CN111756285B

CN111756285B - Electric tool

Info

Publication number: CN111756285B
Application number: CN201910702941.2A
Authority: CN
Inventors: 许彦卿; 杨德中; 王宏伟
Original assignee: Nanjing Chervon Industry Co Ltd
Current assignee: Nanjing Chervon Industry Co Ltd
Priority date: 2019-03-28
Filing date: 2019-07-31
Publication date: 2024-06-18
Anticipated expiration: 2039-07-31
Also published as: CN111756307A; CN111835249A; CN111769769A; CN111835248A; CN111756285A; CN111835249B; CN116722771A; CN116111910A

Abstract

The invention discloses an electric tool, comprising: the motor comprises a stator and a rotor, and the motor is capable of generating reluctance torque; a power supply device for supplying electric power to the motor; the driving circuit is electrically connected with the motor to drive the motor; the parameter acquisition module is used for acquiring the current of the motor, the rotating speed of the motor and the position of the rotor; a controller configured to: and dynamically adjusting the current loaded to the stator according to at least one of the current of the motor, the rotating speed of the motor and the position of the rotor so as to enable the value range of the included angle between the stator flux linkage and the rotor flux linkage to be 90-135 degrees or 135-180 degrees. The motor of the electric tool has higher output rotating speed and better output performance.

Description

Electric tool

Technical Field

The invention relates to an electric tool, in particular to an electric tool with higher motor output rotating speed.

Background

Existing power tools typically employ a conventional square wave to drive their internal motor, which is controlled in terms of motor speed and torque by adjusting the duty cycle of the square wave signal.

For a brushless dc motor, in a conventional square wave control method, in order to rotate the brushless dc motor, a driving circuit has a plurality of driving states, a stator winding of the brushless dc motor generates a magnetic field in one driving state, and a controller is configured to output a corresponding driving signal to the driving circuit according to a rotation position of a rotor so as to enable the driving circuit to switch the driving state, thereby changing a state of a voltage applied to the winding of the brushless dc motor, generating an alternating magnetic field to drive the rotor to rotate, and further realizing driving of the brushless dc motor.

In the conventional square wave modulation control method for a brushless motor, in one electrical cycle, the brushless motor has only six states, or stator current has six states (three-phase bridge arm has six switching states). Each current state can be regarded as a vector moment in one direction, six vectors are regularly converted step by step, so that the rotor is driven to rotate, and the motor rotor can synchronously rotate.

The traditional square wave control implementation mode is simple and convenient, but the motor efficiency is low and the whole machine efficiency is low due to the fact that the square wave control implementation mode only has six discrete and discontinuous vector moments, and under the heavy load condition, the locked-rotor condition can occur frequently.

In addition, the conventional square wave control method is difficult to further raise after the motor speed reaches a certain speed, and in the light load condition, the speed is generally desired to be as high as possible. Therefore, the common practice is to implement speed regulation by configuring different gear ratios by means of a mechanical structure, but the speed regulation range is limited by a motor greatly by means of the mechanical structure, and the mechanical gear structure also increases the weight of the whole machine to affect the use.

Disclosure of Invention

In order to solve the defects in the prior art, the invention aims to provide an electric tool with higher output rotating speed and better output performance.

The technical scheme of the invention is as follows: a power tool, comprising: the motor comprises a stator and a rotor, and the motor is capable of generating reluctance torque; a power supply device for supplying electric power to the motor;

The driving circuit is electrically connected with the motor to drive the motor; a controller for controlling the driving circuit, the controller configured to perform the following operations: in a first load interval, controlling the driving circuit in a first characteristic control mode to enable the motor to rotate in a first rotation speed range; in a second load interval, controlling the driving circuit in a second characteristic control mode to enable the motor to rotate in a second rotating speed range; the first characteristic control mode includes: dynamically adjusting the current loaded to the stator according to at least one of the current of the motor, the rotating speed of the motor and the position of the rotor of the motor so as to enable the value range of the included angle between the stator flux linkage and the rotor flux linkage to be 135-180 degrees; the second characteristic control mode includes: and dynamically adjusting the current loaded to the stator according to at least one of the current of the motor, the rotating speed of the motor and the position of the rotor of the motor so as to enable the value range of the included angle between the stator flux linkage and the rotor flux linkage to be 90-135 degrees.

Optionally, in the second characteristic control mode, the torque of the output torque of the motor in a preset time range is greater than a preset threshold, and the preset threshold is set according to the characteristic of the motor and the current of the motor.

Optionally, the load torque of the motor of the first load interval is smaller than the load torque of the motor of the second load interval.

Optionally, when the controller controls the driving circuit in the first characteristic control manner, the motor outputs a first rotation speed; the controller outputs a second rotating speed when controlling the driving circuit in the second characteristic control mode; the motor outputs a third rotating speed when the controller controls the driving circuit in a third control mode; wherein the first rotational speed is greater than the third rotational speed, and the second rotational speed is greater than the third rotational speed.

Optionally, the bus current of the motor increases with a first slope in a first torque interval and increases with a second slope in a second torque interval, wherein the first slope is greater than the second slope.

Optionally, the controller controls the driving circuit in a second characteristic control manner to enable the motor to rotate with a preset torque, and the output current of the power supply device is a second output current; when the controller controls the driving circuit in a third control mode to enable the motor to rotate with the preset torque, the output current of the power supply device is a third output current; wherein the second output current is less than the third output current.

Optionally, when the controller controls the driving circuit in the first characteristic control manner, the output power of the electric tool is a first output power; when the controller controls the driving circuit in the second characteristic control mode, the output power of the electric tool is second output power; assuming that the controller controls the driving circuit in a third control mode, the output power of the electric tool is a third output power; wherein the first output power is greater than the third output power and the second output power is greater than the third output power.

Optionally, the controller outputs a PWM signal to the driving circuit, a duty ratio of the PWM signal varying following a change in a position of the rotor.

Optionally, the controller controls the driving circuit to make the input voltage of the motor approximately sine-wave-shaped.

Optionally, the motor is a three-phase motor, and three-phase input voltages of the motor are 120 ° phase angle to each other.

Optionally, the controller includes: and the first rotating speed ring is used for generating a target current of the motor according to the target rotating speed of the motor and the actual rotating speed of the motor.

