阅读说明：本技术 电机刹车控制方法、装置及电动工具 (Motor brake control method and device and electric tool ) 是由 不公告发明人 于 2019-09-02 设计创作，主要内容包括：本发明适用于电机控制技术领域,提供了一种电机刹车控制方法、装置及电动工具,该方法包括：实时检测电机的状态；当检测到所述电机在处于转动状态下获取到刹车控制信号时,根据所述刹车控制信号控制用于对所述电机进行刹车的PWM波的占空比逐渐增加,以使控制所述电机逐渐进行刹车,直至所述电机停止转动完成刹车。本发明包括通过在获取到刹车控制信号时,控制用于对电机进行刹车的PWM波的占空比逐渐增加,使得其刹车力度为由小变大,使得刹车柔顺,消除了电动工具在停机时的震动感,改善用户的使用体验。(The invention is suitable for the technical field of motor control, and provides a motor brake control method, a motor brake control device and an electric tool, wherein the method comprises the following steps: detecting the state of the motor in real time; when the motor is detected to acquire a braking control signal in a rotating state, controlling the duty ratio of a PWM wave for braking the motor to gradually increase according to the braking control signal so as to control the motor to gradually brake until the motor stops rotating and brake is completed. The method comprises the steps of controlling the duty ratio of the PWM wave for braking the motor to be gradually increased when the brake control signal is obtained, so that the braking force of the motor is gradually increased, the brake is smooth, the vibration sense of the electric tool during shutdown is eliminated, and the use experience of a user is improved.)

1. A motor brake control method, comprising:

detecting the state of the motor in real time;

when the motor is detected to acquire a braking control signal in a rotating state, controlling the duty ratio of a PWM wave for braking the motor to gradually increase according to the braking control signal so as to control the motor to gradually brake until the motor stops rotating and brake is completed.

2. The motor brake control method of claim 1, wherein the step of controlling the duty ratio of the PWM wave for braking the motor to be gradually increased according to the brake control signal so that the motor is controlled to be gradually braked until the motor stops rotating to complete braking comprises:

according to the brake control signal, a brake switch is started, and the duty ratio of a PWM wave is controlled to gradually increase so as to control the motor to gradually brake, wherein the PWM wave is used for controlling the working state of the brake switch;

and when the motor is detected to stop moving, closing the brake switch to complete braking.

3. The motor brake control method of claim 1, further comprising:

detecting the discharge voltage and the reverse charging current of the battery pack in the current braking state in real time;

and controlling the speed of increasing the duty ratio of the PWM wave within the range of a preset voltage threshold and a preset current threshold according to the discharging voltage and the reverse charging current so as to enable the discharging voltage to be smaller than the preset voltage threshold and the reverse charging current to be smaller than the preset current threshold in a braking state.

4. The motor brake control method of claim 3, further comprising:

when the discharge voltage is detected to be larger than the preset voltage threshold, controlling to reduce the duty ratio of PWM waves until the discharge voltage is smaller than the preset voltage threshold;

and when the discharge voltage is detected to be smaller than the preset voltage threshold, controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset voltage threshold until the motor stops rotating.

5. The motor brake control method of claim 3, further comprising:

when the reverse charging current is detected to be larger than the preset current threshold, controlling to reduce the duty ratio of a PWM wave until the reverse charging current is smaller than the preset current threshold;

and when the reverse charging current is detected to be smaller than the preset current threshold, controlling the speed of increasing the duty ratio of the PWM wave within the preset current threshold range until the motor stops rotating.

6. The motor brake control method of claim 1, wherein the brake control signal includes a braking force, and the step of controlling the duty ratio of the PWM wave for braking the motor to be gradually increased according to the brake control signal so that the motor is controlled to gradually brake comprises:

determining a target duty ratio value corresponding to the braking force according to the braking force;

and according to the target duty ratio value, controlling the duty ratio of a PWM wave for braking the motor to be gradually increased to the target duty ratio value from a first duty ratio value so as to control the motor to gradually brake to the braking force until the motor stops rotating and braking is finished.

7. The motor brake control method of claim 1, wherein the brake control signal includes a braking time, and the step of controlling the duty ratio of the PWM wave for braking the motor to be gradually increased according to the brake control signal so that the motor is controlled to gradually brake comprises:

according to the braking time, a first target change rate that the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to a second duty ratio value is determined;

and gradually increasing the duty ratio of the PWM wave from the first duty ratio value to the second duty ratio value at the first target change rate so as to control the motor to gradually brake within the braking time until the motor stops completing braking.

