Permanent magnet (PM) brushless machines having magnets and windings in stator (the so-called stator-PM machines) have attracted more and more attention in the past decade due to its definite advantages of robust structure, high power density, high efficiency, etc. In this paper, an overview of the stator-PM machine is presented, with particular emphasis on concepts, operation principles, machine topologies, electromagnetic performance, and control strategies. Both brushless ac and dc operation modes are described. The key features of the machines, including the merits and drawbacks of the machines, are summarized. Moreover, the latest development of the machines is also discussed.

Overview of Stator-Permanent Magnet Brushless Machines

This paper provides a technical review of position and speed sensorless methods for controlling Brushless Direct Current (BLDC) motor drives, including the background analysis using sensors, limitations and advances. The performance and reliability of BLDC motor drivers have been improved because the conventional control and sensing techniques have been improved through sensorless technology. Then, in this paper sensorless advances are reviewed and recent developments in this area are introduced with their inherent advantages and drawbacks, including the analysis of practical implementation issues and applications. The study includes a deep overview of state-of-the-art back-EMF sensing methods, which includes Terminal Voltage Sensing, Third Harmonic Voltage Integration, Terminal Current Sensing, Back-EMF Integration and PWM strategies. Also, the most relevant techniques based on estimation and models are briefly analysed, such as Sliding-mode Observer, Extended Kalman Filter, Model Reference Adaptive System, Adaptive observers (Full-order and Pseudoreduced-order) and Artificial Neural Networks.

https://www.mdpi.com/1424-8220/10/7/6901/pdf

Position and speed control of brushless DC motors using sensorless techniques and application trends.

A sensorless control method for a high-speed brushless DC motor based on the line-to-line back electromotive force (back EMF) is proposed in this paper. In order to obtain the commutation signals, the line-to-line voltages are obtained by the low-pass filters. However, due to the low-pass filters, wide speed range, and other factors, the actual commutation signals are significantly delayed by more than 90 electrical degrees which limits the acceleration of the motor. A novel sensorless commutation algorithm based on the hysteresis transition between “90-α” and “150-α” is introduced to handle the severe commutation retarding and guarantee the motor works in a large speed range. In order to compensate the remaining existing commutation errors, a novel closed-loop compensation algorithm based on the integration of the virtual neutral voltage is proposed. The integration difference between the adjacent 60 electrical degrees interval before and after the commutation point is utilized as the feedback of the PI regulator to compensate the errors automatically. Several experiment results confirm the feasibility and effectiveness of the proposed method.

Sensorless Control for High-Speed Brushless DC Motor Based on the Line-to-Line Back EMF

In this paper, a general design procedure for the flux-switching permanent magnet (FSPM) machine with different topologies is proposed. Firstly, a 3-phase 12-stator-tooth/10-rotor-pole topology is introduced and its operation principle is described. Then, the basic design method, including determination of the stator, rotor and magnet dimensions, is proposed under the constraints of some dimensions and electrical parameters. The winding turns are obtained by iteratively solving the base-speed and current equations simultaneously. The influence of current density and slot packing factor on the flux-weakening capability is investigated in the design stage to satisfy the torque and wide-speed operation requirement. Further, the output power equation, consequently, the sizing equation is derived for determining the initial dimensions of a FSPM machine, in which the traditional D2 sil a is replaced by D2 sola. Hence, the power density of different topologies can be compared directly by the equation. It reveals that the 3-phase 12/10-pole topology can offer higher power and power density than those of the 2-phase 8/6-pole machine by ~11% in theory under the same conditions. The experiments on the prototype motor verify the performance predictions

Design of Flux-Switching Permanent Magnet Machine Considering the Limitation of Inverter and Flux-Weakening Capability

In this paper, a novel drive method, which is different from the traditional motor drive techniques, for high-speed brushless DC (BLDC) motor is proposed and verified by a series of experiments. It is well known that the BLDC motor can be driven by either pulse-width modulation (PWM) techniques with a constant dc-link voltage or pulse-amplitude modulation (PAM) techniques with an adjustable dc-link voltage. However, to our best knowledge, there is rare study providing a proper drive method for a high-speed BLDC motor with a large power over a wide speed range. Therefore, the detailed theoretical analysis comparison of the PWM control and the PAM control for high-speed BLDC motor is first given. Then, a conclusion that the PAM control is superior to the PWM control at high speed is obtained because of decreasing the commutation delay and high-frequency harmonic wave. Meanwhile, a new high-speed BLDC motor drive method based on the hybrid approach combining PWM and PAM is proposed. Finally, the feasibility and effectiveness of the performance analysis comparison and the new drive method are verified by several experiments.

