Power tool and control method thereof

Abstract

The application discloses an electric tool and a control method thereof. The electric tool comprises a functional part, a motor assembly comprising a first motor and a second motor, at least one of the first motor and the second motor driving the functional part to work, and a power supply device connected with the motor assembly and supplying power for at least the motor assembly. There is a transmission relationship between the first motor and the second motor, and the first motor drives the second motor to rotate when rotating. The electric tool further comprises a controller connected with the motor assembly, and the controller is configured to control the second motor to start based on the counter electromotive force of the second motor after the first motor starts. The scheme can effectively improve the starting success rate of the motor of the electric tool and ensure the smooth work of the tool.

Description

Technical Field

[0001] This application relates to the field of power tool technology, specifically to a power tool and its control method. Background Technology

[0002] Power tools, widely used in various scenarios such as construction and landscaping, for cutting, fastening, and impact, are mostly powered by electricity. These tools contain a motor controlled by a controller. To better adapt to changing working conditions, some power tools now feature dual motors.

[0003] This section provides background information related to this application, which is not necessarily prior art. Summary of the Invention

[0004] One object of this application is to solve or at least alleviate some or all of the aforementioned problems. Therefore, one object of this application is to provide an electric tool and a control method thereof.

[0005] To achieve the above objectives, this application adopts the following technical solution:

[0006] An electric tool includes: a functional component; a motor assembly including a first motor and a second motor, at least one of the first motor and the second motor driving the functional component to operate; a power supply device connected to the motor assembly and supplying power to at least the motor assembly; wherein there is a transmission relationship between the first motor and the second motor, and the first motor drives the second motor to rotate when it rotates; the electric tool further includes: a controller connected to the motor assembly, the controller being configured to control the second motor to start based on the back electromotive force of the second motor after the first motor starts.

[0007] In some embodiments, the second motor is a sensorless brushless motor.

[0008] In some embodiments, the controller is configured to control the first motor to start when a signal to start a power tool is received.

[0009] In some embodiments, the controller is configured to start the second motor based on the back electromotive force of the second motor after the first motor has started and a first preset time has elapsed.

[0010] In some embodiments, the first preset duration is greater than or equal to 0.1s and less than or equal to 2s.

[0011] In some embodiments, the controller is configured to start the second motor based on the back electromotive force of the second motor after the first motor starts and the speed of the first motor reaches a first speed threshold.

[0012] In some embodiments, the first speed threshold is greater than or equal to 10 RPM or greater than or equal to 10% of the no-load speed of the first motor.

[0013] In some embodiments, the controller is configured to determine the rotor position of the second motor based on the extreme value of the back electromotive force of the second motor, or based on the relative relationship between the back electromotive force of the second motor and the zero potential, and control the second motor to start.

[0014] In some embodiments, the controller includes a first controller and a second controller, the first controller being connected to a first motor and the second controller being connected to a second motor; the first controller is configured to control the first motor to start when a signal to start a power tool is received; the second controller is configured to control the second motor to start based on the back electromotive force of the second motor after the first motor has started.

[0015] A control method for an electric tool includes: starting a first motor of the electric tool; a controller of the electric tool controlling the second motor to start based on the back electromotive force of the second motor of the electric tool after the first motor starts; there is a transmission relationship between the first motor and the second motor, and the rotation of the first motor drives the second motor to rotate.

[0016] An electric tool includes: a functional component; a motor assembly including a first motor and a second motor, at least one of the first motor and the second motor driving the functional component to operate; a power supply device connected to the motor assembly and supplying power to at least the motor assembly; wherein the first motor and the second motor drive the same output shaft; the electric tool further includes: a controller connected to the motor assembly, the controller being configured to control the first motor to stop when the first motor parameter of the first motor exceeds a first protection threshold, and to control the second motor to stop when the second motor parameter of the second motor exceeds a second protection threshold after the first motor parameter exceeds the first protection threshold; the first protection threshold and the second protection threshold are not equal.

[0017] In some embodiments, the first motor parameters include a first stall parameter of the first motor, and the first protection threshold includes a first stall threshold; the second motor parameters include a second stall parameter of the second motor, and the second protection threshold includes a second stall threshold.

[0018] In some embodiments, the first motor parameters include a first overcurrent parameter of the first motor, and the first protection threshold includes a first overcurrent threshold; the second motor parameters include a second overcurrent parameter of the second motor, and the second protection threshold includes a second overcurrent threshold.

[0019] In some embodiments, the first stall parameter is the first commutation duration of the first motor, and the first stall threshold is the first duration threshold; the second stall parameter is the second commutation duration of the second motor, and the second stall threshold is the second duration threshold; the controller is configured to control the first motor to stop when the first commutation duration exceeds the first duration threshold, and to control the second motor to stop when the second commutation duration exceeds the second duration threshold after the first commutation duration exceeds the first duration threshold; the first duration threshold and the second duration threshold are not equal.

[0020] In some embodiments, when the speed ratio of the first motor to the second motor is n:1, the ratio of the first duration threshold to the second duration threshold is not equal to 1:n.

