Wenjuan Hao

The bearingless slice motor employed in ventricular assist devices must deliver not only ultra-clean operation but also exceptionally low speed fluctuations to ensure precise flow control. While feed-forward compensation for cogging torque within the vector control framework can mitigate these fluctuations, the predictive accuracy of such strategies is limited by existing analytical models. These models, which are grounded in conventional magnetic field modulation theory, often neglect the critical modulation effect of stator saturation, leading to significant errors. To address this gap, this article introduces a novel analytical method for cogging torque based on a synchronous rotation saturation modulation (SRSM) factor. First, the modulation mechanism of the SRSM factor is analyzed. Second, the air gap permeance was reconstructed by introducing the SRSM factor, allowing for the complete and accurate determination of the harmonic pairs that generate cogging torque, thus achieving accurate analysis of cogging torque. Finally, experiments are conducted to verify the effectiveness and correctness of the proposed analytical method.

Eddy-current sensor-free control based on reusing Hall sensors of a bearingless slice motor system can reduce the volume, cost, weight, and the impact of shear on transmitted liquid. However, the algorithm will fail in the presence of the PM’s third harmonic. Hence, this article presents the eddy-current sensor-free control algorithm based on the two negative sequence coordinate transformation in parallel with different frequencies (TNSPDF). The random and disordered signal in the Hall output is modulated into asymmetrical component about the displacement vector angle through negative sequence coordinate transformation at different electrical frequencies, achieving decoupling between the displacement vector angle and the motor electrical frequency. The interference signal does not lead to any pulsation in the estimated displacement; rather, it evolves into a significant coefficient for the purpose of displacement identification. The validity and effectiveness of the proposed method are verified through experiments on a bearingless permanent magnet slice motor system.

Permanent magnet (PM) machines inevitably suffer from cogging force, which does not contribute to the average output torque (force) but contributes as a type of torque (force) ripple. This paper provides an overview of the cogging force reduction methods for different types of PM machines. First, a systematic and comprehensive categorization of different kinds of cogging force reduction methods is given according to the reduction principle. Then, the cogging force reduction methods for different types of PM machines are analyzed and discussed based on the categorization. Finally, according to the versatility and feasibility of the cogging force reduction methods, practical methods are recommended for different types of PM machines. The categorization, analyses, and recommendations presented in the paper are useful for the design of different types of PM machines with the requirement of cogging force reduction or output torque (force) ripple suppression.

Flux-switching permanent magnet (FSPM) machines can provide high torque density, strong flux-weakening capability, and high reliability, which makes these machines attractive in electrical drive systems. FSPM machines always employ different control methods, such as the vector control (VC) and direct torque control (DTC) methods. These methods exhibit different electromagnetic torque dynamic performances; hence, the dynamic performances of their rotor speeds are different. However,the proportional integral (PI) controllers of the speed loop in these methods are linear regulators, which hardly guarantee the optimal dynamic performance of the rotor speed. This causes the rotor speed to have several adjustments, overshoots, and a relatively long recovery time during the response to a sudden load change. Therefore, to achieve the optimal dynamic trajectory of rotor speed and maintain the excellent performance of the steady-state simultaneously, a torque-current ( I_q ) integral balance (IQIB) method, which can eliminate the restriction of the PI controllers on the dynamic performance of the rotor speed, is investigated for the VC system of FSPM machines. In the dynamic process, a group of optimal switch vectors is obtained to achieve the shortest recovery time and the minimum number of adjustments for the rotor speed without overshoot, thereby achieving an optimal dynamic performance for the system. Comparative experiments between the IQIB-based VC, VC, DTC, and improved DTC are conducted, and the accuracy and effectiveness of the proposed method are validated.

An open‐winding permanent magnet generator (OWPMG) system that offers features like fewer switching devices and high integration can be used in multi‐input generator systems. To achieve high‐accuracy position sensorless operation for the OWPMG system, this study investigates a phase‐shift‐free synchronous reference frame filter (SRFF‐PSF) for use in the sliding mode observer (SMO) position sensorless algorithm. The proposed SRFF‐PSF can completely restore the fundamental component of back‐electromotive force (EMF) without phase shift and filter out the high‐order harmonics owing to the following two improvements. First, the fundamental phase lag is eliminated by removing the low‐pass filter between the back‐EMF and the SRFF. Second, the error iteration of the output position angle is avoided by using the synchronous angle information from an additional phase locked loop module for the coordinate transformation of the SRFF. Based on the aforementioned improvements, the proposed method can effectively solve the phase shift problem in position estimation. The correctness and effectiveness of the method are verified by the experimental results.