8. The motor brake control method of claim 1, wherein the brake control signal includes a braking time and a braking force, and the step of controlling the duty ratio of the PWM wave for braking the motor to be gradually increased according to the brake control signal so that the motor is controlled to gradually brake comprises:

determining a target duty ratio value corresponding to the braking force according to the braking force;

according to the braking time and the target duty ratio value, a second target change rate is determined, wherein the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to the target duty ratio value;

and controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the target duty ratio value at the second target change rate, so that the motor is controlled to be gradually braked to the braking force within the braking time until the motor stops completing braking.

9. The motor brake control method of claim 1, wherein the step of detecting the state of the motor in real time comprises:

acquiring information acquired by a position sensor or a motor parameter acquisition module in real time;

and determining the state of the motor according to the information acquired by the position sensor or the motor parameter acquisition module in real time.

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

the first detection module is used for detecting the state of the motor in real time;

and the first control module is used for controlling the duty ratio of PWM waves used for braking the motor to be gradually increased according to the brake control signal when the motor is detected to acquire the brake control signal in a rotating state, so that the motor is controlled to gradually brake until the motor stops rotating to complete braking.

11. The motor brake control of claim 10, wherein the first control module comprises:

the first control unit is used for starting a brake switch according to the brake control signal and controlling the duty ratio of a PWM wave to gradually increase so as to control the motor to gradually brake, wherein the PWM wave is used for controlling the working state of the brake switch;

and the second control unit is used for closing the brake switch to finish braking when the motor is detected to stop moving.

12. The motor brake control apparatus of claim 10, further comprising:

the second detection module is used for detecting the discharge voltage and the reverse charging current of the battery pack in the current braking state in real time;

and the second control module is used for controlling the speed of increasing the duty ratio of the PWM wave within the range of a preset voltage threshold and a preset current threshold according to the discharging voltage and the reverse charging current so as to enable the discharging voltage to be smaller than the preset voltage threshold and the reverse charging current to be smaller than the preset current threshold in a braking state.

13. The motor brake control apparatus of claim 12, further comprising:

the third control module is used for controlling and reducing the duty ratio of the PWM wave when the second detection module detects that the discharge voltage is larger than the preset voltage threshold value until the discharge voltage is smaller than the preset voltage threshold value;

and the fourth control module is used for controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset voltage threshold value until the motor stops rotating after the second detection module detects that the discharge voltage is smaller than the preset voltage threshold value.

14. The motor brake control apparatus of claim 12, further comprising:

the fifth control module is used for controlling and reducing the duty ratio of the PWM wave when the second detection module detects that the reverse charging current is larger than the preset current threshold value until the reverse charging current is smaller than the preset current threshold value;

and the sixth control module is used for controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset current threshold value until the motor stops rotating after the second detection module detects that the reverse charging current is smaller than the preset current threshold value.

15. The motor brake control apparatus of claim 10, wherein the brake control signal includes a brake force, and the first control module includes:

the first determining unit is used for determining a target duty ratio value corresponding to the braking force according to the braking force;

and the third control unit is used for controlling the duty ratio of the PWM wave for braking the motor to be gradually increased from the first duty ratio value to the target duty ratio value according to the target duty ratio value so as to control the motor to be gradually braked to the braking force until the motor stops rotating and braking is finished.

16. The motor brake control device of claim 10, wherein the brake control signal includes a brake time, and the first control module includes:

a second determining unit, configured to determine, according to the braking time, a first target change rate at which a duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio to a second duty ratio;

and the fourth control unit is used for controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the second duty ratio value at the first target change rate so as to control the motor to gradually brake within the braking time until the motor stops completing braking.

17. The motor brake control apparatus of claim 10, wherein the brake control signal includes a braking time and a braking force, and the first control module includes:

the third determining unit is used for determining a target duty ratio value corresponding to the braking force according to the braking force;

a fourth determining unit, configured to determine, according to the braking time and the target duty ratio value, a second target change rate at which the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to the target duty ratio value;

and the fifth control unit is used for controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the target duty ratio value at the second target change rate so as to control the motor to be gradually braked to the braking force within the braking time until the motor stops finishing braking.

18. The motor brake control of claim 10, wherein the first detection module comprises:

the acquisition unit is used for acquiring information acquired by the position sensor or the motor parameter acquisition module in real time;

and the fifth determining unit is used for determining the state of the motor according to the information acquired by the position sensor or the motor parameter acquisition module in real time.

19. An electric tool, characterized in that the electric tool comprises a motor brake control device as described in any one of 10-18.

Technical Field

The invention belongs to the technical field of motor control, and particularly relates to a motor brake control method and device and an electric tool.

Background

The electric tools are generally driven by a motor to operate, some electric tools need to be capable of rapidly stopping the motor after a working switch is released so as to avoid potential safety hazards, such as circular saws, angle grinders, chain saws and the like.

