Rotor position detection method of brushless motor and detection system thereof

Abstract

The invention provides a rotor position detection method of a brushless motor and a detection system thereof. The method comprises the following steps: acquiring rotor position information through a back electromotive force zero-cross detection mode when the motor is started; determining the motion state of the rotor according to the rotor position information; and after the rotor enters the normal rotation state, switching the back electromotive force zero-cross detection mode into a Hall detection mode so as to continuously obtain the position information of the rotor. The position information of the rotor of the motor is obtained by adopting a sensorless detection mode, namely a back electromotive force zero-cross detection mode, after the rotation of the motor is kept stable, the Hall detection mode is switched to continue to obtain the position information of the rotor, so that the accurate position information of the rotor is obtained at the starting stage of the motor, and the reliability of the motor is improved. And after the motor stably rotates, the quiet operation of the motor is realized by executing sine wave driving.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a method for detecting the rotor position of a brushless motor and a system for detecting the rotor position of a brushless motor. Background Art

[0002] When a three-phase brushless DC motor is started, the rotor needs to be detected to obtain rotor position information for operations such as commutation.

[0003] Currently, common startup detection methods include three Hall sensors (using three Hall sensors to detect rotor motion), single Hall sensor (using a single Hall sensor to detect rotor motion), and sensorless detection (such as back-EMF zero-crossing detection). Compared to three Hall sensors, the single Hall sensor detection method offers the advantages of smaller footprint and lower cost, while compared to sensorless detection, it offers the advantages of quieter, lower-vibration operation.

[0004] However, the single Hall sensor startup detection method requires the rotor to reach a stable rotation state before obtaining accurate rotor position information, resulting in the inability to obtain accurate rotor information during the startup phase. At the same time, since the accuracy of the position information is per 180° electrical degree, the rotor rotation direction cannot be detected. Summary of the Invention

[0005] The present invention provides a brushless motor rotor position detection method and a brushless motor rotor position detection system to solve the problem in the prior art of using a Hall sensor detection method that cannot obtain accurate rotor information during the startup phase and cannot detect the rotor rotation direction. In order to solve the above technical problems, the present invention provides a rotor position detection method for a brushless motor, which is applied to a brushless motor that can obtain rotor position information through a back-electromotive force zero-crossing detection method and a Hall detection method respectively; the method includes: obtaining the rotor position information through a back-electromotive force zero-crossing detection method when the motor starts; confirming the motion state of the rotor based on the rotor position information; after the rotor enters a normal rotation state, switching from the back-electromotive force zero-crossing detection method to the Hall detection method to continue obtaining the rotor position information.

[0006] Furthermore, when the motor starts, the rotor position information is obtained by back electromotive force zero-crossing detection, including: obtaining the back electromotive force of each phase of the motor; recording the back electromotive force zero-crossing event, wherein the back electromotive force zero-crossing event is an event in which any opposite electromotive force of the motor crosses zero point; and obtaining the rotor position information based on the back electromotive force zero-crossing event.

[0007] Furthermore, the rotor position information is obtained based on the back electromotive force zero-crossing event, including: confirming whether a target number of the back electromotive force zero-crossing events occur continuously within a first preset time; if the target number of the back electromotive force zero-crossing events occur continuously within the first preset time, determining that the rotor is in a normal motion state; if the target number of the back electromotive force zero-crossing events do not occur continuously within the first preset time, continuing to record the back electromotive force zero-crossing events.

[0008] Furthermore, after the rotor enters the normal rotation state, the back electromotive force zero-crossing detection mode is switched to the Hall detection mode to continue to obtain the rotor position information, including: after the rotor enters the normal rotation state, determining whether the back electromotive force zero-crossing event occurs within a second preset time period; if the back electromotive force zero-crossing event does not occur within the second preset time period, it is determined that the rotor is in an abnormal rotation state, and the execution returns to the acquisition of the rotor position information by the back electromotive force zero-crossing detection mode when the motor is started; if the back electromotive force zero-crossing event occurs within the second preset time period, confirming whether the back electromotive force zero-crossing event is detected at the current moment. If the zero crossing condition is not detected at the current moment, the process returns to determine whether the back electromotive force zero crossing event occurs within the second preset time period. If the zero crossing condition is detected at the current moment, the process confirms whether it is the preset time point of the mode switching and whether the count value is above the preset threshold value. If it is at the preset time point of the mode switching and the count value is above the preset threshold value, the process switches to the Hall detection mode. If it is not at the preset time point of the mode switching and / or the count value is not above the preset threshold value, the process updates the count value or returns to determine whether the back electromotive force zero crossing event occurs within the second preset time period.

[0009] It should be noted that the abnormal rotation state of the rotor includes: stopping rotation and abnormal rotation speed.

[0010] Furthermore, updating the count value or returning to determine whether the back electromotive force zero-crossing event occurs within a second preset time period includes: confirming whether the current moment is in the preset polarity detection timing of the Hall signal; if it is not in the preset polarity detection timing, returning to determine whether the back electromotive force zero-crossing event occurs within the second preset time; if it is in the preset polarity detection timing, confirming whether the polarity of the Hall signal meets the expected polarity; if the polarity of the Hall signal does not meet the expected polarity, the count value is cleared; if the polarity of the Hall signal meets the expected polarity, the count value is increased by 1.

