CN108847794B

CN108847794B - Dust collector, rotor position detection method and device of motor and control system

Info

Publication number: CN108847794B
Application number: CN201810296984.0A
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: 2018-03-30
Filing date: 2018-03-30
Publication date: 2020-04-28
Anticipated expiration: 2038-03-30
Also published as: CN108847794A

Abstract

The invention discloses a dust collector, a rotor position detection method and device of a brushless direct current motor and a control system, wherein the rotor position detection method comprises the following steps: in the process of controlling the motor by adopting a counter potential zero crossing method, when the rotor position of the motor is obtained by adopting the counter potential zero crossing method, the rotor position of the motor is also obtained by adopting a flux linkage method; judging whether counter potential zero-crossing detection is successful or not; if the detection is successful, phase change control is carried out on the motor according to the position of the rotor of the motor obtained by the counter electromotive force zero-crossing method, and the motor is continuously controlled by adopting the counter electromotive force zero-crossing method; and if the detection fails, performing phase change control on the motor according to the rotor position of the motor acquired by the flux linkage method, and starting to control the motor by adopting the flux linkage method. Therefore, when the rotating speed of the motor is suddenly reduced, the normal operation of the motor can still be ensured, and the operation reliability of the motor is greatly improved.

Description

Dust collector, rotor position detection method and device of motor and control system

Technical Field

The invention relates to the technical field of motor control, in particular to a rotor position detection method of a brushless direct current motor, a rotor position 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 emf zero crossing method is to obtain the rotor position of the motor by detecting the suspended back emf zero crossing points. When the counter potential of a certain phase winding of the brushless direct current motor passes through zero, the straight shaft of the rotor is just overlapped with the axis of the phase winding, so that the position information of the rotor can be obtained as long as the counter potential zero-crossing point of each phase winding is detected, and then the on-off of a switch tube is controlled by delaying 30 degrees of electric angle backwards based on the counter potential zero-crossing point so as to change the phase of the motor, thereby realizing the control of the motor without a position sensor.

However, when the motor is controlled by adopting the counter potential zero crossing method, if the load is suddenly increased, the corresponding motor rotating speed becomes very low, and when the rotating speed is low, the counter potential of the motor is very small, so that the accurate position of the rotor cannot be obtained by the counter potential zero crossing method, and the normal operation of the motor cannot be ensured.

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 method for detecting a rotor position of a brushless dc motor, which can ensure normal operation of the motor even when the rotation speed of the motor is suddenly reduced, thereby greatly improving the reliability of the operation of the motor.

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 rotor position detecting device 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 first embodiment of the present invention provides a rotor position detecting method for a brushless dc motor, including the following steps: in the process of controlling the motor by adopting a counter electromotive force zero-crossing method, when the rotor position of the motor is obtained by adopting the counter electromotive force zero-crossing method, the rotor position of the motor is also obtained by adopting a flux linkage method; judging whether counter potential zero-crossing detection is successful or not; if the back electromotive force zero-crossing detection is successful, performing phase commutation control on the motor according to the rotor position of the motor acquired by the back electromotive force zero-crossing method, and continuously controlling the motor by adopting the back electromotive force zero-crossing method; and if the back electromotive force zero-crossing detection fails, performing phase commutation control on the motor according to the rotor position of the motor acquired by the flux linkage method, and starting to control the motor by adopting the flux linkage method.

According to the rotor position detection method of the brushless direct current motor, in the process of controlling the motor by adopting the back electromotive force zero-crossing method, when the rotor position of the motor is obtained by adopting the back electromotive force zero-crossing method, the rotor position of the motor is also obtained by adopting a flux linkage method, and whether back electromotive force zero-crossing detection is successful or not is judged. If the back electromotive force zero-crossing detection is successful, phase change control is carried out on the motor according to the position of the rotor of the motor acquired by the back electromotive force zero-crossing method, and the motor is continuously controlled by adopting the back electromotive force zero-crossing method; and if the back electromotive force zero-crossing detection fails, performing phase change control on the motor according to the rotor position of the motor acquired by the flux linkage method, and starting to control the motor by adopting the flux linkage method. Therefore, when the rotating speed of the motor is suddenly reduced, even if the counter potential is very small, the rotor position of the motor cannot be detected by adopting a counter potential zero-crossing method, the phase change control can be performed on the motor through the rotor position of the motor obtained by a flux linkage method, the motor can be ensured to continuously and normally operate, and the operation reliability of the motor is greatly improved.

In addition, the rotor position detection method 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 invention, in the process of controlling the motor by using the flux linkage method, the back electromotive force zero-crossing method is further used for acquiring the rotor position of the motor, and judging whether the number of times of back electromotive force zero-crossing detection success is greater than or equal to a preset number of times or whether the back electromotive force climbing slope of the motor is greater than or equal to a preset slope; if the counter electromotive force zero-crossing detection is successful for a time less than the preset time or the counter electromotive force climbing slope is less than the preset slope, continuing to control the motor by adopting the flux linkage method; and if the counter electromotive force zero-crossing detection is successful for more than or equal to the preset times or the counter electromotive force climbing slope is more than or equal to the preset slope, starting to control the motor by adopting the counter electromotive force zero-crossing method.

According to an embodiment of the present invention, the controlling the motor by using the flux linkage method includes: obtaining a temperature-phase resistance meter, a temperature-phase inductance meter and a bus voltage-phase current change rate table of the motor in an off-line manner; within the high level time of each PWM control period, acquiring conducting phase positive end voltage, conducting phase negative end voltage, non-conducting opposite potential voltage, bus current instantaneous value, bus voltage and current winding temperature; acquiring the phase current change rate of the motor according to the bus voltage and the bus voltage-phase current change rate table, and acquiring the phase resistance and the phase inductance of the motor according to the current winding temperature, the temperature-phase resistance table and the temperature-phase inductance table; and carrying out phase change control on the motor according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance.

According to another embodiment of the present invention, the controlling the motor by the flux linkage method includes: obtaining a temperature-phase resistance meter and a temperature-phase inductance meter of the motor in an off-line manner; in the high level time of each PWM control period, acquiring conducting phase positive end voltage, conducting phase negative end voltage, non-conducting opposite potential voltage, bus current instantaneous value and current winding temperature, and acquiring phase currents of the motor corresponding to any two moments; obtaining the phase current change rate of the motor according to the phase currents of the motor corresponding to the any two moments and the any two moments, and obtaining the phase resistance and the phase inductance of the motor according to the current winding temperature, the temperature-phase resistance meter and the temperature-phase inductance meter; and carrying out phase change control on the motor according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance.

According to an embodiment of the present invention, the phase-change controlling of the motor according to the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance, and the phase inductance includes: acquiring a flux linkage value of the motor or a slope of a flux linkage function G (theta) according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance; and if the flux linkage value of the motor is larger than a preset flux linkage threshold value or the gradient of the flux linkage function G (theta) is larger than a preset gradient threshold value, controlling the motor to carry out phase commutation.

According to an embodiment of the present invention, before obtaining the flux linkage value of the motor or the slope of the flux linkage function G (θ), the method further includes: judging whether a voltage difference value between the non-conduction opposite potential voltage in the current PWM control period and the non-conduction opposite potential voltage in the previous PWM control period is within a preset range or not; and if the voltage difference value is within the preset range, acquiring the flux linkage value of the motor or the slope of a flux linkage function G (theta).

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, and the computer program, when executed by a processor, implements the above-mentioned method for detecting a rotor position of a brushless dc motor.

According to the non-transitory computer readable storage medium of the embodiment of the invention, by executing the rotor position detection method of the brushless direct current motor, when the rotating speed of the motor is suddenly reduced, even if the counter electromotive force is very small, so that the rotor position of the motor cannot be detected by adopting a counter electromotive force zero crossing method, the phase change control can be performed on the motor through the rotor position of the motor obtained by a flux linkage method, the motor can be ensured to continuously and normally operate, and the reliability of the operation of the motor is greatly improved.

