Bearingless Permanent Magnet Research Articles

Vibration Compensation Control of BPMSM With Dead-Time Effect Based on Adaptive Neural Network Band-Pass Filter

In order to solve the problem of rotor vibration for the bearingless permanent magnet synchronous motor, a vibration compensation control method based on adaptive neural network band-pass filter (ANNBPF) is proposed. First, the mechanism of rotor vibration is obtained by theoretical analysis. Second, the ANNBPF is used to extract the components related to the frequency of the unbalanced vibration and the dead-time (DT) vibration to realize the vibration compensation control. Additionally, the DT effect is compensated by detecting the current polarity to improve the compensation effect. Finally, a vibration compensation control system based on ANNBPF and current polarity detection is constructed.

Optimization Design of Unequal Amplitude Modulated Poles for the Bearingless PMSM

The structural parameters of an equal amplitude modulated magnetic pole is limited by the length of the air-gap. When the modulation ratio or carrier ratio is small, the spacing of permanent magnets is too large, which will lead to a worse cogging effect, and then the torque optimization effect is not satisfying. In order to improve the operation stability of a bearingless permanent magnet synchronous motor (bearingless PMSM), an unequal amplitude modulated magnetic pole structure is proposed according to the principle of magnetic pole modulation. The Taguchi method is used to optimize the structural parameters of the unequal amplitude modulated magnetic pole with the goal of reducing the torque and suspension force fluctuation. Three kinds of magnetic pole structures, named the whole magnetic pole, the equal amplitude modulated magnetic pole and the unequal amplitude modulated magnetic pole are compared and verified. The results show that the proposed structure of the unequal amplitude modulated magnetic pole can effectively further decrease the torque and suspension force fluctuations under the premise of the output capacity of the motor being unchanged, which improves the performance of the bearingless PMSM.

Three-Coil Combined Winding Configuration for a 2-DOF Actively Controlled Bearingless Permanent Magnet Motor

This study describes a simple combined winding configuration for a two-degrees-of-freedom (DOF) controlled bearingless motor with a six-slot/six-pole permanent magnet (PM) structure. This bearingless PM motor has only three concentrated coils that are wound alternately on six teeth of the stator and employs only one three-phase inverter for both the two-DOF radial magnetic suspension and single-phase motor drive. Theoretical calculation and finite element method (FEM) analysis demonstrated that the proposed three-coil combined winding configuration generates a four-pole rotating field and six-pole alternating field for generating radial suspension force and torque, respectively. To verify the proposed configuration, we built and tested an outer rotor bearingless PM motor with a diameter of 58 mm and a height of 5 mm. The rotor was successfully levitated and driven up to 7500 rpm. The calculated and measured results were compared for both the proposed combined winding configuration and the previously developed separated winding configuration. The measured motor efficiency of the prototype with the combined winding at 5000 rpm with 20 mNm output is improved by 5% due to the copper loss reduction when compared to that with the separated winding.

Eddy Current Influence on the Control Behavior of Bearingless PM Synchronous Machines

The influence of the additional air gap field in bearingless permanent magnet (PM) synchronous machines, caused by rotor eddy currents, leads to a decrease in bearing force amplitude and to a spatial shift of the bearing force vector with respect to the demanded force direction. Together with the gyroscopic effect and the influence between torque and bearing force generation, this effect may endanger the position control system stability. For a 1-kW/60 000-min <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-1}$</tex-math></inline-formula> prototype and a 40-kW/40 000-min <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-1}$</tex-math></inline-formula> machine, this is exemplified in order to derive a limit for rotor eddy currents in bearingless PM synchronous machines of different power classes. A machine with low gyroscopic coupling allows for a stronger eddy current effect and torque generation influence, independent of the machine size. The maximum admissible spatial shift of the bearing force vector due to rotor eddy currents depends on the gyroscopic rotor properties and the machine utilization. From measurements on a prototype machine, a rough limit is derived.

