CN115967332A - Electric tool and control method thereof - Google Patents
Electric tool and control method thereof Download PDFInfo
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- CN115967332A CN115967332A CN202110519167.9A CN202110519167A CN115967332A CN 115967332 A CN115967332 A CN 115967332A CN 202110519167 A CN202110519167 A CN 202110519167A CN 115967332 A CN115967332 A CN 115967332A
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Abstract
The invention discloses an electric tool and a control method thereof, wherein the tool comprises: a motor having a plurality of phase windings; a drive circuit having a plurality of semiconductor switching elements to switch an energization state of a winding of the motor; the power interface is used for accessing a power supply to supply power to the motor; a controller electrically connected to at least the motor or the driving circuit, wherein the controller is configured to: acquiring the demagnetization time of a motor winding after phase change; determining the load state of the motor according to the demagnetization time; when the motor is determined to be in the no-load state according to the demagnetization time, outputting a first control signal with a first duty ratio to control the motor to operate; and when the motor is determined to be in the loading state according to the degaussing time, outputting a second control signal with a second duty ratio to control the motor to operate. The electric tool capable of flexibly adjusting the rotating speed of the motor is realized.
Description
Technical Field
The present invention relates to an electric tool, and more particularly, to an electric tool and a control method thereof.
Background
With the development of electronic technology, electric tools are widely used, and may be classified into garden electric tools, professional electric tools, household electric tools, and the like according to different application scenarios of the electric tools. Most electric tools are provided with operation components such as buttons or triggers for users to perform startup and shutdown operations or adjust the rotating speed of a motor or adjust torque, however, if the electric tools do not have a speed adjusting component or the speed adjusting mode is single, the flexibility of tool control is affected, and the user experience is reduced.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide an electric tool capable of flexibly adjusting the rotating speed of a motor.
In order to achieve the above object, the present invention adopts the following technical solutions:
a power tool, comprising: a motor having a plurality of phase windings; a drive circuit having a plurality of semiconductor switching elements to switch an energization state of a winding of the motor; the power interface is used for accessing a power supply to supply power to the motor; a controller in electrical connection with at least the motor and/or the drive circuit, wherein the controller is configured to: acquiring the demagnetization time after the phase of a motor winding is changed, wherein the demagnetization time is the time difference between the rising edge of phase voltage and the falling edge of the phase voltage after the phase of the winding is changed; determining the load state of the motor according to the demagnetization time; when the motor is determined to be in a no-load state according to the demagnetization time, outputting a first control signal with a first duty ratio to control the motor to operate; and when the motor is determined to be in a load state according to the demagnetizing time, outputting a second control signal with a second duty ratio to control the motor to operate.
Further, the first duty cycle is less than the second duty cycle.
Further, the controller is configured to: when the degaussing time is larger than a first time threshold value, determining that the motor is in a loaded state; and when the demagnetization time is smaller than a second time threshold, determining that the motor is in a no-load state.
Further, the first time threshold is greater than or equal to the second time threshold.
Further, the controller is configured to: and outputting a first control signal with the first duty ratio to control the motor to start.
Further, the method also comprises the following steps: the data detection module is used for detecting relevant working parameters of the motor; the controller is configured to: acquiring relevant working parameters of the motor; calculating control parameters of the motor according to the demagnetization time and relevant working parameters of the motor; when the control parameter is larger than the first parameter threshold value, outputting a second control signal with a second duty ratio to control the motor to operate; and when the control parameter is smaller than a second parameter threshold value, outputting a first control signal with a first duty ratio to control the motor to operate.
Further, the controller is configured to: and adjusting the first parameter threshold value and/or the second parameter threshold value and/or the first time threshold value and/or the second time threshold value according to the relevant working parameters of the motor.
Further, the relevant operating parameter of the motor includes the rotation speed or temperature of the motor or the output current or the bus voltage.
A method of controlling a power tool comprising a motor having a plurality of phase windings; a drive circuit having a plurality of semiconductor switching elements to switch an energization state of a winding of the motor; the power interface is used for connecting a power supply to supply power to the motor; a controller electrically connected to at least the motor and/or the drive circuit, the method comprising: acquiring the demagnetization time after the phase of a motor winding is changed, wherein the demagnetization time is the time difference between the rising edge of phase voltage and the falling edge of the phase voltage after the phase of the winding is changed; determining the load state of the motor according to the demagnetization time; when the motor is determined to be in a no-load state according to the demagnetization time, outputting a first control signal with a first duty ratio to control the motor to operate; and when the motor is determined to be in a loaded state according to the demagnetization time, outputting a second control signal with a second duty ratio to control the motor to operate.
