阅读说明：本技术 一种无刷直流电机的反电势过零检测方法、装置及吸尘器 (Counter potential zero-crossing detection method and device of brushless direct current motor and dust collector ) 是由 朱泽春 肖占魁 王建坤 于 2019-11-15 设计创作，主要内容包括：本申请实施例提供了一种无刷直流电机的反电势过零检测方法、装置及吸尘器,涉及电机技术领域。该方法包括：比较无刷直流电机的悬空相的端电压与无刷直流电机的三相绕组的中性点电压并获取相应的比较结果,然后基于预设的滤波输入个数设定采样窗口,按照相应的采样窗口对比较结果进行采样以生成第一比较结果组,并根据第一比较结果组确定无刷直流电机的反电势过零并换相。采用本申请可以提高反电势过零检测的准确性。(The embodiment of the application provides a counter potential zero-crossing detection method and device of a brushless direct current motor and a dust collector, and relates to the technical field of motors. The method comprises the following steps: the method comprises the steps of comparing the terminal voltage of a suspension phase of the brushless direct current motor with the neutral point voltage of a three-phase winding of the brushless direct current motor, obtaining a corresponding comparison result, setting a sampling window based on the preset filtering input number, sampling according to the corresponding sampling window comparison result to generate a first comparison result set, and determining the counter potential zero crossing of the brushless direct current motor and changing the phase according to the first comparison result set. By the adoption of the method and the device, the counter potential zero-crossing detection accuracy can be improved.)

1. A back emf zero crossing detection method for a brushless dc motor, the method comprising:

comparing the terminal voltage of the suspension phase of the brushless direct current motor with the neutral point voltage of the three-phase winding of the brushless direct current motor and obtaining a corresponding comparison result;

setting sampling windows based on the preset filtering input number, and sampling the comparison results according to the corresponding sampling windows to generate a first comparison result group;

and determining the back electromotive force zero crossing of the brushless direct current motor according to the first comparison result group and carrying out phase commutation.

2. The method of claim 1, wherein the number of filtered inputs is 4n +2, and wherein n is a positive integer.

3. The method of claim 1 or 2, wherein the number of filter inputs is less than t1/t2, wherein t1 is a time period required for the brushless DC motor to rotate from a commutation point to a zero crossing point, and t2 is a period of comparison between a terminal voltage of the suspended phase and a neutral voltage of the three-phase winding.

4. The method of claim 2, wherein said determining a back emf zero crossing and commutation of said brushless dc motor based on said first set of comparison results comprises:

judging whether the first comparison result group meets a first preset condition or not, wherein the first preset condition comprises the following steps: the direction values of the first 2n +1 comparison results of the first comparison result group are different from the direction values of the second 2n +1 comparison results, wherein the direction value is the comparison result with the largest occurrence frequency in the 2n +1 comparison results;

and if the first preset condition is met, judging that the back electromotive force of the brushless direct current motor is zero-crossed.

5. The method of claim 4, wherein the first preset condition further comprises: the first comparison result set is not a comparison result set which causes pointing values of the first 2n +1 comparison results to be different from pointing values of the second 2n +1 comparison results due to noise interference.

6. The method of claim 4, further comprising:

and if the first preset condition is not met, moving the sampling window backward and forward by one bit according to a time sequence, resampling according to the moved sampling window to obtain a new first comparison result group, and judging whether the back electromotive force of the brushless direct current motor is zero-crossed according to the newly obtained first comparison result group until the back electromotive force is determined to be zero-crossed.

7. The method of claim 4, further comprising:

if the back electromotive force of the brushless direct current motor is judged to be zero, determining the back electromotive force zero crossing time of the brushless direct current motor according to the comparison time of the comparison results in the first comparison result group;

and controlling the brushless direct current motor to change the phase after waiting for a first preset time period by taking the moment of the counter electromotive force zero crossing of the brushless direct current motor as a starting point, wherein the first preset time period is the time period required by the brushless direct current motor to change from the position of the counter electromotive force zero crossing to the position of the phase change point.

8. The method of claim 7, wherein determining a time at which a back emf of the brushless DC motor crosses zero based on the comparison times of the comparison results in the first comparison result set comprises:

determining an intermediate time between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result group as the time when the back emf of the brushless direct current motor crosses zero.

9. A back emf zero cross detection apparatus for a brushless dc motor, the apparatus comprising:

the comparison module is used for comparing the terminal voltage of the suspension phase of the brushless direct current motor with the neutral point voltage of the three-phase winding of the brushless direct current motor and acquiring a corresponding comparison result;

the sampling module is used for setting sampling windows based on the preset filtering input number and sampling the comparison results according to the corresponding sampling windows to generate a first comparison result group;

and the determining module is used for determining the counter electromotive force zero crossing of the brushless direct current motor according to the first comparison result group and carrying out phase commutation.

