Bearingless Switched Reluctance Motor Research Articles

Torque analytical model and self‐decoupling characteristics analysis of a bearingless switched reluctance motor

In this paper, a bearingless switched reluctance motor (BRSM) with sharing suspension windings, which simplifies the winding structure and reduces the complexity of the control circuit, is analysed. A torque analytical model is derived using the Maxwell stress tensor method, which provides better results, compared with the linear model in the magnetic saturated conditions. A finite element analysis (FEA) model of the prototype is built and used for comparison with the torque analytical model. The results show that the torque analytical model provides accurate results in the entire magnetic saturation region, which verify the feasibility of this model. In addition, the self-decoupling characteristics of this type of motor are illustrated using analytical model analysis, FEA and experimental analysis. The results indicate that BSRMs with sharing suspension windings can be flexibly controlled without using complex self-decoupling algorithms of conventional BSRMs. The presented work provides a theoretical basis for the control strategy.

Comparative performance analysis of bearingless switched reluctance motor

To solve the magnetic field coupling problem in the traditional bearingless permanent-magnet motor, which has magnets on the rotor, we propose two topologies of bearingless switched reluctance motors (BLSRMs) with magnets on the stator yoke. The first is a six/four-pole BLSRM with three pairs of permanent magnets on the stator and the second is a six/four-pole BLSRM with one pair of stator yoke magnets. First, the working principle of BLSRMs is introduced, including the structure and winding configuration, and the mechanism of generating levitation force is analyzed in detail. Based on 2D finite element analysis, the electromagnetic characteristics of the prototype are compared, including torque, suspension force, no-load back EMF, and no-load permanent magnet linkage. The calculation results show that at high speeds, the coupling between the levitation force winding and the torque winding of the BLSRM with one magnet pair is low, which allows for better decoupling performance and greater levitation force. In addition, although the motor with three pairs of permanent magnets in the stator yoke shows better torque performance, the loss of the motor is higher at a high speed. The research results lay a theoretical foundation for further research on a new type of bearingless motors.

Principles and Implementation of a Novel Radial-Anti-Disturbance Bearingless Switched Reluctance Motor

In order to solve the problem that the vehicle flywheel battery is easy to be disturbed in the process of using, a novel radial-anti-disturbance bearingless switched reluctance motor (RADBSRM) is proposed and studied based on the double stator switched reluctance motor. By widening the width of rotor poles, the flat top regions of all main winding inductances for each phase are constructed. By adopting the two-phase-conducting decoupling control rules, the electromagnetic torque and the main levitation force can be provided simultaneously. The auxiliary windings and the permanent magnet comprised in the inner stator can provide auxiliary radial suspension force, which can increase the radial load capacity, and also reduce the power consumption for suspension. The basic topology, operation principle, control method, and electromagnetic characteristics were all analyzed. Compared with double stator bearingless switched reluctance motor (DSBSRM), the results of finite element analysis method (FEM) verified that the capacity and stability of radial suspension force are both improved.

A Novel Dual-Channel Bearingless Switched Reluctance Motor

Bearingless switched reluctance motor (BSRM) has the advantages of high integration and low loss, and is especially suitable for flywheel batteries. In order to enhance the reliability and fault tolerance ability of BSRM, a novel dual-channel BSRM is proposed in this paper. This motor has the combined merits of switched reluctance motor and magnetic bearing, and can realize dual-channel fault-tolerant operation. The scalloped rotor poles are evenly distributed on the inner and outer walls of the rotor. All rotor poles are specially widened, which is benefit for raising the continuity of radial suspension force. Through the dual-phase-conduction decoupling control rules, the electromagnetic torque and suspension force can be generated simultaneously without serious coupling problem. The basic topology, operation principle, control method, and electromagnetic characteristics are analyzed. Field-circuit coupling joint simulation results of Simplorer and Maxwell confirm the feasibility of the proposed novel motor and the validity of decoupling control method.

