CN115037196B - DC brushless motor rotation control method and singlechip - Google Patents
DC brushless motor rotation control method and singlechip Download PDFInfo
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- CN115037196B CN115037196B CN202210778764.8A CN202210778764A CN115037196B CN 115037196 B CN115037196 B CN 115037196B CN 202210778764 A CN202210778764 A CN 202210778764A CN 115037196 B CN115037196 B CN 115037196B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/14—Electronic commutators
- H02P6/16—Circuit arrangements for detecting position
- H02P6/18—Circuit arrangements for detecting position without separate position detecting elements
- H02P6/182—Circuit arrangements for detecting position without separate position detecting elements using back-emf in windings
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P2203/00—Indexing scheme relating to controlling arrangements characterised by the means for detecting the position of the rotor
- H02P2203/03—Determination of the rotor position, e.g. initial rotor position, during standstill or low speed operation
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Abstract
The invention discloses a DC brushless motor rotation control method and a singlechip, wherein the method comprises the following steps: pre-positioning the motor to determine an initial position of a motor rotor; outputting pulse width modulation signals to control the motor to accelerate in stages so as to detect counter electromotive force and zero crossing points, and counting the times of the detected zero crossing points; when the number of detected zero crossing points reaches the threshold value of the number of zero crossing points, a high-level signal with fixed duration is output to drive the motor to rotate, and the counter electromotive force of the motor is sampled to control the motor to rotate. After the motor is pre-positioned, the motor is controlled to be started in an acceleration way by adopting the pulse width modulation signal so as to quickly detect the counter electromotive force and the zero crossing point, and after the zero crossing point reaches the threshold value of the number of times of the zero crossing point, the pulse width modulation signal of the driving signal of the motor is adjusted to be a high-level signal with fixed duration, so that the counter electromotive force detected by the singlechip is a continuous signal, and the accuracy of the sampling result of the singlechip is ensured.
Description
Technical Field
The invention relates to the technical field of motor control, in particular to a DC brushless motor rotation control method and a singlechip.
Background
With the continuous expansion of the application market demand of the brushless DC motor, the excellent performance and reliability of the brushless DC motor emit light and heat in the fields of household appliances, automatic tools, industrial control and the like. In a non-inductive square wave control system of a direct current brushless motor, the purpose of controlling the rotation of the motor is achieved by sampling and detecting three-phase counter electromotive force of the motor and then judging a zero crossing point to change phases, in a general scheme, a hardware comparator or an Analog-to-Digital Converter (ADC) sampling mode is adopted to compare the counter electromotive force of the motor, so as to judge the zero crossing point.
In the scheme of the hardware comparator, a plurality of hardware comparators are needed, the hardware cost is increased, the hardware circuits for different applications are needed to be adapted, and the scheme is not good in adaptability and is not universal enough.
The method for comparing the counter electromotive force by using the software algorithm is not limited by a motor and a circuit, the comparison is flexible, the counter electromotive force waveform can be regarded as a PWM waveform, in the current singlechip (Micro Control Unit, MCU), the ADC can only sample in a high level part or a low level part of the PWM waveform, the PWM waveform can change along with the change of the motor speed, and when the motor rotates at a high speed, the sampling range of the counter electromotive force waveform becomes very narrow, so that the sampling error of the ADC becomes large, the motor rotates to generate violent pulsation, and even the motor stops rotating.
Accordingly, the prior art is still in need of improvement and development.
Disclosure of Invention
In view of the defects in the prior art, the invention aims to provide a direct current brushless motor rotation control method and a singlechip, so as to solve the problems of violent pulsation and even stopping rotation of motor rotation caused by sampling errors in the back electromotive force of the motor sampled by the singlechip.
The technical scheme of the invention is as follows:
a method of controlling rotation of a brushless dc motor, comprising:
pre-positioning the motor to determine an initial position of a motor rotor;
outputting pulse width modulation signals to control the motor to accelerate in stages so as to detect counter electromotive force and zero crossing points, and counting the times of the detected zero crossing points;
when the number of detected zero crossing points reaches the threshold value of the number of zero crossing points, a high-level signal with fixed duration is output to drive the motor to rotate, and the counter electromotive force of the motor is sampled to control the motor to rotate.