Further, the first duty cycle is less than the second duty cycle.
The invention has the beneficial effects that the load state of the motor is determined through the demagnetization time after the phase of the motor is changed, so that the rotating speed of the motor is adjusted, and the electric tool with flexibly controlled rotating speed is realized.
Drawings
Fig. 1 is a structural view of an electric power tool as one embodiment;
fig. 2 is a block circuit diagram of a power tool as an embodiment;
FIG. 3 shows a schematic diagram of a degaussing time as an embodiment;
fig. 4 is a schematic diagram showing a demagnetization time generated when a motor in a power tool is commutated as one embodiment;
FIG. 5 is a schematic flow chart of a motor speed control based on a demagnetization time as an embodiment;
fig. 6 is a block circuit diagram of an electric power tool as an embodiment;
fig. 7 is a schematic flowchart of a motor speed control based on a demagnetization time according to an embodiment.
Detailed Description
The invention is described in detail below with reference to the figures and the embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
The technical scheme of the invention can be suitable for various electric tools of different types, such as a handheld electric tool, an electric hammer, a reciprocating saw, an electric hammer and the like, and can also be garden electric tools, such as a mower, a blower and the like. The present application is directed primarily to hand-held power tools. The electric hammer will be explained as an example.
In a first embodiment of the present invention, reference is made to a mechanical structure of a power tool shown in fig. 1 and a circuit structure of the power tool shown in fig. 2. The power tool 100 may include at least an operation switch 10, a motor 20, a power interface 30, a drive circuit 40, and a controller 50.
The switch 10 is operated by a user to perform a power on/off operation. Alternatively, the operation switch 10 may be a mechanical switch or an electronic switch.
The motor 20 is used for outputting power to brake the electric tool, the motor 20 can be a three-phase brushless motor, and the three-phase stator windings A, B and C are connected in a triangular or Y shape.
A power interface 30 for receiving a power supply 301 to supply power to the motor 20. In one embodiment, the power source may be an ac power source, and the power interface 30 may be connected to 120V or 220V ac mains. In one embodiment, the power source may be selected as a battery pack, which may be composed of a group of battery cells, for example, the battery cells may be connected in series into a single power branch, forming a 1P battery pack. The output voltage of the battery pack is subjected to voltage change through a specific power control module, such as a DC-DC module, and the output voltage is suitable for a driving circuit, a motor and the like to supply power to the driving circuit, the motor and the like. Those skilled in the art will appreciate that the DC-DC module is a well-established circuit structure and can be selected accordingly according to the requirements of the specific parameters of the power tool.
In one embodiment, the power tool 100 further integrates a control module 200, which control module 200 may include the drive circuit 40 and the controller 50, primarily for regulating the power supply of the power interface 30 to the motor 20. In one embodiment, the control module 200 may be disposed within the housing 10 below the motor 20, it being understood that the location of the control module 200 may be anywhere on the power tool 100 depending on the shape and size of the power tool.
The driving circuit 40 is electrically connected to the stator windings a, B, and C of the motor 20, and is configured to transmit current from the power circuit 20 to the stator windings a, B, and C to drive the motor 20 to rotate. As one of the embodiments, as shown in fig. 2, the driving circuit 40 includes a plurality of switching elements Q1, Q2, Q3, Q4, Q5, Q6. Each gate terminal of the switching element is electrically connected to the controller 50 for receiving a control signal from the controller 50. Each drain or source of the switching elements is connected to a stator winding a, B, C of the motor 20. The switching elements Q1-Q6 receive control signals from the controller 50 to change the respective conduction states and thereby vary the current that the power circuit 20 applies to the stator windings a, B, C of the motor 20. In one embodiment, the driver circuit 40 may be a three-phase bridge driver circuit including six controllable semiconductor power devices (e.g., FETs, BJTs, IGBTs, etc.). It is to be understood that the above-mentioned switching elements may also be any other type of solid-state switches, such as Insulated Gate Bipolar Transistors (IGBTs), bipolar Junction Transistors (BJTs) etc.
In order to rotate the motor 20, the driving circuit 40 has a plurality of driving states, in which a stator winding of the motor generates a magnetic field, and the controller 50 outputs a corresponding PWM control signal to the switching element in the driving circuit 40 according to a rotor position or a back electromotive force of the motor to switch the driving state of the driving circuit 40, so that the stator winding generates a changing magnetic field to drive the rotor to rotate, thereby realizing rotation or phase change of the motor 20. It should be noted that any other circuit and control method capable of driving the rotation or phase change of the motor 20 can be used in the present disclosure, and the present disclosure does not limit the circuit structure of the driving circuit 40 and the control of the driving circuit 40 by the controller 50.
