CN113949227A

CN113949227A - Electric tool and control method thereof

Info

Publication number: CN113949227A
Application number: CN202010685895.2A
Authority: CN
Inventors: 戴伯凯; 刘伟嘉
Original assignee: Mobiletron Electronics Co Ltd
Current assignee: Mobiletron Electronics Co Ltd
Priority date: 2020-07-16
Filing date: 2020-07-16
Publication date: 2022-01-18
Anticipated expiration: 2040-07-16
Also published as: CN113949227B

Abstract

An electric tool comprises a motor, a first circuit board and a second circuit board, wherein the first circuit board is provided with a first control device which is electrically connected with the motor; the second circuit board is electrically connected with the first circuit board through a transmission line group, and the transmission line group comprises a command transmission line; the second circuit board is provided with a second control device. The control method of the electric tool comprises the following steps: different pulse signal frequencies of the pulse width modulation signal generated by the second control device represent different rotation modes, and the pulse width modulation signal is transmitted through the command transmission line, and the pulse signal frequency of the pulse width modulation signal is analyzed by the first control device, and the motor is controlled by the corresponding rotation mode, so that the number of transmission lines of the transmission line set can be reduced.

Description

Electric tool and control method thereof

Technical Field

The present invention relates to power tools; in particular to an electric tool using pulse width modulation signal to change the rotation mode and the control method thereof.

Background

Fig. 1 and 2 show a conventional electric tool 1, which includes a housing 10, a motor 14, an upper circuit board 16 and a lower circuit board 18, wherein the housing 10 has a transmission portion 102 and a hand-held portion 104, the transmission portion 102 is provided with the motor 14 and a driving mechanism (not shown), and the motor 14 is a three-phase dc brushless motor; the handheld portion 104 is provided with an operation interface 12, and the operation interface 12 is operated by a human to generate an operation signal.

The upper circuit board 16 is disposed on the transmission portion 102, and six commutation switch elements 162 and three hall sensors 164 are disposed on the upper circuit board 16, the commutation switch elements 162 are used for controlling the commutation of the motor, and the hall sensors 164 sense the position of the rotor of the motor 14.

The lower circuit board 18 is disposed in the handle portion 104 of the housing 10, the lower circuit board 18 is electrically connected to the battery port 20 for receiving power from the battery 22, and a controller 182 is disposed on the lower circuit board. The lower circuit board 18 is electrically connected to the operation interface 12, so that the controller 182 receives the operation signal from the operation interface 12. The lower circuit board 18 is electrically connected to the upper circuit board 16 through a transmission line group 24, which includes nine control signal transmission lines for transmitting control signals of the plurality of commutation switch elements 162 and five position signal transmission lines for transmitting output signals of the plurality of hall sensors 164. After receiving the operation signal from the operation interface 12, the lower controller 182 generates a control signal for controlling the plurality of commutation switch elements 162 according to the operation signal and the output signals of the hall sensors from the five position signal transmission lines, and transmits the control signal to the plurality of commutation switch elements 162 of the upper circuit board 16 through the nine control signal transmission lines to control the plurality of commutation switch elements 162 to perform commutation, so as to rotate the rotor of the motor 14.

Since at least 14 transmission lines are required for the transmission line group 24 between the upper circuit board 16 and the lower circuit board 18, the arrangement of 14 transmission lines in the limited space of the housing 10 will result in overcrowding, which is not favorable for the wiring of the transmission line group 24 during assembly.

Disclosure of Invention

Accordingly, the present invention is directed to a method for reducing the number of transmission lines in a transmission line set.

In order to achieve the above object, the present invention provides an electric tool, which includes a motor, a first circuit board and a second circuit board, wherein the first circuit board is provided with a first control device, and the first control device is electrically connected to the motor; the second circuit board is electrically connected with the first circuit board through a transmission line group, wherein the transmission line group comprises a command transmission line; the second circuit board is provided with a second control device, the second control device generates a pulse width modulation signal according to one of a plurality of different rotation modes and transmits the pulse width modulation signal through the command transmission line, wherein the frequency of the generated pulse width modulation signal is one of a plurality of different pulse signal frequencies, and the pulse signal frequencies respectively correspond to the rotation modes; the first control device receives the pulse width modulation signal, analyzes the pulse width modulation signal to obtain a corresponding pulse signal frequency, and controls the corresponding action of the motor according to a rotation mode corresponding to the obtained pulse signal frequency.

