Outdoor operation apparatus, electric tool and control method therefor

Abstract

An outdoor operation apparatus, an electric tool, and a control method therefor. The electric tool comprises: a housing; a brushless motor, which is arranged in the housing and comprises a stator and a rotor; a power supply module, which is configured to supply power to the brushless motor; a drive module, which is configured to drive the brushless motor; and a control module, which is coupled with the drive module. The control module is configured to: inject a set direct-current voltage signal into a two-phase stationary coordinate system to obtain a three-phase current signal of the brushless motor; at least on the basis of the three-phase current signal, estimate a winding resistance of the rotor; on the basis of the winding resistance, estimate the temperature of the rotor; and, on the basis of the temperature, control the drive module to drive the operation state of the brushless motor.

Description

Outdoor working equipment and electric power tool and control method thereof

[0001] This application claims priority to the Chinese patent application No. 202410626962.1, filed on May 20, 2024, with the Chinese Patent Office, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of tool equipment, for example, to an outdoor working equipment and electric power tool and control method thereof. BACKGROUND

[0003] The inductance parameters and temperature parameters of the permanent magnet synchronous motor are obtained by relying on the position observer and the temperature sensor respectively. However, the inductance parameters obtained based on the position observer and the temperature parameters obtained based on the temperature sensor are both deviated, thereby affecting the control effect and the running stability of the permanent magnet synchronous motor.

[0004] This section provides background information relating to the present application, which is not necessarily prior art. SUMMARY

[0005] It is an object of the present application to solve or at least reduce some or all of the above problems. To this end, it is an object of the present application to provide an outdoor working equipment and electric power tool and control method thereof capable of improving the running stability.

[0006] To achieve the above object, the present application adopts the following technical solution: an electric power tool, comprising: a shell; a brushless motor arranged in the shell, comprising a stator and a rotor; a power module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor;

[0007] a control module coupled with the driving module; the control module is configured to: after injecting a set direct current voltage signal into a two-phase stationary coordinate system, obtain a three-phase current signal of the brushless motor; estimate a winding resistance of the rotor based on at least the three-phase current signal; estimate a temperature of the rotor based on the winding resistance; control the driving module to drive the running state of the brushless motor based on the temperature.

[0008] In some embodiments, the control module is specifically configured to: perform coordinate conversion on the three-phase current signal, determine a first current signal of a first stationary axis in the two-phase stationary coordinate system, and extract a first direct current signal in the first current signal which is of the same frequency as the set direct current voltage signal.

[0009] In some embodiments, the control module is specifically configured to: estimate the winding resistance of the rotor based on the first direct current signal and the set direct current voltage signal.

[0010] In some embodiments, the first direct current signal in the first current signal with the same frequency as the set direct voltage signal is extracted based on a low-pass filter or a band-pass filter.

[0011] In some embodiments, the control module is further configured to inject a set direct current signal into the two-phase static coordinate system, and determine the set direct voltage signal based on a PI control method, and inject the direct voltage signal into the two-phase static coordinate system.

[0012] In some embodiments, the two-phase static coordinate system includes a first static axis and a second static axis; the amplitude of the set direct current signal injected into the second static axis is 0.

[0013] In some embodiments, the control module is further configured to obtain an actual electrical angular velocity and a theoretical electrical angular velocity of the brushless motor; and determine a theoretical direct-axis current and a theoretical quadrature-axis current of the two-phase rotating coordinate system based on the actual electrical angular velocity and the theoretical electrical angular velocity.

[0014] In some embodiments, the control module is further configured to adjust the set direct current signal according to the theoretical direct-axis current and the theoretical quadrature-axis current.

[0015] In some embodiments, the control module is further specifically configured to determine an actual direct-axis current and an actual quadrature-axis current of the two-phase rotating coordinate system based on the three-phase current signal; and adjust the theoretical direct-axis current according to the actual direct-axis current, and adjust the theoretical quadrature-axis current according to the actual quadrature-axis current.

[0016] In some embodiments, the control module is configured to control the brushless motor to operate in a vector control mode.

[0017] In some embodiments, the brushless motor is a position sensorless brushless motor.

[0018] In some embodiments, the electric tool includes a handheld electric tool, an outdoor working device.

[0019] The application adopts the following technical solution: an outdoor working device, comprising: a walking wheel set supporting the outdoor working device to walk on the ground; a walking motor including a stator and a rotor, the walking motor being configured to drive the walking wheel set to rotate; a power module configured to supply power to the walking motor; a driving module configured to drive the walking motor to operate; a control module coupled with the driving module; the control module being configured to: after injecting a set direct voltage signal into a two-phase static coordinate system, obtain a three-phase current signal of the walking motor; estimate a winding resistance of the rotor based on at least the three-phase current signal; estimate a temperature of the rotor based on the winding resistance; and control the driving module to drive an operating state of the walking motor based on the temperature.

[0020] In some embodiments, the outdoor work equipment includes at least one of a smart lawn mower, a manned lawn mower, a snow blower, and an all-terrain vehicle.

[0021] The application adopts the following technical solution: A control method of an electric tool, the electric tool comprising: a shell; a brushless motor arranged in the shell, comprising a stator and a rotor; a power module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor; and a control module coupled with the driving module; the method comprising: after injecting a set direct-current voltage signal into a two-phase static coordinate system, acquiring a three-phase current signal of the brushless motor; estimating a winding resistance of the rotor based on at least the three-phase current signal; estimating a temperature of the rotor based on the winding resistance; and the temperature of the rotor controlling an operating state of the driving module driving the brushless motor.

[0022] The application adopts the following technical solution: An electric tool, comprising: a shell; a brushless motor arranged in the shell, comprising a stator and a rotor; a power module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor to operate; and a control module electrically coupled with the driving module; the control module is configured to: construct a two-phase relative rotating coordinate system different from a rotating angle of a two-phase rotating coordinate system, and inject a preset high-frequency signal into a first axis of the two-phase relative rotating coordinate system, so as to estimate and output a direct-axis inductance and a cross-axis inductance in the two-phase rotating coordinate system; and based on at least the direct-axis inductance and the cross-axis inductance, estimate a target direct-axis current and a target cross-axis current in the two-phase rotating coordinate system, so as to control the driving module to drive the brushless motor to operate.

[0023] In some embodiments, an angle difference between the rotating angle of the two-phase relative rotating coordinate system and the rotating angle of the two-phase rotating coordinate system is Δθ; wherein when Δθ = 0° or 180°, an inductance value of the direct-axis inductance of the two-phase rotating coordinate system is equal to an inductance value of the inductance on the first axis; and when Δθ = 90° or 270°, the inductance value of the inductance on the first axis is equal to an inductance value of the cross-axis inductance of the two-phase rotating coordinate system.

[0024] In some embodiments, the control module is specifically configured to: after injecting the preset high-frequency signal into the first axis, acquire a three-phase current signal of the brushless motor; based on the three-phase current signal, determine a high-frequency current with a same frequency as the preset high-frequency signal on the first axis, and extract an amplitude signal of the high-frequency current; extract a periodic signal in the amplitude signal of the high-frequency current that changes at a preset period, and based on the periodic signal, estimate and output the direct-axis inductance and the cross-axis inductance in the two-phase rotating coordinate system.

[0025] In some embodiments, the control module is specifically configured to: perform coordinate transformation on the three-phase current signal to determine an estimated current signal on the first axis; and extract a high-frequency current with a same frequency as the preset high-frequency signal in the estimated current signal.

[0026] In some embodiments, the high-frequency current in the estimated current signal that is the same frequency as the preset high-frequency signal is extracted based on a high-pass filter or a band-pass filter.

[0027] In some embodiments, the amplitude signal of the high-frequency current is extracted based on a Fourier decomposition method.

[0028] In some embodiments, the control module is specifically configured to: calculate an amplitude average of the periodic signal in a preset period; and estimate the direct-axis inductance and the quadrature-axis inductance in the two-phase rotating coordinate system based on the periodic signal and the amplitude average.

[0029] In some embodiments, the periodic signal that changes in a preset period in the amplitude signal of the high-frequency current is extracted based on a Fourier transform method.

[0030] In some embodiments, the preset high-frequency signal includes a sinusoidal signal or a periodic square wave signal.

[0031] In some embodiments, the control module is further configured to: obtain an actual electrical angular velocity and a theoretical electrical angular velocity of the brushless motor; determine a theoretical direct-axis current and a theoretical quadrature-axis current of the two-phase rotating coordinate system based on the actual electrical angular velocity and the theoretical electrical angular velocity; and adjust the preset high-frequency signal according to the theoretical direct-axis current and the theoretical quadrature-axis current.

