Fast steering mirrors (FSMs) are used to correct images observed by satellites. FSMs need to have large apertures and realize high precision and the positioning of the mirror in the tip-tilt and axial directions needs to be highly precise and highly responsive in order to capture large-scale, high-resolution images. An FSM with a large-diameter mirror supported by a compact magnetic suspension and driven by long-stroke voice coil motors (VCMs) is proposed in this paper. The magnetic suspension and VCM actuators enable the mirror to be highly responsive and to have long-range movement in the tip-tilt and axial directions without friction and wear. The magnetic suspension is a hybrid that has active control in the lateral directions and passive support in the tip-tilt and axial directions. An experimental FSM with an 80 mm diameter dummy mirror was fabricated and tested. The mirror’s driving ranges in the tip-tilt and axial directions were ±20 mrad and ±500 μm, respectively. Furthermore, the servo bandwidths in the tip-tilt and axial directions were more than 1 kHz and 200 Hz, respectively.

As the rotational speed of conventional rotor systems supported by oil-film bearings has increased, vibration problems such as oil whip and oil whirl have become apparent. Our group proposed the use of active magnetic bearings (AMBs)/bearingless motors (BELMs) to stabilize these systems. In such a system, measuring the variable stiffness and damping of the oil-film bearings, the current-force and displacement-force parameters of the AMBs/BELMs, and the residual unbalanced force is necessary to satisfy the stability of the rotor system. These parameters are the foundation for the rotor dynamics analysis and optimization of the control strategy. In this paper, we propose a method to simultaneously identify the parameters of the oil-film bearings and AMBs/BELMs along with the residual unbalanced forces during the unbalanced vibration of the rotor. The proposed method requires independent rotor responses and control currents to form a regression equation to estimate all the unknown parameters. Independent rotor responses are realized by changing the PID control parameters of the AMBs/BELMs. Numerical simulation results show that the proposed method is highly accurate and has good robustness to measurement noise. The experimental results show that the unknown parameters identified by the responses generated by different controller parameters are similar. To confirm that the identification results are correct, verification experiments were carried out. The vibration amplitude of the rotor was successfully suppressed by applying a force to the rotor in the opposite direction to the residual unbalanced force. The frequency response characteristics and unbalanced responses of the rotor estimated by the values of the parameters identified show good consistency with the measured results.

The high biocompatibility and high durability of disposable extracorporeal centrifugal blood pumps (CBPs) utilizing magnetic bearing or bearingless motor technology make them perfect for supporting cardiopulmonary circulation for patients. However, the rotor incorporated in the disposable unit typically uses high-cost and environmentally-unfriendly rare-earth permanent magnets (PMs), leading to economic and environmental issues. This paper proposes a centrifugal blood pump with a PM-free impeller/rotor in the disposable pump head utilizing a 12/8 bearingless switched reluctance slice motor (BELSRM). Two axial-magnetized PM rings and two iron rings are mounted symmetrically above and below the tips of the stator poles. The biased magnetic flux generated by the PM rings forms a closed vertical magnetic circuit (homopolar flux circuit) with a PM-free rotor, providing high passive stiffness and large positioning forces independent of the rotor angle. A three-dimensional (3D) finite element analysis (FEA) model was used to evaluate the rotor support stiffness, the current-force coefficient, and the rotational torque. A prototype bearingless slice motor (BELSM) and a disposable pump head with a diameter of 50 mm PM-free impeller/rotor were fabricated. The radial magnetic levitation and the rotation were actively controlled by displacement and speed feedback control systems, respectively. A mock circulatory loop filled with 40wt% aqueous glycerol solution was set to evaluate the performance of the proposed CBP. The CBP provided a maximum flow rate of 4.59 L/min and a maximum head pressure of 214.5 mmHg at 2300 rpm and 2400 rpm, respectively.

Rotors of large turbomachinery are usually supported by oil-film bearings, because oil-film bearings have a simple structure, high load capacity, and large damping. However, an oil-film bearing induces self-excited vibration at high rotational speeds. Therefore, a suppression method for the self-excited vibration is needed. This study proposes the application of a bearingless motor (BELM) for a rotor supported by oil-film bearings. To realize the proposed rotor system, an experimental rotor, supported by the oil-film bearings and equipped with a BELM, was designed and fabricated. This study illustrates the winding configuration and the controller design of the BELM for a stable suspension system. The test rotor with the oil-film bearings and the BELM exhibited stable rotation at rotational speeds higher than the onset speed of the self-excited vibration. Furthermore, the radial force required to suppress the self-excited vibration is discussed. Because it is desirable for the radial force of the BELM to be small in the actual machine, we realized a stable and high-speed rotation with a small radial force. Thus, we demonstrate the feasibility of a compact, stable, and high-speed rotor-oil-film bearing system.