Relative and absolute hybrid motion control strategy investigation on active magnetic bearings_analysis of system performances

In order to raise or guarantee the precision and dynamic stiffness of AMB spindle units mounted on the complex structures, a new method called relative and absolute hybrid motion control is advanced. The model of multi-degree of freedom (MDOF) system was built and analyzed, the natural frequency and modal shapes were calculated. The hybrid control system of the base structure-AMB-rotor system was designed. The mode control was selected as the control law. The actual control force could be resolved after the displacement gain and the speed gain was determined. It could be seen from the equation expression that the control force was not only related to the displacement and speed of the rotor, but also related to those of the stator. The response analysis results showed that the rotor had quick response, low overshoot and high precision compared to the relative motion control system. The hybrid control system could effectively suppress the base vibration and improve the rotor precision. So, hybrid control system had good quality. And it could obtain different displacement gain and the speed gain so as to satisfy the various needs of the system. Thus the system was adjustable.