CN112968649B

CN112968649B - Motor braking control method, device, equipment and computer readable storage medium

Info

Publication number: CN112968649B
Application number: CN202110191876.9A
Authority: CN
Inventors: 李晋
Original assignee: Wuxi Little Swan Electric Co Ltd
Current assignee: Wuxi Little Swan Electric Co Ltd
Priority date: 2021-02-19
Filing date: 2021-02-19
Publication date: 2023-03-03
Anticipated expiration: 2041-02-19
Also published as: CN112968649A

Abstract

The application provides a motor braking control method, a device, equipment and a computer readable storage medium, wherein the method comprises the following steps: controlling a switching tube of the inverter to be switched to a braking state in response to a received braking instruction for controlling the motor to stop; controlling a current detection device to sample the current of the switching tube to obtain a first sampling current; determining a first rotor speed of the electric machine based on the first sampled current; and determining that the motor braking is finished under the condition that the first rotor rotating speed reaches a braking stop ending condition. Therefore, an additional brake circuit is not needed to be added, the cost can be reduced, when the rotating speed of the first rotor reaches the brake stopping end condition, the motor brake is determined to be completed, and the accuracy of determining the complete stopping state and time of the motor can be improved.

Description

Motor braking control method, device, equipment and computer readable storage medium

Technical Field

The application relates to the technical field of automation control, and relates to but is not limited to a motor braking control method, a motor braking control device, motor braking control equipment and a computer readable storage medium.

Background

The operation and stop control of the three-phase brushless direct current motor and the permanent magnet synchronous motor is realized by controlling an inverter in a frequency conversion controller, and the stop of the motor can adopt methods such as common stop, emergency stop, braking and the like. The sudden stop and the brake stop can be divided into a brake circuit brake stop and a self-braking stop.

In the common shutdown method, the motor can continuously run for a period of time due to inertia when the motor is shut down, the motor is still in a power generation state, the service life and the reliability of the electrolytic capacitor can be reduced by the counter electromotive force generated by the motor, and faults such as failure, even explosion and the like can be caused in serious cases; the braking circuit braking shutdown method needs to additionally add a braking loop on the variable frequency controller, so that the cost is higher; the self-braking shutdown method does not need to add an additional braking loop on the frequency conversion controller, although the shutdown method has lower cost, the shutdown time is not easy to control, and the controller is difficult to obtain the state and the moment of whether the motor completely stops.

Disclosure of Invention

In view of the above, embodiments of the present application provide a motor braking control method, device, apparatus, and computer-readable storage medium.

The technical scheme of the embodiment of the application is realized as follows:

the embodiment of the application provides a motor braking control method, which comprises the following steps:

controlling a switching tube of the inverter to be switched to a braking state in response to a received braking instruction for controlling the motor to stop;

controlling a current detection device to sample the current of the switching tube to obtain a first sampling current;

determining a first rotor speed of the electric machine based on the first sampled current;

and determining that the motor braking is finished under the condition that the first rotor rotating speed reaches a braking stop ending condition.

In some embodiments, the inverter includes a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube and a sixth switching tube;

the switching tube of the control inverter is switched to a braking state, and the control inverter comprises:

controlling a first switching tube, a third switching tube and a fifth switching tube of the inverter to be switched to a disconnected state;

and controlling a second switching tube, a fourth switching tube and a sixth switching tube of the inverter to be switched to a closed state.

In some embodiments, the method further comprises:

initializing brake parameters of the motor;

a first controller for controlling a speed loop of the motor is closed, and a second controller for controlling a current loop of the motor is closed;

and controlling a current detection device of the motor to be started, and controlling a speed position observer of the motor to be started.

In some embodiments, said determining a first rotor speed of said electric machine based on said first sampled current comprises:

acquiring characteristic parameters of the motor, wherein the characteristic parameters comprise stator resistance, direct axis inductance, quadrature axis inductance and back electromotive force coefficient;

determining a two-phase current of the motor under a rotating coordinate system based on the first sampling current;

determining a back electromotive force of the electric machine based on the two-phase current, the stator resistance, the direct-axis inductance, and the quadrature-axis inductance;

determining the rotating speed of a first motor according to the counter electromotive force and the counter electromotive force coefficient;

and carrying out filtering processing on the rotating speed of the first motor to obtain the first rotor rotating speed of the motor.

In some embodiments, the determining a back emf of the electric machine based on the two-phase current, the stator resistance, the direct-axis inductance, and the quadrature-axis inductance includes:

acquiring a second rotor rotating speed determined based on a second sampling current, wherein the second sampling current is obtained by sampling the current of the switching tube last time by the current detection device;

determining a direct-axis current and a quadrature-axis current of the motor from the two-phase currents;

determining back electromotive force direct-axis voltage of the motor according to the second rotor rotating speed, the direct-axis current, the stator resistance and the direct-axis inductance;

determining back electromotive force quadrature axis voltage of the motor according to the second rotor rotating speed, the quadrature axis current, the stator resistance and the quadrature axis inductance;

and determining the counter electromotive force of the motor according to the counter electromotive force direct-axis voltage and the counter electromotive force quadrature-axis voltage.

In some embodiments, the determining the direct-axis current and the quadrature-axis current of the motor from the two-phase currents includes:

determining a second rotor angle based on the second rotor speed;

and determining the direct-axis current and the quadrature-axis current of the motor under a rotating coordinate system according to the second rotor angle and the two-phase current.

In some embodiments, the method further comprises:

determining whether the first rotor rotating speed reaches a preset threshold value;

under the condition that the first rotor rotating speed reaches a preset threshold value, acquiring the duration of the first rotor rotating speed reaching the preset threshold value;

and under the condition that the duration reaches a preset duration threshold, determining that the rotating speed of the first rotor reaches a brake shutdown ending condition.

In some embodiments, the method further comprises:

under the condition that the first rotor rotating speed does not reach a preset threshold value or the duration time does not reach a preset time threshold value, determining that the first rotor rotating speed does not reach a braking shutdown ending condition;

and controlling the current detection device to sample the current of the switching tube for the next time.

In some embodiments, the method further comprises:

and controlling a second switching tube, a fourth switching tube and a sixth switching tube of the inverter to be switched to a disconnected state.