10. A dust collector is characterized by comprising a brushless direct current motor, a memory and a processor;

a memory for storing a computer program;

a processor for implementing the method steps of any of claims 1 to 8 when executing a program stored in the memory.

Technical Field

The application relates to the technical field of motors, in particular to a counter potential zero-crossing detection method and device for a brushless direct current motor and a dust collector.

Background

At present, in sensorless driving control of a brushless dc motor, a back electromotive force zero-crossing detection method is generally adopted to determine the position of a rotor, so as to control the phase change of the brushless dc motor.

Disclosure of Invention

The embodiment of the application aims to provide a back electromotive force zero-crossing detection method and device for a brushless direct current motor and a dust collector, and the back electromotive force zero-crossing detection accuracy can be improved. The specific technical scheme is as follows:

in a first aspect, a back emf zero-crossing detection method for a brushless dc motor is provided, the method comprising:

comparing the terminal voltage of the suspension phase of the brushless direct current motor with the neutral point voltage of the three-phase winding of the brushless direct current motor and obtaining a corresponding comparison result;

setting sampling windows based on the preset filtering input number, and sampling the comparison results according to the corresponding sampling windows to generate a first comparison result group;

and determining the back electromotive force zero crossing of the brushless direct current motor according to the first comparison result group and carrying out phase commutation.

Optionally, the number of the filter inputs is 4n +2, and n is a positive integer.

Optionally, the number of the filter inputs is less than t1/t2, where t1 is a time period required for the brushless dc motor to rotate from a commutation point to a zero-crossing point, and t2 is a comparison period between a terminal voltage of the suspended phase and a neutral voltage of the three-phase winding.

Optionally, the determining a back electromotive force zero crossing of the brushless dc motor according to the first comparison result set and performing phase commutation includes:

judging whether the first comparison result group meets a first preset condition or not, wherein the first preset condition comprises the following steps: the direction values of the first 2n +1 comparison results of the first comparison result group are different from the direction values of the second 2n +1 comparison results, wherein the direction value is the comparison result with the largest occurrence frequency in the 2n +1 comparison results;

and if the first preset condition is met, judging that the back electromotive force of the brushless direct current motor is zero-crossed.

Optionally, the first preset condition further includes: the first comparison result set is not a comparison result set which causes pointing values of the first 2n +1 comparison results to be different from pointing values of the second 2n +1 comparison results due to noise interference.

Optionally, the method further includes:

and if the first preset condition is not met, moving the sampling window backward and forward by one bit according to a time sequence, resampling according to the moved sampling window to obtain a new first comparison result group, and judging whether the back electromotive force of the brushless direct current motor is zero-crossed according to the newly obtained first comparison result group until the back electromotive force is determined to be zero-crossed.

Optionally, the method further includes:

if the back electromotive force of the brushless direct current motor is judged to be zero, determining the back electromotive force zero crossing time of the brushless direct current motor according to the comparison time of the comparison results in the first comparison result group;

and controlling the brushless direct current motor to change the phase after waiting for a first preset time period by taking the moment of the counter electromotive force zero crossing of the brushless direct current motor as a starting point, wherein the first preset time period is the time period required by the brushless direct current motor to change from the position of the counter electromotive force zero crossing to the position of the phase change point.

Optionally, the determining the time when the back electromotive force of the brushless dc motor crosses zero according to the comparison time of the comparison result in the first comparison result group includes:

determining an intermediate time between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result group as the time when the back emf of the brushless direct current motor crosses zero.

In a second aspect, there is provided a back emf zero-crossing detection apparatus for a brushless dc motor, the apparatus comprising:

the comparison module is used for comparing the terminal voltage of the suspension phase of the brushless direct current motor with the neutral point voltage of the three-phase winding of the brushless direct current motor and acquiring a corresponding comparison result;

the sampling module is used for setting sampling windows based on the preset filtering input number and sampling the comparison results according to the corresponding sampling windows to generate a first comparison result group;

and the determining module is used for determining the counter electromotive force zero crossing of the brushless direct current motor according to the first comparison result group and carrying out phase commutation.

Optionally, the number of the filter inputs is 4n +2, and n is a positive integer.

Optionally, the number of the filter inputs is less than t1/t2, where t1 is a time period required for the brushless dc motor to rotate from a commutation point to a zero-crossing point, and t2 is a comparison period between a terminal voltage of the suspended phase and a neutral voltage of the three-phase winding.

