Method and device for positionless control of a brushless direct current motor

Abstract

The application discloses a method and device for positionless control of a brushless direct current motor. The method comprises the following steps: obtaining a signal of a back electromotive force zero-crossing point signal of the brushless direct current motor after low-pass filter processing; reconstructing the back electromotive force zero-crossing point signal after filtering to obtain a reconstructed back electromotive force zero-crossing point signal according to comparison between the back electromotive force zero-crossing point signal after filtering and a preset value signal; calculating an electrical angle in which the reconstructed back electromotive force zero-crossing point signal leads or lags a commutation 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 the range of the electrical angle, and obtaining a commutation point signal in combination with the electrical angular velocity of the brushless direct current motor and the reconstructed back electromotive force zero-crossing point signal; and controlling the brushless direct current motor according to the commutation point signal. The application solves the problem that the commutation point obtained by using a common back electromotive force method is inaccurate.

Description

Technical Field

[0001] This application relates to the field of motor control technology, and more specifically, to a method and apparatus for position control of a brushless DC motor. Background Technology

[0002] When controlling a brushless DC motor, it is necessary to obtain rotor position information and apply appropriate electromagnetic torque based on the motor's position to drive it. In typical applications, position sensors are installed to acquire position information in real time. However, in specific situations or to reduce costs, it is necessary for the motor to operate normally even without a position sensor or when the position sensor fails. In such cases, positionless control of the brushless DC motor is essential.

[0003] Currently, the most common method for positionless control of brushless DC motors is the back electromotive force method. For example... Figure 1 The diagram shown is a graph relating the zero-crossing point of the back electromotive force to the commutation point. Figure 1 As can be seen, commutation point Q1 lags behind the zero-crossing point Z1 of the back EMF of phase A by 30° electrical angle, commutation point Q2 lags behind the zero-crossing point Z2 of the back EMF of phase C by 30° electrical angle, and so on. That is, the commutation point of the brushless DC motor lags behind the back EMF by 30° electrical angle. Therefore, by detecting the zero-crossing point of the back EMF of the non-conducting phase and then delaying it by 30° electrical angle, the commutation point signals can be obtained. However, in practical applications, a low-pass filter is needed to smooth the back EMF when constructing it. After filtering by the low-pass filter, a phase delay is unavoidable. Furthermore, the phase delay of the back EMF caused by the low-pass filter varies depending on the motor speed. That is, due to the filtering effect, the actual detected back EMF is not 30° electrical angle behind the back EMF. Therefore, obtaining the commutation point by only detecting the back EMF and then delaying it by 30° electrical angle is inaccurate. Inaccurate commutation points will cause the positionless control method to fail, and the motor will not operate normally. Summary of the Invention

[0004] The main objective of this application is to provide a method and apparatus for position control of a brushless DC motor, which solves the problem of inaccurate commutation point obtained by the commonly used back electromotive force method.

[0005] To achieve the above objectives, according to a first aspect of this application, a method for positionless control of a brushless DC motor is provided.

[0006] The method for positionless control of a brushless DC motor according to this application includes: acquiring a filtered back EMF zero-crossing signal, wherein the filtered back EMF zero-crossing signal is a signal processed by a low-pass filter after the back EMF zero-crossing signal of the brushless DC motor is processed; reconstructing the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain a reconstructed back EMF zero-crossing signal; calculating the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor; selecting different compensation methods according to the range of the electrical angle, and obtaining the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; and controlling the brushless DC motor based on the commutation point signal.

[0007] Optionally, the step of selecting different compensation methods according to the range of the electrical angle and obtaining the commutation point signal by combining the electrical angular velocity of the brushless DC motor includes: if the electrical angle is greater than 0 degrees and less than 30 degrees, then a delay compensation method is selected, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; if the electrical angle is less than 0 degrees, then a predictive compensation method is selected, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal.

[0008] Optionally, the method of selecting the delay compensation method and obtaining the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal includes: calculating the ratio of the electrical angle to the electrical angular velocity to obtain the commutation point delay time; and obtaining the commutation point signal by compensating the reconstructed back EMF zero-crossing signal with the delay time.