The present invention further provides a method for controlling an electric tool, comprising the steps of:

selecting one of a plurality of different rotation modes;

the second control device generates a pulse width modulation signal according to the selected rotation mode and transmits the pulse width modulation signal through the command transmission line, wherein the frequency of the generated pulse width modulation signal is one of a plurality of different pulse signal frequencies, and the pulse signal frequencies respectively correspond to the rotation modes;

the first control device receives the pulse width modulation signal, analyzes the pulse width modulation signal to obtain a corresponding pulse signal frequency, and controls the corresponding action of the motor according to a rotation mode corresponding to the obtained pulse signal frequency.

The effect of the present invention is that different pulse signal frequencies of the pulse width modulation signal generated by the second control device represent different rotation modes, and the first control device analyzes the pulse signal frequency of the pulse width modulation signal and controls the motor in the corresponding rotation mode, so that the number of transmission lines of the transmission line set can be reduced, which is beneficial to the wiring of the transmission line set in the housing.

Drawings

Fig. 1 is a schematic view of a conventional power tool.

Fig. 2 is a system block diagram of a conventional power tool.

Fig. 3 is a schematic view of a power tool according to a first preferred embodiment of the present invention.

FIG. 4 is a system block diagram of the preferred embodiment described above.

FIG. 5 is a waveform diagram of the outputs of the three Hall sensors and the rotation speed signal in the preferred embodiment.

Fig. 6 is a flowchart of a control method of the power tool according to the preferred embodiment.

Fig. 7 is a waveform diagram of the pwm signal of the power tool according to the preferred embodiment.

Fig. 8 is a waveform diagram of the pwm signal of the power tool according to the preferred embodiment.

Fig. 9 is a schematic view of a power tool according to a second preferred embodiment of the present invention.

Fig. 10 is a flowchart of a control method of the power tool according to the preferred embodiment.

Fig. 11 is a waveform diagram of the pwm signal of the power tool according to the preferred embodiment.

Fig. 12 is a waveform diagram of the pwm signal of the power tool according to the preferred embodiment.

Fig. 13 is a waveform diagram of the pwm signal of the power tool according to the preferred embodiment.

Detailed Description

In order to more clearly illustrate the present invention, preferred embodiments are described in detail below with reference to the accompanying drawings. Referring to fig. 3 and 4, an electric tool 2 according to a first preferred embodiment of the present invention includes a housing 30, and a motor 32, a first circuit board 36 and a second circuit board 40 disposed in the housing 30, wherein:

the rotating shaft 322 of the motor 32 is connected to a transmission member 34, and the transmission member 34 is exemplified by an impact mechanism in this embodiment, but not limited thereto, and may also be a clutch mechanism, a speed reducing mechanism, etc. The motor is a three-phase dc brushless motor in this embodiment.

The first circuit board 36 is provided with a first control device 38, and the first control device 38 is electrically connected to the motor 32. In this embodiment, the first control device 38 includes a plurality of commutation switch elements 382, a plurality of hall sensors 384 and a first controller 386, wherein the first controller 386 may be a microcontroller, the first controller 386 is electrically connected to the commutation switch elements 382 and the hall sensors 384, the commutation switch elements 382 are six MOSFETs in this embodiment and are electrically connected to the stator of the motor 32, the hall sensors 384 are three and are respectively used for sensing the position of the rotor of the motor, the output level of each hall sensor 384 is changed between a first voltage level and a second voltage level, and the hall sensors respectively output pulse waves in sequence to form a position signal in the form of pulse waves when the rotor rotates 120 degrees. In this embodiment, the first voltage level is exemplified by a low voltage level, and the second voltage level is exemplified by a high voltage level.

The first control device 38 includes a first storage unit 388, in this embodiment, the first storage unit 388 is a memory built in the first controller 386, the first storage unit 388 stores a plurality of control parameters, and the first controller 386 controls the plurality of phase change switch elements 382 according to the plurality of control parameters, so as to control the rotation of the rotating shaft 322 of the motor 32. Each control parameter is used to control the motor to rotate in one of a plurality of different rotation modes, which may be, for example, a forward rotation mode, a reverse rotation mode.

