WO2022142841A1 - 电动工具及其控制方法 - Google Patents

电动工具及其控制方法 Download PDF

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Publication number
WO2022142841A1
WO2022142841A1 PCT/CN2021/131633 CN2021131633W WO2022142841A1 WO 2022142841 A1 WO2022142841 A1 WO 2022142841A1 CN 2021131633 W CN2021131633 W CN 2021131633W WO 2022142841 A1 WO2022142841 A1 WO 2022142841A1
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WO
WIPO (PCT)
Prior art keywords
motor
conduction mode
torque
phase
conduction
Prior art date
Application number
PCT/CN2021/131633
Other languages
English (en)
French (fr)
Inventor
朱宏
鲁志健
Original Assignee
南京泉峰科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 南京泉峰科技有限公司 filed Critical 南京泉峰科技有限公司
Priority to EP21913583.7A priority Critical patent/EP4231519A4/en
Publication of WO2022142841A1 publication Critical patent/WO2022142841A1/zh
Priority to US18/313,062 priority patent/US20230271305A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/16—Circuit arrangements for detecting position
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q5/00—Driving or feeding mechanisms; Control arrangements therefor
    • B23Q5/02—Driving main working members
    • B23Q5/027—Driving main working members reciprocating members
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23Q—DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT
    • B23Q5/00—Driving or feeding mechanisms; Control arrangements therefor
    • B23Q5/02—Driving main working members
    • B23Q5/04—Driving main working members rotary shafts, e.g. working-spindles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25B—TOOLS OR BENCH DEVICES NOT OTHERWISE PROVIDED FOR, FOR FASTENING, CONNECTING, DISENGAGING OR HOLDING
    • B25B21/00—Portable power-driven screw or nut setting or loosening tools; Attachments for drilling apparatus serving the same purpose
    • B25B21/008—Portable power-driven screw or nut setting or loosening tools; Attachments for drilling apparatus serving the same purpose with automatic change-over from high speed-low torque mode to low speed-high torque mode
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
    • B25F—COMBINATION OR MULTI-PURPOSE TOOLS NOT OTHERWISE PROVIDED FOR; DETAILS OR COMPONENTS OF PORTABLE POWER-DRIVEN TOOLS NOT PARTICULARLY RELATED TO THE OPERATIONS PERFORMED AND NOT OTHERWISE PROVIDED FOR
    • B25F5/00—Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
    • B25F5/001—Gearings, speed selectors, clutches or the like specially adapted for rotary tools
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/06—Rotor flux based control involving the use of rotor position or rotor speed sensors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/14—Estimation or adaptation of machine parameters, e.g. flux, current or voltage
    • H02P21/18—Estimation of position or speed
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/22—Current control, e.g. using a current control loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
    • H02P21/24—Vector control not involving the use of rotor position or rotor speed sensors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P6/00—Arrangements for controlling synchronous motors or other dynamo-electric motors using electronic commutation dependent on the rotor position; Electronic commutators therefor
    • H02P6/14—Electronic commutators
    • H02P6/15—Controlling commutation time

Definitions

  • the present application relates to the field of electric tools, in particular to an electric tool and a control method thereof.
  • Permanent magnet motors including inner rotor motors and outer rotor motors, have speed regulation requirements under different load or torque conditions.
  • the commonly used speed regulation methods are generally voltage regulation, field weakening, or sensor position-based speed regulation.
  • the cost of the whole machine for voltage regulation and speed regulation is relatively high, and the field weakening speed regulation is very easy on the electric excitation motor, but cannot be used on the permanent magnet motor, and the speed regulation can only be realized by using the armature effect.
  • the field weakening technology can adjust the speed by changing the lead angle. However, when the lead angle is changed to increase the speed, the load will increase and the output speed will drop rapidly. That is to say, the speed is not stable, and the output torque will also decrease due to the increase of the load. The performance of the motor.
  • the purpose of the present application is to provide an electric tool that can not only ensure the working ability but also effectively increase the rotational speed.
  • An electric tool comprising: a motor including rotor multi-phase stator windings; a drive circuit having a plurality of switching elements for outputting switching signals to drive the motor to rotate; a controller, at least in communication with the drive circuit and the motor constitute an electrical connection; the controller is configured to: acquire the rotor position information of the motor; adjust the synthetic magnetic potential of the motor according to the rotor position information, so that the synthetic magnetic potential corresponds to the motor
  • the output electrical parameters are within the preset parameter range.
  • the controller is configured to: control the conduction state of the driving circuit based on the rotor position information to adjust the stator magnetic potential of the stator winding; based on the rotor magnetic potential of the motor and the adjusted stator
  • the magnetic potential calculates the combined magnetic potential of the motor, so that the output electrical parameter of the motor corresponding to the combined magnetic potential is within a preset parameter range.
  • rotor position detection module for detecting the rotor position of the motor
  • electrical parameter detection module which is electrically connected to the motor and used for detecting the electrical parameters output by the motor.
  • the rotor position detection module includes a Hall sensor.
  • the rotor position detection module is configured to:
  • the rotor position is estimated based on the back electromotive force of the stator winding or the rotor position is estimated based on the phase current of the stator winding.
  • controller is configured to: when the rotor is in a first preset position, control the drive circuit to change the conduction state to increase the stator magnetic potential; when the rotor is in a second preset position When , the driving circuit is controlled to change the conduction state to reduce the stator magnetomotive force.
  • the electrical parameter includes the rotational speed of the motor.
  • the controller is configured to: calculate the first combined magnetic potential in the first direction and the second combined magnetic potential in the second direction based on the rotor magnetic potential of the motor and the adjusted stator magnetic potential, so as to The rotational speed of the motor corresponding to the first combined magnetic potential is within a preset rotational speed range, and the output efficiency of the motor corresponding to the second combined magnetic potential is within a predetermined efficiency range.
  • first direction is perpendicular to the second direction.
  • the motor has three-phase stator windings; the controller is configured to: when the rotor is in a first preset position, control the drive circuit to change the conduction state to make the three-phase stator windings of the motor Both are connected to the power module; when the rotor is in the second preset position, the drive circuit is controlled to change the conduction state so that any two stator windings of the motor are connected to the power module.
  • a control method of an electric tool comprises: a motor including a rotor multi-phase stator winding; a drive circuit having a plurality of switching elements for outputting switching signals to drive the motor to rotate; a controller, at least with The drive circuit and the motor are electrically connected; the control method includes: acquiring rotor position information of the motor; adjusting the combined magnetic potential of the motor according to the rotor position information, so that the combined magnetic potential The corresponding output electrical parameters of the motor are within the preset parameter range.
  • a power tool comprising: a motor with multi-phase windings, each phase winding of the motor can conduct a first electrical angle in a first conduction mode and conduct conduction in a second conduction mode in a selected phase band The second electrical angle; the torque detection module is used to detect the first electromagnetic torque of the motor when the first electrical angle is turned on in the first conduction mode, and the second electrical angle is turned on in the second conduction mode.
  • the controller is configured to: obtain the first electromagnetic torque and the second electromagnetic torque electromagnetic torque, and calculate the total torque of the motor under unit current in the phase band according to the first electromagnetic torque, the second electromagnetic torque and the reluctance torque of the motor; adjust the first electrical angle and the second electrical angle, so that the total torque of the motor per unit current in the phase band is within a preset torque range.
  • the reluctance torque of the motor is a sine-like wave.
  • the first conduction mode includes conduction of any two-phase windings in each phase winding of the motor; the second conduction mode includes conduction of three-phase windings in each phase winding of the motor.
  • the controller is configured to: detect the rotor position of the motor; in the first conduction mode, switch to the second conduction mode when the rotor position reaches a first preset position; In the second conduction mode, the rotor is switched to the first conduction mode when the rotor position reaches the second preset position.
  • the ratio of the first electrical angle to the second electrical angle in the selected phase band is obtained by looking up a table according to the preset torque range.
  • a control method of a power tool comprising: a motor with multi-phase windings, each phase winding of the motor can conduct a first electrical angle in a first conduction mode in a selected phase band, and in a selected phase band The second conduction mode conducts the second electrical angle;
  • the torque detection module is used to detect the first electromagnetic torque of the motor when the first electrical angle is turned on in the first conduction mode, and the second conduction the second electromagnetic torque of the motor when the second electrical angle is turned on in the mode;
  • a controller is at least electrically connected with the torque detection module and the motor;
  • the control method includes: acquiring the first electromagnetic torque and the second electromagnetic torque and according to the first electromagnetic torque, the second electromagnetic torque and the reluctance torque of the motor to calculate the total torque of the motor under the unit current in the phase band; adjust the The first electrical angle and the second electrical angle are such that the total torque of the electric machine per unit current in the phase band is within a preset torque range.
  • the reluctance torque of the motor is a sine-like wave.
  • the first conduction mode includes conduction of any two-phase windings in each phase winding of the motor; the second conduction mode includes conduction of three-phase windings in each phase winding of the motor.
  • the method further includes: detecting the rotor position of the motor; in the first conduction mode, switching to the second conduction mode when the rotor position reaches a first preset position; In the second conduction mode, the rotor is switched to the first conduction mode when the rotor position reaches the second preset position.
  • the ratio of the first electrical angle to the second electrical angle in the selected phase band is obtained by looking up a table according to the preset torque range.
  • An electric power tool comprising: a motor with multi-phase stator windings, each phase winding of the motor can be conducted in a first conduction mode and a second conduction mode in a selected phase band; a torque detection module, with a rotational speed detection module for detecting the rotational speed of the motor; a controller, at least electrically connected with the torque detection module, the rotational speed detection module and the motor; the control The device is configured to: obtain the output torque and rotational speed of the motor; in the first working stage, adjust the electrical angle at which the motor conducts operation in the second conduction mode, so as to maintain the rotational speed of the motor basically Stable state; in the second working stage, the stator winding is controlled to conduct at a first preset electrical angle in the second conduction mode.
  • controller is configured to control the stator winding to conduct in a first conduction mode at a second preset electrical angle in both the first working stage and the second working stage.
  • the controller is configured to: in the first working stage, when the electrical angle at which the motor conducts operation in the second conduction mode reaches a preset angle threshold, controls the stator winding to operate at a predetermined angle. In the second conduction mode, the conduction is conducted at a third preset electrical angle.
  • a current detection module to detect the working current of the motor; the controller is configured to: obtain the working current of the motor, and calculate the change slope of the working current; When the operating current of the motor in a working stage reaches a current threshold value at a first change slope, the stator winding is controlled to be turned on at the first preset electrical angle to make the motor enter the second working stage.
