CN110838809A

CN110838809A - Counter potential zero-crossing detection method, device and control system for dust collector and motor

Info

Publication number: CN110838809A
Application number: CN201911184122.XA
Authority: CN
Inventors: 王浩东; 吴偏偏
Original assignee: Midea Group Co Ltd; Jiangsu Midea Cleaning Appliances Co Ltd
Current assignee: Midea Group Co Ltd; Jiangsu Midea Cleaning Appliances Co Ltd
Priority date: 2018-06-19
Filing date: 2018-06-19
Publication date: 2020-02-25
Anticipated expiration: 2038-06-19
Also published as: CN108809164B; CN110838809B; CN108809164A

Abstract

The invention discloses a counter electromotive force zero-crossing detection method, a counter electromotive force zero-crossing detection device and a counter electromotive force zero-crossing detection control system of a dust collector and a motor, wherein the counter electromotive force zero-crossing detection method of a brushless direct current motor comprises the following steps: acquiring time, counter potential zero-crossing detection advance time and follow current time interval corresponding to a half sector of the brushless direct current motor at the current rotating speed; acquiring a back electromotive force zero-crossing detection time gap of the brushless direct current motor according to the time corresponding to the half sector, the back electromotive force zero-crossing detection advance time and the follow current time interval; judging whether a back electromotive force zero-crossing detection time gap is entered; and if the back electromotive force zero-crossing detection time gap is entered, continuously sampling the back electromotive force of the brushless direct current motor for multiple times, and judging whether the back electromotive force crosses zero or not. The method can timely and accurately detect the counter potential zero crossing point, ensures that the motor stably runs at an extremely high rotating speed, does not need to additionally increase a comparator, and can reduce the cost.

Description

Counter potential zero-crossing detection method, device and control system for dust collector and motor

Technical Field

The invention relates to the technical field of motor control, in particular to a counter electromotive force zero-crossing detection method of a brushless direct current motor, a counter electromotive force zero-crossing detection device of the brushless direct current motor, a control system of the brushless direct current motor and a dust collector.

Background

At present, in the field of sensorless driving control technology of brushless dc motors, there are various methods for detecting the rotor position of the motor, among which the back electromotive force zero crossing method is simple, effective and widely used. The basic principle of the back electromotive force zero crossing method is that when the back electromotive force of a certain phase winding of the brushless direct current motor crosses zero, the direct axis of the rotor is just coincided with the axis of the phase winding, so that the position of the rotor of the motor can be obtained only by judging the back electromotive force zero crossing point of each phase winding.

In the related art, there are two methods for detecting the back emf zero crossing: firstly, sampling the terminal voltage of a suspension phase of the brushless direct current motor once in each PWM control period by adopting an ADC module, and then comparing a sampling result with a reference voltage to judge whether zero crossing occurs or not; and secondly, an external comparator is added, and the magnitude relation between the terminal voltage of the suspension phase of the brushless direct current motor and the reference voltage is compared by using hardware to realize counter potential zero-crossing detection.

However, the above detection method has the following disadvantages: 1) when the first counter potential zero-crossing detection method is adopted for counter potential zero-crossing detection, the detected counter potential zero-crossing time lags behind the actual counter potential zero-crossing time by about one PWM period, when the rotating speed of the brushless direct current motor is low and the duty ratio of a PWM (Pulse Width Modulation) control signal is small, a plurality of PWM periods exist in one phase change interval, and the influence of the lagged PWM period on the phase change of the brushless direct current motor is small; 2) when the back emf zero-crossing detection is performed by the second method, the cost is high due to the addition of the external comparator.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, a first objective of the present invention is to provide a counter potential zero crossing detection method for a brushless dc motor, which can not only timely and accurately detect counter potential zero crossing points and ensure that the motor stably operates at an extremely high rotation speed, but also reduce cost without adding an additional comparator.

A second object of the invention is to propose a non-transitory computer-readable storage medium.

A third object of the present invention is to provide a back emf zero crossing detection apparatus for a brushless dc motor.

A fourth object of the present invention is to provide a control system for a brushless dc motor.

A fifth object of the present invention is to provide a vacuum cleaner.

In order to achieve the above object, a counter potential zero crossing detection method for a brushless dc motor according to an embodiment of a first aspect of the present invention is characterized by comprising the following steps: acquiring time, counter potential zero-crossing detection advance time and follow current time interval corresponding to a half sector under the current rotating speed of the brushless direct current motor; acquiring a back electromotive force zero-crossing detection time gap of the brushless direct current motor according to the time corresponding to the half sector, the back electromotive force zero-crossing detection advance time and the follow current time interval; judging whether the back emf zero crossing detection time gap is entered; and if the counter electromotive force zero-crossing detection time gap is entered, continuously sampling the counter electromotive force of the brushless direct current motor for multiple times, and judging whether the counter electromotive force crosses zero or not.

According to the back emf zero-crossing detection method of the brushless direct current motor, the time corresponding to a half sector, the back emf zero-crossing detection advance time and the follow current time interval of the brushless direct current motor at the current rotating speed are obtained, the back emf zero-crossing detection time interval of the brushless direct current motor is obtained according to the time corresponding to the half sector, the back emf zero-crossing detection advance time and the follow current time interval, whether the back emf zero-crossing detection time interval enters or not is judged, when the back emf zero-crossing detection time interval enters, the back emf of the brushless direct current motor is continuously sampled for multiple times, and whether the back emf crosses zero or not is judged. Therefore, the back electromotive force zero crossing point can be timely and accurately detected, the motor can stably run at a high rotating speed, an extra comparator is not needed, and the cost can be reduced.

In addition, the back electromotive force zero-crossing detection method of the brushless dc motor according to the above embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the present invention, the acquiring a back emf zero crossing detection time gap of the brushless dc motor according to the time corresponding to the half sector, the back emf zero crossing detection advance time, and the freewheel time interval includes: and acquiring a difference value between the time corresponding to the half sector and the back emf zero crossing detection advance time, and enabling the difference value to be in the follow current time interval so as to obtain the back emf zero crossing detection time gap.

According to an embodiment of the present invention, the obtaining a time corresponding to a half sector of the current rotation speed of the brushless dc motor includes: acquiring the interval time of counter electromotive force zero crossing for the previous N times, wherein N is acquired according to the current rotating speed; and acquiring the time corresponding to the half sector under the current rotating speed according to the interval time of the counter electromotive force zero crossing of the previous N times.

According to an embodiment of the present invention, the obtaining a freewheel time interval of the brushless dc motor includes: acquiring the follow current time interval according to the highest running rotating speed of the brushless direct current motor; or obtaining the follow current time interval by looking up a table according to the current rotating speed; or obtaining the follow current time interval through a table look-up and linear interpolation algorithm according to the current rotating speed.