Development of Axial-Flux Single-Drive Bearingless Motor With One-Axis Active Positioning

This study proposes a novel axial-flux bearingless permanent magnet motor with one-axis active positioning. This bearingless motor consists of an axial-flux surface permanent magnet motor with coreless coils and a repulsive permanent magnet coupling located at its center. Therefore, it has a single three-phase winding and needs only one three-phase inverter for both rotation and magnetic suspension; it is, thus, referred to as a single-drive bearingless motor. The axial position of the rotor is actively controlled, whereas the radial and tilting motions are passively stabilized. The suspension force and torque are regulated by the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis currents, respectively. The structure of the proposed axial-flux single-drive bearingless motor is presented, and its torque and suspension force are obtained by both theoretical derivation and numerical modeling (using the finite-element method). A prototype machine is fabricated, and the obtained experimental results are presented and discussed.

Multiobjective Optimization Design of Outer Rotor Coreless Bearingless Permanent Magnet Synchronous Motor

The outer rotor coreless bearingless permanent magnet synchronous motor (ORCBPMSM) is suitable for flywheel energy storage systems because of the advantages of no core loss and high efficiency. To improve the output torque and suspension forces of the motor, a Taguchi-response surface method (T-RSM) is proposed to conduct multiobjective optimization design of the motor. First, the basic structure and working principle of the proposed motor are expounded, and the basic design parameters of the motor are given. Then, the orthogonal matrix is established according to the number of factor levels, and the finite element analyze (FEA) is conducted to obtain each set of test results. After that, the sensitivity analysis is conducted and the best combination of variables can be achieved. Aiming at improving the accuracy of the Taguchi method, the fitting functions are established among the targets and conflicting variables, and the optimal solution is obtained by RSM. Finally, the optimal motor is manufactured, and the performance of the motor is verified. The experimental results show that stable operation can be obtained and the operating performance of the proposed motor is improved after optimization.

A novel consequent‐pole bearingless PMSM with integrated winding for flywheel energy storage

Generating torque and suspension force with one set of windings at the same time can increase the copper space factor and improve the torque output capacity. This structure has a unique application advantage for bearingless motors used in onboard flywheel energy storage. A consequent-pole bearingless permanent magnet synchronous motor (PMSM) with integrated winding is designed and researched. Regulating suspension current has minimal effect on the torque performance of the motor in this design. The effectiveness and feasibility of this design are verified through a finite element calculation. Its advantages and application scope are discussed.

Design Method of Bearingless Permanent Magnet Slice Motor for Maglev Centrifugal Pump Based on Performance Metric Cluster

Different from ordinary AC machines, the design of a bearingless permanent magnet slice motor (BPMSM) considers not only the torque performance, but also the passive and active suspension properties. In addition, BPMSM for a maglev centrifugal pump has unique design characteristics due to the integration of the pump head and sensors. This paper investigates evaluation and design techniques based on a cluster of performance metrics targeting on developing BPMSM for a maglev centrifugal pump. The cluster of performance metrics for BPMSM, including passive stiffness (kz, kz/kx, kz/ky, kα, and kβ) and active factors (ki and cm), is first proposed and an evaluation function fiSi,Li is constructed. Then, practical configurations of BPMSM for a maglev centrifugal pump are summarized. Based on the cluster of performance metrics, the finite-element method (FEM) is used to explore the impact of the rotor magnetization (sinusoidal, diametric, and radial method) on motor properties. Subsequently, the complete design process of BPMSM for a maglev centrifugal pump is introduced and key differences (including three crucial geometric parameters: ratio of rotor height to diameter λ, magnetic gap length δ, and stator tooth width αst) in the design considerations between BPMSM and general bearingless motors are analyzed. Finally, the upgraded performance (kz, kα, kβ, ki, cm, and fiSi,Li increased by about 29%, 38%, 33%, 31%, 21%, and 15%, respectively) of the designed candidate is obtained, which verifies the effectiveness of the proposed design methods.