The second circuit board 40 is electrically connected to a battery 46 and an operation interface 48, and a second control device 42 and a display 44 are disposed on the second circuit board 40. The battery 46 provides power to the second circuit board 40, and the operation interface 48 is electrically connected to the second control device 42 and includes an activation switch 482 and a mode selector 484, the activation switch 482 is operated by a user to output an activation signal to the second control device 42, and the mode selector 484 may be a switch and operated by the user to output a selection signal to the second control device 42. The second control device 42 includes a second controller 422 and a second storage unit 424, and the second controller 422 may be a microcontroller and is electrically connected to the display 44. In this embodiment, the second storage unit 424 is a built-in memory of the second controller 422, and the second storage unit 424 stores a plurality of frequency parameters, which correspond to a plurality of different pulse signal frequencies, respectively. The second controller 422 can select a corresponding one of the frequency parameters according to the selection signal, and generate a pulse width modulation signal having a specific one of the pulse signal frequencies according to the selected frequency parameter.

The second circuit board 40 is electrically connected to the first circuit board 36 through a transmission line set 50, and the transmission lines of the transmission line set 50 include a power line 501, a ground line 502, a command transmission line 503, a brake signal line 504, a feedback signal line 505, a current signal line 506, and a rotation speed signal line 507. The power line 501 and the ground line 502 are used to transmit power from the second circuit board 40 to the first circuit board 36. The second control device 42 communicates with the first control device 38 via the command transmission line 503, the brake signal line 504, the feedback signal line 505, the current signal line 506, and the rotation speed signal line 507.

The second control device 42 transmits a pulse width modulation signal to the first control device 38 via the command transmission line 503 as a command for controlling the rotation mode of the motor 32, which will be described in detail later.

The second control device 42 transmits a braking command via the braking signal line 504, and the first control device 38 controls the motor 32 to stop rotating according to the braking command.

The first control device 38 transmits a corresponding feedback signal via the feedback signal line 505, where the feedback signal corresponds to the operation state of the transmission member 34, for example, when the impact mechanism is operated, the feedback signal transmitted by the first control device 38 represents the number of impacts of the impact mechanism by a plurality of pulse waves. In one embodiment, the feedback signal line 505 may not be provided.

The first control device 38 detects the current when the motor 32 is running and transmits a motor current signal via the current signal line 506.

The first controller 386 converts the position signals sensed by the three hall sensors 384 into a rotation speed signal, which is transmitted to the second control device 42 via the rotation speed signal line 507 for the second control device 42 to determine the rotation speed of the motor 32. Referring to fig. 5, in the present embodiment, the first controller 386 changes the rotation speed signal from a third voltage level V3 to a fourth voltage level V4 when the output of each hall sensor 384 transitions from the first voltage level V1 to the second voltage level V2, and the first controller 386 changes the rotation speed signal from the fourth voltage level V4 to the third voltage level V3 when the output of each hall sensor 384 transitions from the second voltage level V2 to the first voltage level V1. In this embodiment, the third voltage level V3 is exemplified by a low voltage level, and the fourth voltage level V4 is exemplified by a high voltage level. In other words, the rotation speed signal has a pulse wave change of one period every 120 degrees of rotation of the rotor, the rotation speed signal has a pulse wave of three periods every one rotation of the rotor, and the second control device 42 can calculate the rotation speed of the rotor according to the pulse wave period of the rotation speed signal, so that the outputs of the three hall sensors 384 are integrated into one, and the number of transmission lines of the transmission line set 50 can be effectively reduced.

In one embodiment, the output of one of the hall sensors 384 in the position signals can also be used as a rotation speed signal by the first controller 386, and the second control device 42 calculates the rotation speed of the rotor according to the pulse wave period output by one of the hall sensors 384. Further, if the second control device 42 does not need to obtain the rotation speed, the rotation speed signal line 507 may not be provided.