In the prior art, the current general motor braking method is as follows: the controller is direct to open three-phase power switch of putting the bridge or three-phase power switch of putting the bridge totally under with, produces the brake braking effect, but brake time and dynamics are not adjustable, can produce strong vibrations to some electric tool and feel, and it is not good to use experience.

Disclosure of Invention

The embodiment of the invention aims to provide a motor brake control method, and aims to solve the technical problem that the existing electric tool can generate strong vibration feeling when being stopped.

The embodiment of the invention is realized in such a way that a motor brake control method comprises the following steps:

detecting the state of the motor in real time;

when the motor is detected to acquire a braking control signal in a rotating state, controlling the duty ratio of a PWM wave for braking the motor to gradually increase according to the braking control signal so as to control the motor to gradually brake until the motor stops rotating and brake is completed.

Furthermore, the step of controlling the duty ratio of the PWM wave for braking the motor according to the braking control signal to gradually increase so as to gradually control the motor to gradually brake until the motor stops rotating to complete braking includes:

according to the brake control signal, a brake switch is started, and the duty ratio of a PWM wave is controlled to gradually increase so as to control the motor to gradually brake, wherein the PWM wave is used for controlling the working state of the brake switch;

and when the motor is detected to stop moving, closing the brake switch to complete braking.

Still further, the method further comprises:

detecting the discharge voltage and the reverse charging current of the battery pack in the current braking state in real time;

and controlling the speed of increasing the duty ratio of the PWM wave within the range of a preset voltage threshold and a preset current threshold according to the discharging voltage and the reverse charging current so as to enable the discharging voltage to be smaller than the preset voltage threshold and the reverse charging current to be smaller than the preset current threshold in a braking state.

Still further, the method further comprises:

when the discharge voltage is detected to be larger than the preset voltage threshold, controlling to reduce the duty ratio of PWM waves until the discharge voltage is smaller than the preset voltage threshold;

and when the discharge voltage is detected to be smaller than the preset voltage threshold, controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset voltage threshold until the motor stops rotating.

Still further, the method further comprises:

when the reverse charging current is detected to be larger than the preset current threshold, controlling to reduce the duty ratio of a PWM wave until the reverse charging current is smaller than the preset current threshold;

and when the reverse charging current is detected to be smaller than the preset current threshold, controlling the speed of increasing the duty ratio of the PWM wave within the preset current threshold range until the motor stops rotating.

Furthermore, the brake control signal includes a brake force, and the step of controlling the motor to gradually brake includes, according to the control signal, gradually increasing a duty ratio of a PWM wave for braking the motor:

determining a target duty ratio value corresponding to the braking force according to the braking force;

and according to the target duty ratio value, controlling the duty ratio of a PWM wave for braking the motor to be gradually increased to the target duty ratio value from a first duty ratio value so as to control the motor to gradually brake to the braking force until the motor stops rotating and braking is finished.

Furthermore, the brake control signal includes a brake time, and the step of controlling the motor to gradually brake by gradually increasing the duty ratio of the PWM wave for braking the motor according to the brake control signal includes:

according to the braking time, a first target change rate that the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to a second duty ratio value is determined;

and gradually increasing the duty ratio of the PWM wave from the first duty ratio value to the second duty ratio value at the first target change rate so as to control the motor to gradually brake within the braking time until the motor stops completing braking.

Furthermore, the brake control signal includes a brake time and a brake force, and the step of controlling the motor to gradually brake includes:

determining a target duty ratio value corresponding to the braking force according to the braking force;

according to the braking time and the target duty ratio value, a second target change rate is determined, wherein the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to the target duty ratio value;

and controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the target duty ratio value at the second target change rate, so that the motor is controlled to be gradually braked to the braking force within the braking time until the motor stops completing braking.

Further, the step of detecting the state of the motor in real time includes:

acquiring information acquired by a position sensor or a motor parameter acquisition module in real time;

and determining the state of the motor according to the information acquired by the position sensor or the motor parameter acquisition module in real time.

In addition, an embodiment of the present invention further provides a motor brake control device, where the device includes:

the first detection module is used for detecting the state of the motor in real time;

and the first control module is used for controlling the duty ratio of PWM waves used for braking the motor to be gradually increased according to the brake control signal when the motor is detected to acquire the brake control signal in a rotating state, so that the motor is controlled to gradually brake until the motor stops rotating to complete braking.

In addition, the embodiment of the invention also provides an electric tool, and the electric tool comprises the motor brake control device.

According to the motor brake control method provided by the embodiment of the invention, when the brake control signal is obtained, the duty ratio of the PWM wave for braking the motor is controlled to be gradually increased, so that the braking force is changed from small to large, the brake is smooth, the vibration sense of the electric tool during shutdown is eliminated, and the use experience of a user is improved.

