High-speed Brushless Research Articles

Optimization Experience of a High-Speed Brushless Electric Motor

Optimization Experience of a High-Speed Brushless Electric Motor

Start-up current adaptive control for sensorless high-speed brushless DC motors based on inverse system method and internal mode controller

The start-up current control of the high-speed brushless DC (HS-BLDC) motor is a challenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network (ANN) inverse system and the two degrees of freedom (2-DOF) internal model controller (IMC). The HS-BLDC motor is identified by the online least squares support vector machine (OLS-SVM) algorithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feedback control strategy based on the 2-DOF IMC is proposed to improve the transient response performance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking performance is achieved.

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

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.

Position Sensorless Control Without Phase Shifter for High-Speed BLDC Motors With Low Inductance and Nonideal Back EMF

This paper presents a novel method for position sensorless control of high-speed brushless DC motors with low inductance and nonideal back electromotive force (EMF) in order to improve the reliability of the motor system of a magnetically suspended control moment gyro for space application. The commutation angle error of the traditional line-to-line voltage zero-crossing points detection method is analyzed. Based on the characteristics measurement of the nonideal back EMF, a two-stage commutation error compensation method is proposed to achieve the high-reliable and high-accurate commutation in the operating speed region of the proposed sensorless control process. The commutation angle error is compensated by the transformative line voltages, the hysteresis comparators, and the appropriate design of the low-pass filters in the low-speed and high-speed region, respectively. High-precision commutations are achieved especially in the high-speed region to decrease the motor loss in steady state. The simulated and experimental results show that the proposed method can achieve an effective compensation effect in the whole operating speed region.

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

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.

Sensorless Drive for High-Speed Brushless DC Motor Based on the Virtual Neutral Voltage

The brushless dc (BLDC) motor can be driven by either pulse-width modulation (PWM) or pulse-amplitude modulation (PAM) techniques. Unfortunately, neither of them can be the most suitable method for the high-speed BLDC motor in the wide speed range, so a hybrid drive method combining PWM and PAM is first introduced. Then, this paper proposes a new sensorless control method based on the virtual neutral voltage for high-speed BLDC motor to suit for this hybrid drive method. In order to obtain the commutation signals from this seriously unclear voltage signal due to the commutation notches and electromagnetic interference, a low-pass filter with super low cutoff frequency is employed at the price of a large phase delay. Meanwhile, a novel sensorless control method based on the transition between “90–α” and “150–α” is introduced to handle the severe phase delay. At last, the feasibility and effectiveness of the proposed drive method and the sensorless control method are verified by several experiment results.

Commutation point estimation for sensorless brushless DC motor using back‐electromagnetic force change rate by least‐square method

A new commutation point (CP) estimation method for a high-speed sensorless brushless motor using the back-electromagnetic force (EMF) change rate is proposed. Typical CP estimation methods may not work correctly either at high speed when the number of sampled data is not enough or at low speed when the back-EMF voltage is weak. In the proposed method, the back-EMF voltages are measured using an analogue-to-digital converter. The back-EMF voltage change rate is calculated from the measured values and utilised to estimate the CP by employing the least-square method. The experimental results show that the proposed estimation method works correctly over a wide speed-range operation.

High-Speed Brushless DC Motor Current-Loop Sampling System Design for Three-Axis Turntable

Brushless DC motor (BLDCM) is adopted in the driving of a three-axis turntable. A high-speed current sampling system plays a vital role in intelligent control. This article firstly describes the working principle of a triple-closed-loop regulation system and emphatically dissects the characteristic of the current-loop among speed-loop and position-loop. Secondly, a signal acquisition-alignment circuit of three phases’ current and voltage is designed. Based on ADS8365, a scheme of high-speed current loop’s precise and synchronous sampling system is provided. Finally, experimental results have proved the validity and practicality of the scheme applied in the control of three-axis turntable.

BLDC 고속 센서리스 구동의 ZCP 추정 오차 저감을 위한 Programmable Low Pass Filter 설계

This paper presents a design method of programmable low pass filter(PLPF) which reduce an estimation error of a zero crossing point(ZCP) for a high speed brushless DC(BLDC) motor drive. BLDC motor sensorless drive is possible by estimation of ZCP. The ZCP estimated by detecting a change of back-EMF polarity has the estimation error because noises exist on the measured back-EMF. Therefore a calculated commutation timing using the ZCP is inaccurate. And the inexact commutation timing leads to ripples of 3-phase current and degradation of drive performance. This paper proposes the design method of the PLPF to overcome these problems. First, a speed calculated a inaccurate period of the ZCP is analyzed in the frequency domain. Then, the PLPF that has varying cut-off frequency according to change of the speed is designed on the frequency analysis result. The proposed method is verified by the experiment.