[0009] Optionally, the step of selecting the predictive compensation method and obtaining the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal includes: calculating the difference between 180 degrees and the electrical angle, and calculating the ratio of the difference to the electrical angular velocity to obtain the commutation point delay time at the next moment; and obtaining the commutation point signal by compensating the reconstructed back EMF zero-crossing signal with the commutation point delay time at the next moment.

[0010] Optionally, the step of reconstructing the filtered back EMF zero-crossing signal based on the comparison between the filtered back EMF zero-crossing signal and the preset value signal to obtain the reconstructed back EMF zero-crossing signal includes: comparing the filtered back EMF zero-crossing signal with the preset value signal to obtain a comparison result; if the comparison result is greater than zero, the reconstructed back EMF zero-crossing signal is at a high level; if the comparison result is less than zero, the reconstructed back EMF zero-crossing signal is at a low level.

[0011] Optionally, before acquiring the filtered back EMF zero-crossing signal, the method further includes: detecting and acquiring the back EMF zero-crossing signal through a back EMF zero-crossing detection circuit.

[0012] Optionally, the method further includes: determining whether the speed of the brushless DC motor has changed; if the speed has changed, recalculating a new commutation point signal; and controlling the brushless DC motor according to the new commutation point signal.

[0013] To achieve the above objectives, according to a second aspect of this application, a device for position control of a brushless DC motor is provided.

[0014] The brushless DC motor position control device according to this application includes: an acquisition unit for acquiring a filtered back EMF zero-crossing signal, wherein the filtered back EMF zero-crossing signal is a signal obtained by processing the back EMF zero-crossing signal of the brushless DC motor through a low-pass filter; a reconstruction unit for reconstructing the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain a reconstructed back EMF zero-crossing signal; a calculation unit for calculating the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor; a compensation unit for selecting different compensation methods according to the range of the electrical angle and obtaining the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; and a control unit for controlling the brushless DC motor according to the commutation point signal.

[0015] Optionally, the compensation unit includes: a delay compensation module, used to select the delay compensation method when the electrical angle is greater than 0 degrees and less than 30 degrees, and to obtain the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; and a prediction compensation module, used to select the prediction compensation method when the electrical angle is less than 0 degrees, and to obtain the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal.

[0016] Optionally, the delay compensation module is used to: calculate the ratio of the electrical angle to the electrical angular velocity to obtain the commutation point delay time; and obtain the commutation point signal by compensating the reconstructed back electromotive force zero-crossing signal with the delay time.

[0017] Optionally, the prediction compensation module is used to: calculate the difference between 180 degrees and the electrical angle, and calculate the ratio of the difference to the electrical angular velocity to obtain the commutation point delay time at the next moment; and obtain the commutation point signal by compensating the reconstructed back electromotive force zero-crossing signal with the commutation point delay time at the next moment.

[0018] Optionally, the reconstruction unit includes: a comparison module, used to compare the filtered back EMF zero-crossing signal with a preset value signal to obtain a comparison result; a first determination module, used to set the reconstructed back EMF zero-crossing signal to a high level if the comparison result is greater than zero; and a second determination module, used to set the reconstructed back EMF zero-crossing signal to a low level if the comparison result is less than zero.

[0019] Optionally, the device further includes a detection unit, used to detect and acquire the back EMF zero-crossing signal through a back EMF zero-crossing detection circuit before acquiring the filtered back EMF zero-crossing signal.

[0020] Optionally, the device further includes: a judgment unit for judging whether the speed of the brushless DC motor has changed; the calculation unit for recalculating a new commutation point signal if the speed changes; and the control unit for controlling the brushless DC motor according to the new commutation point signal.

[0021] To achieve the above objectives, according to a third aspect of this application, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions for causing the computer to perform the method for positionless control of a brushless DC motor as described in any of the first aspects above.

[0022] To achieve the above objectives, according to a fourth aspect of this application, an electronic device is provided, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, the computer program being executed by the at least one processor to cause the at least one processor to perform the method for positionless control of a brushless DC motor as described in any of the first aspects above.