In one embodiment, when the user activates the operation switch 10 to start the power tool, the controller 50 outputs a first control signal with a first duty ratio to the driving circuit to start the motor. At this time, since the rotation speed of the motor is not immediately increased to be high immediately after the motor is started, the first duty ratio of the first control signal is less than 100%, and may be, for example, 60%, 50%, or 40%. In addition, when the general electric tool is started in an idle load, the noise of the idle load starting can be reduced to a certain extent by controlling the motor to start by the control signal with a small duty ratio.
Further, after the motor is started, the controller can acquire the demagnetization time after the phase of the motor winding is changed, and judge the load state of the motor according to the demagnetization time. And then corresponding control signals are output according to the load state of the motor to control the motor to operate. For example, when the demagnetization time is greater than the first time threshold, it may be determined that the motor is in a loaded state, and the controller may output a first control signal to control the motor to operate, so as to increase the rotation speed of the motor. Thereby the flexibility of motor speed adjustment has been guaranteed. When the degaussing time is less than the second time threshold, the motor can be determined to be in the no-load state, and then the controller outputs a second control signal to control the motor to operate so as to reduce the rotating speed of the motor. Thereby reducing the operating noise by reducing the rotational speed when the motor is unloaded. Wherein the first time threshold is greater than or equal to the second time threshold. It can be understood that the demagnetizing time refers to that when the motor commutates in a mode that the motor windings are conducted pairwise, the turn-off phase current cannot be suddenly changed to zero due to the existence of the inductance of the motor (i.e., the phase current on the windings after the commutation cannot be suddenly changed to zero), at this time, the turn-off phase current continues to flow through the diodes connected in parallel in the reverse direction, and the continuous time of the flow continues to be the demagnetizing time. It will also be understood that the degaussing time is the time difference between the rising edge of the phase voltage and the falling edge of the phase voltage after commutation of the motor windings, where the falling edge of the phase voltage is the first falling edge after the above-mentioned rising edge. It is understood that during the adjustment of the motor speed, the first control signal is to control the motor speed to decrease, and the second control signal is to control the motor speed to increase. Thus, in general, the first duty cycle of the first control signal is smaller than the second duty cycle of the second control signal, e.g., the first duty cycle is 60% and the second duty cycle is 100%.
In one embodiment, the controller may obtain the demagnetization time after the phase of the motor is changed according to the relative relationship between the bus voltage and the phase voltage. That is, in one implementation, the controller may determine the load state of the motor according to a change in a relative relationship between the bus voltage and the phase voltage, and then output control signals having different duty ratios to increase or decrease the rotation speed of the motor. For example, when the change of the relative relation meets a first preset change condition, a first control signal with a first duty ratio is output to control the motor to reduce the rotating speed; and when the change of the relative relation meets a second preset change condition, outputting a second control signal with a second duty ratio to control the motor to increase the rotating speed. In the application, the change of the rotating speed of the motor is controlled by monitoring the relative relation between the bus voltage and the phase voltage, so that the motor can be more flexibly controlled to perform self-adaptive adjustment of the rotating speed.
It will be appreciated that the relative relationship of the bus voltage and the phase voltages includes either the bus voltage being greater than the phase voltages or the bus voltage being less than the phase voltages. In the application, the controller can change the duty ratio of the control signal by comparing the time node of the change of the relative relation between the half bus voltage and the phase voltage so as to adjust the rotating speed of the motor. For example, as shown in fig. 3, assume that the bus voltage is Us, the phase voltage is Ua, and the time node where the relative relationship between the two changes is taken as the first time node
Is about to >>
Is the first time node and occurs after this for the first time->
Is the second time node->
. The controller monitors the first time node->
And a second time node +>
The duty ratio of the control signal is changed by the preset time length which is met by the time length delta t between the first and second time lengths, and the rotating speed of the motor is further changed.