Optionally, the controller further comprises: the first current distribution unit is used for distributing a direct-axis target current and a quadrature-axis target current according to the target current of the motor generated by the first rotating speed ring; a first current conversion unit for generating a direct-axis actual current and a quadrature-axis actual current according to an actual current of the motor and a position of a rotor of the motor; the first current loop is used for generating a first voltage regulating quantity according to the direct-axis target current and the direct-axis actual current; the second current loop is used for generating a second voltage regulating quantity according to the quadrature target current and the quadrature actual current; a first voltage conversion unit configured to generate a first voltage control amount and a second voltage control amount according to the first voltage adjustment amount and the second voltage adjustment amount; and the first control signal generation unit is used for generating a control signal according to the first voltage control quantity and the second voltage control quantity, and the control signal is used for controlling the driving circuit.

Optionally, the controller includes: and the second rotating speed ring is used for generating target torque of the motor according to the target rotating speed and the actual rotating speed of the motor.

Optionally, the controller further comprises: a torque ring for generating a third voltage adjustment amount according to a target torque and an actual torque of the motor; the magnetic chain ring is used for generating a fourth voltage adjustment quantity according to the target stator flux linkage and the actual stator flux linkage of the motor; a second voltage conversion unit configured to generate a third voltage control amount and a fourth voltage control amount according to the third voltage adjustment amount and the fourth voltage adjustment amount; and a second control signal generating unit for generating a control signal for controlling the driving circuit according to the third voltage control amount and the fourth voltage control amount.

Optionally, the power tool further includes: and the speed regulating mechanism is at least used for setting the target rotating speed of the motor.

The invention has the advantages that: the motor output rotating speed of the electric tool is higher, and the motor output performance is better.

Drawings

Fig. 1 is an external view of an electric drill;

figure 2 is a block diagram of the circuitry of an electric drill of one embodiment;

fig. 3 is a block diagram of the circuitry of another embodiment of the drill;

Fig. 4 is circuitry as a more specific exemplary power drill;

FIG. 5 is a stator and rotor of an electric machine of an embodiment;

fig. 6 is a torque angle characteristic curve of permanent magnet torque T1, reluctance torque T2, and electromagnetic torque Te of the motor;

FIG. 7 is a space vector diagram of the current in the stator flux, rotor flux, and d-q coordinate system of the motor;

FIG. 8 is a graph of motor bus current versus motor torque for an electric drill;

fig. 9 is a graph of motor speed versus motor torque for an electric drill;

fig. 10 is a graph of motor efficiency versus motor torque for an electric drill;

fig. 11 is a graph of output power versus motor torque for an electric drill;

FIG. 12 is an external view of the angle grinder;

FIG. 13 is a partial structural cross-sectional view of the angle grinder of FIG. 12;

FIG. 14 is circuitry for an exemplary angle grinder;

FIG. 15 is a space vector diagram of the current in the stator flux, rotor flux, and d-q coordinate system of the motor;

FIG. 16 is a graph of motor speed versus motor torque for an angle grinder;

fig. 17 is a torque angle relationship curve of the permanent magnet torque T1, the reluctance torque T2, and the electromagnetic torque Te of the motor;

FIG. 18 is a graph of motor efficiency versus motor torque for an angle grinder;

FIG. 19 is a graph of motor bus current versus motor torque for an angle mill;

FIG. 20 is a graph of output power versus motor torque for an angle grinder.

Detailed Description

The invention is described in detail below with reference to the drawings and the specific embodiments.

The power tool of the present invention may be a hand-held power tool, garden-type vehicle such as a vehicular mower, without limitation. The power tool of the present invention includes, but is not limited to, the following: electric tools requiring speed regulation such as screw driver, electric drill, wrench, angle grinder, etc., electric tools which may be used for polishing workpieces such as sander, etc., and reciprocating saw, circular saw, curved saw, etc., may be used for cutting workpieces; electric hammers and the like may be used as power tools for impact use. These tools may also be garden-type tools, such as pruners, chain saws, vehicular mowers; in addition, these tools may also be used for other purposes, such as blenders. It is within the scope of the present invention to provide such power tools that employ the following disclosed embodiments.

Referring to fig. 1, a power tool 10, which is an electric drill, is illustratively shown. The power tool 10 mainly includes: a housing 11, a functional element 12, a grip portion 13, a speed regulating mechanism 14, a motor 15, and a power supply device 16. Of course, the drill also includes a drive mechanism, drill bit, circuit board, etc. (not exposed in the view of fig. 1).

The housing 11 is formed with a grip portion 13, and the grip portion 13 is gripped by a user, and of course, the grip portion 13 may be a separate component. The housing 11 constitutes a main body portion of the power tool 10 for accommodating a motor 15, a transmission mechanism, and other electronic components such as a circuit board. The front end of the housing 11 is used for mounting a functional element.

The functional element 12 is used to perform the function of the power tool 10, and is driven to operate by a motor 15. The functional elements are different for different power tools. For a drill, the function 12 is a drill bit (not shown) for performing a drilling function. The drill bit is operatively connected to the motor 15, and in particular, the drill bit is electrically connected to the motor 15 via an output shaft and a transmission mechanism.

The power supply device 16 is used to provide power to the power tool 10. In this embodiment, the power tool 10 is powered by a battery pack 16. Alternatively, the power tool 10 further includes a battery pack coupling 17 for connecting the battery pack 16 to the power drill.

The speed regulating mechanism 14 is at least used for setting a target rotation speed of the motor 15, that is, the speed regulating mechanism 14 is used for realizing speed regulation of the motor 15, and the speed regulating mechanism 14 can be, but is not limited to, a trigger, a knob and the like. In the present embodiment, the speed regulating mechanism 14 is configured as a trigger structure. The foregoing is merely illustrative, and not limiting, and in other embodiments, the power device 16 may be an ac power source, and in other embodiments, the power tool 10 may be powered by an ac power source, where the ac power source may be 120V or 220V ac mains, and the power device 16 includes a power conversion unit connected to the ac power for converting the ac power into electrical energy for use by the power tool 10.

In another embodiment of the present invention, a hand-held power tool includes a motor having a stator and a rotor; a motor drive shaft or output shaft driven by the motor rotor; a tool attachment shaft for supporting a tool attachment; and the transmission device is used for connecting the motor output shaft to the tool accessory shaft and transmitting the torque output by the motor to the tool accessory. Wherein the motor output shaft may be coaxial, generally parallel, generally perpendicular or inclined to the tool attachment shaft, without limitation.

In yet another embodiment of the present invention, a garden tool, such as a vehicular mower, includes a body, at least one drive wheel or set of drive wheels supported by the body; a drive device, such as a motor, for providing torque to the at least one drive wheel or set of drive wheels; and circuitry to control motor drive operation, as described below.