Characteristic Analysis of a New Double Stator Bearingless Switched Reluctance Motor

In order to improve the performance of bearingless switched reluctance motor (BSRM), this paper proposes a new double stator bearingless switched reluctance motors (DSBSRM). The new DSBSRM adopts an inner and outer double stator structure, the inner and outer stators are separated by magnetic isolation frame to solve the coupling problem between torque control and suspending force control. In suspending control system, the new DSBSRM adopts the working mode of hybrid excitation, permanent magnets are used to provide a bias magnetic field, electromagnetic is used to adjust the magnitude of hybrid magnetic field, thus it has larger suspending force under the same current. Further, the torque mathematical model and the suspending force mathematical model are established, and the difference caused by rotor eccentricity in air gap reluctance and in magnetic flux leakage are considered for more accurateness in the suspending force mathematical model. The 2D simulation model of the new DSBSRM is established by using finite element simulation software, and the mathematical models of torque and suspending force are verified, then the magnetic field characteristics of the new DSBSRM is analyzed, the important parameters influence of the magnetic field characteristics is analyzed. Finally, the new DSBSRM is compared with the 16-phase BSRM, the simulation results show that the torque output of the new DSBSRM is about 100% larger than that of the 16-phase BSRM, the increase percentage of suspending force varies with the change of current, but the output of suspending force is always larger than that of the 16-phase BSRM. Therefore, with the improvement of output performance, it can better cope with various workplaces.

Modeling and Analysis of Radial Levitation and Axial Reluctance Force for Four Degree of Freedom Bearingless Switched Reluctance Motor

For traditional 12/8 bearingless switched reluctance motors (BSRMs), the coupling between torque and levitation increases the complexity of control. For the turbomachinery application, 2 degrees of freedom (DOF) BSRMs stabilized by extra 3-DOF active magnetic bearings are required. In this article, an improved BSRM with 4 rotor poles and 12 stator poles is proposed to realize 4-DOF radial levitation, and the torque dead zone is compensated because that two rotors and these poles are assemble with 15 mechanical degree shifted. The decoupling of torque and radial levitation is realized simultaneously. Moreover, the operation principle of axial reluctance force is analyzed for passive levitation in the axial direction. Various experiments were completed to verify the performance of the proposed BSRM, and the prototype achieved stable levitation of the rotor in 10 000 r/min.

Global Sliding-Mode Suspension Control of Bearingless Switched Reluctance Motor under Eccentric Faults to Increase Reliability of Motor

Bearingless motor development is a substitute for magnetic bearing motors owing to several benefits, such as nominal repairs, compactness, lower cost, and no need for high-power amplifiers. Compared to conventional motors, rotor levitation and its steady control is an additional duty in bearingless switched reluctance motors when starting. For high-speed applications, the use of simple proportional integral derivative and fuzzy control schemes are not in effect in suspension control of the rotor owing to inherent parameter variations and external suspension loads. In this paper, a new robust global sliding-mode controller is suggested to control rotor displacements and their positions to ensure fewer eccentric rotor displacements when a bearingless switched reluctance motor is subjected to different parameter variations and loads. Extra exponential fast-decaying nonlinear functions and rotor-tracking error functions have been used in the modeling of the global sliding-mode switching surface. Simulation studies have been conducted under different testing conditions. From the results, it is shown that rotor displacements and suspension forces in X and Y directions are robust and stable. Owing to the proposed control action of the suspension phase currents, the rotor always comes back rapidly to the center position under any uncertainty.

An Improved Direct Torque Control for a Single-Winding Bearingless Switched Reluctance Motor

The direct torque control (DTC) and direct force control (DFC) method were introduced to reduce the torque and levitation force ripple in single-winding bearingless switched reluctance motors (SWBSRMs). However, it still has some disadvantages. Firstly, the flux-linkage control is not suitable for the DTC method in SWBSRMs. On the one hand, it can increase the torque ripple. On the other hand, the RMS current can be increased and then the torque-ampere ratio is decreased. Secondly, the vectors selection is also unreasonable, which can increase the torque ripple further. In order to solve these problems, an improved control method based on DTC and DFC method for SWBSRMs is proposed in this paper, which can obtain high torque-ampere ratio and low torque ripple simultaneously. In the proposed method, the flux-linkage loop control is not needed and the space voltage vector table is improved. The experimental results show that the torque ripple is reduced by 66.7%, the torque-ampere ratio is increased by 200% and the switching times in one electrical period are reduced by 47.3%.

