Electric tool and control method thereof

Abstract

The invention discloses an electric tool and a control method thereof. The electric tool includes: a functional member; the motor assembly comprises a first motor and a second motor, and at least one of the first motor and the second motor drives the functional part to work; the power supply device is connected with the motor assembly and at least supplies power to the motor assembly; wherein the first motor and the second motor drive the same output shaft; the electric tool further comprises a controller connected with the motor assembly, and the controller is configured to control the first motor to stop when a first motor parameter of the first motor exceeds a first protection threshold value and control the second motor to stop when a second motor parameter of the second motor exceeds a second protection threshold value after the first motor parameter exceeds the first protection threshold value; the first protection threshold value is not equal to the second protection threshold value; according to the scheme, the phenomenon that peak current superposition damages components or interferes with related control when multiple motors in the electric tool are shut down for protection at the same time can be avoided, and smooth work of the tool is guaranteed.

Description

Technical Field

[0001] This application relates to the technical field of power tools, and particularly relates to a power tool and its control method. Background Art

[0002] Currently, most tools such as cutting, fastening, and impact tools widely used in various different scenarios such as construction and gardening are driven by electric energy supply. There is a motor in the power tool that is controlled by a controller to operate. In order to more flexibly respond to changing working conditions, currently, some power tools can be provided with a dual motor.

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

[0004] An object of this application is to solve or at least mitigate part or all of the above problems. To this end, an object of this application is to provide a power tool and its control method.

[0005] To achieve the above object, this application adopts the following technical solutions:

[0006] A power 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 drives 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 power tool further includes: a controller connected to the motor assembly, and the controller is configured to control the first motor to stop when the first motor parameter of the first motor exceeds a first protection threshold, and 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 of the first motor exceeds the first protection threshold; the first protection threshold is not equal to the second protection threshold.

[0007] In some embodiments, the first motor parameter includes the first stall parameter of the first motor, and the first protection threshold includes the first stall threshold; the second motor parameter includes the second stall parameter of the second motor, and the second protection threshold includes the second stall threshold.

[0008] In some embodiments, the first motor parameter includes the first overcurrent parameter of the first motor, and the first protection threshold includes the first overcurrent threshold; the second motor parameter includes the second overcurrent parameter of the second motor, and the second protection threshold includes the second overcurrent threshold.

[0009] 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 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 is not equal to the second duration threshold.

[0010] 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.

[0011] 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 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 is not equal to the second current threshold.

[0012] 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.

[0013] In some embodiments, the first overcurrent parameter is an arithmetic value of one or more of the first output torque, the first current, and the first demagnetization time of the first motor; the second overcurrent parameter is an arithmetic value of one or more of the second output torque, the second current, and the second demagnetization time of the second motor.

[0014] In some embodiments, when the ratio of the first motor parameters to the second motor parameters is n:1, the ratio of the first protection threshold to the second protection threshold is not equal to n:1.

[0015] In some embodiments, the power tool further includes: a driving device, including a first driving circuit and a second driving circuit, the first driving circuit is connected between the power supply device and the first motor, and the second driving circuit is connected between the power supply device and the second motor.

[0016] In some embodiments, the value of the first protection threshold is different when the capacity or voltage of the power supply device is different; and / or, the value of the second protection threshold is different when the capacity or voltage of the power supply device is different.

[0017] In some embodiments, the first protection threshold and / or the second protection threshold is a dynamic threshold and the value has a corresponding relationship with the current or voltage of the motor assembly at present.

[0018] In some embodiments, the controller includes a first controller and a second controller. The first controller is connected to a first motor through a first drive circuit, and the second controller is connected to a second motor through a second drive circuit. The first controller is configured to control the first motor to stop when a 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 a 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 is not equal to the second protection threshold.

[0019] An electric tool includes: a functional member; 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 member 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 a 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 after a second preset duration.

[0020] A control method for an electric tool includes: the controller of the electric tool controlling the first motor to stop when a first motor parameter of the first motor of the electric tool exceeds a first protection threshold; the controller controlling the second motor to stop when a second motor parameter of the second motor of the electric tool exceeds a second protection threshold after the first motor parameter exceeds the first protection threshold. The first protection threshold is not equal to the second protection threshold, and the first motor and the second motor drive the same output shaft.

