The equivalent circuit of an induction machine (IM) without regard to iron loss would lead not only significant mismatch between simulation and experimental results but also deteriorate the vector control performance. This study focuses on modifying the indirect rotor flux-oriented controller subject to the IM equivalent circuit with consideration of stator and rotor core losses. An analytical approach based on the core-loss model for estimating the rotor slip shows salient impact of the stator and rotor core loss on IM performance. A 10 HP IM is performed for laboratory test. The experimental and simulation results validate that the modified vector controller is superior to the conventional vector controller in both transient and steady-state responses.

In this study, the authors present a control method for the permanent magnet synchronous motor (PMSM) driven X–Y motion system for application in industrial and manufacturing apparatus. Backlash and friction effects in ball-screw actuated systems are common obstacles to achieve high-accuracy control. The authors investigate the indirect fuzzy controller to demonstrate the feasibility of reference trajectory tracking and derive an adaptive law in the error state space to deal with parameter uncertainties and external disturbances. The authors adjust the fuzzy parameters online, based on the Lyapunov stability theorem, such that the asymptotic stability of the whole system and error convergence can be guaranteed. In the authors’ experiments, this indirect fuzzy control approach compensated for the non-linear friction and disturbance variation of the biaxial linear stage following the application of four contour shapes, i.e. square, triangular, star, and circular reference contours. Both the authors’ simulation and experimental results demonstrate substantial improvement in contour tracking performance in terms of average tracking error and tracking error standard deviation, as well as robustness against platform uncertainties.

Brushless Harmonic current injection to the stator windings is one of the most effective methods for torque ripple reduction of brushless DC motors. Because of multi harmonic contents of the stator currents, the conventional methods based on rotational reference frame cannot be used to calculate the voltage references for voltage source inverter. sliding mode control (SMC), which has high dynamic response to track a time varying command, can be used to force the arbitrary reference current to the stator windings without transfer the motor currents to the rotational reference frame. However, the main disadvantage of SMC is that the system states cannot reach the equilibrium point in infinite time as well as has a major chattering problem. In this paper, a new control method called integral terminal sliding mode control (ITSMC) is used to overcome these drawbacks. In order to show the robustness and performance of the proposed method, this method is compared with a SMC by some simulation and experimental tests. It is concluded that the dynamic response and robustness of the proposed ITSMC method is higher than SMC and ITSMC is an appropriate method to inject the arbitrary reference current to the motor windings.

Magnetic gears, an alternative to conventional mechanical gearboxes, have been extensively studied in the last decade. By combining a magnetic gear and a conventional permanent-magnet machine into one frame, different magnetic-gear-integrated permanent-magnet machines with a high-torque density are obtained, among which the pseudo-direct-drive permanent-magnet machine features both a high-torque capability and a good power factor with an acceptable structural complexity. However, the stator PM array in the conventional pseudo-direct-drive permanent-magnet machine obstructs the magnetic path and reduces the excitation torque due to the coils. Another problem is the large permanent-magnet amount which increases the overall cost. The authors propose a novel topology which has an improved torque capability under the same excitation current with a reduced permanent-magnet amount. The working principles of the proposed machine are analysed theoretically using the linear-material assumption to decouple the permanent-magnet-machine part and the magnetic-gear part. Its performance is then validated by the finite-element method. A comparison study with the conventional topology is conducted to show its merits.

This study investigates the influence of rotor topologies and winding configurations on the electromagnetic performance of three-phase synchronous reluctance machines (SynRM) with different slot/pole number combinations, e.g. 12-slot/4-pole and 12-slot/8-pole. Transversally laminated synchronous reluctance rotors with both round flux barrier and angled flux barrier have been considered, as well as the doubly salient (DS) rotor as that used in switched reluctance machines. Both concentrated and distributed winding configurations are accounted for, i.e. single-layer and double-layer conventional and mutually coupled windings, as well as fully pitched winding. The machine performance in terms of d- and q-axis inductances, on-load torque, copper loss, and iron loss have been investigated using 2D finite-element analysis. With appropriate rotor topology, 12-slot/4-pole and 12-slot/8-pole machines with fully pitched and double-layer mutually coupled windings can achieve similar torque capacity, which are higher than the machines with other winding configurations. In addition, the synchronous reluctance machine with round flux barrier can have lower iron loss than DS reluctance machine under different working conditions. The prototypes of 12-slot/8-pole single layer and double layer, DS SynRM have been built to validate the predictions in terms of inductances and torques.