A Novel Drive Method for High-Speed Brushless DC Motor Operating in a Wide Range

In this paper, a new 12/8-pole doubly salient permanent-magnet (DSPM) machine is designed and analyzed. Due to its DSPM nature, this machine incorporates the advantageous features of their PM brushless DC (PMBLDC) and switched reluctance (SR) counterparts. Also, due to the unique 12/8-pole topology with rotor skewing, it offers excellent power density, minimum copper consumption and winding resistance as well as torque ripple. Its characteristics, including PM flux linkage, back EMF, and inductance, are analyzed by using the finite element method (FEM) in which the interaction between the PM field and the armature field are taken into account.

http://ieeexplore.ieee.org/iel5/8980/28507/01273800.pdf

Design and performance analysis of new 12/8-pole doubly salient permanent-magnet motor

In this paper, two kinds of commutation modes of the brushless DC(BLDC) motor drives, the delaying commutation and the leading commutation, are discussed in detail. The current of the unexcited phase is calculated under an ideal operation condition, and the condition of circulating current occurring is analyzed. The result with the compensated commutation is provided. The theoretical analysis is confirmed by the experiment results.

http://www.meeting.edu.cn/meeting/webmedia/jingpin/icmes/pdf/A183.pdf

Effect of rotor position error on commutation in sensorless BLDC motor drives

This paper presents a novel startup method of a brushless DC motor (BLDCM) without any reverse rotation and vibration. Using short pulse sensing method, the rotor position can be detected dynamically based on the saturation effect of the stator iron. After accelerating the motor to a certain speed at which the back-electromotive force (EMF) method is applied, all the power devices are turned off and the terminal voltage variation can be used to determine the switch moment and the corresponding commutation phases. The back-EMF zero-crossing point detection is conducted at the end of PWM on-state and the true zero-crossing point is extracted through the proposed algorithm. The experiment results have verified the feasibility and validity of the presented method.

A novel and easy-realizing initial rotor position detection method and speedup algorithm for sensorless BLDC motor drives

In sensorless operation of brushless DC motor drives, a typical method called "back EMF method", is sampled to detect the induced EMF zero-crossing of the unexcited winding The filters are used to eliminate high frequency components of the terminal voltages and to extract back EMF of the motor In this paper, FFT analyses of terminal voltage contents of the BLDC motor are presented The principles of filters are introduced, and two kinds of filters, a passive band-pass filter and an active low-pass filter, are designed for BLDC motor drives The study shows that the theoretical analysis is coincide with that of the experiments

Research on filters for back EMF zero-crossing detecting in sensorless BLDC motor drives

A Linear Rotary Permanent Magnet Generator(LRPMG) is proposed for wind-wave combined power generation system(WWCPGS). The rotary unit and linear unit of the LRPMG can be used to generate electricity by wind energy and wave energy, respectively. Compared with rotary generator by single wind power and linear generator by single wave power, the LRPMG can improve the utilization rate of the material and improve the power density of the motor. The characteristics, including three-phase back electromotive force (EMF), terminal voltage, air-gap flux density and external characteristic of the LRPMG are analyzed by the finite-element method (FEM).

Lin Mingyao

Papers

Design and performance analysis of new 12/8-pole doubly salient permanent-magnet motor

Effect of rotor position error on commutation in sensorless BLDC motor drives

A novel and easy-realizing initial rotor position detection method and speedup algorithm for sensorless BLDC motor drives

Research on filters for back EMF zero-crossing detecting in sensorless BLDC motor drives

Design and analysis of linear rotary permanent magnet generator for wind-wave combined power generation system