CN118100696A - Electric tool and control method thereof - Google Patents
Electric tool and control method thereof Download PDFInfo
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- CN118100696A CN118100696A CN202211445223.XA CN202211445223A CN118100696A CN 118100696 A CN118100696 A CN 118100696A CN 202211445223 A CN202211445223 A CN 202211445223A CN 118100696 A CN118100696 A CN 118100696A
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- 238000000034 method Methods 0.000 title claims description 18
- 238000001514 detection method Methods 0.000 claims abstract description 11
- 238000004804 winding Methods 0.000 claims abstract description 4
- 238000010586 diagram Methods 0.000 description 7
- 230000007246 mechanism Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 3
- 238000005070 sampling Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
- H02P6/08—Arrangements for controlling the speed or torque of a single motor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
- B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/0094—Structural association with other electrical or electronic devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/20—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection for measuring, monitoring, testing, protecting or switching
- H02K11/21—Devices for sensing speed or position, or actuated thereby
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
- H02K11/30—Structural association with control circuits or drive circuits
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Mechanical Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Control Of Motors That Do Not Use Commutators (AREA)
Abstract
The present invention provides an electric tool including: a battery pack; the brushless motor comprises a stator winding, a rotor and a position detection unit for detecting a position signal of the brushless motor; a control assembly electrically connecting the battery pack and the brushless motor, including a plurality of switching elements configured to perform switching control according to a PWM duty cycle and/or a conduction angle to drive the brushless motor; the control component is configured to calculate the actual rotating speed of the brushless motor according to the position signal, and enable the brushless motor to maintain the target rotating speed by selectively adjusting the PWM duty ratio and/or the conduction angle of the switching element; the control component presets a parameter threshold and a conduction angle reference value, the control component is configured to detect parameters representing the load of the brushless motor, and when the parameters exceed the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value. When the parameter exceeds the parameter threshold, the conduction angle is controlled not to exceed the conduction angle reference value, so that the phenomenon that the motor current is at a high value for a long time, and the operation efficiency is reduced is avoided.
Description
Technical Field
The present invention relates to the field of electric tools, and more particularly, to an electric tool and a control method thereof.
Background
The electric tool is widely applied to the working environments such as families, gardens and the like, and brings great convenience to the life and the operation of people. The electric tool can be powered by a battery pack, and after a switch of the electric tool is powered on, the motor rotates and drives the transmission mechanism to realize various power operations.
In order to achieve a desired output power, conventional power tools are typically adjusted by adjusting the PWM duty cycle of a switching element. When it is desired to obtain a larger output power or output torque, the conduction angle of the switching element is increased. However, increasing the conduction angle greatly increases the current flowing through the motor and the switching element, and there is no doubt a need to increase the cost of hardware for a power tool requiring a larger output power or output torque.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, an object of the present invention is to propose an electric tool that can satisfy a user's desire for output power, and a control method thereof.
According to a first aspect of the present invention, there is provided a power tool comprising:
A battery pack;
The brushless motor comprises a stator winding, a rotor and a position detection unit for detecting a position signal of the brushless motor;
A control assembly electrically connecting the battery pack and the brushless motor, including a plurality of switching elements configured to perform switching control according to a PWM duty cycle and/or a conduction angle to drive the brushless motor; the control component is configured to calculate the actual rotating speed of the brushless motor according to the position signal, and the brushless motor is enabled to maintain the target rotating speed by selectively adjusting the PWM duty ratio and the conduction angle of the switching element;
The control component presets a parameter threshold and a conduction angle reference value, the control component is configured to detect parameters representing the load of the brushless motor, and when the parameters exceed the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value.
In one embodiment, after the parameter exceeds the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value until the battery pack stops supplying power to the brushless motor or the PWM duty cycle of the switching element drops to a PWM duty cycle preset value preset by the control component, and the control component controls the conduction angle not to exceed the conduction angle reference value.
In one embodiment, after the parameter exceeds the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value, and if the parameter does not exceed the parameter threshold, the control component controls the conduction angle in a manner that the conduction angle reference value can be exceeded.
In one embodiment, the brushless motor is a three-phase brushless dc motor, the conduction angle initial value of the three-phase brushless dc motor is 120 °, and the conduction angle reference value is the conduction angle initial value.