[0023] In the method and apparatus for position control of a brushless DC motor according to embodiments of this application, a filtered back EMF zero-crossing signal is obtained. The filtered back EMF zero-crossing signal is the signal after the back EMF zero-crossing signal of the brushless DC motor has been processed by a low-pass filter. The filtered back EMF zero-crossing signal is reconstructed by comparing it with a preset value signal to obtain a reconstructed back EMF zero-crossing signal. The reconstructed back EMF zero-crossing signal is calculated to lead or lag the electrical angle of the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor. Different compensation methods are selected according to the range of the electrical angle, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal. The brushless DC motor is controlled based on the commutation point signal. As can be seen, in the back EMF method in this application embodiment, the commutation point is not obtained by delaying the actual detected back EMF by 30° electrical angle. Instead, the electrical angle that the back EMF zero-crossing signal leads or lags behind the commutation point of the brushless DC motor is first calculated, and then the back EMF is compensated in different ways according to the electrical angle to finally obtain a more accurate commutation point. Attached Figure Description

[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the application and to make other features, objects, and advantages of the application more apparent. The illustrative embodiments and descriptions of this application are used to explain the application and do not constitute an undue limitation of the application. In the drawings:

[0025] Figure 1 This is a diagram showing the relationship between the zero-crossing point and the commutation point of the back electromotive force (EMF) according to the existing back EMF method.

[0026] Figure 2 This is a flowchart of a method for positionless control of a brushless DC motor according to an embodiment of this application;

[0027] Figure 3 This is an example diagram of a back EMF zero-crossing detection circuit provided in an embodiment of this application;

[0028] Figure 4 This is a schematic diagram of a delay compensation method provided according to an embodiment of this application;

[0029] Figure 5 This is a schematic diagram of a Bode plot provided according to an embodiment of this application;

[0030] Figure 6 This is a schematic diagram of a predictive compensation method provided according to an embodiment of this application;

[0031] Figure 7 This is a flowchart of another method for positionless control of a brushless DC motor according to an embodiment of this application;

[0032] Figure 8 This is a block diagram of a device for a brushless DC motor without position control, provided according to an embodiment of this application.

[0033] Figure 9 This is a block diagram of another brushless DC motor device without position control provided according to an embodiment of this application. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0035] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0036] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0037] According to an embodiment of this application, a method for position control of a brushless DC motor is provided, such as... Figure 2As shown, the method includes the following steps S101-S105: S101. Obtain the filtered back EMF zero-crossing signal, which is the signal after the back EMF zero-crossing signal of the brushless DC motor has been processed by a low-pass filter; S102. Reconstruct the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain the reconstructed back EMF zero-crossing signal; S103. Calculate the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor; S104. Select different compensation methods according to the range of electrical angle, and obtain the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; S105. Control the brushless DC motor according to the commutation point signal.

[0038] In step S101, the acquired signal is the filtered back EMF zero-crossing signal. Therefore, it is necessary to acquire the back EMF zero-crossing signal before this step, and then process the back EMF zero-crossing signal through a low-pass filter. Specifically, the back EMF zero-crossing signal is first acquired by a back EMF zero-crossing detection circuit. Figure 3 As shown, this is a back EMF zero-crossing detection circuit provided in an embodiment of this application. The specific circuit principle is as follows: First, the three-phase terminal voltage (U) of the brushless DC motor is checked. A U B U C The filter is applied using a low-pass filter, and then the neutral point U is constructed. N The three-phase voltages are obtained as U a U b U c Then, a comparator compares the filtered phase voltage with the voltage between the neutral point to construct the back EMF zero-crossing point, thus outputting the back EMF zero-crossing signal e for each phase. A e B e C After obtaining the zero-crossing signals of the back EMF of each phase, these signals are acquired and processed by a microcontroller unit (MCU), also known as a single-chip microcomputer. Specifically, the three-phase back EMF zero-crossing signals can be acquired through the MCU's three input / output (I / O) ports. To ensure the obtained back EMF zero-crossing signals are continuous and smooth, they are filtered using a low-pass filter, resulting in the filtered back EMF zero-crossing signals.