Referring to fig. 2, the circuit system 20 of the electric power tool 10 according to one embodiment includes a power supply 21, a power supply circuit 22, a controller 23, a driving circuit 24, a parameter acquisition module 25, a rotation speed detection module 26, and a motor 27.

The power supply device 21 is used to power the power tool 10, and in some embodiments, the power supply device 21 outputs direct current, more specifically, the power supply device 21 includes a battery pack. In other embodiments, the power supply device 21 outputs ac power, which may be 120V or 220V ac mains, and the ac power is converted into electric energy for use by the electric tool by rectifying, filtering, voltage dividing, voltage reducing, etc. the ac signal output by the ac power through the hardware circuit. Alternatively, the power tool 10 is powered using a battery pack, and the power supply device 21 includes the battery pack.

The power supply circuit 22 is electrically connected to the power supply device 21 for converting electric energy from the power supply device 21 into electric energy suitable for use by the power tool, and is electrically connected to the controller 23, at least for supplying power to the controller 23.

The current detection module 25 is connected to the motor 27 and is used for collecting the current of the motor 27, wherein the current can be the bus current of the motor 27 or the phase current of the motor 27, and as an embodiment, the current detection module 25 detects each phase current of the motor 27, and the bus of the motor 27 can be directly obtained by calculation from the detected three-phase current.

In a preferred embodiment of the present invention, the parameter acquisition module 25 is configured to acquire at least one of a current of the motor 27, a rotational speed of the motor 27, and a position of a rotor. In the embodiment of fig. 2, the parameter acquisition module 25 comprises a current detection module 251 and a position and speed detection module 252, wherein the current detection module 251 is configured to detect a current of the motor, the current comprising a phase current, and the current detection module 251 is further configured to detect a bus current of the motor 27; the speed and position detection module 252 includes a sensor associated with the motor 27 that directly detects the speed and position of the motor 27, the speed and position detection module 252 being, for example, a hall sensor.

In the embodiment of fig. 2, the speed and position detection module 252 directly detects the speed and position of the motor 27. In yet another embodiment, referring to FIG. 3, the parameter detection module 36 employs a position and speed estimation module 362 to estimate the rotational speed of the motor 37 and the position of the rotor of the motor from the detected current of the motor 37, such as a state observer detection method. In other embodiments of the present invention, the parameter obtaining module 25 may be configured to obtain the current of the motor and the rotational speed of the motor; the position of the rotor of the motor may be estimated by analysis of the current and/or voltage of the motor, or by other parametric characteristics of the components associated with the motor. In still other embodiments of the present invention, the parameter acquisition module 25 may acquire only the current of the motor, and the motor rotation speed may be indirectly acquired through the current and/or the voltage of the motor; the position of the rotor of the motor may be obtained by analyzing and estimating the current and/or voltage of the motor, or may be obtained by other parameter characteristics of elements associated with the motor, but is not limited thereto. That is, the parameter detection module 25 obtains at least one of the current of the motor 27, the rotational speed of the motor 27, and the position of the rotor, and the additional parameter may be obtained by calculation or estimation using the obtained parameter.

The controller 23 is electrically connected to the driving circuit 24 for controlling the driving circuit 24 to operate. In some embodiments, the controller 43 employs a dedicated control chip (e.g., MCU, micro control unit, microcontroller Unit).

The driving circuit 24 is electrically connected to the controller 23 and the motor 27, and is capable of driving the motor 27 to operate according to a control signal of the controller 23. For a three-phase motor, the drive circuit 24 is in particular electrically connected to the three-phase windings of the motor 27. The driving circuit 24 specifically includes a switching circuit for driving the rotor of the motor 27 to operate according to a control signal of the controller 23. Of course, the number of phases of the motor 27 may be other phases, and is not limited herein.

In order to rotate the motor 27, the driving circuit 24 has a plurality of driving states, in which a stator winding of the motor 27 generates a magnetic field, and the controller 23 is configured to output a corresponding driving signal to the driving circuit 24 according to a rotor rotation position of the motor 27 to cause the driving circuit 24 to switch the driving states, thereby changing a state of a voltage and/or a current applied to the winding of the motor 27, generating an alternating magnetic field to drive the rotor to rotate, and thus realizing operation of the motor 27.

Fig. 2 shows an exemplary driving circuit 24, which includes switching elements Q1, Q, Q, Q4, Q5, and Q6, where the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 form a three-phase bridge, and Q1, Q3, and Q5 are upper bridge switches, and Q2, Q4, and Q6 are lower bridge switches. The switching elements Q1 to Q6 may be field effect transistors, IGBT transistors, or the like. The control terminals of the switching elements are electrically connected to the controller 23, respectively, and the switching elements Q1 to Q6 change the on state according to the driving signal output from the controller 23, thereby changing the voltage and/or current state of the power supply device 21 applied to the windings of the motor 27, and driving the motor 27 to operate. Of course, the invention is not limited to drive circuits using any particular number of switches and motors of any particular number of phases.

Referring to fig. 4, as an exemplary controller 43, specifically, it includes: a first rotating speed ring 431, a first current distribution unit 432, a first current ring 433, a second current ring 434, a first voltage conversion unit 435, a current conversion unit 437, a first control signal generation unit 436.

The governor mechanism 48 may be the governor mechanism 14 shown in fig. 1 for a user to set the target rotational speed n0 of the motor 47. The first rotating speed ring 431 is connected to the speed regulating mechanism 48 and the position and speed detecting module 452 in association, and the first rotating speed ring 431 acquires the target rotating speed n0 of the motor 47 set by the user from the speed regulating mechanism 48 and the actual rotating speed n of the motor 47 detected by the position and speed detecting module 452.

The first rotation speed ring 431 is used for generating a target current is0 according to the target rotation speed n0 and the actual rotation speed n of the motor 47. Specifically, the first rotation speed ring 431 is capable of generating the target current is0 by comparing and adjusting according to the target rotation speed n0 and the actual rotation speed n of the motor 47.

The first current distribution unit 432 is connected to the first rotating ring 431 for distributing the first target current id0 and the second target current iq0 according to the target current is 0. The target current is0, the first target current id0 and the second target current iq0 are vectors with directions and magnitudes, wherein the directions of the first target current id0 and the second target current iq0 are perpendicular to each other, and the target current is0 is synthesized by the vectors of the first target current id0 and the second target current iq0. Wherein the first target current id0 and the second target current iq0 may be obtained according to the following formula:

Wherein, ψ _f is the flux linkage generated by the permanent magnets in the rotor, and L _q、L_d is the d-axis and q-axis inductances of the stator windings, respectively. I _s is the target current is0 generated by the first rotating ring 231 according to the target rotating speed n0 and the actual rotating speed n of the motor 27.