In a further arrangement of the present invention, the step of outputting the pulse width modulation signal to control the motor to accelerate to rotate so as to detect the back electromotive force and the zero crossing point and count the number of times of the detected zero crossing point includes:
outputting a pulse width modulation signal according to a target speed value to control the motor to rotate at the 1 st stage speed so as to detect a first zero crossing point and count the times of the detected zero crossing point;
accelerating the motor to rotate at the 2 nd stage by adjusting the duty ratio of the pulse width modulation signal so as to detect a second zero crossing point and count the number of times of the detected zero crossing point;
the motor is rotated at an nth stage by adjusting the duty ratio of the pulse width modulation signal to detect an nth zero crossing point and count the number of times of the detected zero crossing point.
According to the invention, after the number of detected zero crossing points reaches the threshold value of the number of zero crossing points, a high level with fixed duration is output to drive the motor to rotate, and the counter electromotive force of the motor is sampled to control the motor to rotate, and the method comprises the following steps:
detecting the times of zero crossing points;
judging the number of zero crossing points and the threshold value of the number of zero crossing points;
when the rotation speed of the motor is detected to reach a speed convergence value and the number of times of detecting the zero crossing point reaches a zero crossing point number threshold, switching a driving signal of the motor into a high-level signal with fixed duration;
the back emf of the motor is sampled to control the motor rotation.
The invention further provides that the step of outputting the pulse width modulation signal to control the motor to accelerate in stages to detect the back electromotive force and the zero crossing point and count the number of times of the detected zero crossing point further comprises the steps of:
judging whether the counter electromotive force can be detected, and if the counter electromotive force is not detected within the preset time, alarming and controlling the motor to stop rotating.
According to the invention, after the number of detected zero crossing points reaches the zero crossing point number threshold, a high-level signal with fixed duration is output to drive the motor to rotate, and the counter electromotive force of the motor is sampled to control the motor to rotate, and the method further comprises the steps of:
if the number of times of detecting zero crossing points reaches the threshold value of the number of times of zero crossing points, the driving signal of the motor is not switched to a high-level signal with fixed duration, and then the motor is alarmed and controlled to stop rotating.
The invention further provides that the method for controlling the rotation of the brushless DC motor further comprises the following steps:
and presetting the threshold value of the zero crossing times.
According to the invention, the threshold value of the zero crossing frequency is more than or equal to 2.
The invention further provides that the DC brushless motor rotation control method further comprises the following steps:
and presetting a speed convergence value of the motor according to the target speed value.
According to the further arrangement of the invention, when the motor is started in an acceleration mode, the duty ratio of the pulse width modulation signal increases in a linear trend.
Based on the same inventive concept, the invention also provides a singlechip, which comprises a processor and a memory, wherein the memory stores a computer program, and the processor realizes the steps of the method when executing the computer program.
The invention provides a DC brushless motor rotation control method and a singlechip, wherein the method comprises the following steps: pre-positioning the motor to determine an initial position of a motor rotor; outputting pulse width modulation signals to control the motor to accelerate in stages so as to detect counter electromotive force and zero crossing points, and counting the times of the detected zero crossing points; when the number of detected zero crossing points reaches the threshold value of the number of zero crossing points, a high-level signal with fixed duration is output to drive the motor to rotate, and the counter electromotive force of the motor is sampled to control the motor to rotate. After the motor is pre-positioned, the pulse width modulation signal is adopted to control the motor to start up in an accelerating way so as to quickly detect the counter electromotive force and the zero crossing point, and after the zero crossing point reaches the threshold value of the number of times of the zero crossing point, the pulse width modulation signal of the driving signal of the motor is adjusted to be a high-level signal with fixed duration, so that the counter electromotive force detected by the singlechip is a continuous signal, the accuracy of the sampling result of the singlechip is ensured, and the problem that the motor rotates violently and even stops rotating due to sampling errors of the counter electromotive force of the singlechip is prevented.
Drawings
In order to more clearly illustrate the embodiments of the present invention 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.
