Magnetic Motive Force Research Articles

Output feedback linearization control for nanorobots with actuator and sensor delays

This paper proposes an output predictive control design for the endovascular magnetic resonance imaging (MRI)-guided nanorobots in the presence of actuator and sensor delays. The nanorobot is modeled considering the effects of hydrodynamic drag force, apparent weight, and magnetic motive force. Using feedback linearization approach, the state feedback control is designed. To physically implement the predicted states in the state feedback control, the high-gain predictor is constructed. The performance recovery property of the output feedback using the high-gain predictor is achieved. The numerical simulation demonstrates the effectiveness of the designed controllers and the performance recovery property of the designed high-gain predictor.

Generalized Fault-Tolerant Model Predictive Control of Five-Phase PMSM Drives Under Single/Two Open-Switch Faults

To address both single open-switch fault (OSF) and arbitrary two OSFs of a five-phase permanent magnet synchronous motor (PMSM) drive, a generalized fault-tolerant model predictive current control method is proposed in this article. Firstly, the postfault currents under OSFs are analyzed in the stationary frame based on the Fourier method. Then, to maintain torque output capacity and alleviate torque ripple, the optimal reference currents in fault scenarios are deduced with the principle of rotating magnetic motive force undisturbed. Further, the obtained phase currents are transformed into the rotating frame and applied in the cost function for the voltage vector optimization. Thus, the torque under post-fault operations is guaranteed and the torque ripples are suppressed. Finally, various experiments are conducted to validate the feasibility of the generalized fault-tolerant control method of five-phase PMSM drives.

Study on the influence of dual-winding optimization design on the torque and suspension performance of bearingless motor

Abstract The bearingless motor with dual-winding embedded in the stator can not only produce electromagnetic torque and can also produce suspension force to support the rotor suspension, and the design of the dual-winding will directly affect the torque and suspension performance of the motor. It is a complex problem of multi-objective optimization, multi-performance coupling, and multi-parameter collaborative optimization, which is great significance to improve the comprehensive performance of the motor. Firstly, in order to solve the problem of slot space ratio and turns design of dual-winding under the restriction of stator slot space and thermal loading, the calculation formulas of the electromagnetic torque and the suspension force are derived. The influence of dual-winding design on electromagnetic loading, thermal loading, torque and suspension performance are analyzed. The linear variation of electromagnetic torque with the slot space ratio of torque winding is obtained, and the influence of the dual-winding magnetic motive force on suspension force is clarified. Secondly, in order to obtain the dual-winding design scheme with the optimal torque and suspension performance, the performance parameters of the motor are calculated by finite element method and the influence of the slot space ratios of the torque winding on the torque and suspension performance is analyzed. Based on the coupling analysis of the electromagnetic torque and the suspension force in the case of different thermal loading distributions of dual-winding, the dual-winding optimal design of the bearingless motors is given. Finally, the suspension force of a prototype is tested by experiment.

A Torque-Compensated Fault-Tolerant Control Method for Electric Vehicle Traction Motor with Short-Circuit Fault

The development of traditional vehicles which consume fossil carbon-based fuels is constrained by environmental pollution and the energy crisis, and it has become a social consensus to develop electric vehicles with new energy resources and low emissions. The drive system of electric vehicles should be able to reliably operate over a long period. When a short-circuit fault occurs in the driving motor, the current in the winding will increase sharply and threaten driving safety. This paper proposed a short-circuit fault-tolerant control strategy for a dual three-phase permanent magnet synchronous traction motor (DT-PMSTM) which can resolve the problem of short-circuit faults. The current in non-short-circuit fault windings has been reconstructed to offset the interference of the short-circuit current and output a stable torque. Based on the principle of constant composited magnetic motive force (MMF), the dimension-reduced orthogonal transformation matrix was derived. The compensation currents were designed according to the interference effect of the short-circuit current to the normal MMF of the motor. Consequently, the lost torque component caused by the lack of the short-circuit winding was compensated, and the torque pulsation was also reduced. The performance of the topologies with neutral point-isolated mode and neutral point-connected mode were both investigated and compared. The validity of the proposed short-circuit fault-tolerant control strategy was proved by the simulation results.

