Commutation control method, computer program product and non-inductive brushless motor system

Abstract

The invention relates to a commutation control method for a non-inductive brushless motor, and the method comprises the following steps: detecting a first terminal voltage of a current first suspension phase of a stator winding of the non-inductive brushless motor, and judging the commutation time of the non-inductive brushless motor according to the first terminal voltage; when the commutation opportunity is reached, switching off a switching power device used for a first conduction phase of the stator winding for a preset time; after the preset time is over, executing a commutation operation; detecting a second terminal voltage of a second suspended phase after phase commutation, and comparing the second terminal voltage with an expected result to judge whether the non-inductive brushless motor is in an out-of-step state or not; and when it is determined that the non-inductive brushless motor is in an out-of-step state, correspondingly changing a second conduction phase of the stator winding. The invention also relates to a computer program product and a non-inductive brushless motor system. The position detection precision and the real-time performance of the non-inductive brushless motor can be improved, and the output performance and the user experience of the non-inductive brushless motor are effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of electromechanics, and more particularly to a commutation control method for a sensorless brushless motor. In addition, the present invention also relates to a corresponding computer program product and a corresponding sensorless brushless motor system. Background Art

[0002] A brushless motor has a rotor made of a permanent magnet material and a stator with windings, and an electronic commutator is used instead of a mechanical brush. Therefore, the brushless motor has the advantages of simple structure, good linear mechanical characteristics, wide speed regulation range, high operating efficiency, etc. and is widely used in different fields, such as vehicles or power tools.

[0003] During the operation of a brushless motor, it is necessary to obtain the rotor position to achieve operation control. In order to simplify the structure, reduce the number of parts and lower the cost, the sensorless brushless motor without a Hall sensor is the main development trend at present. At present, many position detection methods have been proposed for the sensorless brushless motor without a position sensor, such as the back electromotive force zero-crossing detection method, the model reference adaptive method, the state observer method, etc.

[0004] However, during the low-speed operation of the existing sensorless brushless motor, when performing a commutation operation, the residual current in the stator winding will affect the detection result of the electrical parameters after commutation, resulting in an incorrect rotor position detection and causing a step-out phenomenon, which will cause the output jitter of the sensorless brushless motor and even lead to shutdown, reducing the output performance of the sensorless brushless motor and adversely affecting the user experience. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide an improved commutation control method for a sensorless brushless motor. Through the commutation control method, the position detection accuracy and real-time performance of the sensorless brushless motor can be improved, and when a step-out state occurs, the conduction phase of the stator winding can be adjusted in time, thereby effectively improving the output performance and user experience of the sensorless brushless motor.

[0006] According to a first aspect of the present invention, there is provided a commutation control method for a sensorless brushless motor, wherein the commutation control method at least includes the following steps:

[0007] S1: Detect the first terminal voltage of the current first floating phase of the stator winding of the sensorless brushless motor, and judge the commutation timing of the sensorless brushless motor according to the first terminal voltage;

[0008] S2: When the commutation timing is reached, turn off the switching power device of the first conduction phase for the stator winding for a preset time;

[0009] S3: After the preset time ends, perform a commutation operation;

[0010] S4: Detect the second terminal voltage of the second floating phase after commutation and compare the second terminal voltage with an expected result to determine whether the sensorless brushless motor is in an out-of-step state;

[0011] S5: When it is determined that the sensorless brushless motor is in an out-of-step state, correspondingly change the second conducting phase of the stator winding.

[0012] Compared with the prior art, in the commutation control method for a sensorless brushless motor according to the present invention, when the commutation timing is reached, the switching power devices for the first conducting phase of the stator winding are all turned off for a preset time, rather than directly turning on the switching power devices for the second conducting phase after commutation. During the preset time, the current in the first conducting phase continues to flow through the switching power devices for the first conducting phase and rapidly drops to zero under the action of the DC bus voltage, so that there is no current in the second floating phase after commutation. This allows the second terminal voltage of the second floating phase to be detected immediately without being affected by the current and to be only related to the rotor position, thereby improving the real-time performance and accuracy of position detection, and being able to accurately determine the out-of-step state and timely adjust the conducting phase of the stator winding, so as to avoid phenomena such as output jitter of the sensorless brushless motor and effectively improve the output performance and user experience of the sensorless brushless motor.

[0013] According to a second aspect of the present invention, there is provided a computer program product, which includes a computer program. When the computer program is executed by one or more processors, the processors can execute the commutation control method according to the present invention.