Fig. 1 is a schematic diagram of a conventional motor starting process.
Fig. 2 is a flow chart of a method for controlling rotation of a brushless dc motor according to the present invention.
Fig. 3 is a schematic diagram of controlling rotation of a motor by using a brushless dc motor rotation control method according to the present invention.
Fig. 4 is a schematic diagram of a specific control flow for controlling rotation of a motor according to an embodiment of the present invention.
Detailed Description
The invention provides a DC brushless motor rotation control method and a singlechip, which are used for making the purposes, technical schemes and effects of the invention clearer and more definite, and the invention is further described in detail below by referring to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
In the description and claims, unless the context specifically defines the terms "a," "an," "the," and "the" include plural referents. If there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature.
It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The term "and/or" as used herein includes all or any element and all combination of one or more of the associated listed items.
It will be understood by those skilled in the art that all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs unless defined otherwise. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
The inventor researches that in the current singlechip, the ADC can only be used for sampling in a high level part or a low level part of the PWM waveform, and the PWM waveform can be changed along with the change of the motor speed. When the motor rotates at a high speed, the sampling range of the back electromotive force waveform becomes very narrow, so that the ADC sampling error becomes large, and the motor rotates to generate violent pulsation, and even stops rotating. In particular, this phenomenon is evident in high-speed motor applications such as blowers, medical power tools, molecular pumps, etc. The control method of the motor is as follows: after the initial position of the rotor is found through pre-positioning, a target speed is given, the motor is driven by a control algorithm, the actual speed is slowly increased in a slope mode, after the motor enters a closed loop, the motor is driven by a PWM signal continuously, the starting process of the existing scheme is as shown in figure 1, in the open loop stage of the motor, the motor is pre-positioned firstly, the motor system starts to work, the duty ratio of the PWM signal starts to gradually and linearly rise, after T1 (the time point when the motor starts to rotate after the motor is pre-positioned), when the duty ratio reaches the point A in the graph, enough force is provided to enable the motor to start rotating, the preset positioning stage is ended, the climbing stage is started, the motor speed starts to slowly increase after the moment T1, when the moment B in the graph at the moment T2 (the zero crossing point of the counter electromotive force can be detected), the counter electromotive force can be detected, the zero crossing point can also be detected, the number of times of the zero crossing point is counted, when the set value is exceeded, the moment T3 (when the zero crossing point of a certain number of times is detected, the closed loop is entered) is reached, and the motor is cut into the closed loop; in the closed loop phase of the motor, when the rotation speed of the motor reaches the point C in the figure at the time T3, the system enters the closed loop, the PWM duty ratio of the driving signal still continues to increase, the speed slowly increases to a speed target value, such as 10 ten thousand revolutions per minute, and then constant-speed rotation is started, and the duty ratio of the driving signal is also constant. However, if the motor speed is too high, the counter electromotive force waveform sampling window time becomes smaller than the ADC sampling period of the MCU, so that sampling errors can be caused, and if the control is not good, the motor is stopped or the power consumption becomes large. In addition, the whole open-closed loop is the value of the counter electromotive force detected by the ADC in the whole process to judge the zero crossing point, no matter how fast or slow, the whole process is to remove the sampling when the counter electromotive force PWM is high or low, and the software algorithm is used for comparing and judging the zero crossing point.
In order to solve the technical problems, the invention provides a direct current brushless motor rotation control method and a singlechip, which are characterized in that after a motor is pre-positioned, a pulse width modulation signal is adopted to control the motor to start up in an accelerating way so as to rapidly detect counter electromotive force and zero crossing points, and after the zero crossing points reach a zero crossing point frequency threshold value, a driving signal pulse width modulation signal of the motor is adjusted to be a high-level signal with fixed duration, so that the counter electromotive force detected by the singlechip is a continuous signal, even if the motor is in a high-speed running state, the accuracy of a sampling result of the singlechip can be ensured, and the problem that the rotation of the motor is violently pulsed even stopped due to sampling errors of the counter electromotive force of the singlechip sampling motor is prevented. In addition, in the closed loop stage, a high-level signal with fixed duration is adopted to drive the motor, the requirement on the MCU is low, and the cost is also reduced.