Optionally, the determining module includes:

a first determining unit, configured to determine whether the first comparison result group meets a first preset condition, where the first preset condition includes: the direction values of the first 2n +1 comparison results of the first comparison result group are different from the direction values of the second 2n +1 comparison results, wherein the direction value is the comparison result with the largest occurrence frequency in the 2n +1 comparison results;

a first determination unit configured to determine that a back electromotive force of the brushless dc motor crosses zero if the first preset condition is satisfied.

Optionally, the first preset condition further includes: the first comparison result set is not a comparison result set which causes pointing values of the first 2n +1 comparison results to be different from pointing values of the second 2n +1 comparison results due to noise interference.

Optionally, the determining module further includes a second determining unit;

and the second judging unit is used for moving the sampling window backward by one bit according to a time sequence if the first preset condition is not met, resampling according to the moved sampling window to obtain a new first comparison result group, and judging whether the back electromotive force of the brushless direct current motor crosses zero according to the new first comparison result group until the back electromotive force crosses zero.

Optionally, the determining module further includes a phase changing unit, and the phase changing unit includes:

a determining subunit, configured to determine, if it is determined that the back emf of the brushless dc motor crosses zero, a time at which the back emf of the brushless dc motor crosses zero according to a comparison time of the comparison results in the first comparison result group;

and the phase change subunit is used for controlling the brushless direct current motor to change the phase after waiting for a first preset time length by taking the moment of the counter potential zero crossing of the brushless direct current motor as a starting point, wherein the first preset time length is the time length required by the brushless direct current motor to change from the position of the counter potential zero crossing to the position of the phase change point.

Optionally, the determining subunit is specifically configured to:

determining an intermediate time between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result group as the time when the back emf of the brushless direct current motor crosses zero.

In a third aspect, a vacuum cleaner is provided, which comprises a brushless direct current motor, a memory and a processor;

a memory for storing a computer program;

a processor for implementing the method steps of the first aspect when executing the program stored in the memory.

The embodiment of the application provides a counter potential zero-crossing detection method and device of a brushless direct current motor and a dust collector, which can compare terminal voltage of a suspension phase of the brushless direct current motor with neutral point voltage of a three-phase winding of the brushless direct current motor and obtain a corresponding comparison result, then set a sampling window based on a preset filtering input number, sample the comparison result according to the corresponding sampling window to generate a first comparison result group, and determine counter potential zero-crossing of the brushless direct current motor and change phases according to the first comparison result group.

Compared with the prior art, the counter potential zero-crossing detection method and the counter potential zero-crossing detection device have the advantages that whether the counter potential of the brushless direct current motor crosses zero or not is determined through the first comparison result group generated by sampling of the sampling window set based on the preset filtering input number, misjudgment caused by the fact that counter potential zero-crossing detection is carried out only through one comparison result is avoided, the counter potential zero-crossing detection accuracy is improved, and further the phase change time of the brushless direct current motor is more accurate.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a back emf zero-crossing detection method of a brushless dc motor according to an embodiment of the present disclosure;

fig. 2 is a back emf zero-crossing detection circuit of a brushless dc motor according to an embodiment of the present disclosure;

fig. 3 is a schematic structural diagram of a back electromotive force zero-crossing detection apparatus of a brushless dc motor according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides a back electromotive force zero-crossing detection method of a brushless direct current motor, which can be applied to electronic equipment with the brushless direct current motor. The electronic device may be a vacuum cleaner or the like. The windings of the brushless dc motor may be in a star connection or a delta connection.

The counter potential zero crossing detection method of the brushless dc motor provided in the embodiments of the present application will be described in detail with reference to specific embodiments, as shown in fig. 1, the specific steps are as follows:

and S101, comparing the terminal voltage of the suspension phase of the brushless direct current motor with the neutral point voltage of the three-phase winding of the brushless direct current motor and obtaining a corresponding comparison result.

The suspension phase is a winding which is not electrified in a three-phase winding of the current brushless direct current motor.

In the embodiment of the application, the electronic device may periodically compare the terminal voltage of the suspended phase of the brushless dc motor with the neutral point voltage of the three-phase winding of the brushless dc motor.