[0021] In some embodiments, the first overcurrent parameter is the first current of the first motor, and the first overcurrent threshold is the first current threshold; the second overcurrent parameter is the second current of the second motor, and the second overcurrent threshold is the second current threshold; the controller is configured to control the first motor to stop when the first current exceeds the first current threshold, and to control the second motor to stop when the second current exceeds the second current threshold after the first current exceeds the first current threshold; the first current threshold and the second current threshold are not equal.

[0022] In some embodiments, when the torque ratio of the first motor to the second motor is n:1, the ratio of the first current threshold to the second current threshold is not equal to n:1.

[0023] In some embodiments, the first overcurrent parameter is a calculated value of one or more of the first output torque, first current, and first demagnetization time of the first motor; the second overcurrent parameter is a calculated value of one or more of the second output torque, second current, and second demagnetization time of the second motor.

[0024] In some embodiments, when the ratio of the first motor parameter to the second motor parameter is n:1, the ratio of the first protection threshold to the second protection threshold is not equal to n:1.

[0025] In some embodiments, the power tool further includes a drive device, comprising a first drive circuit and a second drive circuit, wherein the first drive circuit is connected between the power supply device and the first motor, and the second drive circuit is connected between the power supply device and the second motor.

[0026] In some embodiments, the first protection threshold has different values ​​depending on the capacity or voltage of the power supply device; and / or, the second protection threshold has different values ​​depending on the capacity or voltage of the power supply device.

[0027] In some embodiments, the first protection threshold and / or the second protection threshold are dynamic thresholds and their values ​​correspond to the current current or voltage of the motor component.

[0028] In some embodiments, the controller includes a first controller and a second controller. The first controller is connected to the first motor via a first drive circuit, and the second controller is connected to the second motor via a second drive circuit. The first controller is configured to control the first motor to stop when the first motor parameter of the first motor exceeds a first protection threshold. The second controller is configured to control the second motor to stop when the second motor parameter of the second motor exceeds a second protection threshold after the first motor parameter exceeds the first protection threshold. The first protection threshold and the second protection threshold are not equal.

[0029] An electric tool includes: a functional component; a motor assembly including a first motor and a second motor, at least one of the first motor and the second motor driving the functional component to operate; a power supply device connected to the motor assembly and supplying power to at least the motor assembly; wherein the first motor and the second motor drive the same output shaft; the electric tool further includes: a controller connected to the motor assembly, the controller being configured to control the first motor to stop when the first motor parameter of the first motor exceeds a first protection threshold, and to control the second motor to stop after the first motor parameter exceeds the first protection threshold and a second preset time has elapsed.

[0030] A control method for an electric tool includes: a controller of the electric tool controlling the first motor to stop when the parameters of the first motor of the first motor of the electric tool exceed a first protection threshold; the controller controlling the second motor to stop when the parameters of the second motor of the electric tool exceed a second protection threshold after the parameters of the first motor exceed the first protection threshold; the first protection threshold and the second protection threshold are not equal, and the first motor and the second motor drive the same output shaft.

[0031] The advantages of this application are: it adopts a time-sharing start method to realize the start of dual motors. Relying on the transmission relationship between the first and second motors, after controlling the start of the first motor, the second motor is controlled to start based on the back electromotive force generated by the second motor being driven by the first motor. This solves the problem of mutual interference between the two motors during the start-up process, and there is no requirement for signal synchronization for simultaneous start-up. This improves the start-up success rate of power tools with multiple motors and ensures their smooth operation. Attached Figure Description

[0032] Figure 1 This is a perspective view of a power tool as an embodiment of this application from one viewpoint;

[0033] Figure 2 yes Figure 1 A stereoscopic view of the power tool shown from another perspective;

[0034] Figure 3 yes Figure 1 A perspective view of the motor assembly in one embodiment of the power tool shown;

[0035] Figure 4 yes Figure 1 A perspective view of the motor assembly in another embodiment of the power tool shown;

[0036] Figure 5 yes Figure 1 The diagram shows the electrical control schematic of the power tool.

[0037] Figure 6 yes Figure 1 Another electrical control schematic diagram of the power tool shown;

[0038] Figure 7 This is a control flowchart of an electric tool as an embodiment of this application;

[0039] Figure 8 This is a control flowchart of an electric tool as another embodiment of this application.

[0040] Caption:

[0041] 100. Power tools;

[0042] 10. Housing; 20. Functional components; 30. Operating components; 40. Motor assembly; 50. Power supply unit; 60. Controller; 70. Drive unit;

[0043] 41. First motor; 42. Second motor; 43. Clutch; 61. First controller; 62. Second controller; 71. First drive circuit; 72. Second drive circuit; 210. Output shaft. Detailed Implementation

[0044] Before explaining any implementation of this application in detail, it should be understood that this application is not limited to its application to the structural details and component arrangements set forth in the following description or shown in the above drawings.

[0045] In this application, the terms "comprising," "including," "having," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0046] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this application generally indicates that the preceding and following related objects have an "and / or" relationship.

