Sliding mode observer (SMO) has attracted extensive attention in the field of medium- and high-speed sensorless control of permanent magnet synchronous (PMSM) because of its strong robustness and stability. However, the traditional methods are vulnerable to dc bias caused by measurement errors and parameter changes. Therefore, an improved SMO algorithm by disturbance observer compensation is proposed in this article. The algorithm unifies the mathematical models of surface PMSM and interior PMSM. Besides, a band-pass filter (BPF) is used to replace the traditional low-pass filter, so it can effectively suppress dc bias and high-frequency noise. In addition, at any BPF center frequency, the proposed disturbance observer with LPF characteristics can perfectly compensate the position error caused by the digital filter in real time. Moreover, through sensitivity analysis, the influence of model uncertainty on the observation position is studied, and an adaptive extended state observer is added to mitigate the influence of parameter mismatch on the performance, and hence improving the estimation accuracy. Finally, a triple redundant permanent magnet assisted synchronous reluctance motor is taken as an example to verify the feasibility and effectiveness of the proposed observer.

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.

Sensorless control methods based on flux observer have been widely used in motor drives with medium-high speed operation. However, the conventional methods have some shortcomings in estimation accuracy due to the dc bias caused by the integration, measurement, and parameter uncertainty. In this article, a new frequency adaptive disturbance observer with band-pass filter characteristics is proposed. It is insensitive to dc bias and high-frequency noise, hence improving the robustness of the system. Since the proposed method has no phase delay at any synchronous rotor frequency and can amplify the amplitude of the estimated active flux, it does not need a phase compensation module and can obtain a wider operating range. Moreover, an adaptive extended state observer is added to estimate the disturbance caused by parameter mismatch. The estimated disturbance is fed back to the estimated active flux, which further improves the accuracy of the system. Finally, experiments based on a triple redundant permanent magnet-assisted synchronous reluctance motor are accomplished to verify the effectiveness and accuracy of the proposed observer.

This article proposes a novel hybrid rotor flux-switching permanent magnet (PM) machine with a low torque ripple. The rotor of this machine is composed of inverted T-shaped PMs and surface-mounted PMs and the rotor teeth of the inverted T-shaped PM and the surface-mounted PM are designed with a modified shape. Compared with the conventional inverted T-shaped PM machine, the hybrid PMs arrangement of the proposed machine introduces additional air-gap flux density time–space harmonics based on the flux modulation principle. Especially, these harmonics contribute to negative torque ripples and further counteract the positive torque ripple harmonics to suppress total torque ripples. Furthermore, the feasibility of the proposed machine is verified by comparing and analyzing the electromagnetic and mechanical performances of the conventional machine and the proposed one. Finally, a prototype was fabricated to verify the effectiveness of the proposed machine.

This article proposes a new multi-mode high-efficiency fault-tolerant permanent magnet machine with an inner stator to place AC field windings. The q -axis current in the field windings enables the proposed machine to be driven individually or together with the armature windings. On the other hand, the flux can be regulated by applying the d -axis current to the field windings. As a result, multiple operation modes are realized. The proposed machine can run in different modes at different torque and speed operating conditions, implementing the multi-zone high-efficiency operation. Meanwhile, a new fault-tolerant control method can be applied in the proposed machine by combining the mode switching and compensation current in the healthy windings, thus improving the efficiency under fault-tolerant operation. Moreover, the multi-zone high-efficiency regions of the proposed and conventional machines are investigated. The proposed and traditional fault-tolerant methods for the proposed machine are compared. The results reveal that the proposed machine offers a larger high-efficiency region and is capable of stronger fault tolerance. Furthermore, since the double stators in the proposed machine need to operate individually, a swallow-shaped rotor with auxiliary salient poles is adopted to reduce outer torque ripple and inner torque ripple. Finally, the experiments are performed to verify the predicted performances.

In this paper, a new fault-tolerant control (FTC) strategy based on minimum torque ripple is proposed for a triple redundant permanent magnet assisted synchronous reluctance motor under single-phase and double-phase faults. Different from removing the faulty modules (single six-phase (S6) operation or single three-phase (S3) operation), the proposed strategy makes full use of the healthy phase of the faulty modules. By precisely controlling the d-q axes currents of each module, the ripple of permanent magnet torque and reluctance torque can be suppressed simultaneously, thus achieving the minimum output torque ripple. Moreover, the ratio ( k ) of the d-q axes current to the stator current can be determined under the constraint of minimum copper loss. In addition, by changing the ratio k , the proposed strategy can be combined with S6 or S3 strategy to achieve the minimum copper loss in a wide torque range. In summary, the proposed FTC strategy not only achieves the minimum torque ripple but also ensures the minimum copper loss. Finally, experiments are carried out to verify the accuracy and validity of the theory.