[0011] Furthermore, after switching to the Hall detection mode, the rotor position detection method also includes: after switching to the Hall detection mode, determining whether the edge of the Hall signal is detected within a third preset time period; if the edge of the Hall signal is detected, continuing to obtain the rotor position information through the Hall detection mode; if the edge of the Hall signal is not detected, determining that the rotor is in an abnormal rotation state, and switching to the back electromotive force zero-crossing detection mode to obtain the rotor position information.

[0012] Furthermore, the Hall signal is a binary signal.

[0013] Furthermore, the preset polarity detection timing includes a time point when each phase electromotive force of the motor is zero.

[0014] The present invention also provides a rotor position detection device for a brushless motor, wherein the brushless motor can obtain rotor position information through a back electromotive force zero-crossing detection method and a Hall detection method respectively. The rotor position detection device includes: an acquisition unit, used to obtain the rotor position information through a back electromotive force zero-crossing detection method when the motor starts; a confirmation unit, used to confirm the motion state of the rotor based on the rotor position information; and a switching unit, used to switch from the back electromotive force zero-crossing detection method to the Hall detection method after the rotor enters a normal rotation state, so as to continue to obtain the rotor position information.

[0015] The present invention also provides a rotor position detection system for a brushless motor, comprising: a motor body, wherein the motor body is provided with a U-phase winding, a V-phase winding, and a W-phase winding; a motor controller, wherein the motor controller is electrically connected to the U-phase winding, the V-phase winding, and the W-phase winding, respectively, for driving the motor to rotate; a Hall sensor, which is arranged between the W-phase winding and the U-phase winding and is directly opposite to the V-phase winding, for outputting a Hall sensing signal in response to the rotation of the motor; a Hall signal generator, wherein the Hall signal generator is electrically connected to the Hall sensor, and is used to output a Hall signal according to the Hall sensing signal; and a counter-electric A back electromotive force zero-crossing detector, the back electromotive force zero-crossing detector is electrically connected to the U-phase winding, the V-phase winding and the W-phase winding, and is used to perform back electromotive force zero-crossing detection on each phase winding and output a back electromotive force zero-crossing detection signal and a steering signal; a rotor position detector, the rotor position detector is electrically connected to the Hall signal generator, the back electromotive force zero-crossing detector and the motor controller, and is used to obtain the steering signal, the back electromotive force zero-crossing detection signal and the Hall signal, and obtain rotor position information through the back electromotive force zero-crossing detection signal or the Hall signal; a Hall signal polarity detector Hall a signal polarity confirmer, wherein the Hall signal polarity detector is electrically connected to the rotor position detector, the Hall signal generator and the back electromotive force zero-crossing detector, respectively, and is used to obtain the Hall signal, the steering signal, the back electromotive force zero-crossing detection signal and the rotor position information, and is used to respond to the Hall signal, the steering signal, the back electromotive force zero-crossing detection signal and the rotor position information and respond to each received signal and the rotor position information to determine whether a switching condition is met, and output a mode switching signal when the switching condition is met; and a state controller, wherein the state controller is electrically connected to the Hall signal generator, the back electromotive force zero-crossing detector, the rotor position detector, the motor controller and the Hall signal polarity confirmer, respectively, and is used to drive the Hall signal generator, the back electromotive force zero-crossing detector, the rotor position detector, the motor controller and the Hall signal polarity confirmer to work, and obtain the mode switching signal to drive the rotor position detector according to the mode switching signal so that the rotor position detector switches between the back electromotive force zero-crossing detection mode and the Hall detection mode.

[0016] Furthermore, the Hall signal polarity detector Hall signal polarity confirmer includes: a judge, which is electrically connected to the rotor position detector, the Hall signal generator and the back electromotive force zero-crossing detector, respectively, for obtaining the steering signal, the back electromotive force zero-crossing detection signal, the Hall signal and the rotor position information, and making a judgment on the steering signal, the back electromotive force zero-crossing detection signal, the Hall signal and the rotor position information, and generating a judgment result information and a counting signal; a counter, which is electrically connected to the state controller and the judge, respectively, for confirming the motion state of the motor, and counting or clearing according to the counting signal, and outputting an updated count value; a mode switching signal generator, the mode switching signal generating module is electrically connected to the judge, the counter and the state controller, respectively, for generating the mode switching signal according to the judgment result information and the counting value, and sending the mode switching signal to the state controller to enable the state controller to switch between the back electromotive force zero-crossing detection mode and the Hall detection mode.

[0017] The beneficial effects of the present invention are as follows: the present application adopts a sensorless detection method during the motor startup phase, that is, adopts a back electromotive force zero-crossing detection method to obtain the motor rotor position information, and switches to a Hall detection method after the motor rotation remains stable to continue to obtain the rotor position information, thereby ensuring that accurate rotor position information is obtained during the motor startup phase, and after the motor rotates stably, the quiet operation of the motor is achieved by executing sinusoidal wave drive.