In one embodiment, when the actual rotation speed of the brushless motor is lower than the target rotation speed, the control component preferentially adjusts the PWM duty ratio of the switching element and then adjusts the conduction angle of the switching element; when the actual rotating speed is higher than the target rotating speed, the control component preferentially adjusts the conduction angle of the switching element and then adjusts the PWM duty ratio of the switching element.
In one embodiment, the parameter indicative of the brushless motor load is the brushless motor phase current.
In one embodiment, the maximum output torque of the power tool is T max, and the maximum current allowed by the control assembly is I max, wherein T max/Imax is equal to or greater than 0.6 N.m/A.
In one embodiment, the brushless motor has a power density greater than 16W/cm 3.
In one embodiment, the control assembly may also adjust the lead angle of the switching element, the control assembly maintaining the adjustment of the lead angle when the parameter exceeds the parameter threshold.
According to a second aspect of the present invention, there is provided a control method of an electric power tool, the electric power tool including:
A battery pack;
the brushless motor comprises a position detection unit for detecting a position signal of the brushless motor;
the control component comprises a plurality of switching elements for driving the brushless motor, the switching elements are configured to perform switching actions according to PWM duty ratio and/or conduction angle so as to drive the brushless motor, and the control component presets a parameter threshold value and a conduction angle reference value;
The control method comprises the following steps:
the control component detects parameters representing the load of the brushless motor;
the control component calculates the actual rotating speed of the brushless motor according to the position signal, and enables the brushless motor to maintain the target rotating speed by selectively adjusting the PWM duty ratio and/or the conduction angle of the switching element;
When the parameter exceeds the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value.
In one embodiment, after the parameter exceeds the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value until the battery pack stops supplying power to the brushless motor or the PWM duty cycle of the switching element drops to a PWM duty cycle preset value preset by the control component, and the control component controls the conduction angle not to exceed the conduction angle reference value.
In one embodiment, after the parameter exceeds the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value, and if the parameter does not exceed the parameter threshold, the control component controls the conduction angle in a manner that the conduction angle reference value can be exceeded.
In one embodiment, when the actual rotation speed of the brushless motor is lower than the target rotation speed, the control component preferentially adjusts the PWM duty ratio of the switching element and then adjusts the conduction angle of the switching element; when the actual rotating speed is higher than the target rotating speed, the control component preferentially adjusts the conduction angle of the switching element and then adjusts the PWM duty ratio of the switching element.
According to the invention, when the parameter exceeds the parameter threshold, the conduction angle is controlled not to exceed the conduction angle reference value, so that the reduction of the operation efficiency caused by long-time high motor current is avoided.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural view of an impact tool according to a first embodiment of the present invention.
Fig. 2 is a circuit block diagram of a control system for an impact tool according to an embodiment of the present invention.
Fig. 3A is a schematic diagram of a power inverter module according to an embodiment of the invention.
Fig. 3B is a driving sequence diagram of an initial conduction angle according to an embodiment of the invention.
Fig. 4 is a driving sequence diagram for increasing the conduction angle according to an embodiment of the invention.
Fig. 5 is a flow chart of a control method according to a first embodiment of the present invention.
Detailed Description
In order to solve the above-mentioned problems, embodiments of the present invention provide an electric power tool and a control method thereof. Embodiments of the present invention are described in detail below with reference to the accompanying drawings.
The technical solutions in the embodiments of the present invention are clearly and completely described, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It will be understood that when an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Example 1
Fig. 1 is a schematic view showing the structure of an impact tool according to a first embodiment of the present invention. It should be appreciated that embodiments of the present invention may also be applied to grinding tools, cutting tools, cleaning tools, garden tools, etc.