Loss Investigation for Multiphase Induction Machine under Open-Circuit Fault Using Field–Circuit Coupling Finite Element Method

This paper focuses on the loss estimation for the multiphase induction machine (IM) operating under fault-tolerant conditions through the field–circuit coupling finite element method (FEM). Both one-phase and two-phase open-circuit faults of a seven-phase IM are researched, and different spatial positions of the fault phases are taken into consideration. The magnitudes and phase angles of the residual phase’s current are deduced based on the principle of equal magnitude of the residual phase currents and unchanged fundamental magnetic motive force (MMF). The magnetic fields’ coupling between the fundamental and harmonic planes is analyzed. Then, the time-stepping electromagnetic fields calculation of the seven-phase IM are carried out under the commercial software Simplorer–Maxwell environment. The transient and steady performance for both the health and fault conditions are obtained based on the rotor field-oriented control (RFOC) strategy. The Joule loss and iron loss are calculated for the torque step and slope responses. The seven-phase motor driving platform is established to verify the numerical calculation results. The proposed method is effective for predicting the loss and designing a reasonable operating range for multiphase IM operating under fault-tolerant conditions considering the thermal balance.

Optimising the flux barriers of interior permanent magnet machine for noise reduction under certain load conditions

This study proposes a method to reduce the electromagnetic noise of a double-layer interior permanent magnet synchronous motor (DIPMSM) by optimising the flux barrier. First, a noise prediction model of the 36-slot/8-pole DIPMSM is established by finite element (FE). According to the simulation results, the noise of the motor is the loudest at 5000 rpm, especially with a noise component of 3333.3 Hz. From the results of modal analysis, it can be concluded that the four-order radial force with a frequency of 3333.3 Hz resonates with the stator, resulting in the loudest noise. Then, the source of the radial force that causes the loudest noise is analysed, and it can be found that the 9th and 11th harmonics of rotor magnetic motive force have the greatest contribution to the force. By optimising the rotor, the radial force contributed by the 9th and 11th harmonics is weakened, thereby reducing the noise caused by these harmonics. Finally, the electromagnetic performance and noise of the optimised motor are checked by FE. Compared with the initial rotor, the torque ripple is reduced by 26.79%, and noise is reduced by 5.542 dB. The noise test on the prototype verifies the accuracy of the noise prediction model.

A novel speed control strategy for 3-phase induction motor drives with star-connected under single-phase open-circuit fault using modified RFOC strategy

In this research, a novel control method is proposed for 3-Phase Induction Motor (3-PIM) drives with star-connected under Single-Phase Open-Circuit (SPOC) fault using modified Rotor Field-Oriented Control (RFOC) strategy. The standard RFOC strategy is designed based on the d−q model of 3-PIM during normal mode. This strategy cannot be applied for a 3-PIM under SPOC fault as the model of a healthy 3-PIM is different from the model of a faulty 3-PIM. The use of standard RFOC strategy for Vector Control (VC) of a 3-PIM under SPOC fault increases the electromagnetic torque ripples during this fault. To overcome this problem, two unbalanced rotational transformations are used. A Current Transformation Matrix (CTM) is obtained based on the concept of maintaining value of Magnetic Motive Force (MMF) of the faulted machine like the healthy machine. Then, a Voltage Transformation Matrix (VTM) is introduced by using the presented CTM and according to the Single-Phase Induction Motor (SPIM) model. Based on the results, faulted machine RFOC equations were obtained similar to the healthy machine RFOC equations by using the CTM and VTM. The proposed technique was verified by simulations and experiments. Results indicated that the performances of the faulted machine under the proposed RFOC strategy are better than standard control techniques.

Torque Improvement in Dual M-Phase Permanent-Magnet Machines by Phase Shift for Electric Ship Applications

This paper proposes a design technique for electric ship traction machines to achieve high torque density and low torque ripple by adopting dual <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> -phase windings with an appropriate phase shift. Firstly, the general relationship between the slot number and the phase number for dual <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> -phase windings is investigated. Secondly, the uniform analytical expressions of torque with different phase shifts are derived. Also, the optimal phase shift angle is summarized from the perspective of improving torque performance. Then, the 48-slot and 22-pole permanent-magnet machines for electric ship with different windings configurations are designed. The finite-element method is used to calculate their electromagnetic performances, such as back electromotive force, torque capability, stator magnetic motive force and radial force. Finally, some experiments on the prototype machine for electric ship are carried out for validation.