[0039] In step S102, reconstructing the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain the reconstructed back EMF zero-crossing signal includes: comparing the filtered back EMF zero-crossing signal with the preset value signal to obtain a comparison result; if the comparison result is greater than zero, the reconstructed back EMF zero-crossing signal is at a high level; if the comparison result is less than zero, the reconstructed back EMF zero-crossing signal is at a low level. It should be noted that the filtered back EMF zero-crossing signal is a value between 0 and 1. Therefore, in this embodiment, the preset value signal is a fixed value between 0 and 1, such as 0.5. In practical applications, it can also be other values ​​such as 0.6. Figure 4 As shown, a schematic diagram of the reconstructed back EMF zero-crossing signal A of one of the three phases is presented. The waveforms of the reconstructed back EMF zero-crossing signals of the other two phases are the same as those of signal A, except that there is a phase difference.

[0040] In step S103, the calculation of the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor, based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor, can be achieved as follows: First, a Bode plot is constructed based on the transfer function of the low-pass filter. Then, based on the Bode plot and the electrical angular velocity of the brushless DC motor, the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor can be calculated. The calculation method is explained in conjunction with a specific Bode plot: [Example follows] Figure 5 The image shown is a schematic diagram of a Bode plot provided in an embodiment of this application. Figure 5 In the diagram, the horizontal axis "Frequency" represents the electric angular velocity of the motor, and the vertical axis represents the delay or hysteresis angle corresponding to the low-pass filter. Figure 5 As can be seen, different electrical angular velocities correspond to different delay or lag angles. In the calculation, the delay or lag angle corresponding to the low-pass filter is first obtained based on the current electrical angular velocity of the motor and the Bode plot. Then, 30° electrical angle (the electrical angle difference between the commutation point and the zero-crossing point of the back EMF, as determined theoretically in the commonly used back EMF method) is added to this angle. This yields the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor.

[0041] In step S104, different compensation methods are selected based on the range of whether the back EMF zero-crossing signal leads or lags behind the electrical angle of the commutation point of the brushless DC motor. The commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal. This includes: if the electrical angle is greater than 0 degrees and less than 30 degrees, a delay compensation method is selected, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; if the electrical angle is less than 0 degrees, a predictive compensation method is selected, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal.

[0042] Furthermore, the delay compensation method is as follows: The commutation point delay time is obtained by calculating the ratio of the electrical angle (the electrical angle at which the back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor) to the electrical angular velocity; the commutation point signal is then obtained by compensating for the delay time after reconstructing the back EMF zero-crossing signal. This compensation method corresponds to the commutation point lagging behind the back EMF zero-crossing. A schematic diagram of the specific delay compensation is shown below. Figure 4 As shown, signal A is one of the corresponding reconstructed back EMF zero-crossing signals, signal B is the desired commutation point position signal, and angle δ is the electrical angle by which the reconstructed back EMF zero-crossing signal leads the commutation point of the brushless DC motor. Figure 4 As can be seen, the reconstructed back EMF zero-crossing signal, after being delayed by a software delay of δ electrical angle, becomes the commutation point position signal. Specifically, if the motor's electrical angular velocity is ω and the phase of the reconstructed back EMF zero-crossing signal leads the commutation point by an electrical angle of δ, then upon detecting the reconstructed back EMF zero-crossing (when the rising edge or falling edge arrives), delay compensation is performed, and the commutation point delay time t = δ / ω. That is, after a delay time t, the corresponding commutation point position is obtained.