[0021] An electric tool includes: a functional member; 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 member 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 when the first motor rotates, it drives the second motor to rotate. 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.

[0022] In some embodiments, the second motor is a sensorless brushless motor.

[0023] In some embodiments, the controller is configured to control the first motor to start when a signal to start the electric tool is received.

[0024] In some embodiments, 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 and after a first preset duration.

[0025] In some embodiments, the first preset duration is greater than or equal to 0.1 s and less than or equal to 2 s.

[0026] In some embodiments, the controller is configured to control the start of the second motor based on the back electromotive force of the second motor after the first motor starts and the rotational speed of the first motor reaches the first rotational speed threshold.

[0027] In some embodiments, the first rotational speed threshold is greater than or equal to 10 RPM or greater than or equal to 10% of the no-load rotational speed of the first motor.

[0028] 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 start of the second motor.

[0029] In some embodiments, the controller includes a first controller and a second controller. The first controller is connected to the first motor, and the second controller is connected to the second motor. The first controller is configured to control the start of the first motor when receiving a signal to start the power tool. The second controller is configured to control the start of the second motor based on the back electromotive force of the second motor after the first motor starts.

[0030] A control method for a power tool includes: starting a first motor of the power tool; the controller of the power tool controlling the start of a second motor 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 when the first motor rotates, it drives the second motor to rotate.

[0031] The beneficial effect of the present application is that: by setting different protection thresholds for the two motors, the actions of their shutdown protections are separated by a certain time, so that the peak currents during the shutdown protections of the first and second motors are staggered, avoiding damage to relevant components in the power tool or interference with the judgment of relevant control logics, and ensuring the smooth operation of the power tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a perspective view of a power tool as an embodiment of the present application from one perspective;

[0033] Figure 2 is Figure 1 a perspective view of the power tool shown from another perspective;

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

[0035] Figure 4 is Figure 1Stereogram of the motor assembly in the electric tool shown in another embodiment;

[0036] Figure 5 is Figure 1 Electrical control schematic diagram of the electric tool shown;

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

[0038] Figure 7 is the control flowchart of the electric tool as an embodiment of the present application;

[0039] Figure 8 is the control flowchart of the electric tool as another embodiment of the present application.

[0040] Figure caption description:

[0041] 100, Electric tool;

[0042] 10, Housing; 20, Functional component; 30, Operating component; 40, Motor assembly; 50, Power supply device; 60, Controller; 70, Driving device;

[0043] 41, First motor; 42, Second motor; 43, Clutch component; 61, First controller; 62, Second controller; 71, First driving circuit; 72, Second driving circuit; 210, Output shaft. Detailed implementation mode

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

[0045] In the present application, the terms "include", "comprise", "have" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including that element.

[0046] In the present application, the term "and / or" is a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in the present application generally represents an "and / or" relationship between the preceding and following associated objects.

[0047] In this application, the terms "connected", "combined", "coupled", and "installed" can be direct connections, combinations, couplings, or installations, or indirect connections, combinations, couplings, or installations. For example, a direct connection means that two parts or components are connected together without an intermediate member, and an indirect connection means that two parts or components are respectively connected to at least one intermediate member, and these two parts or components are connected through the intermediate member. In addition, "connected" and "coupled" are not limited to physical or mechanical connections or couplings, and may include electrical connections or couplings.

[0048] In this application, those of ordinary skill in the art will understand that relative terms used in connection with a quantity or condition (e.g., "about", "approximately", "substantially", etc.) are intended to include the recited value 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 resulting from manufacturing, assembly, use, etc. associated with a particular value. Such terms should also be considered to disclose a range defined by the absolute values of the two endpoints. Relative terms may refer to a plus or minus a certain percentage (e.g., 1%, 5%, 10% or more) of the indicated value. Numerical values without the use of relative terms should also be disclosed as having tolerances. In addition, when expressing relative angular positional relationships (e.g., substantially parallel, substantially perpendicular), "substantially" may refer to a plus or minus a certain number of degrees (e.g., 1 degree, 5 degrees, 10 degrees or more) from the indicated angle.