[0047] In this application, the terms "connection," "combination," "coupling," and "installation" can refer to direct connection, combination, coupling, or installation, or indirect connection, combination, coupling, or installation. For example, a direct connection refers to two parts or components being connected together without the need for an intermediary, while an indirect connection refers to two parts or components each being connected to at least one intermediary, with the connection achieved through the intermediary. Furthermore, "connection" and "coupling" are not limited to physical or mechanical connections or couplings, but can also include electrical connections or couplings.

[0048] In this application, those skilled in the art will understand that relative terms (e.g., “about,” “approximately,” “basically,” etc.) used in conjunction with quantities or conditions are to include the values ​​and have the meaning indicated by the context. For example, such relative terms include at least the degree of error associated with the measurement of a particular value, tolerances associated with the particular value due to manufacturing, assembly, use, etc. Such terms should also be considered as disclosing a range defined by the absolute values ​​of the two endpoints. Relative terms may refer to a certain percentage (e.g., 1%, 5%, 10% or more) of the indicated value. Numerical values ​​not using relative terms should also be disclosed as specific values ​​with tolerances. Furthermore, “basically” when expressing relative angular relationships (e.g., substantially parallel, substantially perpendicular) may refer to a certain degree (e.g., 1 degree, 5 degrees, 10 degrees or more) added to or subtracted from the indicated angle.

[0049] In this application, those skilled in the art will understand that the function performed by a component can be performed by one component, multiple components, one part, or multiple parts. Similarly, the function performed by a part can also be performed by one part, one component, or a combination of multiple parts.

[0050] In this application, the directional terms "upper," "lower," "left," "right," "front," and "rear" are used to describe the orientation and positional relationships shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when an element is mentioned as being connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected through an intermediate element. It should also be understood that directional terms such as upper side, lower side, left side, right side, front side, and rear side not only represent positive orientation but can also be understood as lateral orientation. For example, "below" can include directly below, lower left, lower right, lower front, and lower rear.

[0051] In this application, the terms "controller," "processor," "central processing unit," "CPU," and "MCU" are used interchangeably. When using the unit "controller," "processor," "central processing unit," "CPU," or "MCU" to perform a specific function, unless otherwise stated, these functions may be performed by a single or multiple of the aforementioned units.

[0052] In this application, the terms "device," "module," or "unit" are used to describe devices that can be implemented in hardware or software to perform a specific function.

[0053] In this application, the terms “calculation,” “judgment,” “control,” “determine,” “identify,” etc., refer to the operation and process of a computer system or similar electronic computing device (e.g., controller, processor, etc.).

[0054] The technical solution proposed in this application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0055] Figure 1 An electric tool 100 is shown as one embodiment of this application. Figure 1 The power tool 100 shown is a circular saw. In other embodiments, the power tool 100 may also be a jigsaw, reciprocating saw, electric drill, impact wrench, or other types of handheld power tools, or a table saw, or an outdoor power equipment such as a lawnmower or snowplow. It is understood that the power tool 100 using the technical solution of this application is not limited to a circular saw, nor is it limited to the tool categories described above.

[0056] refer to Figure 1The power tool 100 includes a housing 10, functional components 20, and an operating component 30. The housing 10 forms the main body of the power tool 100, connecting or supporting the aforementioned components and providing a accommodating space to house or partially accommodate other components. The functional component 20 is the part of the power tool 100 that actually performs operations such as cutting, fastening, grinding, and impact. For example, in a circular saw, the functional component 20 is a circular saw blade; in other power tools 100, the functional component 20 can also be a chain, drill bit, etc. The operating component 30 is operated by the user to switch the power tool 100 between on / off states and can output corresponding start or stop signals. For example, the operating component 30 allows the user to start or stop the motor assembly 40 (described later) and outputs a start signal indicating that the motor assembly 40 is expected to start operating or a stop signal indicating that the motor assembly 40 is expected to stop operating to the controller 60 (described later). In some cases, the operating component 30 may also have more diverse functions, such as allowing the user to adjust the motor speed or perform other functions. In some embodiments, the operating element 30 can be a mechanical switch such as a trigger. It is understood that the start and stop of the power tool 100 can also be achieved in other ways besides setting the operating element 30 on the tool body. For example, in some embodiments, the user can also transmit signals to the power tool 100 through external devices such as mobile phones and tablets to start or stop the power tool 100.

[0057] refer to Figures 2 to 5 The power tool 100, in addition to the housing 10, functional components 20, and operating components 30, also includes a motor assembly 40, a power supply device 50, and a controller 60. The motor assembly 40 is the prime mover of the power tool 100. When the motor shaft of the motor assembly 40 rotates, it directly or indirectly drives the functional components 20 mounted on the output shaft 210. In this application, the power tool 100 is equipped with at least two motors; that is, the motor assembly 40 includes at least a first motor 41 and a second motor 42. The first motor 41 and the second motor 42 drive the same output shaft 210, and there is a transmission relationship between the first motor 41 and the second motor 42. In other words, when the first motor 41 rotates, it can drive the second motor 42 to rotate.