[0043] The predictive compensation method is as follows: Calculate the difference between 180 degrees and the electrical angle (the electrical angle at which the back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor), and calculate the ratio of this difference to the electrical angular velocity to obtain the commutation point delay time at the next moment; after compensating the reconstructed back EMF zero-crossing signal with the commutation point delay time at the next moment, the commutation point signal is obtained. This compensation method corresponds to the commutation point leading the back EMF zero-crossing point. A schematic diagram of the specific predictive compensation is shown below. Figure 6As shown, signal A is one of the corresponding reconstructed back EMF zero-crossing signals, signal B is the desired commutation point position signal, and angle δ is the electrical angle by which the reconstructed back EMF zero-crossing signal lags behind the commutation point of the brushless DC motor. Taking the rising edge of the reconstructed back EMF zero-crossing as an example, when the rising edge of the reconstructed back EMF is detected, the commutation point cannot be obtained because it leads the reconstructed back EMF zero-crossing. However, both the reconstructed back EMF and the commutation point flip after 180° of electrical angle. Therefore, the commutation point action at the next moment can be predicted by collecting the reconstructed back EMF zero-crossing action at this moment. Figure 6 As shown, if the reconstructed back EMF zero-crossing signal A transitions from low to high at a certain moment, it can be predicted that the commutation point will transition from high to low after 180° - δ electrical angles. Therefore, based on this moment, when the reconstructed back EMF zero-crossing signal A transitions from low to high, a delay of 180° - δ electrical angles is made, and the corresponding level is flipped, i.e., the commutation point position signal at the next moment transitions from high to low. This process is repeated to predict the next commutation point by acquiring the reconstructed back EMF zero-crossing signal at a certain moment, achieving the purpose of advance phase compensation. Specifically, if the motor's electrical angular velocity is ω and the reconstructed back EMF zero-crossing signal lags the commutation point at that moment by an electrical angle of δ, then the commutation point delay time (also called the prediction compensation time) t = (180° - δ) / ω, meaning that the commutation point at the next moment is obtained after time t. Regarding the predictive compensation method, it should be noted that, due to variations in rotational speed, the calculated back EMF zero-crossing signal will either lead or lag behind the electrical angle of the brushless DC motor's commutation point. If the rotational speed changes between the current and next moment, the commutation point signal obtained at the next moment may contain errors. However, in practical applications, the motor typically operates at a stable speed, and even if a speed change occurs, it is unlikely to be sudden within a short period. Therefore, while the obtained commutation point signal at the next moment may contain errors, these errors are within an acceptable range and are negligible compared to the errors caused by the back EMF method commonly used in the background technology.

[0044] In step S105, based on the more accurate commutation point signal determined in the preceding steps, a suitable electromagnetic torque is applied to drive the motor. Because the commutation point position and its state are accurately obtained, the motor can operate better over a wider speed range without a position sensor.

[0045] As can be seen from the above description, in the brushless DC motor position control method of this application embodiment, the filtered back EMF zero-crossing signal is obtained. The filtered back EMF zero-crossing signal is the signal after the back EMF zero-crossing signal of the brushless DC motor is processed by a low-pass filter. The filtered back EMF zero-crossing signal is reconstructed by comparing it with a preset value signal to obtain the reconstructed back EMF zero-crossing signal. The reconstructed back EMF zero-crossing signal is calculated to lead or lag the electrical angle of the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor. Different compensation methods are selected according to the range of the electrical angle, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal. The brushless DC motor is controlled based on the commutation point signal. As can be seen, in the back EMF method in this application embodiment, the commutation point is not obtained by delaying the actual detected back EMF by 30° electrical angle. Instead, the electrical angle that the back EMF zero-crossing signal leads or lags behind the commutation point of the brushless DC motor is first calculated, and then the back EMF is compensated in different ways according to the electrical angle to finally obtain a more accurate commutation point.

[0046] Furthermore, in practical applications, because the calculated back EMF zero-crossing signal leads or lags the electrical angle of the brushless DC motor's commutation point differently depending on the rotational speed, the final compensated commutation point signal will also differ. Therefore, when the rotational speed remains constant, after calculating the commutation point signal for one cycle, continuous calculation is unnecessary. However, when the rotational speed changes, the commutation point signal can be updated. Specifically, this can be implemented by: determining whether the brushless DC motor's rotational speed has changed; if so, recalculating the new commutation point signal, following the method described above. Figure 2 The corresponding steps are performed; then the brushless DC motor is controlled according to the new commutation point signal.