In one implementation, the electronic device includes a processor, the processor includes a plurality of ADCs (Analog-to-digital converters), the processor may sample terminal voltages of a suspension phase of the brushless dc motor through the ADCs, as shown in fig. 2, a U-phase winding of the brushless dc motor is connected to one end of a resistor R8, the other end of the resistor R8 is connected to AN1 pin and a resistor R9 of the processor, respectively, and the other end of the resistor R9 is grounded; the V-phase winding of the brushless direct current motor is connected with one end of a resistor R11, the other end of a resistor R11 is respectively connected with AN AN2 pin of the processor and a resistor R12, and the other end of the resistor R12 is grounded; the W-phase winding of the brushless DC motor is connected with one end of a resistor R13, the other end of a resistor R13 is respectively connected with AN AN3 pin of the processor and a resistor R14, and the other end of the resistor R14 is grounded. Among them, the AN1 pin, the AN2 pin, and the AN3 pin are input pins of the ADC.

The processor may sample voltages of the U-phase winding, the V-phase winding, and the W-phase winding through AN1 pin, AN2 pin, and AN3 pin according to a first preset sampling period. When the suspended phase is the U phase, the processor can determine the voltage of the U-phase winding as the terminal voltage of the suspended phase; when the suspended phase is the V phase, the processor can determine the voltage of the W-phase winding as the terminal voltage of the suspended phase; when the suspended phase is the W-phase, the processor may determine the voltage of the W-phase winding as the terminal voltage of the suspended phase.

The processor may also sample the center point voltage of the brushless dc motor through the ADC, and referring to fig. 2, one ends of resistors R15, R16, and R17 are connected to the U-phase winding, the V-phase winding, and the W-phase winding, respectively, and the other ends of resistors R15, R16, and R17 are connected together to create a virtual neutral point, which is connected to AN4 pin of the processor, and is grounded through a resistor R18. The AN4 pin is the input pin of the ADC.

The processor may sample the neutral point voltage through AN4 pin according to a first preset sampling period, and then compare the terminal voltage and the neutral point voltage of the suspended phase sampled at the same time to obtain a comparison result. And the comparison period of the comparison result is a first preset sampling period.

In another implementation, referring to fig. 2, the processor may sample voltages of the U-phase winding, the V-phase winding, and the W-phase winding through AN1 pin, AN2 pin, and AN3 pin according to a first preset sampling period, determine AN average value of the voltages of the U-phase winding, the V-phase winding, and the W-phase winding sampled at the same time as a neutral point voltage, and compare the terminal voltage and the neutral point voltage of the sampled suspended phase to obtain a comparison result. And the comparison period of the comparison result is a first preset sampling period.

Wherein, the sampling of the terminal voltage and the neutral point voltage of the suspension phase comprises: when a Pulse Width Modulation (PWM) signal of the brushless dc motor is controlled to be at a high level, a terminal voltage and a neutral point voltage of the suspended phase are sampled, so as to avoid noise generated when the PWM signal controls the switching of the power switching device, which may result in inaccurate sampling result and further inaccurate comparison result.

S102, setting sampling windows based on the preset filtering input number, and sampling comparison results according to the corresponding sampling windows to generate a first comparison result group.

The sampling window is set based on a preset number of filter inputs, for example, the number of sampling points in the sampling window is set to be the same as the number of filter inputs.

In this embodiment of the application, the electronic device may periodically compare the terminal voltage of the suspended phase with the neutral point voltage, and each time the terminal voltage of the suspended phase is compared with the neutral point voltage, the electronic device may sample the comparison result according to a set sampling window to generate a first comparison result group.

For example, the number of sampling points in the sampling window is 6, and the current comparison result is a according to the sequence of comparison time₁、a₂、a₃、a₄、a₅、a₆And the first comparison result group generated by sampling in the sampling window is a₁a₂a₃a₄a₅a₆。

Optionally, the number of filter inputs may be 4n +2, where n is a positive integer.

Optionally, the number of the filter inputs is less than t1/t2, where t1 is a time period required for the brushless dc motor to rotate from the commutation point to the zero-crossing point, and t2 is a comparison period between the terminal voltage of the suspension phase and the neutral point voltage of the three-phase winding.

The acquisition mode of t1 is as follows: and calculating the commutation period of the brushless direct current motor according to the highest rotating speed and the pole pair number of the brushless direct current motor. Then, the time period t1 required for the brushless DC motor to rotate from the commutation point to the zero crossing point is calculated according to the commutation period. When the commutation period is 60 electrical degrees, t1 is the time period required for the brushless dc motor to rotate 60/2 electrical degrees.

t2 is obtained as follows: according to the computing capability of the processor, the time length t2 required by ADC sampling is determined, namely the comparison period of the terminal voltage of the suspension phase and the neutral point voltage of the three-phase winding is determined.

And t1/t2 is the maximum number of comparison results which can be obtained by the processor in the time period when the brushless direct current motor rotates to the nearest zero crossing point after one switching phase.