The current detection module 451 transmits the detected three-phase currents Iu, iv, iw in actual operation of the motor 47 to the current conversion unit 436 in the controller 43. The first current transformation unit 236 obtains three-phase currents Iu, iv, iw, performs current transformation, and transforms into two-phase currents according to the three-phase currents Iu, iv, iw, which are a first actual current id and a second actual current iq, respectively.

The first current loop 433 is connected to the first current distribution unit 432 and the current conversion unit 437, acquires the first target current id0 and the first actual current id, and generates the first voltage adjustment amount Ud based on the first target current id0 and the first actual current id.

The second current loop 434 is connected to the first current distribution unit 432 and the current conversion unit 437, acquires the second target current iq0 and the first actual current iq, and generates the second voltage adjustment amount Uq based on the second target current iq0 and the second actual current iq.

The first voltage conversion unit 435 is connected to the first current loop 433 and the second current loop 434, acquires the first voltage adjustment amount Ud and the second voltage adjustment amount Uq, and the position of the rotor of the motor 47 from the position and speed detection module 452, and can convert the first voltage adjustment amount Ud and the second voltage adjustment amount Uq into intermediate amounts Ua and Ub related to three-phase voltages Uu, uv, uw applied to the motor 47 and output the intermediate amounts Ua and Ub to the first control signal generation unit 436, and the first control signal generation unit 436 generates PWM signals for controlling the switching elements of the driving circuit 44 based on the intermediate amounts Ua and Ub, so that the power supply device 41 can output three-phase voltages Uu, uv, uw applied to the windings of the motor 47, the Uu, uv, uw being three-phase symmetrical sine wave voltages or saddle wave voltages, the three-phase voltages Uu, uv, uw being 120 ° out of phase with each other.

That is, in the present embodiment, the first current distribution unit 432 is configured to distribute the direct-axis target current and the quadrature-axis target current according to the target current of the motor 47 generated by the first rotating speed ring 431; the current transformation unit 427 is used for generating a direct-axis actual current and a quadrature-axis actual current according to the actual current of the motor 47 and the position of the rotor of the motor; the first current loop 433 is used for generating a first voltage adjustment amount Ud according to the direct-axis target current and the direct-axis actual current; the second current loop 434 is configured to generate a second voltage adjustment amount Uq according to the quadrature target current and the quadrature actual current; the first voltage conversion unit 435 is configured to generate a first voltage control amount Ua and a second voltage control amount Ub according to the first voltage adjustment amount Ud and the second voltage adjustment amount Uq; the first control signal generation unit 436 generates a control signal for controlling the drive circuit 44 based on the first voltage control amount Ua and the second voltage control amount Ub. The control signal is a PWM signal. The duty cycle of the PWM signal varies following the change in the position of the rotor. The controller 43 controls the drive circuit 44 so that the input voltage to the motor 47 varies approximately in a sine wave. The motor 47 is a three-phase motor, and three-phase input voltages of the motor 47 mutually form 120-degree phase angles.

The control method of the present embodiment includes: the current conversion unit 437 acquires the detected three-phase currents Iu, iv, iw and rotor position information of the current detection module 45, performs current conversion, and converts the three-phase currents Iu, iv, iw into two-phase currents, which are the first actual current id and the second actual current iq, respectively.

The first current loop 433 acquires the first target current id0 and the first actual current id described above, and generates a first voltage adjustment amount Ud based on the first target current id0 and the first actual current id.

The second current loop 434 acquires the above-described second target current iq0 and first actual current iq, and generates a second voltage adjustment amount Uq based on the second target current iq0 and second actual current iq.

The first voltage conversion unit 435 acquires the first voltage adjustment amount Ud and the second voltage adjustment amount Uq and the rotor position, and converts the first voltage adjustment amount Ud and the second voltage adjustment amount Uq into a first voltage control amount Ua and a second voltage control amount Ub related to the three-phase voltages Uu, uv, uw applied to the motor 47, and outputs the first voltage control amount Ua and the second voltage control amount Ub to the first control signal generation unit 436, and the first control signal generation unit 436 generates PWM signals for controlling the switching elements of the driving circuit 44 based on the first voltage control amount Ua and the second voltage control amount Ub, so that the power supply device 41 outputs the three-phase voltages Uu, uv, uw applied to the windings of the motor 47, uu, uv, uw being three-phase symmetrical sine wave voltages or saddle wave voltages, uu, uv, uw being 120 ° out of phase with each other.

The motor 47 may be a motor 50 as shown in fig. 5, and the motor 50 is a brushless permanent magnet motor. The motor 50 includes a stator 511, a rotor 52, and a rotor output shaft 573. The rotor 52 may be provided inside the stator 511 or outside the stator 51, and is not limited thereto. In the present embodiment, taking an inner rotor motor as an example, a rotor 52 is built in a stator 51, a rotor output shaft 53 is fixedly connected with the rotor 52, and when the rotor 52 rotates, the rotor output shaft 53 rotates to drive the functional element 12 to work. The stator 51 includes a stator winding (not shown) disposed in the stator 51. The present invention is not limited to the above motor, and may have other phase numbers, other slot numbers, and other pole numbers.

The rotor 52 includes a permanent magnet 521 and a rotor core 522, and slots for mounting the permanent magnet 521 are provided in the rotor core 522 such that inductances (i.e., ld and Lq) of the rotor 52 in the directions of a straight axis (D axis) and a quadrature axis (Q axis) are unequal, and the rotor 52 can generate two different types of torques including a permanent magnet torque T1 generated by the permanent magnet 521 and a reluctance torque T2 generated by the rotor core 522, and the permanent magnet torque T1 and the reluctance torque T2 vector-combine to form a total electromagnetic torque Te that rotates the rotor 52. The direct axis D axis and the quadrature axis Q axis correspond to the D axis and the Q axis in fig. 7 and 15, respectively, and an electrical angle between the D axis and the Q axis is 90 °. The d-axis is the straight axis and the q-axis is the quadrature axis.