[0049] In this application, those of ordinary skill in the art will understand that the functions performed by a component can be performed by one component, multiple components, one part, or multiple parts. Similarly, the functions 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 such as "upper", "lower", "left", "right", "front", "rear", etc. are described based on the orientation and positional relationship shown in the drawings, and should not be construed as limiting the embodiments of this application. In addition, in the context, it should also be understood that when it is mentioned that one element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element. It should also be understood that directional terms such as upper side, lower side, left side, right side, front side, rear side, etc. not only represent the positive direction, but can also be understood as the side direction. For example, below can include directly below, lower left, lower right, front lower, and rear lower, etc.

[0051] In this application, the terms "controller", "processor", "central processing unit", "CPU", and "MCU" can be used interchangeably. When using the units "controller", "processor", "central processing unit", "CPU", or "MCU" to perform specific functions, unless otherwise specified, these functions can be performed by a single one of the above units or multiple ones of the above units.

[0052] In this application, for the terms "device", "module", or "unit" to achieve specific functions, they can be implemented in the form of hardware or software.

[0053] In this application, the terms "calculate", "judge", "control", "determine", "identify", etc. refer to the operations and processes of a computer system or a similar electronic computing device (such as a controller, a 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 as an embodiment in this application is shown. Figure 1 The shown electric tool 100 is a circular saw. The electric tool 100 in other embodiments can also be other types of handheld electric tools such as a jigsaw, a reciprocating saw, a drill, an impact wrench, or table tools such as a miter saw, a table saw, or outdoor power equipment such as a lawn mower, a snow blower. It can be understood that the electric tool 100 applying 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 1, the power tool 100 includes a housing 10, a functional component 20, and an operating component 30. Among them, the housing 10 constitutes the main body of the power tool 100, which connects or supports the above-mentioned components and forms an accommodation space, capable of accommodating or partially accommodating other components. The functional component 20 is a component in the power tool 100 that actually performs operations such as cutting, fastening, grinding, and impact. Taking an electric circular saw as an example, its functional component 20 is a circular saw blade, and the functional component 20 of other power tools 100 can also be a chain, a drill bit, etc. The operating component 30 is for the user to operate to switch the on / off state of the power tool 100 and can output corresponding start signals or stop signals. For example, the operating component 30 allows the user to start or stop the motor assembly 40 to be described later and output a start signal indicating that it is desired for the motor assembly 40 to start running or a stop signal indicating that it is desired for the motor assembly 40 to stop running to the controller 60 to be described later. In some cases, the operating component 30 may also have more diverse functions. For example, it can be operated by the user to adjust the motor speed or achieve other functions. In some embodiments, the operating component 30 can be a mechanical switch such as a trigger. It can be understood that the start and stop of the power tool 100 can also be achieved by other means other than setting the operating component 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 tablet computers to start or stop the power tool 100.

[0057] Reference Figures 2 to 5 , in addition to including the housing 10, the functional component 20, and the operating component 30, the power tool 100 further includes a motor assembly 40, a power supply device 50, and a controller 60. Among them, the motor assembly 40 is the prime mover of the power tool 100. When the motor shaft of the motor assembly 40 rotates, it will directly or indirectly drive the functional component 20 assembled on the output shaft 210 through a transmission component. In this application, the power tool 100 is at least configured with two motors, that is, the motor assembly 40 at least includes 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. The first and second motors 41 and 42 are inner rotor motors and the motor shafts of the first and second motors 41 and 42 are all parallel to the above-mentioned output shaft 210. The power transmission between the motor shaft and the output shaft 210 can be achieved by a gear set. Figure 4Another optional structure of the motor assembly 40 is shown, the first and second motors 41, 42 are inner rotor motors and the motor shafts of the first and second motors 41, 42 and the above-mentioned output shaft 210 are collinear, and a clutch 43 may be provided between the first and second motors 41, 42, and the clutch 43 has a first state that allows power transmission between the first and second motors 41, 42 and a second state that prevents power transmission between the first and second motors 41, 42, and the clutch 43 may be mechanical or electronic. The following text mainly explains the technical solution based on the motor assembly 40 including the first motor 41 and the second motor 42. At least one of the above-mentioned first motor 41 and the second motor 42 can drive the functional part 20 to perform operations such as cutting, tightening, grinding, and impacting. The following text mainly describes the scene where both the first motor 41 and the second motor 42 are working.