In order to achieve the above object, a rotor position 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 the rotor position of the motor by adopting a counter electromotive force zero crossing method; the second acquisition unit is used for acquiring the rotor position of the motor by adopting a flux linkage method; the control unit is used for acquiring the rotor position of the motor through the second acquisition unit and judging whether counter potential zero-crossing detection is successful or not when the rotor position of the motor is acquired through the first acquisition unit in the process of controlling the motor by adopting the counter potential zero-crossing method, wherein if the counter potential zero-crossing detection is successful, the control unit performs phase change control on the motor according to the rotor position of the motor acquired by the first acquisition unit and continues to control the motor by adopting the counter potential zero-crossing method; and if the back electromotive force zero-crossing detection fails, the control unit performs phase change control on the motor according to the rotor position of the motor acquired by the second acquisition unit and starts to control the motor by adopting the flux linkage method.

According to the rotor position detection device of the brushless direct current motor, in the process that the control unit controls the motor by adopting the counter electromotive force zero crossing method, when the first acquisition unit acquires the rotor position of the motor, the second acquisition unit also acquires the rotor position of the motor and judges whether counter electromotive force zero crossing detection is successful, wherein if the counter electromotive force zero crossing detection is successful, the control unit controls the motor in a phase change mode according to the rotor position of the motor acquired by the first acquisition unit and continues to control the motor by adopting the counter electromotive force zero crossing method; and if the back electromotive force zero-crossing detection fails, the control unit performs phase change control on the motor according to the rotor position of the motor acquired by the second acquisition unit and starts to control the motor by adopting a flux linkage method. Therefore, when the rotating speed of the motor is suddenly reduced, even if the counter potential is very small, the rotor position of the motor cannot be detected by adopting a counter potential zero-crossing method, the phase change control can be performed on the motor through the rotor position of the motor obtained by a flux linkage method, the motor can be ensured to continuously and normally operate, and the operation reliability of the motor is greatly improved.

In addition, the rotor position detecting device 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, in the process of controlling the motor by using the flux linkage method, the control unit further obtains a rotor position of the motor through the first obtaining unit, and determines whether the number of times of success of back electromotive force zero-crossing detection is greater than or equal to a preset number of times or whether a back electromotive force climbing slope of the motor is greater than or equal to a preset slope, wherein if the number of times of success of back electromotive force zero-crossing detection is less than the preset number of times or the back electromotive force climbing slope is less than the preset slope, the control unit continues to control the motor by using the flux linkage method; and if the counter electromotive force zero-crossing detection is successful for more than or equal to the preset times or the counter electromotive force climbing slope is more than or equal to the preset slope, the control unit starts to control the motor by adopting the counter electromotive force zero-crossing method.

According to an embodiment of the present invention, when the control unit controls the motor by using the flux linkage method, the control unit obtains a temperature-phase resistance table, a temperature-phase inductance table, and a bus voltage-phase current change rate table of the motor offline, and obtains a conducting phase positive terminal voltage, a conducting phase negative terminal voltage, a non-conducting opposite potential voltage, a bus current instantaneous value, a bus voltage, and a current winding temperature during a high level time of each PWM control cycle, and obtains a phase current change rate of the motor according to the bus voltage and the bus voltage-phase current change rate table, and obtains a phase resistance and a phase inductance of the motor according to the current winding temperature and the temperature-phase resistance table, the temperature-phase inductance table, and a phase resistance and a phase inductance of the motor according to the conducting phase positive terminal voltage, the temperature-phase current change rate table, and a phase current change rate table of the motor according to, And the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance are used for carrying out phase change control on the motor.

According to another embodiment of the present invention, when the control unit controls the motor by using the flux linkage method, the control unit obtains a temperature-phase resistance table and a temperature-phase inductance table of the motor offline, and obtains, during a high level time of each PWM control period, a conducting phase positive terminal voltage, a conducting phase negative terminal voltage, a non-conducting opposite potential voltage, a bus current instantaneous value and a current winding temperature, and obtains phase currents of the motor corresponding to any two times, and obtains a phase current change rate of the motor according to the phase currents of the motor corresponding to the any two times and the any two times, and obtains a phase resistance and a phase inductance of the motor according to the current winding temperature and the temperature-phase resistance table, the temperature-phase inductance table, and the conducting phase positive terminal voltage, And the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance are used for carrying out phase change control on the motor.

According to an embodiment of the present invention, when the control unit performs commutation control on the motor according to the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance, and the phase inductance, the control unit obtains a flux linkage value of the motor or a slope of a flux linkage function G (θ) according to the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance, and the phase inductance, wherein if the flux linkage value of the motor is greater than a preset flux linkage threshold value or the slope of the flux linkage function G (θ) is greater than a preset slope threshold value, the control unit controls the motor to perform commutation.

According to an embodiment of the present invention, before obtaining the flux linkage value of the motor or the slope of the flux linkage function G (θ), the control unit is further configured to determine whether a voltage difference value between the non-conductive opposite potential voltage in the current PWM control period and the non-conductive opposite potential voltage in the previous PWM control period is within a preset range, and if the voltage difference value is within the preset range, obtain the flux linkage value of the motor or the slope of the flux linkage function G (θ).

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 above rotor position detecting device for a brushless dc motor.

According to the control system of the brushless direct current motor, provided by the embodiment of the invention, through the rotor position detection device of the brushless direct current motor, when the rotating speed of the motor is suddenly reduced, even if the counter electromotive force is very small, so that the rotor position of the motor cannot be detected by adopting a counter electromotive force zero crossing method, the phase change control can be carried out on the motor through the rotor position of the motor obtained by a flux linkage method, the normal operation of the motor can be ensured, and the operation reliability of the motor is greatly improved.

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, when the rotating speed of the motor is suddenly reduced, even if the counter potential is very small, so that the rotor position of the motor cannot be detected by adopting a counter potential zero crossing method, the phase change control can be carried out on the motor through the rotor position of the motor obtained by a flux linkage method, the motor can be ensured to continuously and normally run, the running reliability of the motor is greatly improved, and the running reliability of the dust collector is further improved.

Drawings

Fig. 1 is a flowchart of a rotor position detection method of a brushless dc motor according to an embodiment of the present invention;

FIG. 2 is a flow chart of a method for controlling a motor using back emf zero crossings, according to an embodiment of the present invention;

FIG. 3a is a waveform illustrating a back emf during a motor start-up low speed operation in accordance with one embodiment of the present invention;

FIG. 3b is a schematic diagram of a waveform of a back emf during operation of the motor at medium to high speed in accordance with one embodiment of the present invention;

FIG. 4 is a waveform diagram of phase currents for a brushless DC motor according to one embodiment of the present invention;

FIG. 5 is a graph of phase current rate of change versus bus voltage for a brushless DC motor in accordance with one embodiment of the present invention;

FIG. 6 is a graph of phase current change rate versus bus voltage for a brushless DC motor according to another embodiment of the present invention;

FIG. 7 is a waveform diagram of phase currents for a brushless DC motor according to another embodiment of the present invention;

fig. 8 is a waveform diagram of line back emf of a brushless dc motor according to one embodiment of the present invention;

FIG. 9 is a waveform diagram of a flux linkage function G (θ) according to one embodiment of the invention;

FIG. 10 is a waveform diagram of a flux linkage function G (θ) according to another embodiment of the present invention;

FIG. 11 is a flow chart of a method of controlling a motor using flux linkage according to one embodiment of the present invention;

fig. 12 is a block schematic diagram of a rotor position detecting 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 rotor position detection method of a brushless dc motor, a non-transitory computer-readable storage medium, a rotor position 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 rotor position detection method of a brushless dc motor according to an embodiment of the present invention. As shown in fig. 1, a rotor position detection method of a brushless dc motor according to an embodiment of the present invention includes the steps of:

and S1, in the process of controlling the motor by adopting the counter electromotive force zero-crossing method, when the rotor position of the motor is obtained by adopting the counter electromotive force zero-crossing method, the rotor position of the motor is also obtained by adopting a flux linkage method.

