Structure and coupling analysis of a novel 3-DOF conical magnetic bearing

This paper deals with the novel structure and coupling analysis of a 3-degrees of freedom (3-DOF) conical magnetic bearing. The conical stators of the bearing are designed symmetrical to provide the axial control exclusively, and the radial stators are separated by nonmagnetic material between X and Y channels, so the magnetic flux path can be separated among different channels. The configuration and working principle of the bearing are provided, and the mathematical model is derived based on the bias and control magnetic circuits. In order to evaluate the degree of force coupling between different channels, the concept of coupling factor is proposed, which is defined as the ratio of force variation caused by coupling to the original force when there is no coupling. The coupling factors are analyzed not only among the translational movement of X, Y and Z channels but also between the translational and rotational degrees of freedom. The calculation results show that although the component coupling factors of each magnetic poles are a little larger, the resultant ones in X, Y and Z directions of the designed bearing are all less than 4%. Therefore, the magnetic forces and torques of different channels are weakly coupled, and it is convenient for the control of the magnetic bearing.