[0014] According to a third aspect of the present invention, there is provided a sensorless brushless motor system, where the sensorless brushless motor system at least includes:

[0015] - A sensorless brushless motor;

[0016] - A converter, the converter includes six switching power devices, and the switching power devices are arranged in the form of a three-phase six-arm full bridge. Among them, the converter is configured to be suitable for injecting a pulse voltage into the stator winding of the sensorless brushless motor;

[0017] - A voltage detection module, the voltage detection module is configured to be suitable for detecting the terminal voltage of the floating phase of the stator winding;

[0018] - A control module, the control module is communicatively connected to the converter and the voltage detection module respectively and is configured to be suitable for executing the commutation control method according to the present invention by using the computer program product according to the present invention. Description of the Drawings

[0019] Next, the present invention will be described in more detail by referring to the accompanying drawings, and the principles, features, and advantages of the present invention can be better understood. The accompanying drawings include:

[0020] Figure 1 A schematic block diagram of a sensorless brushless motor system according to an exemplary embodiment of the present invention is shown;

[0021] Figure 2 A schematic flow chart of a commutation control method for a sensorless brushless motor according to an exemplary embodiment of the present invention is shown;

[0022] Figure 3 A schematic diagram of the current flow direction when the sensorless brushless motor system commutes according to an exemplary embodiment of the present invention is shown;

[0023] Figure 4 A schematic relationship diagram between the rotor position of a sensorless brushless motor and the inductance of the stator winding according to an exemplary embodiment of the present invention is shown. Detailed implementation manners

[0024] In order to make the technical problems to be solved, technical solutions, and beneficial technical effects of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the protection scope of the present invention. Here, for the sake of brevity, elements with the same reference numerals are only labeled once in the drawings.

[0025] It should be understood that in this text, expressions such as "first" and "second" are only for descriptive purposes and should not be construed as indicating or implying relative importance, nor should they be construed as implicitly indicating the number of the indicated technical features. Features defined with "first" and "second" may explicitly or implicitly include at least one of such features.

[0026] Figure 1 A schematic block diagram of a sensorless brushless motor system 100 according to an exemplary embodiment of the present invention is shown. Here, depending on the power supply module, the sensorless brushless motor system 100 can be a DC brushless motor system or an AC brushless motor system.

[0027] As Figure 1As shown, the sensorless brushless motor system 100 includes a sensorless brushless motor 10, which has a rotor made of permanent magnetic material, especially a magnet-embedded type, and a stator with a stator winding. The stator winding consists of coils wound in the punching slots of the stator. When a current passes through the stator winding, a magnetic field is generated by the stator winding, and the rotor rotates under the action of the magnetic field. Among them, the stator winding has three phases, namely the U phase, the V phase, and the W phase, and each phase has a conduction interval of 120° electrical angle. A bidirectional current can flow through the stator winding of each phase. By changing the phase and current direction of the stator winding, the generated magnetic field can be controlled, so as to realize the continuous rotation of the rotor and achieve the desired rotation direction and rotation speed. Here, for the sake of brevity, the rotor and stator of the sensorless brushless motor 10 are not shown.

[0028] As Figure 1 shown, the sensorless brushless motor system 100 includes a converter 20, which has six switching power devices 21. The switching power devices are configured as power transistors, for example, and arranged in the form of a three-phase six-arm full bridge, so that one switching power device 21 is arranged at each of the two wire ends of the stator winding for each phase. Exemplarily, a first switching power device T1 is arranged at the upper bridge arm of the U-phase stator winding, that is, UP, a second switching power device T2 is arranged at the lower bridge arm of the U-phase stator winding, that is, UN, a third switching power device T3 is arranged at the upper bridge arm of the V-phase stator winding, that is, VP, a fourth switching power device T4 is arranged at the lower bridge arm of the V-phase stator winding, that is, VN, a fifth switching power device T5 is arranged at the upper bridge arm of the W-phase stator winding, that is, WP, and a sixth switching power device T6 is arranged at the lower bridge arm of the W-phase stator winding, that is, WN (only the corresponding symbols are shown hereinafter for the sake of brevity). When connected to the power supply module, by controlling the switching states of the respective switching power devices 21 of the converter 20, a DC bus voltage U DC can be applied to the sensorless brushless motor 10 to generate a corresponding magnetic field and drive the rotor to rotate in the desired rotation direction.