The relationship among the permanent magnet torque T1, the reluctance torque T2, and the electromagnetic torque Te is shown in fig. 6, wherein the horizontal axis represents the electrical angle in degrees, the vertical axis represents the torque in N.m, and the vector combination of the permanent magnet torque T1 and the reluctance torque T2 represents the electromagnetic torque Te, and the electrical angle is defined as the torque angle of the motor 50 for convenience of description. The relation between the permanent magnet torque T1, the reluctance torque T2 and the electromagnetic torque Te is as follows:

Te＝1.5P_n[Ψ_fi_q+(L_d-L_q)i_di_q]，

The formula includes two terms, the former 1.5P _nΨ_fi_q is the permanent magnet torque T1, as shown by the curve T1 in FIG. 6; the latter 1.5P _n(L_d-L_q)i_di_q is the reluctance torque T2, as shown by curve T2 in FIG. 6; te is a combination of curve T1 and curve T2, and is the Te curve in FIG. 6, wherein ψ _f is the rotor flux linkage, i _q is the q-axis current, i _d is the d-axis current, ld is the d-axis inductance of the stator winding, and Lq is the q-axis inductance of the stator winding. As can be seen from fig. 6, the resultant electromagnetic torque Te has an approximate maximum Tmax or maximum Tmax in the range of 90 ° to 135 ° of the corresponding torque angle. In an embodiment of the invention, the current id <0 is actually applied to the motor stator during operation: in the above formula, assuming that, in the case of id=0, t1=1.5p _nΨ_fi_q, that Is, when the maximum value of T1 Is 1.5p _nΨ_f Is (when id=0, i _q =is), where kt=1.5p _nΨ_f, the maximum value of T1 Is KtIs, is the phase current input to the motor, P _n Is the pole pair number of the magnet, for example, 4 magnets has 2 pole pairs, and y _f Is the flux linkage constant of a certain motor; then, when the power tool is actually running, the motor stator current id <0 and L _d<L_q are loaded, then the maximum Tmax of Te at this time > KtIs. In this formula, i _q corresponds to the first target current id0 in fig. 4, and i _d corresponds to the second target current iq0. In other embodiments of the present invention, the included angle between the stator flux linkage and the rotor flux linkage may be varied within a range of 90 ° to 135 ° according to the actual characteristics and actual current of different motors.

As one embodiment, in the present embodiment, with the controller 43 as shown in fig. 4, the controller 43 is configured to: the current applied to the stator is dynamically adjusted according to at least one of the current of the motor 47, the rotation speed of the motor 47 and the position of the rotor so that the included angle between the stator flux linkage and the rotor flux linkage is in the range of 90-135 degrees. That is, the controller 43 dynamically controls the current applied to the stator according to the rotation speed, current and rotor position of the motor 47 obtained by direct acquisition or detection to adjust the stator flux such that the angle between the stator flux and the rotor flux varies within the range of 90 ° to 135 °. Of course, the current loaded to the stator can be dynamically controlled according to the rotation speed and current of the motor to adjust the stator flux linkage according to the actual working condition of the electric tool, so that the included angle between the stator flux linkage and the rotor flux linkage is continuously maintained at the angle at which an approximate maximum Tmax or the maximum Tmax is obtained, that is, the Tmax is continuously maintained at more than KtIs at the moment, and the output performance of the electric tool can be greatly improved. It should be noted that, in the present invention, the "the controller obtains at least one of the rotational speed of the motor, the current of the motor, and the rotor position of the motor" means that the controller obtains at least one of the rotational speed of the motor, the current of the motor, and the rotor position of the motor, and other parameters of the three parameters may be obtained by calculation or estimation according to the obtained parameters, and the controller ultimately obtains the rotational speed of the motor, the current of the motor, and the rotor position of the motor by direct or indirect obtaining, which will not be described in detail below.

In other embodiments, the included angle between the stator flux linkage and the rotor flux linkage may also range from 90 ° to 120 °. In other embodiments, the included angle between the stator flux linkage and the rotor flux linkage may also be in the range of 110 ° to 120 °. In other embodiments, the included angle between the stator flux linkage and the rotor flux linkage may also be in the range of 110 ° to 130 °. In other embodiments, the included angle between the stator flux linkage and the rotor flux linkage may also be in the range of 105 ° to 115 °. In other embodiments, the included angle between the stator flux linkage and the rotor flux linkage may be in the range of 90 ° to 165 °. In the preferred embodiment of the invention, the included angle between the stator flux linkage and the rotor flux linkage can be continuously maintained at approximately Tmax or Tmax by regulating and controlling, so that the synthesized electromagnetic torque Te can reach the maximum value as much as possible, and the output torque of the motor is greatly improved.

In the preferred embodiment of the present invention, the three phases Uu, uv, uw loaded on the motor 47 are controlled so that the included angle between the stator flux linkage and the rotor flux linkage of the motor 27 is between 90 ° and 135 °, and the three phases Uu, uv, uw are three-phase symmetrical sine wave voltages or saddle-shaped waveforms, and are 120 ° phase difference with each other.

Fig. 7 shows the control mode of the present invention from the perspective of the space vector of the motor 47, in this embodiment, the controller 43 is adopted as shown in fig. 4, and the controller 43 controls the three-phase voltages Uu, uv, uw loaded on the motor 47 to control the current loaded on the stator, so that the stator winding generates a stator current space vector is0, the stator current space vector is0 is in phase with a stator flux linkage space vector ψs, and the included angle β between the stator flux linkage ψs and a rotor flux linkage ψf is the torque angle represented by the horizontal axis in the curve shown in fig. 6. Specifically, the controller 43 controls the voltage applied to the motor 47 to control the current applied to the stator according to the rotation speed, current and rotor position of the motor 47 obtained directly or through detection, the voltage applied to the stator is three-phase symmetrical sine wave voltages Uu, uv, uw, the three-phase voltages Uu, uv, uw are 120 ° phase difference with each other, the current applied to the stator causes the stator to generate a stator flux linkage, and the controller 43 dynamically adjusts the current to make the value range of the included angle β between the stator flux linkage ψs and the rotor flux linkage ψf be 90 ° to 135 °.

Referring to fig. 4 and 7, the controller 47 obtains a target speed n0 of the motor 47 according to the speed regulating mechanism 48 and an actual speed n of the motor 47 obtained by the position and speed detecting module 452, and obtains a target current is0 through the first rotating speed loop according to the target speed n0 and the actual speed n, and then the first current distribution unit 432 distributes the first target current id0 and the second target current iq0 according to the target current is 0. The target current is0 in fig. 4 corresponds to the current space vector is0 in fig. 7, the first target current id0 in fig. 4 corresponds to the current id0 of the d-axis component in fig. 7, and the second target current iq0 corresponds to the current iq0 of the q-axis component in fig. 7.

