back-EMF Research Articles

Cold-Spray Additive Manufacturing of a Petal-Shaped Surface Permanent Magnet Traction Motor

Several applications require low torque pulsations as they can lead to mechanical vibrations and acoustic noise in the electric motor. Optimization of the rotor permanent magnet (PM) shape is one of the effective methods for reducing torque pulsations. Unfortunately, the low versatility of the magnet fabrication technologies limits the development of new motor geometries. Cold spray additive manufacturing can be used for shaping permanent magnets for the direct fabrication of motor parts without the need for additional assembly steps. This fabrication technique allows an increase in the design flexibility of electric machine geometries targeting improved performance. This paper investigates the performance of permanent magnet rotors fabricated using a cold spray additive manufacturing technique for radial flux surface permanent magnet synchronous machines (SPMSM). The permanent magnet rotors considered are conventional rectangular-shaped with unskewed magnets (Model A), skewed magnets (Model B), and sinusoidal-petal shaped magnets (Model C) along the axial direction. The magnitude of magnetization current pulse required to magnetize these rotors is calculated and an impulse magnetizer setup is designed for in-situ magnetization. The performance of the shaped cold sprayed permanent magnet rotors and their effects on back EMF, electromagnetic torque, and cogging torque are analyzed experimentally and comparisons are made between the different rotor designs.

Performance Improvement in a Linear Primary Permanent Magnet Vernier Machine by Modular Unit Shift Effect

This article investigates the effects of modular unit shift on the detent force and mutual to self-inductance ratio in the modular linear primary permanent magnet vernier (MLPPMV) machine. First, the winding connection and slot/pole combinations for the modular design is discussed. Then, the relationship of the phase shift and modular unit spacing is given. The operation principle of the MLPPMV machine is analyzed from the perspective of the air-gap field modulation theory. Moreover, the analytical expressions of the modular unit shift and phase shift angle for the MLPPMV machine are derived. Afterwards, the back EMFs, detent forces and inductances are comparatively analyzed. The investigation reveals that the reasonable modular unit shift has significance to improve the electromagnetic performances. Furthermore, the finite element method is adopted to evaluate. Finally, a prototype of MLPPMV machine is built. Experiments are carried out on a linear test bench, verifying the theoretical analysis.

Topology Optimization of Synchronous Reluctance Motors Considering the Optimal Current Reference in the Field-Weakening and Maximum-Torque-Per-Voltage Regions

The torque performance of the synchronous reluctance motors (SynRMs) is primarily determined by the geometric design and current control. The motor structure needs to be designed to yield the maximum output torque under the given current and voltage limitations. The current reference supplied to the stator coils also needs to be determined to maximize the output torque while suppressing the back electromotive force (EMF) to protect a power supply system. However, in the field of design optimization, it has been challenging to simultaneously consider the geometric design and current control due to their complicated relationships. To solve the aforementioned issue, this study proposes a new topology optimization that can cover the maximum-torque-per-ampere (MTPA), field weakening (FW), and maximum-torque-per-voltage (MTPV) controls under both the current and voltage limitations, thereby maximizing the output torque in an entire rotational speed range. To effectively investigate the coupling effects between the geometric design and current reference, this study proposes the design parameterization for the FW and MTPV operation by performing the electromagnetic finite element (FE) analysis and then expresses the optimal current reference in terms of design variables. At every iteration, the structural FE analysis is also performed under the design-dependent loads to obtain a structurally meaningful design. By doing so, both the optimal design and the corresponding optimal current reference can be simultaneously determined. The optimized SynRM is manufactured and experimentally validated to demonstrate the effectiveness of the proposed optimization framework.

Reduction of Torque Vibration in Integrated On-board Chargers Using Stator Windings of an IPMSM

This study proposed a control method to reduce the torque ripple vibration of an integrated on-board charger using the windings of an interior permanent magnet synchronous motor (IPMSM). During a battery-charging operation, stopping the motor results in noise, as well as damage to the motor and other components from the torque vibration caused by the charging current. In the proposed control method, the generated torque was estimated using a back-electromotive force table, and the phase current was controlled to eliminate the torque. The proposed method can suppress torque vibration, irrespective of the angle of the rotor in the IPMSM. The effectiveness of the proposed method was verified experimentally, with the torque vibration suppressed by 94% compared with that of the conventional control method.