[0047] Furthermore, such as Figure 7As shown in the figure, this application embodiment also provides a flowchart of a method for positionless control of a brushless DC motor. The specific implementation process is as follows: Start -- Hardware detection of back EMF zero-crossing point (detected by back EMF zero-crossing point detection circuit) -- Acquire the back EMF zero-crossing point signal into the MCU -- Software reconstruction of the new back EMF zero-crossing point signal (corresponding to step S102 above) -- Calculate the lead / delay angle δ between the reconstructed back EMF zero-crossing point signal and the commutation point (corresponding to step S103 above) -- Determine whether δ is greater than zero. If it is greater than zero, the commutation point signal is obtained by delay compensation (corresponding to the delay compensation method selected above, combined with the electric angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing point). The commutation point signal is obtained from the point signal. It should also be noted that the aforementioned compensation method was selected when δ was greater than zero and less than 30 degrees. Here, δ is greater than zero. Both methods are feasible in practical applications because, in practical applications, if the commutation point lags behind the zero-crossing point of the back EMF, the corresponding δ is usually less than 30° electrical angle. Therefore, the upper limit of δ here is not limited to 30° electrical angle, and the result is the same. -- If it is not greater than zero, the predictive compensation method is used for the commutation point signal (corresponding to the aforementioned selection of predictive compensation method, combined with the electric angular velocity of the brushless DC motor and the reconstructed zero-crossing signal of the back EMF to obtain the commutation point signal) -- The brushless DC motor position control is completed based on the commutation point signal -- End.

[0048] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0049] According to embodiments of this application, a method for implementing the above is also provided. Figure 2 The method of brushless DC motor without position control device 200, such as Figure 8As shown, the device includes: an acquisition unit 21, used to acquire a filtered back EMF zero-crossing signal, wherein the filtered back EMF zero-crossing signal is a signal processed by a low-pass filter after the back EMF zero-crossing signal of a brushless DC motor is processed; a reconstruction unit 22, used to reconstruct the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain a reconstructed back EMF zero-crossing signal; a calculation unit 23, used to calculate the electrical angle by which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor; a compensation unit 24, used to select different compensation methods according to the range of the electrical angle, and combine the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal to obtain the commutation point signal; and a control unit 25, used to control the brushless DC motor according to the commutation point signal.

[0050] Specifically, the detailed process by which each unit and module in the device of this application implements its function can be found in the relevant description in the method embodiment, and will not be repeated here.

[0051] As can be seen from the above description, in the brushless DC motor position control device of this application embodiment, the filtered back EMF zero-crossing signal is obtained. The filtered back EMF zero-crossing signal is the signal after the back EMF zero-crossing signal of the brushless DC motor has been processed by a low-pass filter. The filtered back EMF zero-crossing signal is reconstructed by comparing it with a preset value signal to obtain the reconstructed back EMF zero-crossing signal. The reconstructed back EMF zero-crossing signal is calculated to lead or lag the electrical angle of the commutation point of the brushless DC motor based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor. Different compensation methods are selected according to the range of the electrical angle, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal. The brushless DC motor is controlled based on the commutation point signal. As can be seen, in the back EMF method in this application embodiment, the commutation point is not obtained by delaying the actual detected back EMF by 30° electrical angle. Instead, the electrical angle that the back EMF zero-crossing signal leads or lags behind the commutation point of the brushless DC motor is first calculated, and then the back EMF is compensated in different ways according to the electrical angle to finally obtain a more accurate commutation point.

[0052] Furthermore, such as Figure 9As shown, the compensation unit 24 includes: a delay compensation module 241, used to select the delay compensation method when the electrical angle is greater than 0 degrees and less than 30 degrees, and to obtain the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal; and a prediction compensation module 242, used to select the prediction compensation method when the electrical angle is less than 0 degrees, and to obtain the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal.