The impact tool 10 includes: a housing 11, a motor 12, an output unit 13, a control assembly 14, an impact mechanism 15, a battery pack 16, and a trigger switch 17. The motor 12 is disposed in an upper cavity of the housing 11, including rotor and stator windings. The control assembly 14 is disposed in a cavity in the lower portion of the handle and includes a motor control circuit 141 for controlling the drive of the motor 12. To prevent overload damage to the electronics on the control assembly 14, in this embodiment, the maximum current/I max that the control assembly 14 allows to pass is less than 250A. Preferably, the maximum current allowed to pass by the control assembly 14 is 200A. The battery pack 16 is detachably mounted on the housing 11, or may be provided in the housing 11 in a built-in manner. The impact mechanism 15 includes an impact unit mainly formed of a hammer and an anvil, and when the work load of the output unit 13 increases to a certain extent, the hammer and the anvil are changed from integral rotation to relative rotation with an impact action, so that the hammer repeatedly applies an impact force in the radial direction of the anvil. A trigger switch 17 may be provided at a location on the handle of the housing 11 for providing user input to the control assembly 14 so that the control assembly 14 controls the operation of the impact tool 100 in accordance with the user input instructions. The trigger switch 17 may be a displacement sensor based trigger switch, or other forms of switches may be used, such as a touch sensor, a capacitive sensor based switch, etc.
In this embodiment, the motor 12 is a three-phase brushless DC motor with a power density of not less than 16W/cm 3. Preferably, the motor has a volume of about 36.36cm 3 and an output power of 600W at the maximum efficiency point, and the three-phase brushless DC motor has a power density of 16.5W/cm 3. Where the maximum efficiency point is generally referred to as when the output power/input power is at a maximum. Compared with the conventional motor, the three-phase brushless direct current motor adopted in the embodiment has higher power density, and can output higher torque under the condition of the same current.
The output unit 13 may be equipped with different working heads, such as drills or bits, according to different working requirements. A speed reducing mechanism is further arranged between the motor 12 and the output unit 13, preferably, the speed reducing ratio of the speed reducing mechanism is 55:1, and the maximum torque T max output by the output unit 13 is not lower than 140 N.m under the driving of the motor 12. Preferably, the maximum torque T max output by the output unit 13 is 150n·m.
Fig. 2 is a block circuit diagram of a control system 140 of the impact tool of the present embodiment. The position detection unit 142 is typically mounted on the motor 12 for detecting a position signal of a rotor on the motor 12 and transmitting the position signal to the main control unit 143. The position detecting unit 142 in this embodiment adopts a hall sensor, and may adopt other types of position sensors such as a magneto-electric sensor and a photo-electric sensor. Compared with the motor without the position detection unit, the motor with the position detection unit is adopted in the embodiment, so that the motor with the position detection unit has larger and more accurate conduction angle and lead angle adjustment interval.
The motor control circuit 141 includes a power inverter unit 145, a main control unit 143, a driving module 144, and a sampling module 146. The sampling module 146 is used to collect a parameter indicative of the load of the motor 12 and communicate this parameter to the main control unit 143. The main control unit 143 is typically a Central Processing Unit (CPU) or other form of processing unit having data processing capabilities and/or instruction execution capabilities. The main control unit 143 receives the position signal from the position detection unit 142, and calculates the actual rotational speed of the motor 12 based on the position signal. The main control unit 143 presets a target rotational speed, and it should be understood that the target rotational speed is preset in the main control unit 143 in an unmodified manner, or may be preset in the main control unit 143 in a modifiable or selectable manner, and is individually set by the user according to the working habit. In this embodiment, the parameter characterizing the motor load is the current flowing through the motor 12. Preferably, the current is a phase current of the motor 12. It should be appreciated that the parameters characterizing the motor load may also be other parameters such as motor voltage, motor speed, operating volume, vibration, etc.
Fig. 3A is a schematic diagram of the power inverter 145 of the present embodiment. The power inverter 145 is a three-phase bridge inverter circuit, which includes six switching elements, and is divided into an upper bridge arm and a lower bridge arm. The six switching elements include three upper side switches and three lower side switches, which are driven by high driving signals UH, VH and WH and low driving signals UL, VL and WL, respectively. The source of the upper switch of each phase is connected to the drain of the lower switch to output a power signal for driving the motor 12. The main control unit 143 determines the PWM duty ratio and the conduction angle of the switching element in the power inverter unit 145 based on the signal feedback, and the switching element performs switching control based on the PWM duty ratio and the conduction angle, thereby controlling the rotation speed of the motor 12.
