Research On Vibration Control Of High Speed Motor Spindle

High speed motor spindle is the key functional component of high precision CNC machine tool, in which the main spindle motor is mounted to the spindle and become a complete built-in spindle unit. Therefore it has been paid more attention for its compact configuration, light mass, little inertia, small vibration, low noise, fast response and other advantages, and also for its wide application such as aeronautics and astronautics, automobile, mold manufacture and other manufacture fields. With the development trend towards high torque at low speed and high power at high speed, preload control is a brand-new direction with good technology future. It is of importance to obtain optimum preload and ensure the dynamic quality in whole work condition including high torque at low speed and high power at high speed, which is the foundation of preload control. As a result of this, vibration control of high speed motor spindle based on optimum preload is presented in this paper.Firstly, motor spindle is designed on the basis of preload control. And whole transfer matrix method and rolling bearing theory is used to establish the dynamic model of rotor-bearing system and analyze the critical rotation speed and main mode. Furthermore, spindle stiffness is calculated with considering bearing damp effect, and optimum preload is given under some criterions in whole work condition.Secondly, preload control system for motor spindle is designed based on microcontroller including controller, power amplifier and so on. And it has been debugged, which lays the foundation for realization of optimum preload for motor spindle.Finally, robust control for motor spindle with active magnetic bearing (AMB) is studied in the paper. The dynamic equations of the five-degree-of–freedom motor spindle with AMB are built, and digital control system for motor spindle with AMB is presented based on DSP. On the basis of analyzing racial AMB system with system modeling uncertainty, aμrobust controller is designed by introducing fictive uncertainty. The simulative waveforms of control system are given under different instances by using Matlab. The results of simulation show that the AMB robust control based onμsynthesis theory has strong robustness to system model uncertainty and the external disturbances can be controlled effectively.