The embodiment of the application provides a motor brake control device, the device includes:

the first control module is used for responding to a received braking instruction for controlling the motor to stop and controlling a switching tube of the inverter to be switched to a braking state;

the second control module is used for controlling the current detection device to sample the current of the switching tube to obtain a first sampling current;

a first determination module for determining a first rotor speed of the motor based on the first sampled current;

and the second determining module is used for determining that the motor braking is finished under the condition that the first rotor rotating speed reaches the braking stop ending condition.

The embodiment of the application provides a motor braking controlgear, includes:

a memory for storing executable instructions;

and the processor is used for realizing the method provided by the embodiment of the application when executing the executable instructions stored in the memory.

Embodiments of the present application provide a computer-readable storage medium, which stores executable instructions for causing a processor to implement the method provided by the embodiments of the present application when the processor executes the executable instructions.

The embodiment of the application provides a motor braking control method, a device, equipment and a computer readable storage medium, wherein the method comprises the following steps: in response to a received braking instruction for controlling the motor to stop, controlling a switching tube of the inverter to be switched to a braking state; controlling a current detection device to sample the current of the switching tube to obtain a first sampling current; determining a first rotor speed of the electric machine based on the first sampled current; and determining that the motor braking is finished under the condition that the first rotor rotating speed reaches the braking stop ending condition. Therefore, an additional brake circuit is not required to be added, the equipment cost can be reduced, when the rotating speed of the first rotor reaches the brake stopping ending condition, the motor brake is determined to be completed, and the accuracy of determining the complete stopping state and time of the motor can be improved. The motor brake control method provided by the embodiment of the application is applied to the motor of the washing machine, and the cost of the motor brake control equipment is reduced, so that the cost of the washing machine can be reduced; and because when the rotating speed of the first rotor reaches the braking and stopping ending condition, the braking of the motor is determined to be completed, the accuracy rate of determining the complete stopping state and time of the motor can be improved, the rotating speed of the drum of the washing machine can be determined, the accurate control of the washing machine is further realized, and the accuracy of the washing time is ensured.

Drawings

In the drawings, which are not necessarily drawn to scale, like reference numerals may describe similar components in different views. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed herein.

Fig. 1 is a schematic flow chart of an implementation of a motor braking control method provided in an embodiment of the present application;

fig. 2 is a schematic flow chart of another implementation of a motor braking control method provided in the embodiment of the present application;

fig. 3 is a schematic structural diagram of a frequency converter according to an embodiment of the present application;

fig. 4 is a schematic flow chart of an implementation of the dc motor shutdown control method provided in the embodiment of the present application;

fig. 5 is a schematic diagram of an experimental test of a shutdown control method of a dc motor according to an embodiment of the present application;

fig. 6 is a schematic structural diagram of a motor brake control device provided in an embodiment of the present application;

fig. 7 is a schematic structural diagram of a motor brake control device according to an embodiment of the present application.

Detailed Description

In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be described in further detail with reference to the accompanying drawings, the described embodiments should not be considered as limiting the present application, and all other embodiments obtained by a person of ordinary skill in the art without making creative efforts fall within the protection scope of the present application.

In the following description, reference is made to "some embodiments" which describe a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.

In the following description, references to the terms "first \ second \ third" are only to distinguish similar objects and do not denote a particular order, but rather the terms "first \ second \ third" are used to interchange specific orders or sequences, where appropriate, so as to enable the embodiments of the application described herein to be practiced in other than the order shown or described herein.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of the present application only and is not intended to be limiting of the application.

Based on the problems that the braking downtime is not easy to control and it is difficult to determine the state and time when the motor is completely stopped in the related art, the embodiment of the application provides a motor braking control method applied to the motor. The method provided by the embodiment of the present application may be implemented by a computer program, and when the computer program is executed, each step in the motor braking control method provided by the embodiment of the present application is completed. In some embodiments, the computer program may be executed by a processor in the motor brake control device. Fig. 1 is a schematic implementation flow diagram of a motor braking control method provided in an embodiment of the present application, and as shown in fig. 1, the motor braking control method includes the following steps:

and S101, in response to a received braking instruction for controlling the motor to stop, controlling a switching tube of the inverter to be switched to a braking state.

In the embodiment of the present application, the motor brake control device is used for controlling the motor brake shutdown, and applicable motor types include, but are not limited to: a Brushless Direct Current Motor (BLDCM), a Surface-mounted Permanent Magnet Synchronous Motor (SPMSM), or an Interior Permanent Magnet Synchronous Motor (IPMSM). The motor braking control method provided by the embodiment of the application can be applied to motors of household appliances such as washing machines, clothes dryers and the like, and the application to the washing machines is taken as an example and explained below.

When the motor is stopped, a braking instruction is triggered, and the braking instruction can be triggered based on manual stop operation of a user; or triggered by a timer, e.g., reaching a set down time; it may also be triggered by other operation instructions, for example, the other operation instructions may be an operation instruction to end the dehydration process.

And after the motor brake control equipment receives a brake instruction, the switching tube of the inverter is controlled to be switched to a brake state.

In this embodiment of the application, the inverter may include a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a fifth switching tube, and a sixth switching tube, and form three upper bridge arms and three lower bridge arms of three bridges. For example, the first switching tube, the third switching tube and the fifth switching tube form three upper bridge arms, and the second switching tube, the fourth switching tube and the sixth switching tube form three lower bridge arms. When the brake state is switched, the first switch tube, the third switch tube and the fifth switch tube are switched to an off state, and the second switch tube, the fourth switch tube and the sixth switch tube are switched to an on state, so that the second switch tube, the fourth switch tube and the sixth switch tube are short-circuited and switched to the brake state.

Here, the first switch tube is denoted S ₁ And the third switching tube is denoted as S ₃ The fifth switch tube is denoted as S ₅ Switching the first switch tube, the third switch tube and the fifth switch tube to an off state, namely setting S ₁ ＝Off，S ₃ ＝Off，S ₅ ＝Off。

The second switch tube is denoted as S ₂ The fourth switch tube is denoted as S ₄ The sixth switching tube is denoted as S ₆ Switching the second switching tube, the fourth switching tube and the sixth switching tube to a closed state, namely setting S ₂ ＝On，S ₄ ＝On，S ₆ ＝On。

The switch tube may be a Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), or may be an Insulated Gate Bipolar Transistor (IGBT), which is not limited in the embodiment of the present invention.