[0018] Furthermore, the present application adopts two detection methods, which realize the switching from the back electromotive force zero-crossing detection method to the Hall detection method during the initial stage of motor startup to the stable rotation process. When the Hall sensor has an abnormality, it can also realize the switching from the Hall detection method to the back electromotive force zero-crossing detection method to improve the reliability of the brushless motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a first flow chart of a brushless motor rotor detection method according to a first embodiment of the present invention; Figure 2 This is a specific flow chart of step S1 in the first embodiment of the present invention; Figure 3 This is a specific flow chart of step S2 in the first embodiment of the present invention; Figure 4 This is a specific flow chart of step S3 in the first embodiment of the present invention; Figure 5 This is a specific flow chart of step S34b of the first embodiment of the present invention; Figure 6This is a flowchart of the subsequent steps of step S34a in the first embodiment of the present invention; Figure 7 This is a principle block diagram of a rotor detection system for a brushless motor according to a second embodiment of the present invention; Figure 8 This is a functional block diagram of a Hall signal polarity confirmer according to a second embodiment of the present invention; Figure 9 Schematic diagram of the working process of the rotor detection system of the brushless motor according to the second embodiment of the present invention; Figure 10 Schematic diagram of the relationship between each back electromotive force, Hall signal, polarity detection timing, and mode switching timing under normal conditions in an embodiment of the present invention; Figure 11 This is a table showing the correspondence between polarity detection timing, mode switching timing, and expected polarity under normal circumstances in an embodiment of the present invention; Figure 12 Schematic diagram of the relationship between each back electromotive force, Hall signal, polarity detection timing, and mode switching timing in the case of Hall signal jitter in an embodiment of the present invention; Figure 13 The embodiment of the present invention considers the correspondence table of polarity detection timing, mode switching timing and expected polarity when the Hall signal jitter occurs.

[0020] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0021] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] Those skilled in the art will appreciate that, unless expressly stated otherwise, the singular forms "a", "an", "said", "above", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the described features, integers, steps, operations, elements, units, modules, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, units, modules, components, and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, "connected" or "coupled" as used herein may include wireless connections or wireless couplings. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0023] Those skilled in the art will understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which this invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless specifically defined as such, will not be interpreted in an idealized or overly formal sense.

[0024] Example 1 Please refer to Figure 1 This embodiment provides a method for detecting the rotor position of a brushless motor. The method is applied to a brushless motor that can obtain rotor position information through back electromotive force zero-crossing detection and Hall detection, such as a three-phase brushless motor.

[0025] The method comprises the steps of: S1. When the motor starts, the rotor position information is obtained by detecting the zero crossing of the back electromotive force.

[0026] In this step, the rotor position information includes the rotor starting position, the rotor running position, the rotor rotation angular velocity, etc.

[0027] S2. Confirm the motion state of the rotor according to the rotor position information.

[0028] In this step, the motion state of the rotor includes the rotor rotating normally, the rotor stopping rotating, the rotor starting rotating, etc.

[0029] S3. After the rotor enters a normal rotation state, the back electromotive force zero-crossing detection mode is switched to the Hall detection mode to continue acquiring the rotor position information.

[0030] In this step, a single Hall sensor is used to detect the magnitude of the magnetic field and output a Hall signal.

[0031] In the prior art, during the startup of a brushless motor, if the target speed is not reached using a single Hall detection method, the Hall sensor cannot obtain an effective and usable Hall sensing signal. Moreover, a single Hall sensor can only output a Hall sensing signal when the rotor's sensing magnet approaches. Therefore, it can only detect the rotor position information and cannot infer the rotor's direction of rotation by combining other information.

[0032] The rotor position detection method of this embodiment uses back-EMF zero-crossing detection to obtain rotor position information during the initial motor startup phase. Specifically, as the motor rotates, each winding generates a back-EMF voltage (BEMF). This back-EMF signal is used to determine the rotor position and, as a basis for commutation, to determine the rotor position. Compared to a single Hall sensor approach, this method ensures accurate rotor position information during startup while also enabling the acquisition of rotor direction information. Once the rotor is rotating normally, the back-EMF zero-crossing detection method is switched to Hall detection, using a single Hall sensor to obtain Hall signals to continue acquiring rotor position information. This results in quieter motor operation and lower vibration compared to using back-EMF zero-crossing detection.

[0033] As you can understand, the detection method employed in this embodiment cleverly combines sensorless and Hall-effect detection methods to ensure accurate rotor position information from motor startup to stable rotation. Furthermore, if a Hall-effect sensor anomaly occurs, Hall-effect detection can be switched to back-EMF zero-crossing detection, thereby improving the reliability of the brushless motor.

[0034] In some embodiments, see Figure 2 , step S1 includes: S11, obtaining the back electromotive force of each phase of the motor; S12, recording the back electromotive force zero crossing event; The back EMF zero-crossing event is an event in which any back EMF of the motor crosses zero. For example, a back EMF zero-crossing detection signal can be output when each back EMF crosses zero, thereby recording the back EMF zero-crossing event. The back EMF zero-crossing detection can be implemented using a comparator or a comparison circuit.