In the scheme provided by the application, the number of filtering inputs is less than t1/t2, and therefore it can be guaranteed that before the brushless direct current motor rotates to the zero crossing point, electronic equipment can generate a first comparison result group according to a sampling window, and then zero crossing detection is carried out.

Optionally, the magnitude of the filtering input number and the strength of the motor noise are in a positive correlation, that is, the stronger the motor noise is, the larger the filtering input number is, the weaker the motor noise is, and the smaller the filtering input number is. Therefore, the inaccuracy of zero-crossing detection caused by motor noise can be effectively avoided.

And S103, determining the counter electromotive force zero crossing of the brushless direct current motor according to the first comparison result group and carrying out phase commutation.

In this embodiment, the electronic device may determine whether the back electromotive force of the brushless dc motor crosses zero according to the first comparison result set, and if it is determined that the back electromotive force of the brushless dc motor crosses zero, the electronic device may control the brushless dc motor to perform phase change.

Compared with the prior art, the counter potential zero-crossing detection method and the counter potential zero-crossing detection device have the advantages that whether the counter potential of the brushless direct current motor crosses zero or not is determined through the first comparison result group generated by sampling of the sampling window set based on the preset filtering input number, misjudgment caused by the fact that counter potential zero-crossing detection is carried out only through one comparison result is avoided, the counter potential zero-crossing detection accuracy is improved, and further the phase change time of the brushless direct current motor is more accurate.

Optionally, the specific process of determining the back emf zero-crossing of the brushless dc motor according to the first comparison result set and performing phase commutation may include: judging whether the first comparison result group meets a first preset condition, wherein the first preset condition comprises the following steps: the direction values of the first 2n +1 comparison results of the first comparison result group are different from the direction values of the second 2n +1 comparison results, wherein the direction value is the comparison result with the largest occurrence frequency in the 2n +1 comparison results; and if the first preset condition is met, judging that the back electromotive force of the brushless direct current motor crosses zero.

The number of comparison results in the first comparison result group is 4n +2, and n is a positive integer.

In this embodiment of the application, the electronic device may determine whether the directional values of the first 2n +1 comparison results of the first comparison result set are the first results, and whether the directional values of the last 2n +1 comparison results of the first comparison result set are the second results, and if the directional values of the first 2n +1 comparison results of the first comparison result set are the first results and the directional values of the last 2n +1 comparison results are the second results, the electronic device may determine that the first comparison result set satisfies the first preset condition; otherwise, the electronic device may determine that the first comparison result set does not satisfy the first preset condition.

The first result indicates that the terminal voltage of the suspension phase is equal to the neutral point voltage, and the second result indicates that the terminal voltage of the suspension phase is not equal to the neutral point voltage. Or the first result indicates that the terminal voltage of the suspension phase is not equal to the voltage of the central point, and the second result indicates that the terminal voltage of the suspension phase is equal to the voltage of the neutral point.

For example, if the first comparison result group is 110001, where 1 represents that the terminal voltage of the suspended phase is equal to the voltage of the neutral point, and 0 represents that the terminal voltage of the suspended phase is not equal to the voltage of the neutral point, the first 2n +1 comparison results of the first comparison result group have a directional value of 1, that is, a first result, and the second 2n +1 comparison results have a directional value of 0, that is, a second result, and the first comparison result group satisfies a first preset condition, it is determined that the back emf of the brushless dc motor crosses zero. If the first comparison result set is 010001, the pointing values of the first 2n +1 comparison results of the first comparison result set are 0, that is, the first result, and the pointing values of the last 2n +1 comparison results are 0, that is, the first result, and the first comparison result set does not satisfy the first preset condition, it is determined that the back electromotive force of the brushless dc motor does not cross zero.

In one implementation, the electronic device may determine whether the first comparison result group belongs to a comparison result group in a first preset zero-crossing table, and if the first comparison result group belongs to the comparison result group in the first preset zero-crossing table, the first comparison result group satisfies a first preset condition, and determines that the back electromotive force of the brushless dc motor crosses zero; otherwise, the first comparison result group does not meet the first preset condition, and the back electromotive force zero crossing of the brushless direct current motor is judged.

The comparison result group in the first preset zero-crossing table is a comparison result group which is obtained by randomly combining 4n +1 random comparison results and meets the following conditions: the first 2n +1 comparison results are first results, and the directional values of the last 2n +1 comparison results are second results.