In a conventional constant-speed electric tool, the rotation speed of a motor is regulated by adopting a mode of regulating the PWM duty ratio of a switching element, the duty ratio in each phase of conduction time determines the duration of voltage supplied to the motor, and the longer the duty ratio is, the greater the duration of voltage supplied to the motor in the conduction time is. The actual rotation speed of the motor can be obtained through calculation according to the position signal measured by the position detection unit, and if the actual rotation speed of the motor is lower than the target rotation speed, the main control module controls the PWM duty ratio to be increased to increase the rotation speed of the motor. However, after the PWM duty cycle increases to 100% of the maximum value, if the actual motor speed still does not reach the target speed, the voltage duration cannot be increased continuously within the on time, so that the motor speed cannot be further increased by increasing the PWM duty cycle, which results in that the impact tool cannot reach the desired output.
Fig. 3B shows a driving sequence diagram of the power inverting unit 145 when the PWM duty ratio of the driving switching element is 100%, the conduction angle of each phase of the three-phase brushless dc motor is 120 ° of the initial value of the conduction angle, and the lead angle is 0 °. In this embodiment, in order to further increase the rotation speed of the impact tool to achieve the desired target rotation speed, as shown in fig. 4, the conduction angles of two adjacent phases are partially overlapped in the phase change process by increasing the conduction angle, which is helpful to increase the total voltage supplied to the motor, so that the rotation speed of the motor can be further increased.
Specifically, when the actual rotation speed is smaller than the target rotation speed and the motor rotation speed needs to be increased, the PWM duty ratio is preferentially increased to perform speed increase. And when the PWM duty ratio reaches the maximum value, increasing the conduction angle to increase the speed. When the actual rotation speed is larger than the target rotation speed, namely the motor rotation speed needs to be reduced, the conduction angle is preferentially reduced to reduce the speed. And when the conduction angle reaches an initial value, reducing the PWM duty ratio to reduce the speed. In this embodiment, the initial value of the conduction angle of the three-phase brushless dc motor is 120 ° and the maximum value is 180 °. When the conduction angle is increased or decreased, the main control module preferably increases or decreases the conduction angle in fixed increment and fixed frequency according to the relation between the actual rotation speed and the target rotation speed, so that the actual rotation speed reaches the target rotation speed.
However, in the above-mentioned technical solution, when the user uses the impact tool to perform the fastening operation, as the fastening depth increases, the motor load increases, and the conduction angle continuously increases under the increasing speed requirement, resulting in the motor current being maintained at a high level for a long time. This would bring about the following problems: 1. the large current flowing through the motor and the switching element can cause the tool to run to generate a large amount of heat, and the tool quickly enters overheat protection, so that a user cannot continuously work; 2. if the capacity of carrying large current and the heat dissipation capacity of the motor and the switching element are improved from the perspective of hardware, the hardware cost is certainly increased; 3. when the load is large, the conduction angle increases, and the torque generated by the unit current decreases.
In order to solve the above-mentioned problem, in the present embodiment, a current threshold and a conduction angle reference value are preset in the main control unit 143, the sampling module 146 compares the motor phase current measured in real time with the current threshold, and when the motor phase current exceeds the current threshold, the main control unit 143 controls the conduction angle not to exceed the conduction angle reference value. Preferably, the main control unit 143 controls the conduction angle to be the conduction angle reference value. The conduction angle reference value may be 120 ° of the initial conduction angle value of the three-phase brushless dc motor, or may be 125 °, 130 ° or the like close to the initial conduction angle value. When the motor phase current exceeds the current threshold, preferably, the main control unit adopts a slope adjustment mode to reduce the conduction angle to the conduction angle reference value, so that the speed jump caused by abrupt change of the conduction angle can be avoided, and the user experience is influenced.
Further, before the battery pack stops supplying power to the motor, it means that the user has not completely finished the last fastening operation, and at this time, the main control unit continuously controls the conduction angle not to exceed the conduction angle reference value. The battery pack stops supplying power to the motor, typically by releasing the trigger switch with the user's finger. Or the main control unit also presets a preset PWM duty cycle value, for example, 60%, and continuously controls the conduction angle not to exceed the conduction angle reference value until the PWM duty cycle falls below the preset value.