Meanwhile, the controller 43 obtains a first actual current id and a second actual current iq by converting the three-phase currents Iu, iv, iw detected by the current detection module 451 and the rotor position of the motor 47 detected by the position and speed detection module 452 through the current-to-current conversion unit 437, then obtains a first voltage adjustment amount Ud based on the first target current id0 and the first actual current id by using the first current loop 433, and obtains a first voltage adjustment amount Ud and a second voltage adjustment amount Uq based on the second target current iq0 and the second actual current iq by using the second current loop 434, and sends the converted results of the first voltage adjustment amount Ud and the second voltage adjustment amount Uq to the first control signal generation unit 436 through the first voltage conversion unit 435, the first control signal generating unit 436 generates a PWM signal according to the result transmitted from the first voltage converting unit 435, the PWM signal generated by the first control signal generating unit 436 controls the driving circuit 44 to control the power supply device 41 to apply three-phase voltages Uu, vu, ww to the motor 47, the three-phase voltages Uu, vu, ww being three-phase symmetrical sine wave voltages or saddle wave voltages, and the three-phase voltages Uu, vu, ww being 120 ° mutually different, and the three-phase voltages Uu, vu, ww applied to the motor 47 being capable of causing the stator windings to generate currents, the controller 43 controlling the stator currents to adjust the stator flux linkage such that the included angle β of the stator flux linkage ψs and the rotor flux linkage ψf ranges from 90 ° to 165 °.

Referring to fig. 4, 6 and 7, the first current distribution unit 432 in fig. 4 can generate the permanent magnet torque T1 and the reluctance torque T2 from the rotor of the motor 47 according to the first target current id0 and the second target current iq0 distributed by the target current is0, the electromagnetic torque Te obtained by the motor is synthesized by the vectors of T1 and T2, and te=1.5P _n[Ψ_f*iq0+(L_d-L_q) id0×iq0].

Fig. 8 shows the control of the drill shown in fig. 1 from the perspective of the motor bus current versus motor torque. The solid line is a control method according to the present embodiment, and the thick dotted line is a control method according to a conventional square wave. The horizontal axis represents motor output torque in N.m and the vertical axis represents motor bus current in A.

In this embodiment, the circuit system shown in fig. 2 and the controller 43 shown in fig. 4 are adopted, and the controller 43 controls the current of the motor 47 by controlling the voltage applied to the motor 47 by the power supply device 41, wherein the voltages are three-phase symmetrical sine wave voltages Uu, uv, uw, uu, uv, uw which are 120 ° phase difference.

Specifically, the controller 43 dynamically adjusts the current applied to the stator according to at least one of the rotational speed of the motor 47, the current of the motor, and the rotor position of the motor, so that the bus current of the motor changes in a first torque section (i.e., 0-Tm 0 torque section) with a first current torque characteristic curve, and changes in a second torque section (i.e., tm 0-Tm 1 torque section) with a second current torque characteristic curve, wherein the slope of a first virtual straight line L1 where 0 and Tm0 are selected in the first current torque characteristic curve is defined as a first slope, and the slope of a second virtual straight line L2 where Tm0 and Tm1 are selected in the second current torque characteristic curve is defined as a second slope, and the first slope of the first virtual straight line L1 where the first current torque characteristic curve is greater than the second slope of the second virtual straight line L2 where the second current torque characteristic curve is located. Alternatively, the first slope is a slope of any point of the first current torque characteristic curve in the first torque section (i.e., the 0 to Tm0 torque section), and the second slope is a slope of any point of the second current torque characteristic curve in the second torque section (i.e., the Tm0 to Tm1 torque section). That is, the bus current of the motor 47 has an inflection point R, and a first slope before the inflection point R is greater than a second slope after the inflection point R. That is, the bus current of the motor increases with motor torque at a faster rate before the inflection point, and increases with motor torque at a slower rate after the inflection point. Namely, the first current torque characteristic curve and the second current torque characteristic curve increase with increasing bus current of the torque, but the first current torque characteristic curve increases with increasing current of the torque at a faster rate, and the second current torque characteristic curve increases with increasing current of the torque at a slower rate. That is, in the control method of the present embodiment, the electric current increases at a faster rate in the case of a light load; the current increases at a slower rate under heavy load conditions.

Referring to fig. 8, in the control mode of the present invention, when the controller 43 controls the driving circuit 44 to rotate the motor 47 with a preset torque, the output current of the power supply device 41 is the second output current; assuming that the output current of the power supply device 41 is a first output current when the controller 43 controls the driving circuit 44 in the first control manner to rotate the motor 47 at the preset torque; wherein the second output current is less than the first output current. In this embodiment, the first control mode is a conventional square wave control mode.

It should be noted that, in the present invention, the "assumption that the controller controls the driving circuit in the first control manner" or the "assumption that the controller controls the driving circuit in the third control manner" is merely used to compare the control manner of the present invention with other control manners, and alternatively, the first control manner and the third control manner are conventional square wave control manners. That is, the controller 43 of the present invention is used only for implementing the control method of the present invention, and is not used for implementing the first control method or the third control method to control the driving circuit 44. The following description will be omitted for the description of the "assumption that the controller controls the driving circuit in the first control manner" or "assumption that the controller controls the driving circuit in the third control manner" both as described above.

As a specific example, the preset torque is set to Tm2, at this time, the first output current outputted by the power supply 41 is made to correspond to the motor bus current I1 in fig. 8 by using the conventional square wave control method, and the second output current outputted by the power supply 41 is made to correspond to the motor bus current I2 in fig. 8 by using the control method of the present embodiment, and the second output current I2 is smaller than the first output current I1.

With reference to fig. 8 and 11, in the heavy load region, the control method of the present embodiment is smaller in bus current of the motor 47 and smaller in output current of the power supply device 41 under the same output torque, and the output power of the electric tool 10 is higher, so that energy can be saved, and the navigation ability of the battery pack can be improved for using the battery pack as the power supply device 41, compared with the conventional square wave control method.

Fig. 9 is a graph showing a control mode of the electric drill shown in fig. 1 from the perspective of a motor rotation speed versus motor torque curve. In this embodiment, the circuit system shown in fig. 2 and the controller 43 shown in fig. 4 are adopted, and the controller 43 controls the current of the motor 47 by controlling the voltage applied to the motor 47 by the power supply device 41, wherein the voltages are three-phase symmetrical sine wave voltages Uu, uv, and Uw, and Uu, uv, and Uw are 120 ° phase difference with each other.