And S102, controlling a current detection device to sample the current of the switching tube to obtain a first sampling current.

In the process of braking and stopping, the current detection device samples the current of the switch tube to obtain a first sampling current. The above examples are still illustrative:

controlling the current detection device to sample the current of the second switching tube to obtain a first phase current i _u Controlling the current of the fourth switching tube to be sampled to obtain a second phase current i _v Controlling the current of the sixth switching tube to be sampled to obtain a third phase current i _w To obtain a first sampled current, i.e. a three-phase current i _u ，i _v ，i _w 。

Step S103, determining a first rotor rotating speed of the motor based on the first sampling current.

According to the first sampling current i _u ，i _v ，i _w Determining a first rotor speed ω of an electric machine _e . In implementation, the first sampling current (i.e. three-phase current) i can be firstly obtained _u ，i _v ，i _w Determining two-phase current i in rotating coordinate system _α ，i _β (ii) a Then based on the two-phase current i _α ，i _β Determination of the direct-axis current i _d And quadrature axis current i _q According to the direct axis current i _d And quadrature axis current i _q Calculating to obtain the back electromotive force direct axis voltage E _d And back electromotive force quadrature axis voltage E _q Direct axis voltage E from back EMF _d And back electromotive force quadrature axis voltage E _q Determining the back electromotive force E of an electric machine _s According to back electromotive force E _s Calculating the first motor rotation speed omega, and finally filtering the first motor rotation speed omega through a Low Pass Filter (LPF) to obtain the first rotor rotation speed omega _e 。

And step S104, determining that the motor braking is finished under the condition that the first rotor rotating speed reaches the braking stop ending condition.

Judging the first rotor speed omega of the motor _e Whether the brake stop end condition is reached or not, when the first rotor speed omega _e And when the braking stop ending condition is met, the second switching tube, the fourth switching tube and the sixth switching tube of the inverter are controlled to be switched to an off state from an on state, namely all bridge arm outputs of the inverter are closed, and the motor braking is finished.

The motor braking control method provided by the embodiment of the application is applied to the motor of the washing machine, an additional braking loop is not needed, the cost of motor braking control equipment can be reduced, and therefore the cost of the washing machine can be reduced; and because when the rotating speed of the first rotor reaches the braking and stopping ending condition, the braking of the motor is determined to be completed, the accuracy rate of determining the complete stopping state and time of the motor can be improved, the rotating speed of the drum of the washing machine can be determined, the accurate control of the washing machine is further realized, and the accuracy of the washing time is ensured.

According to the motor brake control method provided by the embodiment of the application, the motor brake control equipment responds to a received brake instruction for controlling the motor to stop, and controls the switching tube of the inverter to be switched to a brake state; controlling a current detection device to sample the current of the switching tube to obtain a first sampling current; determining a first rotor speed of the electric machine based on the first sampled current; and determining that the motor braking is finished under the condition that the first rotor rotating speed reaches a braking stop ending condition. According to the motor braking control method provided by the embodiment of the application, an additional braking loop is not required to be added, the cost of motor braking control equipment can be reduced, the motor braking is determined to be finished when the rotating speed of the first rotor reaches the braking stop end condition, and the accuracy rate of determining the complete stop state and time of the motor can be improved; the motor braking control method provided by the embodiment of the application is applied to the washing machine, so that the cost of the washing machine can be reduced, the accurate control of the washing machine can be realized, and the accuracy of the washing time is ensured.

In some embodiments, before step S102 of the embodiment shown in fig. 1, the method further comprises:

and step S111, initializing the braking parameters of the motor.

Here, the braking parameters include a motor rotation speed, a direct axis current, a quadrature axis current, a direct axis speed, and a quadrature axis speed. And initializing the braking parameters, namely setting the rotating speed of the motor, the direct axis current, the quadrature axis current, the direct axis speed and the quadrature axis speed as initial values 0.

In step S112, the first controller that controls the speed loop of the motor is turned off.

In step S113, the second controller that controls the current loop of the motor is turned off.

And step S114, controlling a current detection device of the motor to be started.

And step S115, controlling the speed position observer of the motor to be started.

The steps S111 to S115 are brake control preparation steps, the steps S111 to S115 are completed, and the braking process can be performed after the switching tube of the inverter is switched to the braking state.

It should be noted that, after receiving the braking instruction for controlling the motor to stop, the above steps S111 to S115 may be executed first, and then the switching tube of the inverter is controlled to switch to the braking state; or the switching tube of the inverter can be controlled to switch to the braking state first, and then the step S111 to the step S115 are executed; the switching tube of the inverter can be controlled to be switched to the braking state between any two steps from step S111 to step S115.

In some embodiments, step S103 "determining the first rotor speed of the motor based on the first sampled current" in the embodiment shown in fig. 1 may be implemented by:

and step S1031, obtaining characteristic parameters of the motor.

Here, the characteristic parameter includes a stator resistance R _s Straight axis inductor L _d Quadrature axis inductor L _q And back electromotive force coefficient K _e 。

Step S1032 determines a two-phase current of the motor in the rotating coordinate system based on the first sampling current.

According to a first sampled current (i.e. three-phase current) i _u ，i _v ，i _w Determining two-phase current i in rotating coordinate system _α ，i _β The calculation formulas are respectively shown in the following formulas (1) and (2):

i _α(n) ＝i _u (1)；

wherein n is a sampling ordinal number, and n =1,2,3, \8230;.

Step S1033 of determining a back electromotive force of the motor based on the two-phase current, the stator resistance, the direct axis inductance, and the quadrature axis inductance.

In implementation, the two-phase current i is firstly based on _α ，i _β Determining the direct-axis current i _d And quadrature axis current i _q Then according to the direct axis current i _d And quadrature axis current i _q Calculating to obtain back electromotive force direct axis voltage E _d And back electromotive force quadrature axis voltage E _q Finally, according to the back electromotive force direct axis voltage E _d And back electromotive force quadrature axis voltage E _q Determining the back electromotive force E of an electric machine _s 。

And S1034, determining the rotating speed of the first motor according to the counter electromotive force and the counter electromotive force coefficient.