The method for acquiring the rotor position of the motor by adopting the back electromotive force zero-crossing method and the method for acquiring the rotor position of the motor by adopting the flux linkage method can be realized by the prior art.

And S2, judging whether the counter potential zero-crossing detection is successful.

And S3, if the counter electromotive force zero-crossing detection is successful, performing phase change control on the motor according to the rotor position of the motor acquired by the counter electromotive force zero-crossing method, and continuously controlling the motor by adopting the counter electromotive force zero-crossing method.

And S4, if the back electromotive force zero-crossing detection fails, performing phase change control on the motor according to the rotor position of the motor acquired by the flux linkage method, and starting to control the motor by the flux linkage method.

Specifically, when the motor operates at medium-high speed, a back electromotive force zero-crossing method is generally adopted to acquire the rotor position of the motor, and the motor is subjected to phase commutation control according to the acquired rotor position, so that the motor continuously operates. However, when the rotor position of the motor is obtained according to the back electromotive force zero crossing method, it is necessary to ensure that the back electromotive force of the motor is sufficiently large, and once the back electromotive force is too small, the accurate rotor position of the motor cannot be obtained.

Therefore, in the embodiment of the invention, when the rotor position of the motor is obtained by the back electromotive force zero-crossing method, the rotor position of the motor is also obtained by the flux linkage method (only the rotor position is obtained, and no phase change is performed), so that when the back electromotive force zero-crossing detection fails, the motor is phase-changed according to the rotor position of the motor obtained by the flux linkage method, that is, the motor can be ensured to continue to operate, and the motor is controlled by switching to the flux linkage method, so that the correct phase change of the motor is ensured, and the motor can be ensured to operate reliably.

Further, in an embodiment of the present invention, as shown in fig. 2, when the motor operates at a medium-high speed, the method for detecting the rotor position of the brushless dc motor according to the embodiment of the present invention may include the following steps:

and S201, entering a current counter potential zero-crossing detection process.

S202, judging whether a counter potential zero crossing point is detected. If yes, go to step S203; if not, step S204 is performed.

And S203, setting phase-changing delay time, and performing phase-changing control on the motor according to the rotor position of the motor acquired by a counter potential zero-crossing method.

And S204, acquiring the rotor position of the motor by adopting a flux linkage method.

And S205, judging whether the counter electromotive force zero-crossing detection is overtime. If yes, go to step S206; and if not, exiting the current counter potential zero-crossing detection process.

And S206, performing phase change control on the motor according to the rotor position of the motor acquired by the flux linkage method.

And S207, switching to a flux linkage method to control the motor.

Therefore, in the process of controlling the motor by adopting the counter electromotive force zero crossing method, the rotor position of the motor is obtained by the flux linkage method, so that the motor is subjected to phase commutation according to the rotor position of the motor obtained by the flux linkage method when the counter electromotive force of the motor is small, and the motor can continue to normally operate. For example, in practical application, when the rotor position detection method is used for controlling a brushless dc motor in a dust collector, when a load is suddenly increased (for example, a large object is blocked or sucked), the rotating speed of the corresponding motor becomes very low, when the rotating speed of the motor is low, the back electromotive force of the motor is very small, which results in failure of back electromotive force zero-crossing detection, and at this time, the motor can be phase-switched according to the rotor position of the motor obtained by a flux linkage method, so that the motor can be ensured to be correctly phase-switched, the motor can continue to normally operate, the occurrence of abnormal operation of the dust collector caused by sudden increase of the load is effectively avoided, and the operation stability of the dust collector is effectively improved. Further, in some embodiments of the present invention, in the process of controlling the motor by using the flux linkage method, a back electromotive force zero-crossing method is further used to obtain the rotor position of the motor, and it is determined whether the number of times of back electromotive force zero-crossing detection success is greater than or equal to a preset number of times; if the times of success of counter potential zero-crossing detection are less than the preset times, continuing to control the motor by adopting a flux linkage method; and if the times of success of counter potential zero-crossing detection are more than or equal to the preset times, starting to adopt a counter potential zero-crossing method to control the motor. The preset times can be calibrated according to actual conditions.

Specifically, in the process of starting and running at a low speed of the motor, the rotor position of the motor can be acquired by adopting a flux linkage method, the phase change control can be performed on the motor according to the acquired rotor position so as to accelerate the running of the motor, meanwhile, counter potential zero-crossing detection (only counter potential zero-crossing points are detected and the phase change is not performed) can be performed on the motor, and when the number of times of successful counter potential zero-crossing detection meets a certain condition, the counter potential zero-crossing method can be switched to for controlling the motor. That is to say, in the process of starting the motor, because the rotating speed ratio of the motor is low, the back electromotive force method cannot obtain the accurate rotor position of the motor, so the motor is controlled by adopting the flux linkage method, the back electromotive force zero-crossing detection is carried out on the motor at the same time, when the rotating speed of the motor is increased to a certain value, the back electromotive force zero-crossing point is continuously detected, and the back electromotive force zero-crossing method is switched to control the motor at the moment. In other embodiments of the present invention, in the process of controlling the motor by using the flux linkage method, a back electromotive force zero-crossing method is further used to obtain the rotor position of the motor, obtain the back electromotive force climbing slope of the motor, and determine whether the back electromotive force climbing slope is greater than or equal to a preset slope; if the back electromotive force climbing slope is smaller than the preset slope, the motor is continuously controlled by adopting a flux linkage method; and if the counter potential climbing slope is larger than or equal to the preset slope, starting to control the motor by adopting a counter potential zero crossing method. The back electromotive force climbing slope refers to a slope corresponding to a steady rising stage or a steady falling stage of a waveform of the back electromotive force of the motor.

Specifically, fig. 3a is a schematic waveform diagram of a counter electromotive force during the motor starting low-speed operation, and fig. 3b is a schematic waveform diagram of a counter electromotive force during the motor operating at a medium-high speed, as shown in fig. 3a and fig. 3b, during the motor starting low-speed operation, the counter electromotive force has a gentle climbing slope, the counter electromotive force has a low climbing slope, and the counter electromotive force climbing slope gradually increases with the increase of the rotation speed, so that whether to switch from the flux linkage method to the counter electromotive force zero-crossing method for controlling the motor can be judged by detecting the counter electromotive force climbing slope.

For example, during the starting of the motor in low-speed operation, the flux linkage method can be used for acquiring the rotor position of the motor, performing phase change control on the motor according to the acquired rotor position so as to accelerate the operation of the motor, and simultaneously performing counter potential zero-crossing detection on the motor and acquiring the counter potential climbing slope of the motor. If the back electromotive force climbing slope of the motor is smaller than a preset slope, and the preset slope is a slope corresponding to the rotor position of the motor, which can be obtained accurately through a back electromotive force zero-crossing method, the back electromotive force zero-crossing method cannot be switched to currently to control the motor, and at the moment, the flux linkage method is continuously adopted to control the motor; if the back electromotive force climbing slope of the motor is larger than or equal to the preset slope, the back electromotive force zero-crossing method is used for obtaining the accurate rotor position of the motor, and the motor is controlled by switching to the back electromotive force zero-crossing method.

Therefore, in the embodiment of the invention, in the process of controlling the motor by adopting the flux linkage method, whether the motor is controlled by switching from the flux linkage method to the counter potential zero-crossing method can be judged according to the times of successful counter potential zero-crossing detection, and whether the motor is controlled by switching from the flux linkage method to the counter potential zero-crossing method can be judged according to the detected counter potential climbing slope of the motor.

