Design, modeling, and performance testing of a weak coupling combined radial-axial magnetic bearing

Most combined radial-axial magnetic bearing (CRAMB) is usually composed of a radial magnetic bearing (RMB) unit and an axial magnetic bearing (AMB) unit. The coupling problems in different degrees of freedom (DOF) will make it difficult to design the controller and influence dynamic characteristics of the magnetic bearing system (MBS). In this paper, the coupling stiffness models of a CRAMB between the RMB unit and the AMB unit affected by radial-displacement and axial-displacement are presented using equivalent magnetic circuit method. The CRAMB and the testing system are designed and fabricated. The coupling stiffness model is verified by the experimental results. The weak coupling characteristics between the radial-direction and axial-direction is beneficial to design the controller and dynamic stability control for the CRAMB system.