A Novel Sensorless Approach for Speed and Displacement Control of Bearingless Switched Reluctance Motor

The bearingless concept is a plausible alternative to the magnetic bearing drives. It provides numerous advantages like minimal maintenance, low cost, compactness and no requirement of high-performance power amplifiers. Controlling the rotor position and its displacements under parameter variations during acceleration and deceleration phases was not effective with the use of conventional controllers like proportional–integral–derivative (PID) and fuzzy-type controllers. Hence, to get the robust and stable operation of a bearingless switched reluctance motor (BSRM), a new robust dynamic sliding mode controller has been proposed in this paper, along with a sensorless operation using a sliding ode observer. The rotor displacement tracking error functions and speed tracking error functions are used in the designing of both proposed methods of the sliding mode switching functions. To get a healthy and stable operation of the BSRM, the proposed controller’s tasks are divided into three steps. As a first step, the displaced rotor in any one of the four quadrants in the air gap has to pull back to the centre position successfully. The second step is to run the motor at a rated speed by exciting torque phase currents, and finally, the third step is to maintain the stable and robust operation of the BSRM even under the application of different loads and changes of the motor parameters. Simulation studies were conducted and analysed under different testing conditions. The suspension forces, rotor displacements, are robust and stable, and the rotor is pulled back quickly to the centre position due to the proposed controller’s actions. The improved performance characteristics of the dynamic sliding mode controller (DSMC)-based sliding mode observer (SMO) was compared with the conventional sliding mode controller (SMC)-based SMO.

Controllability of radial displacement in bearingless switched reluctance motor using bridge configured winding

Controllability of radial displacement in bearingless switched reluctance motor using bridge configured winding

Design and Analysis of a 16/6 Bearingless Switched Reluctance Motor with Segment Hybrid Rotor Teeth

In this article, a 16/6 bearingless switched reluctance motor (BSRM) with segment hybrid rotor teeth has been presented. To realize the decoupling control of torque and suspension force, the rotor teeth were divided into three torque teeth and three suspension teeth, and both of them are embedded in support part. First, both torque and suspension force are generated by short‐circuit excitation, the flux linkage coupling between torque windings and suspension windings was eliminated, and the separate control of torque and suspension force was achieved. Then, by increasing the pole arc of suspension teeth, the inductance of suspension windings is kept constant, which eliminates the influence on the output torque when adjusting suspension force. Finally, the coupling degree is further reduced by using nonmagnetic material as the supporting part. In addition, to achieve a greater output torque, the torque teeth are processed into U‐shape and optimized the pole arc of stator teeth and rotor teeth. The characteristics of inductance, flux linkage, and output torque are analyzed by the finite‐element method, and the results show that the proposed structure basically achieves the decoupling control of torque and suspension force. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Novel Bearingless Switched Reluctance Motor With Wide Flat Inductance Region to Simplify the Control of Torque and Levitation Force

In conventional 12/8 bearingless switched reluctance motors (BSRMs), the generation and control of torque and levitation forces are always coupled and interacted, which increases the complexity of the current control algorithm. In this paper, a novel BSRM with 12 stator poles and 4 rotor poles is proposed to simplify the control of torque and levitation, which has wide flat inductance region. Through allocating the generation of torque and levitation forces to different inductance regions of each phase, the levitation control can be similar as that of magnetic bearings, and the torque control can adopt the methods of conventional switched reluctance motors, e.g. current chopping control and angle position control. Accordingly, the current control algorithm of proposed BSRM becomes very easy and flexible. Extensive experiments were completed to verify the demonstrated performance of proposed motor.

Torque and controllable radial force production in a single winding bearingless switched reluctance motor with a speed controlled drive operation

Torque and controllable radial force production in a single winding bearingless switched reluctance motor with a speed controlled drive operation

Direct Displacement Control for Single-Winding Bearingless Switched Reluctance Motor

Although the conventional control strategy of Bearingless Switched Reluctance Motors (BSRMs) can realize stable suspension of the motor shaft, it still has disadvantages such as relying on the model calculation, strong coupling between torque and displacement, and poor anti-interference ability. In order to solve these problems, this paper studies a direct displacement control (DDC) strategy for single-winding BSRMs (SWBSRMs). This strategy draws on the control idea of magnetic bearings, and realizes the stable suspension of BSRMs on the premise of separating from the mathematical model online calculation. At the same time, the strategy realizes the decoupling of torque and suspension displacement, and has good anti-disturbance. Finally, experimental results show that compared with the conventional control strategy and DTC and DFC method, the DDC strategy reduces the execution time of the algorithm by 36.6% and 41.2% during steady-state; reduces the speed-up time by 60% and 23% during dynamic conditions; and reduces the speed-down time by 20% and 86.6%.