[0058] Figure 3 An optional structure of the motor assembly 40 is shown, wherein the first and second motors 41 and 42 are internal rotor motors and the motor shafts of the first and second motors 41 and 42 are parallel to the output shaft 210. Power transmission can be achieved between the motor shaft and the output shaft 210 by means of a gear set. Figure 4Another optional structure of the motor assembly 40 is shown, in which the first and second motors 41 and 42 are internal rotor motors, and the motor shafts of the first and second motors 41 and 42 and the aforementioned output shaft 210 are collinear. A clutch 43 may also be provided between the first and second motors 41 and 42. The clutch 43 has a first state that allows power transmission between the first and second motors 41 and 42 and a second state that prevents power transmission between the first and second motors 41 and 42. The clutch 43 can be mechanical or electronic. The following text mainly describes the technical solution with the motor assembly 40 including the first motor 41 and the second motor 42. At least one of the first motor 41 and the second motor 42 can drive the functional component 20 to perform operations such as cutting, fastening, grinding, and impact. The following text mainly describes the scenario where both the first motor 41 and the second motor 42 are working.

[0059] The power supply device 50 provides power to at least the motor assembly 40, and can also power other related components such as the controller 60. In some embodiments, the power supply device 50 is a battery pack that is detachably connected to the power tool 100. In other embodiments, the power supply device 50 can also be implemented using mains power or AC power in conjunction with a power adapter, transformer, rectifier, voltage regulator and other related circuits.

[0060] The controller 60 can be an MCU (Microcontroller Unit), ARM (Advanced Reduced Instruction Set Computing Machine), DSP (Digital Signal Processor), etc. By running the relevant program, the controller 60 can control the aforementioned motor assembly 40 to operate in the intended manner. (Reference) Figure 5 The power tool 100 also includes a drive unit 70 connected between the controller 60 and the motor assembly 40. After the controller 60 runs the motor control program, it can output control signals such as pulse-width modulation (PWM) signals to the drive unit 70. The drive unit 70 can convert the above control signals into drive signals that ultimately drive the motor to operate, and transmit the electrical energy provided by the power supply unit 50 to the motor assembly 40 through the DC bus.

[0061] In some embodiments, the drive device 70 includes a first drive circuit 71 connected between the controller 60 and the first motor 41, and a second drive circuit 72 connected between the controller 60 and the second motor 42. The first drive circuit 71 and the second drive circuit 72 may include a three-phase bridge circuit, which consists of three switching transistors as the upper half-bridge and three switching transistors as the lower half-bridge. In the first drive circuit 71, the upper half-bridge switching transistors Q1, Q3, and Q5 are respectively connected between the power supply terminal of the power supply device 50 and each phase coil of the first motor 41, while the lower half-bridge switching transistors Q2, Q4, and Q6 are respectively connected between each phase coil of the first motor 41 and the ground wire. The second drive circuit 72 is similar to the second motor 42. The switching transistors may be field-effect transistors or insulated-gate bipolar transistors. In other examples, the drive device 70 may also be an integrated drive chip, etc.

[0062] In addition, such as Figure 6 As shown, in some embodiments, there may be more than one controller 60 in hardware. For example, the power tool 100 may have a first controller 61 and a second controller 62, which interact with each other through electrical connections. The first controller 61 controls the operation of the first motor 41 and transmits a first control signal to a first drive circuit 71, which is connected between the first controller 61 and the first motor 41. The second controller 62 controls the operation of the second motor 42 and transmits a second control signal to the second drive circuit 72, which is connected between the second controller 62 and the second motor 42. In other embodiments, the first and second controllers 61 and 62 may also be dual controllers at the software level. For example, the first and second controllers 61 and 62 may be dual VCPUs mounted on the same hardware, or first and second control units designed in the program, including parallel processes or threads.

[0063] Following the previous text, since the controller 60 needs to make a preliminary judgment on the initial position of the motor rotor when starting the motor, and the power tool 100 is equipped with a first motor 41 and a second motor 42, and there is a transmission relationship between the first and second motors 41 and 42, the rotation of one motor will drive the rotation of the other motor. This will result in the rotor positions of the two motors affecting each other when the motor is started. To address this problem, in one embodiment, the controller 60 can control the first and second motors 41 and 42 to start simultaneously. In response to a start signal from the operating element 30 or other signals used to start the power tool 100, the controller 60 will simultaneously output corresponding control signals to the first drive circuit 71 corresponding to the first motor 41 and the second drive circuit 72 corresponding to the second motor 42. In some embodiments, the first controller 61 outputs a first control signal to the first drive circuit 71 to drive the first motor 41, and the second controller outputs a second control signal to the second drive circuit 72 to drive the second motor 42. The first and second controllers 61 and 62 synchronize their signals before outputting the control signals to ensure that the first and second motors 41 and 42 are started simultaneously. In another implementation, the controller 60 can also start the motor assembly 40 in a time-sharing manner, eliminating the need for signal synchronization and ensuring safe motor startup during off-peak hours.