According to an embodiment of the present invention, the continuously sampling back emf of the brushless dc motor a plurality of times and determining whether the back emf crosses zero if the back emf zero-crossing detection time gap is entered includes: configuring a single channel of an ADC module as an AD channel corresponding to the voltage of a current suspended phase end when the back electromotive force zero-crossing detection time gap is entered, and triggering the single channel of the ADC module to sample the back electromotive force of the brushless direct current motor for the ith time, wherein i is an integer greater than or equal to 1; after the ith sampling is finished, acquiring an ith sampling result, triggering a single channel of the ADC module to perform (i + 1) th sampling on the counter electromotive force of the brushless direct current motor, and judging whether the counter electromotive force crosses zero or not according to the ith sampling result and a reference voltage in the (i + 1) th sampling process; exiting the back emf zero crossing detection phase if the back emf zero crosses.

According to an embodiment of the present invention, the back electromotive force zero-crossing detection method of the brushless dc motor further includes: and judging whether the time from the last commutation moment to the current time exceeds the difference between the time corresponding to the half sector and the back electromotive force zero-crossing detection advance time, and entering the back electromotive force zero-crossing detection time gap if the time from the last commutation moment to the current time exceeds the difference between the time corresponding to the half sector and the back electromotive force zero-crossing detection advance time.

According to one embodiment of the invention, the maximum electric speed of the brushless direct current motor reaches more than 80000 r/min.

To achieve the above object, a second embodiment of the present invention provides a non-transitory computer-readable storage medium, on which a computer program is stored, the program, when executed by a processor, implementing the counter potential zero crossing detection method of the brushless dc motor described above.

According to the non-transitory computer readable storage medium of the embodiment of the invention, by executing the counter potential zero crossing detection method of the brushless direct current motor, the counter potential zero crossing point can be timely and accurately detected, the motor can be ensured to stably operate at an extremely high rotating speed, and the cost can be reduced without additionally adding a comparator.

In order to achieve the above object, a counter potential zero crossing detecting apparatus for a brushless dc motor according to an embodiment of a third aspect of the present invention includes: the first acquisition unit is used for acquiring time, counter potential zero-crossing detection advance time and follow current time interval corresponding to a half sector of the brushless direct current motor at the current rotating speed, and acquiring counter potential zero-crossing detection time gap of the brushless direct current motor according to the time, the counter potential zero-crossing detection advance time and the follow current time interval corresponding to the half sector; a first judgment unit configured to judge whether the back emf zero-crossing detection time gap is entered; and the sampling unit is used for continuously sampling the counter electromotive force of the brushless direct current motor for multiple times in the counter electromotive force zero-crossing detection time interval and judging whether the counter electromotive force crosses zero or not.

According to the back emf zero-crossing detection device of the brushless direct current motor, the first obtaining unit obtains the time corresponding to a half sector, the back emf zero-crossing detection advance time and the follow current time interval of the brushless direct current motor at the current rotating speed, the back emf zero-crossing detection time interval of the brushless direct current motor is obtained according to the time corresponding to the half sector, the back emf zero-crossing detection advance time and the follow current time interval, the first judging unit judges whether the back emf zero-crossing detection time interval enters or not, the sampling unit continuously samples the back emf of the brushless direct current motor for multiple times when the back emf zero-crossing detection time interval enters, and whether the back emf crosses zero or not is judged. Therefore, the back electromotive force zero crossing point can be timely and accurately detected, the motor can stably run at a high rotating speed, an extra comparator is not needed, and the cost can be reduced.

In addition, the back electromotive force zero-crossing detection apparatus of the brushless dc motor according to the above-described embodiment of the present invention may further have the following additional technical features:

according to an embodiment of the present invention, the first obtaining unit is specifically configured to obtain a difference between a time corresponding to the half sector and the back emf zero crossing detection advance time, and make the difference be in the freewheel time interval, so as to obtain the back emf zero crossing detection time gap.

According to an embodiment of the present invention, the first obtaining unit is specifically configured to obtain counter potential zero-crossing interval time of the previous N times, and obtain time corresponding to a half sector under the current rotation speed according to the counter potential zero-crossing interval time of the previous N times, where N is obtained according to the current rotation speed.

According to an embodiment of the present invention, the first obtaining unit is specifically configured to obtain the freewheel time interval according to a maximum operating speed of the brushless dc motor; or obtaining the follow current time interval by looking up a table according to the current rotating speed; or obtaining the follow current time interval through a table look-up and linear interpolation algorithm according to the current rotating speed.

According to an embodiment of the present invention, the sampling unit is specifically configured to, when entering the back electromotive force zero-crossing detection time gap, configure a single channel of an ADC module as an AD channel corresponding to a current floating phase terminal voltage, trigger the single channel of the ADC module to sample the back electromotive force of the brushless dc motor for the ith time, and after the sampling for the ith time is completed, obtain a sampling result for the ith time, trigger the single channel of the ADC module to sample the back electromotive force of the brushless dc motor for the (i + 1) th time at the same time, and determine whether the back electromotive force crosses zero according to the sampling result for the ith time and a reference voltage in the sampling for the (i + 1) th time, and if the back electromotive force crosses zero, exit the back electromotive force zero-crossing detection stage, where i is an integer greater than or equal to 1.

According to an embodiment of the present invention, the first judging unit is specifically configured to judge whether or not the last commutation time to the present time exceeds the difference between the time corresponding to the half sector and the back electromotive force zero-crossing detection advance time, and enter the back electromotive force zero-crossing detection time gap if the last commutation time to the present time exceeds the difference between the time corresponding to the half sector and the back electromotive force zero-crossing detection advance time.

In order to achieve the above object, a fourth aspect of the present invention provides a control system for a brushless dc motor, which includes the counter potential zero crossing detection apparatus for the brushless dc motor.

According to the control system of the brushless direct current motor, through the counter electromotive force zero-crossing detection device of the brushless direct current motor, counter electromotive force zero-crossing points can be timely and accurately detected, the motor is guaranteed to stably operate at an extremely high rotating speed, a comparator does not need to be additionally arranged, and cost can be reduced.

In order to achieve the above object, a fifth aspect of the present invention provides a vacuum cleaner, which includes the above control system for the brushless dc motor.

According to the dust collector provided by the embodiment of the invention, through the control system of the brushless direct current motor, the back electromotive force zero crossing point can be timely and accurately detected, the motor is ensured to stably operate at an extremely high rotating speed, and the cost can be reduced without additionally increasing a comparator.

Drawings

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 invention;

fig. 2a is a terminal voltage waveform diagram of a phase a for one cycle;

fig. 2b is a terminal voltage waveform diagram of the phase a floating phase;

fig. 3 is a schematic diagram of back emf zero-crossing detection of a related art brushless dc motor;

FIG. 4 is a schematic diagram of a back-emf detection time gap according to one embodiment of the present invention;

fig. 5 is a flowchart of a back emf zero crossing detection method of a brushless dc motor according to another embodiment of the present invention;

FIG. 6 is a schematic diagram of a back-emf detection time gap according to another embodiment of the present invention;

7a-7b are schematic diagrams of back emf zero crossing detection for a brushless DC motor in accordance with one embodiment of the present invention;

8 a-8 c are flow diagrams of a back emf zero crossing detection method of a brushless DC motor in accordance with one embodiment of the present invention;

FIG. 9 is a schematic diagram of back emf zero crossing detection for a brushless DC motor in accordance with one embodiment of the present invention;

fig. 10 is a block schematic diagram of a back emf zero-crossing detection apparatus of a brushless dc motor according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

A counter potential zero-crossing detection method of a brushless dc motor, a non-transitory computer-readable storage medium, a counter potential zero-crossing detection apparatus of a brushless dc motor, a control system of a brushless dc motor, and a cleaner, which are proposed according to embodiments of the present invention, are described below with reference to the accompanying drawings.

