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In this paper, a radial and axial integrated auxiliary bearing (RAIAB) device which can eliminate all radial and axial protective clearances after the rotor dropping is proposed to improve the reliability of the active magnetic bearing systems. In the proposed RAIAB, a strategy that the rotor end and the inner bushing are machined into conical surface is adopted so that the radial and axial clearances between the rotor and the inner bushing can be eliminated simultaneously when the inner bushing moves along the axial direction. In order to research the influence of the conical degree of the inner bushing on the performance of the RAIAB, the preliminary prototype experimental rig is developed and the cases of a 5 degree of freedom AMB rotor dropping on RAIABs at maximum speed of 30000 rpm are tested. The experimental results show that the RAIAB installed with a 30-conical degree inner bushing can successfully eliminate all protective clearances after the AMB rotor drops. However, the RAIAB installed with a 45-conical degree inner bushing is not able to eliminate clearance when the dropping speed of the rotor exceeds 18000 rpm.

This paper focuses on the vector control scheme of surface-mounted permanent magnet synchronous motorized spindle, to solve the problem of poor speed regulation performance of spindle under high-speed operation conditions, according to the principle of double closed-loop vector control, the characteristics of speed loop and current loop are analyzed, and fuzzy theory is introduced to optimize the traditional speed loop PI controller, furthermore the system parameters are adjusted in real time. Aiming at improving the dynamic response ability of the control system, a first-order linear active disturbance rejection controller is proposed to replace the traditional current loop PI controller, which enhances the anti-interference ability of the system. Experimental results show that the fuzzy PI-LADRC combined control strategy can effectively reduce stator current ripple and torque ripple, and improve the dynamic response speed and anti-interference ability of the system. At last can also improve the output performance of the motorized spindle.

Squeeze-film dampers (SFD) are used as indispensable bearings in many rotating machines to suppress lateral vibration and enhance stability. The kinetic energy of the damping fluid is sometimes greater than that of SFD’s journal. Therefore, the influence of the damping fluid must be considered in establishing a dynamic model of a rotor–bearing system. A concept that involves the added mass of the damping fluid is proposed in this work, and the calculation formula is derived based on laminar flow theory and the mean-square speed of the fluid. The unbalance responses of a rotor–bearing system are solved by numerical iteration and with the transfer matrix method. The results calculated with and without added mass are compared. Experimental results indicate that introducing the added mass of the damping fluid into a dynamic model is effective.