[0064] In response to a start signal from the operating element 30 or other signals used to start the power tool 100, the controller 60 first controls the first motor 41 to start, and then controls the second motor 42 to start based on the back electromotive force generated by the second motor 42 driven by the first motor 41 after the first motor 41 starts. Specifically, the first motor 41 starts rotating after the controller 60 starts. The rotation of the rotor of the first motor 41 will drive the rotor of the second motor 42, which has not yet started, to rotate. The passive rotation of the rotor of the second motor 42 will generate an electromagnetic induction phenomenon with the stator winding of the second motor 42, generating a back electromotive force. The controller 60 will control the second motor 42 to start after the first motor 41 starts based on the back electromotive force of the second motor 42. It should be noted that in this embodiment, the second motor 42 can be a sensorless brushless motor, which does not have a position sensor such as a Hall sensor that can directly detect the rotor position. Therefore, the controller 60 controls its start by detecting the back electromotive force of the second motor 42. Of course, if the second motor 42 has a position sensor, the controller 60 can also use the above method as an alternative solution to start the second motor 42.

[0065] It is understood that the first motor 41 can be a sensorless brushless motor or a sensored brushless motor. Correspondingly, there are multiple possible implementations for the controller 60 to control the first motor 41 to start, and this application does not impose specific limitations on this. In some embodiments, the controller 60 can use a pulse injection method to estimate the initial rotor position of the first motor 41 and control its start. The controller 60 can perform pulse injection on each of the six electrical angle sectors of the first motor 41, that is, transmit corresponding pulse signals to the six switching transistors in the first drive circuit 71. Then, it detects the current response of the first motor 41 to the pulse injection and determines the initial rotor position of the first motor 41 based on the current response. The controller 60 can then control the start of the first motor 41 based on this initial rotor position. In other embodiments, the controller 60 can also use a high-frequency injection method to control the start of the first motor 41. In still other embodiments, the controller 60 can also control the start of the first motor 41 by capturing the edge of the Hall signal.

[0066] In some embodiments, after starting the first motor 41, the controller 60 can wait for a first preset time before detecting and controlling the second motor 42 to start based on the back electromotive force (EMF) of the second motor 42. Specifically, after the first motor 41 starts and the first preset time has elapsed, the first motor 41 continues to rotate and has reached a certain speed. The back EMF of the second motor 42, driven by the first motor 41, is also in a state that can be detected relatively accurately and used for start-up control. At this time, the controller 60 can estimate the rotor position of the second motor 42 based on the back EMF of the second motor 42 and control its start-up. If the first preset time is too short, the first and second motors 41 and 42 will interfere with each other, affecting the start-up of both. If it is too long, the first motor 41 will have a significant impact on the rotation of the second motor 42, making start-up control of the second motor 42 difficult. Therefore, a first preset time of appropriate value needs to be set. In some embodiments, the first preset time is greater than or equal to 0.1s and less than or equal to 2s.

[0067] In other embodiments, after starting the first motor 41, the controller 60 can detect the rotational speed of the first motor 41. Once the rotational speed of the first motor 41 reaches a first speed threshold, the controller then detects and controls the second motor 42 to start based on its back electromotive force (EMF). Specifically, after the first motor 41 starts and reaches the first speed threshold, the back EMF of the second motor 42, driven by the first motor 41, is also in a state that can be detected relatively accurately and used for start-up control. At this time, the controller 60 can estimate the rotor position of the second motor 42 based on its back EMF and control its start-up. In some embodiments, the first speed threshold is greater than or equal to 10 RPM or greater than or equal to 10% of the no-load speed of the first motor 41.

[0068] There are several possible implementations for the controller 60 to control the start-up of the second motor 42 based on the back electromotive force (EMF), and this application does not impose any specific limitations on this. In some embodiments, the controller 60 can detect the extreme values ​​of the back EMF of the second motor 42, that is, detect the maximum or minimum value of the back EMF of the second motor 42, and deduce the rotor position from the extreme value position of the back EMF of the second motor 42, and then perform start-up control. In other embodiments, the controller 60 can also detect the relative relationship between the back EMF of the second motor 42 and the zero-point potential, and deduce the rotor position from the zero-point position of the back EMF of the second motor 42, and then perform start-up control.