For example, the first result indicates that the terminal voltage of the suspended phase is equal to the neutral point voltage, the second result indicates that the terminal voltage of the suspended phase is not equal to the neutral point voltage, and n is 1, the first preset zero crossing table is shown in table one, and the comparison result set can be represented by a binary number in a left column of the table, wherein 1 indicates that the terminal voltage of the suspended phase is equal to the neutral point voltage, and 0 indicates that the terminal voltage of the suspended phase is not equal to the neutral point voltage. The comparison result set can also be represented by decimal values in the right column of the table, and the embodiment of the present application does not specifically limit the representation form of the comparison result set.

Watch 1

Binary value representation of zero-crossing comparison result set	Decimal numerical representation of zero-crossing comparison result set
		011000	24
011001	25
		011010	26
011100	28
		101000	40
101001	41
		101010	42
101100	44
		110000	48
110001	49
		110010	50
110100	52
		111000	56
111001	57
		111010	58
111100	60

Optionally, the first preset condition further includes: the first comparison result set is not a comparison result set in which the directional values of the first 2n +1 comparison results are different from the directional values of the second 2n +1 comparison results due to noise interference.

Wherein, the comparison result group which causes the pointing values of the first 2n +1 comparison results to be different from the pointing values of the second 2n +1 comparison results due to noise interference comprises any one or more of the following comparison result groups: a second comparison result set, a third comparison result set, and a fourth comparison result set.

Wherein the second comparison result set satisfies the following condition: the first comparison result in the second set of comparison results is not the second result.

For example, if the first result indicates that the terminal voltage of the suspended phase is equal to the neutral point voltage, the second result indicates that the terminal voltage of the suspended phase is not equal to the neutral point voltage, and n is 1, the second comparison result set includes 011000, 011001, 011010, and 011110.

Wherein the third comparison result set satisfies the following condition: the first 2n +1 comparison results of the third comparison result set are not all the first results and the first 2n +1 comparison results are not all the second results, and the following condition is satisfied after the third comparison result set is shifted left by one bit: the direction values of the first 2n +1 comparison results are first results, and the direction values of the second 2n +1 comparison results are second results; shifting left by one refers to the first comparison of the set of comparisons being removed and any one comparison being added at the tail.

For example, the first result indicates that the terminal voltage of the suspended phase is equal to the neutral point voltage, the second result indicates that the terminal voltage of the suspended phase is not equal to the neutral point voltage, n is 1, 011000 is 110000 or 110001 after shifting left by one bit, the directional values of the first 2n +1 comparison results of 110000 and 110001 are all the first results, the directional values of the last 2n +1 comparison results are all the second results, and 011000 is the third result group. 0110001 shift left by one, the direction values of the first 2n +1 comparison results are all the first results, and after shifting left by one, they are 1100010 or 1100101, and the direction values of the last 2n +1 comparison results are not all the second results, so 1100010 is not the third result group. Similarly, 011100, 101100, 110100, 111100 is the third comparison result set.

Wherein the fourth comparison result group satisfies the following condition: the fourth comparison result set is obtained after the fifth comparison result set is shifted left by one bit or shifted right by one bit, and the comparison result set meets the following conditions: the direction values of the first 2n +1 comparison results are first results, and the direction values of the second 2n +1 comparison results are second results; shifting right by one refers to the last comparison of the set of comparisons being removed and any comparison being added to the header.

Wherein, the first n +1 comparison results and the last n +1 comparison results of the fifth comparison result set are 0, and the comparison results of 1 exist in the comparison results of the fifth comparison result set except the first n +1 comparison results and the last n +1 comparison results.

For example, the first result indicates that the terminal voltage of the suspended phase is equal to the neutral point voltage, the second result indicates that the terminal voltage of the suspended phase is not equal to the neutral point voltage, n is 1, the fifth comparison result group is 001100, the comparison result group in which 001100 appears shifted left by one bit includes 011000 and 011001, the comparison result group in which 001100 appears shifted right by one bit includes 100110 and 000110, the comparison result group in which the first 2n +1 comparison results in which the direction value is the first result and the second 2n +1 comparison results in which the direction value is the second result is 011000 and 011001, and the fourth comparison result group includes 011000 and 011001.

In this embodiment, if the direction values of the first 2n +1 comparison results of the first comparison result set are different from the direction values of the second 2n +1 comparison results, the first comparison result set is not any one or more of the following result sets: if the second comparison result group, the third comparison result group and the fourth comparison result group meet the first preset condition, judging that the first comparison result group meets the first preset condition; otherwise, the first comparison result group is judged not to meet the first preset condition.

In one implementation, the electronic device may determine whether the first comparison result group belongs to a comparison result group in a second preset zero-crossing table, and if the first comparison result group belongs to the comparison result group in the second preset zero-crossing table, the first comparison result group satisfies a first preset condition, and determines that the back electromotive force of the brushless dc motor crosses zero; otherwise, the first comparison result group does not meet the first preset condition, and the back electromotive force zero crossing of the brushless direct current motor is judged.