[0032] In some embodiments, the control module is further specifically configured to: after injecting the preset high-frequency signal into the first axis, collect a three-phase current signal of the brushless motor; determine an actual direct-axis current and an actual quadrature-axis current of the two-phase rotating coordinate system based on the three-phase current signal; and adjust the theoretical direct-axis current according to the actual direct-axis current, and adjust the theoretical quadrature-axis current according to the actual quadrature-axis current.

[0033] The application adopts the following technical solution: an outdoor working device, comprising: a walking wheel set that supports the outdoor working device to walk on the ground; a walking motor comprising a stator and a rotor, the walking motor being configured to drive the walking wheel set to rotate; a power module configured to supply power to the walking motor; a driving module configured to drive the walking motor to operate; a control module electrically coupled with the driving module; the control module being configured to: construct a two-phase relative rotating coordinate system different from a rotating angle of a two-phase rotating coordinate axis, and inject a preset high-frequency signal into a first axis of the two-phase relative rotating coordinate system to estimate and output a direct-axis inductance and a quadrature-axis inductance in the two-phase rotating coordinate system; and estimate a target direct-axis current and a target quadrature-axis current in the two-phase rotating coordinate system based on at least the direct-axis inductance and the quadrature-axis inductance to control the driving module to drive the walking motor to operate.

[0034] The application adopts the following technical scheme: a control method of an electric tool, the electric tool comprising: a shell; a brushless motor arranged in the shell, comprising a stator and a rotor; a power module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor to operate; and a control module electrically connected with the driving module; the control method of the electric tool is executed by the control module, and the control method of the electric tool comprises: constructing a two-phase relative rotation coordinate system different from a rotation angle of a two-phase rotation coordinate axis, and injecting a preset high-frequency signal into a first axis of the two-phase relative rotation coordinate system to estimate and output direct-axis inductance and cross-axis inductance in the two-phase rotation coordinate system; and estimating target direct-axis current and target cross-axis current in the two-phase rotation coordinate system based on at least the direct-axis inductance and the cross-axis inductance to control the driving module to drive the brushless motor to operate. BRIEF DESCRIPTION OF DRAWINGS

[0035] Fig. 1 is a perspective view of an angle grinder provided by an embodiment of the application;

[0036] Fig. 2 is a circuit system block diagram provided by an embodiment of the application;

[0037] Fig. 3 is a rotor coordinate system diagram of a brushless motor provided by an embodiment of the application;

[0038] Fig. 4 is a flow block diagram of obtaining inductance parameters of a brushless motor provided by an embodiment of the application;

[0039] Fig. 5 is a flow chart of a control method of an electric tool provided by an embodiment of the application;

[0040] Fig. 6 is a flow chart of another control method of an electric tool provided by an embodiment of the application;

[0041] Fig. 7 is a flow chart of another control method of an electric tool provided by an embodiment of the application;

[0042] Fig. 8 is a flow chart of another control method of an electric tool provided by an embodiment of the application;

[0043] Fig. 9 is a flow block diagram of obtaining winding resistance of a brushless motor provided by an embodiment of the application;

[0044] Fig. 10 is another flow block diagram of obtaining winding resistance of a brushless motor provided by an embodiment of the application;

[0045] Fig. 11 is a flow chart of another control method of an electric tool provided by an embodiment of the application;

[0046] Fig. 12 is a flow chart of another control method of an electric tool provided by an embodiment of the application;

[0047] Fig. 13 is a temperature change curve of a motor obtained by two methods. DETAILED DESCRIPTION

[0048] Before any embodiments of the application are explained in detail, it is to be understood that the application is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the above-described accompanying drawings. It is being explained, however, by way of example only and not by way of limitation, with reference to the accompanying drawings.

[0049] In the present application, the terms "comprise", "contain", "include", or any other variant thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, an element defined by the phrase "comprising a" does not exclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0050] In the present application, the term "and / or", is a description of the associated relationship between objects, which means that there can be three kinds of relationships. For example, A and / or B, can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in the present application generally represents a "and / or" relationship between the front and rear associated objects.

[0051] In the present application, the terms "connection", "combination", "coupling", "mounting" can be direct connection, combination, coupling or mounting, or indirect connection, combination, coupling or mounting. Among them, for example, direct connection refers to the connection of two parts or components without the need for an intermediate part, and indirect connection refers to the connection of two parts or components with at least one intermediate part. In addition, "connection" and "coupling" are not limited to physical or mechanical connection or coupling, and can include electrical connection or coupling.

[0052] In the present application, those of ordinary skill in the art will understand that the relative terms used in connection with a quantity or a condition (for example, "about", "approximately", "substantially" and the like) include the value indicated and have the meaning indicated by the context. For example, the relative terms at least include the degree of error related to the measurement of a specific value, the tolerance caused by manufacturing, assembly, use, etc. related to a specific value. Such terms should also be considered to disclose the range defined by the absolute values of the two endpoints. The relative term can refer to a certain percentage (for example, 1%, 5%, 10% or more) of the indicated value. The numerical value without the relative term should also be disclosed as a specific value with a tolerance. In addition, "substantially" when expressing the relative angular positional relationship (for example, substantially parallel, substantially perpendicular), can refer to a certain number of degrees (for example, 1 degree, 5 degrees, 10 degrees or more) added or subtracted from the indicated angle.

[0053] In this application, it will be understood by those skilled in the art that the functions performed by the components can be performed by one component, multiple components, one part, or multiple parts. Similarly, the functions performed by the parts can also be performed by one part, one component, or a combination of multiple parts.

[0054] In this application, the terms "upper", "lower", "left", "right", "front", "back", and the like are described in the orientation and positional relationship shown in the drawings, and should not be understood as limiting the embodiments of the application. In addition, it is also understood in the context that when referring to one element connected to another element "on" or "under", it can be directly connected to another element "on" or "under" or indirectly connected to another element "on" or "under" through an intermediate element. It should also be understood that the terms "upper", "lower", "left", "right", "front", "back", and the like not only represent the positive direction, but also can be understood as the side direction. For example, the lower side can include the directly below, left below, right below, front below, and back below, etc.

[0055] In this application, the terms "controller", "processor", "central processing unit", "CPU", and "MCU" can be interchangeable. When using a unit "controller", "processor", "central processing unit", "CPU", or "MCU" to perform a specific function, unless otherwise specified, these functions can be performed by a single unit or multiple units.

[0056] In this application, the terms "device", "module", or "unit" can be implemented in the form of hardware or software to achieve a specific function.

[0057] In this application, the terms "calculate", "determine", "control", "determine", "identify", and the like refer to the operations and processes of a computer system or similar electronic computing device (e.g., controller, processor, etc.).

[0058] In order to achieve the control of the brushless motor, it is necessary to detect the position of the rotor, which refers to the rotational position of the rotor relative to the stator. The related art detects the position of the rotor in two different ways: one is the sensing control, that is, a position sensor is used to directly detect the position of the rotor and generate a corresponding control signal; the other is the non-sensing control, that is, the position or change of the rotor is determined according to the change of the winding electrical parameter, and then the starting commutation of the brushless motor is controlled.

[0059] Although the sensing control can simplify the control logic and make the control more direct, when the position sensor itself is not accurate due to assembly or other problems, it will have a greater impact on the driving of the brushless motor.

[0060] The cost of the inductive control is lower, and the inductive control of the related technology often adopts a rotor position observer to obtain the position of the rotor or the change of the position of the rotor. When the motor runs at high speed, the accuracy of the rotor position observer is greatly affected by the inductance parameter, so that the change of the inductance parameter will affect the accuracy of the obtained position of the rotor, and further affect the control effect and stability of the motor.

[0061] High-voltage brushless motors are gradually popular in the field of power tools, especially in the field of heavy-load power tools, due to their advantages of large power and small size. The high-voltage brushless motor uses a semiconductor switching device to realize electronic commutation, that is, an electronic switching device is used instead of a traditional contact commutator and brush. It has the advantages of high reliability, no commutation spark, low mechanical noise, and is widely used in various electric tools.

[0062] The present application provides an electric tool using a brushless motor. In one embodiment, the brushless motor is a high-voltage brushless motor using no position sensor.