[0069] Following the preceding text, the power tool 100 is equipped with a first controller 61 and a second controller 62, which respectively control the starting of the first motor 41 and the second motor 42. In response to a start signal from the operating element 30 or other signals used to start the power tool 100, the first controller 61 first controls the first motor 41 to start, and then the second controller 62 controls the second motor 42 to start based on its back electromotive force. In some cases, after the first controller 61 runs the start procedure for the first motor 41 in response to a relevant start signal, it can notify the second controller 62 to begin running the start procedure for the second motor 62. In other cases, the first and second controllers 61 and 62 can spontaneously run the start procedures for the first and second motors 41 and 42 sequentially in response to relevant start signals. In some embodiments, the first controller 61 can control the first motor 41 to start and wait for a first preset time before notifying the second controller 62. Upon receiving the notification, the second controller 62 can then control the second motor 42 to start based on its back electromotive force. In other embodiments, the first controller 61 can notify the second controller 62 after controlling the first motor 41 to start and detecting that the speed of the first motor 41 has reached a first speed threshold. Upon receiving the notification, the second controller 62 can then control the second motor 42 to start based on the back electromotive force (EMF) of the second motor 42. In still other embodiments, the first controller 61 can notify the second controller 62 after controlling the first motor 41 to start. Upon receiving the notification, the second controller 62 waits for a first preset time or detects that the speed of the first motor 41 has reached the first speed threshold before controlling the second motor 42 to start based on the back EMF of the second motor 42. In yet another embodiment, the first controller 61 can control the first motor 41 to start after receiving a relevant start signal, and the second controller 62 can wait for a first preset time or detect that the speed of the first motor 41 has reached the first speed threshold before controlling the second motor 42 to start based on the back EMF of the second motor 42. It is understood that in the case of dual controllers, whether there is mutual notification between the controllers, and which controller 60 performs timing statistics or speed detection, is not the focus of this application and does not affect the scope of protection of this application.

[0070] Furthermore, this application does not limit the specific control method of the controller 60 to drive the motor to run after the motor starts. It can use a six-step commutation method to control the operation of the motor assembly 40, or it can use the FOC method to control the operation of the motor assembly 40. Of course, other motor control methods can also be adapted to be introduced.

[0071] Correspondingly, a control method for the power tool 100 is proposed and applied to the power tool 100 described above, with reference to... Figure 7 It illustrates the flow of the control method for the power tool 100, which may include the following steps:

[0072] S710, starts the first motor 41 of the power tool 100;

[0073] S720, the controller 60 of the power tool 100 controls the second motor 42 to start based on the back electromotive force of the second motor 42 of the power tool 100 after the first motor 41 starts; there is a transmission relationship between the first motor 41 and the second motor 42, and the first motor 41 drives the second motor 42 to rotate when it rotates.

[0074] Following on from the previous text, since the first and second motors 41 and 42 share the same power supply device 50, if the first and second motors 41 and 42 are simultaneously controlled to perform shutdown protection, the peak current during their shutdown protection will be superimposed on the bus, potentially damaging semiconductor components and interfering with the judgment of related control logic. To address these issues, the controller 60 can set different protection thresholds for different motors to achieve time-sharing shutdown protection for the motor assembly 40, thereby ensuring motor shutdown safety during peak periods.

[0075] The controller 60 can stop the first motor 41 when its parameters exceed a first protection threshold, and stop the second motor 42 when its parameters exceed a second protection threshold. The first and second protection thresholds are not numerically equal, and there is a time interval between when the first motor parameters exceed the first threshold and when the second motor parameters exceed the second threshold. It is assumed, for illustrative purposes, that the first motor parameters exceed the first protection threshold before the second motor parameters exceed the second protection threshold. However, it is understood that by adjusting the values ​​of the first and second protection thresholds, either the first motor 41 or the second motor 42 can be stopped first, without affecting the scope of protection of this application.

[0076] It should be noted that the motor parameters of the first and second motors 41 and 42 have multiple different parameter types, and the protection thresholds also have multiple different threshold types. However, there is a corresponding relationship between the two; that is, the corresponding protection threshold is used to determine whether the corresponding motor parameter exceeds the limit. Furthermore, in the above scheme, the first and second motor parameters that are compared and judged sequentially should be of the same parameter type. That is, it is not that the first motor parameter of one parameter type is first judged to see if it exceeds its corresponding first protection threshold, and then the second motor parameter of another parameter type is judged to see if it exceeds its corresponding second protection threshold.

[0077] In some embodiments, the first motor parameters include a first stall parameter, and the first protection threshold includes a corresponding first stall threshold. Conversely, the second motor parameters include a second stall parameter, and the second protection threshold includes a corresponding second stall threshold. The first and second stall thresholds are not numerically equal. The controller 60 will first detect that the first stall parameter of the first motor 41 exceeds the first stall threshold and control the first motor 41 to stop. Then, it will detect that the second stall parameter of the second motor 42 exceeds the second stall threshold and control the second motor 42 to stop.

[0078] In some embodiments, the aforementioned stall parameters are commutation durations. The first stall parameter is the first commutation duration of the first motor 41, the first stall threshold is the first duration threshold, the second stall parameter is the second commutation duration of the second motor 42, and the second stall threshold is the second duration threshold. The ratio of the commutation durations of the two motors is related to their rotational speeds. If the speed ratio of the first and second motors 41 and 42 driving the same output shaft 210 is n:1, or in other words, the ratio of the transmission ratio of the first motor 41 to the output shaft 210 to the transmission ratio of the second motor 42 to the output shaft 210 is n:1, then their first and second commutation durations should theoretically be 1:n. Assuming the first and second duration thresholds are also set to 1:n, the stall shutdown protection of the first and second motors 41 and 42 will occur simultaneously, leading to the aforementioned superposition of current peaks and component damage. Therefore, in this application, if the speed ratio of the first and second motors 41 and 42 is n:1, the controller 60 will set the ratio of the first and second time thresholds to be different from 1:n, so that the stall stop protection of the first and second motors 41 and 42 will not be performed at the same time, thereby causing current peak shifting and avoiding component damage and control interference.