The field winding based flux adjustable permanent magnet (FWFAPM) machines, including the hybrid excitation topology and the memory topology, can offer excellent capabilities in terms of flux regulation, wide constant power operation as well as de-excitation (flux-weakening) under fault, thus, they are capable for using in More Electric Aircraft (MEA) generator systems. First, this paper probes four basic hybrid excitation modes, and based on that, a general method deriving PM machines to hybrid excitation machines is established. The basic characteristics of each hybrid excitation mode considering the relationship between S-pole and N-pole are obtained for the first time. The performance differences of each hybrid excitation mode combined with different PM machines are summarized. Then, this general topology derivation method are extended for the memory topology, The unified derivation method of the single-PM topologies, the double-PM topologies and the triple-PM topologies for memory machines is systematically established.The general laws of the electromagnetic performance of each double-PM mode and triple-PM mode considering different relationships between NdFeB and AlNiCo are summarized for the first time. Finally, the control strategies for voltage regulation of aircraft generator systems are discussed based on the different critical control variables and controller types, a torque impulse balance control method which shows excellent dynamic performance for both target control variable and critical control variable has been achieved experimentally.

DC-DC converters with high dynamic performance are attracting more and more attentions in industry and academia. The charge balance control (CBC) method enables the single-input DC-DC (SIDD) converter system to achieve optimal dynamic performance. In this paper, the CBC method for the multi-port converter is proposed, and the analogy as well as the innovative transplantation approach of the CBC from single-input systems to multi-input systems are developed. First, general steps and unified equations of the CBC for SIDD converter are summarized. Second, through analogy analysis, the CBC method is transplanted to a full-bridge three-port converter(FB-TPC) system to improve the dynamic performance under load step change. Third, through innovative transplantation, a CBC strategy based on magnetizing current three-stage regulation is proposed, achieving optimal dynamic performance for the FB-TPC system under power distribution step change. Experimental results on a FB-TPC verify the feasibility and effectiveness of the CBC methods for multi-port converter and the transplantation method.

In view of the relatively low estimation accuracy in the low‐pass filter (LPF)‐based sliding mode observer (SMO) method, synchronous reference frame filter (SRFF)‐based SMO (without input LPF) method, and SRFF‐based SMO (with input LPF) method, an improved SRFF‐based SMO position sensorless method of the open‐winding permanent magnet generator (OWPMG) system is presented. This improved SRFF consists of a programmable eighth‐order low‐pass filter (8th‐PLPF), a traditional SRFF, and two phase‐locked loops (PLL1 and PLL2). Based on the synchronous angular frequency obtained by PLL2, the 8th‐PLPF together with the traditional SRFF can not only effectively filter out the harmonics in the output of the SMO but also achieve the fundamental back‐EMF without magnitude and phase angle errors. Then, based on the obtained accurate back‐EMF, the estimated rotor position angle can be obtained without phase shift. The OWPMG system using the improved method can work well in both steady‐state and dynamic conditions, which is verified by experimental results. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

In this letter, based on a structural decoupling design for the mover, a bearingless linear switched reluctance motor is proposed to simplify the levitation force control. This mover is designed to exhibit two decoupling features, one feature is that the levitation field and the armature field is decoupled by separating the levitation part and the armature part using the modular design with an E‐core structure. The other feature is the self‐inductance of the levitation module is decoupled from the mover position in the X‐direction by specially designed size of the levitation module. Based on this simple and decoupled mover structure, the levitation force can be controlled linearly by adjusting the magnitude of the levitation current without the information of the armature current and the mover position in the X‐direction, that is, the levitation current control is a simple scalar control, and the levitation force control and the thrust force control are structurally decoupled. Based on the FEA results, the design and theoretical analysis are verified. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.