Anti-Demagnetization Capability Research of a Less-Rare-Earth Permanent-Magnet Synchronous Motor Based on the Modulation Principle

In this article, a new method of enhancing the anti-demagnetization capability based on the modulation principle is proposed for a less-rare-earth permanent-magnet synchronous motor (PMSM). By means of analytical method, the relationship between the demagnetization effect and the air gap flux density, calculated by magnetic motive force (MMF) and magnetic permeance, is established. By implementing the design of the fundamental harmonic modulation, the anti-demagnetization capability of the less-rare-earth PMSM can be improved. Using the finite-element method, the electromagnetic performances of the initial and optimal motor are analyzed and compared in detail, including the demagnetization characteristics and torque characteristics. Finally, theoretical analysis and simulation results verify the effectiveness of the proposed method.

Low-Loss-Design of a Flux-Switching Motor Considering Air-Gap Harmonics

In this paper, a new low-loss-design method based on MMF harmonics is proposed for a flux-switching permanent magnet (FSPM) motor. By analytical method, the relationship between permanent magnet loss and air-gap harmonics caused by magneticmotive force (MMF) is deduced theoretically. By introducing a loss impact factor, the correlation designs among the impact factor, PM loss, torque and cogging torque are carried out to realize the PM loss reduction with comprehensively optimal motor performances. By utilizing finite-element method, the electromagnetic performances of initial and optimal motor are analyzed and compared in detail, consisting of PM loss and torque performances. Finally, theoretical analysis and simulation results verify the effectiveness of the proposed design method and motor.

Fault‐tolerant FOC for five‐phase SPMSM with non‐sinusoidal back EMF

A fault-tolerant field-oriented control (FOC) is proposed for five-phase surface-mounted permanent magnet synchronous motor (SPMSM) with non-sinusoidal back electromotive force under single-phase open-circuit fault. On the basis of the concept of preserving the circular rotation of fundamental magnetic motive force and PM flux linkage, the decoupled model of five-phase SPMSM under single-phase open-circuit fault is derived. To suppress the torque ripples caused by third-harmonic content of PM flux linkage, the closed-form solution of current references with zero-torque pulsation in the synchronous coordinate is presented. Then, the presented solution is used for obtaining optimum current references to achieve minimum stator winding losses and maximum available torque while satisfying the zero-torque-pulsation constraint. The optimal current references generation method is simple and is suitable for real-time implementation. The experimental results confirm that the proposed method can effectively suppress the torque ripples and produce lower stator winding losses as well as wider-torque operation range compared with traditional fault-tolerant FOC method.

A Double-Stator Flux Switching PM Machine With Multi-PM MMF Harmonics

A double stator flux switching permanent-magnet machine (DS-FSPM) is proposed to improve the torque density and power factor of DS-FSPMs. As opposed to regular DS-FSPMs with spoke-PMs of the same pole arc, the pole arcs of the spokePMs in the proposed DS-FSPM are not exactly the same, which can produce multiorder PM magnetic motive force (MMF) working harmonics. Meanwhile, the total PM usage of the regular and the proposed DS-FSPMs is kept identical. In this paper, the working mechanism of the proposed DS-FSPM is introduced, and the effects of several key parameters including PM pole arc, slot-pole combination, split ratio, rotor thickness, and rotor width on torque and power factor are also analyzed.

Torque Ripple Reduction in Five-Phase IPM Motors by Lowering Interactional MMF

This paper proposes a torque ripple reduction method for a five-phase interior permanent magnet (PM) motor by shifting asymmetrical rotor poles. The key of this method is to consider the PM torque ripple, reluctance torque ripple, and cogging torque simultaneously from two aspects. First, the main interactional harmonic, contributing to PM torque ripple, between stator magnetic motive force (MMF) and rotor MMF is developed. Then, the appropriate combination of unequal pole arcs is adopted to eliminate the main interactional harmonic. Second, the asymmetrical rotor pole-pair is selected as a repeating unit which produces cogging torque and reluctance torque with consistency in waveforms and phases. Then, three methods for shifting asymmetrical rotor pole-pair are proposed showing that the torque ripple can be reduced greatly and the lower-order harmonics of radial force is acceptable when the shifting angle of the repeating unit is 4.5 mechanical degrees. Through theoretical analysis and experimental test, it is verified that the proposed motor can offer lower torque ripple even under deep flux-weakening region.

