Design and fabrication of a micro magnetic bearing

A micro magnetic bearing actuator has been designed using electromagnets. In this design, the rotor position is actively controlled in the radial directions and passively supported in the axial direction. A micro position sensor, along with a proportional plus derivative (PD) control system, constitutes the feedback network, which ensures that the rotor is actively suspended in the radial directions. The circular stator has four control coils which are sandwiched between two stator end plates. The diameter of the stator and rotor are 2.1 and 2.6 mm respectively, while the thickness is fixed at 250 mu m. The air gap between the stator and rotor has been fixed at 10 mu m. The stator and rotor plates were fabricated using Permalloy electroplating, while the control coils of the stator were hand-wound using conventional coil winding techniques. The bearing components were assembled using normal micro assembly techniques. The details of the fabrication and assembly techniques employed for the micro bearings are presented, along with the test results.