For convenience of illustration, the plurality of rotation modes includes a first rotation mode for controlling the motor 32 to rotate in a first rotation direction D1 and a second rotation mode for controlling the motor 32 to rotate in a second rotation direction D2, the second rotation direction D2 being opposite to the first rotation direction D1.

After the rotation mode definition is completed, the plurality of frequency parameters in the second storage unit 424 are set in the second control device 42 to correspond to the plurality of different rotation modes, respectively. For example, the plurality of frequency parameters include a first frequency parameter for generating the pwm signal having the pulse signal frequency at a first frequency and a second frequency parameter for generating the pwm signal having the pulse signal frequency at a second frequency.

The control parameters in the first storage unit 388 are set in the first control device 38 to correspond to the different pulse signal frequencies, respectively. For example, the control parameters include a first control parameter and a second control parameter, the first control parameter and the second control parameter respectively correspond to a first frequency and a second frequency, the first control parameter is used for controlling the motor 32 to rotate along the first rotating direction D1, and the second control parameter is used for controlling the motor 32 to rotate along the second rotating direction D2.

By the above-mentioned structure of the electric tool 2, the control method shown in fig. 6 can be performed, which includes the following steps:

step S11: selecting one of the plurality of different rotation modes. In this embodiment, the user operates the operation interface 48 to select a corresponding one of the rotation modes by the mode selector 484, the mode selector 484 outputs a corresponding selection signal to the second controller 42, and the second controller 422 displays information of the rotation mode through the display 44. After the user depresses the start switch 482, the following steps are performed.

Step S12: the second control device 42 generates a pwm signal according to the selected rotation mode and transmits the pwm signal through the command transmission line 503.

In this embodiment, the second controller 422 selects a corresponding one of the plurality of frequency parameters according to the selection signal, and generates the pwm signal having a corresponding pulse signal frequency according to the selected frequency parameter.

For example, the first frequency parameter is "21K", the second frequency parameter is "10K", and referring to fig. 7, when the mode selector 484 selects the first rotation mode, the second controller 422 generates the pwm signal with the first frequency (21KHz) according to the selected first frequency parameter. Referring to fig. 8, when the mode selector 484 selects the second rotation mode, the second controller 422 generates a pwm signal having a second frequency (10KHz) according to the selected second frequency parameter.

Step S13: the first control device 38 receives the pwm signal, analyzes the waveform of the pwm signal to obtain the pulse signal frequency, and controls the motor 32 according to a rotation mode corresponding to the obtained pulse signal frequency.

In this embodiment, the first controller 386 analyzes the rising edge of a pulse wave in one period and the rising edge of a pulse wave in the next period of the pwm signal, and obtains the corresponding pulse signal frequency according to the reciprocal of a time difference between the rising edges of the two pulse waves (i.e. the first time difference T1 in fig. 7 and 8).

After obtaining the pulse signal frequency of the pwm signal, the first control device 38 selects a corresponding one of the control parameters in the first storage unit 388 according to the obtained pulse signal frequency to control a corresponding operation of the motor 32.

For example, the first controller 386 receives the pwm signal of fig. 7, obtains a pulse signal frequency as a first frequency (21KHz), and the first controller 386 controls the plurality of phase-change switch elements 382 according to a first control parameter corresponding to the first frequency, so as to control the motor 32 to rotate along the first rotation direction D1. Similarly, when the first controller 386 receives the pwm signal of fig. 8 and obtains a pulse signal frequency of a second frequency (10KHz), the first controller 386 controls the plurality of phase-change switch elements 382 according to a second control parameter corresponding to the second frequency, so as to control the motor 32 to rotate along the second rotation direction D2.

In the above, different pulse signal frequencies of the pwm signal generated by the second control device 42 represent different rotation modes and are transmitted through a command transmission line 503, and the first control device 38 analyzes the pulse signal frequency of the pwm signal and controls the motor 32 in the corresponding rotation mode, so that the number of transmission lines of the transmission line set 50 can be reduced and the wiring of the transmission line set 50 in the housing 30 can be facilitated.

Fig. 9 shows a power tool 3 according to a second preferred embodiment of the present invention, which is based on the first embodiment, except that the activation switch 482 includes a rotation speed selector 482a, and when the activation switch 482 is pressed by a user, the rotation speed selector 482a is activated together according to the pressing depth to generate a corresponding rotation speed selection signal to be transmitted to the second control device 42.