[0059] The power supply device 50 at least provides electrical energy for the above-mentioned motor assembly 40, and can also provide power for other related components such as the controller 60. In some embodiments, the power supply device 50 is a battery pack, which is detachably connected to the power tool 100. In other embodiments, the power supply device 50 can also be implemented using AC power, AC power supply in conjunction with a power adapter, transformer, rectifier, voltage stabilizer and other related circuits.

[0060] The controller 60 may be an MCU (Microcontroller Unit), an ARM (Advanced Reduced Instruction Set Computing Machine), a DSP (Digital Signal Processor), etc. By running a related program, the controller 60 may control the motor assembly 40 to operate as intended. Figure 5 The electric tool 100 also includes a driving device 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 driving device 70. The driving device 70 can convert the above control signals into driving signals that ultimately drive the motor to operate, and transmit the electric energy provided by the power supply device 50 to the motor assembly 40 through the DC bus.

[0061] In some embodiments, the driving device 70 includes a first driving circuit 71 connected between the controller 60 and the first motor 41, and a second driving circuit 72 connected between the controller 60 and the second motor 42. The first driving circuit 71 and the second driving circuit 72 may include a three-phase bridge circuit, which is composed of three switching tubes as the upper half bridge and three switching tubes as the lower half bridge. In the first driving circuit 71, the upper half bridge switching tubes 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, and the lower half bridge switching tubes Q2, Q4, and Q6 are respectively connected between each phase coil of the first motor 41 and the ground wire. The second driving circuit 72 and the second motor 42 are the same. The switching tubes may be field effect transistors or insulated gate bipolar transistors. In some other examples, the driving device 70 may also be an integrated driving chip or the like.

[0062] In addition, as Figure 6 shown, in some embodiments, there may be more than one controller 60 in terms of hardware. For example, in the power tool 100, a first controller 61 and a second controller 62 may be provided, and the first and second controllers 61 and 62 exchange data in an electrically connected manner or the like. Among them, the first controller 61 is responsible for controlling the operation of the first motor 41 and transmitting a first control signal to the first driving circuit 71, and the first driving circuit 71 is connected between the first controller 61 and the first motor 41. The second controller 62 is responsible for controlling the operation of the second motor 42 and transmitting a second control signal to the second driving circuit 72, and the second driving circuit 72 is connected between the second controller 62 and the second motor 42. In some 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 are dual VCPUs carried on the same hardware, or the first and second control units designed in the program, including parallel processes or threads, etc.

[0063] Continuing from the previous text, since the controller 60 needs to initially determine the initial position of the rotor of the motor when starting the motor, and the power tool 100 is configured with a first motor 41 and a second motor 42, and there is a transmission relationship between the first and second motors 41, 42, the rotation of any one motor will drive the rotation of the other motor, and there will be a problem that the rotor positions of the two motors affect each other when controlling the motor to start. To address the above problem, in one implementation, the controller 60 can control the above-mentioned first and second motors 41, 42 to start simultaneously. In response to a start signal from the operating member 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 respectively. 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, 62 perform signal synchronization before outputting the control signals to ensure that the first and second motors 41, 42 are started simultaneously. In another implementation, the controller 60 can also start the motor assembly 40 in a time-sharing manner, eliminating the signal synchronization operation and ensuring the safety of motor startup with a staggered peak.

[0064] In response to a start signal from the operating member 30 or other signals used to start the power tool 100, the controller 60 will first control the first motor 41 to start, and based on the back electromotive force generated when the second motor 42 is driven by the first motor 41 after the first motor 41 starts, control the second motor 42 to start. Specifically, the first motor 41 starts to rotate after being started by the controller 60. The rotation of the rotor of the first motor 41 will drive the rotor of the second motor 42 that 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, and the second motor 42 generates 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, when the second motor 42 has a position sensor, the controller 60 can also use the above method as an alternative scheme for starting the second motor 42.