[0035] S13. Obtain the rotor position information according to the back electromotive force zero-crossing event.

[0036] It can be understood that accurate rotor position information can be obtained by using the back electromotive force zero-crossing detection method at the initial stage of motor startup.

[0037] In some embodiments, see Figure 3 , step S2 includes: S21, confirm whether the target number of back electromotive force zero-crossing events occur continuously within a first preset time, if so, execute step S22a, if not, execute step S22b; S22a, determining that the rotor is in a normal motion state; S22b, returning to step S12 (continuing to record the back electromotive force zero-crossing event).

[0038] In this embodiment, if the back electromotive force zero-crossing event occurs continuously, the motor is in a rotating state; if the back electromotive force zero-crossing event does not occur, the motor is in a stopped state; if the back electromotive force zero-crossing event does not reach the target number continuously occurring within the first preset time, the motor does not reach a normal and stable rotation state; if the back electromotive force zero-crossing event reaches the target number continuously occurring within the first preset time, the motor maintains a normal and stable rotation state.

[0039] It can be understood that when the motor rotates normally, the speed is stable, the commutation is normal, and back electromotive force zero-crossing events occur alternately in each phase. At this time, the number of back electromotive force zero-crossing events occurring within the first preset time is certain, so the motion state of the rotor can be confirmed by the above method.

[0040] In some embodiments, an initialized count value is preset, and illustratively, the count value is reset to zero. Figure 4 , step S3 includes: S31, after the rotor enters a normal rotation state, determining whether the back electromotive force zero-crossing event occurs within a second preset time period; if not, executing step S32a; if so, executing step S32b; S32a, determining that the rotor is in an abnormal rotation state, and returning to step S1; S32b, confirm whether the back electromotive force is detected to be zero-crossing at the current moment, if not, execute step S33a, if so, execute step S33b; S33a, return to step S31, S33b, confirm whether it is the preset mode switching time point and whether the count value is above the preset threshold value. If so, execute step S34a; if not, execute step S34b; In this step, a mode switching timing is provided. In this embodiment, it is confirmed at the mode switching timing whether the count value is greater than or equal to a preset count threshold. Exemplarily, the mode switching timing includes the time point when the back electromotive force of one phase of the motor passes through zero. In this embodiment, the time point when the back electromotive force of V passes through zero is used as the time point of the mode switching timing, and there is no limitation in other embodiments.

[0041] S34a, switching to Hall detection mode; S34b: Update the count value, or return to step S31.

[0042] Before this step, the method also includes: obtaining a Hall signal, and further obtaining the polarity of the Hall signal.

[0043] As will be appreciated, this embodiment determines, through step S31, whether the motor maintains normal rotation within a second preset time period after the rotor enters the normal rotation state. Furthermore, steps S32a and S32b determine whether the back EMF at the current moment crosses zero, thereby determining whether to switch to the Hall detection mode. In steps S33a and S33b of this embodiment, the count value is used to determine whether the switching condition is met, that is, whether the Hall signal is available before switching to the Hall detection mode. If the condition is met, the switch is implemented through step S34a. If the condition is not met, step S34b is continued to ensure that the Hall signal is available before switching to the Hall detection mode.

[0044] Please refer to Figure 5 , step S34b includes the steps of: S342: Determine whether the current moment is the preset polarity detection time of the Hall signal. If not, execute step S343a; if so, execute step S343b; S343a, return to step S31; S343b, confirm whether the polarity of the Hall signal meets the expected polarity; if not, execute step S344a; if so, execute step S344b; S344a, the count value is cleared; S344b, the count value is increased by 1.

[0045] It is understood that if the polarity of the Hall signal meets the expected polarity at any polarity detection timing, it can be confirmed that the Hall signal at that polarity detection timing is usable. Correspondingly, if the polarity of the Hall signal meets the corresponding expected polarity at consecutive polarity detection timings, that is, the Hall signal detection continuously obtains the expected polarity, it can be confirmed that the Hall signal is stable and usable. At this time, the operation of switching from the back-EMF zero-crossing detection mode to the Hall detection mode can be performed. This embodiment uses counting and comparing with a preset counting threshold to determine whether the Hall signal is usable before switching to the Hall detection mode, thereby ensuring the accuracy of the detected rotor position information.

[0046] In some embodiments, see Figure 6 , after step S34a, the following steps are included: S35, after switching to the Hall detection mode, determining whether an edge of the Hall signal is detected within a third preset time period, if not, executing step S36a, if so, executing step S36b; S36a, determining that the rotor is in an abnormal rotation state, switching to a back electromotive force zero-crossing detection mode to obtain the rotor position information; S36b, continue to obtain the rotor position information through Hall detection.

[0047] It can be understood that after switching to the Hall detection mode, the Hall signal continues to be detected. When the edge (rising edge or falling edge) of the Hall signal cannot be detected, it is determined that the Hall sensor has entered a preset state, which includes but is not limited to the abnormal state of the motor, the normal stop of the motor, and the stop state due to external force. At this time, switching to the back electromotive force zero-crossing detection mode is carried out to continue to obtain the motor rotor position information, which is beneficial to improving the reliability of the motor.