Drawings

Fig. 1 is a schematic flow chart of a motor brake control method according to an embodiment of the present invention;

fig. 2 is a schematic flow chart of a motor brake control method according to a second embodiment of the present invention;

FIG. 3 is a circuit diagram of a position sensor according to an embodiment of the present invention;

fig. 4 is a structural diagram of a PWM control circuit according to an embodiment of the present invention;

fig. 5 is a circuit structure diagram of a motor controller according to an embodiment of the present invention;

fig. 6 is a structural diagram of a back electromotive force detection circuit according to an embodiment of the present invention;

fig. 7 is a structural diagram of a discharge voltage detection circuit of a battery pack according to an embodiment of the present invention;

fig. 8 is a structural diagram of a reverse charging current detection circuit according to an embodiment of the present invention;

fig. 9 is a block diagram of a motor brake control device according to a third embodiment of the present invention;

fig. 10 is a schematic block diagram of an electric power tool according to a fourth embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the present invention, unless otherwise expressly specified 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 connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention provides a motor brake control method, a device and an electric tool, aiming at the technical problems that in the prior art, a three-phase lower bridge power switch or a three-phase upper bridge power switch is directly and completely opened to generate a brake braking effect on a motor, but the brake time and the brake force are not adjustable, strong vibration feeling can be generated on some electric tools, and the use experience is not good.

Example one

Referring to fig. 1, which is a schematic flow chart of a motor brake control method according to an embodiment of the present invention, which may be applied to a motor brake control device, for example, the motor brake control device may be a motor controller, and the motor brake control device may be implemented by software and/or hardware, and the method includes steps S01 to S02:

step S01, the state of the motor is detected in real time.

In particular, the state of the motor, which may include a rotating state and a stopped state, may be detected by providing a state sensor, monitoring electrical parameters (e.g., phase current, back electromotive force, etc.) of an operating circuit of the motor, or setting a program to automatically feed back the current state of the motor.

And step S02, when the motor is detected to acquire a brake control signal in a rotating state, controlling the duty ratio of PWM waves for braking the motor to be gradually increased according to the brake control signal so as to control the motor to gradually brake until the motor stops rotating and brake is completed.

It can be understood that when the brake control signal is received, if the motor is in a rotating state, it is determined that the user needs to brake the motor, and the motor controller sends a brake PWM wave to the motor to control the motor to brake through the PWM wave.

The PWM wave is a pulse width modulation wave, that is, a pulse waveform with a variable duty ratio. The duty ratio of the PWM wave refers to the proportion of the high level in the whole period in a pulse period, when the duty ratio of the PWM wave is gradually increased, the proportion of the high level in the PWM wave is gradually increased, the pulse width is gradually increased, so that a brake switch (a three-phase lower bridge power switch and/or a three-phase upper bridge power switch) of the motor is gradually opened until the switch is opened to a set or rated maximum opening degree, the brake voltage applied to the motor is gradually increased, and the brake force is gradually increased from small to small.

In some alternative embodiments of the present invention, the duty ratio of the PWM wave may be gradually increased in a constant manner, or the duty ratio of the PWM wave may be gradually increased in a variable manner, such as a gradual front-to-back approach, or a gradual middle-to-middle approach. In addition, the initial duty ratio and the maximum duty ratio of the PWM wave can adopt preset values, or adopt system default values, or carry out self-adaptive adjustment according to the actual brake control state.

To sum up, according to the motor brake control method in the embodiment, when the brake control signal is acquired, the duty ratio of the PWM wave for braking the motor is controlled to be gradually increased, so that the braking force is gradually increased, the brake is flexible, the vibration of the electric tool during shutdown is eliminated, and the use experience of the user is improved.

Example two

Referring to fig. 2, it is a schematic flow chart of a motor brake control method according to a second embodiment of the present invention, which can be applied to a motor brake control device, for example, the motor brake control device may be a motor controller, the motor brake control device may be implemented by software and/or hardware, and the method includes steps S11 to S15.

And step S11, acquiring information acquired by the position sensor or the motor parameter acquisition module in real time.

And step S12, determining the state of the motor according to the information acquired by the position sensor or the motor parameter acquisition module in real time.

In some alternative embodiments, for some motors with hall sensors, the hall sensors can be used as the position sensors to directly sense the working state of the motor by using the hall sensors; alternatively, the position sensor may be disposed on the motor stator or other position capable of monitoring the position of the motor rotor, so as to determine the operating state of the motor by directly acquiring the position of the motor rotor. Illustratively, as shown in fig. 3, a circuit structure diagram of the position sensor is shown, which includes a sensing chip CN3 and three signal input pins (Hall U, Hall V and Hall W, respectively), wherein pins 2, 3 and 4 of the sensing chip CN3 are connected to the Hall U, Hall V and Hall W through a protection resistor (R68, R69 and R70), respectively, and the Hall U, Hall V and Hall W are connected to corresponding pins of a motor controller (as shown in fig. 5), respectively, and the motor controller senses an operating state, such as an operating state or a stop state, of the motor according to a parameter fed back by the position sensor.