The second control device 42 generates a plurality of different rotation speed values according to the different depths of the pressing start switch 482 by the rotation speed selection signal of the rotation speed selector 482 a. In an embodiment, the rotation speed selector 482a may also be independent of the start switch 482, and provide the user with a rotation speed value to output a corresponding rotation speed selection signal.

The second storage unit 424 of the second control device 42 stores a plurality of proportional value parameters, which correspond to a plurality of different duty ratios respectively, and can change the duty ratio of the pwm signal according to one proportional value parameter when generating the pwm signal.

The first storage unit 388 stores a plurality of rotational speed parameters, each rotational speed parameter is used for the first control device 38 to control the rotational speed of the motor 32, and the rotational speed parameters respectively correspond to different rotational speeds of the motor 32.

It is first defined that the proportional parameters of the second storage unit 424 correspond to the rotation speed values, respectively, and the proportional parameters of the first storage unit 388 correspond to the duty ratios and the rotation speed values, respectively. Higher duty cycles represent faster speeds.

Fig. 10 shows a control method of a power tool 3 according to a second preferred embodiment of the present invention, which has substantially the same steps as those of the first embodiment, except that:

step S21: one of a plurality of different rotation modes is selected. This step is the same as step S11 of the first embodiment. After the user depresses the start switch 482, the following steps are performed.

Step S22: the second control device 42 generates a pwm signal according to the selected rotation mode, adjusts the duty ratio of the pwm signal to one of a plurality of different ratios according to different rotation speed values, and transmits the pwm signal through the command transmission line 503.

In this embodiment, the second controller 422 selects a corresponding one of the plurality of frequency parameters according to the selection signal, and generates one of the plurality of rotation speed values according to the different depths at which the user presses the activation switch 482, and selects a corresponding one of the ratio value parameters from the second storage unit 424 according to the generated rotation speed value. Then, the PWM signal with the corresponding pulse signal frequency is generated according to the selected frequency parameter, and the PWM signal with the corresponding duty ratio is generated according to the selected proportional value parameter.

Taking the first frequency parameter as "21K", one of the proportional value parameters as "23", referring to fig. 11, when the mode selector 484 selects the first rotation mode, the second controller 422 generates a pulse width modulation signal with a first frequency (21KHz) according to the selected first frequency parameter, and selects a corresponding proportional value parameter (for example, "23") according to a rotation speed value corresponding to the current rotation speed selection signal and generates a corresponding duty ratio of 23%. Referring to fig. 12, one of the proportional value parameters is "60", and when the depth of the pressing start switch is deeper to reach the rotation speed value corresponding to the proportional value parameter "60", the second controller selects the corresponding proportional value parameter (for example, "60") according to the rotation speed value corresponding to the current rotation speed selection signal, and further changes the duty ratio of the pulse width modulation signal to 60%.

Similarly, when the mode selector 484 selects the second rotation mode, the second controller 422 generates the pulse width modulation signal having the second frequency according to the selected second frequency parameter, and selects the corresponding proportional value parameter according to the rotation speed value corresponding to the current rotation speed selection signal and generates the duty ratio.

Step S23: the first control device 38 receives the pwm signal, analyzes a waveform of the pwm signal to obtain the pulse signal frequency and the duty ratio, controls the motor 32 according to a rotation mode corresponding to the obtained pulse signal frequency, and controls a rotation speed of the motor 32 according to the obtained duty ratio.

With reference to fig. 11 and 12, the first controller 386 analyzes the reciprocal of a first time difference T1 from the rising edge of a pulse wave in one period to the rising edge of a pulse wave in the next period of the pwm signal to obtain a corresponding frequency of the pulse signal. The first controller 386 analyzes a second time difference T2 between a rising edge and a falling edge of a pulse wave of one period of the pwm signal, and obtains the duty ratio according to a ratio of the second time difference T2 to the first time difference T1.

After the first controller 386 obtains the pulse signal frequency and the duty ratio of the pwm signal, the first controller 386 selects a corresponding one of the plurality of control parameters in the first storage unit 388 according to the obtained pulse signal frequency and selects a corresponding one of the rotation speed parameters according to the current duty ratio to control the motor to generate a corresponding rotation speed in the rotation mode according to the action corresponding to the selected rotation mode and the selected rotation speed parameter of the motor 32.