According to determined back electromotive force E _s And the back electromotive force coefficient K of the motor _e The first motor rotation speed ω can be determined by the following equation (3).

Step S1035, performing filtering processing on the first motor rotation speed to obtain a first rotor rotation speed of the motor.

The first motor rotation speed omega is filtered by a low pass filter LPF to obtain a signal with a frequency higher than a cut-off frequency, and the first rotor rotation speed omega is obtained _e . In the embodiment of the application, LPF (ω) is used to perform filtering processing on the first motor rotation speed, and then the first rotor rotation speed of the motor is represented as ω _e = LPF (ω). By the method, the accuracy of the first rotor rotating speed of the motor can be ensured, so that the method is applied to the washing machine, the rotating speed of the drum of the washing machine can be determined, and the washing machine can be accurately controlled.

In some embodiments, the step S1033 "of determining the back electromotive force of the motor based on the two-phase current, the stator resistance, the direct-axis inductance, and the quadrature-axis inductance" may be implemented by:

in step S10331, a second rotor rotational speed determined based on the second sampling current is acquired.

Here, the second sampling current is obtained by sampling the current of the switching tube last time by the current detection device. In the embodiment of the present application, the second sampling current is denoted as i _u ′，i _v ′，i _w ', and the second rotor speed is denoted by ω _e ′。

Step S10332 determines a direct-axis current and a quadrature-axis current of the motor from the two-phase currents.

In some embodiments, step S10332 may be implemented as:

step S03321, determining a second rotor angle based on said second rotor speed.

As shown in equation (4), the second rotor speed is represented as ω _e ' integral over time t to obtain the second rotor angle theta _e ′。

θ _e ′＝∫ω _e ′dt (4)；

Step S03322, determining a direct axis current of the motor in a rotating coordinate system according to the second rotor angle and the two-phase sampling current.

According to two-phase current i _α 、i _β And a second rotor angle theta _e ', the determined direct axis current is denoted as i _d And can be represented by formula (5):

i _d ＝i _α *cos(θ _e ′)+i _β *sin(θ _e ′) (5)；

step S03323, determining a quadrature axis current of the motor in the rotating coordinate system according to the second rotor angle and the two-phase sampling current.

According to two-phase current i _α 、i _β And a second rotor angle theta _e ', the determined quadrature axis current being denoted as i _q And can be represented by formula (6):

i _q ＝i _β *cos(θ _e ′)-i _α *sin(θ _e ′) (6)；

step S10333, determining a back electromotive force direct axis voltage of the motor according to the second rotor speed, the direct axis current, the stator resistance, and the direct axis inductance.

From the second rotor speed ω _e ' straight axis current i _d Stator resistor R _s And a direct axis inductor L _d Determining the back EMF direct axis voltage E of the motor _d And can be represented by formula (7):

E _d ＝R _s *i _d -ω _e ′*L _d *i _d (7)；

step S10334, determining back electromotive force quadrature axis voltage of the motor according to the second rotor speed, the quadrature axis current, the stator resistance, and the quadrature axis inductance.

From the second rotor speed ω _e ' quadrature axis current i _q Stator resistor R _s And quadrature axis inductance L _q Determining the back electromotive force quadrature axis voltage E of the motor _q And can be represented by formula (8):

E _q ＝R _s *i _q +ω _e ′*L _q *i _q (8)；

step S10335, determining a back electromotive force of the motor according to the back electromotive force direct axis voltage and the back electromotive force quadrature axis voltage.

In the embodiment of the present application, the back electromotive force E of the motor can be calculated according to the following formula (9) _s ：

Thus, the back electromotive force E of the motor is obtained _s 。

In some embodiments, before step S104 of the embodiment shown in fig. 1, the method may further include the steps of:

step S131, determining whether the first rotor speed reaches a preset threshold value.

In the embodiment of the present application, the preset threshold may be set to 0, and when the first rotor speed reaches the preset threshold, i.e. ω is ω _e If =0, the flow proceeds to step S132 to acquire the duration; when the first rotor speed does not reach the preset threshold value, i.e. ω _e If > 0, it indicates that the motor is still running, and the process proceeds to step S135.

Step S132, acquiring the duration of the first rotor speed reaching a preset threshold value.

When ω is _e And when the value is =0, starting a timer to start timing to obtain the duration t.

Step S133, determining whether the duration reaches a preset duration threshold.

In the embodiment of the present application, the preset duration threshold is represented as T _s When the duration of the first rotor speed reaching the preset threshold reaches the preset duration threshold, namely T is more than or equal to T _s Then, determining that the motor has stopped running and has reached a steady state, and then entering step S134; when the duration of the first rotor reaching the preset threshold is less than the preset duration threshold, namely T is less than T _s If it is determined that the motor has stopped operating, the motor has not reached a steady state, and the process proceeds to step S135.

And step S134, determining that the first rotor speed reaches a brake shutdown end condition.

At this time, the second switching tube, the fourth switching tube and the sixth switching tube of the inverter can be controlled to be switched from the closed state to the open state, so that all the switching tubes of the inverter are switched to the open state, that is, all bridge arm outputs of the inverter are closed, and the motor braking is completed.

And step S135, determining that the first rotor rotating speed does not reach the braking stop ending condition.

And step S136, controlling the current detection device to sample the current of the switching tube for the next time.

And when the motor is not decelerated to 0 or the motor is decelerated to 0 but does not reach a stable state, continuing sampling the switching tube until the rotating speed of the first rotor reaches a braking stop ending condition, and determining that the motor is braked. According to the motor braking control method provided by the embodiment of the application, an additional braking loop is not needed to be added, the cost of motor braking control equipment can be reduced, the motor braking is determined to be completed when the rotating speed of the first rotor reaches the braking stop ending condition, and the accuracy rate of determining the complete stop state and time of the motor can be improved.

Fig. 2 is a schematic flow chart of another implementation of a motor braking control method provided in an embodiment of the present application, where the motor braking control method is applied to a motor braking control device, and the motor braking control device in the embodiment of the present application is described by taking a clothes dryer as an example. As shown in fig. 2, a motor braking control method provided in an embodiment of the present application includes the following steps:

step S201, receiving a braking instruction for controlling the motor to stop.