[0063] As shown in FIG. 1, the electric tool includes a handheld electric tool, an outdoor working device. In some embodiments, the electric tool can be an angle grinder 10, and in other embodiments, the electric tool can also be a sander, a sanding machine, or other sanding or polishing tools. In some embodiments, the electric tool can also include an outdoor working vehicle. For the convenience of description, the electric tool takes an angle grinder as an example, of course, the electric tool can also be other tools that can convert the output torque into other forms of motion, which can be used to polish workpieces, such as sanders; these tools can also be used to cut workpieces, such as reciprocating saws, circular saws, and curve saws; these tools can also be used for impact, such as electric hammers; these tools can also be garden tools, such as snow blowers, trimmers, and chain saws; these tools can also be vehicle-type electric tools, for example, riding lawn mowers; in addition, these tools can also be used for other purposes, such as mixers. As long as these electric tools include a motor that drives the movement of the working parts, for example, a smart lawn mower, and an outdoor working device including a walking motor, the essential content of the technical solutions disclosed below can be adopted.

[0064] The angle grinder 10 can be mainly used for cutting, grinding, and brushing metal and stone materials. The front side, rear side, upper side, lower side, left side, and right side in FIG. 1 are described with respect to the position of the electric tool relative to the user when the electric tool is in use.

[0065] As shown in FIG. 1, the angle grinder 10 comprises a housing 11, a brushless motor 12, a power module 13, a driving module and a control module. The brushless motor is disposed in the housing and comprises a stator and a rotor. The power module is configured to supply power to the brushless motor. The driving module is configured to drive the brushless motor to operate to realize the electric tool operation. The control module is electrically coupled with the driving module. The brushless motor 12 of the angle grinder 10 of the embodiment can be a position sensorless AC brushless motor.

[0066] The circuit system 100 of the electric tool can be a circuit as shown in FIG. 2, comprising: a brushless motor 12, a power module 101, a driving module 102, a detection module 103 and a control module 104.

[0067] The brushless motor 12 can comprise three-phase windings u, v, w in Y-connection, and the connection ends of the three-phase windings are defined as phase connection end A, phase connection end B and phase connection end C, respectively. In other embodiments, the three-phase windings of the brushless motor 12 can also be in delta connection.

[0068] The driving module 102 is electrically connected to the power module 101, and includes a plurality of switching elements. The driving module 102 is electrically connected to the control module 104 and the brushless motor 12, and is capable of controlling the brushless motor 12 to operate according to the control signal output by the control module 104. In an exemplary embodiment, the control module includes a PWM signal generator, and the driving module includes a three-phase inverter. The PWM signal generator is configured to generate a PWM signal, and the three-phase inverter is configured to control the brushless motor 12 to operate according to the PWM signal. As an implementation, the brushless motor 12 is a three-phase motor, and has three-phase windings. The driving module 102 is electrically connected to the three-phase windings of the brushless motor 12. The driving module 102 specifically includes a switching circuit, which is configured to drive the rotor of the motor to operate according to the control signal of the control module 104. In order to make the motor rotate, the driving module 102 has a plurality of driving states. In a driving state, a magnetic field is generated in the stator winding of the motor. The control module 104 is configured to output a corresponding driving signal to the driving module 102 according to the position of the rotor of the brushless motor 12, so as to switch the driving state of the driving module 102, thereby changing the state of the voltage and / or current loaded on the winding of the brushless motor 12, generating an alternating magnetic field to drive the rotor to rotate, and thus achieving the driving of the motor. For example, the driving module 102 includes switching elements Q1, Q2, Q3, Q4, Q5, and Q6. Among them, Q1, Q3, and Q5 are high-side switching elements, and Q2, Q4, and Q6 are low-side switching elements. Any one phase stator winding of the brushless motor 12 is connected to a high-side switching element and a low-side switching element. The gate terminal of each switching element in the driving module 102 is electrically connected to the control module 104, and is configured to receive the control signal from the control module 104. The control signal can be a PWM signal. In an embodiment, if the switching element is a MOS tube, the drain or source of each switching element is connected to the stator winding of the brushless motor 12. In an embodiment, if the switching element is an IGBT tube, the collector and emitter of each switching element are connected to the stator winding of the brushless motor 12. The switching elements Q1-Q6 receive the control signal from the control module 104 to change their conduction states, thereby changing the current loaded on the stator winding of the brushless motor 12 by the power module 101.

[0069] The detection module 103 is electrically connected to the multi-phase stator winding of the brushless motor 12, and is configured to detect the electrical parameter of the multi-phase stator winding during the operation of the brushless motor 12. Specifically, the electrical parameter can be an electrical parameter that can be directly detected, such as voltage or current, or a parameter calculated according to the voltage or current, such as slope or derivative.

[0070] The control module 104 is electrically connected to the detection module 103 and the driving module 102, and is configured to control the on-off state of the switching element of the driving module 102, so as to control the working mode and driving state of the brushless motor 12. In some embodiments, the control module 104 adopts a dedicated controller, such as a dedicated control chip (e.g., MCU, Microcontroller Unit). The control module 104 is integrated with a signal processing unit, which is configured to process the acquired parameter signals, and has the functions of calculation, comparison, judgment, etc. After the signal processing unit processes the signals, a control signal can be generated and output to the driving module 102 to drive the brushless motor 12 to operate.

[0071] The power module 101 includes a power supply, which is an alternating current power supply in this embodiment.

[0072] In some embodiments, the control module 104 controls the electrical signal of the driving module 102 by outputting a pulse width modulation (PWM) signal to the switching element of the driving module 102.

[0073] The control module 104 is configured to construct a two-phase relative rotation coordinate system different from the rotation angle of the two-phase rotation coordinate axis, and inject a preset high-frequency signal into the first axis of the two-phase relative rotation coordinate system, so as to estimate and output the direct-axis inductance and the cross-axis inductance in the two-phase rotation coordinate system; and estimate the target direct-axis current and the target cross-axis current in the two-phase rotation coordinate system based on at least the direct-axis inductance and the cross-axis inductance, so as to control the driving module to drive the brushless motor to operate.

[0074] The preset high-frequency signal can include, but is not limited to, a periodically changing high-frequency voltage signal. In an optional embodiment, the preset high-frequency signal includes a sine signal or a periodic square wave signal, so that the angle difference Δθ between the two-phase relative rotation coordinate system and the two-phase rotation coordinate system can change periodically. It should be noted that the frequency and amplitude of the preset high-frequency signal can be set according to actual conditions, as long as the brushless motor can operate normally. The target direct-axis current in the two-phase rotation coordinate system can be understood as the input current of the direct-axis, and similarly, the target cross-axis current can be understood as the input current of the cross-axis.

[0075] FIG. 3 is a schematic diagram of a rotor coordinate system of a brushless motor according to an embodiment of the present application. Referring to FIG. 3, the coordinate system formed by the a-axis and the β-axis is a two-phase stationary coordinate system, i.e., a reference coordinate system. The d-axis and the q-axis are two-phase rotating coordinate axes, the two-phase rotating coordinate axes rotate at an electrical speed ωe, and θe is the angle between the two-phase rotating coordinate axes and the two-phase stationary coordinate system. The d-axis, i.e., the direct axis, in the two-phase rotating coordinate axes is used to control the size of the magnetic field, and the q-axis, i.e., the quadrature axis, is used to control the size of the force, and the electrical angle between the direct axis and the quadrature axis is 90°. The γ-axis and the δ-axis are two-phase relative rotating coordinate systems, ωγ is the rotating speed of the two-phase relative rotating coordinate systems, and θγ is the angle between the two-phase relative rotating coordinate systems and the two-phase stationary coordinate system. In some embodiments, the γ-axis is a first axis, and the δ-axis is a second axis. In some embodiments, the δ-axis is a first axis, and the γ-axis is a second axis. For the convenience of understanding, the γ-axis is a first axis, and the δ-axis is a second axis in the following description unless otherwise specified.

[0076] In the above equation, the rotating angle of the two-phase rotating coordinate axes and the rotating angle of the two-phase relative rotating coordinate systems are different, so that the angle difference θγ- θe=△θ between the two-phase relative rotating coordinate systems and the two-phase rotating coordinate axes is periodically changed, and thus the real values of the d-axis and q-axis inductances can be obtained by detecting the maximum and minimum values of the γ-axis inductance. In an optional embodiment, the angle difference between the rotating angle of the two-phase relative rotating coordinate systems and the rotating angle of the two-phase rotating coordinate systems is △θ; when △θ=0° or 180°, the inductance value of the direct-axis inductance of the two-phase rotating coordinate systems is equal to the inductance value of the inductance on the first axis; when △θ=90° or 270°, the inductance value of the inductance on the first axis is equal to the inductance value of the quadrature-axis inductance of the two-phase rotating coordinate systems.