[0065] It can be understood that the first motor 41 can be a sensorless brushless motor or a sensor brushless motor. Correspondingly, there are also various optional implementation manners for the controller 60 to control the first motor 41 to start first, and the present application does not make specific limitations thereto. In some embodiments, the controller 60 can use the pulse injection method to estimate the initial position of the rotor of the first motor 41 and control its start. The controller 60 can perform pulse injection on six electrical angle sectors of the first motor 41 respectively, that is, transmit corresponding pulse signals to six switching tubes in the first drive circuit 71, and then detect the current response of the first motor 41 to the above pulse injection, and determine the initial position of the rotor of the first motor 41 based on this current response, and then the first motor 41 can be controlled to start from this rotor initial position. In other embodiments, the controller 60 can also use the high-frequency injection method to control the first motor 41 to start. In still other embodiments, the controller 60 can also control the first motor 41 to start by capturing the edge jump of the Hall signal.

[0066] In some embodiments, after controlling the first motor 41 to start, the controller 60 can wait for a first preset duration, and then detect and control the second motor 42 to start based on the back electromotive force of the second motor 42. Specifically, after the first motor 41 starts and passes the first preset duration, the first motor 41 continues to rotate and already has a certain rotational speed, and then the back electromotive force of the second motor 42 driven by the first motor 41 is also in a state where it can be detected more accurately and can be used for start control. At this time, the controller 60 can estimate the rotor position of the second motor 42 based on the back electromotive force of the second motor 42 and control its start. If the above first preset duration is too short, the first and second motors 41 and 42 interfere with each other, and the start of both is affected. If it is too long, the driving effect of the first motor 41 on the second motor 42 is large, and the start control of the second motor 42 is difficult. Therefore, a first preset duration with an appropriate value needs to be set. In some embodiments, the above first preset duration is greater than or equal to 0.1 s and less than or equal to 2 s.

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

[0068] There are various alternative implementation manners for the controller 60 to control the startup of the second motor 42 based on the back electromotive force thereof, and the present application does not make specific limitations thereto. In some embodiments, the controller 60 may detect the extreme value of the back electromotive force of the second motor 42, that is, detect the maximum value or the minimum value of the back electromotive force of the second motor 42, and deduce the rotor position from the extreme value position of the back electromotive force of the second motor 42, and then perform startup control. In some other embodiments, the controller 60 may also detect the relative relationship between the back electromotive force of the second motor 42 and the zero potential, and deduce the rotor position from the zero-crossing position of the back electromotive force of the second motor 42, and then perform startup control.

[0069] Continuing from the foregoing, the power tool 100 is provided with a first controller 61 and a second controller 62 that are respectively responsible for controlling the startup of the first motor 41 and the second motor 42. In response to a startup signal from the operating member 30 or other signals for starting the power tool 100, first, the first controller 61 may control the first motor 41 to start, and then, the second controller 62 may control the second motor 42 to start based on the back electromotive force of the second motor 42. In some cases, after the first controller 61 runs the startup program of the first motor 41 in response to a relevant startup signal, it may send a notification to the second controller 62 to enable it to start running the startup program of the second motor 62. In some other cases, the first and second controllers 61 and 62 may spontaneously run the startup programs of the first and second motors 41 and 42 successively in response to a relevant startup signal. In some embodiments, the first controller 61 may notify the second controller 62 after controlling the first motor 41 to start and waiting for a first preset time period. After receiving the notification, the second controller 62 may control the second motor 42 to start based on the back electromotive force of the second motor 42. In some other embodiments, the first controller 61 may notify the second controller 62 after controlling the first motor 41 to start and detecting that the rotational speed of the first motor 41 reaches a first rotational speed threshold. After receiving the notification, the second controller 62 may control the second motor 42 to start based on the back electromotive force of the second motor 42. In some other embodiments, the first controller 61 may notify the second controller 62 after controlling the first motor 41 to start. After receiving the notification, the second controller 62 may wait for a first preset time period or detect that the rotational speed of the first motor 41 reaches a first rotational speed threshold and then control the second motor 42 to start based on the back electromotive force of the second motor 42. In some other embodiments, the first controller 61 may control the first motor 41 to start after receiving a relevant startup signal, and the second controller 62 may wait for a first preset time period or detect that the rotational speed of the first motor 41 reaches a first rotational speed threshold after receiving a relevant startup signal and then control the second motor 42 to start based on the back electromotive force of the second motor 42. It can be understood that in the case of dual controllers, whether there is mutual notification between the controllers, which controller 60 performs timing statistics or rotational speed detection does not constitute the focus of the solution of the present application and does not affect the protection scope of the present application.