Step S202, initializing the braking parameters of the motor.

Here, the braking parameters include a motor rotation speed, a direct-axis current, a quadrature-axis current, a direct-axis speed, and a quadrature-axis speed.

In step S203, the first controller that controls the speed loop of the motor is turned off.

In step S204, the second controller that controls the current loop of the motor is turned off.

And S205, controlling a current detection device of the motor to be started.

And step S206, controlling a speed position observer of the motor to be started.

And step S207, controlling the first switching tube, the third switching tube and the fifth switching tube of the inverter to be switched to an off state.

And S208, controlling the second switching tube, the fourth switching tube and the sixth switching tube of the inverter to be switched to a closed state.

Through switching first switch tube, third switch tube and fifth switch tube to the off-state, switch second switch tube, fourth switch tube and sixth switch tube to the on-state for second switch tube, fourth switch tube and sixth switch tube short circuit, thereby make the switch tube of dc-to-ac converter switch to the braking state.

Step S209, controlling the current detection device to sample the current of the switching tube, so as to obtain a first sampling current.

In some embodiments, obtaining the first sampled current may be implemented as: controlling the current detection device to sample the current of the second switching tube to obtain a first phase current; controlling the current detection device to sample the current of the fourth switching tube to obtain a second phase current; controlling the current detection device to sample the current of the sixth switching tube to obtain a third phase current; and determining the first phase current, the second phase current and the third phase current as sampling currents.

And step S210, acquiring characteristic parameters of the motor.

Here, the characteristic parameters include stator resistance, direct axis inductance, quadrature axis inductance, and back electromotive force coefficient.

And step S211, determining the two-phase current of the motor under the rotating coordinate system based on the first sampling current.

In step S212, a second rotor speed determined based on the second sampling current is acquired.

Here, the second sampling current is obtained by sampling the current of the switching tube last time by the current detection device.

Step S213, determining a second rotor angle based on the second rotor speed.

And step S214, determining the direct-axis current and the quadrature-axis current of the motor under a rotating coordinate system according to the second rotor angle and the two-phase current.

Step S215, determining the back electromotive force direct axis voltage of the motor according to the second rotor rotating speed, the direct axis current, the stator resistance and the direct axis inductance.

And S216, determining back electromotive force quadrature axis voltage of the motor according to the second rotor rotating speed, the quadrature axis current, the stator resistance and the quadrature axis inductance.

And step S217, determining the counter electromotive force of the motor according to the counter electromotive force direct-axis voltage and the counter electromotive force quadrature-axis voltage.

And step S218, determining the first motor rotating speed according to the counter electromotive force and the counter electromotive force coefficient.

Step S219, performing filtering processing on the first motor rotation speed to obtain a first rotor rotation speed of the motor.

Step S220, determining a first rotor angle based on the first rotor speed.

Step S221, determining whether the first rotor speed reaches a preset threshold.

When the first rotor speed reaches a preset threshold, the method proceeds to step S222 to obtain a duration; when the first rotor speed does not reach the preset threshold, it indicates that the motor is still running, and then the process goes to step S225.

Step S222, obtaining a duration of the first rotor speed reaching a preset threshold.

Step S223, determining whether the duration reaches a preset duration threshold.

When the duration that the first rotor speed reaches the preset threshold reaches the preset duration threshold, indicating that the motor stops running and has reached a stable state, then entering step S224; when the duration of the first rotor reaching the preset threshold is less than the preset duration threshold, it indicates that the motor has stopped running but has not reached a steady state, and then the process goes to step S225.

Step S224, determining that the first rotor speed reaches a brake shutdown end condition.

After it is determined that the first rotor speed reaches the brake-off end condition, the process proceeds to step S226.

And step S225, determining that the first rotor rotating speed does not reach the braking stop ending condition.

In this case, the process returns to step S209, and the current detection device is controlled to sample the current of the switching tube next time.

And step S226, controlling the second switching tube, the fourth switching tube and the sixth switching tube of the inverter to be switched to an off state.

In step S227, it is determined that the motor braking is completed.

According to the motor braking control method provided by the embodiment of the application, when the motor is braked and stopped, the outputs of the three upper bridge arms of the inverter are closed, and the outputs of the three lower bridge arms of the inverter are simultaneously opened, so that the three lower bridge arms of the inverter bridge form a short circuit, a loop is formed among three phases of the motor due to the current generated by the inertia kinetic energy of the motor in operation, and the current is consumed in the coil impedance of the motor, so that the motor is quickly stopped. And in the braking process, a current detection device and a speed observer are started, the rotor rotating speed of the motor is obtained through calculation of the position-free sensor, and when the rotor rotating speed obtained through calculation is zero and lasts for a certain time, the controller determines that the braking and stopping process is finished, so that the accuracy of determining the complete stopping state and time of the motor can be improved. In addition, the brake control method does not need to add an additional brake circuit, so that the cost can be reduced; the motor braking control method provided by the embodiment of the application is applied to the washing machine, so that the cost of the washing machine can be reduced, the accurate control of the washing machine can be realized, and the accuracy of the washing time is ensured.

Next, an exemplary application of the embodiment of the present application in a practical application scenario will be described.

In the related technology, the operation and stop control of the three-phase brushless direct current motor and the permanent magnet synchronous motor is realized by the control of an inverter in a frequency conversion controller, and the stop of the motor can adopt methods such as common stop, emergency stop and brake. The sudden stop and the brake stop can be divided into a brake circuit brake stop and a self-braking stop.

And (4) ordinary shutdown: and stopping controlling the operation of the inverter, namely simultaneously closing the output of all bridge arms of the inverter. When the motor is stopped, the motor can continuously run for a period of time due to inertia, the motor is in a power generation state, phase current of the motor charges a direct current bus through a reverse diode connected in parallel to each IGBT or MOSFET of the inverter, reverse electromotive force generated by the motor is superposed at two ends of an electrolytic capacitor of the bus, if voltage at two ends of the electrolytic capacitor exceeds a tolerance or charging current is too large, the service life and reliability of the electrolytic capacitor are reduced, and failures such as failure and even explosion are caused in serious cases.