In addition, it should be noted that the information collected by the motor parameter collecting module may be, but is not limited to, a phase current or a back electromotive force of the motor, so as to determine a state of the motor, such as an operating state or a stop state, by collecting the phase current or the back electromotive force of the motor, where the motor parameter collecting module may specifically be an electrical signal collecting device, such as an ammeter, a sensor, or may also be an electrical signal collecting circuit, such as an electromotive force collecting circuit. The back electromotive force is an electromotive force generated against a tendency of a change in current. When the motor runs, the counter electromotive force of the motor has a variable value, and when the motor stops running, the counter electromotive force of the motor is at rest.

And step S13, when the motor is detected to acquire a brake control signal in a rotating state, controlling the duty ratio of PWM waves for braking the motor to be gradually increased according to the brake control signal so as to control the motor to gradually brake until the motor stops rotating and brake is completed.

In specific implementation, the step S13 can be implemented as follows:

according to the brake control signal, a brake switch is started, and the duty ratio of a PWM wave is controlled to gradually increase so as to control the motor to gradually brake, wherein the PWM wave is used for controlling the working state of the brake switch;

and when the motor is detected to stop moving, closing the brake switch to complete braking.

It should be noted that, in an embodiment of the present invention, the motor is connected to an external battery pack, energy required by the motor to operate is provided by the battery pack, at this time, when the motor operates, the battery pack outputs a discharge voltage to the motor, and when the motor brakes, the battery pack is reversely charged. It is understood that in other embodiments of the present invention, the motor may also be connected to an energy storage capacitor with a large capacitance, or directly connected to an external power supply (such as commercial power, etc.), which is configured according to actual needs, and is not limited herein.

For example, referring to fig. 4, a PWM control circuit of a motor is shown, which includes three PWM control sub-circuits connected in parallel and respectively used for controlling the motor U, V and the W phase, the circuit structures of the three PWM control sub-circuits are completely the same, and a corresponding description is given by using one of the PWM control sub-circuits for controlling the U phase. Specifically, the PWM control sub-circuit for controlling the U-phase includes an UP-bridge input UPH and a down-bridge input UPL, control chip DIP8, upper bridge power switch (MOS pipe Q8), lower bridge power switch (MOS pipe Q10) and output terminal UU1, upper bridge input end UPH and lower bridge input end UPL are respectively connected with corresponding pins of a motor controller (shown in figure 5), pins 2 and 3 of control chip DIP8 are respectively connected with upper bridge input end UPH and lower bridge input end UPL, and the D pole of MOS pipe Q8 is connected with battery pack power supply end V_busThe G pole of MOS pipe Q8 is connected with pin 7 of control chip DIP8, and output UU1 is connected to the S pole of MOS pipe Q8, and output UU1 is connected with the U of motor and is connected mutually the wiring terminal, and output UU1 is connected to the D pole of MOS pipe Q10, and the G pole of MOS pipe Q10 is connected with pin 5 of control chip DIP8, and the S pole of MOS pipe Q10 is ground connection. The output terminals VV1 and WW1 of the other two PWM control sub-circuits are connected to the V-phase and W-phase terminal terminals of the motor, respectively. In other embodiments, the upper bridge power switch and the lower bridge power switch may use an IGBT switch or the like in addition to the MOS transistor.

As a control mode, when receiving a brake control signal, the motor controller may input a PWM wave to the corresponding control chip DIP8 through the upper bridge input terminal UPH, so that the control chip DIP8 turns on (i.e., turns on) the upper bridge power switch (MOS transistor Q8), and the battery pack supply terminal V is enabled to supply a power supply voltage to the battery pack_busA U phase that can be input to the motor via output UU 1; meanwhile, a PWM wave can be input to the corresponding control chip DIP8 through the lower bridge input VPL, so that the control chip DIP8 turns on (i.e., turns on) the lower bridge power switch (MOS transistor Q15), so that a current can be output from the V phase of the motor and is output back to the PWM control circuit through the output VV1, and since the MOS transistor Q15 is already turned on, the output VV1 is grounded at this time, thereby forming a loop to brake the motor; according to the method, the duty ratio of the PWM wave is controlled to be gradually increased, so that the upper bridge power switch and/or the lower bridge power switch are/is gradually opened, the braking voltage input to the motor is also gradually increased, the braking force is gradually increased from small to large, and the brake is smooth. In other alternative embodiments, the motor controller may input the PWM modulation wave to the corresponding control chip DIP8 through any upper bridge input terminal and any lower bridge input terminal, so as to supply the battery pack with the power terminal V from other circuits_busInput to the motor.