Referring to fig. 2 to 4, the present invention provides a method for controlling rotation of a brushless dc motor.
As shown in fig. 1 and 2, the present invention provides a method for controlling rotation of a brushless dc motor, comprising the steps of:
s100, pre-positioning the motor to determine the initial position of a motor rotor;
s200, outputting pulse width modulation signals to control the motor to accelerate in a stage mode so as to detect counter electromotive force and zero crossing points, and counting the times of the detected zero crossing points;
and S300, outputting a high-level signal with fixed duration to drive the motor to rotate after the number of detected zero crossing points reaches a zero crossing point number threshold, and sampling the counter electromotive force of the motor to control the motor to rotate.
Specifically, the starting process of the singlechip-controlled motor comprises an open-loop stage and a closed-loop stage, wherein the open-loop stage comprises a pre-positioning stage and an acceleration stage. In the pre-positioning stage, the AB and BC phases of the motor are electrified firstly to find the accurate position of the motor rotor, so that the initial position of the motor rotor is determined. In the acceleration stage, a driving signal of the motor adopts a pulse width modulation signal, the singlechip enables the motor to accelerate and rotate by changing the duty ratio of the pulse width modulation signal so as to rapidly detect counter electromotive force and zero crossing points, counts the times of the zero crossing points, enters a closed loop stage of the motor when the times of the zero crossing points reach a threshold value of the times of the zero crossing points, adjusts the driving signal of the motor into a high-level signal with fixed duration by the pulse width modulation signal, drives the motor to rotate by the high-level signal with fixed duration, the counter electromotive force detected by the singlechip is a continuous signal at the moment, and the waveform of the detected counter electromotive force is a continuous slope, so that the counter electromotive force detected by the singlechip is a continuous value, and the sampling result is more accurate.
Therefore, after the motor enters a closed loop stage, the motor is driven by a high-level signal with fixed duration, the counter electromotive force detected by the singlechip is a continuous signal, the waveform of the detected counter electromotive force is a continuous slope, and even if the motor is in a high-speed or even ultra-high-speed running state, the singlechip can accurately sample, so that the accuracy of the sampling result of the singlechip is ensured, the problem that the motor rotates to violent pulsation or even stops rotating due to sampling errors of the counter electromotive force of the singlechip is prevented, and the operation difficulty and complexity are not increased compared with the original control mode. In addition, in the closed loop stage, a high-level signal with fixed duration is adopted to drive the motor, the requirement on the MCU is low, and the cost is also reduced. In addition, the invention drives the motor by adopting the high level with fixed duration, namely, the fixed level is adopted to control the switching tube, and compared with the pulse width modulation signal driving switching tube, the frequency of a conducting medium of the switching tube can be greatly reduced, thereby prolonging the service life of the switching tube, being particularly suitable for high-speed motors and improving the competitiveness of the high-speed motors.
In some embodiments, step S200 specifically includes the steps of:
s210, outputting a pulse width modulation signal according to a target speed value to control the motor to rotate at the 1 st stage speed so as to detect a first zero crossing point and count the number of times of the detected zero crossing point;
s220, enabling the motor to rotate in an acceleration mode at a 2 nd stage by adjusting the duty ratio of the pulse width modulation signal so as to detect a second zero crossing point, and counting the number of times of the detected zero crossing point;
s230, enabling the motor to rotate in an acceleration mode at an nth stage by adjusting the duty ratio of the pulse width modulation signal so as to detect an nth zero crossing point, and counting the number of times of the detected zero crossing point.
Specifically, in the acceleration start stage of the motor, the duty ratio of the pulse width modulation signal is linearly increased, that is, the motor adopts a gradual acceleration mode in the acceleration stage, during the acceleration process, the singlechip detects the counter electromotive force and the zero crossing point, when the counter electromotive force and the zero crossing point can be detected, the number of times of the zero crossing point is counted, and whether the motor enters the closed loop stage is judged according to the detected number of times of the zero crossing point. The invention accelerates the motor rotation by adopting the staged duty ratio, can lead the motor speed to be converged rapidly, lead the counter electromotive force to be detected rapidly, and quicken the starting time of the motor. In one implementation, the motor is typically at least 2 phases, for example, may be 3 phases, during the acceleration start phase.