An equivalent circuit of the single‐sided linear induction motor considering the discontinuous secondary

Due to the influence of the switch and rail equipment, the secondary cannot be laid continuously in the linear metro. An equivalent circuit of the single-sided linear induction motor (SLIM) is presented to consider the discontinuity of the secondary plate, and the electromagnetic characteristics of the motor with the discontinuous secondary are obtained. First, the analysis model of the SLIM considering the missing part of the secondary plate is proposed. Second, the variation of the length of the coupled region between the primary and secondary are considered by the method of approximate linearisation to correct the parameters including the primary leakage inductance, magnetising inductance, secondary resistance and secondary leakage inductance. Third, three typical cases of the relative position between the primary and discontinuous secondary are analysed, and the equivalent circuit in each case is deduced according to the distribution of the secondary magnetic motive force and air gap flux density. Then, two coefficients considering the longitudinal end effect, on the basis of the corrected secondary time constant, are proposed to correct the magnetising inductance and secondary resistance. Finally, the analytical results are verified by the results measured on the test rig of an SLIM.

Third Harmonic Current Injection in Fault-Tolerant Five-Phase Permanent-Magnet Motor Drive

This paper presents a third harmonic current injection method for a five-phase permanent-magnet (PM) motor with trapezoidal back electromotive force (EMF) under postfault field oriented control (FOC). The key of the proposed method is the third harmonic current online calculation and injection under postfault FOC. The postfault FOC lies in the fundamental decoupled model based on the concept of maintaining spatial circular rotation of fundamental PM flux linkage vector and magnetic motive force under open-circuit fault. Based on the mathematical model of torque pulsations caused by third harmonics of air-gap flux, the injected third harmonic current can be calculated by the radio of the amplitude of third harmonic EMF and fundamental EMF easily. The presented fault-tolerant control strategy can achieve the real time optimal current reference generation and third harmonic current injection under postfault FOC while reducing the torque pulsations. The effectiveness of the proposed method is verified by experimental results under various operation conditions.

Three-Dimensional Temperature Field Calculation and Analysis of an Axial-Radial Flux-Type Permanent Magnet Synchronous Motor

This article concentrates on the steady-state thermal characteristics of the Axial-Radial Flux-Type Permanent Magnet Synchronous Motor (ARFTPMSM). Firstly, the three-dimensional mathematical models for electromagnetic calculation and analyses are established, and the machine loss, including the stator loss, armature winding loss, rotor loss, and axial structure loss is calculated by using time-step Finite Element Method (FEM). Then, the loss distribution is assigned as the heat source for the thermal calculation. Secondly, the mathematical model for thermal calculation is also established. The assumptions and the boundary conditions are proposed to simplify the calculation and to improve convergence. Thirdly, the three-dimensional electromagnetic and thermal calculations of the machine, of which the armature winding and axial field winding are developed by using copper wires, are solved, from which the temperature distributions of the machine components are obtained. The experiments are carried out on the prototype with copper wires to validate the accuracy of the established models. Then, the temperature distributions of machine components under different Axial Magnetic Motive Force (AMMF) are investigated. Since the machine is finally developing by using HTS wires, the temperature distributions of machine developed by utilizing High Temperature Superconducting (HTS) wires, are also studied. The temperature distribution differences of the machine developed by using copper wires and HTS wires are drawn. All of these above will provide a helpful reference for the thermal calculation of the ARFTPMSM, as well as the design of the HTS coils and the cryogenic cooling system.

Analysis on the Amplitude and Frequency Characteristics of the Rotor Unbalanced Magnetic Pull of a Multi-Pole Synchronous Generator with Inter-Turn Short Circuit of Field Windings

Inter-turn short circuit of field windings (ISCFW) is a common generator fault which can result in serious safety accidents for power systems, if the fault is not eliminated in time. Taking advantage of the electrical and mechanical characteristics of the generator after a fault as a fault criterion is a new idea for fault monitoring, so finding out the frequency and amplitude frequency characteristics of rotor unbalanced magnetic pull (UMP)—the vibration excitation source of the fault—is the basis and key of the research. Taking a six-pole generator as an example, the effects of harmonic magnetic motive force (MMF) interaction on rotor UMP, as well as the frequency characteristics of rotor UMP after generator faults in different stator windings, are obtained based on the analysis of the air-gap MMF of the generator after a fault, and the results of theoretical analysis are verified by simulation. Based on the above results, the simulation calculation on rotor UMP of generators with three stator winding forms under different operating conditions has been achieved, to get the relation between rotor UMP amplitude and active power and field current, and to find out the mechanism of rotor UMP amplitude change along with operating conditions and effect of stator winding forms on UMP amplitude by theoretical analysis. The conclusions are of important significance for studying fault mechanical characteristics of generators and lay a foundation for online monitoring on ISCFW by integrating mechanical and electrical information.