According to one embodiment of the invention, the motor is controlled by adopting a flux linkage method, and the method comprises the following steps: obtaining a temperature-phase resistance meter, a temperature-phase inductance meter and a bus voltage-phase current change rate table of the motor in an off-line manner; within the high level time of each PWM control period, acquiring conducting phase positive end voltage, conducting phase negative end voltage, non-conducting opposite potential voltage, bus current instantaneous value, bus voltage and current winding temperature; acquiring phase current change rate of the motor according to the bus voltage and the bus voltage-phase current change rate table, and acquiring phase resistance and phase inductance of the motor according to the current winding temperature, a temperature-phase resistance table and a temperature-phase inductance table; and performing phase change control on the motor according to the voltage of the positive end of the conducting phase, the voltage of the negative end of the conducting phase, the voltage of the non-conducting opposite potential, the instantaneous value of the bus current, the phase current change rate, the phase resistance and the phase inductance.

According to another embodiment of the present invention, a flux linkage method is used for controlling a motor, including: obtaining a temperature-phase resistance meter and a temperature-phase inductance meter of the motor in an off-line manner; in the high level time of each PWM control period, acquiring conducting phase positive end voltage, conducting phase negative end voltage, non-conducting opposite potential voltage, bus current instantaneous value and current winding temperature, and acquiring phase currents of the motor corresponding to any two moments; obtaining the phase current change rate of the motor according to any two moments and the phase currents of the motor corresponding to any two moments, and obtaining the phase resistance and the phase inductance of the motor according to the current winding temperature, a temperature-phase resistance meter and a temperature-phase inductance meter; and performing phase change control on the motor according to the voltage of the positive end of the conducting phase, the voltage of the negative end of the conducting phase, the voltage of the non-conducting opposite potential, the instantaneous value of the bus current, the phase current change rate, the phase resistance and the phase inductance.

Specifically, assuming that three-phase windings of the brushless dc motor are connected in a star shape, a permanent magnet rotor of the square-wave driven brushless dc motor is usually in a surface-mount structure, and has no damping winding, neglects hysteresis loss and eddy current loss, neglects the influence of magnetic circuit saturation, and neglects the influence of rotor position change on inductance, taking phase a as an example, a phase voltage equation of the brushless dc motor may be expressed as:

wherein, U_anPhase voltage, R, for A-phase winding of brushless DC motor_sIs the phase resistance of a brushless DC motor, i_aThe phase current of A phase winding of the brushless DC motor, L is equivalent inductance of each phase winding, theta is rotor position angle of the brushless DC motor, lambda_arAnd (theta) is a rotor permanent magnet flux linkage of the A-phase winding turn chain.

Since the last term in equation (1) is the back emf of the brushless dc motor, equation (1) can be redefined as:

wherein k is_eIs the back emf coefficient of the brushless DC motor, f_ar(theta) is a flux linkage related function that varies periodically with rotor position angle theta.

Because the brushless direct current motor does not generally lead out a neutral point during design, in order to facilitate calculation, a line voltage equation expression can be obtained by the formula (2):

wherein, U_abLine voltage for brushless DC motors, i_bPhase current of B-phase winding of brushless DC motor, omega instantaneous angular velocity of brushless DC motor, f_abrAnd (theta) is a line-to-line flux linkage function which changes with the change of the rotor position angle of the brushless direct current motor.

Further, the rotor position angle θ is included in the formula (3)

Redefined as a new flux linkage function H (theta) between lines_abThat is to say that,

combining equation (3) yields:

wherein, U_a、U_bIs the brushless dc motor terminal voltage.

Due to H_ab(θ) is a function related to the rotor position angle, and therefore, the rotor position of the motor can be theoretically estimated by the function. However, as can be seen from equation (4), in calculating H_abIn (θ), in addition to the motor parameters such as the terminal voltage of the brushless dc motor, the instantaneous angular velocity ω of the rotor of the brushless dc motor, that is, the rotation speed of the brushless dc motor, needs to be obtained. To solve the above problem, the flux linkage function between the two wire lines of the three-phase winding may be divided to obtain a new flux linkage function G (θ), that is,

from equations (4) and (5) we can obtain:

wherein, U_a、U_b、U_cFor brushless DC motor terminal voltage, i_aPhase current of A-phase winding of brushless DC motor i_bPhase current of B-phase winding of brushless DC motor i_cThe phase current of the C-phase winding of the brushless direct current motor.

It can be understood that the flux linkage function G (θ) has a one-to-one correspondence relationship with the rotor position of the brushless dc motor, and is not related to the rotation speed of the brushless dc motor, and theoretically, the rotor position information can be obtained in the full speed range of the brushless dc motor, so that the rotor position information can be obtained in the low speed operation stage of the brushless dc motor according to the flux linkage function G (θ), and the brushless dc motor is controlled to perform accurate phase change.

That is, in the process of starting the low-speed operation of the brushless dc motor, the flux linkage commutation method can be used to obtain the rotor position of the brushless dc motor and perform accurate commutation control. However, when the rotor position is obtained by the flux linkage commutation method and commutation is performed, the flux linkage value of the brushless dc motor needs to be obtained in real time and judged accordingly, so that accurate commutation can be performed. According to the formula (6), to obtain the flux linkage value of the brushless dc motor, the terminal voltage of the brushless dc motor (including the positive terminal voltage of the conducting phase, the negative terminal voltage of the conducting phase, and the opposite potential voltage of the non-conducting phase), the phase current of each phase winding of the brushless dc motor, the phase resistance of each phase winding of the brushless dc motor, the phase inductance of each phase winding of the brushless dc motor, and the phase current change rate of each phase winding of the brushless dc motor need to be obtained.

Furthermore, phase resistance and phase inductance of each phase winding of the brushless direct current motor have a certain relation with the temperature of the corresponding winding, and phase current change rate of each phase winding of the brushless direct current motor has a certain relation with bus voltage. In order to simplify the code operation, the relationship between the phase resistance and the phase inductance of each phase winding of the brushless dc motor and the temperature of the corresponding winding and the relationship between the phase current change rate of each phase winding of the brushless dc motor and the corresponding bus voltage can be recorded in the form of an off-line table through a large number of tests in advance, that is, a temperature-phase resistance table, a temperature-phase inductance table and a bus voltage-phase current change rate table of the brushless dc motor can be counted through a large number of tests in advance.

Specifically, the temperature-phase resistance table and the temperature-phase inductance table of the brushless dc motor may be obtained by measuring the phase resistance and the phase inductance of each phase winding of the brushless dc motor at a plurality of discrete temperature points (for example, the temperature interval may be 5 ℃) offline, or may be obtained by simulation software.

Further, the brushless dc motor may be provided with a current vector capable of turning on the brushless dc motor clockwise/counterclockwise at several different bus voltages (e.g., the voltage interval may be 2V), respectively, and a waveform of observing the phase current of the brushless dc motor may be recorded, wherein the waveform of the phase current of the brushless dc motor may be as shown in fig. 4. From the time interval Δ t and the phase current change amount Δ i of the brushless dc motor shown in fig. 4, the phase current change rate di/dt of the brushless dc motor at the current bus voltage can be calculated. As shown in fig. 5, each bus voltage u_n(N is 1,2, …, N, and N is an integer of 1 or more) corresponding to a phase current change rate (di/dt) of a brushless dc motor_n(N is 1,2, …, N, and N is an integer of 1 or more), whereby a bus voltage-phase current change rate table can be obtained.

Specifically, during the conduction period of the power switch tube, the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage and the bus voltage can be sequentially collected through the resistance voltage dividing circuit, the bus current instantaneous value (equal to the phase current instantaneous value of the brushless direct current motor) can be collected through the sampling resistor, and the current winding temperature of the brushless direct current motor can be obtained in real time through the temperature sensor.