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 invention. As shown in fig. 1, the back electromotive force zero-crossing detection method of the brushless dc motor according to the embodiment of the present invention includes the steps of:

and S1, acquiring the back electromotive force zero-crossing detection time gap of the brushless direct current motor.

S2, it is judged whether or not the back electromotive force zero-crossing detection time gap is entered. Wherein, whether to enter a counter electromotive force zero-crossing detection time gap is judged, namely whether to enter a counter electromotive force zero-crossing detection stage is judged.

And S3, if entering the counter electromotive force zero-crossing detection time gap, continuously sampling the counter electromotive force of the brushless direct current motor for multiple times, and judging whether the counter electromotive force crosses zero or not.

According to an embodiment of the present invention, before the back emf zero-crossing detection time gap of the brushless dc motor is acquired, the duty ratio of the PWM control signal of the brushless dc motor may also be acquired, and it is determined whether the duty ratio is greater than a first preset duty ratio. If the duty ratio is larger than a first preset duty ratio, acquiring a back electromotive force zero-crossing detection time gap of the brushless direct current motor, judging whether the back electromotive force zero-crossing detection time gap is entered, continuously sampling the back electromotive force of the brushless direct current motor for multiple times in the back electromotive force zero-crossing detection time gap, and judging whether the back electromotive force crosses zero; and if the duty ratio is smaller than a second preset duty ratio, sampling the back electromotive force of the brushless direct current motor once by a conventional back electromotive force sampling method in the PWM control period, and judging whether the back electromotive force crosses zero or not according to a sampling result, wherein the second preset duty ratio is smaller than the first preset duty ratio, and the calibration can be specifically carried out according to the actual situation.

Specifically, the back emf zero crossing detection compares the floating phase terminal voltage with a reference voltage. Taking phase a as an example, the voltage waveform of winding terminal of phase a in one cycle is shown in fig. 2a, wherein phase a is floating during BC and CB, and the voltage waveform of terminal thereof is shown in fig. 2 b. During PWM turn-on period, the voltage U of phase-A terminal_A＝e_A+1/2U_DCWhen U is formed_A＝1/2U_DCWhen e is present_A0, namely the zero crossing time of the opposite potential A; during PWM turn-off period, the voltage U of phase-A terminal_A＝e_AWhen U is formed_AWhen the value is 0, the zero-crossing time of the opposite potential of the A is obtained. Therefore, counter potential zero crossing detection is performed during PWM turn-on, reference voltage selection 1/2U_DCDuring the PWM off period, back emf zero crossing detection is performed, and the reference voltage is selected to be 0V.

In the related art, when the ADC module is used to sample the terminal voltage of the suspended phase once in each PWM control period, and the sampling result is compared with the reference voltage to determine whether the back emf crosses zero, the back emf zero crossing is detected during the PWM on period, for example. As shown in FIG. 2, during the BC turn-on period, the A-phase terminal voltage is in a rising trend, and is sampled once during each PWM turn-on period and compared with the reference voltage, and at the time a1 in FIG. 2b, U_A＜1/2U_DCThe back-emf does not cross zero, at time a2 of the next PWM control period, U_A＞1/2U_DCWhen it is detected that the back emf has crossed zero; similarly, during the CB on period, the voltage of the phase A end is in a descending trend, and at the moment b2, U is in the_A＞1/2U_DCCounter potential does not cross zero, and at time b3, U_A＜1/2U_DCWhen it is detected that the back emf has crossed zero.

The detected back emf zero-crossing time lags the actual back emf zero-crossing time by about one PWM control period, and under the condition of low rotating speed (low duty ratio), a plurality of PWM control periods exist in one phase change interval, so that the influence of one lagging PWM control period on phase change is small. However, when the brushless dc motor operates at a very high speed, such as 100000RPM (1 pole pair), the time of one phase sector is 100us, and one PWM control period is 50us (i.e. 20KHz, the frequency of the PWM control signal of the brushless dc motor is generally in the range of 5 to 30KHz, which would cause disadvantages to the switching loss, efficiency, heat dissipation, etc. of the power switching tube), at this time, there are at most 2 PWM control periods in one commutation interval, and each PWM control period only performs back electromotive force zero crossing sampling once, so that it is impossible to know whether the back electromotive force zero crossing in time, and it is very easy to cause the brushless dc motor step loss due to a large back electromotive force zero crossing detection lag.

Specifically, as shown in fig. 3, when the brushless dc motor is operated at an extremely high speed, only 2 PWM control periods are provided in one commutation interval, if the back emf sampling method is adopted, that is, the back emf AD sampling is performed once in both PWM control periods, which correspond to the times c1 and c2, respectively, and the actual back emf zero-crossing occurs after the time c1, so that the back emf zero-crossing cannot be detected in time in the first PWM control period, the back emf zero-crossing can be detected only at the time c2 of the second PWM control period, and the time c2 lags behind the real back emf zero-crossing point by about 1 PWM control period (about 1/2 commutation interval), which results in the lag of back emf zero-crossing detection, and consequently in the lag of commutation, which causes the bad conditions of large current ripple and even step loss.

Therefore, in the embodiment of the present invention, the operation of the brushless dc motor may be divided into two stages, a low-speed stage and a high-speed stage, respectively, and further, the operation of the brushless dc motor may be divided into a low-duty stage and a high-duty stage according to the duty ratio of the PWM control signal. In the low duty cycle phase (i.e., the low-speed phase), the conventional back electromotive force zero-crossing detection method is still adopted, for example, back electromotive force AD sampling is performed once in each PWM control period, and whether the back electromotive force crosses zero or not is judged according to the sampling result. When the duty ratio is increased to exceed a first preset duty ratio, a high duty ratio stage (namely, a high-speed stage) is entered, in the stage, because a follow current process exists after the brushless direct current motor is switched, the voltage of a suspended phase end is forcibly pulled to a bus voltage or a power ground during the follow current, and partial counter potential waveform is annihilated, so that counter potential zero-crossing detection during the follow current is ineffective, and meanwhile, if the counter potential zero-crossing detection is carried out immediately after the switching is finished, the counter potential zero-crossing detection can be influenced by a switching tube, so that the counter potential zero-crossing detection is inaccurate. Therefore, the counter electromotive force of the brushless direct current motor is continuously and repeatedly sampled when the counter electromotive force zero-crossing detection time gap is entered in each PWM control period in a high duty ratio stage, and whether the counter electromotive force crosses zero is judged. When the duty cycle again falls below a second preset duty cycle, the conventional back emf zero crossing detection method is reused.