[0048] In some embodiments, the Hall signal is a binary signal. It is understandable that the Hall signal obtained in this embodiment is a square wave signal or a quasi-square wave signal, that is, the Hall signal has two polarities: high level and low level.

[0049] In some embodiments, the polarity detection timing includes the time when the back electromotive force of each phase of the motor reaches zero. Optionally, the polarity of the Hall signal is detected when the back electromotive force of one or more of the motor phases U, V, and W passes through zero, and the corresponding expected polarity is provided for comparison.

[0050] It can be understood that in this embodiment, by performing polarity detection on the Hall signal when the back electromotive force of each motor is zero, it is helpful to determine the expected polarity of the Hall signal.

[0051] Example 2 This embodiment further provides a brushless motor rotor position detection system, which applies the brushless motor rotor position detection method described in the first embodiment.

[0052] Please refer to Figure 7 , the rotor position detection system of the brushless motor includes: The motor body 100 is provided with a U-phase winding, a V-phase winding, and a W-phase winding; a motor controller 300 , the motor controller 300 being electrically connected to the U-phase winding, the V-phase winding, and the W-phase winding, respectively, for driving the motor to rotate; A Hall sensor 200 is provided between the W-phase winding and the U-phase winding and directly opposite the V-phase winding, and is configured to output a Hall sensing signal in response to the rotation of the motor; A Hall signal generator 400 , electrically connected to the Hall sensor 200 , configured to output a Hall signal according to the Hall sensing signal; a back electromotive force zero-crossing detector 500, the back electromotive force zero-crossing detector 500 being electrically connected to the U-phase winding, the V-phase winding, and the W-phase winding, for performing back electromotive force zero-crossing detection on each phase winding and outputting a back electromotive force zero-crossing detection signal and a steering signal; a rotor position detector 600, the rotor position detector 600 being electrically connected to the Hall signal generator 400, the back-EMF zero-crossing detector 500, and the motor controller 300, respectively, for acquiring the steering signal, the back-EMF zero-crossing detection signal, and the Hall signal, and obtaining rotor position information through the back-EMF zero-crossing detection signal or the Hall signal; a Hall signal polarity confirmer 700, the Hall signal polarity confirmer 700 being electrically connected to the rotor position detector 600, the Hall signal generator, and the back-electromotive force zero-crossing detector, respectively, for obtaining the Hall signal, the steering signal, the back-electromotive force zero-crossing detection signal, and the rotor position information, and determining whether a switching condition is satisfied in response to each received signal and the rotor position information, and outputting a mode switching signal when the switching condition is satisfied; and The state controller 800 is electrically connected to the Hall signal generator 400, the back electromotive force zero-crossing detector 500, the rotor position detector 600, the motor controller 300 and the Hall signal polarity confirmer 700, respectively, and is used to drive the Hall signal generator 400, the back electromotive force zero-crossing detector 500, the rotor position detector 600, the motor controller 300 and the Hall signal polarity confirmer 700 to operate, and obtain the mode switching signal, and drive the rotor position detector 600 according to the mode switching signal, so that the rotor position detector 600 switches between the back electromotive force zero-crossing detection mode and the Hall detection mode.

[0053] The working principle of the rotor detection system of the brushless motor of this embodiment is as follows: the state controller 800 is used to drive the operation of the other components to achieve drive control of the motor. The Hall sensor 200 provides a Hall sensing signal in response to the rotation of the motor winding, and the Hall signal generator 400 generates a Hall signal in response to the Hall sensing signal. The back electromotive force zero-crossing detector 500 respectively obtains the back electromotive force of each phase winding of the motor and outputs a back electromotive force zero-crossing detection signal and a steering signal when the back electromotive force crosses zero. The rotor position detector 600 obtains the back electromotive force zero-crossing detection signal, the Hall signal, and the steering signal to obtain rotor position information. The Hall signal polarity confirmer 700 generates a mode switching signal in response to the Hall signal, the steering signal, the back electromotive force zero-crossing detection signal, and the rotor position information.

[0054] Exemplarily, a mode switching timing is preset. The Hall signal polarity confirmer obtains the rotor's motion state from the rotor position information, confirms the rotor's direction of rotation from the steering signal, obtains the Hall signal polarity detection timing from the back-EMF zero-crossing detection signal and provides an expected polarity, performs polarity detection on the Hall signal, compares the polarity at the polarity detection timing with the expected polarity, and determines whether the switching condition is met based on the comparison result, thereby outputting a mode switching signal. The state controller 800 adjusts the drive of each component based on the mode switching signal to change the rotor position information detection method. Exemplarily, the motor is started using the back-EMF zero-crossing detection method. When the rotor rotates normally and the Hall signal meets the switching condition, the state controller 800 switches to the Hall detection method in response to the mode switching signal.