When the motor phase current exceeds the current threshold, the main control unit controls the conduction angle not to exceed the conduction angle reference value, and if the motor phase current is lower than the current threshold, the main control unit resumes normal control of the conduction angle, that is, the main control unit controls the conduction angle in such a way that the conduction angle can exceed the conduction angle reference value.
By means of the scheme, when the motor current rises to exceed the current threshold value, the main control unit controls the conduction angle not to exceed the conduction angle reference value, and the impact tool can be prevented from entering an overheat protection state too early due to large current. And when the motor current rises to exceed the current threshold value and the conduction angle is controlled to be not more than the conduction angle reference value, the efficiency of generating torque by the unit current is improved when the load of the impact tool is large. Meanwhile, when the current of the motor does not exceed the current threshold value, the impact tool is kept at the target rotating speed by increasing the conduction angle, so that the working efficiency of the impact tool when the load is small is improved.
Example two
The difference from the first embodiment described above is that the main control unit further adjusts the lead angle of the switching element in addition to increasing the conduction angle under the need of a rise speed. Specifically, a functional relationship, such as a linear relationship, of the lead angle and the current is preset in the main control unit. As the load increases, the motor current increases, and the lead angle is set by the main control unit according to a preset functional relationship. Therefore, the problem of inaccurate commutation time after load increase can be further solved. Preferably, the main control unit maintains the adjustment of the lead angle as a function of the lead angle and the current when the motor current exceeds the current threshold. Of course, the control of the conduction angle may be similar to the control of the conduction angle described above, and the main control unit may control the lead angle not to exceed a predetermined value when the motor current exceeds the current threshold.
Fig. 5 is a flow chart of a control method according to the first embodiment.
Step S201: the magnitude of the current of the brushless motor is detected.
Step S202: calculating the actual rotating speed of the brushless motor and comparing the actual rotating speed with the target rotating speed; when the rotation speed is lower than the target rotation speed, the process proceeds to step S203; otherwise, the process advances to step S204.
Step S203: judging whether the current PWM duty cycle is the maximum value or not; if yes, increasing the conduction angle; otherwise, the PWM duty cycle is increased.
Step S204: judging whether the current conduction angle is the minimum value or not; if yes, reducing the PWM duty cycle; conversely, the conduction angle is reduced.
Step S205: comparing the motor current with a current threshold; when above the threshold, go to step S206; otherwise, the process advances to step S202.
Step S206: the conduction angle is controlled not to exceed the conduction angle reference value.
By repeatedly executing the series of the above-described regulation of S201 to S206, the PWM duty ratio and/or the conduction angle are selectively increased when the rotational speed needs to be increased. And detecting the motor current at the same time, and controlling the conduction angle to be not more than a conduction angle reference value after the motor current exceeds a current threshold value.
In addition, it should be noted that the combination of the technical features described in the present invention is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present invention may be freely combined or combined in any manner unless contradiction occurs between them.
It should be noted that the above-mentioned embodiments are merely examples of the present invention, and it is obvious that the present invention is not limited to the above-mentioned embodiments, and many similar variations are possible. All modifications attainable or obvious from the present disclosure set forth herein should be deemed to be within the scope of the present disclosure.
It should be understood that the first, second, etc. qualifiers mentioned in the embodiments of the present invention are only used for more clearly describing the technical solutions of the embodiments of the present invention, and should not be used to limit the protection scope of the present invention.
The foregoing is merely illustrative of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (13)
1. A power tool, comprising:
A battery pack;
the brushless motor comprises a stator winding, a rotor and a position detection unit for detecting a position signal of the brushless motor;
A control assembly electrically connecting the battery pack and the brushless motor, including a plurality of switching elements configured to perform switching control according to a PWM duty cycle and/or a conduction angle to drive the brushless motor; the control component is configured to calculate the actual rotating speed of the brushless motor according to the position signal, and enable the brushless motor to maintain the target rotating speed by selectively adjusting the PWM duty ratio and the conduction angle of the switching element;
the brushless motor load control device is characterized in that the control component presets a parameter threshold value and a conduction angle reference value, the control component is configured to detect a parameter representing the brushless motor load, and when the parameter exceeds the parameter threshold value, the control component controls the conduction angle not to exceed the conduction angle reference value.