Specifically, the controller 43 dynamically adjusts the current applied to the stator according to at least one of the rotation speed of the motor 47, the current of the motor and the rotor position of the motor, the controller 43 controls the current applied to the stator by controlling the voltage applied to the motor 47, the voltages applied to the stator are three-phase symmetrical sine wave voltages Uu, uv, uw, the three-wire voltages Uu, uv, uw are 120 ° out of phase with each other, the current applied to the stator causes the stator to generate a stator flux linkage, and the controller 43 dynamically adjusts the current applied to the stator so that the value of the included angle between the stator flux linkage and the rotor flux linkage is in the range of 90 ° to 135 °.

When the controller 43 of the present embodiment controls the drive circuit 44, the motor 47 obtains a second constant-speed torque section; assuming that the controller 43 controls the drive circuit 44 in the first control manner, the motor 47 obtains a first constant-speed torque section; wherein the length of the second constant speed torque section is greater than the length of the first constant speed torque section.

In fig. 9, the horizontal axis represents motor output torque in N.m and the vertical axis represents motor rotation speed n in rpm. Wherein the solid line is the effect curve of the motor speed changing along with the motor torque by adopting the control mode of the embodiment, and the thick dotted line represents the effect curve of the motor speed changing along with the motor torque by adopting the traditional square wave control mode. In the present embodiment, the motor rotation speed is substantially in a constant speed state in the torque range of 0 to Tm4, whereas the conventional square wave control method does not have such a long constant speed range.

As can be seen from fig. 9, compared with the conventional square wave control method, the control method of the present embodiment has the advantage of a wide constant speed range, which has a wide constant speed characteristic for some electric tools with a light and medium load range, such as an electric drill, an electric screwdriver, and the like, and can obtain a better and more consistent working effect.

In the present embodiment, the controller 43 controls the driving circuit 44 such that the motor 47 obtains the second rotation speed when the motor 47 is rotated in a preset torque section; assuming that the controller 43 controls the driving circuit 44 in a first control manner so that the motor obtains a first rotation speed when the motor rotates in the preset torque section; wherein the second rotational speed is greater than the first rotational speed. Referring to fig. 9, alternatively, the preset torque interval is set to be a torque interval with a torque greater than Tm4, i.e., greater than Tm 4), for example, tm3 to Tm2 torque intervals as in fig. 9, and when the motor outputs the same torque (e.g., tm 2), the motor rotation speed is higher than that of the conventional square wave control, which means higher operation efficiency for a power tool such as an electric drill. And, in combination with fig. 8 and 9, when the torque (for example, tm 2) is preset, the motor rotation speed is higher than that of the conventional square wave control method, but the required current is smaller than that of the conventional square wave control method, that is, the control method of the present invention can obtain a higher rotation speed by a smaller current, and for the electric tool using the battery pack as the power supply device 41, the cruising ability of the battery pack can be improved.

Fig. 10 compares the effect of the control method of the present embodiment with that of the conventional square wave control from the viewpoint of the motor efficiency versus motor torque. Wherein the horizontal axis represents motor output torque in N.m units, and the vertical axis represents motor efficiency in no units. The solid line is an effect curve of the motor efficiency according to the motor torque by the control method according to the present embodiment, and the thick dotted line is an effect curve of the motor efficiency according to the motor torque by the conventional square wave control method. As can be seen from fig. 10, the motor employing the control mode of the embodiment is higher in efficiency than the conventional square wave control mode.

Fig. 11 shows the manner in which the drill shown in fig. 1 is controlled from the power tool output versus motor torque curve. Wherein the horizontal axis represents motor output torque in N.m and the vertical axis represents power output of the electric tool in W. The solid line is a control mode of the present embodiment, and the thick dotted line indicates a conventional square wave control mode.

The controller 43 of the present embodiment controls the driving circuit 44 to make the output power of the electric tool 10 be the second output power w2 when the motor 47 rotates at a preset torque (e.g., tm 6) in a preset torque interval (e.g., greater than Tm 5); assuming that the controller 44 controls the driving circuit 44 in the first control manner so that the output power of the electric tool 10 is the first output power w1 when the motor 47 rotates at the preset torque (e.g., tm 6) in the preset torque interval (e.g., greater than Tm 5); wherein the second output power w2 is larger than the first output power w1. In this embodiment, the first control mode is a conventional square wave control mode.

As can be seen from fig. 11, the control method of the present embodiment enables the motor 47 to output higher power of the electric power tool 10 when the output torque is the same, as compared with the conventional square wave control method. Referring to fig. 8 and 11, when the motor rotates (e.g., tm 2) at a certain preset torque within a certain preset torque interval (e.g., greater than Tm 1), the control method of the present invention outputs a smaller current from the power supply device 41 and at the same time outputs a higher power from the power tool, as compared to the conventional square wave control method, thereby enabling a higher cruising ability of the battery pack as the power supply device 41.

Referring to fig. 8, 9 and 11, when the motor rotates (e.g., tm 2) with a certain preset torque within a certain preset torque interval (e.g., greater than Tm 1), the control method of the present invention makes the current output from the power supply device 41 smaller, and at the same time, the output power of the electric tool 10 is higher, the rotation speed of the motor 47 is higher, so that the cruising ability of the battery pack as the power supply device 41 can be made higher, as compared with the conventional square wave control method.

Of course, the above embodiment is not limited to the above embodiment in which the controller 43 of fig. 4 is used to indirectly control the stator flux by controlling the current or voltage vector to adjust the angle between the stator flux and the rotor flux, and the controller 73 of fig. 14 may be used to directly control the stator flux to adjust the angle between the stator flux and the rotor flux, which can achieve the above effect. Specifically, the controller 73 includes: a second rotation speed ring 731 for generating a target torque of the motor 77 according to the target rotation speed and the actual rotation speed of the motor 77. The controller 73 further includes: a torque ring 733 for generating a third voltage adjusting amount v1 according to the target torque and the actual torque of the motor 77; a magnetic link 734 for generating a fourth voltage adjustment quantity v2 from the target stator flux and the actual stator flux of the motor 77; a second voltage conversion unit 735 for generating a third voltage control amount uα and a fourth voltage control amount uβ according to the third voltage adjustment amount v1 and the fourth voltage adjustment amount v2; a second control signal generating unit 736 for generating control signals according to the third voltage control amount uα and the fourth voltage control amount uβ, the control signals being for controlling the driving circuit.