According to one embodiment of the invention, a linear interpolation algorithm is used to obtain the phase current change rate of the brushless DC motor, the phase resistance and the phase inductance of the brushless DC motor.

Specifically, when the acquired bus voltage of the brushless dc motor falls between certain two voltage values in the bus voltage-phase current change rate table, a line may be employedAnd calculating the phase current change rate of the brushless direct current motor corresponding to the current bus voltage by using a linear interpolation algorithm. For example, as shown in fig. 5, when the bus voltage u of the brushless dc motor is obtained_xBus voltage u in bus voltage-phase current change rate table₁And bus voltage u₂In time between, due to bus voltage u₁The corresponding brushless DC motor has a phase current change rate of (di/dt)₁Bus voltage u₂The corresponding brushless DC motor has a phase current change rate of (di/dt)₂Therefore, using a linear interpolation algorithm, the following relationship can be obtained:

then, the current bus voltage u can be obtained according to the formula (7)_xPhase current change rate of corresponding brushless DC motor

Similarly, when the obtained current winding temperature is between two temperatures in the temperature-phase resistance table, the phase resistance of the brushless dc motor corresponding to the current winding temperature may be calculated by using a linear interpolation algorithm, and when the obtained current winding temperature is between two temperatures in the temperature-phase inductance table, the phase inductance of the brushless dc motor corresponding to the current winding temperature may also be calculated by using a linear interpolation algorithm, which is specifically referred to the obtaining of the phase current change rate, and will not be described in detail herein.

According to another embodiment of the present invention, in some applications with low requirements, in addition to obtaining the phase current change rate of the brushless dc motor by using the linear interpolation algorithm in the above embodiment, linear fitting of data may be performed on a plurality of discrete points obtained offline in fig. 3, so as to obtain the phase current change rate di/dt and the bus voltage u of the brushless dc motor_nThe relationship between them, as shown in fig. 6 and equation (8):

di/dt＝k*u_n+b (8)

where k and b are both constants.

In this way, in the process of controlling the brushless dc motor, the detected current bus voltage may be substituted into the formula (8) to obtain the phase current change rate of the brushless dc motor corresponding to the current bus voltage. In addition, for the acquisition of the phase resistance and the phase inductance, in some occasions with low requirements, a linear fitting mode can be adopted, and specifically, the acquisition of the phase current change rate can be referred to, and details are not repeated here.

According to another embodiment of the present invention, when the bus voltage-phase current change rate table is not obtained, the phase current change rate di/dt of the brushless dc motor can be obtained through an online calculation. Specifically, as shown in fig. 7, in the process of controlling the brushless dc motor, during the period when the power switching device is turned on, the phase current of the brushless dc motor is approximately considered to rise linearly, the phase current is sampled at two times during the period when the phase current of the brushless dc motor rises, and the sampling times t1 and t2, and the corresponding phase currents i1 and i2, i.e., sampling points C1(t1, i1), and sampling points C2(t2, i2) are recorded, and the phase current change rate di/dt of the brushless dc motor can be calculated online according to the two sampling points C1 and C2, that is,

di/dt＝(i2-i1)/(t2-t1)。

it should be noted that the two sampling points C1 and C2 in fig. 7 are respectively selected at the rising edge and the falling edge of the PWM control signal, however, when the points are actually taken, any time between the two points can be selected.

Therefore, in the process of controlling the brushless direct current motor, the bus voltage and the current winding temperature of the brushless direct current motor can be obtained in real time, and parameters such as the phase current change rate, the phase resistance, the phase inductance and the like of the brushless direct current motor can be effectively obtained by combining a corresponding algorithm according to a bus voltage-phase current change rate table, a temperature-phase resistance table and a temperature-phase inductance table; or, the current winding temperature of the brushless direct current motor is obtained in real time, parameters such as phase resistance, phase inductance and the like of the brushless direct current motor are effectively obtained by combining a corresponding algorithm according to the temperature-phase resistance table and the temperature-phase inductance table, and meanwhile, the phase current change rate of the brushless direct current motor corresponding to the current bus voltage is obtained in an online calculation mode. And then, carrying out phase change control on the motor according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance.

According to an embodiment of the present invention, a method for controlling phase change of a motor according to a conducting phase positive terminal voltage, a conducting phase negative terminal voltage, a non-conducting opposite potential voltage, a bus current instantaneous value, a phase current change rate, a phase resistance and a phase inductance includes: acquiring a flux linkage value or the slope of a flux linkage function G (theta) of the motor according to the positive end voltage of the conducting phase, the negative end voltage of the conducting phase, the non-conducting opposite potential voltage, the instantaneous value of the bus current, the phase current change rate, the phase resistance and the phase inductance; and if the flux linkage value of the motor is larger than a preset flux linkage threshold value or the gradient of the flux linkage function G (theta) is larger than a preset gradient threshold value, controlling the motor to carry out phase commutation.

Specifically, the positive end voltage of the conducting phase, the negative end voltage of the conducting phase, the non-conducting opposite potential voltage, the instantaneous value of the bus current (equal to the instantaneous value of the phase current), the rate of change of the phase current, the phase resistance and the phase inductance obtained in the above embodiment are substituted into the formula (6), so as to calculate the flux linkage value of the brushless dc motor, and obtain the waveform of the flux linkage function G (θ) to obtain the slope of the flux linkage function G (θ), and compare the flux linkage value of the brushless dc motor with the commutation threshold, or compare the slope of the flux linkage function G (θ) with the preset slope threshold, so as to determine whether to control the dc motor to perform commutation.

Before acquiring the flux linkage value of the brushless dc motor, the method further includes: judging whether a voltage difference value between the non-conduction opposite potential voltage in the current PWM control period and the non-conduction opposite potential voltage in the previous PWM control period is within a preset range; and if the voltage difference value is within the preset range, acquiring the flux linkage value of the brushless direct current motor.

That is, before the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance are substituted into the formula (6) to calculate the flux linkage value of the brushless dc motor, it may be determined whether a voltage difference value between the non-conducting opposite potential voltage in the current PWM control period and the non-conducting opposite potential voltage in the previous PWM control period is within a preset range, and when the voltage difference value is within the preset range, the flux linkage value of the brushless dc motor may be calculated to reduce the calculated frequency and increase the reliability of the calculation. The preset range is obtained by adding a certain margin to the actually measured voltage difference value of the non-conduction opposite potential of each PWM period.

Specifically, according to a commonly used mathematical model of the brushless dc motor, equation (6) is summarized as follows:

wherein e is_bc、e_abIs the line back electromotive voltage of the brushless DC motor.

As can be seen from equation (9), the flux linkage function G (θ) is equivalent to the division of the corresponding two line back emf. Fig. 8 shows a line back electromotive force waveform of the brushless dc motor. In an electric period of 0-2 pi, when ω t is pi/6, pi/2, 5 pi/6, 7 pi/6, 3 pi/2 and 11 pi/6 respectively, the line counter electromotive force e_ca、e_bc、e_ab、e_ca、e_bc、e_abThe values of (a) are in turn zero and correspond respectively to 6 commutation moments within one complete electrical cycle. According to the formula (9), the phase commutation time of the brushless dc motor is determined by using the flux linkage function G (θ), which is essentially equal to the division of the two line back electromotive forces, and when the line back electromotive force on the denominator crosses zero, the flux linkage function G (θ) has an infinite value, so that the phase commutation time of the brushless dc motor can be detected. Since the flux linkage function G (θ) eliminates the rotational speed variation of the brushless dc motor, the method is suitable for a wider rotational speed range, for example, when the brushless dc motor is operated at a low speed.

When a pairwise conduction mode (only two phases of windings are controlled to be conducted, and the rest phase of winding is in a suspended state) is adopted, in a complete electric cycle, the flux linkage function G (theta) has 3 expression modes, and the brushless direct current motor in the pairwise conduction mode has 6 phase change phase sequences. Therefore, when the brushless dc motor is controlled to perform commutation by the flux linkage commutation method, it is necessary to determine in advance how the expression of the flux linkage function G (θ) corresponds to the phase sequence of the brushless dc motor. In correspondence with fig. 6, the relationship between the different electrical angle intervals and the expression form of the magnetic linkage function G (θ) can be shown in table 1.