[0077] It can be understood that when △θ=0° or 180°, the two-phase rotating coordinate axes coincide with or are opposite to the two-phase relative rotating coordinate systems, at this time, the inductance value of the first-axis inductance is the same as the inductance value of the direct-axis inductance, and the inductance value of the second-axis inductance is the same as the inductance value of the quadrature-axis inductance. When △θ=90° or 270°, the two-phase rotating coordinate axes are perpendicular to each other, at this time, the inductance value of the first-axis inductance is the same as the inductance value of the quadrature-axis inductance, and the inductance value of the second-axis inductance is the same as the inductance value of the direct-axis inductance. When △θ≠0°, △θ≠90°, △θ≠180°, and △θ≠270°, the inductance value of the first-axis inductance is between the inductance values of the direct-axis inductance and the quadrature-axis inductance, and the inductance value of the second-axis inductance is between the inductance values of the direct-axis inductance and the quadrature-axis inductance.

[0078] Specifically, by constructing a two-phase relative rotation coordinate system, the rotation angle of the two-phase relative rotation coordinate system is different from that of the two-phase rotation coordinate axis, so that the angle difference Δθ between the two-phase relative rotation coordinate system and the two-phase rotation coordinate axis changes periodically during the rotation of the rotor. By injecting a preset high-frequency signal into the first axis of the two-phase relative rotation coordinate system, the direct-axis inductance and the cross-axis inductance in the two-phase rotation coordinate system are estimated according to the inductance values of the inductance of the first axis and the second axis of the two-phase relative rotation coordinate system and the angle difference Δθ between the two-phase relative rotation coordinate system and the two-phase rotation coordinate axis during the rotation of the rotor. Thus, the target direct-axis current and the target cross-axis current in the two-phase rotation coordinate system can be estimated according to the impedance relationship after the direct-axis inductance and the cross-axis inductance are estimated, and then the driving module is controlled to drive the operation of the brushless motor according to the target direct-axis current and the target cross-axis current in the two-phase rotation coordinate system.

[0079] In the embodiment, the control module is configured to construct a two-phase relative rotation coordinate system with a rotation angle different from that of the two-phase rotation coordinate axis, and inject a preset high-frequency signal into the first axis of the two-phase relative rotation coordinate system, so as to estimate and output the direct-axis inductance and the cross-axis inductance in the two-phase rotation coordinate system. Then, at least based on the direct-axis inductance and the cross-axis inductance, the target direct-axis current and the target cross-axis current in the two-phase rotation coordinate system are estimated to control the driving module to drive the operation of the brushless motor. In this way, the real values of the direct-axis inductance and the cross-axis inductance of the motor can be obtained to estimate the target direct-axis current and the target cross-axis current, without introducing the rotor electrical angle signal to construct the two-phase rotation coordinate axis, so that the position observer is not needed to obtain the rotor electrical angle signal, avoiding the problem of large precision deviation of the position observer when the motor runs at high speed, and being beneficial to improving the control effect and the operation stability of the brushless motor.

[0080] Optionally, FIG. 4 is a flow block diagram of obtaining the inductance parameters of the brushless motor according to an embodiment of the present application. As shown in FIG. 4, the control module is specifically configured to: after injecting the preset high-frequency signal into the first axis, collect the three-phase current signals Ia, Ib and Ic of the brushless motor; based on the three-phase current signals Ia, Ib and Ic, determine the high-frequency current Iγh on the first axis that is the same frequency as the preset high-frequency signal Uγh, and extract the amplitude signal AIγh of the high-frequency current; extract the periodic signal AIγh_A in the amplitude signal AIγh of the high-frequency current that changes at a preset period, and based on the periodic signal AIγh_A, estimate and output the direct-axis inductance Ld and the cross-axis inductance Lq in the two-phase rotation coordinate system.

[0081] The three-phase current signals Ia, Ib, and Ic of the brushless motor can be, but are not limited to, collected by the detection module 103. The high-frequency current Iγh can be understood as a current signal on the first axis that is the same frequency as the injected preset high-frequency signal Uγh. The amplitude signal AIγh of the high-frequency current Iγh can include, but is not limited to, the amplitude of the high-frequency current. Considering the detection accuracy of the detection module and the error generated by the phase change, there can be an amplitude signal that does not change according to the preset period in the amplitude signal AIγh of the high-frequency current. The existence of the amplitude signal that does not change according to the preset period will affect the accuracy of the obtained inductance parameters. Therefore, the amplitude signal AIγh of the high-frequency current can be extracted to eliminate the amplitude signal that does not change according to the preset period, so as to improve the accuracy of the obtained inductance parameters. The periodic signal AIγh_A can be understood as the amplitude signal that changes according to the preset period in the amplitude signal of the high-frequency current.

[0082] In some embodiments, based on the periodic signal AIγh_A, the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can be estimated and output. Specifically, the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can be estimated and output based on the extreme value of the periodic signal AIγh_A. In some embodiments, based on the periodic signal AIγh_A, the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can be estimated and output. Specifically, the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can be calculated and output based on the periodic signal AIγh_A and the average value AIγh_av of the periodic signal.

[0083] It can be understood that FIG. 4 only exemplarily shows the case where the first axis is the γ axis, the preset high-frequency signal Uγh is injected into the first axis, and the signal injected into the δ axis is 0, which does not limit the position of the injection of the preset high-frequency signal. In some embodiments, the first axis can also be the δ axis. At this time, the preset high-frequency signal injected into the first axis is Uδh, and the signal injected into the γ axis is 0.

[0084] In an optional embodiment, based on the three-phase current signals Ia, Ib, and Ic, the high-frequency current on the first axis that is the same frequency as the preset high-frequency signal Uγh can include: performing coordinate transformation on the three-phase current signals Ia, Ib, and Ic to determine the estimated current signal Iαγ on the first axis; and extracting the high-frequency current Iγh that is the same frequency as the preset high-frequency signal from the estimated current signal Iαγ.

[0085] The coordinate transformation on the three-phase current signals Ia, Ib, and Ic can include, based on a Clarke transformation, transforming the three-phase current signals Ia, Ib, and Ic into current signals Ia and Iβ in a reference coordinate system, and based on a Park transformation, transforming the current signals Ia and Iβ in the reference coordinate system into an estimated current signal Iaγ on a first axis in a two-phase relative rotating coordinate system. Extracting a high-frequency current Iγh in the estimated current signal Iaγ that is the same frequency as the preset high-frequency signal can be understood as filtering or removing the high-frequency current in the estimated current signal Iaγ that is different from the preset high-frequency signal Uγh. In an optional embodiment, extracting the high-frequency current Iγh in the estimated current signal Iaγ that is the same frequency as the preset high-frequency signal Uγh can filter the high-frequency current in the estimated current signal Iaγ that is different from the preset high-frequency signal Uγh based on a high-pass filter or a band-pass filter BPF to extract the high-frequency current Iγh in the estimated current signal Iaγ that is the same frequency as the preset high-frequency signal Uγh, thereby simplifying the process of extracting the high-frequency current in the estimated current signal that is the same frequency as the preset high-frequency signal, and facilitating improvement of the efficiency of obtaining the inductance parameter.

[0086] In an optional embodiment, extracting the amplitude signal AIγh of the high-frequency current Iγh can extract the amplitude signal AIγh from the high-frequency current Iγh based on a Fourier transform method FFT or a Fourier decomposition method.

[0087] In an optional embodiment, extracting a periodic signal AIγh_A that varies at a preset period in the amplitude signal AIγh of the high-frequency current Iγh, and based on the periodic signal AIγh_A, estimating and outputting the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can include: calculating an amplitude average value AIγh_av of each periodic signal AIγh_A in the preset period; based on the periodic signal AIγh_A and the amplitude average value AIγh_av, estimating the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system.

[0088] In an optional embodiment, extracting a periodic signal AIγh_A that varies at a preset period in the amplitude signal AIγh of the high-frequency current Iγh, and based on the periodic signal AIγh_A, estimating and outputting the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can include: calculating an amplitude average value AIγh_av of each periodic signal AIγh_A in the preset period; based on the periodic signal AIγh_A and the amplitude average value AIγh_av, estimating the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system.

[0089] In an optional embodiment, extracting a periodic signal AIγh_A that varies at a preset period in the amplitude signal AIγh of the high-frequency current Iγh, and based on the periodic signal AIγh_A, estimating and outputting the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system can include: calculating an amplitude average value AIγh_av of each periodic signal AIγh_A in the preset period; based on the periodic signal AIγh_A and the amplitude average value AIγh_av, estimating the direct-axis inductance Ld and the quadrature-axis inductance Lq in the two-phase rotating coordinate system.