  • the output current of the motor has the first change slope
  • the output current of the motor has a second change slope; the first change The slope is greater than the second change slope
  • the electrical angle at which the stator winding is turned on in the second conduction mode is the second electrical angle.
  • the first preset electrical angle is less than or equal to the maximum electrical angle at which the stator winding conducts in the second conduction mode in the first working stage.
  • the first conduction mode includes conduction of any two-phase windings in each phase winding of the motor; the second conduction mode includes conduction of three-phase windings in each phase winding of the motor.
  • a method for controlling a power tool comprising: a motor with a multi-phase stator winding, each phase winding of the motor can be conducted in a first conduction mode and a second conduction mode in a selected phase band work; a torque detection module for detecting the output torque of the motor; a rotational speed detection module for detecting the rotational speed of the motor; a controller, at least formed with the torque detection module, the rotational speed detection module and the motor
  • the control method includes: obtaining the output torque and rotational speed of the motor; in the first working stage, adjusting the electrical angle at which the motor conducts operation in the second conduction mode, so as to make the motor The rotational speed of the motor is maintained in a substantially stable state; in the second working stage, the stator winding is controlled to conduct at a first preset electrical angle in the second conduction mode.
  • the method further includes: in the first working stage and the second working stage, controlling the stator winding to conduct at a second preset electrical angle in a first conduction mode.
  • the benefit of the present application lies in that the above-mentioned electric tool can effectively take into account both the work performance and the improvement of the rotational speed of the motor by adjusting the magnetic potential of the motor stator.
  • FIG. 1 is a schematic structural diagram of a power tool provided by an embodiment of the present application.
  • FIG. 2 is a circuit block diagram of a power tool provided by an embodiment of the present application.
  • FIG. 3 is a schematic diagram of the change of the magnetic potential in the motor when the two are turned on according to the embodiment of the present application;
  • FIG. 4 is a schematic diagram of the change of the magnetic potential in the motor when the three-to-three conduction provided by the embodiment of the present application;
  • FIG. 5 is a schematic diagram of the conduction mode of the windings in a certain phase band provided by an embodiment of the present application
  • FIG. 6 is a schematic diagram of the synthesis of the magnetic potential provided by the embodiment of the present application.
  • FIG. 7 is a schematic diagram of the conduction mode of a winding combined with a leading angle in a certain phase band provided by an embodiment of the present application;
  • FIG. 8 a is a schematic diagram showing the comparison between the working power and the field weakening capability of the motor provided by the embodiment of the present application;
  • FIG. 8b is a schematic diagram showing the comparison of the working capacity and the field weakening capacity of the motor provided by the embodiment of the present application;
  • FIG. 9 is a circuit block diagram of a power tool provided by an embodiment of the present application.
  • FIG. 10 is a schematic diagram of electromagnetic torque provided by an embodiment of the present application.
  • FIG. 11 is a schematic diagram of electromagnetic torque provided by an embodiment of the present application.
  • FIG. 12 is a schematic diagram of the output performance of tools at different stages provided by an embodiment of the present application.
  • FIG. 13 is a circuit block diagram of a power tool provided by an embodiment of the present application.
  • FIG. 14 is a schematic diagram of output performance of tools at different stages provided by the embodiments of the present application.
  • the electric tools to which the technical solutions of the present application are applicable include grinding tools, electric drills, electric circular saws, reciprocating saws, miter saws and other electric tools that can adopt brushless and non-inductive electric control methods.
  • Other types of electric tools can use the following disclosures
  • the essential content of the technical solution can fall within the protection scope of the present application.
  • the power tool 100 at least includes a casing 10, a motor in the casing (not shown in FIG. 1 ), a bottom plate 12, a transmission mechanism (not shown), a grip Holder 13 and battery pack 14 .
  • the casing 10 has a built-in motor.
  • the casing 10 includes a left casing and a right casing. During assembly, the left and right casings are closed from the left and right directions to the middle and fastened by screws.
  • the motor shaft of the motor is parallel to the base plate 12 and is built into the front end of the tool 100 .
  • the motor drives the transmission mechanism to make the grinding sandpaper fixed on the bottom plate 12 carry out the grinding work.
  • the transmission mechanism is at least used to connect the motor shaft and the output shaft, and can be a two-stage transmission gear.
  • the housing 10 is formed with a grip portion 13 that conforms to ergonomics for the user to hold.
  • the tool 100 also includes an electronic membrane switch for controlling the switch.
  • the battery pack 14 is installed at the rear end of the tool, the longest side of the battery pack 14 is parallel to the plane of the bottom plate, and the overall volume of the tool is small.
  • the drive system of the motor 11 may at least include a drive circuit 20 , a power module 21 , a rotor position detection module 22 , an electrical parameter detection module 23 and a controller 24 .
  • the motor 11 is a brushless DC motor (BLDC). In one embodiment, the motor 11 is a non-inductive BLDC. In one embodiment, the motor 11 is an inductive BLDC.
  • the brushless DC motor may be an inner rotor motor or an outer rotor motor, and the motor 11 at least includes three-phase stator windings A, B, and C, and the three-phase windings may be star-connected or delta-connected.
  • motor speed regulation for BLDCs with Hall sensors or other hardware devices that detect the rotor position, the sensor can be directly used to detect the rotor position, and the motor speed can be adjusted according to the rotor position.
  • non-inductive BLDC since there is no sensor to detect the rotor position in the motor, the rotor position can be detected by detecting the back electromotive force of the winding or other methods.
  • the non-inductive BLDC cannot accurately know the position of the rotor when it is started or loaded at low speed, which will lead to unstable output torque.
  • the speed regulation of non-inductive BLDC is generally controlled by means of field weakening or voltage regulation. The cost of speed regulation by voltage regulation is high, while the traditional weak field speed regulation will greatly reduce the working capacity of the motor.
  • the above problems can be solved by adopting the method of adjusting the stator magnetic potential for speed control.
  • the motor speed can also be adjusted by adjusting the stator magnetic potential.
  • the power source can be selected as an AC power source, so that the power module 21 can be connected to 120V or 220V AC mains.
  • the power source can be selected as a battery pack, and the battery pack can be composed of a group of battery cells.
  • the battery cells can be connected in series to form a single power supply branch to form a 1P battery pack.
  • the output voltage of the battery pack is changed by a specific power control module, such as a DC-DC module, to output a power supply voltage suitable for the drive circuit 20, the motor 11, etc. to supply power.
  • a specific power control module such as a DC-DC module
  • the DC-DC module is a mature circuit structure, and can be selected according to the specific parameter requirements of the electric tool.
  • the rotor position detection module 22 is used to identify the rotor position.
  • the rotor position detection module 22 may include Hall sensors for detecting rotor position.
  • the rotor position detection module 22 may estimate the rotor position based on motor parameters such as floating phase voltage or phase current.
  • the rotor position detection module may also include any other method or hardware device capable of detecting the rotor position.
  • the electrical parameter detection module 23 can detect the electrical parameters in the working process of the motor 11 in real time, such as the rotational speed of the motor.
  • the electrical parameter detection module 23 may also detect the output torque of the motor, or detect the work efficiency of the motor based on the rotational speed and torque.
  • the driving circuit 20 is electrically connected to the stator windings A, B, and C of the motor 11 , and is used to transmit the current from the power module 21 to the stator windings A, B, and C to drive the motor 11 to rotate.
  • the driving circuit 20 includes a plurality of switching elements Q1 , Q2 , Q3 , Q4 , Q5 , and Q6 .
  • the gate terminal of each switching element is electrically connected to the controller 23 for receiving a control signal from the controller 23 .
  • the drain or source of each switching element is connected to the stator windings A, B, C of the electric machine 11 .
  • the switching elements Q1-Q6 receive control signals from the controller 23 to change their respective conduction states, thereby changing the currents applied by the power module 21 to the stator windings A, B, and C of the motor 11 .
  • the driver circuit 20 may be a three-phase bridge driver circuit including six controllable semiconductor power devices (eg, FETs, BJTs, IGBTs, etc.). It can be understood that the above switching elements can also be any other types of solid state switches, such as insulated gate bipolar transistors (IGBTs), bipolar junction transistors (BJTs) and the like.
  • IGBTs insulated gate bipolar transistors
  • the drive circuit 20 has multiple drive states, and the controller 24 can output the corresponding PWM drive signal through the position information of the rotor to control the switching elements in the drive circuit 20 to switch the drive circuit to the conduction state, thereby changing the motor stator The conducting phase of the winding and the magnitude and direction of the current in the conducting winding. It should be noted that different conduction phases of the stator windings and changes in the magnitude and direction of the energized current in the windings will result in changes in the magnitude and direction of the stator magnetic potential.
  • Figure 3 shows the change of the magnetic potential during the commutation process of two-phase conduction in the three-phase winding of the three-phase non-inductive BLDC, that is, the two-phase conduction, where the magnetic potential includes the rotor magnetic potential of the motor and the stator magnetic potential of the stator windings
  • the motor performs a commutation, that is, each phase winding occupies a 60° phase band, and the rotor corresponds to different position information in six different phase bands, and the PWM drive signal output by the controller 24 can correspond to Six different signal combinations.
  • the signal 0 is used to represent the state of the winding being turned off
  • the signal 1 is used to represent the state of the winding being turned on.
  • the dotted line in FIG. 3 represents the Hall scale formed when the Hall positions of the three-phase windings are respectively parallel to the rotor direction. Under the Hall scale, the Hall position of the stator winding can be determined with the change of the rotor position. Specifically, the Hall position of the three-phase windings, the combined form of the PWM signal output by the controller and the conduction state of the corresponding stator windings are shown in Table 1:
  • Hall location PWM signal combination Stator winding conduction state (0,1,0) (1, 0, X) A+B-
  • 0 below the Hall position indicates that the Hall position of the corresponding winding falls at the S stage of the rotor
  • 1 below the Hall position indicates that the Hall position of the corresponding winding falls at the N stage of the rotor.
  • 0 in the following PWM signal combination means the lower tube of the corresponding winding is turned on
  • 1 in the following PWM signal combination means the upper tube of the corresponding winding is turned on
  • X in the following PWM signal combination means that the upper and lower tubes of the corresponding winding are not turned on.
  • the rotor magnetic potential in the process of rotor rotation. changing direction, The size of the stator remains unchanged; while the stator magnetic potential It is synthesized by the magnetic potential of the conducting two-phase stator windings, and its direction changes with the commutation of the stator windings, and its magnitude is also related to the conducting direction and conducting current of the conducting phase windings.