Further, the back electromotive force detection circuit shown in fig. 6 may be utilized to monitor the back electromotive force of the motor, so as to determine the operating state of the motor according to the back electromotive force of the motor, specifically, the circuit shown in fig. 6 includes three signal output pins, i.e., U _ Phase, V _ Phase and D _ Phase, and further includes three signal input pins, i.e., drive a, drive b and drive c, the three signal output pins are connected in series with the three signal input pins one-to-one, and two protection resistors (R81-R86) are connected in series therebetween, the three signal output pins, i.e., U _ Phase, V _ Phase and D _ Phase, are respectively connected with corresponding pins of the motor controller in fig. 5, and the three signal input pins, i.e., drive a, drive b and drive c, are respectively connected with the output terminals UU1, VV1 and WW1 in fig. 4, so as to input the Phase voltages of the motor to the motor controller, thereby obtaining the back electromotive force of the motor.

And step S14, detecting the discharging voltage and the reverse charging current of the battery pack in the current braking state in real time.

It should be noted that, when the motor is controlled to perform braking, the battery pack is charged based on the motor energy recovery principle to form a reverse charging voltage and a reverse charging current, so as to implement energy regeneration. The faster the motor speed, the greater the reverse charging current, and in order to protect the battery pack and the circuit, it is generally necessary to ensure that the reverse charging current is within a preset range. Meanwhile, when the upper and lower bridge power switches are continuously opened, the power is input to the power supply end V of the battery pack of the motor_busThe larger the discharge voltage of the battery pack is, the larger the voltage applied to the upper and lower bridge power switches is, and it is necessary to ensure that the discharge voltage of the battery pack is within a preset range in order to protect the upper and lower bridge power switches.

Step S15, controlling the rate of increasing the duty ratio of the PWM wave within a preset voltage threshold and a preset current threshold according to the discharging voltage and the reverse charging current, so that the discharging voltage is smaller than the preset voltage threshold and the reverse charging current is smaller than the preset current threshold in the braking state.

Specifically, in order to ensure that the discharge voltage of the battery pack is within the set range, the method of controlling the rate of increasing the duty ratio of the PWM wave within the preset voltage threshold and the preset current threshold may be specifically implemented according to the following steps:

when the discharge voltage is detected to be larger than the preset voltage threshold, controlling to reduce the duty ratio of PWM waves until the discharge voltage is smaller than the preset voltage threshold;

and when the discharge voltage is detected to be smaller than the preset voltage threshold, controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset voltage threshold until the motor stops rotating.

The whole process is that when the discharge voltage of the battery pack is larger than the preset voltage threshold, the duty ratio of the PWM wave is reduced so as to reduce the opening degree of the upper and lower bridge power switches and further play a role in reducing the discharge voltage of the battery pack. And when the discharge voltage of the battery pack is detected to be smaller than the preset voltage threshold, continuously increasing the duty ratio of the PWM wave, and increasing the duty ratio increasing speed so as to shorten the braking time of the motor as much as possible.

In specific implementation, as one implementation, the discharge voltage V of the battery pack can be detected by the circuit shown in fig. 7_{bus_}AD, in the figure, the discharge voltage VCC of the battery pack is grounded via voltage dividing resistors R22 and R17 in order, and V of the motor controller in fig. 5_{bus_}The AD pin is connected with a connection point between the voltage dividing resistors R22 and R17 to input the voltage of the voltage dividing resistor R17 to the motor controller, thereby indirectly obtaining the discharge voltage VCC of the battery pack.

Specifically, in order to ensure that the reverse charging current of the battery pack is within a set range, the method of controlling the rate of increasing the duty ratio of the PWM wave within the preset voltage threshold and the preset current threshold may be implemented as follows:

when the reverse charging current is detected to be larger than the preset current threshold, controlling to reduce the duty ratio of a PWM wave until the reverse charging current is smaller than the preset current threshold;

and when the reverse charging current is detected to be smaller than the preset current threshold, controlling the speed of increasing the duty ratio of the PWM wave within the preset current threshold range until the motor stops rotating.

The whole process is that when the reverse charging current is larger than the preset current threshold value, the duty ratio of the PWM wave is reduced to reduce the opening degree of the upper and lower bridge power switches, so that the braking force is reduced, and the reverse charging current is reduced. And when the reverse charging current is detected to be smaller than the preset voltage threshold, continuously increasing the duty ratio of the PWM wave, and increasing the duty ratio increasing speed so as to shorten the braking time of the motor as much as possible.