[0090] In an optional embodiment, the periodic signal AIγh_A that varies in the preset period in the amplitude signal AIγh of the high-frequency current Iγh can include: based on a Fourier transform method or a Fourier decomposition method, extracting the periodic signal AIγh_A that varies in the preset period from the amplitude signal AIγh of the high-frequency current Iγh.

[0091] Optionally, continuing to refer to FIG. 4, the control module is further configured to: acquire an actual electrical angular velocity w of the brushless motor and a theoretical electrical angular velocity w*; determine a theoretical direct-axis current Id* and a theoretical quadrature-axis current Iq* of the two-phase rotating coordinate system based on the actual electrical angular velocity w and the theoretical electrical angular velocity w*; and adjust the preset high-frequency signal Uγh according to the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq*.

[0092] In the formula, the detection component can include a position observer, and the actual electrical angular velocity w of the brushless motor can be acquired by the position observer. The theoretical electrical angular velocity w* is a theoretical electrical angular velocity that the brushless motor should have under a current working condition. The theoretical direct-axis current Id* can be understood as a theoretical current value on a direct axis under the current working condition, and similarly, the theoretical quadrature-axis current Iq* can be understood as a theoretical current value on a quadrature axis under the current working condition. In an optional embodiment, the determination of the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* of the two-phase rotating coordinate system based on the actual electrical angular velocity w and the theoretical electrical angular velocity w* can be that the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* of the two-phase rotating coordinate system are calculated by a speed controller based on the actual electrical angular velocity w and the theoretical electrical angular velocity w* by using a PID algorithm.

[0093] In an optional embodiment, the adjustment of the preset high-frequency signal according to the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* can include that the theoretical direct-axis voltage Ud* and the theoretical quadrature-axis voltage Uq* are calculated by a current controller based on the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* by using a PID algorithm, and then the theoretical α-axis voltage Uα* and the theoretical β-axis voltage Uβ* under a reference coordinate system are estimated by using a Park inverse transformation based on the theoretical direct-axis voltage Ud* and the theoretical quadrature-axis voltage Uq* and an observation angle θ of the two-phase rotating coordinate axes, so as to adjust the preset high-frequency signal Uγh according to the theoretical α-axis voltage Uα* and the theoretical β-axis voltage Uβ*, so as to input the adjusted preset high-frequency signal to a PWM signal generator SVPWM, thereby generating a PWM signal for driving a three-phase inverter.

[0094] In an optional embodiment, the adjusting the preset high-frequency signal Uγh according to the theoretical α-axis voltage Uα* and the theoretical β-axis voltage Uβ* can specifically be: estimating the injected α-axis voltage Uαh and the injected β-axis voltage Uβh in the reference coordinate system according to the injected preset high-frequency signal Uγh by using Park inverse transformation, adjusting the injected α-axis voltage Uαh according to the theoretical α-axis voltage Uα*, and adjusting the injected β-axis voltage Uβh according to the theoretical β-axis voltage Uβ*.

[0095] Optionally, still referring to FIG. 4, the control module is further specifically configured to: after injecting the preset high-frequency signal Uγh into the first axis of the two-phase relative rotating coordinate system, collect three-phase current signals Ia, Ib, Ic of the brushless motor; determine an actual direct-axis current Id and an actual quadrature-axis current Iq of the two-phase rotating coordinate system based on the three-phase current signals Ia, Ib, Ic; adjust the theoretical direct-axis current Id* according to the actual direct-axis current Id, and adjust the theoretical quadrature-axis current Iq* according to the actual quadrature-axis current Iq.

[0096] In an optional embodiment, the determining the actual direct-axis current Id and the actual quadrature-axis current Iq of the two-phase rotating coordinate system based on the three-phase current signals Ia, Ib, Ic can include: transforming the three-phase current signals Ia, Ib, Ic into an actual α-axis current Iα and an actual β-axis current Iβ in the reference coordinate system based on Clarke transformation, and then transforming the actual α-axis current Iα and the actual β-axis current Iβ in the reference coordinate system into the actual direct-axis current Id and the actual quadrature-axis current Iq based on Park transformation, the actual α-axis current Iα and the actual β-axis current Iβ, and an observation angle θ of the two-phase rotating coordinate system. The adjusting the theoretical direct-axis current Id* according to the actual direct-axis current Id includes comparing the actual direct-axis current Id and the theoretical direct-axis current Id*, and adjusting the theoretical direct-axis current Id* according to a comparison result. Similarly, the adjusting the theoretical quadrature-axis current Iq* according to the actual quadrature-axis current Iq includes comparing the actual quadrature-axis current Iq and the theoretical quadrature-axis current Iq*, and adjusting the theoretical quadrature-axis current Iq* according to a comparison result.

[0097] Based on the same idea, the application further provides a control method of an electric power tool. FIG. 5 is a flowchart of a control method of an electric power tool according to an embodiment of the application. As shown in FIG. 5, the control method of the electric power tool includes:

[0098] S110, constructing a two-phase relative rotating coordinate system different from a rotating angle of a two-phase rotating coordinate axis, and injecting a preset high-frequency signal into a first axis of the two-phase relative rotating coordinate system to estimate and output a direct-axis inductance and a quadrature-axis inductance in the two-phase rotating coordinate system.

[0099] The electric tool comprises a housing, a brushless motor, a power module, a driving module and a control module. The brushless motor is arranged in the housing, and the brushless motor comprises a stator and a rotor. The power module is configured to supply power to the brushless motor. The driving module is configured to drive the brushless motor to operate. The control module is electrically connected with the driving module, and the control module is configured to execute the control method of the electric tool.

[0100] In some embodiments, the preset high-frequency signal comprises a sine signal or a periodic square wave signal.

[0101] S120, based at least on the direct-axis inductance and the quadrature-axis inductance, estimating target direct-axis current and target quadrature-axis current in a two-phase rotating coordinate system to control the driving module to drive the brushless motor to operate.

[0102] Since the control method of the electric tool is executed by the control module of the electric tool, it can achieve the beneficial effects of the electric tool provided in any embodiment of the present application, and the same parts can be referred to the description above.

[0103] FIG. 6 is a flowchart of another control method of an electric tool provided in an embodiment of the present application. Referring to FIG. 6, S110 specifically comprises:

[0104] S111, after injecting the preset high-frequency signal into the first axis, collecting three-phase current signals of the brushless motor.

[0105] S112, based on the three-phase current signals, determining a high-frequency current on the first axis with the same frequency as the preset high-frequency signal, and extracting an amplitude signal of the high-frequency current.

[0106] S113, extracting a periodic signal in the amplitude signal of the high-frequency current that changes with a preset period, and based on the periodic signal, estimating and outputting direct-axis inductance and quadrature-axis inductance in a two-phase rotating coordinate system.

[0107] In some embodiments, the specific method of extracting the periodic signal in the amplitude signal of the high-frequency current that changes with a preset period is based on Fourier transform method.

[0108] In some embodiments, FIG. 7 is a flowchart of another control method of an electric tool provided in an embodiment of the present application. Referring to FIG. 7, S112 comprises:

[0109] S1121, performing coordinate transformation on the three-phase current signals to determine an estimated current signal on the first axis.

[0110] S1122, extracting a high-frequency current in the estimated current signal with the same frequency as the preset high-frequency signal.

[0111] In some embodiments, the specific method for extracting the high-frequency current with the same frequency as the preset high-frequency signal in the estimated current signal is based on a high-pass filter or a band-pass filter.

[0112] S1123, extract the amplitude signal of the high-frequency current based on the Fourier decomposition method.

[0113] In some embodiments, FIG. 8 is a flowchart of another control method of the electric tool according to an embodiment of the present application. Referring to FIG. 8, S113 includes:

[0114] S1131, calculate the amplitude average value of each periodic signal in a preset period.

[0115] S1132, estimate the direct-axis inductance and the quadrature-axis inductance in the two-phase rotating coordinate system based on the periodic signal and the amplitude average value.

[0116] The present application also provides an electric tool. For ease of description, the present embodiment only describes the differences from the above-mentioned embodiments, and the same or similar components as those in the above-mentioned embodiments are labeled with the same reference numerals. The parts in the above-mentioned embodiments that are suitable for the present embodiment can be applied to the present embodiment, and only the different parts of the present embodiment from the above-mentioned embodiments are described below.