[0070] In addition, the present application does not limit the specific control method of the controller 60 for driving the motor to operate after the motor is started. The motor assembly 40 can be controlled to operate either by a six-step commutation method or by a FOC method. Of course, other motor control methods can also be adaptively introduced.

[0071] Correspondingly, a control method for the power tool 100 is proposed, which is applied to the power tool 100 described above. Referring to Figure 7 , which shows the flow of the control method of the power tool 100, and can include the following steps:

[0072] S710, start 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 is started; there is a transmission relationship between the first motor 41 and the second motor 42, and the second motor 42 is driven to rotate when the first motor 41 rotates.

[0074] Continuing from the above, since the first and second motors 41 and 42 share the same power supply device 50 to achieve power supply, if the first and second motors 41 and 42 are controlled to perform shutdown protection simultaneously, the current peaks during their shutdown protection will be superimposed in the bus, which may cause damage to semiconductor components and the like, and may also interfere with the judgment of relevant control logics. To address the above problems, the controller 60 can set different protection thresholds for different motors to achieve time-sharing shutdown protection of the motor assembly 40, thereby ensuring the safety of motor shutdown with staggered peaks.

[0075] The controller 60 can control the first motor 41 to stop when the first motor parameter of the first motor 41 exceeds the first protection threshold, and control the second motor 42 to stop when the second motor parameter of the second motor 42 exceeds the second protection threshold. Among them, the first protection threshold and the second protection threshold are not equal in value, and there is a certain time interval between the moment when the first motor parameter exceeds the first protection threshold and the moment when the second motor parameter exceeds the second protection threshold. For the purpose of exemplary illustration, it is assumed hereinafter that the first motor parameter exceeds the first protection threshold prior to the second motor parameter exceeding the second protection threshold. However, it can be understood that by adjusting the values of the first and second protection thresholds, it is possible to achieve the first motor 41 stopping first or the second motor 42 stopping first, which does not affect the protection scope of the present application.

[0076] It should be noted here that there are multiple different parameter types for the motor parameters of the first and second motors 41 and 42, and there are also multiple different threshold types for the protection thresholds. 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. And in the above solution, the first and second motor parameters that are compared and judged successively should be of the same parameter type. That is, it is not to first judge whether the first motor parameter of one parameter type exceeds its corresponding first protection threshold, and then judge whether the second motor parameter of another parameter type exceeds its corresponding second protection threshold.

[0077] In some embodiments, the first motor parameter includes a first stall parameter, and the first protection threshold includes a corresponding first stall threshold. Correspondingly, the second motor parameter includes a second stall parameter, and the second protection threshold includes a corresponding second stall threshold. The above first and second stall thresholds are not equal in value. The controller 60 will first detect that the first stall parameter of the first motor 41 exceeds the above first stall threshold, control the first motor 41 to stop, and then detect that the second stall parameter of the second motor 42 exceeds the above second stall threshold, and control the second motor 42 to stop.

[0078] In some embodiments, the above stall parameter is the commutation duration. 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. Among them, the ratio of the commutation durations of the two motors is related to their rotational speeds. If the rotational speed ratio of the first and second motors 41 and 42 driving the same output shaft 210 is n:1, or rather, 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 that the first and second duration thresholds are also set to 1:n, the stall stop protection of the first and second motors 41 and 42 will occur simultaneously, which will then lead to the problem of the above-mentioned current peak superposition and component damage. Therefore, in this application, if the rotational speed ratio of the first and second motors 41 and 42 is n:1, the ratio of the first and second duration thresholds in the controller 60 will be set not equal to 1:n, so that the stall stop protection of the first and second motors 41 and 42 does not occur simultaneously, thereby causing the current to be staggered and avoiding component damage and control interference.