[0053] Furthermore, such as Figure 9 As shown, the delay compensation module 241 is used to: calculate the ratio of the electrical angle to the electrical angular velocity to obtain the commutation point delay time; and obtain the commutation point signal by compensating the reconstructed back electromotive force zero-crossing signal with the delay time.

[0054] Furthermore, such as Figure 9 As shown, the prediction compensation module 242 is used to: calculate the difference between 180 degrees and the electrical angle, and calculate the ratio of the difference to the electrical angular velocity to obtain the commutation point delay time at the next moment; and obtain the commutation point signal by compensating the reconstructed back electromotive force zero-crossing signal with the commutation point delay time at the next moment.

[0055] Furthermore, such as Figure 9 As shown, the reconstruction unit 22 includes: a comparison module 221, used to compare the filtered back EMF zero-crossing signal with a preset value signal to obtain a comparison result; a first determination module 222, used to determine that if the comparison result is greater than zero, the reconstructed back EMF zero-crossing signal is at a high level; and a second determination module 223, used to determine that if the comparison result is less than zero, the reconstructed back EMF zero-crossing signal is at a low level.

[0056] Furthermore, such as Figure 9 As shown, the device further includes a detection unit 26, used to detect and acquire the back EMF zero-crossing signal through a back EMF zero-crossing detection circuit before acquiring the filtered back EMF zero-crossing signal.

[0057] Furthermore, such as Figure 9 As shown, the device further includes: a judgment unit 27, used to judge whether the speed of the brushless DC motor has changed; a calculation unit 23, used to recalculate a new commutation point signal if the speed changes; and a control unit 25, used to control the brushless DC motor according to the new commutation point signal.

[0058] Specifically, the detailed process by which each unit and module in the device of this application implements its function can be found in the relevant description in the method embodiment, and will not be repeated here.

[0059] According to an embodiment of this application, a computer-readable storage medium is also provided, characterized in that the computer-readable storage medium stores computer instructions, the computer instructions being used to cause the computer to execute the method for positionless control of a brushless DC motor in the above method embodiment.

[0060] According to an embodiment of this application, an electronic device is also provided, including: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores a computer program executable by the at least one processor, the computer program being executed by the at least one processor to cause the at least one processor to perform the brushless DC motor position control method in the above method embodiment.

[0061] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device, or fabricating them separately as individual integrated circuit modules, or fabricating multiple modules or steps as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0062] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for position control of a brushless DC motor, characterized in that, The method includes: The filtered back EMF zero-crossing signal is obtained, wherein the filtered back EMF zero-crossing signal is the signal after the back EMF zero-crossing signal of the brushless DC motor has been processed by a low-pass filter. The filtered back EMF zero-crossing signal is reconstructed by comparing it with a preset value signal to obtain the reconstructed back EMF zero-crossing signal. The step of reconstructing the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain a reconstructed back EMF zero-crossing signal includes: comparing the filtered back EMF zero-crossing signal with a preset value signal to obtain a comparison result; if the comparison result is greater than zero, the reconstructed back EMF zero-crossing signal is at a high level; if the comparison result is less than zero, the reconstructed back EMF zero-crossing signal is at a low level. The reconstructed back EMF zero-crossing signal is calculated based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor, indicating whether it leads or lags behind the electrical angle of the commutation point of the brushless DC motor. Different compensation methods are selected according to the range of the electrical angle, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the zero-crossing signal of the reconstructed back electromotive force. The step of selecting different compensation methods according to the range of the electrical angle and obtaining the commutation point signal in combination with the electrical angular velocity of the brushless DC motor includes: if the reconstructed back EMF zero-crossing signal leads or lags behind the electrical angle δ of the commutation point of the brushless DC motor by less than 0 degrees, that is, when the commutation point leads the back EMF zero-crossing point, then the predictive compensation method is selected. Specifically, if the reconstructed back EMF zero-crossing signal is detected to jump from low level to high level or from high level to low level, after a delay of (180°-δ) / ω, the commutation point at the next moment is obtained, and the level of the commutation point position signal at the next moment is flipped, where ω is the electrical angular velocity of the motor. The brushless DC motor is controlled based on the commutation point signal.

