affecting the steady state response of rotor-tool system of magnetic suspension milling motorized spindle;variable mass force is the main factor affecting the transient response of the system;the effect of unbalanced magnetic pull on system response is negatively correlated with system stability and positively correlated with system amplitude.