The comparison result group in the second preset zero-crossing table is a comparison result group which is obtained by randomly combining 4n +1 random comparison results and meets the following conditions: the direction values of the first 2n +1 comparison results are different from the direction values of the second 2n +1 comparison results, and are not the second comparison result group and/or the third comparison result group and/or the fourth comparison result group.

For example, n is 1, and the comparison result set in the second preset zero-crossing table is a comparison result set obtained by arbitrarily combining 4n +1 arbitrary comparison results and satisfying the following condition: the direction values of the first 2n +1 comparison results are the first results, and the direction values of the second 2n +1 comparison results are the second results, and are not the second comparison result group, the third comparison result group and the fourth comparison result group. The first result indicates that the terminal voltage of the suspended phase is equal to the neutral point voltage, the second result indicates that the terminal voltage of the suspended phase is not equal to the neutral point voltage, the second preset zero-crossing table is shown as table two, and the first preset zero-crossing table excludes the second comparison result group, the third comparison result group and the fourth comparison result group in the above example to obtain the comparison result.

Watch two

In the scheme provided by the application, the first preset condition further includes that the first comparison result group is not a comparison result group in which the pointing values of the first 2n +1 comparison results are different from the pointing values of the second 2n +1 comparison results due to noise interference, so that the interference of motor noise can be further eliminated, and the accuracy of counter potential zero-crossing detection is higher.

In addition, whether the counter potential crosses zero is judged by judging whether the first comparison result group belongs to a comparison result group in a second preset zero-crossing table, and the second preset zero-crossing table is compared with the first preset zero-crossing table to eliminate a comparison result group in which the directional values of the first 2n +1 comparison results are different from the directional values of the second 2n +1 comparison results due to noise interference, so that the interference of motor noise can be further eliminated, the number of the comparison result groups in the second preset zero-crossing table is fewer, and the calculation amount of counter potential zero-crossing detection is reduced.

Optionally, if the first comparison result group does not satisfy the first preset condition, the sampling window is moved backward and forward by one bit according to the time sequence, a new first comparison result group is obtained by resampling according to the moved sampling window, and whether the back electromotive force of the brushless dc motor crosses zero is determined according to the new first comparison result group until the back electromotive force crosses zero.

For example, the comparison results are a in the sequence of the comparison time₁、a₂、a₃、a₄、a₅、a₆And a is a first comparison result group generated by sampling in the current sampling window₁a₂a₃a₄a₅a₆If a₁a₂a₃a₄a₅a₆The electronic device may obtain the comparison result a when the first preset condition is not satisfied₆Then, the terminal voltage and the neutral point voltage of the suspension phase are compared again to obtain a comparison result a₇At this moment, the comparison result is a according to the sequence of the comparison time₁、a₂、a₃、a₄、a₅、a₆、a₇The electronic device may move the sampling window backward by one bit according to the time sequence, and obtain a new first comparison result group a by resampling according to the moved sampling window₂a₃a₄a₅a₆a₇Based on the newly obtained first comparison result set a₂a₃a₄a₅a₆a₇And judging whether the counter electromotive force of the brushless direct current motor is zero-crossed or not until the counter electromotive force zero-crossing is determined.

Optionally, if it is determined that the back electromotive force of the brushless dc motor crosses zero, the electronic device may control the brushless dc motor to perform phase commutation, and the specific processing procedure may be: if the back electromotive force of the brushless direct current motor is judged to be zero, determining the back electromotive force zero crossing time of the brushless direct current motor according to the comparison time of the comparison results in the first comparison result group; and taking the moment of the counter electromotive force zero crossing of the brushless direct current motor as a starting point, waiting for a first preset time period, and controlling the brushless direct current motor to change the phase, wherein the first preset time period is the time period required by the brushless direct current motor to change from the position of the counter electromotive force zero crossing to the position of a phase change point.

In the embodiment of the present application, if it is determined that the back electromotive force of the brushless dc motor crosses zero, the electronic device may determine the time when the back electromotive force of the brushless dc motor crosses zero according to the comparison time of the comparison results in the first comparison result group, for example, the electronic device may determine the comparison time of the 2n +1 th comparison result or the 2n +2 nd comparison result in the first comparison result group as the time when the back electromotive force of the brushless dc motor crosses zero.

Then, the electronic device may control the brushless dc motor to perform phase commutation after waiting for a first preset time period, starting from the determined time when the counter potential crosses zero. The first preset time period is a time period required for the brushless dc motor to transition from the position where the back emf zero-crossing exists to the position where the commutation point exists, for example, a time period required for the brushless dc motor to rotate by 30 electrical degrees.