In specific implementation, as an implementation manner, the reverse charging current may be detected by the circuit shown in fig. 8, where the circuit shown in fig. 8 includes an operational amplifier LM258A, an input terminal CurrentAD + of the operational amplifier LM258A is connected to a corresponding reverse charging voltage collecting node on the PWM control circuit in fig. 4, and an output terminal of the operational amplifier LM258A is connected to a corresponding pin of the motor controller in fig. 5, so as to amplify the collected current signal and input the amplified current signal to the motor controller, thereby obtaining the reverse charging current.

Further, in some optional embodiments of the present invention, when the braking control signal includes a braking force, the step of controlling the motor to gradually brake may be specifically implemented as follows:

determining a target duty ratio value corresponding to the braking force according to the braking force;

and according to the target duty ratio value, controlling the duty ratio of a PWM wave for braking the motor to be gradually increased to the target duty ratio value from a first duty ratio value so as to control the motor to gradually brake to the braking force until the motor stops rotating and braking is finished.

The braking force can be preset by a user, or the braking force actually input by the user (such as the braking force obtained by stepping depth conversion according to a brake pedal), the maximum braking force which the user wants to give to the motor when braking the motor is indicated, a target duty ratio value is obtained by converting the braking force into a duty ratio value of a corresponding PWM wave, and then the duty ratio of the PWM wave is controlled to be gradually increased to the target duty ratio value from a first duty ratio value (initial value) so as to gradually brake the motor to the braking force.

Further, in some optional embodiments of the present invention, when the braking control signal includes a braking time, the step of controlling the PWM wave for braking the motor according to the braking control signal to gradually increase the duty ratio of the PWM wave for gradually braking the motor may be specifically implemented as follows:

according to the braking time, a first target change rate that the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to a second duty ratio value is determined;

and gradually increasing the duty ratio of the PWM wave from the first duty ratio value to the second duty ratio value at the first target change rate so as to control the motor to gradually brake within the braking time until the motor stops completing braking.

The braking time can be preset by a user, namely the time spent by the user for expecting the motor to be completely braked when the motor is braked, the change rate of the duty ratio of the PWM wave is determined through the braking time, and the duty ratio of the PWM wave is controlled to be gradually increased from the first duty ratio value to the second duty ratio value at the change rate so as to complete the braking of the motor in the braking time.

Further, in some optional embodiments of the present invention, when the braking control signal includes a braking time and a braking force, the step of controlling the motor to gradually brake may be specifically implemented as follows:

determining a target duty ratio value corresponding to the braking force according to the braking force;

according to the braking time and the target duty ratio value, a second target change rate is determined, wherein the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to the target duty ratio value;

and controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the target duty ratio value at the second target change rate, so that the motor is controlled to be gradually braked to the braking force within the braking time until the motor stops completing braking.

EXAMPLE III

Another aspect of the present invention further provides a motor brake control device, please refer to fig. 9, which is a schematic block diagram of a motor brake control device according to a third embodiment of the present invention, and the motor brake control device can be applied to a motor brake control device, for example, the motor brake control device can be a motor controller, the motor brake control device can be implemented by software and/or hardware, and the motor brake control device 10 includes:

the first detection module 11 is used for detecting the state of the motor in real time;

the first control module 12 is configured to, when it is detected that the motor acquires a brake control signal in a rotating state, control a duty ratio of a PWM wave used for braking the motor to gradually increase according to the brake control signal, so as to control the motor to gradually brake until the motor stops rotating and braking is completed.

In specific implementation, the state of the motor can be detected by setting a state sensor, monitoring an electrical parameter of a working circuit of the motor, or setting a program to enable the motor to automatically feed back the current state, and the state of the motor can include a rotating state and a stopping state.

It can be understood that when the brake control signal is received, if the motor is in a rotating state, it is determined that the user needs to brake the motor, and the motor controller sends a brake PWM wave to the motor to control the motor to brake through the PWM wave.

The PWM wave is a pulse width modulation wave, that is, a pulse waveform with a variable duty ratio. The duty ratio of the PWM wave refers to the proportion of the high level in the whole period in a pulse period, when the duty ratio of the PWM wave is gradually increased, the proportion of the high level in the PWM wave is gradually increased, the pulse width is gradually increased, so that a brake switch (a three-phase lower bridge power switch and/or a three-phase upper bridge power switch) of the motor is gradually opened until the switch is opened to a set or rated maximum opening degree, the brake voltage applied to the motor is gradually increased, and the brake force is gradually increased from small to small.

In some alternative embodiments of the present invention, the duty ratio of the PWM wave may be gradually increased in a constant manner, or the duty ratio of the PWM wave may be gradually increased in a variable manner, such as a gradual front-to-back approach, or a gradual middle-to-middle approach. In addition, the initial duty ratio and the maximum duty ratio of the PWM wave can adopt preset values, or adopt system default values, or carry out self-adaptive adjustment according to the actual brake control state.