This study proposes direct torque and flux control of dual-inverter-fed open-end winding induction motor (OEWIM) with the help of model predictive control. OEWIMs are extensively used in electric vehicles and for ship propulsion but they require a high dynamic performance. Predictive torque control (PTC) retains the features of direct torque control and offers a high dynamic performance by eliminating start-up problems. In this study, predictive torque control is implemented for multilevel inversion-fed OEWIMs. Multilevel inversion is obtained by operating two two-level inverters with equal and unequal DC link voltages. The proposed study gives a comparative analysis of PTC of OEWIM for various speeds and numerical analysis of torque ripple and flux ripple. The proposed methods are simulated using MATLAB/SIMULINK and experimental response shows the validity of the developed methods.

This study presents a force and torque model utilising transfer-matrix theory for a novel electrodynamic suspension reaction sphere (EDSRS), which features a compact structure and low cost. A motor in the EDSRS is unfolded along the directions of the circumference and the arc of the stator iron core, then it can be regarded as a non-back-iron linear induction motor (NBILIM) with infinite length in the longitudinal direction. The NBILIM is simplified and extended by arranging infinite duplicates side by side along the transverse direction, constructing an extended simplified linear induction motor (ESLIM). Applying the transfer-matrix theory to each layer of the ESLIM, the relationship between the magnetic fields at two boundaries is obtained, and corresponding boundary conditions are presented. An analytical model is derived based on the magnetic field. Furthermore, the errors of this analytical model are analysed and modified coefficients are obtained from finite element method (FEM) simulation. A modified model of the EDSRS is developed according to the analytical model. Finally, the proposed model is verified by FEM simulations and experiments on a prototype, and a suspension and rotation experiment is conducted.

In this study, a direct torque control (DTC) strategy based on a novel switching table for induction motor drives fed by the eight-switch three-phase inverter (ESTPI), which is the post-fault reconfigured topology for the three-level neutral-point-clamped inverter with the open-circuit fault occurring in a leg, is proposed to reduce the torque ripple and suppress the dc-link capacitor voltages offset. The influence of each basic voltage vector provided by the ESTPI on the stator flux, the electromagnetic torque and the dc-link capacitor voltages is analysed in detail, and the causes of the torque ripple and the capacitor voltages offset are also revealed. To suppress the dc-link capacitor voltages offset, a hysteresis comparator is added to regulate the dc-link capacitor voltages. Based on that, an optimised switching table to achieve not only torque ripple reduction but also dc-link capacitor voltages offset suppression is proposed. The feasibility and the effectiveness of the proposed DTC strategy are verified by simulations and experimental results.

This study first proposes a novel position sensorless control method for doubly salient electro-magnetic motor (DSEM) based on line-to-line voltage. The commutation instants are estimated by comparing the proper line-to-line voltage with a commutation threshold value, which is preset according to motor speed and field current. Since only line-voltage is required, the negative influence of DSEM neutral point voltage variation is eliminated. Moreover in addition, line-to-line voltage has a gain of phase back-electromotive force (EMF), so the application speed range is desired to be extended. Then, the sensorless commutation lags introduced by reluctance back EMFs and low-pass filters are analysed in detail, with the obtained mathematic expressions, a uniform compensation strategy by adjusting the commutation threshold value is proposed. With no need for extra hardware, the compensation strategy has the merit of easy implementation. What is more, to overcome the restriction of the distorted commutation signal arising in freewheeling process, a constraint of three-phase currents is developed to avoid false commutation. Finally, the experiments on a 12/8-pole DSEM validate the correctness and feasibility of the proposed techniques.

Electric propulsion is widely used in ship propulsion systems, and multiphase machines are gaining increasing popularity because of their fault-tolerant ability, high power density, and reduced torque ripple. This study concentrates on the tandem ship propulsion configuration with two 15-phase induction machines (IMs) fixed on the same shaft. Based on field-oriented control and reconfiguration fault-tolerant control for the single 15-phase IM, the master–slave coordinated control strategy is designed for the tandem motors, which can not only achieve power allocation between two motors during normal operation, but also minimise the total stator copper loss of the two motors and maximise the propulsion output power ability during fault-tolerant operation. Experiment results from a ship propulsion experimental platform verify the effectiveness of the proposed control strategies.

Direct torque and flux control (DTFC) is known for its reduced torque and flux ripples compared to the classical direct torque control scheme. It can drive an interior permanent magnet synchronous motor (IPMSM) in usual control regimes while satisfying current and voltage limits of the system. However, deep flux-weakening control of an IPMSM under DTFC has not been investigated as extensively, especially operation along the maximum torque per voltage (MTPV) trajectory in the torque-flux plane. This study proposes a simple and effective control method, which incorporates MTPV trajectory in the conventional flux-weakening algorithm of DTFC. Performance of an IPMSM drive is analysed when operated with the proposed control method.

