Abstract: To investigate the stable levitation performance of permanent magnetic bearings system, the stable levitation performance of the five-DOF permanent magnetic bearing (PMB) system is analyzed from the perspective of bearing stiffness. The analysis formulas of PMB’ s loading capacity, torque and stiffness are established based on the equivalent magnetic charge theory, then use Monte Carlo method to solve the quadruple integral formula to get the result of the force, moment and stiffness. The minimum critical speed for rotor in the case of forced precession and in the situation of external torque is explored. Puts forward a six circular magnetic rings and five DOF all permanent magnetic bearing structure model based on the structure of radial and axial magnetic bearings, the carrying capacity, moment and stiffness of five-DOF PMB system are analyzed, this shows that the model can withstand stably axial load and cannot bear radial load under the static, this is consistent with the Earnshaw-theorem. Finally, using the levitation performance of rigid rotor gyro inertial torque to withstand the imbalance torque of the all permanent magnetic bearing system and external torque. Thereby maintaining the stable fixed-axis rotation. The calculation results of stable levitation performance for the system shows that the rotor in all permanent magnetic bearing can be dynamic stable suspension after its speed over the minimum critical speed and has a certain value for engineering application.

Key words: all permanent magnetic bearing, critical speed, gyroscopic moment, stable levitation performance, stiffness