To sum up, motor brake control device 10 in the middle of this embodiment through when acquireing brake control signal, controls the duty cycle that is used for carrying out the PWM ripples that brakes to the motor and increases gradually for its brake dynamics is by little grow, makes the brake gentle and agreeable, has eliminated the vibration sense of electric tool when shutting down, improves user's use and experiences.

Further, in some optional embodiments of the present invention, the first control module 11 may include:

the first control unit is used for starting a brake switch according to the brake control signal and controlling the duty ratio of a PWM wave to gradually increase so as to control the motor to gradually brake, wherein the PWM wave is used for controlling the working state of the brake switch;

and the second control unit is used for closing the brake switch to finish braking when the motor is detected to stop moving.

Further, in some optional embodiments of the present invention, the apparatus may further include:

the second detection module is used for detecting the discharge voltage and the reverse charging current of the battery pack in the current braking state in real time;

and the second control module is used for controlling the speed of increasing the duty ratio of the PWM wave within the range of a preset voltage threshold and a preset current threshold according to the discharging voltage and the reverse charging current so as to enable the discharging voltage to be smaller than the preset voltage threshold and the reverse charging current to be smaller than the preset current threshold in a braking state.

Further, in some optional embodiments of the present invention, the apparatus may further include:

the third control module is used for controlling and reducing the duty ratio of the PWM wave when the second detection module detects that the discharge voltage is larger than the preset voltage threshold value until the discharge voltage is smaller than the preset voltage threshold value;

and the fourth control module is used for controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset voltage threshold value until the motor stops rotating after the second detection module detects that the discharge voltage is smaller than the preset voltage threshold value.

Further, in some optional embodiments of the present invention, the apparatus may further include:

the fifth control module is used for controlling and reducing the duty ratio of the PWM wave when the second detection module detects that the reverse charging current is larger than the preset current threshold value until the reverse charging current is smaller than the preset current threshold value;

and the sixth control module is used for controlling the speed of increasing the duty ratio of the PWM wave within the range of the preset current threshold value until the motor stops rotating after the second detection module detects that the reverse charging current is smaller than the preset current threshold value.

Further, in some optional embodiments of the present invention, when the brake control signal includes a braking force, the first control module 12 may include:

the first determining unit is used for determining a target duty ratio value corresponding to the braking force according to the braking force;

and the third control unit is used for controlling the duty ratio of the PWM wave for braking the motor to be gradually increased from the first duty ratio value to the target duty ratio value according to the target duty ratio value so as to control the motor to be gradually braked to the braking force until the motor stops rotating and braking is finished.

Further, in some optional embodiments of the present invention, when the braking control signal includes a braking time, the first control module 12 may include:

a second determining unit, configured to determine, according to the braking time, a first target change rate at which a duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio to a second duty ratio;

and the fourth control unit is used for controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the second duty ratio value at the first target change rate so as to control the motor to gradually brake within the braking time until the motor stops completing braking.

Further, in some optional embodiments of the present invention, when the braking control signal includes braking time and braking force, the first control module 12 may include:

the third determining unit is used for determining a target duty ratio value corresponding to the braking force according to the braking force;

a fourth determining unit, configured to determine, according to the braking time and the target duty ratio value, a second target change rate at which the duty ratio of a PWM wave for braking the motor is gradually increased from a first duty ratio value to the target duty ratio value;

and the fifth control unit is used for controlling the duty ratio of the PWM wave to be gradually increased from the first duty ratio value to the target duty ratio value at the second target change rate so as to control the motor to be gradually braked to the braking force within the braking time until the motor stops finishing braking.

Further, in some optional embodiments of the present invention, the first detecting module 11 includes:

the acquisition unit is used for acquiring information acquired by the position sensor or the motor parameter acquisition module in real time;

and the fifth determining unit is used for determining the state of the motor according to the information acquired by the position sensor or the motor parameter acquisition module in real time.

The functions or operation steps of the modules and units when executed are substantially the same as those of the method embodiments, and are not described herein again.

Example four

Referring to fig. 10, a module structure of an electric tool according to a fourth embodiment of the present invention is shown, including a motor 20, a motor brake control device 10 for controlling the motor 20, and a battery pack 30 connected to the motor 20, where the motor brake control device 10 is the motor brake control device according to any of the embodiments.

In other embodiments, the electric tool may further include a memory and a computer program stored in the memory and executable on the processor, and when the motor brake control device 10 executes the computer program, the motor brake control method according to any of the above embodiments is implemented.

To sum up, electric tool among the embodiment through when acquireing brake control signal, the duty cycle that control is used for carrying out the PWM ripples of braking to the motor increases gradually for its brake dynamics is by little grow, makes the brake gentle and agreeable, has eliminated electric tool's vibrations sense when shutting down, improves user's use and experiences.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.