This study discusses the modelling of torque and speed characterisation of the double stator slotted rotor brushless DC motor (DSSR-BLDC). Most double stators have a surface mount rotor structure. The problem with this structure is that it has a large air gap, expensive permanent magnet, and cannot operate at high speed. In addition to flux leakage when this type of rotor structure is used. To overcome this problem, the DSSR-BLDC has been introduced. The usage of the DSSR-BLDC is to minimise the flux leakage, thus increasing the flux linkage. This will increase the torque production for the DSSR-BLDC. The aim of this research is to model the torque and speed characterisation of the DSSR-BLDC. This model uses the permeance analysis method and finite element method. The maximum torque and speed can be determined using both methods. The analyses of the electromagnetic torque, output power, and efficiency for various voltages are also presented. The simulation and measurement result show a good agreement with each other. The highest measurement value of the electromagnetic torque is 11 N m at 100 rpm. In conclusion, this study reveals that the modelling of the torque and speed characterisation of the DSSR-BLDC is suitable for portable applications.

This study presents an experimental validation and robustness evaluation of predictive current control and reactive power minimisation strategy for a three-level three-phase four-wire indirect matrix converter. The proposed topology features a unification of conventional four-leg indirect matrix converter with an additional four switches circuit resembling a back-to-back buck circuit to synthesise multi-level variable dual dc-link voltage. A systematic rectifier switching strategy is elaborated to ensure positive fictitious dc-link voltage at any instant. The proposed control and topology have been tested under various transient and steady-state conditions for comprehensive robustness evaluation. The experimental results reveal an outstanding independent load current reference tracking with low ripple current and the reactive power minimisation has been achieved by tuning the weighting factor. The load current tracking and reactive power minimisation have been achieved by properly tuning the weighting factor. The load current harmonics distortion is recorded <5% during normal operating conditions.

This study proposes an isolated on-board integrated battery charger using an interior permanent magnet (IPM) machine with a nine-slot/eight-pole combination or its multiples, and equipped with a non-overlapped fractional slot concentrated winding. The proposed winding layout comprises three three-phase winding sets that are connected in such a way as to provide six motor terminals. Hence, a six-phase or two three-phase converters will be required for propulsion. Under motoring mode, the machine can be effectively regarded as a six-phase machine, which provides a high fault-tolerant capability, and allows for a ‘limp home’ mode of operation. Additionally, all magneto motive force subharmonics are eliminated, which significantly reduces the induced rotor eddy current losses, when compared with a conventional three-phase motor having the same slot/pole combination. In battery charging mode, the winding is reconfigured, so that the machine is considered as a three-phase to six-phase rotating transformer. A 40 kW IPM machine is designed and simulated under different modes of operation using two-dimensional finite element analysis to validate the proposed concept. A small-scale prototype machine is also used for experimental validation.

In this paper, an analytical expression of cogging torque considering flux-leakage effect for FRPM machines with different magnetization methods of magnets is derived based on co-energy and magneto motive force-permeance model. Then, the influences of machine parameters (including PM width and rotor tooth width) on cogging torque as well as its harmonic spectra are analysed according to this derived model. Consequently, an effective method to diminish cogging torque is obtained by optimally choosing rotor tooth/PM width. Besides, the skewing and chamfering methods are also discussed. Then, with the aid of 2D finite element analysis (FEA), the above theoretical analysis and the proposed cogging torque suppression methods are verified by two exampled 6-stator-slot/8-rotor-pole FRPM machines with different magnetized magnets. Finally, these two exampled machines are fabricated and tested to further validate the derived model and FEA analysis. It turns out that the cogging torque of both magnetization methods are completely the same and it can be minimized by optimally choosing machine design parameters during the design stage. Then, combined with the skewing, cogging torque can be reduced further. However, chamfering is not recommended in this type of machine since it may aggravate asymmetric back-EMFs.

This study proposes an improved finite-state predictive torque control (FS-PTC) to minimise the torque ripples of switched reluctance motor (SRM) drive. Firstly, based on the accurate analytical method, a discrete time model is established for predicting the future states of SRM drive system. Secondly, to reduce the computational burden, a new switching table is constructed for the predictive controller by using the sector partition technique. Further, the torque ripple, copper losses, and average switching frequency are considered synchronously by using a multi-objective cost function. As a result, the proposed FS-PTC method not only can minimise the torque ripple but also can reduce effectively the copper losses and average switching frequency. Finally, the experimental results are carried out for a three phase 12/8 poles 1.5 kW SRM with the proposed control algorithm and the results are compared with conventional direct instantaneous torque control algorithm. These results demonstrate the effectiveness of the proposed method.