In some embodiments, step S300 includes the steps of:
s310, detecting the times of zero crossing points;
s320, judging the number of zero crossing points and the threshold value of the number of zero crossing points;
s330, when the rotation speed of the motor is detected to reach a speed convergence value and the number of times of detecting the zero crossing point reaches a zero crossing point number threshold, switching a driving signal of the motor into a high-level signal with fixed duration;
s340, the counter electromotive force of the motor is sampled to control the motor to rotate.
Specifically, in the motor acceleration stage, the singlechip counts the counter electromotive force and the times of zero crossing points in real time, when the rotating speed of the motor reaches a speed convergence value, judges whether the times of the detected zero crossing points reach a zero crossing point time threshold, and if the times of the detected zero crossing points reach the zero crossing point time threshold, converts a driving signal of the motor into a corresponding high-level signal with fixed duration from a pulse width modulation signal, drives the motor to rotate through the high-level signal with fixed duration, and samples the counter electromotive force to control the motor to rotate.
The high-level time length of the fixed time length is obtained through the debugging stage.
In some embodiments, the method for controlling rotation of a brushless dc motor further includes the steps of:
s101, presetting the zero crossing frequency threshold.
Specifically, before the singlechip is used for controlling the motor to start, the zero crossing frequency threshold value of the motor in the acceleration stage is set, and in one implementation manner, the zero crossing frequency threshold value is greater than or equal to 2, for example, may be 12 times.
S102, presetting a speed convergence value of the motor according to a target speed value.
Specifically, before the single chip microcomputer is controlled to start the motor, the speed convergence value of the motor in the acceleration stage is required to be set, the speed convergence value is set according to the target speed, and when the rotating speed of the motor reaches the speed convergence value and the zero crossing frequency reaches the zero crossing frequency threshold, the motor enters the closed loop stage, and a driving signal of the motor is converted into a high-level signal with fixed duration from a pulse width modulation signal.
In some implementations, step S200 further includes the steps of:
s240, judging whether the counter electromotive force can be detected, and if the counter electromotive force is not detected within the preset time, alarming and controlling the motor to stop rotating.
Specifically, in the acceleration stage of the motor, the singlechip detects the counter electromotive force in real time, if the counter electromotive force is not detected within a preset time (for example, 2 seconds), the abnormal operation of the motor is indicated, and the singlechip controls the motor to stop rotating and perform alarm processing.
In some embodiments, step S300 further comprises:
and S350, if the number of times of detecting the zero crossing point reaches the threshold value of the number of times of the zero crossing point, the driving signal of the motor is not switched to a high-level signal with fixed duration, and then the motor is alarmed and controlled to stop rotating.
Specifically, when the number of times of detecting the zero crossing point reaches the threshold value of the number of times of detecting the zero crossing point, after the rotation speed of the motor is converged, the motor driving signal is not converted into a high-level signal with fixed duration, the abnormal operation of the motor is indicated, the single chip microcomputer controls the motor to stop working, and alarm processing is carried out.
For a better understanding of the present invention, the following further describes the motor start-up procedure:
as shown in fig. 4, in the starting stage, the singlechip is powered on or reset, and then enters a pre-positioning stage, and the pre-positioning mode can be selected by itself in the actual use process, so long as the initial position of the motor rotor can be found. After the initial position of the motor rotor is found, the motor is controlled to enter an acceleration stage, specifically, the rotating speed of the motor is quickly increased by changing the duty ratio of a pulse width modulation signal so as to quickly detect counter electromotive force, at the moment, whether the counter electromotive force can be detected is judged, and if the counter electromotive force can not be detected still in a certain time, the motor is stopped to rotate and alarm. And detecting and counting zero crossing points, if the number of the detected zero crossing points reaches a zero crossing point number threshold, meeting the condition of entering a closed loop stage, otherwise stopping the motor rotation and carrying out alarm processing. After entering the closed loop stage, setting the driving signal as a high level signal with a corresponding fixed duration according to a given speed value to drive the motor to rotate, and ending the control flow when the motor stops rotating.