An analytical model of harmonic content no-load magnetic fields and Back EMF in axial flux PM machines regarding the iron saturation and winding distribution

PurposeThis paper aims to propose an analytical model for the harmonic content no-load magnetic fields and Back electric motive force (EMF) in double-sided TORUS-type non-slotted axial flux permanent magnet (TORUS-NS AFPM) machines with surface-mounted magnets considering the winding distribution and iron saturation effects.Design/methodology/approachFirst, a procedure to calculate the winding distribution with a rectangular cross-section is proposed. The magnetic field distribution and magnetic motive force (MMF) drop due to saturation in iron cores are then exactly extracted in a 2-D analytical model. The consequent influence on air-gap magnetic field and Back EMF are also calculated using a new iterative algorithm. The results are compared with those of the conventional analytical model without saturation, 2-D finite element analysis (FEA) and an experiment on a fabricated prototype machine.FindingsUnlike the conventional method, the new method yields the no-load magnetic field distributions in air-gap and iron cores and Back EMF very exactly such that the results well match to those of the FEA and experiment.Originality/valueUnlike the conventional winding factor, the winding distribution is considered here along the both axial and circumferential directions, which improves the accuracy level of results for non-slotted structures with relatively large air-gaps. The magnetic field distribution and MMF drop-in iron parts are also calculated as the basis for exact recalculation of air-gap magnetic field and Back EMF. Because of small computational burden beside superior accuracy, the proposed model can be treated as an accurate and fast substitute for FEA to be used during the design procedure or for predicting the other performance characteristics of TORUS-NS AFPM machines.

Design and Analysis of a New Five-Phase Brushless Hybrid-Excitation Fault-Tolerant Motor for Electric Vehicles

High reliability and wide range of speed regulation are key factors for motor drive system in electric vehicles (EVs). To meet the requirement for EV application, this paper proposes and investigates a new five-phase brushless fault-tolerant hybrid-excitation motor. This motor has several advantages over the conventional permanent magnet (PM) motor, such as high fault tolerance and adjustable flux. In addition, to realize flux regulation, based on the utilization of the high-harmonic component of the stator magnetic motive force (MMF), the rotor field winding and the rotor harmonic winding are designed. Unlike the existing hybrid-excitation machines with rotor PM, the proposed motor can achieve the balance between simple structure and no sliding contacts. Moreover, the topology and operation principle of the proposed motor are analyzed. Also, the characteristics of the proposed motor are investigated by using finite-element analysis and experiments with a 2 kW prototype machine. The experimental results are given to be consistent with the theoretical analysis, which validates the correctness of the theory.

Decoupled Modeling and Nonlinear Speed Control for Five-Phase PM Motor Under Single-Phase Open Fault

Fault-tolerant control of a five-phase (5Ph) permanent magnet (PM) motor has been recently widely studied, however decoupled modeling under faulty conditions is discussed in less details. In this paper, decoupled model of the 5Ph PM motor under single-phase open fault is investigated and based on the proposed model field oriented control (FOC) is applied to the motor. The proposed model is based on the concept of preserving values of fundamental magnetic motive force (MMF) and back electromotive force (EMF) under single-phase open fault, the same as in healthy case, along with keeping equal torque equation at fundamental rotating space. Nevertheless, the output torque still presents some noises due to third harmonics of air-gap flux and system uncertainties, and to cope with those disturbances, sliding mode control (SMC) is proposed in the speed loop to improve the speed performance. The proposed SMC contains a PI controller and a chattering term, and thus it can be easily tuned. The decoupled model is verified by transient finite element analysis finite element analysis (FEA) and further experiment results are presented to confirm the effectiveness of the proposed control strategy.