Braking and stopping by a braking circuit: if a release resistor and a switch tube are added on the frequency conversion controller, when the inverter closes the output of all bridge arms of the inverter in a conventional mode, a switch of the brake circuit is opened to conduct the release circuit, and the current of the motor is quickly consumed on a passive component (resistor) through the release circuit, so that the inertia kinetic energy of the motor can be released in a short time, and the effect of quickly stopping the motor is achieved.

Self-braking shutdown: the inverter has the advantages that a special braking loop is not arranged in the variable frequency controller, three lower bridge arms of the inverter are simultaneously opened and output when the inverter is stopped, the three lower bridge arms of the inverter bridge form a short circuit state, current generated by inertia kinetic energy of the running motor is consumed in coil impedance of the motor, and the effect of quickly braking and stopping the inverter is achieved. The difficulty of the shutdown is that the shutdown time is not easy to control, and the controller is difficult to obtain the state and the moment whether the motor completely stops.

The embodiment of the application provides a novel speed estimation method for controlling and stopping a direct current motor, which adopts self-braking brake to stop the direct current motor, and detects the speed of the direct current motor in the stopping process in a speed sensor-free mode, so that the accurate stopping of the direct current motor, the speed of the direct current motor, the position of a rotor and other state information can be obtained. Applicable motor types include, but are not limited to: brushless Direct Current motors (BLDCM), surface Permanent Magnet Synchronous Motors (SPMSM), or Interior Permanent Magnet Synchronous Motors (IPMSM).

The embodiment of the application provides a novel speed estimation method for stopping control and stopping process of a direct current motor, when braking and stopping, the output of three upper bridge arms of an inverter is closed, the output of three lower bridge arms of the inverter is simultaneously opened, the three lower bridge arms of the inverter bridge form a short circuit state, current generated by inertia kinetic energy of the motor in operation forms a loop between three phases of the motor, and the current is consumed in coil impedance of the motor, so that the motor is quickly stopped. The speed observer module of the controller program calculates the rotational speed: and in the braking process, a current detector and a speed observer are started, and the rotation speed of the motor is calculated by a position-sensorless algorithm. And when the rotating speed result calculated by the speed observer is zero and lasts for a certain time, the controller determines that the braking and stopping process is finished.

Fig. 3 is a schematic structural diagram of a frequency converter according to an embodiment of the present application, and as shown in fig. 3, the frequency converter 300 includes: a Micro Control Unit (MCU) 301, an inverter 302, an inverter control module 303, a current detection circuit 304, a motor 305 and a power supply 306. The inverter 302 has six power switching tubes (IGBT or MOSFET) S1 to S6, three upper bridge arms and three lower bridge arms constituting three bridges, and each switching element has an anti-parallel diode D1 to D6; the MCU 301 comprises a speed position observer, a rotating speed and angle instruction control unit, a starting control unit, a stopping control unit, a braking control unit and a direct axis current i _d Or quadrature axis current i _q Proportional-Integral (PI) controller, speed controller, space Vector Pulse Width Modulation (SVPWM).

Fig. 4 is a schematic flow chart of an implementation of a dc motor shutdown control method provided in an embodiment of the present application, and as shown in fig. 4, the method includes the following steps:

in step S401, brake shutdown is started.

And step S402, closing three upper bridge arms of the inverter and opening three lower bridge arms of the inverter.

In step S403, control instruction setting.

Setting a rotational speed omega based on a rotational speed command _ref =0, set direct current based on d-q axis voltage control command

Quadrature axis current

Close speed PI Ring, set straight shaft speed

Velocity of quadrature axis

Closing the current loop i _d And i _q The PI controller of (1); and starting a current detection module and a speed and position observer.

In step S404, the current detection circuit samples three-phase currents.

In step S405, a two-phase coordinate current is calculated based on the three-phase current.

In the braking process, the current detection circuit samples three-phase current i _u ，i _v ，i _w The two-phase coordinate current i is obtained by the following equations (10) and (11) _α ，i _β ；

i _α(n) ＝i _u (10)；

Step S406, calculating the direct-axis current and the quadrature-axis current according to the two-phase coordinate current.

The speed position observer calculates the direct-axis current and the quadrature-axis current from the following equations (12) and (13):

i _d ＝i _α *cos(θ _e ′)+i _β *sin(θ _e ′) (12)；

i _q ＝i _β *cos(θ _e ′)-i _α *sin(θ _e ′) (13)；

wherein, theta _e ' is a rotor angle calculated based on the three-phase current sampled last time.

In step S407, the back electromotive voltage in the rotating coordinate system is calculated.

In the present embodiment, the back electromotive force in the rotating coordinate system is calculated by the following equations (14) and (15)Axial voltage E _d And quadrature axis voltage E _q ：

E _d ＝R _s *i _d -ω _e ′*L _d *i _d (14)；

E _q ＝R _s *i _q +ω _e ′*L _q *i _q (15)；

Wherein, ω is _e ' is the rotor speed, R, calculated based on the three-phase current obtained from the last sampling _s Is the motor stator resistance, L _d Is a direct axis inductor, L _q Is a quadrature axis inductance.

In step S408, the back electromotive force is calculated.

In the present embodiment, the back electromotive force E is calculated from the following equation (16) _s ：

And step S409, calculating the rotating speed of the motor.

In the embodiment of the application, the back electromotive force E based on the motor _s Calculating the motor speed omega:

wherein, K _e As the back emf coefficient, is a known motor controller parameter.

And S410, filtering the rotating speed of the motor to obtain the rotating speed of the rotor.

Filtering the signal by a low pass filter LPF to obtain the final rotor rotation speed omega of the observer _e . In the embodiment of the application, LPF (ω) is used to represent filtering processing on the rotation speed of the first motor, and then the rotation speed of the first rotor of the motor is represented as ω _e ＝LPF(ω)。

And step S411, integrating the rotating speed of the rotor and calculating to obtain the rotor angle.

From the rotor speed omega _e The time integral formula (18) of (a) calculates the rotor angle theta _e 。

θ _e ＝∫ω _e dt (18)；

Here, the calculated rotor angle participates in the next sampling calculation.

Step S412, determining whether the rotor speed reaches a preset threshold.