Because the back electromotive force zero-crossing detection lag in the low duty cycle stage has almost no influence on the commutation of the brushless direct current motor, the control requirement can be met by adopting a conventional back electromotive force zero-crossing detection method in the low-speed operation stage of the brushless direct current motor, and the back electromotive force of the brushless direct current motor can be continuously sampled for multiple times in the back electromotive force zero-crossing detection time gap in the high duty cycle stage, so that the timeliness and the accuracy of the back electromotive force zero-crossing detection can be ensured, the brushless direct current motor can be supported to stably operate in an extremely high rotating speed range, an extra comparator is not needed, the cost can be reduced, and the size of a controller PCB (printed circuit board) is reduced.

It should be noted that, in practical application, the electric rotation speed of the brushless dc motor can reach above 80000 r/min.

According to one embodiment of the present invention, acquiring a back emf zero crossing detection time gap of a brushless dc motor comprises: acquiring the interval time of the counter electromotive force zero crossing for the previous N times, wherein N is acquired according to the current rotating speed; acquiring time corresponding to a half sector at the current rotating speed according to the interval time of the previous N counter electromotive force zero crossings; acquiring back electromotive force zero-crossing detection advance time of the brushless direct current motor; and acquiring the difference between the time corresponding to the half sector and the back electromotive force zero crossing detection advance time to obtain the back electromotive force zero crossing detection time gap.

According to an embodiment of the present invention, the back electromotive force zero-crossing detection method of the brushless dc motor further includes: and judging whether the time from the last commutation moment to the current time exceeds the difference value between the time corresponding to the half sector and the back electromotive force zero-crossing detection advance time, and entering a back electromotive force zero-crossing detection time gap if the time from the last commutation moment to the current time exceeds the difference value between the time corresponding to the half sector and the back electromotive force zero-crossing detection advance time.

According to an embodiment of the present invention, the time corresponding to a half sector at the current rotation speed can be obtained by the following formula:

wherein Ts0 is the time corresponding to half sector at the current rotation speed, Tzci is the ith counter potential zero-crossing interval time, and N is an integer greater than or equal to 1.

According to one embodiment of the present invention, acquiring a back emf zero crossing detection advance time of a brushless dc motor comprises: acquiring back electromotive force zero-crossing detection advance time according to the highest running rotating speed of the brushless direct current motor; or obtaining the back electromotive force zero-crossing detection advance time through a lookup table according to the current rotating speed; or acquiring the back electromotive force zero-crossing detection advance time by a table look-up and linear interpolation algorithm according to the current rotating speed.

Specifically, the back electromotive force zero-crossing detection of the back electromotive force zero-crossing detection time gap after the phase change of the brushless direct current motor can be obtained by comprehensively considering various factors which may influence the accuracy and timeliness of the back electromotive force zero-crossing detection. When acquiring the back emf zero-crossing detection time interval, the previous N back emf zero-crossing interval times (time intervals between two previous back emf zero-crossings) may be acquired, for example, the acquired previous N back emf zero-crossing interval times are Tzc1, Tzc2, Tzc3, Tzc4, …, and TzcN, respectively, and then the time Ts0 corresponding to a half sector (half sector corresponding to 30 ° electrical angle) at the current rotation speed is acquired according to the acquired previous N back emf zero-crossing interval times, as shown in the following formula (2):

the value of N is related to the current rotating speed of the brushless direct current motor, and in practical application, the N can be set in a segmented mode according to the rotating speed of the motor. For example, the brushless DC motor has a rotation speed range of w₀～w_x(x is an integer of 2 or more), the range of the rotation speed of the brushless DC motor can be divided into w₀～w₁、w₁～w₂、…、w_x-1～w_xX intervals in total, when the rotating speed of the brushless DC motor is in w₀～w₁When the value is within the range, the value of the corresponding N is N1; when the rotating speed of the brushless DC motor is at w₁～w₂When the value of the corresponding N is within the range, the value of the corresponding N is N₂(ii) a …, respectively; when the rotating speed of the brushless DC motor is at w_x-1～w_xWhen the value of the corresponding N is within the range, the value of the corresponding N is N_x。

It can be understood that if the brushless dc motor is operated at a constant speed, the time Ts0 corresponding to half a sector after the phase change of the brushless dc motor is exactly the time of the back emf zero crossing point, but in actual operation, the rotation speed of the brushless dc motor fluctuates, the time of each sector is not uniform, and when the load changes rapidly, the time of the sector also fluctuates. Therefore, in order to be able to reliably detect the counter potential zero-crossing point in time, the counter potential zero-crossing detection start timing needs to be slightly advanced, i.e., the counter potential zero-crossing detection is started a certain time before the expected counter potential zero-crossing point (i.e., the counter potential zero-crossing detection advance time Ta).

The back electromotive force zero-crossing detection advance time Ta of the brushless direct current motor can be determined by the following three methods: 1) the counter potential zero-crossing detection advance time Ta can be set to be a fixed value, and the fixed value can be configured according to the highest running rotating speed of the brushless direct current motor; 2) updating the back electromotive force zero-crossing detection advance time Ta in real time in a table look-up mode according to the rotating speed of the brushless direct current motor; 3) and updating the back electromotive force zero-crossing detection advance time Ta in real time by looking up a table and combining a linear interpolation algorithm according to the rotating speed of the brushless direct current motor.

Further, the back emf zero crossing detection advance time Ta is subtracted from the time Ts0 corresponding to half a sector to obtain the back emf zero crossing detection time gap start time. As shown in fig. 4, the time between the back emf zero-crossing detection time gap start time and the back emf zero-crossing detection time gap detection may be defined as a back emf zero-crossing detection time gap Tslot, no back emf zero-crossing detection is performed before entering the time gap, and after entering the time gap, i.e., when the back emf zero-crossing detection advance time Ta starts, the back emf is subjected to single-channel AD sampling a plurality of times in succession and compared with the reference voltage to determine whether the back emf zero-crossing.

According to another embodiment of the present invention, as shown in fig. 5, a back electromotive force zero-crossing detecting method of a brushless dc motor may include the steps of:

s401, acquiring time, counter potential zero-crossing detection advance time and follow current time interval corresponding to half sector of the brushless direct current motor at the current rotating speed.

S402, acquiring a back electromotive force zero-crossing detection time gap of the brushless direct current motor according to the time corresponding to the half sector, the back electromotive force zero-crossing detection advance time and the follow current time interval.

And S403, judging whether a back electromotive force zero-crossing detection time gap is entered. Wherein, whether to enter a counter electromotive force zero-crossing detection time gap is judged, namely whether to enter a counter electromotive force zero-crossing detection stage is judged.

S404, if the back electromotive force zero-crossing detection time gap is entered, continuously sampling the back electromotive force of the brushless direct current motor for multiple times, and judging whether the back electromotive force crosses zero or not.