[0055] This embodiment utilizes a Hall signal polarity confirmer to obtain rotor position information, Hall signals, and back-EMF zero-crossing detection signals. This information is then used for judgment and comparison to generate a detection mode switch signal. This allows the motor to detect rotor position information using back-EMF zero-crossing detection during startup. After the motor rotates normally, it switches to Hall detection to continue detecting rotor position information, ensuring accurate rotor position information during startup. Once the motor stabilizes, sinusoidal drive is implemented to achieve quiet operation.

[0056] In addition, when an abnormality occurs in the Hall detection method, the rotor position information can still be detected by switching to the back electromotive force detection method to improve the reliability of the brushless motor.

[0057] In some embodiments, see Figure 8 , the Hall signal polarity confirmer comprises: a determiner 710, the determiner 710 being electrically connected to the rotor position detector 600, the Hall signal generator, and the back-electromotive force zero-crossing detector, respectively, and configured to obtain the steering signal, the back-electromotive force zero-crossing detection signal, the Hall signal, and the rotor position information, make a determination on the steering signal, the back-electromotive force zero-crossing detection signal, the Hall signal, and the rotor position information, and generate determination result information and a counting signal; a counter 720 , the counter 720 being electrically connected to the state controller 800 and the determiner 710 , for confirming the motion state of the motor, counting according to the counting signal, and outputting an updated count value; The mode switching signal generator 730, the mode switching signal generating module is electrically connected to the judge 710, the counter 720 and the state controller 800, respectively, and is used to generate the mode switching signal according to the judgment result information and the count value, and send the mode switching signal to the state controller 800, so that the state controller 800 switches between the back electromotive force zero-crossing detection mode and the Hall detection mode.

[0058] In this embodiment, the determination of the determiner 710 includes confirming the rotor's motion state through the rotor position information, confirming the rotor's direction of rotation through the direction signal, confirming the zero-crossing detection timing through the back-electromotive force zero-crossing detection signal, and confirming the polarity of the Hall signal through the Hall signal. The determination of the determiner 710 also includes: Determining whether a target number of back-electromotive force zero-crossing events occur consecutively within a first preset time period, and determining whether a back-electromotive force zero-crossing event occurs within a second preset time period after the rotor enters a normal rotation state. Exemplarily, determining a back-electromotive force zero-crossing event is performed by using a back-electromotive force zero-crossing detection signal.

[0059] Confirm whether a back EMF zero crossing is detected at the current moment. For example, if a target number of back EMF zero crossing events occur consecutively within a first preset time period, and a back EMF zero crossing event occurs within a second preset time period, then confirm whether a back EMF zero crossing is detected. Determine whether the count value is greater than or equal to a preset count threshold. For example, the counter is preset with a count value for reset and initialization. The determiner outputs a count signal based on the polarity detection result to reset or increment the count value. After updating the count value, the count value is compared with the preset count threshold. When the count value is greater than or equal to the preset count threshold, the mode switching signal generator generates a mode switching signal. When the count value is less than the preset count threshold, the mode switching signal generator issues a count signal and compares the next updated count value with the preset count threshold.

[0060] Confirm whether the polarity of the Hall signal at the polarity detection timing meets the expected polarity. Exemplarily, the polarity detection timing and the expected polarity are preset, the polarity of the Hall signal at the polarity detection timing is obtained, the polarity of the Hall signal is compared with the expected polarity, and a corresponding comparison result is output. Exemplarily, when the polarity of the Hall signal does not meet the expected polarity, the counting signal output by the judgement unit 710 is used to clear the count value, and when the polarity of the Hall signal meets the expected polarity, the counting signal output by the judgement unit 710 is used to increase the count value by 1.

[0061] It can be understood that the counter 720 of this embodiment is used to count the comparison results of the polarity of the Hall signal and the expected polarity respectively. For example, a count value that has been initialized and cleared is provided. If the polarity of the Hall signal does not meet the expected polarity, the count value is cleared. If the polarity of the Hall signal meets the expected polarity, the count value is increased by 1.

[0062] Furthermore, the mode switching signal generator of this embodiment generates a mode switching signal based on the determination result of determiner 710 and the count value, and outputs the mode switching signal to state controller 800, thereby causing state controller 800 to adjust the driving of various components to switch the rotor position detection method. For example, when the rotor is rotating normally, if a zero crossing is detected, and the polarity of the continuously obtained Hall effect signals all meet the expected polarity, the mode switching signal is sent to state controller 800 at the mode switching opportunity.

[0063] For example, please refer to Figure 9 The steps of the brushless motor rotor position detection system of this embodiment are as follows: A1. Rotor position detection starts; A2. Enter the back electromotive force zero-crossing detection mode; In this step, the rotor position information is detected by back electromotive force zero-crossing detection; A3. Provide the count value and reset it to zero; A4, determining whether the back electromotive force is continuously detected to be zero-crossing within the first preset time, if so, executing step A5, if not, continuing the back electromotive force zero-crossing detection; A5. Determining that the rotor is in a normal motion state; A6. After the rotor enters a normal rotation state, determining whether the back electromotive force zero-crossing event occurs within a second preset time period; if not, executing step A15; if so, executing step A7; A7, confirm whether the back electromotive force is detected to be zero-crossing at the current moment, if so, execute step A8, if not, return to execute step A6; A8. Determine whether it is the preset mode switching time point and whether the count value is above the preset threshold. If so, execute step A13; if not, execute step A9; A9, determine whether it is the time to detect the polarity of the Hall signal. If so, execute step A10. If not, return to step A6. A10, determining whether the polarity of the Hall signal meets the expected polarity, if so, executing step A11, if not, executing step A12; A11, count value plus 1; A12, count value cleared; A13, enter single Hall detection mode; In this step, switch to Hall detection mode to continue obtaining rotor position information; A14. After switching to the Hall detection mode, determine whether an edge of the Hall signal is detected within a third preset time period. If not, execute step A15. If so, continue detecting the edge of the Hall signal. A15. Determine whether the rotor is in an abnormal rotation state.