Here, the preset threshold may be set to 0. Brake control module in micro control unit judges omega _e Whether it is equal to 0, when ω is _e If =0, the flow proceeds to step S413; when omega _e If not equal to 0, the process returns to step S404.

In step S413, it is determined whether the duration of the rotor speed reaching the preset threshold reaches the preset duration threshold.

Here, the preset time period threshold is denoted as T _s . The program of the brake control module judges whether the duration T reaches T _s When T is more than or equal to T _s If yes, go to step S414; when T < T _s Then, the process returns to step S404.

And step S414, all bridge arm outputs of the inverter are closed, and the motor braking is finished.

Fig. 5 is a schematic diagram of an experimental test of the dc motor shutdown control method according to the embodiment of the present application, as shown in fig. 5, 501 is a rotation speed, 502 is an estimated rotation speed, 503 is a u-phase current, 504 is a v-phase current, and 505 is a w-phase current. And at the time T1, the motor braking stop is started, and the time T2 determines that the motor braking is finished.

In other embodiments, the back EMF voltage estimation may employ a back EMF observer, a state observer, a synovial observer, a Roeberg observer, or the like to calculate the back EMF direct axis voltage E _d And quadrature axis voltage E _q 。

In other embodiments, the observer calculates the back EMF E _s Available in the stationary coordinate system E _α 、E _β In this case, the above equation (16) is replaced with equation (19):

according to the speed estimation method for the direct current motor stopping control and the stopping process, self-braking is adopted for braking, additional braking components are not needed, and all lower bridge arms of an inverter are controlled to be in short circuit to achieve motor braking; during braking, the speed PI control is closed, and the current controller is closed; during braking, the current detection module and the speed and position observer work, and the control system can obtain the actual speed and the actual rotor position of the motor in the stopping process.

Based on the foregoing embodiments, the present application provides a motor brake control apparatus, where each module included in the apparatus and each unit included in each module may be implemented by a processor in a computer device; of course, the implementation can also be realized through a specific logic circuit; in implementation, the processor may be a Central Processing Unit (CPU), a Microprocessor Unit (MPU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), or the like.

Fig. 6 is a schematic structural diagram of a motor brake control device provided in an embodiment of the present application, where the motor brake control device is applied to a motor brake control apparatus, and as shown in fig. 6, the motor brake control device 600 includes:

the first control module 601 is used for responding to a received braking instruction for controlling the motor to stop and controlling a switching tube of the inverter to be switched to a braking state;

the second control module 602 is configured to control the current detection device to sample the current of the switching tube, so as to obtain a first sampled current;

a first determining module 603 for determining a first rotor speed of the electric machine based on the first sampled current;

a second determination module 604 determines that motor braking is complete if the first rotor speed reaches a brake shutdown end condition.

the first control module 601 is further configured to:

and controlling a second switching tube, a fourth switching tube and a sixth switching tube of the inverter to be switched to a closed state, so that the second switching tube, the fourth switching tube and the sixth switching tube are switched to a braking state in a short circuit mode.

In some embodiments, the motor brake control apparatus 600 may further include:

the initialization module is used for initializing the braking parameters of the motor;

the third control module is used for controlling the first controller of the speed ring of the motor to close;

the fourth control module is used for controlling the second controller of the current loop of the motor to be closed;

the fifth control module is used for controlling the opening of a current detection device of the motor;

and the sixth control module is used for controlling the starting of the speed position observer of the motor.

In some embodiments, the first determining module 603 is further configured to:

determining a back electromotive force of the motor based on the two-phase current, the stator resistance, the direct-axis inductance, and the quadrature-axis inductance;

In some embodiments, the first determining module 603 is further configured to:

determining a direct-axis current and a quadrature-axis current of the motor from the two-phase current;

and determining the counter electromotive force of the motor according to the counter electromotive force direct axis voltage and the counter electromotive force quadrature axis voltage.

In some embodiments, the first determining module 603 is further configured to:

determining a second rotor angle based on the second rotor speed;

In some embodiments, the motor brake control apparatus 600 may further include:

the judging module is used for determining whether the rotating speed of the first rotor reaches a preset threshold value;

the acquisition module is used for acquiring the duration of the first rotor rotating speed reaching a preset threshold value under the condition that the first rotor rotating speed reaches the preset threshold value;

and the third determining module is used for determining that the rotating speed of the first rotor reaches the braking shutdown ending condition under the condition that the duration reaches a preset duration threshold.

In some embodiments, the motor brake control apparatus 600 may further include:

the fourth determining module is used for determining that the first rotor rotating speed does not reach a brake shutdown ending condition under the condition that the first rotor rotating speed does not reach a preset threshold value or the duration does not reach a preset duration threshold value;

and the seventh control module is used for controlling the current detection device to sample the current of the switching tube next time.

In some embodiments, the motor brake control apparatus 600 may further include:

and the eighth control module is used for controlling the second switching tube, the fourth switching tube and the sixth switching tube of the inverter to be switched to a disconnected state.

Here, it should be noted that: the above description of the motor brake control apparatus embodiment is similar to the above description of the method, and has the same advantageous effects as the method embodiment. For technical details not disclosed in the embodiments of the motor brake control device of the present application, a person skilled in the art should understand with reference to the description of the embodiments of the method of the present application.

It should be noted that, in the embodiment of the present application, if the motor braking control method is implemented in the form of a software functional module and is sold or used as a standalone product, the method may also be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the embodiments of the present application may be essentially implemented or portions thereof contributing to the prior art may be embodied in the form of a software product stored in a storage medium, and including several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read Only Memory (ROM), a magnetic disk, or an optical disk. Thus, embodiments of the present application are not limited to any specific combination of hardware and software.

Accordingly, embodiments of the present application provide a computer-readable storage medium, on which a computer program is stored, which when executed by a processor implements the steps in the motor braking control method provided in the above embodiments.

The embodiment of the present application provides a motor brake control apparatus, which is applied to a motor, fig. 7 is a schematic diagram of a composition structure of the motor brake control apparatus provided in the embodiment of the present application, and other exemplary structures of the motor brake control apparatus 700 can be foreseen according to the exemplary structure of the motor brake control apparatus 700 shown in fig. 7, so that the structure described herein should not be considered as a limitation, for example, some components described below may be omitted, or components not described below may be added to adapt to special requirements of some applications.