  • the rotor rotates within the phase band of 30° to 90°, the A and B windings are turned on in the manner of A+B-, and the rotor magnetic potential In the direction parallel to the rotor, the stator magnetic potential It is synthesized by the magnetic potential of the A and B phase windings, namely The commutation occurs every time the rotor rotates by 60 electrical degrees.
  • the commutation process of the rotor according to the driving signal shown in Table 1 corresponds to the commutation process indicated by the arrow in Figure 3.
  • the corresponding rotor magnetic potential and stator magnetic potential are also shown in the figure. 3 changes as shown.
  • Figure 4 shows the three-phase non-inductive BLDC, and the change process of the magnetic potential when the three-phase windings are all turned on, that is, when the three-phase windings are turned on.
  • Table 2 shows the correspondence between the Hall position, the PWM signal and the conduction state of the motor stator windings when the three-phase windings are all turned on:
  • Hall location PWM signal combination Stator winding conduction state (0,1,0) (1, 0, 0) A+B-C- (0, 1, 1) (1, 1, 0) A+B+C-
  • the rotor magnetic potential in the process of rotor rotation. changing direction, The size of the stator remains unchanged; while the stator magnetic potential It is synthesized by the magnetic potential of the three-phase stator windings that are turned on, and its direction changes with the commutation of the stator windings, and its magnitude is also related to the conduction direction of the three-phase windings and the conduction current.
  • the PWM signal output by the controller in Figure 4 is (1, 0, 0)
  • the rotor rotates within a phase of 30° to 90°, and the A, B, and C windings are turned on in the manner of A+BC-.
  • Rotor magnetic potential In the direction parallel to the rotor, the stator magnetic potential It is synthesized by the magnetic potential of the A, B, and C phase windings, that is, The commutation occurs every time the rotor rotates by 60 electrical degrees.
  • the commutation process of the rotor according to the driving signal shown in Table 2 corresponds to the commutation process indicated by the arrow in Figure 4.
  • the corresponding rotor magnetic potential and stator magnetic potential are also shown in the figure. 4 changes as shown.
  • the conduction mode of the stator windings of the motor affects the magnitude of the stator magnetic potential.
  • the stator magnetic potential when all three-phase windings are turned on is greater than the stator magnetic potential when the windings are turned on. Therefore, in order to obtain a larger stator magnetic potential in the selected phase band, the controller 24 can change the PWM signal to control the stator windings to work in a combined conduction mode of two-to-two conduction and three-to-three conduction. Specifically, as shown in Fig.
  • the stator windings of the motor can be controlled to conduct electrical angles of ⁇ ° in a three-to-three conduction mode, and conduct 60- ⁇ ° in a two-to-two conduction mode.
  • Electrical angle define ⁇ as the expansion angle.
  • the two-by-two conduction process in the selected phase band can be continuous or discontinuous.
  • the so-called selected phase band may be a selected phase band of any size, and the size of the selected phase band is not limited in this embodiment of the present application.
  • the combined magnetic potential of the motor can be obtained by the stator magnetic potential and the rotor magnetic potential in a certain combined manner.
  • the first direction of the position of the rotor is defined as the straight axis
  • the second direction perpendicular to the straight axis is defined as the quadrature axis.
  • Components of the stator magnetic potential on the direct and quadrature axes and After being combined with the rotor magnetic potential, a first combined magnetic potential in the direct axis direction and a second combined magnetic potential in the quadrature axis direction can be formed. It should be noted that the size of the included angle ⁇ between the rotor magnetic potential and the stator magnetic potential shown in FIG.
  • the motor 6 can represent the current excitation capability of the motor.
  • the angle ⁇ between the rotor magnetic potential and the stator magnetic potential is an obtuse angle
  • the motor has the ability to weaken the magnetic field
  • the angle ⁇ is an acute angle
  • the motor has the strong magnetic ability.
  • the included angle ⁇ is an obtuse angle.
  • the first resultant magnetic potential is on the straight axis and synthesis, as long as the synthesized magnetic potential is compared to the original
  • the size of the first combined magnetic potential represents the field weakening ability of the motor.
  • the speed of the motor can be adjusted; Component of the potential on the quadrature axis Based on the angle between the stator magnetomotive force and the quadrature axis shown in Figure 6 as ⁇ , due to the electromagnetic torque of the motor where K is a fixed value, W is the magnetic residual energy, and Thus the electromagnetic torque That is, the electromagnetic torque is related to the component of the stator magnetomotive force on the quadrature axis, so the magnitude of the second combined magnetomotive force represents the working power of the motor.
  • the magnitude of the second synthetic magnetic potential the purpose of adjusting the electromagnetic torque and thus affecting the working power of the motor can be achieved.
  • the stator magnetic potential can be adjusted to make the second combined magnetic potential reach the expected value. That is to say, the present application can ensure the working capability of the motor, that is, the power output efficiency of the motor, on the premise of increasing the rotational speed of the motor.
  • the output efficiency of the motor is the efficiency of the power output of the motor, which can represent the working capability of the motor.
  • the rotor position has a corresponding relationship with the rotor magnetic potential.
  • the combined magnetic potential of the two can be adjusted by adjusting the stator magnetic potential, thereby controlling the electrical parameters output by the motor.
  • the lead conduction angle ⁇ may be set. That is to say, whether in the two-two conduction mode or the three-three conduction mode, the windings have a leading conduction angle ⁇ .
  • the horizontal axis is the expansion angle
  • the vertical axis of Fig. 8a represents the working capability of the motor
  • the vertical axis of Fig. 8b represents the excitation capability of the motor.
  • the excitation capability includes Strong magnetic ability and weak magnetic ability.
  • the range of the spread angle ⁇ is 0 to ⁇ /3. However, even at ⁇ /3, the difference between line 1 and line 3 is less than 0.2, that is to say, the increase The lead angle has little effect on the performance of the motor to a certain extent. It can be seen from Figure 8b that setting the expansion angle ⁇ can increase the field weakening ability of the motor, and on this basis, increasing the lead angle ⁇ will greatly improve the field weakening ability of the motor. To sum up, it can be seen that the use of a suitable expansion angle can achieve a balance between the motor's field weakening capability and working power, and can increase the motor speed on the premise of ensuring the working power.
  • the controller 24 can obtain the rotor position information. Since the conduction modes of the stator windings are different in different rotor positions, the stator magnetic potential is different under different conduction modes of the windings. Therefore, the controller 24 can control the change of the conduction state of the windings according to the rotor position information to adjust the stator magnetic potential, and then can determine the combined magnetic potential of the motor according to the rotor magnetic potential and the adjusted stator magnetic potential, and under the combined magnetic potential.
  • the electrical parameters output by the motor are within the preset parameter range. That is to say, the motor can meet certain rotational characteristics by adjusting the synthetic magnetic potential of the motor.
  • the electrical parameter of the motor may be the speed of the motor, or the power output determined based on the speed and torque.
  • the controller can adjust the conduction mode of the electronic winding according to the rotor position information, so that the speed of the motor can reach a certain speed or increase the speed of the motor to a certain range, and at the same time ensure that the motor has a good power output efficiency .
  • the conduction modes of the windings include two-to-two conduction and/or three-to-three conduction and/or a combination of two-to-two conduction and three-to-three conduction, as well as expansion angles and/or lead angles under different conduction modes.
  • the controller 24 can increase the stator magnetic potential by controlling the three-phase stator windings of the motor to be connected to the power module; when the rotor is at the second preset position, control The controller 24 can reduce the stator magnetic potential by controlling any two stator windings of the motor to be connected to the power module.
  • increasing the stator magnetic potential may be maintaining the current direction of the stator magnetic potential unchanged, increasing the magnitude of the stator magnetic potential, or changing the direction of the stator magnetic potential while increasing its magnitude.
  • reduce the stator magnetic potential it is also possible to keep the current direction of the stator magnetic potential unchanged, reduce the stator magnetic potential to zero or to a certain value, or change the stator direction while reducing the stator magnetic potential to zero or to a certain value.
  • the controller when the rotor is in the first preset position, can control the stator windings to switch from the two-to-two conduction mode to the three-to-three conduction mode, and when the rotor is in the second preset position, control the stator windings to switch from the three-to-three conduction mode The conduction mode is switched to the pairwise conduction mode.
  • the two-two conduction mode or the three-three conduction mode can be switched multiple times, so the above-mentioned first preset position and second preset position are not a fixed rotor position, but It is the position of the rotor when the electric parameter exceeds the preset range due to the change of the synthetic magnetic potential of the motor during the rotation of the rotor.
  • the controller identifies the current rotor position through the rotor position detection module 22 and determines whether the current position is the first preset position or the second preset position.
  • the stator magnetic potential can be adjusted by detecting the rotor position information and adjusting the conduction number of the stator windings, thereby affecting the combined magnetic potential, that is, affecting the first combined magnetic potential and the second combined magnetic potential. , in order to increase the motor speed under the premise of less impact on the motor performance.
  • the conduction mode of the three-phase non-inductive BLDC stator windings in the selected phase band can be switched according to the rotor position information. switch between the second conduction mode of the pass.
  • the two-phase stator windings conduct a first electrical angle in the first conduction mode, that is, the two-phase conduction mode
  • the three-phase stator windings conduct conduction in the second conduction mode, that is, the three-phase conduction mode.
  • the motor conducts the first electrical angle in the first conduction mode, there is a first electromagnetic torque
  • the motor conducts the second electrical angle and has the second electromagnetic torque.
  • the so-called electromagnetic torque is the output torque of the motor, which can characterize the working ability of the motor.
  • the motor itself has a reluctance torque that affects the working power of the motor
  • the reluctance torque and the electromagnetic torque under different conduction modes together constitute the total torque of the motor, and the total torque can accurately reflect the working power of the motor. It can be understood that the greater the total torque of the motor per unit current, the more power saving the tool will be. Therefore, the energy consumption can be further reduced on the premise of ensuring the motor's functional capability and increasing the motor speed.
  • the power tool shown in FIG. 9 also includes a torque detection module 25 for detecting the output torque of the motor under different conduction modes of the stator winding.
  • the torque detection module 25 can also detect the reluctance torque of the motor, wherein the reluctance torque is caused by the difference in the reluctance of the direct axis and the quadrature axis of the rotor in the motor.
  • the horizontal axis represents the angle of rotation of the rotor, and the vertical axis represents the magnitude of the torque.
  • Line 1 is the total torque of the motor in the first conduction mode
  • line 2 is the second conduction mode.
  • line 3 is the first electromagnetic torque of the motor in the first conduction mode
  • line 4 is the second electromagnetic torque of the motor in the second conduction mode
  • line 5 is the reluctance torque of the motor.