Analysis of an Axial-Flux Slotted Limited-Angle Torque Motor with Quasi-Halbach Array for Torque Performance Improvement

Better torque performance and higher reliability have long been the focus of research for slotted limited-angle torque motors (LATMs), which are primarily used to position first-stage valves in electrohydraulic servosystems. This paper presents a high reliability axial-flux slotted LATM with quasi-Halbach array for torque performance improvement including constant torque range (CTR) and output torque. Firstly, the structure with two sets of windings and the operation principle of the proposed slotted LATM is analyzed. Secondly, a brief design procedure is presented, the structure selections of open slot and double-stator single-rotor (DSSR) interior rotor with surface mounted quasi-Halbach permanent magnet (PM) array are illustrated, and the geometric parameters are optimized to obtain the optimal design of the proposed slotted LATM. Then, 3-D finite-element method (FEM) is employed to compare the proposed slotted LATM with the conventional surface mounted PM slotted LATM in terms of cogging torque, no-load back EMF, and output torque, and the results show that the proposed LATM with quasi-Halbach array has a 10% improvement in output torque and a 25% improvement in CTR. Meanwhile, the flux linkages and torque performance of the two sets of windings under various conditions verify good magnetic isolation. Finally, prototypes of two different rotor types are manufactured and a series of experiments are performed to validate the analysis.

Sectional Modular Technology for Reducing Detent Force of Linear Unit in Linear-rotary Flux-switching Permanent-magnet Generator for Wind-wave Combined Energy Conversion

A linear-rotary flux-switching permanent magnet (FSPM) generator (LRFSPMG) is a potential candidate for a wind-wave combined energy conversion (WWCEC) system. The linear unit of the LRFSPMG is a tubular FSPM linear generator (TFSPMLG), which like other permanent magnet linear generators, has an inherent detent force problem. To alleviate this problem, a sectional modular technology scheme is investigated to reduce the detent force of the TFSPMLG. Firstly, the structure is briefly introduced and the detent force analyzed. Secondly, the sectional modular TFSPMLGs are presented and their feasibility verified with respect to the stator of the TFSPMLG being split into two and three sections, forming Modulars I and II, respectively. After that, the detent force suppression principle, and the effects that the sectional modular structures exert on the detent force are analyzed. According to the analysis results, two methods are presented to suppress the detent force: one is to suppress the magnetic coupling effect; the other is to reduce the remaining harmonics. Finally, the three TFSPMLGs, including the initial TFSPMLG, Modular I, and Modular II, are comparatively analyzed by finite-element analysis (FEA). The results show that both the detent forces are greatly reduced without sacrificing the back electromotive force (EMF) and average electromagnetic force, thereby proving the effectiveness of the TFSPMLG with a sectional modular structure.

Demagnetization Modeling and Analysis for a Six-Phase Surface-Mounted Field-Modulated Permanent-Magnet Machine Based on Equivalent Magnetic Network

Demagnetization Modeling and Analysis for a Six-Phase Surface-Mounted Field-Modulated Permanent-Magnet Machine Based on Equivalent Magnetic Network

An ampere‐second‐vector pulse width modulation technique and fault‐tolerant control for CSI11 fed five‐phase permanent magnet synchronous motor with multiple harmonic electromotive forces