이산화 오차를 고려한 ZCP 추정방법과 고속 BLDC 센서리스 구동에 관한 연구

This paper presents zero crossing point(ZCP) estimation methods considering discretization error for a high speed brushless DC(BLDC) motor drive. The ZCP is estimated by detecting the change of back-EMF polarity for the BLDC sensorless drive, and the discretization error exist on the estimated ZCP. The discretization error of the ZCP is a cause of the delay of a commutation timing of current and increment of a current ripple factor. Besides a delay of a ZCP estimation brings on the limitation of a speed range for the BLDC sensorless drive. The compensation method based on the error analysis with probability theory for reducing the effects of the discretization error of the ZCP is proposed. Also a ZCP estimation method according to the Back-EMF patterns is proposed to widen the speed range for the BLDC sensorless drive. The proposed methods are verified by the experiment.

Self-Compensation of the Commutation Angle Based on DC-Link Current for High-Speed Brushless DC Motors With Low Inductance

As low-resolution position sensors, a high placement accuracy of Hall-effect sensors is hard to achieve. Accordingly, a commutation angle error is generated. The commutation angle error will inevitably increase the loss of the low inductance motor and even cause serious consequence, which is the abnormal conduction of a freewheeling diode in the unexcited phase especially at high speed. In this paper, the influence of the commutation angle error on the power loss for the high-speed brushless dc motor with low inductance and nonideal back electromotive force in a magnetically suspended control moment gyro (MSCMG) is analyzed in detail. In order to achieve low steady-state loss of an MSCMG for space application, a straightforward method of self-compensation of commutation angle based on dc-link current is proposed. Both simulation and experimental results confirm the feasibility and effectiveness of the proposed method.

Proximity Losses in the Windings of High Speed Brushless Permanent Magnet AC Motors With Single Tooth Windings and Parallel Paths

Proximity and additional eddy-current losses can be difficult to calculate and if there are parallel paths then there can sometimes be increased losses which can be unexpected. The paper addresses these winding losses in a brushless permanent magnet machine with 18 slots, 16 poles and a spoke type rare earth magnet rotor. The winding has coils that are one pitch. Different simulation scenarios are investigated to illustrate the even when the windings are in slots they can still experience increased ac copper losses when rotating at high speed. High speed machines often have few series turns because of the high rate of change of flux linkage so they can have many parallel turns or strands in hand. Simulations are carried out at 12 000 r/min then some simulations are run at 4000 r/min for completeness. The simulations are run in a 2-D finite-element analysis environment.

Design and Characterization of an E-booster Driven by an High Speed Brushless DC Motor

Engine downsizing has become one of the main strategies to reduce C02 emission. Turbochargers are well-adapted to this purpose but one of their biggest drawbacks is the turbo-lag which reduces the driving comfort especially during acceleration. Electrically driven compressors also known as E-compressor or E-booster could be a well-adapted solution to boost the engine intake pressure in order to reduce the turbo-lag. Since centrifugal compressors operate at high rotational speeds, high speed electric machines are therefore required. To achieve a significant reduction of the turbo-lag, a very fast response time is needed leading to the development of electric machines able to typically spin from idle to 75kRPM in less than 300ms. With 20 years of expertise in the development of innovative brushless DC motors for automotive applications, MMT has recently investigated the design of such high power-high rotation speed motors. After first integrated an electric motor into a turbocharger described in [1], MMT has decided to optimize the complete system in collaboration with SwissAuto Wenko AG, a specialist in the design and characterization of advanced charging systems. The initial specification was an overpressure of 1.3 within 300ms, reached by using a 2kW@80kRPMs electric motor. The motor optimization, the mechanical design of the system as well as experimental measurements are presented. Details about the brushless DC motor design will be given as well as compressor maps and transient response behaviors. Results will also show that the transient state performances are better than expected.