Research on the Modelling of a Single-winding Bearingless Permanent Magnet Brushless DC Motor

This paper studies the radial suspension force mathematical model of a single-winding bearingless permanent magnet brushless DC motor, which provides a theoretical basis for the precise control of a single-winding motor. First, the physical structure of the single-winding BL-BLDC motor and the principle of radial suspension force generation are introduced. Then, the equivalent magnetic circuit method is used to establish the electromagnetic relationship inside the motor and the virtual displacement method is used to derive and calculate the mathematical model of the radial suspension force. The radial suspension force of the motor is composed of the force generated by the suspension force winding and the unbalanced magnetic pull force generated by the motor rotor deviating from the center position. Finally, the finite element analysis software is used to model and simulate the single-winding motor to analyze the change of the suspension force amplitude under different currents and the influence of different eccentric displacements on the unbalanced magnetic tension of the motor. The results show that the error between the simulation results obtained by the FEA and the theoretical calculation results of the mathematical model is small, which verifies the correctness of the radial suspension force mathematical model of the single-winding BL-BLDC motor.

Multi-Structural Optimization of Bearingless Permanent Magnet Slice Motor Based on Virtual Prototype in Ansoft Maxwell

As a preliminary study for bearingless permanent magnet slice motor (BPMSM) development, an effective means for BPMSM mechanical structure optimization is proposed here by developing a virtual prototype based on Ansoft Maxwell to realize overall performance improvements. First, the sensitivity evaluation index of the candidate mechanical structural parameters for individual BPMSM performance is constructed for selection. Orthogonal tests are performed to determine the dominant mechanical structural parameters to be optimized by utilizing monitored data based on Ansoft Maxwell. A linear regression model of the mechanical structural parameters for specific performances is obtained by utilizing the gradient descent method. Then, a multi-structural optimization regression model of the selected dominant mechanical structural parameters for overall performance is established using an analytic hierarchy process and solved using a genetic algorithm. The simulation results show that the performance of the optimized BPMSM has been comprehensively improved. Specifically, the passive axial stiffness, passive tilting stiffness, force-current coefficient, and motor efficiency increased by 56.4%, 71.3%, 19.6%, and 8.7%, respectively.

Sensorless Control of Bearingless Permanent Magnet Synchronous Motor Based on LS-SVM Inverse System

In order to solve the problems of low integration, low reliability, and high cost caused by mechanical sensors used in bearingless permanent magnet synchronous motor (BPMSM) control systems, a novel speed and displacement sensorless control method using a least-squares support vector machine (LS-SVM) left inverse system is proposed in this paper. Firstly, the suspension force generation principle of the BPMSM is introduced, and the mathematical model of the BPMSM is derived. Secondly, the observation principle of the left inverse system is explained, and the left reversibility of the established speed and displacement subsystem is proved. Thirdly, the left inverse systems of the speed and displacement subsystems are constructed by using the LS-SVM, and the complete speed and displacement sensorless control system is constructed. Finally, the simulations and experiments of the proposed method are performed. The research results demonstrate that the proposed observation method can identify the speed and displacement quickly and accurately, and the sensorless control method can realize the stable operation of the BPMSM without speed and displacement sensors.

A new type of sinusoidal suspension winding Consequent-pole Bearingless Permanent Magnet Synchronous Motor

The existence of the harmonic of the suspension magnetomotive force is a key factor affecting the precision of the suspension force of the Consequent-pole Bearingless Permanent Magnet Synchronous Motor, and the coupling of motor’s suspension force in different degrees of freedom is obvious. Aiming at the improvement of the motor’s suspension performance, a 48 slot 8-pole consequent-pole bearingless permanent magnet synchronous motor with low harmonic suspension sinusoidal winding is designed in this paper. The effects of two kinds of sinusoidal suspension windings, 90° type and 120° type, on the optimization of suspension performance are analyzed, and the finite element analysis was used to verify that these two low-harmonic suspension winding structures, especially the 120° type, can effectively suppress the motor’s suspension magnetomotive force harmonics, improve the motor’s suspension force accuracy, and at the same time make the coupling problem between different suspension degrees of freedom of consequent-pole bearingless permanent magnet synchronous motor improved obviously.