The motor brake control apparatus 700 shown in fig. 7 includes: a processor 701, at least one communication bus 702, a user interface 703, at least one external communication interface 704 and a memory 705. Wherein the communication bus 702 is configured to enable connective communication between these components. The user interface 703 may comprise a display screen, and the external communication interface 704 may comprise a standard wired interface and a wireless interface, among others. Wherein the processor 701 is configured to execute the program of the motor braking control method stored in the memory to implement the steps in the motor braking control method provided by the above-mentioned embodiments.

The above description of the motor brake control apparatus and storage medium embodiments is similar to the description of the method embodiments above with similar beneficial effects as the method embodiments. For technical details not disclosed in the embodiments of the motor brake control apparatus and the storage medium of the present application, reference is made to the description of the embodiments of the method of the present application for understanding.

It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in the various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application. The above-mentioned serial numbers of the embodiments of the present application are merely for description and do not represent the merits of the embodiments.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one of 8230, and" comprising 8230does not exclude the presence of additional like elements in a process, method, article, or apparatus comprising the element.

In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. The above-described device embodiments are merely illustrative, for example, the division of the unit is only one logical function division, and there may be other division ways in actual implementation, such as: multiple units or components may be combined, or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the coupling, direct coupling or communication connection between the components shown or discussed may be through some interfaces, and the indirect coupling or communication connection between the devices or units may be electrical, mechanical or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units; can be located in one place or distributed on a plurality of network units; some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, all functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may be separately regarded as one unit, or two or more units may be integrated into one unit; the integrated unit may be implemented in the form of hardware, or in the form of hardware plus a software functional unit.

Those of ordinary skill in the art will understand that: all or part of the steps for realizing the method embodiments can be completed by hardware related to program instructions, the program can be stored in a computer readable storage medium, and the program executes the steps comprising the method embodiments when executed; and the aforementioned storage medium includes: a removable storage device, a ROM, a magnetic or optical disk, or other various media that can store program code.

Alternatively, the integrated units described above in the present application may be stored in a computer-readable storage medium if they are implemented in the form of software functional modules and sold or used as independent products. Based on such understanding, the technical solutions of the embodiments of the present application may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a product to perform all or part of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a removable storage device, a ROM, a magnetic or optical disk, or other various media that can store program code.

The above description is only for the embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A motor braking control method, characterized in that the method comprises:

initializing brake parameters of the motor; a first controller for controlling a speed loop of the motor is closed, and a second controller for controlling a current loop of the motor is closed; controlling a current detection device of the motor to be started, and controlling a speed position observer of the motor to be started;

determining that the motor braking is finished under the condition that the rotating speed of the first rotor reaches the braking stop ending condition;

wherein said determining a first rotor speed of the motor based on the first sampled current comprises:

carrying out filtering processing on the rotating speed of the first motor to obtain the first rotor rotating speed of the motor;

wherein the determining a back EMF of the motor based on the two-phase current, the stator resistance, the direct-axis inductance, and the quadrature-axis inductance comprises:

2. The method according to claim 1, wherein the inverter comprises a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube and a sixth switch tube, three upper bridge arms and three lower bridge arms forming three bridges, wherein the first switch tube, the third switch tube and the fifth switch tube form the three upper bridge arms, and the second switch tube, the fourth switch tube and the sixth switch tube form the three lower bridge arms;

3. The method of claim 1, wherein determining a direct-axis current and a quadrature-axis current of the motor from the two-phase currents comprises:

determining a second rotor angle based on the second rotor speed;

4. The method of any of claims 1 to 3, further comprising:

5. The method of claim 4, further comprising:

and controlling the current detection device to sample the current of the switching tube next time.

6. The method of claim 2, further comprising:

and after the fact that the rotating speed of the first rotor reaches the braking stop ending condition is determined, controlling a second switching tube, a fourth switching tube and a sixth switching tube of the inverter to be switched to a disconnected state.

7. A motor brake control apparatus, the apparatus comprising:

the second control module is used for initializing the braking parameters of the motor; a first controller for controlling a speed loop of the motor is closed, and a second controller for controlling a current loop of the motor is closed; controlling a current detection device of the motor to be started, and controlling a speed position observer of the motor to be started; controlling a current detection device to sample the current of the switching tube to obtain a first sampling current;

the second determining module is used for determining that the motor braking is finished under the condition that the rotating speed of the first rotor reaches the braking stop ending condition;

wherein the first determining module, configured to determine a first rotor speed of the motor based on the first sampled current, comprises: acquiring characteristic parameters of the motor, wherein the characteristic parameters comprise stator resistance, direct axis inductance, quadrature axis inductance and back electromotive force coefficient; determining a two-phase current of the motor under a rotating coordinate system based on the first sampling current; determining a back electromotive force of the electric machine based on the two-phase current, the stator resistance, the direct-axis inductance, and the quadrature-axis inductance; determining the rotating speed of a first motor according to the counter electromotive force and the counter electromotive force coefficient; carrying out filtering processing on the rotating speed of the first motor to obtain a first rotor rotating speed of the motor;

wherein the first determination module to determine a back EMF of the motor based on the two-phase current, the stator resistance, the direct axis inductance, and the quadrature axis inductance comprises: acquiring a second rotor rotating speed determined based on a second sampling current, wherein the second sampling current is obtained by sampling the current of the switching tube last time by the current detection device; determining a direct-axis current and a quadrature-axis current of the motor from the two-phase current; determining back electromotive force direct-axis voltage of the motor according to the second rotor rotating speed, the direct-axis current, the stator resistance and the direct-axis inductance; determining back electromotive force quadrature axis voltage of the motor according to the second rotor rotating speed, the quadrature axis current, the stator resistance and the quadrature axis inductance; and determining the counter electromotive force of the motor according to the counter electromotive force direct axis voltage and the counter electromotive force quadrature axis voltage.

8. A motor brake control apparatus, characterized by comprising:

a memory for storing executable instructions;

a processor for implementing the method of any one of claims 1 to 6 when executing executable instructions stored in the memory.

9. A computer readable storage medium having stored thereon executable instructions for causing a processor, when executed, to implement the method of any one of claims 1 to 6.