AbstractWhen dealing with safety‐critical applications that involve multiphase permanent magnet synchronous motors (PMSMs), the current source inverter (CSI) is a superior choice compared with the voltage source inverter. The conventional technique of pulse width modulation (PWM) presents a challenge for CSI, particularly during faults. The fault‐tolerant control of multiphase PMSMs fed by CSIs has not been well investigated, particularly in situations involving double‐phase open‐circuit faults. Furthermore, fault‐tolerant control becomes more complex when the multiphase PMSM includes harmonic back electromotive forces (EMFs). To deal with these issues, an ampere‐second (AS) vector PWM technique is developed for a five‐phase PMSM powered by CSI11. The modulation ratio of the proposed PWM is identical to that of space vector PWM. The proposed method, however, is easier to implement. A fault‐tolerant control method using AS‐vector is proposed for single‐phase, adjacent double‐phase, and non‐adjacent double‐phase open‐circuit faults. Additionally, a method is developed to suppress the torque ripple that results from harmonic back‐EMFs during fault conditions. Compared without the torque ripple suppression method, during the speed rising, the proposed method can reduce torque ripple to 16.7%, 54.5%, and 37.5%, respectively. The experiments have confirmed the effectiveness of the proposed PWM technique and fault‐tolerant control method.

Adaptive Neuro-Fuzzy Sliding Mode Controller (ANF-SMC) to control speed, electromagnetic torque (EMT), Stator Current, and Back EMF using PMBLDCmotor(PMBLDCM) in Electric Propulsion of Electric Vehicles

Adaptive Neuro-Fuzzy Sliding Mode Controller (ANF-SMC) to control speed, electromagnetic torque (EMT), Stator Current, and Back EMF using PMBLDCmotor(PMBLDCM) in Electric Propulsion of Electric Vehicles

Improved Position Observer Using Adaptive Training Control-Based Filter for Interior Permanent Magnet Synchronous Motor Drives

Rotor position is the key information to achieve superior performance for sensorless control of interior permanent magnet synchronous motor (IPMSM). Nevertheless, the back electromotive force (EMF) model-based position estimation suffers from severe contamination from the fifth and seventh harmonics resulting from inverter nonlinearity and flux spatial harmonics. Therefore, an adaptive training control-based adaptive filter combined with a sliding-mode observer (SMO) is presented for harmonics rejection in the estimated back-EMF, and thus improving the rotor position estimation performance. This method, based on the steepest descent algorithm, is capable of self-adjusting harmonic coefficients to obtain the fundamental component online under various frequency conditions adaptively. Additionally, the proposed method has simpler structure and less calculation burden since its reference signal is self-generated without external injection compared to the conventional method. The effectiveness is verified by experiments at a 1.5-kW IPMSM drive platform.

Position Sensorless Drive With Online Parameters Estimation for Magnetic Suspension Centrifugal Compressor

With the advantages of a high power-to-weight ratio and oil-free bearings, a magnetically Suspension centrifugal compressor (MSCC) equipped with active magnetic bearings (AMB) operates more efficiently than traditional mechanical compressors over a wide speed range by precisely controlling a high-speed permanent-magnet synchronous motor (PMSM). However, owing to the harsh working environment, the motor parameters, including the resistor, inductance and flux linkage, vary significantly. This degrades the rotor position observer performance, which is crucial for controlling a high-speed PMSM. Hence, this article proposes an improved sensorless control method combined with novel motor parameter identification. First, an improved position sliding mode observer using a novel super-twisting algorithm (STA) is designed to achieve higher precision and better transient performance. Second, the influence of parameter mismatch is analyzed. To overcome the problems of rank deficiency and system matrix uncertainties, a novel identification strategy based on recursive total least squares excitatory and inhibitory learning (RTLS EXIN) is developed to identify inductance and resistance in two-time scales. Meanwhile, the back electromotive force (EMF) in static coordinates is employed to estimate the flux linkage. Third, the results are adopted to update the control parameters immediately. Finally, the proposed method is tested on an MSCC prototype experimental platform, and the results verify its validity and feasibility.