TABLE 1

Interval of electric angle	Flux linkage function G (theta)
		I/IV	G(θ)_ca/bc＝H(θ)_ca/H(θ)_bc
II/V	G(θ)_bc/ab＝H(θ)_bc/H(θ)_ab
		III/VI	G(θ)_ab/ca＝H(θ)_ab/H(θ)_ca

When the flux linkage function G (θ) is actually applied to determine the commutation time of the brushless dc motor, in order to make the commutation point calculated by the flux linkage function G (θ) more accurate, the position of the rotor of the brushless dc motor can be accurately obtained only by using the upper half of the waveform of the flux linkage function G (θ), and correspondingly, the waveform of the flux linkage function G (θ) is as shown in fig. 9, and the commutation time appears at the peak of the waveform of the flux linkage function G (θ).

Therefore, in one embodiment of the present invention, the flux linkage value calculated according to the flux linkage function G (θ) may be compared with a predetermined commutation threshold value, and when the flux linkage value at a certain time is greater than the commutation threshold value, the certain time may be determined as a commutation time, and the brushless dc motor may be controlled to perform commutation.

The commutation threshold may be a fixed value, that is, the fixed value is used to compare with the calculated flux linkage value in the whole control process to determine the commutation time.

Of course, the commutation threshold may include a plurality of commutation thresholds, and the plurality of commutation thresholds may be obtained by: the rotating speed range of the brushless direct current motor is divided into a plurality of intervals, wherein different commutation threshold values are correspondingly arranged in each interval, and the commutation threshold values are in inverse proportion to the rotating speed of the brushless direct current motor.

That is, the commutation threshold in the above embodiment may be set to a fixed value or may be set to a plurality of values, and the plurality of commutation thresholds may be set in stages according to the rotation speed, and the higher the rotation speed, the smaller the corresponding commutation threshold. For example, assume that the rotation speed range of the brushless DC motor is N₀～N_x(x is an integer of 2 or more), the range of the rotation speed of the brushless DC motor can be divided into N₀～N₁、N₁～N₂、…、N_x-1～N_xX intervals in total, when the rotating speed of the brushless DC motor is in N₀～N₁Within the range, the corresponding commutation threshold is M₁(ii) a When the rotating speed of the brushless DC motor is at N₁～N₂Within the range, the corresponding commutation threshold is M₂(ii) a …, respectively; when the rotating speed of the brushless DC motor is at N_x-1～N_xWithin the range, the corresponding commutation threshold is M_x. Wherein the commutation threshold value M₁、M₂、…、M_xAnd decreases in turn.

In practical applications, in addition to comparing the flux linkage value with the commutation threshold value to determine whether to control the brushless dc motor to perform commutation in the above embodiment, whether to control the brushless dc motor to perform commutation may be determined according to the slope of the flux linkage function G (θ).

Specifically, as shown in fig. 10, near the commutation time of the motor, the flux linkage function G (θ)_bc/abIs infinite, i.e. commutation moments always occurIn flux linkage function G (theta)_bc/abThe moment of the transition from positive infinity to negative infinity. Therefore, in the embodiment of the present invention, the motor may be controlled to perform commutation by determining a commutation point of the motor using the slope of the flux linkage function G (θ), for example, when the slope of the flux linkage function G (θ) is greater than a preset slope threshold value.

The preset slope threshold can be set to be a fixed value or a plurality of values, and the preset slope thresholds can be set in a segmented manner according to the rotating speed, and the higher the rotating speed is, the smaller the corresponding preset slope threshold is. For example, assume that the rotation speed range of the brushless DC motor is N₀～N_x(x is an integer of 2 or more), the range of the rotation speed of the brushless DC motor can be divided into N₀～N₁、N₁～N₂、…、N_x-1～N_xX intervals in total, when the rotating speed of the brushless DC motor is in N₀～N₁Within the range, the corresponding preset slope threshold is K₁(ii) a When the rotating speed of the brushless DC motor is at N₁～N₂Within the range, the corresponding preset slope threshold is K₂(ii) a …, respectively; when the rotating speed of the brushless DC motor is at N_x-1～N_xWithin the range, the corresponding preset slope threshold is K_x. Wherein, a slope threshold K is preset₁、K₂、…、K_xAnd decreases in turn.

Therefore, in the low-speed operation stage of the brushless direct current motor, the flux linkage value of the brushless direct current motor is calculated by obtaining the relevant parameters of the brushless direct current motor, and the phase commutation is carried out when the flux linkage value is larger than the phase commutation threshold value (or the slope of the flux linkage function G (theta)) is larger than the preset slope threshold value, so that the problem that the brushless direct current motor cannot correctly commutate due to the fact that the rotating speed of the brushless direct current motor is low can be effectively avoided.

And in the process of starting the motor to run at low speed, when the motor is controlled to carry out phase change, counter potential zero-crossing detection is also carried out, and when the counter potential zero-crossing point is successfully detected for N times (or the counter potential climbing slope is greater than the preset slope), the counter potential zero-crossing method is switched to control the motor.

Further, in an embodiment of the present invention, as shown in fig. 11, when the motor starts to operate at a low speed, the method for detecting the rotor position of the brushless dc motor according to the embodiment of the present invention may include the following steps:

and S501, calculating the flux linkage.

S502, judging whether the calculated flux linkage value is larger than a preset flux linkage threshold value. If yes, go to step S503; if not, step S504 is performed.

And S503, performing phase change control on the motor.

And S504, carrying out counter potential zero crossing detection.

And S505, judging whether the counter potential zero crossing point is detected. If yes, go to step S506; if not, step S509 is performed.

And S506, adding 1 to the number of times of the counter potential zero crossing points which are continuously and successfully detected.

And S507, judging whether the number of times of continuously and successfully detecting the counter electromotive force zero crossing point is greater than N. If yes, go to step S508; if not, the flux linkage method is continuously adopted to control the motor. And N represents that the back emf zero-crossing detection is successful for N times, and the motor is controlled by switching to a back emf zero-crossing method, and the motor can be calibrated according to actual conditions.

And S508, switching to a counter potential zero crossing method to control the motor.

And S509, judging whether the times of continuously and successfully detecting the counter potential zero crossing points are more than or equal to M. If yes, go to step S510; if not, the flux linkage method is continuously adopted to control the motor. Wherein, M represents that after the counter potential zero-crossing detection is successful for M times, once the counter potential zero-crossing detection is failed, the counter potential zero-crossing detection is cleared for the successful times, and the calibration can be specifically carried out according to the actual condition, and M is less than N.

And S510, judging whether counter potential zero-crossing detection is overtime. If yes, go to step S511; if not, return to step S504.

And S511, clearing the times of the successive successful detection of the counter potential zero crossing points.

Therefore, in the process of starting the motor to run at a low speed, the motor is controlled by adopting a flux linkage method, and counter potential zero-crossing detection is carried out in the control process, so that when counter potential zero-crossing points are continuously detected for multiple times, the counter potential zero-crossing method is switched to control the motor.

