压电驱动器可控预紧力主轴设计及性能分析

Design and performance analysis of variable preload spindle based on piezoelectric actuator

可控预紧力主轴能够满足高速主轴在整个切削转速范围内热、动特性兼优的要求,已逐步成为智能主轴的重要发展方向。为弥补压电驱动器(piezoelectric actuator,PEA)可控预紧力主轴设计及选型方面的不足,提出一种具有分辨率高、响应快、对切削刚度影响小及结构紧凑等优点的PEA可控预紧力主轴结构。建立了静止状态和运行状态下的角接触球轴承刚度模型,并以此为基础建立了PEA可控预紧力主轴的等效力学模型,得到了预紧机构负载刚度随预紧位移的变化规律。然后,分析了PEA的输出特性,建立了预紧机构的实际输入输出模型,并通过该模型分析了初始预紧力和PEA刚度对预紧力控制区间的影响规律,进而提出了预紧机构设计选型原则。最后,应用提出的主轴结构和预紧机构设计选型原则设计了PEA可控预紧力主轴试验台。试验结果表明预紧力控制分辨率为1.5 N,阶跃响应时间为300 ms,验证了所建预紧机构实际输入输出模型的准确性;温度控制试验结果表明该主轴试验台具有良好的温度调控能力。研究结果可为实际工程中PEA可控预紧力主轴的设计提供指导。

Variable preload spindle can meet the requirements of both thermal and dynamic characteristics of high-speed spindle in the whole cutting speed range, and has become an important development direction of the intelligent spindle. In order to make up for the deficiencies in the design and selection of variable preload spindle based on piezoelectric actuator(PEA), a variable preload spindle structure based on PEA with the advantages of high resolution, quick response,little influence on cutting stiffness and compact structure was presented. The stiffness models of angular contact ball bearing under static and running conditions were established. On this basis, the equivalent mechanical model of the variable preload spindle based on PEA was established and the change regulation of preload mechanism load stiffness with preload displacement was obtained. Furthermore, the actual inputoutput model of the preload mechanism was established by analyzing the output characteristics of PEA,and the influence of initial preload and the stiffness of PEA on the control range for preload was analyzed, and then, the design and selection principles of preload mechanism was proposed. Finally,a variable preload spindle test rig based on PEA was designed by applying the proposed spindle structure and the design and selection principles. Test results showed that the preload control resolution was 1.5 N and the step response time was 300 ms,and the accuracy of the actual input-output model of the preload mechanism was verified. The temperature control test results showed that the spindle test rig had great temperature control ability. The study results can provide guidance for the design of variable preload spindle based on PEA in engineering.