[0029] As Figure 1As shown, the sensorless brushless motor system 100 includes a voltage detection module 30. The voltage detection module is respectively connected to the ends of each phase of the stator windings and is configured to detect the terminal voltage of the floating-phase stator winding relative to ground when injecting a pulse voltage into the conducting-phase stator winding. In the framework of the present invention, "conducting phase" should be understood as that by closing the power switch devices arranged at the upper bridge arm of the first-phase stator winding, such as UP, and at the lower bridge arm of the second-phase stator winding, such as VN, the two-phase stator windings are conductively connected to the power supply. Thus, when a voltage is applied by the power supply, the voltage is injected into the two-phase stator windings and a response current is generated in the two-phase stator windings. Wherein, each conducting phase corresponds to an electrical angle range of 60° of the rotor; and "floating phase" should be understood as that the third phase among the three-phase stator windings, such as phase W, except for the conducting phase, and the power switch devices corresponding to the third phase are all in the off state, so that no response current is generated in the stator winding of the third phase.

[0030] As Figure 1 As shown, the sensorless brushless motor system 100 includes a control module 40. The control module is respectively communicatively connected to the converter 20 and the voltage detection module 30 and can implement commutation operations by controlling the switching states of the respective switching power devices 21 in the converter 20 to change the conducting phase of the stator windings and keep the rotor rotating continuously.

[0031] Exemplarily, as Figure 1 As shown, the sensorless brushless motor system 100 further includes a current detection module 50. The current detection module is connected to the DC bus and is configured to detect the response current of the stator winding when a voltage is applied to the conducting phase.

[0032] Exemplarily, the sensorless brushless motor system 100 is integrally constructed to achieve a compact configuration of the sensorless brushless motor system 100.

[0033] Figure 2 Shows a schematic flowchart of a commutation control method for a sensorless brushless motor 10 according to an exemplary embodiment of the present invention. Figure 3 Shows a schematic diagram of the current flow direction during commutation of the sensorless brushless motor system 100 according to an exemplary embodiment of the present invention. Figure 4 Shows a schematic relationship diagram between the rotor position of the sensorless brushless motor 10 and the inductance of the stator winding according to an exemplary embodiment of the present invention.

[0034] As Figure 2 As shown, the commutation control method according to the present invention at least includes the following steps:

[0035] S1: Apply the DC bus voltage U to the current first conducting phase of the stator winding DCIn the case of, the current first-end voltage of the stator winding of the sensorless brushless motor 10 is detected by the voltage detection module 30, and the commutation timing of the sensorless brushless motor 10 is judged according to the first-end voltage;

[0036] S2: When the commutation timing is reached, the switching power device for the first conducting phase is turned off by the control module 40 for a preset time, and all the switching power devices are in the off state during this preset time;

[0037] S3: After the preset time ends, a commutation operation is performed;

[0038] S4: After commutation, the second-end voltage of the second floating phase after commutation is detected by the voltage detection module 30 and the second-end voltage is compared with the expected result to judge whether the sensorless brushless motor 10 is in an out-of-step state;

[0039] S5: When it is determined that the sensorless brushless motor 10 is in an out-of-step state, the second conducting phase of the stator winding is correspondingly changed by the control module 40.

[0040] Here, it is assumed that in step S1, the first conducting phase is the upper bridge arm UP of the U-phase stator winding and the lower bridge arm VN of the V-phase stator winding, and the first floating phase is the W-phase. Then, in step S1, the first switching power device T1 for UP and the fourth switching power device T4 for VN are in the on state, and the current generated under the action of the DC bus voltage U DC flows through the first switching power device T1, the U-phase stator winding, the V-phase stator winding, and the fourth switching power device T4 in sequence, and finally returns to the power supply.

[0041] As Figure 3 shown, when the commutation timing is reached, both the first switching power device T1 and the fourth switching power device T4 are turned off for a preset time. In this case, Figure 3 the dotted arrows in show the direction of current flow. The residual current in the U-phase stator winding and the V-phase stator winding continues to flow through the second switching power device T2 at the lower bridge arm UN of the U-phase stator winding and the third switching power device T3 at the upper bridge arm VP of the V-phase stator winding, so that the current in the stator winding returns to the DC bus. Thus, the current rapidly decreases under the damping action of the DC bus voltage U DC Especially, the current in the stator winding is reduced to zero within the preset time, thereby avoiding the adverse influence of the current in the stator winding of the second floating phase on the detection of the end voltage after the commutation operation. Exemplarily, the preset time and the DC bus voltage U of the sensorless brushless motor DCIs inversely proportional and can be calculated by an empirical formula. In particular, the preset time is on the order of microseconds, for example, less than 500 microseconds. This can eliminate the influence of the current in the floating-phase stator winding in the case of a relatively short turn-off time of the switching power device.

