阅读说明：本技术 吸尘器、电机的反电势过零检测方法、装置和控制系统 (Counter potential zero-crossing detection method, device and control system for dust collector and motor ) 是由 万德康 王浩东 吴偏偏 于 2018-03-30 设计创作，主要内容包括：本发明公开了一种吸尘器、无刷直流电机的反电势过零检测方法、装置和控制系统,其中,无刷直流电机的反电势过零检测方法包括以下步骤：在每个PWM控制周期内采用中心对称的PWM控制信号对无刷直流电机进行控制,并判断PWM控制信号的占空比是否大于第一预设占空比；如果占空比大于第一预设占空比,则在PWM控制周期内通过硬件触发方式触发ADC单通道每隔第一预设时间对无刷直流电机的反电势进行采样,并在每次采样完成后根据采样结果判断反电势是否过零。该方法不仅能够及时、准确地检测到反电势过零点,保证电机稳定运行在极高转速,而且无需额外增加比较器,能够降低成本。(The invention discloses a dust collector, a back electromotive force zero-crossing detection method and device of a brushless direct current motor and a control system, wherein the back electromotive force zero-crossing detection method of the brushless direct current motor comprises the following steps: adopting centrosymmetric PWM control signals to control the brushless direct current motor in each PWM control period, and judging whether the duty ratio of the PWM control signals is greater than a first preset duty ratio; if the duty ratio is larger than a first preset duty ratio, triggering an ADC single channel to sample the counter electromotive force of the brushless direct current motor every first preset time in a PWM control period in a hardware triggering mode, and judging whether the counter electromotive force crosses zero or not according to a sampling result after sampling is completed every time. 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.)

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

s1, adopting centrosymmetric PWM control signals to control the brushless direct current motor in each PWM control period, and judging whether the duty ratio of the PWM control signals is larger than a first preset duty ratio;

s2, if the duty ratio is larger than the first preset duty ratio, triggering an ADC single channel to sample the counter electromotive force of the brushless direct current motor every first preset time in the PWM control period in a hardware triggering mode, and judging whether the counter electromotive force crosses zero or not according to a sampling result after each sampling is finished;

and S3, if the duty ratio is smaller than a second preset duty ratio, sampling the counter electromotive force of the brushless direct current motor once within the high level time of the PWM control period by a conventional counter electromotive force sampling method, and judging whether the counter electromotive force crosses zero or not according to the sampling result, wherein the second preset duty ratio is smaller than the first preset duty ratio.

2. The counter potential zero-crossing detection method of a brushless dc motor according to claim 1, wherein in sampling the counter potential of the brushless dc motor every first preset time, it is further determined whether a current time is a high level middle time of the PWM control period, and if so, the sampling of the counter potential of the brushless dc motor is stopped, and a bus current ADC sampling is triggered to obtain a bus current of the brushless dc motor.

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

judging whether the current time is the starting time of the PWM control period or not;

if so, triggering bus voltage ADC sampling to obtain the bus voltage of the brushless direct current motor, and configuring the ADC single channel so that the ADC single channel samples the counter electromotive force of the brushless direct current motor every first preset time;

after configuration is completed, the ADC single channel starts to sample the counter electromotive force of the brushless direct current motor every other first preset time, whether the counter electromotive force crosses zero is judged according to a sampling result and the bus voltage, and whether the sampling frequency of the counter electromotive force is larger than or equal to a first preset frequency is judged at the same time, wherein the first preset frequency is obtained according to the PWM control period and the first preset time;

and if the sampling times of the counter electromotive force are more than or equal to the first preset times, judging that the current time is the middle time of the high level of the PWM control period.

4. The counter potential zero crossing detection method of a brushless dc motor according to claim 3, wherein after obtaining the bus current of the brushless dc motor, the ADC single channel is further configured such that the ADC single channel samples the counter potential of the brushless dc motor every first preset time;

after configuration is completed, the ADC single channel starts to sample the counter electromotive force of the brushless direct current motor every other first preset time, and whether the counter electromotive force crosses zero or not is judged according to a sampling result and the bus voltage until the counter electromotive force crosses zero or the next PWM control period is judged.

5. A non-transitory computer-readable storage medium having stored thereon a computer program, characterized in that the program, when executed by a processor, implements the back emf zero-crossing detection method of a brushless dc motor as claimed in any one of claims 1-4.

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

the control unit is used for controlling the brushless direct current motor by adopting centrosymmetric PWM control signals in each PWM control period;

the judging unit is used for judging whether the duty ratio of the PWM control signal is larger than a first preset duty ratio or not;

the sampling unit is used for triggering an ADC single channel to sample the counter electromotive force of the brushless direct current motor every first preset time in the PWM control period in a hardware triggering mode when the duty ratio is larger than the first preset duty ratio, and judging whether the counter electromotive force crosses zero or not according to a sampling result after sampling is completed each time; wherein the content of the first and second substances,

the sampling unit is further configured to, when the duty ratio is smaller than a second preset duty ratio, perform primary sampling on the back electromotive force of the brushless dc motor by using a conventional back electromotive force sampling method within a high level time of the PWM control period, and determine whether the back electromotive force crosses zero according to a sampling result, where the second preset duty ratio is smaller than the first preset duty ratio.

7. The counter potential zero-crossing detection apparatus of a brushless dc motor according to claim 6, wherein the sampling unit is further configured to determine whether a current time is a high level middle time of the PWM control period during sampling the counter potential of the brushless dc motor every first preset time, and if so, stop sampling the counter potential of the brushless dc motor and trigger a bus current ADC sampling to obtain a bus current of the brushless dc motor.

8. The apparatus of claim 7, wherein the sampling unit is further configured to determine whether a current time is a start time of the PWM control period, trigger a bus voltage ADC to sample to obtain a bus voltage of the brushless dc motor if the current time is the start time of the PWM control period, and configure the ADC single channel such that the ADC single channel samples the back emf of the brushless dc motor every first preset time;

after configuration is completed, the ADC single channel starts to sample the counter electromotive force of the brushless direct current motor every other first preset time, the sampling unit judges whether the counter electromotive force crosses zero or not according to a sampling result and the bus voltage, and simultaneously judges whether the sampling frequency of the counter electromotive force is larger than or equal to a first preset frequency or not, wherein the first preset frequency is obtained according to the PWM control period and the first preset time;

and if the sampling frequency of the counter electromotive force is more than or equal to the first preset frequency, the sampling unit judges that the current time is the middle time of the high level of the PWM control period.

9. The apparatus of claim 8, wherein after obtaining the bus current of the brushless dc motor, the sampling unit is further configured to configure the ADC single channel such that the ADC single channel samples the back emf of the brushless dc motor every first preset time;

after configuration is completed, the ADC single channel starts to sample the counter electromotive force of the brushless direct current motor every other first preset time, and the sampling unit judges whether the counter electromotive force crosses zero or not according to a sampling result and the bus voltage until the counter electromotive force crosses zero or enters the next PWM control period.

10. 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 6 to 9.

11. A vacuum cleaner comprising a control system for a brushless dc motor according to claim 10.