CN-115459640-B - Method and device for controlling brushless direct current motor in position-free mode

CN115459640BCN 115459640 BCN115459640 BCN 115459640BCN-115459640-B

Abstract

The application discloses a brushless direct current motor position-free control method and a device thereof, wherein the method comprises the steps of obtaining a signal processed by a low-pass filter of a back electromotive force zero crossing point signal of the brushless direct current motor; the method comprises the steps of comparing a filtered back electromotive force zero crossing point signal with a preset value signal, reconstructing the filtered back electromotive force zero crossing point signal to obtain a reconstructed back electromotive force zero crossing point signal, calculating an electrical angle of the reconstructed back electromotive force zero crossing point signal leading or lagging a phase change point of a brushless direct current motor according to a transfer function of a low-pass filter and the electrical angular velocity of the brushless direct current motor, selecting different compensation modes according to the range of the electrical angle, combining the electrical angular velocity of the brushless direct current motor and the reconstructed back electromotive force zero crossing point signal to obtain a phase change point signal, and controlling the brushless direct current motor according to the phase change point signal. The application solves the problem of inaccurate commutation points obtained by a common back electromotive force method.

Inventors

ZHANG PENGFEI
LIN DONGXUAN

Assignees

圣邦微电子（北京）股份有限公司

Dates

Publication Date: 20260508
Application Date: 20220923

Claims (8)

1. A method for position-free control of a brushless dc motor, the method comprising: Acquiring a filtered back electromotive force zero crossing signal, wherein the filtered back electromotive force zero crossing signal is a signal processed by a low-pass filter through the back electromotive force zero crossing signal of the brushless direct current motor; reconstructing the filtered back EMF zero crossing point signal according to the comparison of the filtered back EMF zero crossing point signal and a preset value signal to obtain a reconstructed back EMF zero crossing point signal; The reconstruction of the filtered back EMF zero crossing point signal according to the comparison of the filtered back EMF zero crossing point signal and a preset value signal comprises the steps of comparing the filtered back EMF zero crossing point signal with the preset value signal to obtain a comparison result, wherein the reconstructed back EMF zero crossing point signal is high level if the comparison result is greater than zero, and the reconstructed back EMF zero crossing point signal is low level if the comparison result is less than zero; Calculating the electrical angle of leading or lagging the commutation point of the brushless direct current motor of the reconstructed back electromotive force zero crossing signal according to the transfer function of the low-pass filter and the electrical angular velocity of the brushless direct current motor; selecting different compensation modes according to the electric angle range, and combining the electric angular speed of the brushless direct current motor and the reconstructed back electromotive force zero crossing point signal to obtain a phase change point signal; Selecting different compensation modes according to the electric angle range, and combining the electric angular speed of the brushless direct current motor to obtain the phase change point signal, wherein if the electric angle delta of the reconstructed counter electromotive force zero crossing point signal is less than 0 degree and is in advance or behind the phase change point of the brushless direct current motor, namely, the phase change point is in advance of the counter electromotive force zero crossing point, selecting a prediction compensation mode, specifically, if the reconstructed counter electromotive force zero crossing point signal is detected to jump from low level to high level or from high level to low level, delaying time (180-delta)/omega, obtaining the phase change point of the next moment, overturning the level of the phase change point position signal of the next moment, and omega is the electric angular speed of the motor; And controlling the brushless direct current motor according to the phase change point signal.
2. The method of claim 1, wherein selecting different compensation modes according to the range of electrical angles, and obtaining the commutation point signal in combination with the electrical angular velocity of the brushless dc motor comprises: If the electric angle is larger than 0 degrees and smaller than 30 degrees, a delay compensation mode is selected, and the phase change point signal is obtained by combining the electric angular speed of the brushless direct current motor and the reconstructed back electromotive force zero crossing signal; and if the electric angle is smaller than 0 degree, selecting a prediction compensation mode, and combining the electric angular speed of the brushless direct current motor and the reconstructed back electromotive force zero crossing signal to obtain the phase change point signal.
3. The method of claim 2, wherein selecting the delay compensation mode and combining the electrical angular velocity of the brushless dc motor and the reconstructed back emf zero-crossing signal to obtain the commutation point signal comprises: Calculating the ratio of the electric angle to the electric angular speed to obtain the delay time of the phase change point; and compensating the reconstructed back electromotive force zero crossing signal by the delay time to obtain the phase change point signal.
4. The method of brushless dc motor position-less control of claim 1, wherein prior to said obtaining the filtered back emf zero-crossing signal, the method further comprises: And detecting and acquiring a counter electromotive force zero crossing point signal through a counter electromotive force zero crossing point detection circuit.
5. The method of brushless dc motor position-less control of claim 1, further comprising: Judging whether the rotating speed of the brushless direct current motor is changed or not; if the rotating speed is changed, recalculating a new phase change point signal; And controlling the brushless direct current motor according to the new phase change point signal.
6. A device for position-free control of a brushless dc motor, the device comprising: The acquisition unit is used for acquiring a filtered back electromotive force zero crossing signal, wherein the filtered back electromotive force zero crossing signal is a signal processed by a low-pass filter through the back electromotive force zero crossing signal of the brushless direct current motor; The reconstruction unit is used for reconstructing the filtered back electromotive force zero crossing point signal according to the comparison of the filtered back electromotive force zero crossing point signal and a preset value signal to obtain a reconstructed back electromotive force zero crossing point signal, wherein the reconstruction unit is used for reconstructing the filtered back electromotive force zero crossing point signal according to the comparison of the filtered back electromotive force zero crossing point signal and the preset value signal to obtain a reconstructed back electromotive force zero crossing point signal, and comprises the steps of comparing the filtered back electromotive force zero crossing point signal with the preset value signal to obtain a comparison result, wherein the reconstructed back electromotive force zero crossing point signal is high level if the comparison result is larger than zero, and the reconstructed back electromotive force zero crossing point signal is low level if the comparison result is smaller than zero; The calculating unit is used for calculating the electric angle of the reconstructed back electromotive force zero crossing signal which leads or lags the phase change point of the brushless direct current motor according to the transfer function of the low-pass filter and the electric angular speed of the brushless direct current motor; The compensation unit is used for selecting different compensation modes according to the electric angle range, combining the electric angular speed of the brushless direct current motor and the reconstructed counter electromotive force zero crossing point signal to obtain a phase change point signal, selecting different compensation modes according to the electric angle range, combining the electric angular speed of the brushless direct current motor to obtain the phase change point signal, wherein if the electric angle delta of the reconstructed counter electromotive force zero crossing point signal is less than 0 degree and is in advance or lag behind the phase change point of the brushless direct current motor, namely, the phase change point signal is in advance of the counter electromotive force zero crossing point, the prediction compensation mode is selected, specifically, if the reconstructed counter electromotive force zero crossing point signal is detected to jump from low level to high level or jump from high level to low level, delay time (180 ° -delta)/omega, obtaining the phase change point at the next moment, and overturning the level of the phase change point position signal at the next moment to be the electric angular speed of the motor; and the control unit is used for controlling the brushless direct current motor according to the phase change point signal.
7. A computer-readable storage medium storing computer instructions for causing the computer to perform the method of brushless dc motor position-less control of any one of claims 1 to 5.
8. An electronic device comprising at least one processor and a memory communicatively coupled to the at least one processor, wherein the memory stores a computer program executable by the at least one processor to cause the at least one processor to perform the method of brushless dc motor position-free control of any one of claims 1 to 5.