According to the rotor position detection method of the brushless direct current motor, a flux linkage method and a back electromotive force zero-crossing method are combined, the rotor position of the motor can be accurately detected within a full rotating speed range by the motor, correct phase commutation of the motor is achieved, and therefore reliable operation of the motor within the full rotating speed range is guaranteed. When the rotor position detection method of the embodiment of the invention is applied to a brushless direct current motor in a dust collector, in the process of starting the dust collector to run at a low speed, a magnetic linkage method is adopted to control the motor to carry out phase change, counter potential zero crossing detection is carried out in the phase change process, when the rotor position of the motor can be successfully detected by adopting the counter potential zero crossing method, the motor is controlled by switching to the counter potential zero crossing method, magnetic linkage calculation is carried out when the rotor position of the motor is detected by adopting the counter potential zero crossing method, when a load is suddenly increased, such as when the motor is blocked, the rotor position calculated by adopting the magnetic linkage is normally phase changed, the motor is controlled by switching to the magnetic linkage method, the motor can still correctly carry out phase change and reliable running under the condition that the rotating speed of the motor is rapidly reduced, and when the dust collector returns to normal operation, the motor can be controlled by switching to the counter potential zero crossing method, therefore, the reliable operation of the motor in the full rotating speed range is realized through the switching control of the two modes, and the reliability of the dust collector is effectively improved.

In summary, according to the method for detecting the rotor position of the brushless dc motor in the embodiment of the present invention, in the process of controlling the motor by using the back electromotive force zero crossing method, when the rotor position of the motor is obtained by using the back electromotive force zero crossing method, the rotor position of the motor is also obtained by using the flux linkage method, and whether the back electromotive force zero crossing detection is successful is determined. If the back electromotive force zero-crossing detection is successful, phase change control is carried out on the motor according to the position of the rotor of the motor acquired by the back electromotive force zero-crossing method, and the motor is continuously controlled by adopting the back electromotive force zero-crossing method; and if the back electromotive force zero-crossing detection fails, performing phase change control on the motor according to the rotor position of the motor acquired by the flux linkage method, and starting to control the motor by adopting the flux linkage method. Therefore, when the rotating speed of the motor is suddenly reduced, even if the counter potential is very small, the rotor position of the motor cannot be detected by adopting a counter potential zero-crossing method, the phase change control can be performed on the motor through the rotor position of the motor obtained by a flux linkage method, the motor can be ensured to continuously and normally operate, and the operation reliability of the motor is greatly improved.

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 rotor position detection method of the brushless dc motor described above.

Fig. 12 is a block schematic diagram of a rotor position detecting apparatus of a brushless dc motor according to an embodiment of the present invention. As shown in fig. 12, a rotor position detecting apparatus of a brushless dc motor according to an embodiment of the present invention includes: a first acquisition unit 100, a second acquisition unit 200 and a control unit 300.

The first acquiring unit 100 is configured to acquire a rotor position of the motor by using a back electromotive force zero-crossing method; the second obtaining unit 200 is configured to obtain a rotor position of the motor by using a flux linkage method; the control unit 300 is configured to, when the rotor position of the motor is acquired by the first acquisition unit 100, further acquire the rotor position of the motor by the second acquisition unit 200 and determine whether the counter potential zero-crossing detection is successful in the process of controlling the motor by the counter potential zero-crossing method. If the back emf zero-crossing detection is successful, the control unit 300 performs phase change control on the motor according to the rotor position of the motor acquired by the first acquisition unit 100, and continues to control the motor by adopting a back emf zero-crossing method; if the back electromotive force zero-crossing detection fails, the control unit 300 performs phase commutation control on the motor according to the rotor position of the motor acquired by the second acquisition unit 200, and starts to perform control on the motor by using a flux linkage method.

According to an embodiment of the present invention, in the process of controlling the motor by using the flux linkage method, the control unit 300 further obtains the rotor position of the motor through the first obtaining unit 100, and determines whether the number of times of the back electromotive force zero-crossing detection success is greater than or equal to a preset number, wherein if the number of times of the back electromotive force zero-crossing detection success is less than the preset number, the control unit 300 continues to control the motor by using the flux linkage method; if the counter potential zero crossing detection is successful more than or equal to the preset number of times, the control unit 300 starts to control the motor by adopting the counter potential zero crossing method.

According to another embodiment of the present invention, in the process of controlling the motor by using the flux linkage method, the control unit 300 further obtains the rotor position of the motor through the first obtaining unit 100, obtains the back electromotive force climbing slope of the motor, and determines whether the back electromotive force climbing slope is greater than or equal to a preset slope, wherein if the back electromotive force climbing slope is less than the preset slope, the control unit 300 continues to control the motor by using the flux linkage method; if the back emf ramp slope is greater than or equal to the preset slope, the control unit 300 starts to control the motor by adopting a back emf zero-crossing method.

According to an embodiment of the present invention, when the control unit 300 controls the motor using the flux linkage method, wherein the control unit 300 obtains the temperature-phase resistance table, the temperature-phase inductance table, and the bus voltage-phase current change rate table of the motor off-line, and obtains the conductive phase positive terminal voltage, the conductive phase negative terminal voltage, the non-conductive opposite potential voltage, the bus current instantaneous value, the bus voltage, and the current winding temperature during the high level time of each PWM control period, and obtains the phase current change rate of the motor from the bus voltage and the bus voltage-phase current change rate table, and obtains the phase resistance and the phase inductance of the motor from the current winding temperature and the temperature-phase resistance table, the temperature-phase inductance table, and obtains the phase resistance and the phase inductance of the motor from the conductive phase positive terminal voltage, the conductive phase negative terminal voltage, the non-conductive opposite potential voltage, the bus current instantaneous value, And the phase current change rate, the phase resistance and the phase inductance are used for carrying out phase change control on the motor.

According to another embodiment of the present invention, when the control unit 300 controls the motor by using the flux linkage method, wherein the control unit 300 obtains the temperature-phase resistance table and the temperature-phase inductance table of the motor offline, and obtains the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the instantaneous value of the bus current and the current winding temperature during the high level time of each PWM control period, and obtains the phase currents of the motor corresponding to any two times, and obtains the phase current change rate of the motor according to the phase currents of the motor corresponding to any two times, and obtains the phase resistance and the phase inductance of the motor according to the current winding temperature, the temperature-phase resistance table and the temperature-phase inductance table, and obtains the phase resistance and the phase inductance of the motor according to the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, And the instantaneous value of the bus current, the phase current change rate, the phase resistance and the phase inductance are used for carrying out phase change control on the motor.

According to an embodiment of the present invention, when the control unit 300 performs commutation control on the motor according to the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance, wherein the control unit 300 obtains the flux linkage value of the motor or the slope of the flux linkage function G (θ) according to the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance, wherein if the flux linkage value of the motor is greater than a preset flux linkage threshold value or the slope of the flux linkage function G (θ) is greater than a preset slope threshold value, the motor is controlled to perform commutation.

According to an embodiment of the present invention, the control unit 300 is further configured to determine whether a voltage difference value between the non-conducting opposite potential voltage in the current PWM control period and the non-conducting opposite potential voltage in the previous PWM control period is within a preset range before acquiring the flux linkage value of the motor or the slope of the flux linkage function G (θ), wherein if the voltage difference value is within the preset range, the flux linkage value of the motor or the slope of the flux linkage function G (θ) is acquired.

It should be noted that, details that are not disclosed in the rotor position detecting device of the brushless dc motor according to the embodiment of the present invention refer to details that are disclosed in the rotor position detecting method of the brushless dc motor according to the embodiment of the present invention, and detailed descriptions thereof are omitted here.

In addition, an embodiment of the present invention further provides a control system of a brushless dc motor, which includes the rotor position detection device of the brushless dc 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 rotor position detection method of a brushless direct current motor is characterized by comprising the following steps:

in the process of controlling the motor by adopting a counter electromotive force zero-crossing method, when the rotor position of the motor is obtained by adopting the counter electromotive force zero-crossing method, the rotor position of the motor is also obtained by adopting a flux linkage method;

judging whether counter potential zero-crossing detection is successful or not;

if the back electromotive force zero-crossing detection is successful, performing phase commutation control on the motor according to the rotor position of the motor acquired by the back electromotive force zero-crossing method, and continuously controlling the motor by adopting the back electromotive force zero-crossing method;

and if the back electromotive force zero-crossing detection fails, performing phase commutation control on the motor according to the rotor position of the motor acquired by the flux linkage method, and starting to control the motor by adopting the flux linkage method.