Grey Wolf Optimization Algorithm Based State Feedback Control for a Bearingless Permanent Magnet Synchronous Machine

In this article, an optimal control strategy for a bearingless permanent magnet synchronous machine (BPMSM) drive is proposed. The state feedback control (SFC) based on the grey wolf optimization (GWO) algorithm is applied. As for the BPMSM system, coupling and nonlinearity exist, which hinders the SFC. Hence, the linearization of the BPMSM mathematical model is implemented first. Second, the discretized state model with the augmented integrals of the displacement error and the angular speed error is obtained. Then, the weighting matrices K <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> are obtained by employing the GWO algorithm. Finally, simulations and experiments are carried out to verify the effectiveness of the proposed method. Comparisons between the controllers with and without the penalty term are conducted. Meanwhile, the proportional-integral (PI) controllers based on the genetic algorithm and the proposed one are compared as well. The results show the superiority of the proposed method reflecting in faster response and no overshoot compared with the PI controllers.

Rotor radial displacement sensorless control of bearingless permanent magnet synchronous motor based on MRAS and suspension force compensation

Limitations exist on the displacement sensors employed in a bearingless permanent magnet synchronous motor (BPMSM). They lead to the increase in cost, size and complexity of the motor. Apart from that, the measurement errors are sensitive to the temperature and the electromagnetic noise. In order to resolve these problems, a novel rotor radial displacement sensorless control method of the BPMSM is proposed. In this paper, the operation principle and mathematical model of the BPMSM are introduced firstly. Secondly, the rotor radial displacement self-sensing method using the model reference adaptive system is designed. Thirdly, a direct control strategy of rotor eccentric displacement with suspension force compensation is proposed to promote the property of the displacement sensorless control system. Finally, a torque control subsystem based on the id=0 control scheme and a displacement control subsystem based on the proposed displacement self-sensing method and the suspension force control method are constructed. The related simulations and experiments are carried out. According to the research results, the rotor radial displacements of the BPMSM are effectively estimated and the stable suspension of the BPMSM rotor without displacement sensors is achieved.

Direct Control of Bearingless Permanent Magnet Slice Motor Based on Active Disturbance Rejection Control

Aiming at the problem that the suspension force under disturbance of the permanent magnet slice rotor is difficult to be accurately detected, a new displacement controller based on the active disturbance rejection control is proposed. Firstly, the mathematic models of torque and suspension forces of the bearingless permanent magnet slice motor (BPMSM) are deduced. Secondly, the active disturbance rejection (ADR) controller is constructed. Thirdly, the BPMSM direct control system based on the ADR controller is built and the simulation is carried out, the correctness of the mathematic model and the control algorithm are verified. Finally, the displacement controller is used for a 4 kW prototype. Compared with the traditional PI controller, the floating stability time and the disturbed recovery time of the slice rotor are both decreased, the vibration displacement of rotor in stable state is reduced by 44%.

Multi-Objective Optimization Design of Bearingless Permanent Magnet Synchronous Generator

In order to realize the design objectives of high power generation performance and stable suspension capability, a multi-objective optimization method based on a response surface (RS) model and an improved multi-objective particle swarm optimization (MOPSO) algorithm is proposed and utilized to the multi-objective optimization design of a bearingless permanent magnet synchronous generator (BPMSG). Firstly, the operating principle and the mathematical model of the BPMSG are introduced. Secondly, the design variables and the design objectives are determined and the design space is reduced by the sensitivity analysis. Thirdly, the RS models of design objectives are constructed and the improved MOPSO algorithm is applied to get the Pareto optimal sets. Finally, the initial generator and the optimal generator are compared using the finite element analysis software. Compared with the initial generator, the average suspension force of the optimal generator is increased by 21% and the suspension force ripple is decreased by 52%.