[0079] For example, assume that the speed ratio of the first and second motors 41 and 42 is n:1. The first and second duration thresholds can be set to 0.95*1:1.05*n. When the power tool 100 is jammed, 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 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, for the speed ratio n:1 of the first and second motors 41 and 42, if 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 successively for jam 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 successively for jam protection.

[0080] In some other embodiments, the first motor parameter further includes a first overcurrent parameter, and the first protection threshold includes a corresponding first overcurrent threshold. Correspondingly, the second motor parameter further includes a second overcurrent parameter, and the second protection threshold includes a corresponding second overcurrent threshold. The above first and second overcurrent thresholds are not equal in value. The controller 60 will first detect that the first overcurrent parameter of the first motor 41 exceeds the above 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 above second overcurrent threshold and control the second motor 42 to stop.

[0081] In some embodiments, the above overcurrent parameter is the motor current, including but not limited to the bus current, phase current, quadrature axis current, etc. of the motor. 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. Among them, the ratio of the current amplitudes of the two motors is related to their output torques. 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. Assume that the first and second current thresholds are also set to n:1. Then, the overcurrent stop protection of the first and second motors 41 and 42 will occur simultaneously, which will lead to problems such as the superposition of the above 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 ratio of the first and second current thresholds in the controller 60 will be set not equal to n:1, so that the overcurrent stop protection of the first and second motors 41 and 42 does not occur simultaneously, thereby making the current staggered and avoiding component damage and control interference.

[0082] For example, assume that 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 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, for the torque ratio n:1 of the first and second motors 41 and 42, if 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 successively 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 successively for overcurrent protection.

[0083] In some other embodiments, the above overcurrent parameters may include the operation values of one or more of the output torque, current, and demagnetization time of the motor. For example, the overcurrent parameter may be the output torque of the motor, or the current of the motor, or the product of the current of the motor and the demagnetization time, etc. Similarly to the previous text, different forms of overcurrent parameters each have corresponding overcurrent thresholds, and the forms of the overcurrent parameters that the controller 60 compares and judges successively are the same.

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

[0085] In some embodiments, the first and second protection thresholds adopted 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 parameters such as the capacity and voltage of the power supply device 50 are different, the first protection threshold adopted by the controller 60 in the power tool 100 is different, and / or the second protection threshold adopted is different. In some embodiments, the first and second protection thresholds adopted 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 assembled in the power tool 100 is higher, the first and second duration thresholds adopted by the controller 60 are correspondingly lowered to more sensitively detect jamming when the power supply capacity of the power supply device 50 is stronger. In some other embodiments, the first and second protection thresholds adopted by the controller 60 can also be positively correlated with the capacity or voltage of the power supply device 50.

[0086] In some other embodiments, the first and second protection thresholds adopted by the controller 60 may be dynamic thresholds, and the first protection threshold and / or the second protection threshold may be related to the current and voltage of the motor assembly 40 at present. Among them, the first protection threshold may vary dynamically with the current and voltage of the first motor 41, and the second protection threshold may vary dynamically with the current and voltage of the second motor 42. In some embodiments, the first and second duration thresholds adopted by the controller 60 may be negatively correlated with the current and voltage of the first and second motors 41 and 42 respectively. As the current and voltage of the first and second motors 41 and 42 increase, the first and second duration thresholds may be dynamically and adaptively decreased.

[0087] Continuing from the foregoing, in the power tool 100, a first controller 61 and a second controller 62 are provided to respectively undertake the shutdown protection of 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 shut down when the first motor parameters exceed the 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 shut down when the second motor parameters exceed the second protection threshold. Among them, the first protection threshold and the second protection threshold are not equal in value, and there is a certain time interval between the moment when the first controller 61 controls the first motor 41 to shut down and the moment when the second controller 62 controls the second motor 42 to shut down.