  • the reluctance torque of the motor is a sine-like waveform, that is to say, the reluctance torque can increase the total torque of the motor within a certain electrical angle, and can reduce the total torque of the motor within a certain electrical angle, so
  • Figure 10 The shaded area in the middle represents the interval range of the rotor rotation angle when the motor has the maximum total torque, and the range of this interval is 90° to 135°. That is to say, the definition domain of the motor with the maximum total torque is 90° to 135°.
  • the two shaded intervals shown in Figure 11 respectively represent the first total torque when the first conduction mode is adopted and the second total torque when the second conduction mode is adopted under the unit current, and the sum of the two is the final The total torque of the motor required. That is to say, when the sum of the areas of the two shaded areas shown in FIG. 11 is the largest, it corresponds to the maximum total torque of the motor under the unit current.
  • the controller 24 can adjust the first electrical angle of conduction in the first conduction mode and the second electrical angle of conduction in the second conduction mode according to the position of the rotor of the motor, so that the motor is within the selected phase band
  • the total torque per unit current is within the preset torque range. It can be understood that the energy consumption of different tools is different, and the preset torque is also different, and the preset torque range in this application can cover the total torque value of the motor corresponding to different energy consumption requirements of different tools.
  • the ratio of the first electrical angle and the second electrical angle in the selected phase band can be obtained by looking up a table according to a preset torque range.
  • the conduction mode of the motor stator winding can be controlled to ensure that the power tool has stable output performance and large output power under different working conditions.
  • the operation stage of a general tool can be divided into a high-speed operation stage and a low-speed operation stage.
  • the minimum speed of the motor is different in the high-speed operation stage of different tools under different working conditions, and the maximum speed of the motor in the low-speed operation stage of different tools is also different. different.
  • the high operation phase is defined as the first operation phase of the tool operation
  • the low speed operation phase is defined as the second operation phase of the tool operation.
  • the motor maintains a constant rotational speed for a period of time and continues to work for a period of time, and the motor is transferred to the second working stage before the working parameters of the motor are overloaded.
  • the motor adopts the conduction mode of two-to-two conduction and three-to-three conduction switching to control the operation of the motor. Therefore, in order to obtain a basically stable rotational speed in the first working stage, the controller adjusts the motor in the first working stage to The second conduction mode, namely the three-to-three conduction mode, conducts the second electrical angle ⁇ of the operation, so as to maintain the rotational speed of the motor in a basically stable state; further, in the second working stage, the stator winding can be controlled to conduct three-to-three conduction.
  • the conduction is conducted at the first preset electrical angle, that is, the conduction is conducted at a fixed electrical angle.
  • the motor in the first working stage and the second working stage, the motor is switched between two-two conduction and three-three conduction, that is, in both working stages, the motor has two-two conduction and three-three conduction.
  • the electrical angles of the two conductions in the two working stages are all fixed values, such as the second preset electrical angle. Therefore, the present application does not describe the electrical angle of the two-by-two conduction mode of the motor in the two working stages.
  • the electrical angle of the three-to-three conduction of the tool in the high-speed operation stage is constantly changing, and the electrical angle of the three-to-three conduction of the tool is fixed in the low-speed operation stage, and the electrical angle of the two-to-two conduction of the windings in the two operation stages is Fixed value.
  • the sizes of the first preset electrical angle and the second preset electrical angle are not specifically limited.
  • the controller 24 adjusts the electrical angle (expansion angle ⁇ ) of the stator windings of the motor in the second conduction mode, that is, the three-to-three conduction, while keeping the stator windings conducting at a fixed lead angle ⁇ , so that the Keep the speed of the motor basically unchanged.
  • the stator winding has a lead angle of 15°, and the expansion angle of the three-way conduction changes from 0° to 45°, so the speed of the motor can be maintained in a relatively stable state.
  • the horizontal axis represents the output torque T of the motor
  • the vertical axis represents the motor speed n.
  • the motor speed and output torque remain basically unchanged, and the line 1 is basically parallel to the abscissa axis.
  • the current rising rate of the motor is faster, and the motor will bear a larger current in a short period of time, so the maintenance time of the first working stage should not be too long.