That is, in the embodiment of the present invention, in addition to the counter potential zero-cross detection time gap Tslot that can be acquired from the time Ts0 corresponding to half a sector and the counter potential zero-cross detection advance time Ta, the counter potential zero-cross detection time gap Tslot can be acquired from the time Ts0 corresponding to half a sector, the counter potential zero-cross detection advance time Ta, and the free-wheeling time interval.

According to one embodiment of the invention, acquiring a back electromotive force zero-crossing detection time gap of a brushless direct current motor according to a time corresponding to a half sector, a back electromotive force zero-crossing detection advance time and a free-wheeling time interval comprises: and acquiring a difference value between the time corresponding to the half sector and the back emf zero-crossing detection advance time, and enabling the difference value to be in a follow current time interval so as to acquire a back emf zero-crossing detection time gap.

According to one embodiment of the invention, acquiring a freewheel time interval of a brushless direct current motor comprises: acquiring a follow current time interval according to the highest running rotating speed of the brushless direct current motor; or obtaining a follow current time interval through table look-up according to the current rotating speed; or acquiring a follow current time interval through a table look-up and linear interpolation algorithm according to the current rotating speed.

Specifically, the time Ts0 and the counter potential zero-crossing detection advance time Ta corresponding to a half sector of the current rotation speed of the brushless dc motor may be obtained in the foregoing manner, and then the counter potential zero-crossing detection advance time Ta is subtracted from the time Ts0 corresponding to the half sector to obtain the commutation freewheel time Tfw, that is, Tfw equals Ts0 — Ta, and the commutation freewheel time Tfw needs to satisfy tfw (min) ≦ Tfw ≦ tfw (max), that is, the commutation freewheel time Tfw needs to be within a freewheel time interval [ tfw (min), tfw (max) ].

Wherein, tfw (min) is a minimum phase commutation freewheel time threshold, and tfw (max) is a maximum phase commutation freewheel time threshold, which can be determined by the following three methods: 1) the minimum threshold value Tfw (min) of commutation follow current time and the maximum threshold value Tfw (max) of commutation follow current time can be set as fixed values respectively, and the fixed values can be configured according to the highest running rotating speed of the brushless direct current motor; 2) updating the minimum threshold value Tfw (min) of the commutation follow current time and the maximum threshold value Tfw (max) of the commutation follow current time in real time in a table look-up mode according to the rotating speed of the brushless direct current motor; 3) and updating the minimum threshold value Tfw (min) of the commutation follow current time and the maximum threshold value Tfw (max) of the commutation follow current time in real time by looking up a table and combining a linear interpolation algorithm according to the rotating speed of the brushless direct current motor.

Further, as shown in fig. 6, the end of the commutation freewheel time Tfw, that is, the back emf zero-crossing detection time gap start time, the time between the back emf zero-crossing detection time gap start time and the back emf zero-crossing detection time gap Tslot may be defined as the back emf zero-crossing detection time gap, no back emf zero-crossing detection is performed before entering the back emf zero-crossing detection time gap Tslot, and after entering the back emf zero-crossing detection time gap Tslot, the back emf is subjected to single-channel AD sampling for a plurality of consecutive times and compared with the reference voltage to determine whether the back emf zero-crossing exists.

The following describes in detail how to sample the back electromotive force of the brushless dc motor continuously for multiple times through a single channel of the AD module in combination with the back electromotive force zero-crossing detection time gap within the PWM control period, and determine whether the back electromotive force crosses zero based on the last sampling result in the sampling process, with reference to fig. 7 to 9.

According to an embodiment of the present invention, if a back electromotive force zero-crossing detection time gap is entered, continuously sampling a back electromotive force of a brushless dc motor a plurality of times and determining whether the back electromotive force crosses zero, includes: when a back electromotive force zero-crossing detection time gap is entered, configuring a single channel of an ADC module as an AD channel corresponding to the voltage of a current suspended phase end, and triggering the single channel of the ADC module to sample the back electromotive force of the brushless direct current motor for the ith time, wherein i is an integer greater than or equal to 1; after the ith sampling is finished, acquiring an ith sampling result, triggering a single channel of an ADC (analog to digital converter) module to carry out (i + 1) th sampling on the counter electromotive force of the brushless direct current motor, and judging whether the counter electromotive force crosses zero or not according to the ith sampling result and the reference voltage in the (i + 1) th sampling process; if the back emf crosses zero, the back emf zero crossing detection phase is exited.

Specifically, referring to fig. 7a-7b, in the process of controlling the brushless dc motor with the PWM control signal, the bus voltage AD sampling is triggered after the PWM control period is started and delayed for a first preset time (the duration of the time is configured by a software program, for example, 4us) (since the reference voltages for performing the back emf zero crossing detection during the high level and the low level of the PWM control signal are different, the bus voltage AD sampling is not required when performing the back emf zero crossing detection only during the low level of the PWM control signal). The AD sampling is carried out on the bus voltage after the first preset time, so that the bus voltage sampling is not accurate due to the influence of a power switch tube switch. In the first preset time, the duty ratio of the PWM control signal can be compared and judged, if the duty ratio is smaller than the second preset duty ratio, whether the counter potential crosses zero is judged by adopting a conventional counter potential sampling method, if yes, a counter potential zero-crossing detection stage is started after the bus voltage AD is sampled, at the moment, the single channel of an ADC (analog-to-digital converter) module is adopted to sample the voltage of the suspended phase end for one time, and the sampling result is compared with the reference voltage to judge whether the counter potential crosses zero; if the duty ratio is larger than the first preset duty ratio, the bus voltage AD is sampled and then enters a counter potential zero-crossing detection stage, in the stage, whether a counter potential zero-crossing detection time gap is entered or not is judged, if yes, the counter potential of the brushless direct current motor is continuously sampled for multiple times through a single channel of the ADC module, and whether the counter potential crosses zero or not is judged according to a last sampling result in the sampling process.

Specifically, as shown in fig. 7a-7b, after the AD sampling of the bus voltage is completed (about 1us), the AD interrupt is automatically generated, and after the AD interrupt is entered, the AD sampling result of the bus voltage is read, and the single channel of the ADC module is configured as the AD channel corresponding to the voltage at the current floating phase terminal, so as to prepare for the subsequent continuous multiple times of single-channel back-emf AD sampling. Then, there are two cases according to the back emf zero crossing detection time gap start time and the AD interrupt occurrence context.