For example, the first controller 386 receives the pwm signal of fig. 11, obtains a pulse signal frequency as a first frequency (21KHz), a duty ratio is 23%, and the first controller 386 controls the plurality of phase-change switch elements 382 according to a first control parameter corresponding to the first frequency and a rotation speed parameter corresponding to the duty ratio of 23%, so as to control the motor 32 to rotate along the first rotation direction D1 and have a corresponding rotation speed.

As shown in fig. 13, in the rotating process, if the user changes the depth of the pressing start switch 482 to reach the rotation speed value corresponding to the proportional value parameter "60", the second controller 422 selects the proportional value parameter according to the rotation speed value corresponding to the current rotation speed selection signal, and changes the duty ratio of the pulse width modulation signal to 60%, the first controller controls the phase change switch elements 382 according to the first control parameter corresponding to the first frequency and the rotation speed parameter corresponding to the duty ratio of 60%, so as to control the motor 32 to rotate along the first rotating direction D1 and have a corresponding higher rotation speed.

Similarly, if the pulse signal frequency of the pwm signal received by the first controller is the second frequency, the plurality of phase change switch elements 382 are controlled according to the second control parameter and a rotation speed parameter corresponding to the current duty ratio, so as to control the motor 32 to rotate along the second rotation direction D2 at the corresponding rotation speed.

Accordingly, the second embodiment of the present invention can also reduce the number of transmission lines of the transmission line set 50 by transmitting the pwm signal through the command transmission line 503, and can simultaneously adjust the rotation speed by using the duty ratio of the pwm signal without transmitting the rotation speed command through an additional transmission line.

The rotation modes in the above embodiments may also include other rotation modes, not limited to the first rotation mode and the second rotation mode.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications to the present invention as described and claimed should be included in the scope of the present invention.

Description of the reference numerals

[ conventional ]

1: electric tool

10: shell body

102: transmission part

104: hand-held part

12: operation interface

14: motor with a stator having a stator core

16: upper circuit board

162: phase change switch element

164: hall sensor

18: lower circuit board

182: controller

20: battery port

22: battery with a battery cell

24: transmission line group

[ invention ]

2. 3: electric tool

30: shell body

32: motor with a stator having a stator core

322: rotating shaft

34: transmission member

36: first circuit board

38: first control device

382: phase change switch element

384: hall sensor

386: first controller

388: a first storage unit

40: second circuit board

42: second control device

422: second controller

424: second storage unit

44: display device

46: battery with a battery cell

48: operation interface

482: starting switch

482 a: rotating speed selector

484: mode selector

50: transmission line group

501: power line

502: grounding wire

503: command transmission line

504: brake signal line

505: feedback signal line

506: current signal line

507: speed signal line

D1: first direction of rotation

D2: second direction of rotation

S11-S13, S21-S23: step (ii) of

V1: first voltage level

V2: second voltage level

V3: third voltage level

V4: fourth voltage level

Claims

1. A power tool, comprising:

a motor;

the first circuit board is provided with a first control device, and the first control device is electrically connected with the motor;

the second circuit board is electrically connected with the first circuit board through a transmission line group, wherein the transmission line group comprises a command transmission line; the second circuit board is provided with a second control device, the second control device generates a pulse width modulation signal according to one of a plurality of different rotation modes and transmits the pulse width modulation signal through the command transmission line, wherein the frequency of the generated pulse width modulation signal is one of a plurality of different pulse signal frequencies, and the pulse signal frequencies respectively correspond to the rotation modes;

2. The power tool of claim 1, wherein each cycle of the pwm signal generated by the second control device has a duty cycle, the second control device adjusting the duty cycle to one of a plurality of different ratios according to a plurality of different rotational speed values; the first control device analyzes the pulse width modulation signal to obtain the duty ratio, and controls the rotating speed of the motor according to the obtained duty ratio.

