Design and Optimization of a Radial Hybrid Magnetic Bearing With Separate Poles for Magnetically Suspended Inertially Stabilized Platform

To decrease the mass of the radial hybrid magnetic bearing (RHMB) when used in large journal diameter application, this paper researches the relationships of the structure parameters and presents an optimization method for an RHMB with separate poles. The designed RHMB is composed of four separate magnetic poles, with a secondary air gap constructed to help the control flux form its loop. Considering the effect of the secondary air gap to the value of both bias flux and control flux, the reluctance of the secondary air gap is optimized based on the magnetic circuit analysis, and the optimum value turns out to be determined by the reluctances of permanent magnet and the air gap only. The optimization of the whole RHMB is conducted with four constraints considered: the maximum force, copper loss, flux density of the air gap, and flux density of the secondary air gap. After a series of analyses, it is found that the copper loss of the RHMB depends mainly on the geometric size of the magnetic pole, and has no relationship with the number of coil turns or the current of the control coil. By the optimization method of sequential quadratic programming, the structure parameters have been obtained. Then the finite element method is adopted to simulate the distribution of the flux density, and the result is in accordance with that of the magnetic circuit analysis. The prototype is manufactured based on the optimal design, and the experiment carried out on the current stiffness and displacement stiffness verified the design result of the optimization.