[0079] For example, assuming the speed ratio of the first and second motors 41 and 42 is n:1, the first and second commutation duration thresholds can be set to 0.95*1:1.05*n. When the power tool 100 stalls, the controller 60 will first detect that the first commutation duration of the first motor 41 exceeds the first duration threshold and control the first motor 41 to stop. After a certain period of time, the controller 60 will detect that the second commutation duration of the second motor 42 exceeds the second duration threshold and control the second motor 42 to stop. In other words, if the speed ratio of the first and second motors 41 and 42 is n:1, and the ratio of the first and second duration thresholds is less than 1:n, the controller 60 will control the first motor 41 and the second motor 42 to stop sequentially for stall protection. If the ratio of the first and second duration thresholds is greater than 1:n, the controller 60 will control the second motor 42 and the first motor 41 to stop sequentially for stall protection.

[0080] In other embodiments, the first motor parameters further include a first overcurrent parameter, and the first protection threshold includes a corresponding first overcurrent threshold. Conversely, the second motor parameters further include a second overcurrent parameter, and the second protection threshold includes a corresponding second overcurrent threshold. The first and second overcurrent thresholds are not numerically equal. The controller 60 will first detect that the first overcurrent parameter of the first motor 41 exceeds the first overcurrent threshold and control the first motor 41 to stop. Then, it will detect that the second overcurrent parameter of the second motor 42 exceeds the second overcurrent threshold and control the second motor 42 to stop.

[0081] In some embodiments, the overcurrent parameters mentioned above are motor currents, including but not limited to the motor's bus current, phase current, and quadrature shaft current. The first overcurrent parameter is the first current of the first motor 41, the first overcurrent threshold is the first current threshold, the second overcurrent parameter is the second current of the second motor 42, and the second overcurrent threshold is the second current threshold. The ratio of the current amplitudes of the two motors is related to their output torque. If the torque ratio of the first and second motors 41 and 42 driving the same output shaft 210 is n:1, then their current amplitudes should theoretically be n:1. Assuming that the first and second current thresholds are also set to n:1, the overcurrent shutdown protection of the first and second motors 41 and 42 will occur simultaneously, leading to the aforementioned problem of superimposed current peaks and component damage. Therefore, in this application, if the torque ratio of the first and second motors 41 and 42 is n:1, the controller 60 will set the ratio of the first and second current thresholds to be different from n:1, so that the overcurrent shutdown protection of the first and second motors 41 and 42 will not be activated at the same time, thereby causing current peak shifting and avoiding damage to components and control interference.

[0082] For example, assuming the torque ratio of the first and second motors 41 and 42 is n:1, the first and second current thresholds can be set to 0.95*1:1.05*n. When an overcurrent occurs in the power tool 100, the controller 60 will first detect that the first current of the first motor 41 exceeds the first current threshold and control the first motor 41 to stop. After a certain period of time, the controller 60 will detect that the second current of the second motor 42 exceeds the second current threshold and control the second motor 42 to stop. In other words, if the torque ratio of the first and second motors 41 and 42 is n:1, and the ratio of the first and second current thresholds is less than n:1, the controller 60 will control the first motor 41 and the second motor 42 to stop sequentially for overcurrent protection. If the ratio of the first and second current thresholds is greater than n:1, the controller 60 will control the second motor 42 and the first motor 41 to stop sequentially for overcurrent protection.

[0083] In some other embodiments, the overcurrent parameters may include one or more calculated values ​​of the motor's output torque, current, and demagnetization time. For example, the overcurrent parameter may be the motor's output torque, the motor's current, or the product of the motor's current and the demagnetization time. Similar to the previous description, different forms of overcurrent parameters have corresponding overcurrent thresholds, and the controller 60 compares and judges overcurrent parameters of the same form.

[0084] In summary, when the first and second motors 41 and 42 drive the same output shaft, if the parameters of the first and second motors of the same parameter type related to the shutdown protection are theoretically proportional, then when the ratio of the parameters of the first and second motors is n:1, the ratio of the first and second protection thresholds corresponding to the parameters of the first and second motors set in the controller 60 of the power tool 100 does not conform to the above-mentioned n:1 relationship, and the ratio of the two is not equal to n:1, thereby achieving the above-mentioned purpose of staggered shutdown protection.

[0085] In some embodiments, the first and second protection thresholds used by the controller 60 can be adaptively adjusted according to parameters such as the capacity and voltage of the power supply device 50. When the capacity and voltage of the power supply device 50 are different, the first protection threshold used by the controller 60 in the power tool 100 will be different, and / or the second protection threshold will be different. In some embodiments, the first and second protection thresholds used by the controller 60 can be negatively correlated with the capacity or voltage of the power supply device 50. For example, if the capacity or voltage of the power supply device 50 installed in the power tool 100 is higher, the first and second duration thresholds used by the controller 60 will be lowered accordingly to more sensitively detect stall when the power supply device 50 has a stronger power supply capacity. In other embodiments, the first and second protection thresholds used by the controller 60 can also be positively correlated with the capacity or voltage of the power supply device 50.