  • the controller 24 can make the stator winding of the motor conduct at the third preset electrical angle by stopping the adjustment of the electrical angle in the first conduction mode, At the same time, continue to maintain a constant lead angle ⁇ to reduce the speed of the motor and reduce the change slope of the working current of the motor, so that the motor enters the second working stage.
  • the third preset electrical angle is a fixed electrical angle, and the size of the third preset electrical angle is not specifically limited in this application. It can be understood that if the motor maintains a high speed all the time, it will cause serious heat generation. Therefore, when the speed needs to be reduced, the controller can control the motor to enter the second working stage.
  • the controller may control the motor to enter the second working stage when the conduction angle of the second conduction mode reaches an angle threshold. For example, when the expansion angle changes from 0° to 45° in the first working stage, the controller 24 no longer adjusts the expansion angle, so that the motor windings are turned on at a lead angle of 15° and a fixed expansion angle less than or equal to 45°. The second stage of work.
  • the power tool further includes a current detection module 26 for detecting the working current of the motor.
  • the controller 24 obtains the working current of the motor, the change slope of the current can be calculated. Further, the controller can control the motor to switch to the second working stage according to the change slope of the motor current in the first working stage, that is, control the electrical angle of the second conduction mode of the stator winding of the motor to be the first preset electrical angle. That is to say, in the second working stage, the lead angle ⁇ of the motor stator winding and the expansion angle ⁇ when the three-thirds are turned on are both fixed values.
  • the working current of the motor has a first change slope in the first working stage and a second change slope in the second working stage, as shown in FIG. 14 , the horizontal axis represents the motor output torque, and the vertical axis represents the motor operating current , it can be seen from FIG. 14 that the second change slope of the motor current in the second working stage is significantly smaller than the first change slope in the first working stage. 12 and 14, it can be seen that in the second working stage, the current change slope becomes smaller, but the working current value does not decrease, and the motor speed decreases.
  • the controller 24 when the controller 24 detects that the motor operating current reaches the current threshold at the first change slope in the first working stage of the motor, it can control the motor to switch to the second working stage, that is, the expansion angle ⁇ is no longer adjusted. It can be understood that in the first working stage, when the working current of the motor reaches the current threshold at the first change slope, the expansion angle ⁇ of the motor windings is the maximum current that can be achieved in the second conduction mode. angle. In the second working stage, the fixed second electrical angle of the three-to-three conduction is less than or equal to the above-mentioned maximum electrical angle.
  • the controller controls the motor to 15° lead angle and fixed
  • the expansion angle of less than or equal to 20° is turned on and enters the second working stage. That is, when the motor operating current reaches the current threshold at the first current slope in the first working stage, and the electrical angle in the second conduction mode is less than the angle threshold, the controller still controls the motor to enter the second working stage.

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Abstract

一种电动工具及其控制方法，电动工具包括电机，电机包括转子和多相定子绕组；驱动电路，具有多个开关元件用于输出开关信号以驱动电机转动；控制器，至少与驱动电路和电机构成电性连接；控制器被配置为：获取电机的转子位置信息；根据该转子位置信息调整电机的合成磁势，以使所述合成磁势对应的电机的输出电参量处于预设参数范围内。

Description

电动工具及其控制方法
本申请要求在2020年12月30日提交中国专利局、申请号为202011630527.4的中国专利申请的优先权，要求在2020年12月30日提交中国专利局、申请号为202011630511.3的中国专利申请的优先权，要求在2020年12月30日提交中国专利局、申请号为202011630501.X的中国专利申请的优先权，该三件申请的全部内容通过引用结合在本申请中。
技术领域
本申请涉及电动工具领域，具体涉及一种电动工具及其控制方法。
背景技术
永磁式电动机，包括内转子电机和外转子电机都有不同负载或扭矩情况下的调速需求。常用的调速方式一般是调压调速、弱磁调速或者基于传感器位置的调速。然而，调压调速的整机成本较高、弱磁调速在电励磁式电机上非常容易，在永磁式电机上无法使用只能利用电枢效应实现调速。
弱磁技术可通过改变超前角实现转速调节，然而在改变超前角提高转速时会导致负载增加输出转速快速下降，也就是说，转速并不稳定，同时由于负载增加也会导致输出扭矩的下降影响电机的做功能力。
发明内容
为解决相关技术的不足，本申请的目的在于提供一种既能保证做功能力又能有效提高转速的电动工具。
本申请采用如下的技术方案：
一种电动工具，包括：电机，包括转子多相定子绕组；驱动电路，具有多个开关元件，用于输出开关信号以驱动所述电机转动；控制器，至少与所述驱动电路和所述电机构成电性连接；所述控制器被配置为：获取所述电机的转子位置信息；根据所述转子位置信息调整所述电机的合成磁势，以使所述合成磁势对应的所述电机的输出电参量处于预设参数范围内。
进一步的，所述控制器被配置为：基于所述转子位置信息控制所述驱动电路的导通状态以调整所述定子绕组的定子磁势；基于所述电机的转子磁势和调整后的定子磁势计算所述电机的合成磁势，以使所述合成磁势对应的所述电机的输出电参量处于预设参数范围内。
进一步的，还包括转子位置检测模块，用于检测所述电机的转子位置；电参量检测模块，与所述电机电性连接，用于检测所述电机输出的电参量。
进一步的，所述转子位置检测模块包括霍尔传感器。
进一步的，所述转子位置检测模块被配置为：
基于所述定子绕组的反电动势估算所述转子位置或者基于所述定子绕组的相电流估算所述转子位置。
进一步的，所述控制器被配置为：在所述转子处于第一预设位置时，控制所述驱动电路改变导通状态以增加所述定子磁势；在所述转子处于第二预设位置时，控制所述驱动电路改变导通状态以降低所述定子磁势。
进一步的，所述电参量包括电机的转速。
进一步的，所述控制器被配置为：基于所述电机的转子磁势和调整后的定子磁势计算第一方向上的第一合成磁势和第二方向上的第二合成磁势，以使所述第一合成磁势对应的所述电机的转速处于预设转速范围内，并使所述第二合成磁势对应的所述电机的出功效率处于预设效率范围内。
进一步的，所述第一方向垂直于所述第二方向。
进一步的，所述电机具有三相定子绕组；所述控制器被配置为：在所述转子处于第一预设位置时，控制所述驱动电路改变导通状态使所述电机的三相定子绕组均导通接入所述电源模块；在所述转子处于第二预设位置时，控制所述驱动电路改变导通状态使所述电机的任意两项定子绕组导通接入所述电源模块。
一种电动工具的控制方法，所述电动工具包括包括：电机，包括转子多相定子绕组；驱动电路，具有多个开关元件，用于输出开关信号以驱动所述电机转动；控制器，至少与所述驱动电路和所述电机构成电性连接；所述控制方法包括：获取所述电机的转子位置信息；根据所述转子位置信息调整所述电机的合成磁势，以使所述合成磁势对应的所述电机的输出电参量处于预设参数范围内。
一种电动工具，包括：电机，具有多相绕组，所述电机的各相绕组在选定相带内能够以第一导通方式导通第一电角度，并以第二导通方式导通第二电角度；扭矩检测模块，用于检测所述第一导通方式下导通第一电角度时所述电机的第一电磁扭矩，和所述第二导通方式下导通第二电角度时所述电机的第二电磁扭矩；控制器，至少与所述扭矩检测模块和所述电机构成电性连接；所述控制器被配置为：获取所述第一电磁扭矩和所述第二电磁扭矩，并依据所述第一电磁扭矩、所述第二电磁扭矩和所述电机的磁阻扭矩计算所述电机在所述相带 内单位电流下的总扭矩；调整所述第一电角度和所述第二电角度，以使所述电机在所述相带内单位电流下的总扭矩处于预设扭矩范围内。