[0042] Exemplarily, in step S1, from the first terminal voltage of the first floating phase and the DC bus voltage U of the sensorless brushless motor 10 DC The first induced electromotive force of the first floating phase is calculated. When the first induced electromotive force is zero, it is determined that the commutation timing is reached. Of course, other commutation timings that those skilled in the art consider meaningful can also be considered, such as an electrical angle 30° later than the above commutation timing.

[0043] Specifically, the induced electromotive force of the floating phase is proportional to the difference between the terminal voltage and half of the DC bus voltage U DC That is, 0.5U DC When the terminal voltage is equal to half of the DC bus voltage U DC The induced electromotive force is zero. When the terminal voltage is less than half of the DC bus voltage U DC The induced electromotive force is negative, and when the terminal voltage is greater than half of the DC bus voltage U DC The induced electromotive force is positive. In addition, it should be noted that the terminal voltage of the floating phase corresponds to the voltage division of the stator winding of the lower arm in the conducting phase, and this voltage division is proportional to the inductance of this stator winding. The greater the voltage division, the greater the inductance of this stator winding. Thus, when the induced electromotive force of the floating phase is zero, it indicates that the inductances of the stator windings of the upper and lower arms in the conducting phase are the same; when the induced electromotive force of the floating phase is positive, it indicates that the inductance of the stator winding of the lower arm in the conducting phase is greater than that of the stator winding of the upper arm; and when the induced electromotive force of the floating phase is negative, it indicates that the inductance of the stator winding of the lower arm in the conducting phase is less than that of the stator winding of the upper arm.

[0044] As Figure 4 Shown, the abscissa θ is the angle of the N pole of the rotor relative to a stator winding, and the ordinate L is the inductance of the stator winding. Here, when the stator winding is energized, the permanent magnet flux of the rotor and the additional flux generated by the stator winding current act together to affect the saturation degree of the stator core. When the permanent magnet flux and the additional flux are in the same direction, a magnetizing effect is generated, the saturation degree of the stator core increases, and the inductance of the stator winding decreases; while when the permanent magnet flux and the additional flux are in the opposite direction, a demagnetizing effect is generated, the saturation degree of the stator core decreases, and the inductance of the stator winding increases.

[0045] As Figure 4As shown, when the angle of the N pole of the rotor with respect to a stator winding is 0°, the inductance of this stator winding is the smallest. As the rotor rotates, the inductance of the stator winding gradually increases and reaches the maximum level when the angle of the N pole of the rotor with respect to this stator winding is 90°. During the process where the angle of the N pole of the rotor with respect to the stator winding ranges from 90° to 180°, the inductance of the stator winding gradually decreases again.

[0046] As Figure 4 shown, since the stator windings of the three phases have an angular interval of 120° relative to each other, the curves of the inductances of the stator windings of the U phase, V phase, and W phase with respect to the change in rotor position are offset from each other by 120°, and the trends of the inductance curves of the stator windings of each phase are the same. Among them, the inductance curve of the U-phase stator winding is represented by a solid line, the inductance curve of the V-phase stator winding is represented by a dashed line, and the inductance curve of the W-phase stator winding is represented by a dotted line. For example, the inductance of the U-phase stator winding at 0° is equal to the inductance of the V-phase stator winding at 120° and is equal to the inductance of the W-phase stator winding at 240°. By comparing the magnitude relationships of the inductances of the stator windings of each phase, the angular position of the rotor can be determined.

[0047] Exemplarily, in step S4, the second induced electromotive force of the second floating phase is calculated from the second terminal voltage of the second floating phase and the DC bus voltage U DC wherein, when the N pole of the rotor of the sensorless brushless motor is in the electrical angle range of 0° to 60° or 120° to 180° or 240° to 300°, the expected result of the second induced electromotive force is positive, and when the N pole of the rotor is in the electrical angle range of 60° to 120° or 180° to 240° or 300° to 360°, the expected result of the second induced electromotive force is negative. Wherein, when the second induced electromotive force does not match the expected result, it is determined that the sensorless brushless motor is in an out-of-step state.