[0086] In other embodiments, the first and second protection thresholds used by the controller 60 can be dynamic thresholds, and the first and / or second protection thresholds can be related to the current and voltage of the motor assembly 40. Specifically, the first protection threshold can dynamically change with the current and voltage of the first motor 41, and the second protection threshold can dynamically change with the current and voltage of the second motor 42. In some embodiments, the first and second duration thresholds used by the controller 60 can be negatively correlated with the current and voltage of the first and second motors 41 and 42, respectively, and the first and second duration thresholds can be dynamically and adaptively adjusted downwards as the current and voltage of the first and second motors 41 and 42 increase.

[0087] Following on from the previous text, the power tool 100 is equipped with a first controller 61 and a second controller 62, which respectively provide shutdown protection for the first motor 41 and the second motor 42. The first controller 61 can detect the first motor parameters of the first motor 41 and control the first motor 41 to stop when the first motor parameters exceed a first protection threshold. The second controller 62 can detect the second motor parameters of the second motor 42 and control the second motor 42 to stop when the second motor parameters exceed a second protection threshold. The first protection threshold and the second protection threshold are not numerically equal, and there is a certain time interval between the moment when the first controller 61 controls the first motor 41 to stop and the moment when the second controller 62 controls the second motor 42 to stop.

[0088] Correspondingly, a control method for the power tool 100 is proposed and applied to the power tool 100 described above, with reference to... Figure 8 It illustrates a control method for the power tool 100, which may include the following steps:

[0089] S810, when the parameters of the first motor 41 of the power tool 100 exceed the first protection threshold, the controller 60 of the power tool 100 controls the first motor 41 to stop.

[0090] S820, when the second motor parameter of the second motor 42 of the power tool 100 exceeds the second protection threshold after the first motor parameter exceeds the first protection threshold, the controller 60 controls the second motor 42 to stop; the first protection threshold and the second protection threshold are not equal, and the first motor 41 and the second motor 42 drive the same output shaft 210.

[0091] Following on from the previous text, to address the issue of overlapping current peaks during shutdown protection as described earlier, controller 60 can also control the first motor 41 to stop when its parameters exceed the first protection threshold, and then control the second motor 42 to stop after the parameters exceed the first protection threshold and a second preset time has elapsed. This achieves time-sharing shutdown of the first and second motors 41 and 42 in a simpler way. However, with the single threshold plus delay method described above, if a logic fault occurs in the shutdown protection of the first motor 41, it will interfere with the shutdown protection of the second motor 42, leading to the problem that neither motor can stop. Further optimization with other protection logic is required, typically returning to the previously described scheme of using the first and second protection thresholds for peak-shaving protection.

[0092] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that the above embodiments do not limit this application in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of this application.

Claims

1. An electric tool, comprising: Functional components; The motor assembly includes a first motor and a second motor, wherein at least one of the first motor and the second motor drives the functional component to operate; A power supply device, connected to the motor assembly, provides power to at least the motor assembly; The first motor and the second motor have a transmission relationship, and the first motor drives the second motor to rotate when it rotates; the power tool also includes a controller connected to the motor assembly, and the controller is configured to control the second motor to start based on the back electromotive force of the second motor after the first motor starts.

2. The power tool according to claim 1, wherein, The second motor is a sensorless brushless motor.

3. The power tool according to claim 1, wherein, The controller is configured to control the first motor to start when it receives a signal to start the power tool.

4. The power tool according to claim 1, wherein, The controller is configured to start the second motor based on the back electromotive force of the second motor after the first motor has started and a first preset time has elapsed.

5. The power tool according to claim 4, wherein, The first preset duration is greater than or equal to 0.1s and less than or equal to 2s.

6. The power tool according to claim 1, wherein, The controller is configured to start the second motor based on the back electromotive force of the second motor after the first motor starts and the speed of the first motor reaches a first speed threshold.

7. The power tool according to claim 6, wherein, The first speed threshold is greater than or equal to 10 RPM or greater than or equal to 10% of the no-load speed of the first motor.

8. The power tool according to claim 4 or 6, wherein, The controller is configured to determine the rotor position of the second motor based on the extreme value of the back electromotive force of the second motor, or based on the relative relationship between the back electromotive force of the second motor and the zero potential, and to control the second motor to start.

9. The power tool according to claim 1, wherein, The controller includes a first controller and a second controller, the first controller being connected to the first motor and the second controller being connected to the second motor; the first controller is configured to control the first motor to start when it receives a signal to start the power tool; The second controller is configured to control the second motor to start based on the back electromotive force of the second motor after the first motor starts.

10. A method for controlling an electric tool, comprising: Start the first motor of the power tool; The controller of the power tool controls the second motor to start based on the back electromotive force of the second motor of the power tool after the first motor starts; There is a transmission relationship between the first motor and the second motor, and the first motor drives the second motor to rotate when it rotates.

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