进一步的，所述电机的磁阻扭矩为类正弦波。
进一步的，所述第一导通方式包括电机各相绕组中任意两相绕组导通；所述第二导通方式包括电机各相绕组中三相绕组导通。
进一步的，所述控制器被配置为：检测所述电机的转子位置；在所述第一导通方式下，所述转子位置达到第一预设位置处时切换至第二导通方式；在所述第二导通方式下，所述转子位置达到第二预设位置处时切换至第一导通方式。
进一步的，在选定相带内所述第一电角度和所述第二电角度的比值根据所述预设扭矩范围通过查表的方式获得。
一种电动工具的控制方法，所述电动工具包括：电机，具有多相绕组，所述电机的各相绕组在选定相带内能够以第一导通方式导通第一电角度，并以第二导通方式导通第二电角度；扭矩检测模块，用于检测所述第一导通方式下导通第一电角度时所述电机的第一电磁扭矩，和所述第二导通方式下导通第二电角度时所述电机的第二电磁扭矩；控制器，至少与所述扭矩检测模块和所述电机构成电性连接；所述控制方法包括：获取所述第一电磁扭矩和所述第二电磁扭矩并依据所述第一电磁扭矩、所述第二电磁扭矩和所述电机的磁阻扭矩计算所述电机在所述相带内单位电流下的总扭矩；调整所述第一电角度和所述第二电角度，以使所述电机在所述相带内单位电流下的总扭矩处于预设扭矩范围内。
进一步的，所述电机的磁阻扭矩为类正弦波。
进一步的，所述第一导通方式包括电机各相绕组中任意两相绕组导通；所述第二导通方式包括电机各相绕组中三相绕组导通。
进一步的，所述方法还包括：检测所述电机的转子位置；在所述第一导通方式下，所述转子位置达到第一预设位置处时切换至第二导通方式；在所述第二导通方式下，所述转子位置达到第二预设位置处时切换至第一导通方式。
进一步的，在选定相带内所述第一电角度和所述第二电角度的比值根据所述预设扭矩范围通过查表的方式获得。
一种电动工具，包括：电机，具有多相定子绕组，所述电机的各相绕组在选定相带内能够以第一导通方式和第二导通方式导通工作；扭矩检测模块，用于检测所述电机的输出扭矩；转速检测模块，用于检测所述电机的转速；控制器，至少与所述扭矩检测模块、所述转速检测模块和所述电机构成电性连接；所述控制器被配置为：获取所述电机的输出扭矩和转速；在第一工作阶段中，调整所述电机以所述第二导通方式导通工作的电角度，以使所述电机的转速维 持基本稳定状态；在所述第二工作阶段中，控制所述定子绕组在所述第二导通方式下以第一预设电角度导通。
进一步的，所述控制器被配置为：在所述第一工作阶段和所述第二工作阶段中均控制所述定子绕组在第一导通方式下第二预设电角度导通。
进一步的，所述控制器被配置为：在所述第一工作阶段中，所述电机以所述第二导通方式导通工作的电角度达到预设角度阈值时，控制所述定子绕组在所述第二导通方式下以第三预设电角度导通。
进一步的，还包括：电流检测模块，用以检测所述电机的工作电流；所述控制器被配置为：获取所述电机的工作电流，并计算所述工作电流的变化斜率；在所述第一工作阶段中所述电机的工作电流达到第一变化斜率下的电流阈值时，控制所述定子绕组以所述第一预设电角度导通使所述电机进入所述第二工作阶段。
进一步的，在所述第一工作阶段内所述电机的输出电流具有所述第一变化斜率，在所述第二工作阶段内所述电机的输出电流具有第二变化斜率；所述第一变化斜率大于所述第二变化斜率。
进一步的，在所述第一工作阶段中所述电机的工作电流达到第一变化斜率下的电流阈值时，所述定子绕组以所述第二导通方式导通的电角度为所述第二导通方式下能够达到的最大电角度。
进一步的，所述第一预设电角度小于或等于所述定子绕组在所述第一工作阶段中以所述第二导通方式导通的最大电角度。
进一步的，所述第一导通方式包括电机各相绕组中任意两相绕组导通；所述第二导通方式包括电机各相绕组中三相绕组导通。
一种电动工具的控制方法，所述电动工具包括：电机，具有多相定子绕组，所述电机的各相绕组在选定相带内能够以第一导通方式和第二导通方式导通工作；扭矩检测模块，用于检测所述电机的输出扭矩；转速检测模块，用于检测所述电机的转速；控制器，至少与所述扭矩检测模块、所述转速检测模块和所述电机构成电性连接；所述控制方法包括：获取所述电机的输出扭矩和转速；在第一工作阶段中，调整所述电机以所述第二导通方式导通工作的电角度，以使所述电机的转速维持基本稳定状态；在所述第二工作阶段中，控制所述定子绕组在所述第二导通方式下以第一预设电角度导通。
进一步的，所述方法还包括：在所述第一工作阶段和所述第二工作阶段中控制所述定子绕组在第一导通方式下以第二预设电角度导通。
本申请的有益之处在于：采用上述电动工具通过调整电机定子磁势能够有 效兼顾电机的做功性能和转速的提升。
附图说明
图1是本申请实施例提供的一种电动工具的结构示意图；
图2是本申请实施例提供的一种电动工具的电路框图；
图3是本申请实施例提供的两两导通时电机中磁势变化示意图；
图4是本申请实施例提供的三三导通时电机中磁势变化示意图；
图5是本申请实施例提供的一定相带内绕组导通方式示意图；
图6是本申请实施例提供的磁势合成示意图；
图7是本申请实施例提供的一定相带内结合超前角的绕组导通方式示意图；
图8a是本申请实施例提供的电机做功能力和弱磁能力对比示意图；
图8b是本申请实施例提供的电机做功能力和弱磁能力对比示意图；
图9是本申请实施例提供的一种电动工具的电路框图；
图10是本申请实施例提供的电磁扭矩的示意图；
图11是本申请实施例提供的电磁扭矩的示意图；
图12是本申请实施例提供的不同阶段工具的输出性能示意图；
图13是本申请实施例提供的一种电动工具的电路框图；
图14是本申请实施例提供的不同阶段工具的输出性能示意图。
具体实施方式
以下结合附图和具体实施例对本申请作具体的介绍。可以理解的是，此处所描述的具体实施例仅仅用于解释本申请，而非对本申请的限定。另外还需要说明的是，为了便于描述，附图中仅示出了与本申请相关的部分而非全部结构。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本申请说明书中所使用的术语只是为了描述具体的实施例，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
本申请的技术方案所适用的电动工具包括打磨工具、电钻、电圆锯、往复锯、斜锯等任何可采用无刷无感电控方式的电动工具，其他类型的电动工具只要能够采用以下披露的技术方案的实质内容即可落在本申请的保护范围内。
在本申请实施例中，参考图1以砂光机为例，电动工具100至少包括机壳10、壳体内的电机(图1未示出)、底板12、传动机构(未示出)、握持部13、电池包14。
机壳10中内置电机，在一个实施例中，壳体10包括左壳体和右壳体，组装时左右壳体分别从左右两个方向向中间盖合，并通过螺钉紧固。在一个实施例中，电机的电机轴平行于底板12，内置在工具100的前端。电机驱动传动机构使底板12上固定的打磨砂纸进行打磨工作。其中，传动机构至少用于连接电机轴和输出轴，可以是两级传动齿轮。壳体10上形成有符合人机工程供用户握持的握持部13。工具100还包括用于控制开关机的电子薄膜开关。电池包14安插在工具后端，电池包14的最长边平行于底板平面，工具整体体积较小。
参考图2所示的电动工具的电路框图，电机11的驱动系统至少可以包括驱动电路20、电源模块21，转子位置检测模块22、电参量检测模块23和控制器24。
在一个实施例中，电机11为无刷直流电机(BLDC)。在一个实施例中，电机11为无感BLDC。在一个实施例中，电机11为有感BLDC。在本申请中，无刷直流电机可以是内转子电机也可以是外转子电机，电机11至少包括三相定子绕组A、B、C，三相绕组可以是星型连接也可以是三角形连接。在电机调速中，对于有霍尔传感器或者其他检测转子位置的硬件装置的BLDC，可以直接采用传感器检测转子位置，根据转子位置调整电机转速。然而对于无感BLDC，由于电机中不存在检测转子位置的传感器，可通过检测绕组的反电动势或者其他方式检测转子位置。但无感BLDC在启动或者低速带载时不能准确获知转子的位置，会导致输出扭矩不稳定。针对无感BLDC的调速一般是采用弱磁或者调压的方式调控，采用调压方式调速成本较高，而传统的弱磁调速会大大降低电机的做功能力。在本申请中，通过采用调整定子磁势的方式进行调速控制，可以解决上述问题。当然，在有感BLDC中也可以采用调整定子磁势的方式调整电机转速。
在一个实施例中，电源可选择为交流电源，从而电源模块21可以接入120V或220V的交流市电。在一个实施例中，电源可选择为电池包，电池包可由一组电池单元组成，例如，可将电池单元串联成单一电源支路，形成1P电池包。电池包输出电压通过具体的电源控制模块，例如DC-DC模块进行电压变化，输出适合驱动电路20、电机11等的供电电压，为其供电。本领域技术人员可理解，DC-DC模块为成熟的电路结构，可根据电动工具具体参数要求而相应选择。
转子位置检测模块22，用于识别转子位置。在一个实施例中，转子位置检测模块22可以包括霍尔传感器，用于检测转子位置。在一个实施例中，转子位 置检测模块22可以基于浮空相电压或者相电流等电机参数估算转子的位置。在本申请中，转子位置检测模块还可以包括其他任何能够检测转子位置的方法或者硬件设备。
电参量检测模块23，可以实时检测电机11工作过程中的电参量，例如电机的转速。可选的，电参量检测模块23还可以检测电机的输出扭矩，或者基于转速和扭矩检测电机的做功效率。
驱动电路20与电机11的定子绕组A、B、C电性连接，用于将来自电源模块21的电流传递至定子绕组A、B、C以驱动电机11旋转。作为实施例的一种，驱动电路20包括多个开关元件Q1、Q2、Q3、Q4、Q5、Q6。每个开关元件的栅极端与控制器23电性连接，用于接收来自控制器23的控制信号。每个开关元件的漏极或源极与电机11的定子绕组A、B、C连接。开关元件Q1-Q6接收来自控制器23的控制信号改变各自的导通状态，从而改变电源模块21加载在电机11的定子绕组A、B、C上的电流。在一个实施例中，驱动电路20可以是包括六个可控半导体功率器件(例如FET，BJT，IGBT等)的三相桥驱动器电路。可以理解的是，上述开关元件也可以是任何其他类型的固态开关，例如绝缘栅双极型晶体管(IGBT)，双极结型晶体管(BJT)等。
为了使电机11转动，驱动电路20具有多个驱动状态，控制器24可以通过转子的位置信息输出相应的PWM驱动信号控制驱动电路20中的开关元件使驱动电路切换导通状态，进而改变电机定子绕组的导通相以及导通绕组中电流的大小和方向。需要说明的是，定子绕组导通相不同、绕组中的通电电流大小和方向发生变化，将导致定子磁势的大小和方向发生变化。
如图3示出了三相无感BLDC的三相绕组中两相导通即两两导通换相过程中磁势的变化，其中的磁势包括电机转子磁势
Figure PCTCN2021131633-appb-000001
和定子绕组的定子磁势
Figure PCTCN2021131633-appb-000002
转子每转过60度电角度，电机执行一次换相，即每相绕组占有60°的相带，转子在六个不同的相带对应不同的位置信息，控制器24输出的PWM驱动信号可以对应六种不同的信号组合。在一个实施例中，采用信号0代表绕组截止的状态，采用信号1代表绕组导通的状态。另外，图3中虚线表示三相绕组的霍尔位置分别与转子方向平行时形成的霍尔标尺，在该霍尔标尺下，随着转子位置的变化可以确定定子绕组的霍尔位置。具体的，三相绕组的霍尔位置、控制器输出的PWM信号组合形式及相应定子绕组的导通状态如表1所示：
表1
霍尔位置 PWM信号组合 定子绕组导通状态
(0，1，0) (1，0，X) A+B-
(0，1，1) (1，X，0) A+C-
(0，0，1) (X，1，0) B+C-
(1，0，1) (0，1，X) B+A-
(1，0，0) (0，X，1) C+A-
(1，1，0) (X，0，1) C+B-
表1中霍尔位置下列的0表示对应绕组的霍尔位置落在转子的S级处，霍尔位置下列的1表示对应绕组的霍尔位置落在转子的N级处。表1中PWM信号组合下列的0表示对应绕组的下管导通，PWM信号组合下列的1表示对应绕组的上管导通，PWM信号组合下列的X表示对应绕组的上下管均不导通。
由图3可知，在360°的电角度区间内，在转子转动的过程中转子磁势
Figure PCTCN2021131633-appb-000003
的方向不断变化，
Figure PCTCN2021131633-appb-000004
的大小不变；而定子磁势
Figure PCTCN2021131633-appb-000005
由导通的两相定子绕组的磁势合成，其方向随着定子绕组的换相而变化，其大小也与导通相绕组的导通方向及导通电流相关。例如，图3中控制器输出的PWM信号是(1，0，X)时，转子在30°～90°的相带内转动，A、B绕组以A+B-的方式导通，转子磁势
Figure PCTCN2021131633-appb-000006
在平行于转子的方向上，定子磁势
Figure PCTCN2021131633-appb-000007
由A、B相绕组的磁势合成即