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

[0089] S810, when the first motor 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 shut down;

[0090] S820, when the second motor parameters of the second motor 42 of the power tool 100 exceed the second protection threshold after the first motor parameters exceed the first protection threshold, the controller 60 controls the second motor 42 to shut down; 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] Continuing from the above, in order to deal with the problem of current peak superposition during shutdown protection described above, the controller 60 can also control the first motor 41 to shut down when the first motor parameter of the first motor 41 exceeds the first protection threshold, and control the second motor 42 to shut down after the first motor parameter exceeds the first protection threshold and the second preset time has passed, thereby realizing the time-sharing shutdown of the first and second motors 41 and 42 in a more simplified manner. However, the above-mentioned single threshold plus delay method, once the shutdown protection of the first motor 41 has a logical failure, will interfere with the shutdown protection of the second motor 42, and then cause the problem that both motors cannot be stopped, and it is also necessary to cooperate with other protection logics for optimization, and usually it will return to the solution of peak-shifting protection using the first and second protection thresholds described above.

[0092] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the above embodiments do not limit the present application in any form, and any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present application.

Claims

1. An electric tool, comprising: 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 a first motor parameter of the first motor exceeds a first protection threshold, and to control the second motor to stop when a 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 is not equal to the second protection threshold.

2. The power tool according to claim 1, wherein, The first motor parameter includes a first stall parameter of the first motor, and the first protection threshold includes a first stall threshold; the second motor parameter includes a second stall parameter of the second motor, and the second protection threshold includes a second stall threshold.

3. The power tool according to claim 1, wherein, The first motor parameter includes a first overcurrent parameter of the first motor, and the first protection threshold includes a first overcurrent threshold; the second motor parameter includes a second overcurrent parameter of the second motor, and the second protection threshold includes a second overcurrent threshold.

4. The power tool according to claim 2, wherein, The first stall parameter is a first commutation duration of the first motor, and the first stall threshold is a first duration threshold; the second stall parameter is a second commutation duration of the second motor, and the second stall threshold is a 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 is not equal to the second duration threshold.

5. The power tool according to claim 4, wherein, 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.

6. The power tool according to claim 3, wherein, The first overcurrent parameter is a first current of the first motor, and the first overcurrent threshold is a first current threshold; the second overcurrent parameter is a second current of the second motor, and the second overcurrent threshold is a 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 is not equal to the second current threshold.

7. The power tool according to claim 6, wherein, 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.

8. The power tool according to claim 3, wherein, The first overcurrent parameter is an operation 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 an operation value of one or more of the second output torque, second current, and second demagnetization time of the second motor.

9. The power tool according to claim 1, wherein, 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.

10. The power tool according to claim 2 or 3, wherein, The power tool further includes: a driving device, including a first driving circuit and a second driving circuit, where the first driving circuit is connected between the power supply device and the first motor, and the second driving circuit is connected between the power supply device and the second motor.

11. The power tool according to claim 10, wherein, The value of the first protection threshold is different when the capacity or voltage of the power supply device is different; and / or, the value of the second protection threshold is different when the capacity or voltage of the power supply device is different.

12. The power tool according to claim 10, wherein, The first protection threshold and / or the second protection threshold is a dynamic threshold and its value has a corresponding relationship with the current or voltage of the motor assembly at present.

13. The power tool according to claim 10, wherein, The controller includes a first controller and a second controller. The first controller is connected to the first motor through the first driving circuit, and the second controller is connected to the second motor through the second driving circuit; The first controller is configured to control the first motor to stop when the first motor parameter of the first motor exceeds the 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 the second protection threshold after the first motor parameter of the first motor exceeds the first protection threshold; The first protection threshold is not equal to the second protection threshold.

14. A power tool, including: A functional member; A motor assembly, including a first motor and a second motor, at least one of the first motor and the second motor drives the functional member 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 power tool further includes: a controller, connected to the motor assembly, and the controller is configured to control the first motor to stop when the first motor parameter of the first motor exceeds the first protection threshold, and control the second motor to stop after the first motor parameter exceeds the first protection threshold and after a second preset duration.

15. A control method for a power tool, including: The controller of the power tool controls the first motor to stop when the first motor parameter of the first motor of the power tool exceeds the first protection threshold; The controller controls the second motor to stop when the second motor parameter of the second motor of the power tool exceeds the second protection threshold after the first motor parameter exceeds the first protection threshold; The first protection threshold is not equal to the second protection threshold, and the first motor and the second motor drive the same output shaft.

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