Rotor vibration control of hybrid pole bearingless switched reluctance motor with C-dump converter

Rotor vibration control during start up, acceleration and deceleration phases is one of the key problems besides stable levitation, in high-speed applications of bearingless switched reluctance motor (BSRM). In this paper, an effective intelligent sliding mode controller is proposed for suppressing the rotor vibration due to residual unbalance and external disturbance during levitation and motoring phases. The parameters of time-varying sliding surface for avoiding high control gains and chattering are adjusted integrating the sliding mode control (SMC) and features of fuzzy logic control. The experimental studies conducted on a prototype BSRM system confirm that the application of fuzzy SMC guarantees the robust performance with less chattering under model uncertainties and unknown external disturbances compared to classical sliding mode controller.

Rotor vibration control of hybrid pole bearingless switched reluctance motor with C-dump converter

Rotor vibration control of hybrid pole bearingless switched reluctance motor with C-dump converter

Full‐period suspension force accurate modelling for a novel bearingless switched reluctance motor

In the traditional bearingless switched reluctance motor (BSRM) system, the electromagnetic coupling between the torque system and suspension system is unavoidable. In this Letter, the present BSRM has the advantages of electromagnetic decouple with independent torque-suspension magnetic circuit design. However, the further in-depth study shows that the BSRM has an obvious suspension force fluctuation according to its asymmetry structure. Thus, it is necessary to build an accurate suspension force mathematical model considering commutation ripple. In this frame, a magnetic field segmentation method is proposed and the accurate suspension force model is built with Maxwell stress method and its reliability and precision are verified, modified based on finite element analysis.

Design Consideration and Characteristic Investigation of Modular Permanent Magnet Bearingless Switched Reluctance Motor

In order to increase structure compactness, critical rotor speed, and output torque of existing 12/12 bearingless switched reluctance motor (BSRM) with axial-biased permanent magnet, an improved modular permanent magnet BSRM is comprehensively investigated. First, basic structure and operation principle for torque and suspending force are briefly introduced. Second, magnetic design, including torque and suspending force, is taken into account. In addition, basic size estimation, self-starting capability, maximum suspending force, and selection of secondary air-gap are comprehensively considered in design. Third, several characteristics, such as torque, suspending force, etc., are deeply analyzed. Finally, a prototype motor is manufactured based on the above-mentioned analysis and design method. And the implemented experiment results show that the improved structure has good performance.

Multi-Physics Multi-Objective Optimal Design of Bearingless Switched Reluctance Motor Based on Finite-Element Method

The bearingless switched reluctance motor (BSRM) integrates the switched reluctance motor (SRM) with the magnetic bearings, which avoids mechanical bearings-loss and makes it promising in high-speed applications. In this paper, a comprehensive framework for the multi-physics multi-objective optimal design of BSRMs based on finite-element method (FEM) is proposed. At first, the 2-D electromagnetic model of a fabricated initial design prototype is built and solved by the open-source FEM software, Elmer. The iron loss model in Elmer based on the Fourier series is modified by a transient iron loss model with less computation time. Besides, a simplified lumped-parameter (LP) thermal model of the BSRM is applied to estimate the temperature rise of BSRM in the steady state. Then, the comprehensive framework for the multi-physics multi-objective optimal design of BSRMs based on FEM is proposed. The objectives, constraints, and decision variables for optimization are determined. The multi-objective genetic particle swarm optimizer is utilized to obtain the Pareto front of optimization. The electromagnetic performance of the final optimal design is compared with the initial design. Comparison results show that the average electromagnetic torque and the efficiency are significantly enhanced.

Design and Analysis of a Novel Bearingless Segmented Switched Reluctance Motor

A novel bearingless segmented switched reluctance motor (BSSRM) is proposed in this paper to solve the coupling problem of the traditional bearingless switched reluctance motor (BSRM). Different from traditional BSRMs, the proposed BSSRM adopts the double stator and segmented rotor structure, thereby making the motor operate in short flux paths and the magnetic flux path isolated between torque and suspension system. On the basis of introducing the structure and working principle of the BSSRM, the mathematical model of torque and suspension force is deduced. The 2D finite element simulation model is established by the Ansoft software. The influence of structural parameters on torque and suspension system is analyzed, and its electromagnetic characteristic and decoupling characteristic are analyzed. Compared with the double stator bearingless switched reluctance motor (DSBSRM), the BSSRM not only improves the torque and suspension output but also weakens the coupling between torque and suspension system. Finally, the simulation results verify the effectiveness of the BSSRM.