[0117] FIG. 9 is a flowchart of obtaining the winding resistance of the brushless motor according to an embodiment of the present application. Referring to FIG. 9, the control module in the electric tool in the present embodiment is configured to: after injecting a set direct-current voltage signal UαDC into the two-phase stationary coordinate system, obtain three-phase current signals Ia, Ib and Ic of the brushless motor; estimate the winding resistance Rs of the rotor based on at least the three-phase current signals Ia, Ib and Ic; estimate the temperature of the rotor based on the winding resistance Rs; and control the driving module to drive the operating state of the brushless motor based on the temperature. In some embodiments, the control module is configured to control the brushless motor to operate in a vector control mode. In some embodiments, the brushless motor is a brushless motor without a position sensor.

[0118] The two-phase stationary coordinate system is a reference coordinate system, for example, the coordinate system formed by the α-axis and the β-axis in FIG. 3. In some embodiments, the two-phase stationary coordinate system includes a first stationary axis and a second stationary axis. When the first stationary axis is the α-axis, the second stationary axis is the β-axis. When the first stationary axis is the β-axis, the second stationary axis is the α-axis. The present embodiment does not make specific limitations on this, and for ease of understanding, the first stationary axis is taken as the α-axis and the second stationary axis is taken as the β-axis in the following exemplary description.

[0119] The preset direct current voltage signal can include, but is not limited to, a periodically changing direct current voltage signal. In some embodiments, the preset direct current voltage signal can be a sinusoidal signal or a high-frequency square wave signal. It should be noted that the amplitude of the preset direct current voltage signal can be set according to actual needs. When the preset direct current voltage signal is high, the signal-to-noise ratio of the position estimation can be improved, but the operating noise of the brushless motor will be increased. In some embodiments, the preset direct current voltage signal can be set to 10% of the DC bus voltage.

[0120] It should be noted that injecting the preset direct current voltage signal into the two-phase static coordinate system can be understood as injecting a first direct current voltage signal into the a-axis of the two-phase static coordinate system and injecting a second direct current voltage signal into the β-axis. The amplitudes of the first direct current voltage signal and the second direct current voltage signal are both not 0, or the amplitude of the first direct current voltage signal is 0, or the amplitude of the second direct current voltage signal is 0. When the amplitude of the preset direct current voltage signal injected into the second static axis, i.e., the second direct current voltage signal, is 0, there is no coupling mutual inductance in the two-phase static coordinate system, which is conducive to simplifying the process of estimating the winding resistance of the rotor.

[0121] It should also be noted that FIG. 9 only exemplarily shows the case of injecting the preset direct current voltage signal UαDC into the a-axis of the two-phase static coordinate system, and does not limit the injection of the preset direct current voltage signal into the two-phase static coordinate system. For the convenience of understanding, the case of injecting the preset direct current voltage signal UαDC into the a-axis of the two-phase static coordinate system is described below without special description.

[0122] The three-phase current signals Ia, Ib, and Ic of the brushless motor can be collected by the detection module 103, but are not limited thereto. In some embodiments, estimating the winding resistance Rs of the rotor based on at least the three-phase current signals Ia, Ib, and Ic can include estimating the direct current voltage and the direct current IαDC, IβDC of the two-phase static coordinate system based on the three-phase current signals Ia, Ib, and Ic, and then calculating the winding resistance Rs of the rotor based on Ohm's law according to the direct current voltage UαDC and the direct current IαDC, IβDC of the two-phase static coordinate system. In some embodiments, estimating the winding resistance Rs of the rotor based on at least the three-phase current signals Ia, Ib, and Ic can include estimating the direct current IαDC, IβDC of the two-phase static coordinate system based on the three-phase current signals Ia, Ib, and Ic, and then calculating the winding resistance Rs of the rotor based on Ohm's law according to the direct current IαDC, IβDC and the injected preset direct current voltage signal UαDC.

[0123] Since the winding resistance Rs of the rotor has a certain corresponding relationship with the temperature of the rotor, the temperature of the rotor can be estimated based on the winding resistance Rs.

[0124] In this embodiment, a set direct current voltage signal is injected into the two-phase stationary coordinate system, and then the three-phase current signals of the brushless motor are acquired, so that the winding resistance of the rotor is estimated based on at least the three-phase current signals, which is beneficial to improve the winding resistance accuracy of the rotor, thereby improving the temperature accuracy of the rotor when the temperature of the rotor is estimated based on the winding resistance, and further avoiding problems such as demagnetization of the permanent magnet and aging of the insulation material of the brushless motor caused by excessively high motor temperature when the driving module is controlled to drive the brushless motor to operate. In addition, the temperature of the rotor can be acquired in real time without setting a temperature acquisition resistor and a calculation circuit of the temperature acquisition resistor by estimating the temperature of the rotor based on the winding resistance, which is beneficial to reduce the cost. In addition, the winding resistance of the rotor is estimated by the method of injecting a set direct current voltage signal into the two-phase stationary coordinate system, so that the control parameters are updated, which is beneficial to improve the control consistency of the brushless motor, thereby improving the performance of the brushless motor.

[0125] Optionally, with reference back to FIG. 9, the control module is specifically configured to: perform coordinate conversion on the three-phase current signals Ia, Ib and Ic, determine at least a first current signal Iα of a first stationary axis in the two-phase stationary coordinate system, and extract a first direct current signal IαDC in the first current signal Iα that is of the same frequency as the set direct current voltage signal UαDC; and estimate the winding resistance of the rotor based on the first direct current signal IαDC and the set direct current voltage signal UαDC.

[0126] The coordinate conversion on the three-phase current signals Ia, Ib and Ic can include converting the three-phase current signals Ia, Ib and Ic into a current of an α axis and a current of a β axis in the two-phase stationary coordinate system based on a Clarke transformation method.

[0127] The determination of the first current signal Iα of the first stationary axis in the two-phase stationary coordinate system can be understood as the determination of the first current signal Iα of the α axis in the two-phase stationary coordinate system, or the determination of a second current signal Iβ of the β axis in the two-phase stationary coordinate system, or the determination of the first current signal Iα of the α axis and the second current signal Iβ of the β axis in the two-phase stationary coordinate system.

[0128] The first direct current signal IαDC can be understood as a current signal in the first current signal Iα that is of the same frequency as the set direct current voltage signal UαDC. In some embodiments, the control module is further configured to extract a second direct current signal IβDC in the second current signal Iβ that is of the same frequency as the set direct current voltage signal UαDC. The second direct current signal IβDC can be understood as a current signal in the second current signal Iβ that is of the same frequency as the set direct current voltage signal UαDC.

[0129] In some embodiments, extracting the first direct current signal IαDC in the first current signal Iα that has the same frequency as the set direct current voltage signal UαDC can include extracting the first direct current signal in the first current signal Iα that has the same frequency as the set direct current voltage signal based on a low-pass filter or a band-pass filter, thereby simplifying the process of extracting the first direct current signal IαDC in the first current signal Iα that has the same frequency as the set direct current voltage signal UαDC, and facilitating to improve the efficiency of obtaining the winding resistance of the rotor.

[0130] Estimating the winding resistance of the rotor based on the first direct current signal IαDC and the set direct current voltage signal UαDC can include calculating the winding resistance Rs of the rotor based on the first direct current signal IαDC and the set direct current voltage signal UαDC by using a second formula, wherein the second formula is as follows:

[0131] wherein ωe is an electrical angle of a two-phase rotating coordinate axis, Ld is an inductance of a direct axis in the two-phase rotating coordinate axis, and Lq is an inductance of a quadrature axis in the two-phase rotating coordinate axis.

[0132] Optionally, FIG. 10 is a flow chart of another process of obtaining the winding resistance of the brushless motor according to an embodiment of the present application. As shown in FIG. 10, the control module is further configured to inject a set direct current signal iαDC_ref into the two-phase stationary coordinate system, and determine the set direct current voltage signals UαDC and UβDC based on a PI control method.

[0133] The set direct current signal iαDC_ref can include, but is not limited to, a periodically varying direct current signal. It should be noted that injecting the set direct current signal into the two-phase stationary coordinate system can be understood as injecting a first direct current signal into an α axis of the two-phase stationary coordinate system and injecting a second direct current signal into a β axis of the two-phase stationary coordinate system. The amplitude of the first direct current signal and the amplitude of the second direct current signal are both not 0, or the amplitude of the first direct current signal is 0, or the amplitude of the second direct current signal is 0. When the amplitude of the set direct current signal injected into the second stationary axis, i.e., the second direct current signal, is 0, and the amplitude of the set direct current signal injected into the first stationary axis, i.e., the first direct current signal, is not 0, there is only a mutual inductance direct current iβDC in the second direct axis of the two-phase stationary coordinate system, thereby facilitating to simplify the process of estimating the winding resistance of the rotor.