Electric Compressor With High-Speed Brushless DC Motor

Electric Compressor With High-Speed Brushless DC Motor

Study on rotor structure with different magnet assembly in high-speed sensorless brushless DC motors

High-speed permanent magnet (PM) brushless DC motors have gained more and more interests for many applications. The technique of detecting the electromotive force (EMF) zero-crossings is a common method in sensorless operation of PM brushless DC motors. However, the zero-crossings of the phase EMF will be obscured and the sensorless control will be malfunctioned, since the free-wheeling diode conduction can last more than 30 elec-degs under high-speed condition. Therefore it is supposed that the utilisation of third-harmonic EMF is more preferable, as it is not influenced by the free-wheeling diode conduction. Some design features for the high-speed sensorless operation are presented, primarily focusing on the rotor structure with different magnet assembly. The influence of the pole-arc to pole-pitch ratio on the third-harmonic airgap field will be analysed with both finite-element method and analytical model. Based on these analyses, another method which can improve both the third harmonic and fundamental components in the airgap field, by segmenting the parallel-magnetised PMs, is employed and studied. Motor prototypes are then designed and fabricated, and the experimental results confirm the validity of the proposed design method.

Operating Torque Estimation of High-Speed Slotless Brushless DC Machine Considering Power Loss

Torque is very essential for performance evaluation of electric machines because it is directly connected with power loss for dynamic characteristics. To evaluate dynamic performance, torque with harmonic component according to time is introduced. Particularly, eddy current loss is significantly increased at high speed, so it is difficult to express the dynamic characteristic without reflection about losses. Therefore, in this paper, rotor eddy current loss wave is derived by fast Fourier transform which uses the phase current wave obtained from finite element analysis according to two conditions: one has rotor eddy current loss, the other does not. The core loss is deduced by a modified Steinmetz equation and additional losses are considered from an experiment. Those losses are worked as drag torque which is inverse force to performance of a machine. The operating torque estimated from the difference between drag torque and electric torque closely reflects the dynamic characteristics.

A current ripple reduction of a high-speed miniature brushless direct current motor using instantaneous voltage control

High-speed miniature brushless direct current motor (BLDCM) is used in robots and medical applications because of its high-torque and high-speed characteristics. When compared with the general BLDCM, a high-speed miniature BLDCM has a low electrical time-constant. The current and torque ripple are very high when compared with the conventional pulse-width modulation (PWM) control scheme in the conduction period because of the inherent electrical characteristics. The authors propose a simple instantaneous source voltage and phase current control for torque ripple reduction of a high-speed miniature BLDCM. To reduce the switching current ripple, instantaneously controlled source voltage is supplied to the inverter system according to the motor speed and the load torque. In addition, a fast hysteresis current controller can keep the phase current within a limited band. Computer simulations and experimental results up to 40 000 rpm show the effectiveness and verification of the proposed control scheme.

A Magnetic-Geared Outer-Rotor Permanent-Magnet Brushless Machine for Wind Power Generation

This paper presents a new permanent-magnet (PM) brushless machine for wind power generation. This machine adopts an outer-rotor topology, aiming at capturing wind power directly. In order to achieve high power density, a high-speed PM brushless generator is artfully integrated with a coaxial magnetic gear. The design details, with emphasis on the special constraints of wind power generation, are elaborated. By using the time-stepping finite element method, the static characteristics as well as no-load and on-load operations are simulated. A prototype is also built for experimentation. Both simulation and experimental results are given to verify the validity of the proposed machine. Finally, a quantitative comparison is made to justify that the proposed machine is of smaller size, lighter weight, and lower cost than its counterparts.

Design aspects of a high-speed sensorless brushless dc motor using third harmonic back-emf for sensorless control

There is increasing interest in high-speed permanent magnet (PM) brushless dc motors for a wide range of applications. Back-emf is often utilized for sensorless operation of permanent magnet brushless dc motors, by detecting the emf zero crossings. However, in high-speed motors, the free-wheeling diode conduction can last more than 30edeg. This can obscure the zero crossings of the phase EMF; therefore, it is preferable to utilize the third harmonic emf instead of the phase emf. In this paper, some design aspects related to this high-speed sensorless operation are presented, including a special nonoverlapping winding arrangement and magnet segmenting technique. Finally, the experimental results confirmed the validity of the proposed design method.

Research Progress on the Application of High-speed Brushless DC Motor in Magnetically Suspended Inertial Actuator

There are various applications of permanent magnet brushless DC motor (BDCM). They offer a number of attractive features and could meet the requirements coming from new generation satellites such as high attitude precision, high maneuver capacity and high stability. Therefore, high speed magnetically suspended inertia devices using BDCM is becoming the best choice for inertia actuators. In this paper, design principles including hollow cup BDCM electromagnetic design method and optimized structural design methods are reviewed. Also, the control methods of high speed BDCM used for magnetically suspended flywheel (MSFW) including PLL method, double mode control method and current restraint method are reviewed. The worldwide applications of high speed BDCM in magnetically suspended inertia actuators are considered.