[0064] For example, please refer to Figure 10 and Figure 11 This embodiment provides schematic diagrams of the back EMFs and Hall effect signals for each motor's forward and reverse downward rotation, along with the corresponding polarity detection timing, mode detection timing settings, and the expected polarity for each polarity detection timing. For example, the polarity detection timing is the time when each back EMF crosses zero, and the mode switching timing is the time when the V back EMF crosses zero.

[0065] Please refer to Figure 12 and Figure 13 To prevent Hall signal jitter from affecting detection results, this embodiment adjusts the polarity detection timing and mode detection timing. This embodiment provides schematic diagrams of the back EMF and Hall signal for each of the forward and reverse motor rotations in the presence of Hall signal jitter, along with the corresponding polarity detection timing, mode detection timing settings, and the expected polarity of the corresponding polarity detection timing. For example, the polarity detection timing is the time when the back EMF of the V phase crosses zero, and the mode switching timing is the time when the back EMF of the V phase crosses zero.

[0066] In summary, the present invention provides a rotor position detection method and detection system for a brushless motor, which adopts a sensorless detection method during the motor startup phase, that is, adopts a back electromotive force zero-crossing detection method to obtain the motor rotor position information, and switches to a Hall detection method after the motor rotation remains stable to continue to obtain the rotor position information, thereby ensuring that accurate rotor position information is obtained during the motor startup phase, and after the motor rotates stably, the quiet operation of the motor is achieved by executing sinusoidal wave drive.

[0067] Furthermore, the present application adopts two detection methods, which realize the switching from the back electromotive force zero-crossing detection method to the Hall detection method during the initial stage of motor startup to the stable rotation process. When the Hall sensor has an abnormality, it can also realize the switching from the Hall detection method to the back electromotive force zero-crossing detection method to improve the reliability of the brushless motor.

[0068] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for detecting the rotor position of a brushless motor, characterized in that: The method is applied to a brushless motor capable of obtaining rotor position information by back electromotive force zero-crossing detection and Hall detection, and comprises the following steps: When the motor starts, the rotor position information is obtained by detecting the zero crossing of the back electromotive force; confirming the motion state of the rotor according to the rotor position information; After the rotor enters a normal rotation state, the back electromotive force zero-crossing detection mode is switched to the Hall detection mode to continue to obtain the rotor position information.

2. The method for detecting the rotor position of a brushless motor according to claim 1, wherein: When the motor starts, the rotor position information is obtained by back electromotive force zero-crossing detection, including: Obtaining the back electromotive force of each phase of the motor; Recording a back electromotive force zero-crossing event, wherein the back electromotive force zero-crossing event is an event in which any back electromotive force of the motor crosses a zero point; The rotor position information is obtained according to the back electromotive force zero-crossing event.

3. The method for detecting the rotor position of a brushless motor according to claim 2, wherein: Obtaining the rotor position information according to the back electromotive force zero-crossing event includes: confirming whether a target number of back electromotive force zero-crossing events occur continuously within a first preset time; If a target number of back electromotive force zero-crossing events occur continuously within a first preset time, it is determined that the rotor is in a normal motion state; If the target number of back electromotive force zero-crossing events does not occur continuously within the first preset time, the back electromotive force zero-crossing events are continuously recorded.

4. The method for detecting the rotor position of a brushless motor according to claim 3, wherein: After the rotor enters a normal rotation state, the back electromotive force zero-crossing detection mode is switched to the Hall detection mode to continue to obtain the rotor position information, including: After the rotor enters a normal rotation state, determining whether the back electromotive force zero-crossing event occurs within a second preset time period; If the back electromotive force zero-crossing event does not occur within the second preset time period, it is determined that the rotor is in an abnormal rotation state, and the process returns to executing the method of obtaining the rotor position information by using the back electromotive force zero-crossing detection method when the motor is started; If the back electromotive force zero crossing event occurs within the second preset time period, confirm whether the back electromotive force zero crossing is detected at the current moment; if no zero crossing is detected at the current moment, return to determine whether the back electromotive force zero crossing event occurs within the second preset time period; if a zero crossing is detected at the current moment, confirm whether it is a preset mode switching time point and whether the count value is above a preset threshold; If it is at a preset mode switching time point and the count value is above a preset threshold, it switches to the Hall detection mode; if it is not at a preset mode switching time point and / or the count value is not above the preset threshold, it updates the count value or returns to determine whether the back electromotive force zero crossing event occurs within a second preset time period.