[0048] As Figure 4 shown, assuming that the rotor of the sensorless brushless motor 10 rotates in the clockwise direction, the first conducting phase is the upper bridge arm UP of the U-phase stator winding and the lower bridge arm VN of the V-phase stator winding, and the first floating phase is the W phase. At this time, the N pole of the rotor of the sensorless brushless motor 10 should be in the electrical angle range of 0° to 60°. Among them, the inductance of the V-phase stator winding is greater than the inductance of the U-phase stator winding, such that the first terminal voltage of the W phase is greater than the DC bus voltage U DCHalf of it, the first induced electromotive force is positive. When the first induced electromotive force of the W phase is zero, the N pole of the rotor is at an electrical angle of 60° and the commutation timing is reached. After turning off the first switching power device T1 and the fourth switching power device T4 for the first conducting phase for a preset time, the commutation operation is performed. The second conducting phase is the upper bridge arm UP of the U-phase stator winding and the lower bridge arm WN of the W-phase stator winding, and the second floating phase is the V phase. Therefore, the first switching power device T1 and the sixth switching power device T6 are turned on, and the second terminal voltage of the V phase is detected. Here, if the sensorless brushless motor 10 is operating normally, that is, in a non-step-out state, the N pole of the rotor should be in the electrical angle range of 60° to 120°. Among them, the inductance of the W-phase stator winding is less than the inductance of the U-phase stator winding, so that the second terminal voltage of the V phase is less than the DC bus voltage U DC Half of it, the second induced electromotive force should be negative. However, if the sensorless brushless motor 10 is in a step-out state, the rotor rotates counterclockwise due to a high load, for example, and is in the electrical angle range of 300° to 360°, then the inductance of the W-phase stator winding is greater than the inductance of the U-phase stator winding, so that the second terminal voltage of the V phase is greater than the DC bus voltage U DC Half of it, the second induced electromotive force is positive. Therefore, if when the second conducting phase is the upper bridge arm UP of the U-phase stator winding and the lower bridge arm WN of the W-phase stator winding and the second induced electromotive force of the second floating phase V is positive, it can be determined that the sensorless brushless motor 10 is in a step-out state. This correspondingly applies to other conducting states of the sensorless brushless motor 10. The specific relationships between the conducting states, the electrical angle range of the rotor N pole, and the positive and negative of the expected induced electromotive force of the floating phase are shown in the following table.

[0049]

[0050] Exemplarily, when another commutation timing is selected in step S1, for example, when it is offset by 30° relative to the zero crossing of the first induced electromotive force, the judgment condition for the step-out state based on the second induced electromotive force changes accordingly. In addition, it can also be considered to directly judge whether the sensorless brushless motor 10 is in a step-out state based on the second terminal voltage and the DC bus voltage.

[0051] Exemplarily, in step S5, when it is determined that the sensorless brushless motor 10 is in a step-out state, the second conducting phase of the stator winding is callback by 120° of electrical angle in the reverse rotation direction. For example, when the second conducting phase is the upper bridge arm UP of the U-phase stator winding and the lower bridge arm WN of the W-phase stator winding and the rotation direction of the sensorless brushless motor 10 is clockwise, if the second induced electromotive force calculated according to the second terminal voltage of the second floating phase is positive, the inductance of the W-phase stator winding is greater than that of the U-phase stator winding and the sensorless brushless motor 10 is in a step-out state. Thus, it can be determined that the N pole of the rotor is in the electrical angle range of 300° - 360°. To correct this step-out state, corresponding to the position of the N pole of the rotor, the second conducting phase is callback by 120° of electrical angle in the reverse rotation direction. The adjusted second conducting phase is the upper bridge arm WP of the W-phase stator winding and the lower bridge arm VN of the V-phase stator winding, which can effectively eliminate the step-out phenomenon of the sensorless brushless motor 10 and improve the output performance.

[0052] Exemplarily, the commutation control method according to the present invention is only implemented when the rotor speed of the sensorless brushless motor 10 is lower than the speed threshold, and the rotor speed can be obtained according to the commutation frequency. Here, the speed threshold is, for example, 1% of the no-load speed of the sensorless brushless motor 10. Of course, other speed values considered meaningful by those skilled in the art can also be considered.

[0053] Exemplarily, in step S4, additionally detect the response current of the stator winding. According to the change rate of the response current, the inductance of the conducting-phase stator winding can be determined, and whether the sensorless brushless motor 10 is in a step-out state can be judged from the change of the inductance. For this purpose, a current detection module 50 is connected to the DC bus to detect the response current of the stator winding. Thus, the accuracy of the state judgment of the sensorless brushless motor 10 can be further improved.