In one embodiment, the time node is defined
And &>
The duration delta t between the two phases is the follow current time after the phase change of the motor, namely the demagnetization time. The demagnetization time of the motor during phase change can be determined according to the bus voltage and the phase voltage of the motor. When the delta t is larger than the first time threshold, the controller determines that the motor is in a loaded state, and then outputs a second control signal with a second duty ratio to control the motor to increase the rotating speed; when the delta t is smaller than the second time threshold, the controller determines that the motor is in the no-load state, and then outputs a first control signal to control the motor to reduce the rotating speed. Referring to the schematic phase change diagram of the motor shown in fig. 4, during any phase change of the motor, a sudden change occurs in the phase voltage of the phase changed in the motor, and the time for maintaining the voltage value after the sudden change is the demagnetization time. In one embodiment, the phase voltage jump is typically a decrease from a maximum Us to 0 or an increase from 0 to a maximum Us, for example, at the upper bridgeAfter the phase change, namely AC phase change to BC, the time for reducing the A phase voltage from Us to 0 is the demagnetization time after the A phase change.
In one embodiment, the degaussing time may also be obtained by means of AD sampling. It can be understood that the acquisition of the demagnetization time is not limited by the present application, and any other manners of acquiring the demagnetization time are within the protection scope of the present application.
It can be understood that only the degaussing time is used as an influencing parameter for controlling the change of the rotating speed of the motor, and the deviation of the acquisition of the degaussing time caused by the change of the power supply voltage can exist, thereby influencing the accuracy of the control.
In one embodiment, the controller may further obtain relevant operating parameters of the motor after startup, such as operating voltage, current, or temperature of the motor. The controller may then calculate a control parameter of the electric machine based on the degaussing time and an associated operating parameter of the electric machine, e.g. the control parameter is determined based on the product of the degaussing time and the bus voltage. Further, when the control parameter is greater than the first parameter threshold value, the controller outputs a second control signal; when the control parameter is smaller than the second parameter threshold value, the controller outputs a first control signal. In this embodiment, the first parameter threshold is greater than or equal to the second parameter threshold. The product of the degaussing time and the bus voltage is used as a control parameter for controlling the motor to change the rotating speed, and the phase voltage is used as a compensation quantity, so that the problem of reduction of control accuracy caused by the change of the power supply voltage is solved.
It should be noted that, as the use time of the tool increases, or other working conditions (for example, changes of the ambient temperature, etc.) affecting the working performance of the tool are encountered during the use process, if the preset time threshold is still used as the threshold for the adjustment of the control manner, the accuracy of the motor control may be affected. Therefore, as shown in fig. 5, the operating parameter of the motor may be obtained by the data detecting module 60, and the preset first time threshold and/or the preset second time threshold may be adjusted according to the operating parameter. In one embodiment, the first parameter threshold or the second parameter threshold may also be adjusted according to an operating parameter such as a current, a rotation speed, or a temperature of the motor. The preset threshold value is adjusted at any time according to the relevant working parameters of the motor, so that the problem that the motor is controlled inaccurately due to the influence of uncontrollable factors is avoided.
A method for controlling the rotation speed of the motor according to the demagnetization time in the electric tool will be described with reference to fig. 6, and the method includes the following steps:
and S101, collecting bus voltage.
S102, collecting phase voltage.
And S103, calculating the demagnetization time of the motor after phase change based on the bus voltage and the phase voltage.
And S104, judging the relation between the demagnetization time and a time threshold, and when the demagnetization time is greater than the first time threshold, turning to the step S105, and when the demagnetization time is less than the second time threshold, turning to the step S106.
And S105, outputting a second control signal to control the rotation speed of the motor to increase.
And S105, outputting a first control signal to control the rotation speed of the motor to be reduced.
In the electric tool shown in fig. 7, the method for controlling the rotation speed of the motor according to the demagnetization time comprises the following steps:
s201, start.
And S202, controlling the motor to start at a duty ratio of 60%.
S203, judging whether the degaussing time is larger than a first time threshold value, namely whether the degaussing time is larger than T1. If yes, go to step S204, otherwise, continue to judge.
And S204, judging whether the times of the degaussing time being more than T1 is more than a time threshold value 3. If yes, go to step S205, otherwise, continue to determine. That is, the degaussing time can be collected at a certain frequency and compared with T1, and when the degaussing time is greater than T1 for more than 3 times, the duty ratio is increased to increase the rotational speed of the motor. The number threshold may be other values. By setting the comparison time threshold, misjudgment caused by sudden change of the demagnetization time is avoided, and the control accuracy is ensured.
And S205, increasing the duty ratio to 100% and increasing the rotating speed of the motor.
And S206, judging whether the degaussing time is less than a second time threshold value, namely, whether the degaussing time is less than T2. If yes, go to step S207, otherwise, continue to determine.