According to the scheme, whether the back electromotive force of the brushless direct current motor crosses zero or not is determined through the first comparison result group generated by sampling of the sampling window set based on the preset filtering input number, the accuracy of back electromotive force zero crossing detection is improved, and therefore the phase change time of the brushless direct current motor is accurate.

Optionally, the specific processing procedure of determining the time when the back electromotive force of the brushless dc motor crosses zero according to the comparison time of the comparison result in the first comparison result group may be: an intermediate time between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result set is determined as the time at which the back emf of the brushless dc motor crosses zero.

For example, the comparison time t of the first comparison result in the first comparison result group₁₁The comparison time of the last comparison result is t₁₂The electronic device may then determine an intermediate time (t) between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result set₁₁+t₁₂) And/2, as the moment when the back electromotive force of the brushless direct current motor crosses zero.

In the scheme provided by the application, the middle time between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result group is used as the back electromotive force zero-crossing time of the brushless direct current motor, so that the determined back electromotive force zero-crossing time is higher in accuracy, and the phase change time of the brushless direct current motor is more accurate.

Based on the same technical concept, as shown in fig. 3, an embodiment of the present application further provides a back electromotive force zero-crossing detection apparatus for a brushless dc motor, where the apparatus includes:

a comparing module 301, configured to compare a terminal voltage of a suspension phase of the brushless dc motor with a neutral point voltage of a three-phase winding of the brushless dc motor, and obtain a corresponding comparison result;

a sampling module 302, configured to set sampling windows based on a preset number of filtering inputs, and sample the comparison results according to the corresponding sampling windows to generate a first comparison result group;

a determining module 303, configured to determine a back electromotive force zero crossing of the brushless dc motor according to the first comparison result set and perform phase commutation.

Optionally, the number of the filter inputs is 4n +2, and n is a positive integer.

Optionally, the number of the filter inputs is less than t1/t2, where t1 is a time period required for the brushless dc motor to rotate from a commutation point to a zero-crossing point, and t2 is a comparison period between a terminal voltage of the suspended phase and a neutral voltage of the three-phase winding.

Optionally, the determining module 303 includes:

a first determining unit, configured to determine whether the first comparison result group meets a first preset condition, where the first preset condition includes: the direction values of the first 2n +1 comparison results of the first comparison result group are different from the direction values of the second 2n +1 comparison results, wherein the direction value is the comparison result with the largest occurrence frequency in the 2n +1 comparison results;

a first determination unit configured to determine that a back electromotive force of the brushless dc motor crosses zero if the first preset condition is satisfied.

Optionally, the first preset condition further includes: the first comparison result set is not a comparison result set which causes pointing values of the first 2n +1 comparison results to be different from pointing values of the second 2n +1 comparison results due to noise interference.

Optionally, the determining module 303 further includes a second judging unit;

and the second judging unit is used for moving the sampling window backward by one bit according to a time sequence if the first preset condition is not met, resampling according to the moved sampling window to obtain a new first comparison result group, and judging whether the back electromotive force of the brushless direct current motor crosses zero according to the new first comparison result group until the back electromotive force crosses zero.

Optionally, the determining module 303 further includes a phase changing unit, where the phase changing unit includes:

a determining subunit, configured to determine, if it is determined that the back emf of the brushless dc motor crosses zero, a time at which the back emf of the brushless dc motor crosses zero according to a comparison time of the comparison results in the first comparison result group;

and the phase change subunit is used for controlling the brushless direct current motor to change the phase after waiting for a first preset time length by taking the moment of the counter potential zero crossing of the brushless direct current motor as a starting point, wherein the first preset time length is the time length required by the brushless direct current motor to change from the position of the counter potential zero crossing to the position of the phase change point.

Optionally, the determining subunit is specifically configured to:

determining an intermediate time between the comparison time of the first comparison result and the comparison time of the last comparison result in the first comparison result group as the time when the back emf of the brushless direct current motor crosses zero.

The embodiment of the application also provides a dust collector which comprises a brushless direct current motor, a memory and a processor;

a memory for storing a computer program;

and the processor is used for realizing the steps of the counter electromotive force zero-crossing detection method of any brushless direct current motor when executing the program stored in the memory.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the application to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, as for the embodiment of the device and the dust collector, the description is simple because the embodiment is basically similar to the embodiment of the method, and the relevant points can be referred to the part of the description of the embodiment of the method.

The above description is only for the preferred embodiment of the present application, and is not intended to limit the scope of the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application are included in the protection scope of the present application.