[0054] Here, the control module 40 of the sensorless brushless motor system 100 can execute the commutation control method for the sensorless brushless motor 10 according to the present invention by using the computer program product according to the present invention. The computer program product includes a computer program, wherein when the computer program is executed by one or more processors, the processor can execute the commutation control method according to the present invention.

[0055] The foregoing explanation of the embodiments only describes the present invention within the framework of the examples. Of course, as long as it is technically meaningful, the various features of the embodiments can be freely combined with each other without departing from the framework of the present invention.

[0056] For those skilled in the art, other advantages and alternative embodiments of the present invention will be obvious. Therefore, the present invention in its broader sense is not limited to the specific details, representative structures, and exemplary embodiments shown and described. Instead, those skilled in the art can make various modifications and substitutions without departing from the basic spirit and scope of the present invention.

Claims

1. A commutation control method for a sensorless brushless motor (10), characterized in that, The commutation control method at least includes the following steps: S1: Detect the first terminal voltage of the current first floating phase of the stator winding of the sensorless brushless motor (10), and judge the commutation timing of the sensorless brushless motor (10) according to the first terminal voltage; S2: When the commutation timing is reached, turn off the switching power device of the first conducting phase for the stator winding for a preset time; S3: After the preset time ends, perform a commutation operation; S4: Detect the second terminal voltage of the second floating phase after commutation and compare the second terminal voltage with an expected result to judge whether the sensorless brushless motor (10) is in an out-of-step state; S5: When it is determined that the sensorless brushless motor (10) is in an out-of-step state, correspondingly change the second conducting phase of the stator winding.

2. The commutation control method according to claim 1, wherein In step S1, a first induced electromotive force of the first floating phase is calculated from the first terminal voltage and the DC bus voltage (U DC ) of the sensorless brushless motor (10). When the first induced electromotive force is zero, it is determined that the commutation timing is reached.

3. The commutation control method according to claim 2, wherein In step S4, a second induced electromotive force of the second floating phase is calculated from the second terminal voltage and the DC bus voltage (U DC ). Depending on the conduction state of the sensorless brushless motor (10), when the N pole of the rotor of the sensorless brushless motor (10) is in the electrical angle range of 0° to 60° or 120° to 180° or 240° to 300°, the expected result of the second induced electromotive force is positive. When the N pole of the rotor is in the electrical angle range of 60° to 120° or 180° to 240° or 300° to 360°, the expected result of the second induced electromotive force is negative. When the second induced electromotive force does not match the expected result, it is determined that the sensorless brushless motor (10) is in an out-of-step state.

4. The commutation control method according to any one of claims 1 to 3, wherein When the sensorless brushless motor (10) is in an out-of-step state, the second conducting phase of the stator winding is adjusted back by an electrical angle of 120° in the reverse rotation direction.

5. The commutation control method according to any one of the foregoing claims, wherein The preset time is set such that the current in the stator winding of the second floating phase drops to zero; and / or The preset time is inversely proportional to the DC bus voltage of the sensorless brushless motor; and / or The preset time is of the order of microseconds.

6. The commutation control method according to any one of the foregoing claims, wherein The commutation control method is only implemented when the rotor speed of the sensorless brushless motor (10) is lower than a speed threshold, and the rotor speed is obtained according to the commutation frequency.

7. The commutation control method according to any one of the foregoing claims, wherein In step S4, additionally detect the response current of the stator winding, and judge whether the sensorless brushless motor (10) is in an out-of-step state according to the change rate of the response current.

8. A computer program product comprising a computer program, wherein, When the computer program is executed by one or more processors, the processor can execute the commutation control method according to any one of claims 1-7.

9. A sensorless brushless motor system (100), characterized in that, The sensorless brushless motor system (100) at least includes: - A sensorless brushless motor (10); - A converter (20), the converter includes six switching power devices (21), and the switching power devices are arranged in the form of a three-phase six-arm full bridge. Among them, the converter is configured to be suitable for injecting a pulse voltage into the stator winding of the sensorless brushless motor (10); - A voltage detection module (30), the voltage detection module is configured to be suitable for detecting the terminal voltage of the floating phase of the stator winding; - A control module (40), the control module is respectively communicatively connected with the converter (20) and the voltage detection module (30) and is configured to be suitable for executing the commutation control method according to any one of claims 1 to 7 by using the computer program product according to claim 8.

10. The sensorless brushless motor system (100) according to claim 9, characterized in that the sensorless brushless motor system (100) further includes a current detection module (50), and the current detection module is configured to be adapted to detect the response current of the stator winding; and / or the sensorless brushless motor system (100) is integrally constructed.

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