2. The power tool according to claim 1, wherein when the parameter exceeds the parameter threshold, the control module controls the conduction angle not to exceed the conduction angle reference value until the battery pack stops supplying power to the brushless motor or the PWM duty cycle of the switching element drops to a PWM duty cycle preset value preset by the control module.
3. The power tool according to claim 1, wherein the control module controls the conduction angle in such a manner that the conduction angle reference value is exceeded if the parameter does not exceed the parameter threshold value after the parameter exceeds the parameter threshold value.
4. The electric power tool according to claim 1, wherein the brushless motor is a three-phase brushless dc motor, a conduction angle initial value of the three-phase brushless dc motor is 120 °, and the conduction angle reference value is the conduction angle initial value.
5. The power tool according to claim 1, wherein when the actual rotational speed of the brushless motor is lower than the target rotational speed, the control module preferentially adjusts the PWM duty cycle of the switching element, and then adjusts the conduction angle of the switching element; when the actual rotating speed is higher than the target rotating speed, the control component preferentially adjusts the conduction angle of the switching element and then adjusts the PWM duty ratio of the switching element.
6. The power tool of claim 1, wherein the parameter indicative of the brushless motor load is brushless motor phase current.
7. The power tool of claim 1, wherein the maximum output torque of the power tool is T max, and the maximum current allowed to pass by the control assembly is I max, wherein T max/Imax is greater than or equal to 0.6N-m/a.
8. The power tool of claim 1, wherein the brushless motor has a power density greater than 16W/cm 3.
9. The power tool of claim 1, wherein the control assembly is further operable to adjust the lead angle of the switching element, the control assembly maintaining the adjustment of the lead angle when the parameter exceeds the parameter threshold.
10. A control method of an electric tool, characterized in that the electric tool includes:
A battery pack;
a brushless motor including a position detection unit that detects a position signal of the brushless motor;
a control assembly including a plurality of switching elements driving the brushless motor, the switching elements configured to perform switching operation according to a PWM duty cycle and/or a conduction angle to drive the brushless motor, the control assembly presetting a parameter threshold and a conduction angle reference value;
the control method comprises the following steps:
a control component detects a parameter representing the load of the brushless motor;
A control component calculates the actual rotating speed of the brushless motor according to the position signal, and enables the brushless motor to maintain the target rotating speed by selectively adjusting the PWM duty ratio and/or the conduction angle of the switching element;
When the parameter exceeds the parameter threshold, the control component controls the conduction angle not to exceed the conduction angle reference value.
11. The control method according to claim 10, wherein when the parameter exceeds the parameter threshold, the control module controls the conduction angle not to exceed the conduction angle reference value until the battery pack stops supplying power to the brushless motor or the PWM duty cycle of the switching element drops to a PWM duty cycle preset value preset by the control module.
12. The control method according to claim 10, wherein the control module controls the conduction angle in such a manner that the conduction angle reference value is exceeded if the parameter does not exceed the parameter threshold value after the control module controls the conduction angle not to exceed the conduction angle reference value when the parameter exceeds the parameter threshold value.
13. The control method according to claim 10, wherein when the actual rotational speed of the brushless motor is lower than the target rotational speed, the control module preferentially adjusts the PWM duty ratio of the switching element, and then adjusts the conduction angle of the switching element; when the actual rotating speed is higher than the target rotating speed, the control component preferentially adjusts the conduction angle of the switching element and then adjusts the PWM duty ratio of the switching element.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211445223.XA CN118100696A (en) | 2022-11-18 | 2022-11-18 | Electric tool and control method thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211445223.XA CN118100696A (en) | 2022-11-18 | 2022-11-18 | Electric tool and control method thereof |
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| CN118100696A true CN118100696A (en) | 2024-05-28 |
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| CN202211445223.XA Pending CN118100696A (en) | 2022-11-18 | 2022-11-18 | Electric tool and control method thereof |
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| CN (1) | CN118100696A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118554846A (en) * | 2024-07-29 | 2024-08-27 | 浙江德硕科技股份有限公司 | Motor torque control method and system for multifunctional garden operation device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118554846A (en) * | 2024-07-29 | 2024-08-27 | 浙江德硕科技股份有限公司 | Motor torque control method and system for multifunctional garden operation device |
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