2. The rotor position detecting method of a brushless DC motor according to claim 1,

in the process of controlling the motor by adopting the flux linkage method, the counter electromotive force zero-crossing method is also adopted to obtain the rotor position of the motor, and whether the times of successful counter electromotive force zero-crossing detection is more than or equal to the preset times or whether the counter electromotive force climbing slope of the motor is more than or equal to the preset slope is judged;

if the counter electromotive force zero-crossing detection is successful for a time less than the preset time or the counter electromotive force climbing slope is less than the preset slope, continuing to control the motor by adopting the flux linkage method;

and if the counter electromotive force zero-crossing detection is successful for more than or equal to the preset times or the counter electromotive force climbing slope is more than or equal to the preset slope, starting to control the motor by adopting the counter electromotive force zero-crossing method.

3. The method of detecting a rotor position of a brushless dc motor according to claim 2, wherein the controlling the motor by the flux linkage method includes:

obtaining a temperature-phase resistance meter, a temperature-phase inductance meter and a bus voltage-phase current change rate table of the motor in an off-line manner;

within the high level time of each PWM control period, acquiring conducting phase positive end voltage, conducting phase negative end voltage, non-conducting opposite potential voltage, bus current instantaneous value, bus voltage and current winding temperature;

acquiring the phase current change rate of the motor according to the bus voltage and the bus voltage-phase current change rate table, and acquiring the phase resistance and the phase inductance of the motor according to the current winding temperature, the temperature-phase resistance table and the temperature-phase inductance table;

and carrying out phase change control on the motor according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance.

4. The method of detecting a rotor position of a brushless dc motor according to claim 2, wherein the controlling the motor by the flux linkage method includes:

obtaining a temperature-phase resistance meter and a temperature-phase inductance meter of the motor in an off-line manner;

in the high level time of each PWM control period, acquiring conducting phase positive end voltage, conducting phase negative end voltage, non-conducting opposite potential voltage, bus current instantaneous value and current winding temperature, and acquiring phase currents of the motor corresponding to any two moments;

obtaining the phase current change rate of the motor according to the phase currents of the motor corresponding to the any two moments and the any two moments, and obtaining the phase resistance and the phase inductance of the motor according to the current winding temperature, the temperature-phase resistance meter and the temperature-phase inductance meter;

5. The rotor position detecting method of a brushless dc motor according to claim 3 or 4, wherein said phase-change control of the motor based on the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance, and the phase inductance comprises:

acquiring a flux linkage value of the motor or a slope of a flux linkage function G (theta) according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance;

and if the flux linkage value of the motor is larger than a preset flux linkage threshold value or the gradient of the flux linkage function G (theta) is larger than a preset gradient threshold value, controlling the motor to carry out phase commutation.

6. The rotor position detecting method of a brushless dc motor according to claim 5, further comprising, before acquiring a flux linkage value of the motor or a slope of a flux linkage function G (θ):

judging whether a voltage difference value between the non-conduction opposite potential voltage in the current PWM control period and the non-conduction opposite potential voltage in the previous PWM control period is within a preset range or not;

and if the voltage difference value is within the preset range, acquiring the flux linkage value of the motor or the slope of a flux linkage function G (theta).

7. 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 rotor position detection method of a brushless dc motor according to any one of claims 1-6.

8. A rotor position detecting device of a brushless dc motor, comprising:

the first acquisition unit is used for acquiring the rotor position of the motor by adopting a counter electromotive force zero crossing method;

the second acquisition unit is used for acquiring the rotor position of the motor by adopting a flux linkage method;

a control unit configured to, when the rotor position of the motor is acquired by the first acquisition unit, acquire the rotor position of the motor by the second acquisition unit and determine whether back emf zero-crossing detection is successful in controlling the motor by the back emf zero-crossing method,

if the back electromotive force zero-crossing detection is successful, the control unit performs phase change control on the motor according to the rotor position of the motor acquired by the first acquisition unit and continues to control the motor by adopting a back electromotive force zero-crossing method;

and if the back electromotive force zero-crossing detection fails, the control unit performs phase change control on the motor according to the rotor position of the motor acquired by the second acquisition unit and starts to control the motor by adopting the flux linkage method.

9. The rotor position detecting apparatus of a brushless DC motor according to claim 8,

the control unit also acquires the rotor position of the motor through the first acquisition unit in the process of controlling the motor by adopting the flux linkage method, and judges whether the times of counter potential zero-crossing detection success are more than or equal to preset times or whether the counter potential climbing slope of the motor is more than or equal to a preset slope or not, wherein,

if the counter potential zero-crossing detection is successful for a number of times smaller than the preset number of times or the counter potential climbing slope is smaller than the preset slope, the control unit continues to control the motor by adopting the flux linkage method;

and if the counter electromotive force zero-crossing detection is successful for more than or equal to the preset times or the counter electromotive force climbing slope is more than or equal to the preset slope, the control unit starts to control the motor by adopting the counter electromotive force zero-crossing method.

10. The rotor position detecting apparatus of a brushless dc motor according to claim 9, wherein the control unit obtains a temperature-phase resistance table, a temperature-phase inductance table, and a bus voltage-phase current change rate table of the motor offline, and obtains a conducting phase positive terminal voltage, a conducting phase negative terminal voltage, a non-conducting opposite potential voltage, a bus current instantaneous value, a bus voltage, and a current winding temperature during a high level time of each PWM control period, and obtains a phase current change rate of the motor from the bus voltage and the bus voltage-phase current change rate table, and obtains a phase resistance and a phase inductance of the motor from the current winding temperature and the temperature-phase resistance table, the temperature-phase inductance table, when controlling the motor using the flux linkage method, and carrying out phase change control on the motor according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance.

11. The apparatus of claim 9, wherein the control unit obtains a temperature-phase resistance table and a temperature-phase inductance table of the motor offline while controlling the motor using the flux linkage method, and obtains a conducting phase positive terminal voltage, a conducting phase negative terminal voltage, a non-conducting opposite potential voltage, a bus current instantaneous value, and a current winding temperature during a high level time of each PWM control period, and obtains phase currents of the motor corresponding to any two times, and obtains a phase current change rate of the motor according to the any two times and the phase currents of the motor corresponding to the any two times, and obtains a phase resistance and a phase inductance of the motor according to the current winding temperature and the temperature-phase resistance table, and the temperature-phase inductance table, and carrying out phase change control on the motor according to the conducting phase positive end voltage, the conducting phase negative end voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance and the phase inductance.

12. The rotor position detecting apparatus of a brushless dc motor according to claim 10 or 11, wherein the control unit performs phase change control of the motor based on the conducting phase positive terminal voltage, the conducting phase negative terminal voltage, the non-conducting opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance, and the phase inductance, wherein,

the control unit acquires a flux linkage value of the motor or a slope of a flux linkage function G (theta) according to the conductive phase positive end voltage, the conductive phase negative end voltage, the non-conductive opposite potential voltage, the bus current instantaneous value, the phase current change rate, the phase resistance, and the phase inductance, wherein,

13. The rotor position detecting apparatus of a brushless dc motor according to claim 12, wherein the control unit is further configured to determine whether a voltage difference value between the non-conductive opposite potential voltage in a current PWM control period and a non-conductive opposite potential voltage in a previous PWM control period is within a preset range before acquiring the flux linkage value of the motor or the slope of the flux linkage function G (θ), and if the voltage difference value is within the preset range, acquire the flux linkage value of the motor or the slope of the flux linkage function G (θ).

14. A control system of a brushless dc motor, comprising a rotor position detection device of a brushless dc motor according to any one of claims 8 to 13.

15. A vacuum cleaner comprising a control system for a brushless dc motor according to claim 14.