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A magnetic screw motor integrated by a magnetic screw and a permanent magnet synchronous motor offers high thrust density without friction and loss. However, its internal structure is complicated, resulting in difficulty to control its linear displacement to track the given signal in time and even getting out of control due to interference. In this article, to improve the tracking performance and anti-interference performance of the system, an active disturbance rejection controller (ADRC) is adopted to improve the current loop and makes up for nonlinear regional control in the closed-loop control system. To ensure the stability of the proposed scheme in the entire operation range, the design and the stability analysis are carried out in the continuous-time domain. The novel control algorithm enhances the flexibility of the magnetic screw motor by optimizing the nonlinear function in ADRC. In addition, to highlight the high-performance control of the ADRC for the magnetic screw motor, sliding mode control and PI control are added to compare with it. Finally, the reciprocating motion control is added to show the diversity of the functions of the magnetic screw motor, which verifies the effectiveness and feasibility of the control algorithm. [ABSTRACT FROM AUTHOR]

This article proposes a practical design guide for a linear electromagnetic actuator based on the concept of magnetic screw transmission, in which manufacturing and assembly technologies are investigated. The surface-inserted design is first used to form a required helical-shape magnetic pole, which exhibits simple processing, high precision, and robust structure. Moreover, different topologies are developed using the 3-D finite-element analysis aided design, with the goal of optimizing thrust force. In addition, different number of permanent-magnet (PM) segments are first proposed to reduce the cogging effect. Afterward, the linear actuator integrates the rotary machine and the magnetic screw together to construct a compact design and decouples the magnetic circuits. The decoupling design focuses on the self-shielding effect of the Halbach PM array, and the special bearing supports are selected to avoid the eccentricity. Finally, a prototype is built using the developed techniques. Experiments are carried out on a linear test bench, verifying the theoretical analysis. [ABSTRACT FROM AUTHOR]

This paper proposes a novel tubular double-stator vernier permanent-magnet (TDS-VPM) motor for artificial hearts. The key of the proposed motor is double-stator and vernier structures. Due to its vernier structure, more PMs can be adopted in the proposed TDS-VPM motor and the useful harmonics of the air-gap flux density are increased, thus improving thrust density. Furthermore, double stator, namely inner stator and outer stator, has an appropriate 90° (electrical degree) angle difference. Since the inner stator is located inside the mover, the motor space is fully used. Hence, the thrust density is enhanced and the axial direction length is reduced. Meanwhile, the angle difference between the inner and the outer stator can reduce the cogging force of this TDS-VPM motor. The electromagnetic characteristics of the proposed motor are analyzed using the time-stepping finite-element method, confirming the validity of the theoretical analysis. [ABSTRACT FROM PUBLISHER]

This paper proposes a new type of motor with hybrid permanent magnet material (HPMM); termed HPMM motor. The key of the proposed HPMM motor is the excitations, which combined rare-earth PM (REPM) with ferrite PM (FPM). To investigate the HPMM motor extensively, the HPMM motors with parallel magnetic circuit (PMC) and serial magnetic circuit (SMC) are designed. Because of the property difference between the REPM and the FPM, both PMC-HPMM motor and SMC-HPMM motor can offer low total harmonic distortion at high winding factor. Besides, the PMC-HPMM motor needs low consumption of REPM and offers low cogging torque, while the SMC-HPMM motor needs the extraordinary consumption of FPM, but offers little lower cogging torque. In addition, the reliabilities of both PMC-HPMM motor and SMC-HPMM motor are improved because of the single-layer concentrated winding and fault-tolerant teeth. Finally, the demagnetization of two motors has been studied, which indicates that the partial demagnetization will occur in the FPM. All these theoretical analyses are evaluated by the time-stepping finite element method. [ABSTRACT FROM AUTHOR]

The aim of this paper is to design and investigate two fault-tolerant interior-permanent-magnet motors for high reliability operation. The first one is the spoke type, while the second one has V-shape magnets embedded in the rotor. The structures and features of both motors are presented and the optimal designs are performed. The electromagnetic performances, such as $dq$-axis inductances, torque, flux weakening, and partial demagnetization, are investigated and compared. In order to calculate the $dq$-axis inductances accurately and segregate the torque components, the frozen-permeability method is adopted. Additionally, a method to obtain the maximum flux-weakening speed is introduced. Moreover, the partial demagnetization performances of both motors are evaluated under no-load, on-load, overload, and short-circuit conditions. Also, the fault-tolerant capacities of both motors are compared. Finally, both motors are built for exemplification. The analysis is confirmed by experimental results. [ABSTRACT FROM PUBLISHER]