3. The power tool of claim 2, wherein the plurality of rotation modes includes a first rotation mode and a second rotation mode, the first rotation mode corresponds to a first frequency of the pulse signal, and the second rotation mode corresponds to a second frequency of the pulse signal; the second control device generates the corresponding pulse width modulation signal according to the first rotation mode or the second rotation mode, and adjusts the ratio of the duty ratio of the pulse width modulation signal according to a rotation speed value; the first control device controls the motor according to the pulse signal frequency of the pulse width modulation signal, wherein when the pulse signal frequency is a first frequency, the motor is controlled to rotate along a first rotating direction according to the rotating speed value according to the duty ratio of the pulse width modulation signal; and when the frequency of the pulse signal is a second frequency, controlling the motor to rotate along a second rotation direction according to the rotation speed value according to the duty ratio of the pulse width modulation signal, wherein the second rotation direction is opposite to the first rotation direction.

4. The power tool of claim 1, wherein the plurality of rotation modes includes a first rotation mode and a second rotation mode, the first rotation mode corresponds to a first frequency of the pulse signal, and the second rotation mode corresponds to a second frequency of the pulse signal; the second control device generates the corresponding pulse width modulation signal according to the first rotation mode or the second rotation mode; the first control device controls the motor according to the pulse signal frequency of the pulse width modulation signal, wherein when the pulse signal frequency is the first frequency, the motor is controlled to rotate along a first rotating direction; when the pulse signal frequency is a second frequency, the motor is controlled to rotate along a second rotating direction, and the second rotating direction is opposite to the first rotating direction.

5. The power tool according to claim 1, wherein the second control device has a second storage unit, the second storage unit stores a plurality of frequency parameters, the plurality of frequency parameters respectively correspond to the plurality of pulse signal frequencies and to the plurality of rotation modes;

the first control device is provided with a first storage unit, the first storage unit stores a plurality of control parameters, and the control parameters respectively correspond to the pulse signal frequencies and the rotation modes;

the second control device selects a corresponding frequency parameter according to one of the rotation modes, and generates the pulse width modulation signal with a corresponding pulse signal frequency according to the selected frequency parameter;

the first control device selects a corresponding control parameter according to the obtained pulse signal frequency, and controls the corresponding action of the motor according to the selected control parameter.

6. The electric tool according to claim 5, wherein the second storage unit stores a plurality of proportional value parameters corresponding to a plurality of different duty ratios and a plurality of different rotation speed values, respectively;

the first storage unit stores a plurality of rotation speed parameters, and the rotation speed parameters respectively correspond to the duty ratios and the rotation speed values;

the second control device selects a corresponding proportional value parameter according to the rotation speed value, and generates the pulse width modulation signal with a corresponding duty ratio according to the selected proportional value parameter;

the first control device analyzes the pulse width modulation signal to obtain a duty ratio, selects a corresponding rotating speed parameter according to the obtained duty ratio, and controls the motor to generate a corresponding rotating speed when the motor acts according to the selected rotating speed parameter.

7. The power tool of claim 2, wherein the first control device analyzes a rising edge of a pulse wave of one period and a rising edge of a pulse wave of the next period of the pwm signal, and obtains a corresponding frequency of the pulse signal according to an inverse of a first time difference between the rising edges of the two pulse waves; the first control device analyzes a second time difference between a rising edge and a falling edge of a pulse wave of one period of the pulse width modulation signal, and obtains the duty ratio according to the proportion of the second time difference to the first time difference.

8. The power tool according to claim 1, wherein the first control device analyzes a rising edge of a pulse wave of one period and a rising edge of a pulse wave of the next period of the pwm signal, and obtains a corresponding frequency of the pulse signal according to an inverse of a time difference between the rising edges of the two pulse waves.

9. A control method of an electric tool comprises a motor, a first circuit board and a second circuit board, wherein the first circuit board is provided with a first control device, and the first control device is electrically connected with the motor; the second circuit board is electrically connected with the first circuit board through a transmission line group, wherein the transmission line group comprises a command transmission line; a second control device is arranged on the second circuit board; the control method comprises the following steps:

selecting one of a plurality of different rotation modes;

10. The method of claim 9, wherein each cycle of the pwm signal generated by the second control device has a duty cycle, the second control device adjusting the duty cycle to one of a plurality of different ratios according to a plurality of different rotational speed values; the first control device analyzes the pulse width modulation signal to obtain the duty ratio, and controls the motor to change the rotating speed according to the obtained duty ratio.