In some embodiments, the present invention further provides a single chip microcomputer, which includes a processor and a memory, the memory stores a computer program, and the processor processes the following steps when executing the computer program:
s100, pre-positioning the motor to determine the initial position of a motor rotor;
s200, outputting pulse width modulation signals to control the motor to accelerate in a stage mode so as to detect counter electromotive force and zero crossing points, and counting the times of the detected zero crossing points;
and S300, outputting a high-level signal with fixed duration to drive the motor to rotate after the number of detected zero crossing points reaches a zero crossing point number threshold, and sampling the counter electromotive force of the motor to control the motor to rotate.
Specifically, the starting process of the singlechip-controlled motor comprises an open-loop stage and a closed-loop stage, wherein the open-loop stage comprises a pre-positioning stage and an acceleration stage. In the pre-positioning stage, the AB and BC phases of the motor are electrified firstly to find the accurate position of the motor rotor, so that the initial position of the motor rotor is determined. In the acceleration stage, a driving signal of the motor adopts a pulse width modulation signal, the singlechip enables the motor to accelerate and rotate by changing the duty ratio of the pulse width modulation signal so as to rapidly detect counter electromotive force and zero crossing points, counts the times of the zero crossing points, enters a closed loop stage of the motor when the times of the zero crossing points reach a threshold value of the times of the zero crossing points, adjusts the driving signal of the motor into a high-level signal with fixed duration by the pulse width modulation signal, drives the motor to rotate by the high-level signal with fixed duration, the counter electromotive force detected by the singlechip is a continuous signal at the moment, and the waveform of the detected counter electromotive force is a continuous slope, so that the counter electromotive force detected by the singlechip is a continuous value, and the sampling result is more accurate.
Therefore, after the motor enters a closed loop stage, the motor is driven by a high-level signal with fixed duration, the counter electromotive force detected by the singlechip is a continuous signal, the waveform of the detected counter electromotive force is a continuous slope, and even if the motor is in a high-speed or even ultra-high-speed running state, the singlechip can accurately sample, so that the accuracy of the sampling result of the singlechip is ensured, the problem that the motor rotates to violent pulsation or even stops rotating due to sampling errors of the counter electromotive force of the singlechip is prevented, and the operation difficulty and complexity are not increased compared with the original control mode. In addition, in the closed loop stage, a high-level signal with fixed duration is adopted to drive the motor, the requirement on the MCU is low, and the cost is also reduced. In addition, the invention drives the motor by adopting the high level with fixed duration, namely, the fixed level is adopted to control the switching tube, and compared with the pulse width modulation signal driving switching tube, the frequency of a conducting medium of the switching tube can be greatly reduced, thereby prolonging the service life of the switching tube, being particularly suitable for high-speed motors and improving the competitiveness of the high-speed motors.