Figure PCTCN2021131633-appb-000008
转子每转过60电角度发生一次换相，转子按照表1所示的驱动信号发生换相的过程对应图3中箭头所指的换相过程，相应的转子磁势和定子磁势也如图3所示发生变化。
如图4示出了三相无感BLDC，三相绕组均导通即三三导通时磁势的变化过程。表2为三相绕组均导通方式下霍尔位置、PWM信号与电机定子绕组的导通状态的对应关系：
表2
霍尔位置 PWM信号组合 定子绕组导通状态
(0，1，0) (1，0，0) A+B-C-
(0，1，1) (1，1，0) A+B+C-
(0，0，1) (0，1，0) B+C-A-
(1，0，1) (0，1，1) B+C+A-
(1，0，0) (0，0，1) C+A-B-
(1，1，0) (1，0，1) C+A+B-
由图4可知，在360°的电角度区间内，在转子转动的过程中转子磁势
Figure PCTCN2021131633-appb-000009
的方向不断变化，
Figure PCTCN2021131633-appb-000010
的大小不变；而定子磁势
Figure PCTCN2021131633-appb-000011
由导通的三相定子绕组的磁势合成，其方向随着定子绕组的换相而变化，其大小也与三相绕组的导通方向上及导通电流相关。例如，图4中控制器输出的PWM信号是(1，0，0)时，转子在30°～90°的相待内转动，A、B、C绕组以A+B-C-的方式导通，转子磁势
Figure PCTCN2021131633-appb-000012
在平行于转子的方向上，定子磁势
Figure PCTCN2021131633-appb-000013
由A、B、C相绕组的磁势合成即
Figure PCTCN2021131633-appb-000014
转子每转过60电角度发生一次换相，转子按照表2所示的驱动信号发生换相的过程对应图4中箭头所指的换相过程，相应的转子磁势和定子磁势也如图4所示发生变化。
由图3和图4对比可知，电机定子绕组的导通方式影响定子磁势的大小，单位电流下三相绕组均导通时的定子磁势大于绕组两两导通时的定子磁势。因此在选定相带内为获得较大的定子磁势，控制器24可以改变PWM信号控制定子绕组以两两导通和三三导通的组合导通方式工作。具体的，如图5所示，在60°的相带内，可以控制电机的定子绕组以三三导通方式导通β°的电角度，以两两导通方式导通60-β°的电角度，定义β为扩展角。在一个实施例中，选定相带内两两导通的过程可以连续也可以间断。所谓的选定相带，可以是任意大小的被选定的相带，本申请实施例中对被选定的相带的大小不做限定。
在一个实施例中，定子磁势和转子磁势按照一定的合成方式可以获得电机的合成磁势。示例性的，如图6所示，将转子所在位置的第一方向定义为直轴，垂直于直轴的第二方向定义为交轴。定子磁势在直轴和交轴上的分量
Figure PCTCN2021131633-appb-000015
和
Figure PCTCN2021131633-appb-000016
与转子磁势合成后可以形成直轴方向上的第一合成磁势和交轴方向上的第二合成磁势。需要说明的是，图6所示的转子磁势和定子磁势之间的夹角θ的大小能够表征电机当前的励磁能力。例如，在转子磁势和定子磁势之间的夹角θ为钝角时，电机具有弱磁能力，θ为锐角时，电机具有强磁能力。在一个实施例中，夹角θ为钝角。
在本申请中，第一合成磁势是直轴上
Figure PCTCN2021131633-appb-000017
和
Figure PCTCN2021131633-appb-000018
的合成，只要合成后的磁势相较于原来的
Figure PCTCN2021131633-appb-000019
大小变小即表示电机的弱磁能力得到增强，因此第一合成磁势的 大小表征了电机的弱磁能力，通过调整第一合成磁势可以调整电机的转速；第二合成磁势即定子磁势在交轴上的分量
Figure PCTCN2021131633-appb-000020
基于图6所示的定子磁势与交轴的夹角为θ，由于电机的电磁扭矩
Figure PCTCN2021131633-appb-000021
其中K为固定值，W表示磁余能，而
Figure PCTCN2021131633-appb-000022
从而电磁扭矩
Figure PCTCN2021131633-appb-000023
即电磁扭矩与定子磁势在交轴上的分量相关，因此第二合成磁势的大小表征了电机的做功能力。通过调整第二合成磁势的大小可以达到调整电磁扭矩进而影响电机做功能力的目的。需要说明的是，由图6所示的合成磁势分解图可知，可以在固定第一合成磁势不变的前提下，通过调整定子磁势使第二合成磁势达到预期值。也就是说，本申请在提高电机转速的前提下可以保证电机的做功能力即保证电机的出功效率。
在本申请中，电机的出功效率为电机功率输出的效率，能代表电机的做功能力。
同样的，由图6可知，转子位置与转子磁势具有对应关系，在转子位置确定时，通过调整定子磁势可达到调整二者的合成磁势的目的，从而控制电机输出的电参量。
在一个实施例中，如图7所示，为获得更高的弱磁能力，可以设置超前导通电角度α。也就是说，无论是两两导通方式下还是三三导通方式下，绕组均具有超前导通角α。
参考图8所示的电机的弱磁能力和做功能力的对比图，横轴为扩展角，图8a的纵轴表示电机做功能力，图8b的纵轴表示电机的励磁能力，励磁能力包括强磁能力和弱磁能力。图8a中线1表示无超前角、绕组两两导通时电机的做功能力，即超前角为0，扩展角也为0时电机的做功能力；线2表示无超前角、绕组两两导通和三三导通组合时电机的做功能力，即超前角为0，扩展角不为0时电机的做功能力；线3表示有超前角、绕组两两导通和三三导通组合时电机的做功能力，即超前角不为0，扩展角也不为0时电机的做功能力。图8b中线1表示无超前角、绕组两两导通时电机的励磁能力，即超前角为0，扩展角也为0时电机的励磁能力；线2表示无超前角、绕组两两导通和三三导通组合时电机的励磁能力，即超前角为0，扩展角不为0时电机的励磁能力；线3表示有超前角、绕组两两导通和三三导通组合时电机的励磁能力，即超前角不为0，扩展角也不为0时电机的励磁能力。其中在励磁为正时表示强磁能力，励磁为负时表示弱磁能力。由图8a可知，设置一定的扩展角可以增加电机的做功能力。扩展角β的范围为0～π/3。而在设置扩展角的基础上行设置超前角α会在一定程度上降低电机的做功能力，然而即使在π/3处，线1和线3之间的差值也小于0.2，也就是说增加超前角在一定程度上对电机的做功能力影响不大。由图8b可知，设置扩展角β可以增加电机的弱磁能力，在此基础上增加超前角α将大幅提升 电机的弱磁能力。综上可知，采用合适的扩展角可以取得电机弱磁能力和做功能力的平衡，能够在保证做功能力的前提下，提升电机转速。
具体实现中，控制器24能够获取转子位置信息，由于转子位置不同定子绕组的导通方式也不同，在绕组的不同导通方式下定子磁势不同。因此控制器24可根据转子位置信息控制绕组导通状态的改变进而调整定子磁势，进而能根据转子磁势和调整后的定子磁势的确定电机的合成磁势，且在该合成磁势下电机输出的电参量是处于预设参量范围内的。也就是说，通过调整电机的合成磁势可以使电机满足一定的转动特性。在一个实施例中，电机的电参量可以是电机转速，或者基于转速和扭矩确定的出功效率。上述过程可以理解为：控制器可以根据转子位置信息调整电子绕组的导通方式，以使电机的转速能够达到一定的速度或者使电机转速提高到一定范围，同时保证电机具有较好的出功效率。其中绕组的导通方式包括两两导通和/或三三导通和/或两两导通与三三导通的组合以及不同导通方式下的扩展角度和/或超前角度。
由图3和图4可知，单位电流下三相电机中任意两相定子绕组导通时定子磁势小于三相绕组均导通时的定子磁势。因此，在转子处于第一预设位置时，控制器24可以通过控制电机的三相定子绕组均导通接入电源模块的方式来增加定子磁势；在转子处于第二预设位置时，控制器24可以通过控制电机的任意两项定子绕组导通接入电源模块的方式来降低定子磁势。其中，增加定子磁势可以是保持当前定子磁势方向不变，增加定子磁势的大小，也可以是改变定子磁势的方向同时增加其大小。降低定子磁势，也可以是保持当前定子磁势方向不变，将定子磁势降低为零或者降低至一定值，或者改变定子方向同时将定子磁势降低为零或者降低至一定值。
在一个实施例中，转子处于第一预设位置时，控制器可以控制定子绕组由两两导通方式切换至三三导通方式，转子处于第二预设位置时控制定子绕组由三三导通方式切换至两两导通方式。可以理解的是，在选定相带内，可以多次切换两两导通方式或者三三导通方式，因此上述第一预设位置和第二预设位置并不是一个固定的转子位置，而是在转子转动过程中电机的合成磁势变化导致电参量超过预设范围时转子所处的位置。具体实现中，控制器通过转子位置检测模块22识别当前的转子位置并判断当前位置是否为第一预设位置或第二预设位置。
也就是说，在选定的相带内，通过检测转子位置信息调整定子绕组的导通数量可以实现定子磁势的调整，进而影响合成磁势即影响第一合成磁势和第二合成磁势，以达到对电机做功能力影响较小的前提下，提升电机转速。
由上述实施例可知，选定相带内三相无感BLDC定子绕组的导通方式可以 根据转子位置信息进行切换，例如，在两相绕组导通的第一导通方式和三相绕组均导通的第二导通方式之间切换。在本实施例中，定义在第一导通方式即两两导通方时下两相定子绕组导通第一电角度，在第二导通方式即三三导通方式下三相定子绕组导通第二电角度，则电机在第一导通方式下导通第一电角度具有第一电磁扭矩，在第二导通方式下导通第二电角度具有第二电磁扭矩。所谓的电磁扭矩也就是电机的输出扭矩，能够表征电机的做功能力。
由于电机本身具有影响电机做功能力的磁阻扭矩，因此磁阻扭矩和不同导通方式下的电磁扭矩共同组成电机的总扭矩，总扭矩可以准确反映电机的做功能力。可以理解的是，电机在单位电流下的总扭矩越大工具越省电，因此在保证电机做功能力、提升电机转速的前提下还可以进一步降低能耗。
参考图9所示的电动工具的电路框图，还包括扭矩检测模块25，用于检测定子绕组不同导通方式下电机的输出扭矩，例如，可以检测电机以第一导通方式导通第一电角度时的第一电磁扭矩，以及电机以第二导通当时导通第二电角度时的第二电磁扭矩。可以理解的是，扭矩检测模块25还可以检测电机的磁阻扭矩，其中磁阻扭矩是电机中转子的直轴和交轴的磁阻不同引起的。
参考图10和图11所示的电磁扭矩示意图，横轴表示转子转动的角度，纵轴表示扭矩的大小，线1为第一导通方式下电机的总扭矩，线2为第二导通方式下电机的总扭矩，线3为第一导通方式下电机的第一电磁扭矩，线4为第二导通方式下电机的第二电磁扭矩，线5为电机的磁阻扭矩。由图10可知，电机的磁阻扭矩为类正弦波形，也就是说，在一定电角度内磁阻扭矩可以增加电机的总扭矩，在一定电角度内可以将降低电机的总扭矩，因此图10中阴影区域表示电机具有最大总扭矩时转子转动角度的区间范围，该区间的范围是90°～135°。也就是说，电机具有最大总扭矩的定义域是90°～135°。进一步的，如图11所示的两个阴影区间分别表示单位电流下采用第一导通方式时的第一总扭矩和采用第二导通方式时的第二总扭矩，二者之和为最终要求的电机的总扭矩。也就是说，图11所示的两处阴影区域的面积之和最大时对应单位电流下电机的最大总扭矩。
基于此，控制器24可以根据电机转子的位置调整第一导通方式下导通的第一电角度和第二导通方式下导通的第二电角度，以使电机在选定相带内单位电流下的总扭矩处于预设扭矩范围内。可以理解的是，不同工具的能耗不同，预设扭矩也不同，本申请中预设扭矩范围可以涵盖不同工具不同能耗要求所对应的电机的总扭矩值。
可以理解的是，上述调整定子绕组不同导通方式下导通电角度调整的过程也是影响定子磁势的过程，因此在调整总扭矩降低电机能耗的过程中，对电机 的做功能力和转速的提升影响较小。
在一个实施例中，选定相带内的第一电角度和第二电角度的比值可以根据预设扭矩范围通过查表的方式获得。
针对不同的工具，及不同工具具体的使用工况，可以通过控制电机定子绕组的导通方式保证电动工具在不同工况下均具有稳定的输出性能，同时具备较大的输出功率。
一般工具的运行阶段可分为高速运行阶段和低速运行阶段，其中不同工具在不同工况下的高速运行阶段电机的最低转速不同，不同工具在不同工况下的低速运行阶段电机的最高转速也不同。在一个实施例中，定义高度运行阶段为工具工作的第一工作阶段，低速运行阶段为工具工作的第二工作阶段。一般，在第一工作阶段，希望电机尽量维持不变的转速持续工作一段时间，并且电机的工作参数超负荷之前转入第二工作阶段。在本申请中，电机采用两两导通和三三导通切换的的导通方式控制电机运转，因此为获得第一工作阶段中基本稳定的转速，控制器在第一工作阶段中调整电机以第二导通方式即三三导通方式导通工作的第二电角度β，以使电机的转速维持基本稳定状态；进一步的，在第二工作阶段中，可以控制定子绕组在三三导通方式下以第一预设电角度导通，也就是以一个固定的电角度导通。特别的，在第一工作阶段和第二工作阶段中电机是在两两导通和三三导通方式间切换的，即在两个工作阶段中电机均存在两两导通和三三导通两种导通工作方式，且两个工作阶段中两两导通的电角度均是固定值，例如是第二预设电角度。因此本申请并未对电机在两个工作阶段中两两导通方式的电角度进行说明。也就是说，工具在高速运行阶段三三导通的电角度不断变化，在低速运行阶段三三导通的电角度固定不变，且两个运行阶段中绕组两两导通的电角度均是固定值。在本实施例中，对第一预设电角度和第二预设电角度的大小不做具体限定。