2. The method for position control of a brushless DC motor according to claim 1, characterized in that, The step of selecting different compensation methods based on the range of the electrical angle and obtaining the commutation point signal by combining the electrical angular velocity of the brushless DC motor includes: If the electrical angle is greater than 0 degrees and less than 30 degrees, then the delay compensation method is selected, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the zero-crossing signal of the reconstructed back electromotive force. If the electrical angle is less than 0 degrees, then the predictive compensation method is selected, and the commutation point signal is obtained by combining the electrical angular velocity of the brushless DC motor and the zero-crossing signal of the reconstructed back electromotive force.

3. The method for position control of a brushless DC motor according to claim 2, characterized in that, The method of selecting delay compensation, and obtaining the commutation point signal by combining the electric angular velocity of the brushless DC motor and the reconstructed back electromotive force zero-crossing signal, includes: The commutation point delay time is obtained by calculating the ratio of the electrical angle to the electrical angular velocity. The reconstructed back EMF zero-crossing signal is compensated for by the delay time to obtain the commutation point signal.

4. The method for position control of a brushless DC motor according to claim 1, characterized in that, The method further includes the following steps before acquiring the filtered back electromotive force zero-crossing signal: The zero-crossing signal of the back EMF is obtained by detecting the zero-crossing point of the back EMF through a back EMF zero-crossing point detection circuit.

5. The method for position control of a brushless DC motor according to claim 1, characterized in that, The method further includes: Determine whether the speed of the brushless DC motor has changed; If the rotational speed changes, the new commutation point signal is recalculated; The brushless DC motor is controlled based on the new commutation point signal.

6. A device for brushless DC motors without position control, characterized in that, The device includes: The acquisition unit is used to acquire the filtered back EMF zero-crossing signal, wherein the filtered back EMF zero-crossing signal is the signal after the back EMF zero-crossing signal of the brushless DC motor has been processed by a low-pass filter. The reconstruction unit is used to reconstruct the filtered back EMF zero-crossing signal by comparing it with a preset value signal to obtain a reconstructed back EMF zero-crossing signal. The reconstructing of the filtered back EMF zero-crossing signal by comparing it with the preset value signal includes: comparing the filtered back EMF zero-crossing signal with the preset value signal to obtain a comparison result; if the comparison result is greater than zero, the reconstructed back EMF zero-crossing signal is at a high level; if the comparison result is less than zero, the reconstructed back EMF zero-crossing signal is at a low level. The calculation unit is used to calculate, based on the transfer function of the low-pass filter and the electrical angular velocity of the brushless DC motor, the electrical angle at which the reconstructed back EMF zero-crossing signal leads or lags the commutation point of the brushless DC motor. The compensation unit is used to select different compensation methods according to the range of the electrical angle, and to obtain the commutation point signal by combining the electrical angular velocity of the brushless DC motor and the reconstructed back EMF zero-crossing signal. The selection of different compensation methods according to the range of the electrical angle and the obtaining of the commutation point signal by combining the electrical angular velocity of the brushless DC motor includes: if the reconstructed back EMF zero-crossing signal leads or lags the electrical angle δ of the commutation point of the brushless DC motor by less than 0 degrees, that is, when the commutation point leads the back EMF zero-crossing point, then the predictive compensation method is selected. Specifically, if the reconstructed back EMF zero-crossing signal is detected to jump from low level to high level or from high level to low level, after a delay of (180°-δ) / ω, the commutation point at the next moment is obtained, and the level of the commutation point position signal at the next moment is flipped, where ω is the electrical angular velocity of the motor. The control unit is used to control the brushless DC motor according to the commutation point signal.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to perform the method for positionless control of a brushless DC motor as described in any one of claims 1 to 5.

8. An electronic device, characterized in that, include: At least one processor; The at least one processor is also connected in communication with a memory, wherein the memory stores a computer program that can be executed by the at least one processor to cause the at least one processor to perform the method for positionless control of a brushless DC motor as described in any one of claims 1 to 5.

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