S207, judging whether the times of demagnetization time smaller than T2 is larger than the times threshold value 3. If yes, go to step S208, otherwise, continue to judge. That is to say, the degaussing time can be collected at a certain frequency and compared with T2, and when the number of times that the degaussing time is less than T2 is more than 3, the duty ratio is reduced to reduce the rotation speed of the motor. The number threshold may be other values. By setting the comparison time threshold, misjudgment caused by sudden change of the demagnetization time is avoided, and the control accuracy is ensured.
The two times thresholds may be the same or different.
And S208, reducing the duty ratio to 60% and reducing the rotating speed of the motor.
It will be appreciated that the change in the speed of the motor may be controlled at any time during operation of the motor, depending on the degaussing time, with the duty cycle of the control signal being increased or decreased accordingly in order to increase or decrease the speed of the motor. And the specific value of the duty ratio can be determined according to actual conditions.
And S209, ending.
It should be noted that any other motor control that can be implemented according to the detected demagnetization time or by simple calculation based on the demagnetization time is within the protection scope of the present invention, and is not listed here.
It is to be noted that the foregoing description is only exemplary of the invention and that the principles of the technology may be employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments illustrated herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.
Claims (10)
1. A power tool, comprising:
a motor having a plurality of phase windings;
a drive circuit having a plurality of semiconductor switching elements to switch an energization state of a winding of the motor;
the power interface is used for accessing a power supply to supply power to the motor;
the controller is at least electrically connected with the motor and/or the driving circuit;
wherein the controller is configured to:
acquiring the demagnetization time after the phase of a motor winding is changed, wherein the demagnetization time is the time difference between the rising edge of phase voltage and the falling edge of the phase voltage after the phase of the winding is changed;
determining the load state of the motor according to the demagnetization time;
when the motor is determined to be in a no-load state according to the demagnetization time, outputting a first control signal with a first duty ratio to control the motor to operate;
and when the motor is determined to be in a loaded state according to the demagnetization time, outputting a second control signal with a second duty ratio to control the motor to operate.
2. The power tool according to claim 1,
the first duty cycle is less than the second duty cycle.
3. The power tool according to claim 1,
the controller is configured to:
when the degaussing time is larger than a first time threshold value, determining that the motor is in a loaded state;
and when the degaussing time is less than a second time threshold value, determining that the motor is in an idle state.
4. The power tool according to claim 3,
the first time threshold is greater than or equal to the second time threshold.
5. The power tool according to claim 1,
the controller is configured to:
and outputting a first control signal with the first duty ratio to control the motor to start.
6. The power tool according to claim 1,
further comprising:
the data detection module is used for detecting relevant working parameters of the motor;
the controller is configured to:
acquiring relevant working parameters of the motor;
calculating control parameters of the motor according to the demagnetization time and relevant working parameters of the motor;
when the control parameter is larger than the first parameter threshold value, outputting a second control signal with a second duty ratio to control the motor to operate;
and when the control parameter is smaller than a second parameter threshold value, outputting a first control signal with a first duty ratio to control the motor to operate.
7. The power tool according to claim 6,
the controller is configured to:
and adjusting the first parameter threshold value and/or the second parameter threshold value and/or the first time threshold value and/or the second time threshold value according to the relevant working parameters of the motor.
8. The power tool according to claim 6,
the relevant working parameters of the motor comprise the rotating speed or the temperature or the output current or the bus voltage of the motor.
9. A method of controlling a power tool including a motor having a number of phase windings; a drive circuit having a plurality of semiconductor switching elements to switch an energization state of a winding of the motor; the power interface is used for connecting a power supply to supply power to the motor; the controller is at least electrically connected with the motor and/or the driving circuit; the method comprises the following steps:
acquiring the demagnetization time after the phase of a motor winding is changed, wherein the demagnetization time is the time difference between the rising edge of phase voltage and the falling edge of the phase voltage after the phase of the winding is changed;
determining the load state of the motor according to the demagnetization time;
when the motor is determined to be in a no-load state according to the demagnetization time, outputting a first control signal with a first duty ratio to control the motor to operate;
and when the motor is determined to be in a loaded state according to the demagnetization time, outputting a second control signal with a second duty ratio to control the motor to operate.
10. The control method according to claim 9,
the first duty cycle is less than the second duty cycle.
Priority Applications (1)
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| CN202110519167.9A CN115967332A (en) | 2021-05-12 | 2021-05-12 | Electric tool and control method thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110519167.9A CN115967332A (en) | 2021-05-12 | 2021-05-12 | Electric tool and control method thereof |
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| CN115967332A true CN115967332A (en) | 2023-04-14 |
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