在一个实施例中，控制器24通过调整电机定子绕组在第二导通方式即三三导通下的电角度(扩展角β)，同时保持定子绕组以固定的超前角α导通工作，可使电机的转速基本维持不变。例如，在第一工作阶段定子绕组具有15°的超前角，三三导通的扩展角从0°变化到45°，则电机的转速可以维持在相对稳定的状态。
如图12所示，横轴表示电机的输出扭矩T，纵轴表示电机的转速n，在第一工作阶段中，电机转速和输出扭矩基本保持不变，线1基本平行于横坐标轴。然而，在第一工作阶段内电机的电流上升速率较快电机在短时间内将承受较大的电流，因此第一工作阶段的维持时长不宜过长。在一种实现方式中，在电机处于第一工作阶段中，控制器24可以通过停止对第一导通方式下电角度的调整， 使电机的定子绕组以第三预设电角度导通工作，同时继续保持不变的超前角α，来降低电机的转速，并降低电机工作电流的变化斜率，使电机进入第二工作阶段。其中，第三预设电角度是一个固定的电角度，本申请对其大小不做具体限定。可以理解的是，如果电机一直维持较高的转速，将导致发热严重，因此在需要降速时，控制器可以控制电机进入第二工作阶段。
在一个实施例中，控制器可以在第二导通方式的导通角达到角度阈值时，控制电机进入第二工作阶段。例如，在第一工作阶段扩展角从0°变化到45°时，控制器24不再调整扩展角，使电机绕组以15°的超前角和固定的小于或等于45°的扩展角导通进入第二工作阶段。
在一个实施例中，如图13所示，电动工具还包括电流检测模块26用于检测电机的工作电流。控制器24获取电机的工作电流后可以计算电流的变化斜率。进一步的，控制器可以根据第一工作阶段电机电流的变化斜率控制电机切换至第二工作阶段，即控制电机定子绕组第二导通方式导通的电角度为第一预设电角度。也就是说，在第二工作阶段内，电机定子绕组的超前角α和三三导通时的扩展角β均为固定值。在本申请中，定义电机工作电流在第一工作阶段具有第一变化斜率，在第二工作阶段具有第二变化斜率，如图14所示，横轴表示电机输出扭矩，纵轴表示电机工作电流，由图14可知第二工作阶段的电机电流的第二变化斜率明显小于第一工作阶段中的第一变化斜率。结合图12和图14可知，在第二工作阶段中，电流变化斜率变小，但工作电流值并没有下降，电机转速下降。
具体实现中，控制器24在电机的第一工作阶段检测到电机工作电流在第一变化斜率下达到电流阈值时，可以控制电机切换至第二工作阶段，即不再调整扩展角β。可以理解的是，在第一工作阶段中电机的工作电流达到第一变化斜率下的电流阈值时，电机绕组三三都通的扩展角β为其在第二导通方式下能够达到的最大电角度。在第二工作阶段中，三三导通的固定第二电角度小于或等于上述最大电角度。例如，在第一工作阶段三三导通的扩展角从0°调整至20°时，电机工作电流在第一工作阶段下达到了电流阈值，则控制器控制电机以15°的超前角和固定的小于等于20°的扩展角导通进入第二工作阶段。也就是说，在第一工作阶段的第一电流斜率下电机工作电流达到电流阈值，第二导通方式下的电角度小于角度阈值时，控制器仍控制电机进入第二工作阶段。
通过在第一工作阶段内调整扩展角以维持电机的转速和输出扭矩可以保证电机在启动阶段能在不同的工况下维持稳定的输出性能，通过固定扩展角使电机工作在第二阶段可以避免电流持续快速增加，损坏电机。

Claims (30)

  1. 一种电动工具，包括：
    电机，包括转子和多相定子绕组；
    驱动电路，具有多个开关元件，用于输出开关信号以驱动所述电机转动；
    控制器，至少与所述驱动电路和所述电机构成电性连接；
    所述控制器被配置为：
    获取所述电机的转子位置信息；
    根据所述转子位置信息调整所述电机的合成磁势，以使所述合成磁势对应的所述电机的输出电参量处于预设参数范围内。
  2. 根据权利要求1所述的电动工具，其中，
    所述控制器被配置为：
    基于所述转子位置信息控制所述驱动电路的导通状态以调整所述定子绕组的定子磁势；
    基于所述电机的转子磁势和调整后的定子磁势计算所述电机的合成磁势，以使所述合成磁势对应的所述电机的输出电参量处于预设参数范围内。
  3. 根据权利要求1所述的电动工具，其中，
    还包括：
    转子位置检测模块，用于检测所述电机的转子位置；
    电参量检测模块，与所述电机电性连接，用于检测所述电机输出的电参量。
  4. 根据权利要求3所述的电动工具，其中，
    所述转子位置检测模块包括霍尔传感器。
  5. 根据权利要求3所述的电动工具，其中，
    所述转子位置检测模块被配置为：
    基于所述定子绕组的反电动势估算所述转子位置或者基于所述定子绕组的相电流估算所述转子位置。
  6. 根据权利要求1所述的电动工具，其中，
    所述控制器被配置为：
    在所述转子处于第一预设位置时，控制所述驱动电路改变导通状态以增加所述定子磁势；
    在所述转子处于第二预设位置时，控制所述驱动电路改变导通状态以降低所述定子磁势。
  7. 根据权利要求6所述的电动工具，其中，
    所述控制器被配置为：
    基于所述电机的转子磁势和调整后的定子磁势计算第一方向上的第一合成磁势和第二方向上的第二合成磁势，以使所述第一合成磁势对应的所述电机的转速处于预设转速范围内，并使所述第二合成磁势对应的所述电机的出功效率处于预设效率范围内。
  8. 根据权利要求7所述的电动工具，其中，
    所述第一方向垂直于所述第二方向。
  9. 根据权利要求5所述的电动工具，其中，
    所述电机具有三相定子绕组；
    所述控制器被配置为：
    在所述转子处于第一预设位置时，控制所述驱动电路改变导通状态使所述电机的三相定子绕组均导通接入所述电源模块；
    在所述转子处于第二预设位置时，控制所述驱动电路改变导通状态使所述电机的任意两项定子绕组导通接入所述电源模块。
  10. 一种电动工具的控制方法，
    所述电动工具包括包括：
    电机，包括转子和多个定子相绕组；
    驱动电路，具有多个开关元件，用于输出开关信号以驱动所述电机转动；
    控制器，至少与所述驱动电路和所述电机构成电性连接；
    其中，所述控制方法包括：
    获取所述电机的转子位置信息；
    根据所述转子位置信息调整所述电机的合成磁势，以使所述合成磁势对应的所述电机的输出电参量处于预设参数范围内。
  11. 一种电动工具，包括：
    电机，具有多相绕组，所述电机的各相绕组在选定相带内能够以第一导通方式导通第一电角度，并以第二导通方式导通第二电角度；
    扭矩检测模块，用于检测所述第一导通方式下导通第一电角度时所述电机的第一电磁扭矩，和所述第二导通方式下导通第二电角度时所述电机的第二电磁扭矩；
    控制器，至少与所述扭矩检测模块和所述电机构成电性连接；
    所述控制器被配置为：
    获取所述第一电磁扭矩和所述第二电磁扭矩，并依据所述第一电磁扭矩、所述第二电磁扭矩和所述电机的磁阻扭矩计算所述电机在所述相带内单位电流下的总扭矩；
    调整所述第一电角度和所述第二电角度，以使所述电机在所述选定相带内单位电流下的总扭矩处于预设扭矩范围内。
  12. 根据权利要求11所述的电动工具，其中，
    所述电机的磁阻扭矩为类正弦波。
  13. 根据权利要求11所述的电动工具，其中，
    所述第一导通方式包括电机各相绕组中任意两相绕组导通；
    所述第二导通方式包括电机各相绕组中三相绕组导通。
  14. 根据权利要求11所述的电动工具，其中，
    所述控制器被配置为：
    检测所述电机的转子位置；
    在所述第一导通方式下，所述转子位置达到第一预设位置处时切换至第二导通方式；
    在所述第二导通方式下，所述转子位置达到第二预设位置处时切换至第一导通方式。
  15. 根据权利要求11所述的电动工具，其中，
    在所述选定相带内所述第一电角度和所述第二电角度的比值根据所述预设扭矩范围通过查表的方式获得。
  16. 一种电动工具的控制方法，所述电动工具包括：
    电机，具有多相绕组，所述电机的各相绕组在选定相带内能够以第一导通方式导通第一电角度，并以第二导通方式导通第二电角度；
    扭矩检测模块，用于检测所述第一导通方式下导通第一电角度时所述电机的第一电磁扭矩，和所述第二导通方式下导通第二电角度时所述电机的第二电 磁扭矩；
    控制器，至少与所述扭矩检测模块和所述电机构成电性连接；
    所述控制方法包括：
    获取所述第一电磁扭矩和所述第二电磁扭矩并依据所述第一电磁扭矩、所述第二电磁扭矩和所述电机的磁阻扭矩计算所述电机在所述相带内单位电流下的总扭矩；
    调整所述第一电角度和所述第二电角度，以使所述电机在所述相带内单位电流下的总扭矩处于预设扭矩范围内。
  17. 根据权利要求16所述的方法，其中，
    所述电机的磁阻扭矩为类正弦波。
  18. 根据权利要求16所述的方法，其中，
    所述第一导通方式包括电机各相绕组中任意两相绕组导通；
    所述第二导通方式包括电机各相绕组中三相绕组导通。
  19. 根据权利要16所述的方法，还包括：
    检测所述电机的转子位置；
    在所述第一导通方式下，所述转子位置达到第一预设位置处时切换至第二导通方式；
    在所述第二导通方式下，所述转子位置达到第二预设位置处时切换至第一导通方式。
  20. 根据权利要16所述的方法，其中，
    在所述选定相带内所述第一电角度和所述第二电角度的比值根据所述预设扭矩范围通过查表的方式获得。
  21. 一种电动工具，包括：
    电机，具有多相定子绕组，所述电机的各相绕组在选定相带内能够以第一导通方式和第二导通方式导通工作；
    扭矩检测模块，用于检测所述电机的输出扭矩；
    转速检测模块，用于检测所述电机的转速；
    控制器，至少与所述扭矩检测模块、所述转速检测模块和所述电机构成电性连接；
    所述控制器被配置为：
    获取所述电机的输出扭矩和转速；
    在第一工作阶段中，调整所述电机以所述第二导通方式导通工作的电角度，以使所述电机的转速维持基本稳定状态；
    在所述第二工作阶段中，控制所述定子绕组在所述第二导通方式下以第一预设电角度导通。
  22. 根据权利要求21所述的电动工具，其中，
    所述控制器被配置为：
    在所述第一工作阶段和所述第二工作阶段中控制所述定子绕组在第一导通方式下以第二预设电角度导通。
  23. 根据权利要求21所述的电动工具，其中，
    所述控制器被配置为：
    在所述第一工作阶段中，所述电机以所述第二导通方式导通工作的电角度达到预设角度阈值时，控制所述定子绕组在所述第二导通方式下以第三预设电角度导通。
  24. 根据权利要求21所述的电动工具，还包括：
    电流检测模块，用以检测所述电机的工作电流；
    所述控制器被配置为：
    获取所述电机的工作电流，并计算所述工作电流的变化斜率；
    在所述第一工作阶段中所述电机的工作电流达到第一变化斜率下的电流阈值时，控制所述定子绕组以所述第一预设电角度导通使所述电机进入所述第二工作阶段。
  25. 根据权利要求24所述的电动工具，其中，
    在所述第一工作阶段内所述电机的输出电流具有所述第一变化斜率，在所述第二工作阶段内所述电机的输出电流具有第二变化斜率；
    所述第一变化斜率大于所述第二变化斜率。
  26. 根据权利要求23所述的电动工具，其中，
    在所述第一工作阶段中所述电机的工作电流达到第一变化斜率下的电流阈值时，所述定子绕组以所述第二导通方式导通的电角度为所述第二导通方式下能够达到的最大电角度。
  27. 根据权利要求26所述的电动工具，其中，
    所述第一预设电角度小于或等于所述定子绕组在所述第一工作阶段中以所述第二导通方式导通的最大电角度。
  28. 根据权利要求21所述的电动工具，其中，
    所述第一导通方式包括电机各相绕组中任意两相绕组导通；
    所述第二导通方式包括电机各相绕组中三相绕组导通。
  29. 一种电动工具的控制方法，所述电动工具包括：
    电机，具有多相定子绕组，所述电机的各相绕组在选定相带内能够以第一导通方式和第二导通方式导通工作；
    扭矩检测模块，用于检测所述电机的输出扭矩；
    转速检测模块，用于检测所述电机的转速；
    控制器，至少与所述扭矩检测模块、所述转速检测模块和所述电机构成电性连接；
    所述控制方法包括：
    获取所述电机的输出扭矩和转速；
    在第一工作阶段中，调整所述电机以所述第二导通方式导通工作的电角度，以使所述电机的转速维持基本稳定状态；
    在所述第二工作阶段中，控制所述定子绕组在所述第二导通方式下以第一预设电角度导通。
  30. 根据权利要求29所述的方法，还包括：
    在所述第一工作阶段和所述第二工作阶段中控制所述定子绕组在第一导通方式下以第二预设电角度导通。
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