In the first case, as shown in fig. 7a, the back-emf zero-crossing detection time gap has been entered after the entry of the AD interrupt (the corresponding entry back-emf zero-crossing detection phase flag bit has been set), then a single-channel back-emf AD sampling is performed a number of times in succession in the AD interrupt. The specific sampling process is as follows: the single channel triggering the ADC module firstly carries out first sampling on the counter electromotive force of the brushless direct current motor, after the first sampling is finished, the first sampling result is read, meanwhile, the single channel triggering the ADC module carries out second sampling on the counter electromotive force of the brushless direct current motor, in the process of the second sampling, the counter electromotive force is compared with reference voltage according to the first sampling result to judge whether the counter electromotive force crosses zero or not, if the counter electromotive force crosses zero, AD interruption is quitted, and counter electromotive force zero crossing detection of the current PWM control period is finished. If the back electromotive force does not cross zero, reading a second sampling result after the second sampling is finished, triggering a single channel of the ADC module to carry out third sampling on the back electromotive force of the brushless direct current motor, judging whether the back electromotive force crosses zero according to the second sampling result and the bus voltage in the third sampling process, and if the back electromotive force crosses zero, exiting AD interruption; if the counter potential does not cross zero, after the third sampling is finished, reading a third sampling result, triggering a single channel of the ADC module to carry out fourth sampling on the counter potential of the brushless direct current motor, …, after the ith sampling is finished, obtaining an ith sampling result, simultaneously triggering the single channel of the ADC module to carry out (i + 1) th sampling on the counter potential of the brushless direct current motor, judging whether the counter potential crosses zero or not according to the ith sampling result and the reference voltage in the (i + 1) th sampling process, and quitting AD interruption until the counter potential crosses zero or the sampling times are more than or equal to the preset times N or the PWM control period is finished.

In the above embodiment, the ith sampling result is obtained when the ith sampling is completed, and the (i + 1) th sampling of the counter potential is triggered at the same time, so that the counter potential zero-crossing judgment is performed by using the ith sampling result, and the (i + 1) th sampling and conversion of the counter potential are also performed automatically, which is beneficial to collecting the counter potential as much as possible in the PWM control period.

It should be noted that the preset number of times in the above embodiment is related to the current PWM control period, and N represents the maximum number of times of sampling the counter potential AD before the end of the current PWM control period.

In the second case, as shown in fig. 7b, after the AD interrupt is entered, the back emf zero-crossing detection time slot is not entered (the flag bit of the corresponding back emf zero-crossing detection phase is not set), the AD interrupt is exited, once the back emf zero-crossing detection time slot is entered, the back emf zero-crossing detection time slot TF is automatically entered, the flag bit of the back emf zero-crossing detection phase is set in the back emf zero-crossing detection time slot TF, and then the single-channel back emf AD sampling is performed for a plurality of consecutive times, and the specific sampling process is described in the foregoing, and will not be described in detail here.

In order to make the present invention more clear to those skilled in the art, the back electromotive force zero crossing detection method of the brushless dc motor will be further described below with reference to specific examples of the present invention.

Specifically, as shown in fig. 8a, the back electromotive force zero-crossing detection method of the brushless dc motor may include the steps of:

s501, after AD interruption, judging whether a back electromotive force zero-crossing detection time gap is entered. If so, i.e. case one as shown in FIG. 7a, step S502 is performed; if not, the AD interrupt is exited.

And S502, triggering single-channel counter potential AD sampling.

S503, it is determined whether the current counter potential AD sampling is finished. If yes, go to step S504; if not, step S503 is continued.

And S504, reading the counter potential AD sampling result.

And S505, judging whether the counter potential crosses zero or not according to the counter potential AD sampling result. If yes, go to step S507; if not, step S506 is performed.

And S506, judging whether the current PWM control period is finished. If yes, exiting AD interruption; if not, return to step S502.

And S507, quitting AD sampling and processing the counter potential zero-crossing time.

And S508, setting the zero-crossing detection success flag bit, and clearing the counter potential zero-crossing detection flag bit entering the counter potential zero-crossing detection stage.

S509, a delay commutation interruption TP is set.

Further, after detecting the back electromotive force zero crossing, a time-delay commutation interruption TP is entered to control the brushless dc motor to perform commutation, as shown in fig. 8b, and the specific method may include the following steps:

s601, judging whether the flag bit of the zero-crossing detection success is set. If yes, go to step S602; if not, exiting the delay commutation interruption TP.

And S602, controlling the brushless direct current motor to perform phase change operation.

S603, the phase is updated.

S604, clearing the flag bit of the zero-crossing detection success.

S605 sets the counter potential zero-crossing detection timing interrupt TF.

As shown in fig. 8c, the back emf zero crossing detection time gap has not been entered after the AD interrupt is entered, i.e. as in case two shown in fig. 7b, once the back emf zero crossing detection time gap is entered, the back emf zero crossing detection timed interrupt TF is automatically entered, and the back emf zero crossing detection method may comprise the steps of:

and S701, setting a zone bit entering a counter potential zero-crossing detection stage.

S702, the counter potential zero-crossing detection timer interrupt TF is stopped.

And S703, judging whether the current PWM control period is in. If so, go to step S704; if not, the back emf zero crossing detection timed interrupt TF is exited.

And S704, triggering single-channel counter potential AD sampling.

S705, it is determined whether the current counter potential AD sampling is finished. If yes, go to step S706; if not, execution continues with step S705.

S706, the counter potential AD sampling result is read.

And S707, judging whether the counter potential crosses zero according to the counter potential AD sampling result. If so, step S709 is performed. If not, step S708 is performed.

And S708, judging whether the current PWM control period is finished. If yes, quitting the back electromotive force zero-crossing detection timed interruption TF; if not, return to step S704.

S709, quitting the AD sampling and processing the back emf zero crossing time.

S710, setting a zero-crossing detection success flag bit, and clearing the counter potential zero-crossing detection flag bit entering the counter potential zero-crossing detection stage.

S711 sets a delay commutation interruption TP.

Therefore, in each PWM control period, whether counter potential zero-crossing detection is carried out in the counter potential zero-crossing detection time gap after AD interruption is generated can be judged according to the front-back relation between the counter potential zero-crossing detection time gap starting moment and the time for generating AD interruption, and then counter potential zero-crossing detection is carried out on the brushless direct current motor in different modes according to the judgment result, so that the purpose of carrying out counter potential zero-crossing judgment in the counter potential zero-crossing detection time gap is achieved.

Fig. 9 is a schematic diagram of back emf zero-crossing detection of a brushless dc motor according to an embodiment of the present invention, and as shown in fig. 9, during actual operation of the brushless dc motor, an advance time of the back emf zero-crossing detection may be calculated to obtain a back emf zero-crossing detection time gap Tslot, and the back emf zero-crossing detection performs a single-channel AD sampling on the back emf multiple times within the back emf zero-crossing detection time gap Tslot after the phase change of the brushless dc motor, that is, during each PWM period, if the back emf zero-crossing detection time gap Tslot is not entered, the back emf sampling is not performed, and once the back emf zero-crossing detection time gap Tslot is entered, the back emf sampling is performed continuously. Therefore, the back emf zero crossing point can be timely and accurately detected, the motor can be guaranteed to stably operate at a high rotating speed, the CPU occupancy rate can be reduced, meanwhile, a comparator does not need to be additionally arranged, and the cost can be reduced.