[0134] It should be noted that FIG. 10 only exemplarily shows the case of injecting the set direct current signal iαDC_ref into the a-axis of the two-phase static coordinate system, and does not limit the injection of the set direct current signal into the two-phase static coordinate system. For the convenience of understanding, the case of injecting the set direct current signal iαDC_ref into the a-axis of the two-phase static coordinate system is described below without special instructions.

[0135] It should be noted that after the set direct current signal iαDC_ref is injected into the two-phase static coordinate system, due to the coupling mutual inductance between the first static axis and the second static axis in the two-phase static coordinate system, the current of the first static axis is the sum of the set direct current signal iαDC_ref and the mutual direct current iαDC on the first static axis, and the current of the first static axis generates the first direct voltage UαDC on the first static axis through PI regulation. Similarly, the current of the second static axis is the sum of the injected direct current signal and the mutual direct current iβDC on the second static axis, and the current of the second static axis generates the second direct voltage UβDC on the second static axis through PI regulation.

[0136] Specifically, when the set direct current signal iαDC_ref is injected into the two-phase static coordinate system, the estimated winding resistance Rs of the rotor can adopt a third formula, wherein the third formula is as follows:

[0137] Optionally, as shown in FIG. 9 and FIG. 10, the control module is further configured to: obtain an actual electrical angular velocity w of the brushless motor and a theoretical electrical angular velocity w*; determine a theoretical direct-axis current Id* and a theoretical quadrature-axis current Iq* of the two-phase rotating coordinate system based on the actual electrical angular velocity w and the theoretical electrical angular velocity w*; and adjust the set direct voltage signal UαDC according to the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq*.

[0138] Wherein, the actual electrical angular velocity w of the brushless motor can be obtained by a position observer. The theoretical electrical angular velocity w* is the electrical angular velocity that the brushless motor should theoretically output under the current working condition. The theoretical direct-axis current Id* can be understood as the theoretical current value on the direct axis under the current working condition, and similarly, the theoretical quadrature-axis current Iq* can be understood as the theoretical current value on the quadrature axis under the current working condition. In an optional embodiment, based on the actual electrical angular velocity w and the theoretical electrical angular velocity w*, the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* of the two-phase rotating coordinate system can be calculated by a speed controller based on the actual electrical angular velocity w* and the theoretical electrical angular velocity w through a PID algorithm.

[0139] In an optional embodiment, adjusting the set DC voltage signal UαDC according to the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* can comprise calculating the theoretical direct-axis voltage Ud* and the theoretical quadrature-axis voltage Uq* according to the theoretical direct-axis current Id* and the theoretical quadrature-axis current Iq* by a current controller using a PID algorithm, and estimating the theoretical α-axis voltage Uα* and the theoretical β-axis voltage Uβ* in the reference coordinate system according to the theoretical direct-axis voltage Ud* and the theoretical quadrature-axis voltage Uq* and the observation angle θ of the two-phase rotating coordinate system using Park inverse transformation, so as to adjust the set DC voltage signal UαDC according to the theoretical α-axis voltage Uα* and the theoretical β-axis voltage Uβ* to input the adjusted set DC voltage signal into the SVPWM signal generator, so as to generate the PWM signal for driving the three-phase inverter.

[0140] Optionally, with continuous reference to FIG. 9 or FIG. 10, the control module is further configured to determine the actual direct-axis current Id and the actual quadrature-axis current Iq of the two-phase rotating coordinate system based on the three-phase current signals Ia, Ib, Ic, and adjust the theoretical direct-axis current Id* according to the actual direct-axis current Id and adjust the theoretical quadrature-axis current Iq* according to the actual quadrature-axis current Iq.

[0141] The actual direct-axis current Id of the two-phase rotating coordinate system can be understood as the current on the direct axis under the current working condition. Similarly, the actual quadrature-axis current Iq of the two-phase rotating coordinate system can be understood as the current on the quadrature axis under the current working condition. In an optional embodiment, determining the actual direct-axis current Id and the actual quadrature-axis current Iq of the two-phase rotating coordinate system based on the three-phase current signals Ia, Ib, Ic can comprise transforming the three-phase current signals Ia, Ib, Ic into the actual α-axis current Iα and the actual β-axis current Iβ in the reference coordinate system based on the Clarke transformation method, and transforming the actual α-axis current Iα and the actual β-axis current Iβ in the reference coordinate system into the actual direct-axis current Id and the actual quadrature-axis current Iq based on the actual α-axis current Iα and the actual β-axis current Iβ and the observation angle θ of the two-phase rotating coordinate system using the Park transformation method.

[0142] Adjusting the theoretical direct-axis current Id* according to the actual direct-axis current Id can comprise comparing the actual direct-axis current Id with the theoretical direct-axis current Id*, and adjusting the theoretical direct-axis current Id* according to the comparison result. Similarly, adjusting the theoretical quadrature-axis current Iq* according to the actual quadrature-axis current Iq can comprise comparing the actual quadrature-axis current Iq with the theoretical quadrature-axis current Iq*, and adjusting the theoretical quadrature-axis current Iq* according to the comparison result.

[0143] Based on the same concept, the application further provides a control method of an electric tool. FIG. 11 is a flow chart of another control method of an electric tool according to an embodiment of the application. As shown in FIG. 11, the control method of the electric tool comprises:

[0144] S210, after injecting the set direct current voltage signal into the two-phase stationary coordinate system, acquiring a three-phase current signal of the brushless motor.

[0145] The electric tool comprises a housing, a brushless motor, a power module, a driving module and a control module. The brushless motor is arranged in the housing, and the brushless motor comprises a stator and a rotor. The power module is configured to supply power to the brushless motor. The driving module is configured to drive the brushless motor to operate. The control module is electrically connected with the driving module, and the control module is configured to execute the control method of the electric tool.

[0146] S220, estimating the winding resistance of the rotor based on at least the three-phase current signal.

[0147] S230, estimating the temperature of the rotor based on the winding resistance.

[0148] S240, controlling the driving module to drive the operating state of the brushless motor based on the temperature.

[0149] Since the control method of the electric tool is executed by the control module of the electric tool, the control method of the electric tool can achieve the beneficial effects provided by any embodiment of the electric tool, and the same parts can be referred to the description above.

[0150] FIG. 12 is a flow chart of another control method of an electric tool according to an embodiment of the present application. Referring to FIG. 12, S220 specifically comprises:

[0151] S221, performing coordinate conversion on the three-phase current signal, determining at least a first current signal of a first stationary axis in a two-phase stationary coordinate system, and extracting a first direct current signal in the first current signal and having the same frequency as the set direct current voltage signal.

[0152] In some embodiments, the first direct current signal in the first current signal and having the same frequency as the set direct current voltage signal is extracted based on a low-pass filter or a band-pass filter.

[0153] S222, estimating the winding resistance of the rotor based on the first direct current signal and the set direct current voltage signal.

[0154] Fig. 13 shows the temperature change curves of the motor acquired by two methods, the horizontal coordinate is time, and the vertical coordinate is the temperature of the motor. In Fig. 13, the curve represented by the dotted line is the internal temperature curve of the motor acquired by the method disclosed in the present application, and the curve represented by the solid line is the surface temperature of the motor detected by the NTC temperature sensor. As can be seen from Fig. 13, the change rule of the internal temperature of the motor acquired by the technical solution disclosed in the present application with time is basically consistent with the change rule of the surface temperature of the motor detected by the temperature sensor with time. It can be understood that at the same time, the internal temperature of the motor will be higher than the surface temperature, therefore, the temperature estimated by the technical solution disclosed in the present application will be higher than the surface temperature of the motor at the same time.

[0155] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art 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 power tool, comprising: a housing; a brushless motor disposed in the housing, comprising a stator and a rotor; a power supply module configured to supply power to the brushless motor; a drive module configured to drive the brushless motor; a control module coupled with the drive module; wherein the control module is configured to: after injecting a set direct current voltage signal into a two-phase stationary coordinate system, obtain a three-phase current signal of the brushless motor; estimate a winding resistance of the rotor based on at least the three-phase current signal; estimate a temperature of the rotor based on the winding resistance; control an operating state of the drive module driving the brushless motor based on the temperature.

2. The power tool of claim 1, wherein, the control module is configured to: perform coordinate conversion on the three-phase current signal, determine a first current signal of a first stationary axis in the two-phase stationary coordinate system, and extract a first direct current signal in the first current signal that has a same frequency as the set direct current voltage signal.