Description

Method and device for controlling brushless direct current motor in position-free mode Technical Field The application relates to the technical field of motor control, in particular to a brushless direct current motor position-free control method and device. Background In the control of a brushless direct current motor, rotor position information needs to be acquired, proper electromagnetic torque is applied according to the position of the motor, the motor is driven to operate, and a position sensor is usually installed in the application to acquire the position information in real time. However, for a specific application or for cost reduction, it is necessary to normally operate the motor even when the position sensor is not installed or when the position sensor is failed, and thus, position control of the brushless dc motor is necessary. Currently, the most common way of position-free control for brushless dc motors is the back emf method. As shown in fig. 1, which is a graph of the relationship between the counter electromotive force zero-crossing point and the commutation point, it can be seen from fig. 1 that the commutation point Q 1 lags the counter electromotive force zero-crossing point Z 1 ° in electrical angle, the commutation point Q 2 lags the counter electromotive force zero-crossing point Z 2 ° in electrical angle, and so on, that is, the commutation point of the brushless dc motor lags the counter electromotive force zero-crossing point Z 2 ° in electrical angle. Therefore, by detecting the back electromotive force zero crossing point of the non-conductive phase and delaying the back electromotive force zero crossing point by 30 DEG, each phase change point signal can be obtained. In practical applications, however, a low pass filter is required to smooth the back emf as it is constructed. And after the back electromotive force is filtered by the low-pass filter, a phase delay is inevitably present. And when the motor is at different rotating speeds, the back electromotive force delay phases brought by the low-pass filter are also different. I.e. the actual detected back emf is not a hysteresis back emf 30 electrical angle due to filtering effects. Therefore, it is not accurate to detect only the counter electromotive force of the phase and further delay the phase by 30 ° in electrical angle to obtain the commutation point. Inaccurate commutation points can cause failure of the position-free control method, and the motor cannot normally operate. Disclosure of Invention The application mainly aims to provide a method and a device for controlling the brushless direct current motor without position, which solve the problem of inaccurate phase change points obtained by a common back electromotive force method. In order to achieve the above object, according to a first aspect of the present application, there is provided a method of position-free control of a brushless dc motor. The brushless direct current motor position-free control method comprises the steps of obtaining a filtered back electromotive force zero crossing signal, wherein the filtered back electromotive force zero crossing signal is a signal obtained by processing a back electromotive force zero crossing point signal of the brushless direct current motor through a low-pass filter, reconstructing the filtered back electromotive force zero crossing signal according to comparison of the filtered back electromotive force zero crossing point signal and a preset value signal to obtain a reconstructed back electromotive force zero crossing point signal, calculating an electrical angle of the reconstructed back electromotive force zero crossing point signal which is ahead or behind a phase change point of the brushless direct current motor according to a transfer function of the low-pass filter and an electrical angular velocity of the brushless direct current motor, selecting different compensation modes according to a range of the electrical angle, combining the electrical angular velocity of the brushless direct current motor and the reconstructed back electromotive force zero crossing point signal to obtain the phase change point signal, and controlling the brushless direct current motor according to the phase change point signal. Optionally, selecting different compensation modes according to the electric angle range, and obtaining the phase-change point signal by combining the electric angular velocity of the brushless direct current motor includes selecting a delay compensation mode if the electric angle is greater than 0 degrees and less than 30 degrees, obtaining the phase-change point signal by combining the electric angular velocity of the brushless direct current motor and the reconstructed back electromotive force zero-crossing signal, and obtaining the phase-change point signal by selecting a prediction compensation mode if the electric angle is less than 0 degrees and combining the electric angular velocity of the brushl