Topology Optimization of the IPMSMs Considering Both the MTPA and FW Controls Under the Voltage and Current Limitations

This study proposes a novel topology optimization which can maximize the average torque of the interior permanent magnet synchronous motors (IPMSMs) in both the maximum torque per ampere (MTPA) and field weakening (FW) regions. In principle, the back electromotive force (EMF), which is proportional to a rotating speed, should be suppressed below the DC-link voltage to protect a power supply system. However, because the design and current reference of the IPMSM are coupled to affect the back EMF, it has been challenging to simultaneously determine the optimal design and current reference under such a voltage limitation. To solve the above issue, this study derives the design-dependent FW current reference in terms of the elementwise relative densities, which are set as design variables in topology optimization. In addition, the selection criterion between the MTPA and FW operations is proposed under the same design parametrization. After estimating the motor-design parameters, the proposed method simultaneously determines the optimal design and the corresponding current reference in both the MTPA and FW regions. The simulation and experimental results clearly demonstrate the validity of the proposed method.

Experimental investigation of a real-time singularity-based fault diagnosis method for five-phase PMSG-based tidal current applications

This paper presents a novel real-time singularity-based fault diagnosis method for tidal current applications, specifically utilizing a five-phase permanent magnet synchronous generator with trapezoidal back electromotive forces. The proposed method incorporates an innovative orthogonal signal generator through a second-order filter, enabling the extraction of detectable singularity signatures from phase current signals. The principle of the method is elucidated through step-by-step design procedures, outlining the indicator enhancement approach and adaptive thresholds employed for enhanced robustness and adaptability. Fault detection is performed based on the improved fault indicators and an adaptive threshold law, followed by immediate fault localization that is achieved via twice average operations of the phase currents. To demonstrate the effectiveness and efficiency of the proposed method, a comparative study is carried out with a classical mean current vector-based fault diagnosis method. A small-scale experimental platform emulating a tidal current application is established for a comprehensive evaluation of both methods. The experimental results highlight the superior fault diagnosis performance of the proposed method, particularly in detecting single and multiple open circuit faults in phases or switches, while exhibiting enhanced robustness against variations in torque and speed. The simplicity of implementation and rapid detection mechanism are principal merits for the proposed method.

Speed Sensorless Control Method of Synchronous Reluctance Motor Based on Resonant Kalman Filter

When estimating the active back electromotive force (AEMF) of synchronous reluctance motor (SynRM) at medium and high speed, the traditional Kalman Filter (KF) will produce large phase delay due to the low-pass filter characteristics. A novel speed sensorless control scheme of SynRM based on resonant Kalman filter (RKF) is proposed in this paper. Firstly, the AEMF observer based on KF is designed and the bandwidth performance is analyzed. To solve the phase delay problem caused by KF, a generalized integral resonance perturbation estimator (GIRPE) is introduced to the framework of KF and the proposed RKF is formed. The estimation error of AEMF is compensated through GIRPE in the current error feedback loop of KF observer. In this way, the high-precision position estimation at high speed range is obtained. Finally, an improved dynamic position compensator (IDPC) is proposed to enhance the position estimation performance under dynamic case. The effectiveness of proposed scheme is validated at a 1.5kW SynRM drive, and the computational burden of the proposed method is assessed quantitatively.

Sensorless Control of Interior Permanent Magnet Synchronous Motor Drives Considering Resistance and Permanent Magnet Flux Linkage Variation

Extended sliding mode disturbance observer-based current observer for interior permanent magnet synchronous motors (IPMSM) is an efficient method where the estimated dq-axis disturbances are linearly dependent on the position estimation error. Thus, this paper proposed a robust speed-position identification strategy using the estimated disturbances. First, an analysis of the estimated disturbances concerning parameter variation, position estimation error and the effect on the sensorless control performance is given. Then, a combined method that uses the dq-axis disturbances is proposed for speed-position identification. The proposed method is robust against stator resistance variation without estimating the stator resistance. However, the flux linkage variation effect sustains per the external load. Therefore, the permanent flux linkage variation electromotive force (EMF) compensator is included. The compensator is activated in the medium to the high-speed range while deactivated in the low-speed area. Thus, the advantage of the combined method for the low-speed area against resistance variation is kept. Various hardware-in-the-loop experimental studies and comparative analysis show that the proposed method with a permanent flux linkage variation back EMF compensator achieved an excellent sensorless control performance for IPMSM.