5. The method for detecting the rotor position of a brushless motor according to claim 4, wherein: Updating the count value or returning to determine whether the back electromotive force zero-crossing event occurs within a second preset time period includes: Confirm whether the current moment is at the preset polarity detection time of the Hall signal; If it is not the preset polarity detection time, returning to the step of determining whether the back electromotive force zero-crossing event occurs within a second preset time; If the preset polarity detection timing has occurred, it is confirmed whether the polarity of the Hall signal meets the expected polarity. If the polarity of the Hall signal does not meet the expected polarity, the count value is reset to zero; if the polarity of the Hall signal meets the expected polarity, the count value is increased by 1.

6. The method for detecting the rotor position of a brushless motor according to claim 4, wherein: After switching to the Hall detection mode, the rotor position detection method further includes: After switching to the Hall detection mode, determining whether an edge of the Hall signal is detected within a third preset time period; If an edge of the Hall signal is detected, the rotor position information is obtained by continuing to use the Hall detection method; If no edge of the Hall signal is detected, it is determined that the rotor is in an abnormal rotation state, and the back electromotive force zero-crossing detection mode is switched.

7. The method for detecting the rotor position of a brushless motor according to claim 4, wherein: The Hall signal is a binary signal; and / or the preset polarity detection timing includes a time point when the back electromotive force of each motor is zero.

8. A brushless motor rotor position detection device, characterized in that: The brushless motor can obtain rotor position information by back electromotive force zero-crossing detection and Hall detection, and the rotor position detection device includes: an acquisition unit, configured to acquire the rotor position information by back electromotive force zero-crossing detection when the motor is started; a confirmation unit, configured to confirm a motion state of the rotor according to the rotor position information; The switching unit is used to switch from the back electromotive force zero-crossing detection mode to the Hall detection mode after the rotor enters the normal rotation state, so as to continue to obtain the rotor position information.

9. A brushless motor rotor position detection system, characterized in that: include: a motor body, wherein the motor body is provided with a U-phase winding, a V-phase winding, and a W-phase winding; a motor controller, the motor controller being electrically connected to the U-phase winding, the V-phase winding, and the W-phase winding, respectively, for driving the motor to rotate; a Hall sensor, disposed between the W-phase winding and the U-phase winding and facing the V-phase winding, for outputting a Hall sensing signal in response to rotation of the motor; a Hall signal generator, the Hall signal generator being electrically connected to the Hall sensor and configured to output a Hall signal according to the Hall sensing signal; a back electromotive force zero-crossing detector, the back electromotive force zero-crossing detector being electrically connected to the U-phase winding, the V-phase winding, and the W-phase winding, for performing back electromotive force zero-crossing detection on each phase winding and outputting a back electromotive force zero-crossing detection signal and a steering signal; a rotor position detector, the rotor position detector being electrically connected to the Hall signal generator, the back-electromotive force zero-crossing detector, and the motor controller, respectively, and being configured to obtain the steering signal, the back-electromotive force zero-crossing detection signal, and the Hall signal, and to obtain rotor position information through the back-electromotive force zero-crossing detection signal or the Hall signal; a Hall signal polarity confirmer, the Hall signal polarity confirmer being electrically connected to the rotor position detector, the Hall signal generator, and the back electromotive force zero-crossing detector, respectively, for acquiring the Hall signal, the steering signal, the back electromotive force zero-crossing detection signal, and the rotor position information, and determining whether a switching condition is satisfied in response to each received signal and the rotor position information, and outputting a mode switching signal when the switching condition is satisfied; as well as A state controller, wherein the state controller is electrically connected to the Hall signal generator, the back electromotive force zero-crossing detector, the rotor position detector, the motor controller and the Hall signal polarity confirmer, respectively, and is used to drive the Hall signal generator, the back electromotive force zero-crossing detector, the rotor position detector, the motor controller and the Hall signal polarity confirmer to operate, and obtain the mode switching signal, and drive the rotor position detector according to the mode switching signal to enable the rotor position detector to switch between the back electromotive force zero-crossing detection mode and the Hall detection mode.

10. The rotor position detection system of a brushless motor according to claim 9, wherein: The Hall signal polarity confirmer comprises: a judger, the judger being electrically connected to the rotor position detector, the Hall signal generator, and the back electromotive force zero-crossing detector, respectively, and being configured to obtain the steering signal, the back electromotive force zero-crossing detection signal, the Hall signal, and the rotor position information, make a judgment on the steering signal, the back electromotive force zero-crossing detection signal, the Hall signal, and the rotor position information, and generate judgment result information and a counting signal; a counter, the counter being electrically connected to the state controller and the determiner, for confirming the motion state of the motor, counting or clearing according to the counting signal, and outputting an updated count value; A mode switching signal generator, wherein the mode switching signal generating module is electrically connected to the judge, the counter and the state controller respectively, and is used to generate the mode switching signal according to the judgment result information and the count value, and send the mode switching signal to the state controller to enable the state controller to switch between the back electromotive force zero-crossing detection mode and the Hall detection mode.

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