3. The power tool of claim 2, wherein, the control module is configured to: estimate the winding resistance of the rotor based on the first direct current signal and the set direct current voltage signal.

4. The power tool of claim 2, wherein, the first direct current signal in the first current signal that has a same frequency as the set direct current voltage signal is extracted based on a low-pass filter or a band-pass filter.

5. The power tool of claim 1, wherein, the control module is further configured to: inject a set direct current signal into the two-phase stationary coordinate system, and determine the set direct current voltage signal based on a PI control method, and inject the direct current voltage signal into the two-phase stationary coordinate system.

6. The power tool of claim 2, wherein, the two-phase stationary coordinate system comprises a first stationary axis and a second stationary axis; an amplitude of the set direct current signal injected into the second stationary axis is 0.

7. The power tool of claim 1, wherein, the control module is further configured to: obtain an actual electrical angular velocity and a theoretical electrical angular velocity of the brushless motor; based on the actual electrical angular velocity and the theoretical electrical angular velocity, determine a theoretical direct-axis current and a theoretical quadrature-axis current of a two-phase rotating coordinate system.

8. The power tool of claim 7, wherein, the control module is further configured to: adjust the set direct current signal according to the theoretical direct-axis current and the theoretical quadrature-axis current.

9. The power tool of claim 8, wherein, the control module is further configured to: based on the three-phase current signal, determine an actual direct-axis current and an actual quadrature-axis current of the two-phase rotating coordinate system; adjust the theoretical direct-axis current according to the actual direct-axis current, and adjust the theoretical quadrature-axis current according to the actual quadrature-axis current.

10. The power tool of claim 1, wherein, the control module is configured to control the brushless motor to operate in a vector control mode.

11. The power tool of claim 1, wherein, the brushless motor is a position sensorless brushless motor.

12. The power tool of claim 1, wherein, the electric power tool comprises a handheld electric power tool and an outdoor working device.

13. An outdoor working device, comprising: a walking wheel set supporting the outdoor working device to walk on the ground; a walking motor comprising a stator and a rotor, the walking motor being configured to drive the walking wheel set to rotate; a power supply module configured to supply power to the walking motor; a drive module configured to drive the walking motor to operate; a control module coupled with the drive module; wherein the control module is configured to: After injecting a set direct current voltage signal into a two-phase stationary coordinate system, a three-phase current signal of the walking motor is acquired; at least based on the three-phase current signal, a winding resistance of the rotor is estimated; based on the winding resistance, a temperature of the rotor is estimated; based on the temperature, an operation state of the driving module driving the walking motor is controlled.

14. The outdoor work apparatus according to claim 13, wherein The outdoor working equipment includes at least one of an intelligent mower, a manned mower, a snow sweeper, and an all-terrain vehicle.

15. A control method of an electric power tool, the electric power tool comprising: a housing; a brushless motor disposed in the housing, including a stator and a rotor; a power module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor; a control module coupled with the driving module; wherein the method comprises: after injecting a set direct current voltage signal into a two-phase stationary coordinate system, acquiring a three-phase current signal of the brushless motor; at least based on the three-phase current signal, estimating a winding resistance of the rotor; based on the winding resistance, estimating a temperature of the rotor; and the temperature of the rotor controls an operation state of the driving module driving the brushless motor.

16. An electric power tool, comprising: a housing; a brushless motor disposed in the housing, including a stator and a rotor; a power module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor to operate; a control module electrically coupled with the driving module; the control module is configured to: construct a two-phase relative rotating coordinate system different from a rotating angle of a two-phase rotating coordinate system, and inject a preset high-frequency signal into a first axis of the two-phase relative rotating coordinate system, to estimate and output direct-axis inductance and cross-axis inductance in the two-phase rotating coordinate system; based on at least the direct-axis inductance and the cross-axis inductance, estimate target direct-axis current and target cross-axis current in the two-phase rotating coordinate system, to control the driving module to drive the brushless motor to operate.

17. The power tool of claim 16, wherein, an angle difference between the rotating angle of the two-phase relative rotating coordinate system and the rotating angle of the two-phase rotating coordinate system is △θ; wherein when △θ = 0° or 180°, an inductance value of the direct-axis inductance of the two-phase rotating coordinate system is equal to an inductance value of the inductance on the first axis; when △θ = 90° or 270°, the inductance value of the inductance on the first axis is equal to an inductance value of the cross-axis inductance of the two-phase rotating coordinate system.

18. The power tool of claim 16, wherein, the control module is configured to: after injecting the preset high-frequency signal into the first axis, acquire a three-phase current signal of the brushless motor; based on the three-phase current signal, determine a high-frequency current on the first axis with the same frequency as the preset high-frequency signal, and extract an amplitude signal of the high-frequency current; extract a periodic signal in the amplitude signal of the high-frequency current that changes at a preset period, and based on the periodic signal, estimate and output the direct-axis inductance and the cross-axis inductance in the two-phase rotating coordinate system.

19. The power tool of claim 18, wherein, the control module is configured to: perform coordinate transformation on the three-phase current signal to determine an estimated current signal on the first axis; extract the high-frequency current in the estimated current signal with the same frequency as the preset high-frequency signal.

20. The power tool of claim 19, wherein, extracting the high-frequency current in the estimated current signal that is of the same frequency as the preset high-frequency signal based on a high-pass filter or a band-pass filter.

21. The power tool of claim 18, wherein, extracting an amplitude signal of the high-frequency current based on a Fourier decomposition method.

22. The power tool of claim 18, wherein, The control module is configured to: calculate an average value of amplitudes of the periodic signals in the preset period; estimate direct-axis inductance and quadrature-axis inductance in the two-phase rotating coordinate system based on the periodic signals and the average value of amplitudes.

23. The power tool of claim 18, wherein, extract a periodic signal that varies in a preset period from the amplitude signal of the high-frequency current based on a Fourier transform method.

24. The power tool of claim 16, wherein, The preset high-frequency signal includes a sinusoidal signal or a periodic square wave signal.

25. The power tool of claim 16, wherein, The control module is further configured to: obtain an actual electric angular velocity and a theoretical electric angular velocity of the brushless motor; determine theoretical direct-axis current and theoretical quadrature-axis current of the two-phase rotating coordinate system based on the actual electric angular velocity and the theoretical electric angular velocity; adjust the preset high-frequency signal according to the theoretical direct-axis current and the theoretical quadrature-axis current.

26. The power tool of claim 25, wherein, The control module is further configured to: collect three-phase current signals of the brushless motor after injecting the preset high-frequency signal into the first axis; determine actual direct-axis current and actual quadrature-axis current of the two-phase rotating coordinate system based on the three-phase current signals; adjust the theoretical direct-axis current according to the actual direct-axis current, and adjust the theoretical quadrature-axis current according to the actual quadrature-axis current.

27. An outdoor working device, comprising: a walking wheel set supporting the outdoor working device to walk on the ground; a walking motor including a stator and a rotor, the walking motor being configured to drive the walking wheel set to rotate; a power supply module configured to supply power to the walking motor; a driving module configured to drive the walking motor to operate; a control module electrically coupled to the driving module; The control module is configured to: construct a two-phase relative rotating coordinate system different from a rotating angle of a two-phase rotating coordinate axis, and inject a preset high-frequency signal into a first axis of the two-phase relative rotating coordinate system to estimate and output direct-axis inductance and quadrature-axis inductance in the two-phase rotating coordinate system; estimate target direct-axis current and target quadrature-axis current in the two-phase rotating coordinate system based on at least the direct-axis inductance and the quadrature-axis inductance, to control the driving module to drive the walking motor to operate.

28. A control method of an electric tool, the electric tool comprising: a housing; a brushless motor disposed in the housing, including a stator and a rotor; a power supply module configured to supply power to the brushless motor; a driving module configured to drive the brushless motor to operate; a control module electrically connected to the driving module; The control method of the electric tool is performed by the control module, and the control method of the electric tool comprises: constructing a two-phase relative rotating coordinate system different from a rotating angle of a two-phase rotating coordinate axis, and injecting a preset high-frequency signal into a first axis of the two-phase relative rotating coordinate system to estimate and output direct-axis inductance and quadrature-axis inductance in the two-phase rotating coordinate system; At least based on the direct-axis inductance and the quadrature-axis inductance, a target direct-axis current and a target quadrature-axis current in the two-phase rotating coordinate system are estimated to control the driving module to drive the operation of the brushless motor.

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