Active disturbance rejection control of 5-degree-of-freedom bearingless permanent magnet synchronous motor based on fuzzy neural network inverse system

To realize the high performance operation of the 5-degree-of-freedom bearingless permanent magnet synchronous motor (5-DOF-BPMSM), a novel decoupling control strategy combining fuzzy neural network inverse system (FNNIS) with active disturbance rejection control (ADRC) is proposed. Firstly, fuzzy neural network (FNN) is employed to approach the inverse system of the 5-DOF-BPMSM. By connecting the obtained inverse system with the original system, six independent pseudo-linear subsystems are constructed. Then, considering the influence of parametric variations and external disturbances in the process of operation, the ADRC theory is employed to design additional closed-loop controllers to ensure the stability of the pseudo-linear subsystems. Finally, comparative simulation and experimental results indicate that the proposed control strategy can achieve better control performance.

Decoupling control of bearingless PMSM with LSSVM inverse system and IMC

In this paper, a novel decoupling control scheme combining least squares support vector machines (LSSVM) inverse models and 2-degree-of-freedom (DOF) internal model controllers (IMC) is employed in the decoupling control system of the bearingless permanent magnet synchronous motor (BPMSM). This scheme can be used to enhance the control properties of high-precision, fast-response, and strong-robustness for the BPMSM system, and effectively eliminate the nonlinear and coupling influence. It introduces LSSVM inverse models into the original BPMSM system to constitute a decoupled pseudo-linear system. In addition, the particle swarm optimization algorithm (PSO) is used to optimize parameters of the LSSVM, which improves its fitting ability and prediction accuracy. What is more, the internal model control scheme is used to design additional closed-loop controllers, thereby improving the robustness of the entire control system. Therefore, this scheme successfully combines the advantages of the LSSVM inverse models and the internal model controller. It can enhance the stability and the static as well as dynamic properties of the whole BPMSM system while independently adjusting the tracking and interference rejection performances. The effectiveness of the proposed scheme has been verified by simulation results at various operations.

Performance Benchmarking of a Novel Magnet-Free Bearingless Synchronous Reluctance Slice Motor

This paper presents a novel bearingless synchronous reluctance slice motor topology that contains no permanent magnets. The rotor with two iron poles and flux barriers is levitated and rotated through a stator winding system with six coils wired as two three-phase systems. A constant rotor-oriented magnetization current is applied to generate a magnetic bias flux. The system can be controlled similar to a bearingless permanent magnet synchronous slice motor and provides passive stabilization of axial and tilting movements of the rotor. The motor topology is discussed in detail and a prototype implementation is presented. Its performance with regard to passive properties, achievable torque, controllability, and wide air gap suitability is benchmarked against two other designs that contain permanent magnets either in the rotor or the stator. A loss analysis of all topologies is performed and suitable application areas are identified. The proposed design provides an interesting alternative to existing bearingless slice motor topologies in applications that require high rotational speeds, high process or ambient temperatures, or a disposable low-cost rotor with short exchange intervals.

Design and Analysis of a Bearingless Permanent-Magnet Motor for Axial Blood Pump Applications

Because of their high power density and compact size, permanent-magnet (PM) motors have been commonly used to drive rotary blood pumps (RBPs), which are focused on the treatment of end-stage heart failure or as the bridge to a heart transplant. In this paper, a bearingless PM motor has been proposed for axial blood pump applications. The finite-element method (FEM) is used to predict the electromagnetic characteristics of the designed motor with improved performance. Two topologies are investigated, namely the integral-slot and distributed-windings method and the fractional-slot and double-layer concentrated windings method. Both motors are analyzed and optimized. FEM reveals that, compared with the integral-slot motor, the fractional-slot motor offers significantly enhanced performance, including reduced cogging torque, improved back electromotive force (back EMF), and decreased magnetic flux leakage. Finally, hydraulic experiments have been conducted in a mock-circulation loop to validate the feasibility of the designed motor for an axial blood pump. The results show that the fractional-slot bearingless PM motor can drive the RBP to produce physiological blood flow with reasonable efficiency.