Closed-loop control of BLDC motor using Hall effect sensors

Due to its key advantages of top performance, strong torque, and simple volume, brushless direct current (BLDC) motors are now extensively employed in a variety of industrial sectors, including the automotive industry, robotics, and electrical vehicles. Yet, in some circumstances, it can be challenging to use speed control techniques for specific devices. The major goal of this work is to use a proportional integral derivative (PID) converter to regulate the speed characteristics of BLDC. PID converter is preferred over all other converters because of its straightforward design and straightforward implementation. Using MATLAB simulation results are verified at different reference speed changing conditions, the motor input current and back electromotive force (EMF) values are verified. The speed and torque characteristics are verified during steady and transient state conduction.

Assessment of a PLL‐ASMO position/speed estimator for sensor‐less control of rotor‐tied DFIG (RDFIG)

AbstractIn this paper, an adaptive sliding mode observer (ASMO) associated with a phase locked loop (PLL) is assessed for the sensor‐less control of a rotor‐tied doubly‐fed induction generator (RDFIG). In the proposed PLL‐ASMO estimator, the ASMO utilizes the stator current, the stator voltage, and the back electromotive force (EMF) as state variables. The proposed ASMO is used in order to estimate the back‐EMF from which the slip position/speed is extracted using a PLL. The design of the ASMO gains is based on the Lyapunov stability criteria to ensure the convergence of the proposed observer in a finite time. Therefore, the main contribution of this paper is to propose a PLL‐based ASMO estimator that aims to improve the estimation by reducing the chattering effect. A comparative study between the standard PLL‐SMO estimator and the PLL‐ASMO estimator is presented. Also, For the first time, an adaptive sliding mode observer is used for the sensor‐less control of a RDFIG. The performance of the proposed sensor‐less control strategy is validated through simulation and experimental measurements under various operating conditions. Furthermore, the estimator is shown to be robust to machine parameter variation.

Analytical Model for Electromagnetic Performance Prediction of IPM Motors Considering Different Rotor Topologies

Aiming at the problem of long computation time of finite element analysis (FEA) and poor calculation universality of existing analytical models, this paper proposes a general hybrid analytical model to predict the no-load and load performance of interior permanent magnet motors with any slot-pole combination, where the form of magnet can be V-shape, U-shape or flat-shape. The magnets are equivalent correspondingly according to the rotor structure in the modeling process and the motor can be divided into eight types of subdomains, the no-load and load magnetic field of the motors can be obtained by solving the equations established by boundary conditions, where the nonlinear of core is calculated by local MEC. The proposed model can be used to calculate the air-gap magnetic field, no-load back electromotive force, cogging torque and electromagnetic torque of IPM motors with different rotor topologies. The effectiveness of the proposed model is verified by both FEA and experiments. Compared with FEA, this model can consume less time with the acceptable accuracy, which brings convenience to the design and optimization of related types of motors.

Design and Optimization of PMSM for Injection Molding Machine

With the implementation of the “dual carbon policy”, the traditional injection molding machine transmission system pays more and more attention to improving the energy efficiency for the drive motor, and the PM motor has obvious advantages in injection molding machine drive motor because of its high efficiency and high-power density. A permanent magnet servo motor (PMSM) for an injection molding machine with a rated power of 7 kW is designed based on the theory of PMSM in this paper. The 2D finite element analysis (FEA) model of the motor is set up. The electromagnetic performance parameters are obtained, including cogging torque, torque ripple, output torque, and no-load back EMF. The cogging torque of the motor is optimized and analyzed. The results show that the optimized motor has reduced the cogging torque and torque ripple without affecting the output capacity, which is more suitable for the application in the drive system of the injection molding machine.

Sensorless control of PMSM based on third harmonic back EMF and SOGI-FLL

Sensorless control of PMSM based on third harmonic back EMF and SOGI-FLL