In summary, the method for controlling the rotation of the brushless direct current motor and the singlechip provided by the invention have the following beneficial effects:
after the motor enters a closed loop stage, the motor is driven by a high-level signal with fixed duration, the counter electromotive force detected by the singlechip is a continuous signal, the waveform of the detected counter electromotive force is a continuous slope, and even if the motor is in a high-speed or even super-speed running state, the singlechip can accurately sample, so that the accuracy of a sampling result of the singlechip is ensured, and the problem that the rotation of the motor is violently pulsed or even stopped due to sampling errors of the counter electromotive force of the motor sampled by the singlechip is prevented;
in the closed loop stage, a high-level signal with fixed duration is adopted to drive the motor, so that the requirement on the MCU is low, and the cost is reduced;
the switching tube is controlled by adopting a fixed level, and the frequency of a conducting medium of the switching tube is greatly reduced relative to that of driving the switching tube by a pulse width modulation signal, so that the service life of the switching tube can be prolonged, the switching tube is particularly suitable for a high-speed motor, and the competitiveness of the high-speed motor is improved;
compared with the original control mode, the control method does not increase the operation difficulty and complexity.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (9)
1. A method for controlling rotation of a brushless dc motor, comprising:
pre-positioning the motor to determine an initial position of a motor rotor;
outputting pulse width modulation signals to control the motor to accelerate in stages so as to detect counter electromotive force and zero crossing points, and counting the times of the detected zero crossing points;
when the number of detected zero crossing points reaches a zero crossing point number threshold, outputting a high-level signal with fixed duration to drive the motor to rotate, and sampling the counter electromotive force of the motor to control the motor to rotate;
after the number of zero crossing points detected reaches the threshold value of the number of zero crossing points, outputting a high level with a fixed duration to drive the motor to rotate, sampling the counter electromotive force of the motor, and controlling the motor to rotate, wherein the step of controlling the motor to rotate comprises the following steps:
detecting the times of zero crossing points;
judging the number of zero crossing points and the threshold value of the number of zero crossing points;
when the rotation speed of the motor is detected to reach a speed convergence value and the number of times of detecting the zero crossing point reaches a zero crossing point number threshold, switching a driving signal of the motor into a high-level signal with fixed duration; when the detected zero crossing frequency reaches a zero crossing frequency threshold value, entering a closed loop stage of the motor;
sampling the back electromotive force of the motor to control the motor to rotate; the sampled back electromotive force is a continuous signal, and the waveform of the back electromotive force is a continuous slope.
2. The method of claim 1, wherein the step of outputting the pulse width modulation signal to control the motor to accelerate to detect the counter electromotive force and the zero crossing point and counting the number of times of the detected zero crossing point comprises:
outputting a pulse width modulation signal according to a target speed value to control the motor to rotate at the 1 st stage speed so as to detect a first zero crossing point and count the times of the detected zero crossing point;
accelerating the motor to rotate at the 2 nd stage by adjusting the duty ratio of the pulse width modulation signal so as to detect a second zero crossing point and count the number of times of the detected zero crossing point;
the motor is rotated at an nth stage by adjusting the duty ratio of the pulse width modulation signal to detect an nth zero crossing point and count the number of times of the detected zero crossing point.
3. The method of claim 1, wherein the step of outputting the pulse width modulation signal to control the motor to accelerate stepwise to detect the back electromotive force and the zero crossing point and counting the number of times of the detected zero crossing point further comprises:
judging whether the counter electromotive force can be detected, and if the counter electromotive force is not detected within the preset time, alarming and controlling the motor to stop rotating.
4. The method of claim 1, wherein the step of outputting a high level signal of a fixed duration to drive the motor to rotate and sampling a back electromotive force of the motor to control the motor to rotate after the number of zero crossings detected reaches the zero crossing number threshold value further comprises:
if the number of times of detecting zero crossing points reaches the threshold value of the number of times of zero crossing points, the driving signal of the motor is not switched to a high-level signal with fixed duration, and then the motor is alarmed and controlled to stop rotating.
5. The method of controlling rotation of a brushless dc motor according to claim 1, further comprising the step of:
and presetting the threshold value of the zero crossing times.
6. The method according to claim 5, wherein the threshold number of zero crossing points is 2 or more.
7. The method of claim 1, further comprising:
and presetting a speed convergence value of the motor according to the target speed value.
8. The method according to claim 2, wherein the duty ratio of the pulse width modulation signal increases in a linear trend when the motor is started up at an acceleration.
9. A single chip microcomputer comprising a processor and a memory, characterized in that the memory stores a computer program, which processor, when executing the computer program, realizes the steps of the method according to any of claims 1-8.
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| CN108606724A (en) * | 2018-03-30 | 2018-10-02 | 江苏美的清洁电器股份有限公司 | The back-emf zero passage detection method, apparatus and control system of dust catcher, motor |
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| CN110190784A (en) * | 2019-07-04 | 2019-08-30 | 北京航远动力科技有限责任公司 | A kind of brushless DC motor without sensor varying load progress control method |
| CN110635726A (en) * | 2019-10-18 | 2019-12-31 | 中国电子科技集团公司第四十三研究所 | Speed detection method and detection circuit for non-inductive brushless motor |
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