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, we propose a new R/D (Resolver-to -Digital) conversion method, in which a bang-bang type phase comparator is employed for fast tracking. We eliminate from the R/D conversion loop the low-pass filter which is needed to reject carrier signal and noise. Instead, we employ two prefilters outside the R/D conversion loop that take the role of the low-pass filter. Thereby, we can construct a fast and accurate tracking R/D converter. Some simulation and experimental results as well as mathematical performance analysis are presented to demonstrate the superior tracking performance of our R/D converter over conventional tracking R/D converters.

A Resolver-to-Digital Conversion Method for Fast Tracking

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.

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

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.

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

This paper proposes a compensation algorithm for reducing the position errors that are due to two nonideal output signals of a resolver in the vector control of a permanent magnet synchronous motor. Practically, a resolver generates periodic position errors because of the amplitude imbalance and imperfect quadrature between the two output signals of the resolver. As a result, the dq-axis currents of the synchronous reference frame have ripple components that are twice the stator fundamental frequency. In this paper, the effects of the position errors are analyzed on the basis of the synchronous dq-axis current equations, including the position errors. The d-axis current is directly used as the input signal of the proposed compensator to estimate the position errors by using a simple integral operation according to the rotor position, because the d-axis current is typically constant or zero. The proposed algorithm additionally considers the bandwidth effect of the closed current control loop to estimate the exact error signals according to the variation of the rotor speed. Therefore, the proposed algorithm does not need any additional hardware and much computation time. Furthermore, this algorithm can be applied to both the steady and transient states. The experimental results verify the effectiveness of the proposed algorithm.

Compensation of Amplitude Imbalance and Imperfect Quadrature in Resolver Signals for PMSM Drives

A new sensorless control algorithm for brushless dc motors (BLDCMs) is proposed in this paper. The torque constant of a BLDCM is used as a reference signal for position detection because it is constant during the entire speed range and can be estimated by calculating the ratio of the back electromotive force (EMF) to the rotor speed. By using both a disturbance observer and the torque constant estimation error, the rotor speed can be obtained. The back EMF can be easily obtained from the voltage equation of the BLDCM. The estimated back EMF decreases simultaneously with the estimated torque constant at the commutation point. By using this phenomenon, the commutation of the phase currents can be done automatically at the drop point of the estimated torque constant. Unlike conventional back-EMF-based methods, the proposed method provides highly accurate sensorless operation even under low speeds because only the drop of the torque constant is used for position detection and current commutation. Therefore, the position accuracy is not affected by the electric parameter errors of the BLDCM. Also, this algorithm does not require an additional hardware circuit for position detection. The validity of the proposed algorithm is verified through several experiments.

Sensorless Control of Brushless DC Motors With Torque Constant Estimation for Home Appliances

This paper presents a compensation algorithm for position error due to an amplitude imbalance between resolver output signals Resolvers are typically used to obtain absolute position information for motor drive systems in severe environments Position error is caused by an amplitude imbalance of the resolver output signals As a result, the d- and q-axis currents of synchronous reference frame have periodic ripples in the stator fundamental frequency in permanent magnet synchronous motor (PMSM) drive systems Therefore, this paper proposes a compensation algorithm to reduce the position error generated by the amplitude imbalance The proposed method does not require any additional hardware, and reduces computation time with a simple integral operation according to rotor position In addition, the position error can be directly compensated for by the estimated position error The effectiveness of the proposed compensation algorithm is verified through several simulations and experiments

/pdf/compensation-of-position-error-due-to-amplitude-imbalance-in-5c4zt3qu8e.pdf

Compensation of Position Error due to Amplitude Imbalance in Resolver Signals

This paper proposes an estimation algorithm for the electrical parameters of synchronous reluctance motors (SynRMs) by using a synchronous PI current regulator at standstill. In reality, the electrical parameters are only measured or estimated in limited conditions without fully considering the effects of the switching devices, connecting wires, and magnetic saturation. As a result, the acquired electrical parameters are different from the real parameters of the motor drive system. In this paper, the effects of switching devices, connecting wires, and the magnetic saturation are considered by simultaneously using the short pulse and closed loop equations of resistance and synchronous inductances. Therefore, the proposed algorithm can be easily and safely implemented with a reduced measuring time. In addition, it does not need any external or additional measurement equipment, information on the motor’s dimensions, and material characteristics as in the case of FEM. Several experimental results verify the effectiveness of the proposed algorithm.

http://www.koreascience.or.kr:80/article/JAKO201033359740591.pdf

Parameter Identification of a Synchronous Reluctance Motor by using a Synchronous PI Current Regulator at a Standstill

This paper describes the ultra precise position estimation of a servomotor using a sinusoidal encoder based on Arcsine Interpolation Method for the cost reduction of circuit design. The amplitude and offset errors of the sinusoidal encoder output signals, from the encoder itself and analog signal processing procedures, are effectively compensated and on-line tuned by utilizing a low cost programmable differential amplifier without any special expensive equipment. For a theoretical evaluation of the practical resolution of this system, the relationship between the amplitude of ADC(Analog to Digital Converter) input signal errors and the anticipated resolution is also addressed. The performance of the proposed method is verified by comparing it with speed control characteristics of the servomotor driving system using a digital incremental 50,000ppr encoder in the experiments.

https://jpels.org/digital-library/manuscript/file/17376/JPE 6-2-6.pdf

Ultra Precise Position Estimation of Servomotor using Analog Quadrature Encoder

This paper proposes a compensation algorithm for the analog rotor position errors caused by nonideal sinusoidal encoder output signals including offset and gain errors. In order to achieve a much higher resolution, position sensors such as resolvers or incremental encoders can be replaced by sinusoidal encoders. In practice, however, the periodic ripples related to the analog rotor position are generated by the offset and gain errors between the sine and cosine output signals of sinusoidal encoders. In this paper, the effects of offset and gain errors are easily analyzed by applying the concept of a rotating coordinate system based on the dq transformation method. The synchronous d-axis signal component is used directly to detect the amplitude of the offset and gain errors for the proposed compensator. As a result, the offset and gain errors can be well corrected by three integrators located on the synchronous d-axis component. In addition, the proposed algorithm does not require any additional hardware and can be easily implemented by a simple integral operation. The effectiveness of the proposed algorithm is verified through several experimental results.

/pdf/signal-compensation-for-analog-rotor-position-errors-due-to-5gmv5gq2or.pdf

Seon-Hwan Hwang

Papers

Sensorless Control of Brushless DC Motors With Torque Constant Estimation for Home Appliances

Compensation of Position Error due to Amplitude Imbalance in Resolver Signals

Parameter Identification of a Synchronous Reluctance Motor by using a Synchronous PI Current Regulator at a Standstill

Ultra Precise Position Estimation of Servomotor using Analog Quadrature Encoder

Signal Compensation for Analog Rotor Position Errors due to Nonideal Sinusoidal Encoder Signals