基于主动磁轴承的机床切削系统动态特性分析

Dynamic Characteristics Analysis of Dynamic Cutting Based on Active Magnetic Bearings

数控机床在切削过程中其电主轴转子系统的动态特性及刀具端的动态特性不仅决定着工件的表面质量,还决定着数控机床的高速化发展.磁悬浮电主轴是目前高速机床的首选,而基于磁悬浮轴承的电主轴转子系统运行时的动态特性将受到磁轴承等效刚度和阻尼的极大影响.除此之外,切削力系数和切削阻尼也将影响电主轴转子系统及刀具端的动态特性.以主动磁轴承支承的柔性电主轴为研究对象,研究了主动磁轴承等效刚度、阻尼及切削力系数对电主轴转子系统模态及临界转速的影响;分析了主动磁轴承等效刚度、等效阻尼及切削阻尼对刀具端频率响应以及对切削稳定性的影响.研究结果表明,主动磁轴承的等效刚度对电主轴转子的模态频率影响较大;而随着主动磁轴承等效刚度的增大,将增大刀具端频率响应的最大负实部及虚部的位置、最大负实部及虚部的值;而主动磁轴承等效阻尼和切削阻尼仅影响刀具端的频率响应最大负实部及虚部的值的大小,而不影响其发生的位置,且切削阻尼的影响较大;刀具端的频率响应同样也反映了切削的稳定性,这在随后的稳定性分析中得到了验证.对刀具端的动态分析将为切削过程中的振动控制提供一定的基础.

The dynamic characteristics of the spindle rotor system and cutter in the cutting process not onlydetermine the surface quality of work pieces, but decide the high speed development of mechanical process-ing as well. The magnetic levitation motorized spindle is the first choice for high speed machine tools at pres-ent, and the equivalent stiffness and damping of magnetic levitation bearings will greatly affect the dynamiccharacteristics of the spindle rotor system and cutter. In addition, the cutting stiffness and damping willaffect the dynamic characteristics of the spindle rotor system and cutter. Taking the flexible motorized spindleby active magnetic bearing as the research object, the paper investigates the effect of the equivalent stiffnessand the stiffness of cutting process of active magnetic bearings on the electric spindle rotor system modal aswell as the impact of the equivalent stiffness and damping of the active magnetic bearings and the stiffnessand damping of cutting on cutter frequency response. Results show that the equivalent stiffness of active mag-netic bearings has a greater effect on the modal frequencies of the motorized spindle rotor, whereas the cut-ting stiffness has a smaller effect. Concerning the cutter frequency response, the results show that with theincrease of equivalent stiffness and cutting stiffness of the active magnetic bearings, both will increase thecutter frequency response location and the maximum negative value of negative real part and imaginary part,but the effect of cutting stiffness on cutter frequency response is the greater. The frequency response of cutteralso reflects the stability of the cutting, which is verified in the subsequent stability analysis. The dynamic a-nalysis of the cutter will provide a basis for vibration control in the cutting process.