In summary, according to the back emf zero-crossing detection method of the brushless dc motor of the embodiment of the present invention, the time corresponding to the half sector at the current rotation speed of the brushless dc motor, the back emf zero-crossing detection advance time and the follow current time interval are first obtained, the back emf zero-crossing detection time interval of the brushless dc motor is obtained according to the time corresponding to the half sector, the back emf zero-crossing detection advance time and the follow current time interval, and whether the back emf zero-crossing detection time interval enters or not is determined, and the back emf of the brushless dc motor is continuously sampled for multiple times in the back emf zero-crossing detection time interval, and whether the back emf zero-crossing exists or not is determined. Therefore, the back electromotive force zero crossing point can be timely and accurately detected, the motor can stably run at a high rotating speed, an extra comparator is not needed, and the cost can be reduced.

In addition, an embodiment of the present invention also proposes a non-transitory computer-readable storage medium on which a computer program is stored, which when executed by a processor implements the counter potential zero crossing detection method of the brushless dc motor described above.

Fig. 10 is a block schematic diagram of a back emf zero-crossing detection apparatus of a brushless dc motor according to an embodiment of the present invention. As shown in fig. 10, the back electromotive force zero-crossing detection apparatus of a brushless dc motor according to an embodiment of the present invention may include a first acquisition unit 100, a first judgment unit 200, and a sampling unit 300.

The first acquiring unit 100 is configured to acquire a back emf zero-crossing detection time gap of the brushless dc motor; the first judgment unit 200 is used for judging whether a back electromotive force zero-crossing detection time gap is entered; the sampling unit 300 is configured to continuously sample the back electromotive force of the brushless dc motor multiple times in the back electromotive force zero crossing detection time interval, and determine whether the back electromotive force crosses zero.

According to an embodiment of the present invention, the first obtaining unit 100 is specifically configured to obtain the previous N times of back emf zero crossing interval time, and obtain a time corresponding to a half sector at the current rotation speed according to the previous N times of back emf zero crossing interval time, and obtain a back emf zero crossing detection advance time of the brushless dc motor, and obtain a difference between the time corresponding to the half sector and the back emf zero crossing detection advance time, so as to obtain a back emf zero crossing detection time gap, where N is obtained according to the current rotation speed.

According to an embodiment of the present invention, the first obtaining unit 100 obtains the time corresponding to half a sector at the current rotation speed by the following formula:

According to an embodiment of the present invention, the first obtaining unit 100 is specifically configured to obtain the back electromotive force zero-crossing detection advance time according to a maximum operation rotation speed of the brushless dc motor; or obtaining the back electromotive force zero-crossing detection advance time through a lookup table according to the current rotating speed; or acquiring the back electromotive force zero-crossing detection advance time by a table look-up and linear interpolation algorithm according to the current rotating speed.

According to an embodiment of the present invention, the sampling unit is specifically configured to configure a single channel of the ADC module as an AD channel corresponding to a current floating phase end voltage when entering a back electromotive force zero crossing detection time gap, trigger the single channel of the ADC module to sample a back electromotive force of the brushless dc motor for the ith time, obtain a sampling result for the ith time after the sampling for the ith time is completed, trigger the single channel of the ADC module to sample a back electromotive force of the brushless dc motor for the (i + 1) th time at the same time, determine whether the back electromotive force crosses zero according to the sampling result for the ith time and a reference voltage in the sampling for the (i + 1) th time, and exit a back electromotive force zero crossing detection stage if the back electromotive force crosses zero, where i is an integer greater than or equal to 1.

According to an embodiment of the present invention, the first determining unit 200 is specifically configured to determine whether the time from the last commutation time to the current time exceeds the difference between the time corresponding to the half sector and the back emf zero crossing detection advance time, and enter the back emf zero crossing detection time gap if the time from the last commutation time to the current time exceeds the difference between the time corresponding to the half sector and the back emf zero crossing detection advance time.

According to another embodiment of the present invention, the first obtaining unit 100 is further configured to obtain a time corresponding to half a sector of the current rotation speed of the brushless dc motor, a back emf zero crossing detection advance time, and a freewheel time interval, and obtain a back emf zero crossing detection time gap of the brushless dc motor according to the time corresponding to half the sector, the back emf zero crossing detection advance time, and the freewheel time interval; the first judgment unit 200 is used for judging whether a back electromotive force zero-crossing detection time gap is entered; the sampling unit 300 is configured to continuously sample the back electromotive force of the brushless dc motor multiple times during the back electromotive force zero-crossing detection time interval, and determine whether the back electromotive force crosses zero.

According to an embodiment of the present invention, the first obtaining unit 100 is specifically configured to obtain a difference value between a time corresponding to a half sector and a back emf zero crossing detection advance time, and make the difference value be in a freewheel time interval, so as to obtain a back emf zero crossing detection time gap.

According to an embodiment of the present invention, the first obtaining unit 100 is specifically configured to obtain a freewheel time interval according to a maximum operating speed of the brushless dc motor; or obtaining a follow current time interval through table look-up according to the current rotating speed; or acquiring a follow current time interval through a table look-up and linear interpolation algorithm according to the current rotating speed.

It should be noted that details that are not disclosed in the back electromotive force zero-crossing detection apparatus of the brushless dc motor according to the embodiment of the present invention refer to details that are disclosed in the back electromotive force zero-crossing detection method of the brushless dc motor according to the embodiment of the present invention, and detailed descriptions thereof are omitted here.

In addition, the embodiment of the invention also provides a control system of the brushless direct current motor, which comprises the counter electromotive force zero-crossing detection device of the brushless direct current motor.

In addition, the embodiment of the invention also provides a dust collector which comprises the control system of the brushless direct current motor.

It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.

In addition, in the description of the present invention, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. A back electromotive force zero-crossing detection method of a brushless direct current motor is characterized by comprising the following steps:

acquiring time, counter potential zero-crossing detection advance time and follow current time interval corresponding to a half sector under the current rotating speed of the brushless direct current motor;

acquiring a back emf zero-crossing detection time gap of the brushless direct current motor according to the time corresponding to the half sector, the back emf zero-crossing detection advance time and the follow current time interval, wherein before acquiring the back emf zero-crossing detection time gap of the brushless direct current motor, the method further comprises:

acquiring the duty ratio of a PWM control signal of the brushless direct current motor, and judging whether the duty ratio is larger than a first preset duty ratio;

if the duty ratio is larger than the first preset duty ratio, acquiring a back electromotive force zero-crossing detection time gap of the brushless direct current motor;

if the duty ratio is smaller than a second preset duty ratio, sampling the counter electromotive force of the brushless direct current motor once in a PWM control period by a conventional counter electromotive force sampling method, and judging whether the counter electromotive force crosses zero or not according to a sampling result, wherein the second preset duty ratio is smaller than the first preset duty ratio;

judging whether the back emf zero crossing detection time gap is entered;

and if the counter electromotive force zero-crossing detection time gap is entered, continuously sampling the counter electromotive force of the brushless direct current motor for multiple times, and judging whether the counter electromotive force crosses zero or not.