11. The control method of an electric tool according to claim 10, wherein the plurality of rotation modes include a first rotation mode and a second rotation mode; the second control device generates the corresponding pulse width modulation signal according to whether the selected rotation mode is the first rotation mode or the second rotation mode, and adjusts the ratio of the duty ratio of the pulse width modulation signal according to a rotation speed value, wherein the frequency of the pulse signal corresponding to the first rotation mode is a first frequency, and the frequency of the pulse signal corresponding to the second rotation mode is a second frequency; the first control device controls the motor according to the pulse signal frequency of the pulse width modulation signal, wherein when the pulse signal frequency is a first frequency, the motor is controlled to rotate along a first rotating direction according to the rotating speed value according to the duty ratio of the pulse width modulation signal; and when the frequency of the pulse signal is a second frequency, controlling the motor to rotate along a second rotation direction according to the rotation speed value according to the duty ratio of the pulse width modulation signal, wherein the second rotation direction is opposite to the first rotation direction.

12. The control method of an electric tool according to claim 9, wherein the plurality of rotation modes include a first rotation mode and a second rotation mode; the second control device generates the corresponding pulse width modulation signal according to whether the selected rotation mode is the first rotation mode or the second rotation mode, wherein the frequency of the pulse signal corresponding to the first rotation mode is a first frequency, and the frequency of the pulse signal corresponding to the second rotation mode is a second frequency; the first control device controls the motor according to the pulse signal frequency of the pulse width modulation signal, wherein when the pulse signal frequency is a first frequency, the motor is controlled to rotate along a first rotating direction according to the rotating speed value; and when the pulse signal frequency is a second frequency, controlling the motor to rotate along a second rotation direction according to the rotation speed value, wherein the second rotation direction is opposite to the first rotation direction.

13. The method of claim 9, wherein the step of generating the pulse width modulation signal by the second control device comprises:

selecting a corresponding one of a plurality of frequency parameters according to the selected rotation mode, wherein the plurality of frequency parameters respectively correspond to the plurality of pulse signal frequencies and correspond to the plurality of rotation modes; and

generating the PWM signal having a corresponding pulse signal frequency according to the selected frequency parameter;

wherein the step of controlling the motor by the first control device according to the rotation mode corresponding to the obtained pulse signal frequency comprises:

selecting a corresponding one from a plurality of control parameters according to the obtained pulse signal frequency, wherein the plurality of control parameters respectively correspond to the plurality of pulse signal frequencies and the plurality of rotation modes; and

and controlling the corresponding action of the motor according to the selected control parameters.

14. The method of claim 13, wherein the step of generating the pwm signal by the second control means further comprises:

selecting a corresponding one from a plurality of proportional value parameters according to one of a plurality of rotating speed values, wherein the proportional value parameters respectively correspond to a plurality of different duty ratios;

generating the PWM signal with a corresponding duty ratio according to the selected proportional value parameter;

wherein the step of controlling the motor by the first control device according to the rotation mode corresponding to the obtained pulse signal frequency further comprises:

analyzing the pulse width modulation signal to obtain a duty ratio;

selecting a corresponding one of a plurality of rotational speed parameters according to the obtained duty ratio;

and controlling the motor to generate corresponding rotating speed when the motor acts according to the selected rotating speed parameter.

15. The method according to claim 10, wherein the first control device analyzes a rising edge of a pulse wave of one period and a rising edge of a pulse wave of a next period of the pwm signal, and obtains a frequency of the pulse signal according to an inverse of a first time difference between the rising edges of the two pulse waves; the first control device analyzes a second time difference between a rising edge and a falling edge of a pulse wave of one period of the pulse width modulation signal, and obtains the duty ratio according to the proportion of the second time difference to the first time difference.

16. The method according to claim 9, wherein the first control device analyzes a rising edge of a pulse wave of one period and a rising edge of a pulse wave of a next period of the pwm signal, and obtains a corresponding frequency of the pulse signal according to an inverse of a time difference between the rising edges of the two pulse waves.