2. The counter potential zero-crossing detection method of a brushless dc motor according to claim 1, wherein said acquiring a counter potential zero-crossing detection time gap of the brushless dc motor based on the time corresponding to the half sector, the counter potential zero-crossing detection advance time, and the freewheel time interval comprises:

and acquiring a difference value between the time corresponding to the half sector and the back emf zero crossing detection advance time, and enabling the difference value to be in the follow current time interval so as to obtain the back emf zero crossing detection time gap.

3. The counter potential zero-crossing detection method of a brushless dc motor according to claim 1 or 2, wherein the acquiring a time corresponding to a half sector at a current rotation speed of the brushless dc motor includes:

acquiring the interval time of counter electromotive force zero crossing for the previous N times, wherein N is acquired according to the current rotating speed;

and acquiring the time corresponding to the half sector under the current rotating speed according to the interval time of the counter electromotive force zero crossing of the previous N times.

4. The counter potential zero-crossing detection method of a brushless dc motor according to claim 1 or 2, wherein the acquiring a freewheel time interval of the brushless dc motor includes:

acquiring the follow current time interval according to the highest running rotating speed of the brushless direct current motor; alternatively, the first and second electrodes may be,

obtaining the follow current time interval through table look-up according to the current rotating speed; alternatively, the first and second electrodes may be,

and acquiring the follow current time interval by a table look-up and linear interpolation algorithm according to the current rotating speed.

5. The counter potential zero-crossing detection method of a brushless dc motor according to claim 1, wherein the continuously sampling counter potentials of the brushless dc motor a plurality of times and determining whether the counter potentials cross zero if the counter potential zero-crossing detection time gap is entered comprises:

when the back electromotive force zero-crossing detection time gap is entered, configuring a single channel of an ADC module as an AD channel corresponding to the voltage of a current suspended phase end, and triggering the single channel of the ADC module to sample the back electromotive force of the brushless direct current motor for the ith time, wherein i is an integer greater than or equal to 1;

after the ith sampling is finished, acquiring an ith sampling result, triggering a single channel of the ADC module to perform (i + 1) th sampling on the counter electromotive force of the brushless direct current motor, and judging whether the counter electromotive force crosses zero or not according to the ith sampling result and a reference voltage in the (i + 1) th sampling process;

exiting the back emf zero crossing detection phase if the back emf zero crosses.

6. A back emf zero crossing detection method of a brushless dc motor as claimed in claim 2, further comprising:

judging whether the time from the last commutation moment to the current time exceeds the difference between the time corresponding to the half sector and the back electromotive force zero crossing detection advance time;

and if the time from the last commutation moment to the current time exceeds the difference between the time corresponding to the half sector and the back emf zero crossing detection advance time, entering the back emf zero crossing detection time gap.

7. A counter potential zero crossing detection method of a brushless DC motor according to any of claims 1-6, characterized in that the maximum electrical speed of the brushless DC motor is above 80000 r/min.

8. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that the program, when executed by a processor, implements a back emf zero crossing detection method of a brushless dc motor as claimed in any one of claims 1-7.

9. A back electromotive force zero-cross detection apparatus of a brushless dc motor, comprising:

the first acquisition unit is used for acquiring time, counter potential zero-crossing detection advance time and follow current time interval corresponding to a half sector of the brushless direct current motor at the current rotating speed, and acquiring counter potential zero-crossing detection time gap of the brushless direct current motor according to the time, the counter potential zero-crossing detection advance time and the follow current time interval corresponding to the half sector;

a first judgment unit configured to judge whether the back emf zero-crossing detection time gap is entered;

a sampling unit, configured to perform continuous multiple sampling on the back electromotive force of the brushless dc motor when entering the back electromotive force zero-crossing detection time gap, and determine whether the back electromotive force crosses zero, where the sampling module is further configured to, before the first obtaining unit obtains the back electromotive force zero-crossing detection time gap of the brushless dc motor:

if the duty ratio is larger than the first preset duty ratio, controlling the first acquisition unit to acquire a back electromotive force zero-crossing detection time gap of the brushless direct current motor;

and if the duty ratio is smaller than a second preset duty ratio, sampling the counter electromotive force of the brushless direct current motor once in a PWM control period by a conventional counter electromotive force sampling method, and judging whether the counter electromotive force crosses zero or not according to a sampling result, wherein the second preset duty ratio is smaller than the first preset duty ratio.

10. The counter potential zero-crossing detection apparatus of a brushless dc motor according to claim 9, wherein the first acquisition unit is specifically configured to acquire a difference value between a time corresponding to the half sector and the counter potential zero-crossing detection advance time, and to make the difference value in the freewheel time interval to obtain the counter potential zero-crossing detection time gap.

11. The back emf zero crossing detection apparatus of a brushless dc motor of claim 9 or 10, wherein the first obtaining unit is specifically configured to obtain a previous N back emf zero crossing interval times, and obtain a time corresponding to a half sector at the current rotation speed according to the previous N back emf zero crossing interval times, where N is obtained according to the current rotation speed.

12. The counter potential zero-crossing detection apparatus of a brushless dc motor according to claim 9 or 10, wherein the first obtaining unit is specifically configured to obtain the freewheel time interval according to a maximum operating rotation speed of the brushless dc motor; or obtaining the follow current time interval by looking up a table according to the current rotating speed; or obtaining the follow current time interval through a table look-up and linear interpolation algorithm according to the current rotating speed.

13. A counter potential zero-crossing detecting apparatus of a brushless DC motor according to claim 9,

the sampling unit is specifically configured to, when entering the back electromotive force zero-crossing detection time gap, configure a single channel of an ADC module as an AD channel corresponding to a current suspended phase end voltage, trigger the single channel of the ADC module to sample the back electromotive force of the brushless dc motor for the ith time, acquire an ith sampling result after the ith sampling is completed, trigger the single channel of the ADC module to sample the back electromotive force of the brushless dc motor for the (i + 1) th time at the same time, determine whether the back electromotive force crosses zero according to the ith sampling result and the reference voltage in the (i + 1) th sampling process, and exit the back electromotive force zero-crossing detection stage if the back electromotive force crosses zero, where i is an integer greater than or equal to 1.

14. The counter potential zero-crossing detection apparatus of a brushless dc motor according to claim 10, wherein the first judgment unit is specifically configured to judge whether or not the last commutation time to the present time exceeds the difference between the time corresponding to the half sector and the counter potential zero-crossing detection advance time, and enter the counter potential zero-crossing detection time gap if the last commutation time to the present time exceeds the difference between the time corresponding to the half sector and the counter potential zero-crossing detection advance time.

15. A counter potential zero crossing detection apparatus of a brushless dc motor according to any one of claims 9 to 14, wherein a maximum electric rotation speed of the brushless dc motor reaches 80000r/min or more.

16. A control system of a brushless dc motor, characterized by comprising a back electromotive force zero-cross detection apparatus of a brushless dc motor according to any one of claims 9 to 15.

17. A vacuum cleaner comprising a control system for a brushless dc motor according to claim 16.