Fig. 12 and 13 exemplarily show another electric tool 60, the electric tool 60 being an angle grinder, which mainly includes a housing 61, a functional member 62, a grip 63, a speed regulating mechanism 64, a motor 65, and a power supply device 66.

The housing 61 is formed with a grip 63, and the grip 63 is gripped by a user, but the grip 63 may be a separate component. The housing 61 constitutes a main body portion of the power tool 60 for accommodating a motor 65, a transmission mechanism, and other electronic components such as a circuit board. The front end of the housing 61 is used for mounting the functional element 62.

The functional element 62 is used for realizing the function of the electric tool 60, and is driven to operate by the motor 65. The functional elements are different for different power tools 60. For angle grinders, the functional member 62 is a blade for performing a grinding or cutting function. The functional element 62 is operatively connected to the motor 65, in particular the functional element 62 is electrically connected to the motor 65 via an output shaft 69 and a transmission 68.

The speed governor mechanism 64 is used to set at least a target rotational speed of the motor 65, that is, the speed governor mechanism 64 is used to achieve speed governor of the motor 65, and the speed governor mechanism 65 may be, but is not limited to, a trigger, a knob, a sliding mechanism, or the like. In the present embodiment, the speed regulating mechanism 64 is configured as a slide mechanism.

The power supply 66 is used to provide power to the power tool 60. In this embodiment, the power tool 60 is powered by a battery pack 66. Alternatively, the power tool 60 further includes a battery pack coupling portion 67 for connecting the battery pack 66 to the power tool 60. In other embodiments, the power supply 66 may also be an ac power source, which may be 60V or 220V ac mains, and the power supply 66 includes a power conversion unit connected to the ac power for converting the ac power into electrical energy for use by the power tool.

The operation of the power tool 60 described above also relies on circuitry. Referring to fig. 14, as an exemplary circuit system, wherein the controller 73 includes: a second rotation speed loop 731, a second current distribution unit 732, a torque loop 733, a flux linkage loop 734, a second voltage conversion unit 735, a second control signal generation unit 736, a second current conversion unit 737, a torque and flux linkage calculation unit 738, a target flux linkage calculation unit 739, and a feedback linearization control unit 730. The feedback linearization control unit 730 and the second voltage conversion unit 735 may be collectively referred to as a voltage change unit, which are both configured to perform voltage conversion.

Referring to fig. 15 to 17, the controller 73 is configured to perform the following operations: in a first load section (0 to Tn 1), the drive circuit 74 is controlled in a first characteristic control manner to rotate the motor 77 in a first rotation speed range; in a second load interval (greater than Tn 1), the drive circuit 74 is controlled in a second characteristic control manner to rotate the motor 77 in a second rotation speed range; the first characteristic control method includes: dynamically adjusting the current loaded to the stator according to at least one of the current of the motor 47, the rotating speed of the motor 47 and the position of the rotor of the motor 47 so as to enable the value range of the included angle beta between the stator flux linkage and the rotor flux linkage to be 135-180 degrees; the second characteristic control method includes: dynamically adjusting the current loaded to the stator according to at least one of the current of the motor 77, the rotating speed of the motor 77 and the position of the rotor of the motor 77 to enable the value range of the included angle beta between the stator flux linkage and the rotor flux linkage to be 90-135 degrees; wherein the output torque of the motor 77 when the controller 73 controls the driving circuit 74 in the second characteristic control manner is greater than the output torque of the motor 77 when the controller 73 controls the driving circuit 74 in the first characteristic control manner (see fig. 17). The output torque of the motor and the electromagnetic torque Te of the motor are in positive correlation, and the larger the electromagnetic torque Te of the motor is, the larger the output torque of the motor is.

That is, in the first load section (the torque section of 0 to Tn 1), the controller 77 controls in a first characteristic control manner of regulating and controlling the angle between the stator flux linkage and the rotor flux linkage; and in a second load interval (a torque interval section larger than Tn 1), the control is performed in a second characteristic control mode for regulating and controlling the included angle between the stator flux linkage and the rotor flux linkage and obtaining the approximate Tmax or Tmax. Specifically, the first characteristic control method includes: dynamically adjusting the current applied to the stator according to at least one of the current of the motor 77, the rotational speed of the motor 77 and the position of the rotor so that the value of the included angle beta between the stator flux linkage and the rotor flux linkage is in the range of 135-180 degrees, so that the torque of the motor 77 operates at a value not greater than or equal to a preset threshold KtIs, wherein kt=1.5 Pn ψf, pn is the number of pole pairs of the magnets, for example, 4 magnets have 2 pole pairs, and ψf is the flux linkage constant of the motor; is the phase current of the motor. The second characteristic control mode includes: dynamically adjusting the load to the stator flux according to at least one of the current of the motor 77, the rotational speed of the motor 77 and the position of the rotor so that the value range of the included angle beta between the stator flux and the rotor flux is 90-135 degrees, so that the torque of the motor 77 operates in a preset time range continuously greater than a preset threshold KtIs, wherein kt=1.5 Pn ψf, pn is the number of pole pairs of the magnets, for example, 4 magnets have 2 pole pairs, and ψf is the flux constant of the motor; is the phase current of the motor; wherein the output torque of the motor 77 when the controller 73 controls the driving circuit 74 in the second characteristic control manner is greater than the output torque of the motor 77 when the controller 73 controls the driving circuit 74 in the first characteristic control manner.

In other embodiments of the present invention, in the first characteristic control manner, the value range of the included angle between the stator flux linkage and the rotor flux linkage may be regulated to be 90 ° to 120 °, or 90 ° to 135 °, or 110 ° to 120 °, or 110 ° to 130 °, or 110 ° to 140 °, or 105 ° to 135 °, or 115 ° to 145 °, or 120 ° to 160 °, or 135 ° to 165 °, or 150 ° to 180 °, so that the torque of the motor 77 operates at a value not greater than the preset threshold KtIs; in the second characteristic control mode, the value range of the included angle between the stator flux linkage and the rotor flux linkage can be regulated and controlled to be 110-120 degrees, or 110-130 degrees, or 105-115 degrees, or 115-135 degrees, or 120-145 degrees, but the torque of the motor 77 can be operated in a preset time range to be continuously larger than a preset threshold KtIs. Specifically, the second rotation speed ring 731 in the controller 73 acquires the actual rotation speed n of the motor 77 from the position and speed detecting module 752 and the target rotation speed n 0of the motor set by the user through the speed regulating mechanism 78, and outputs the target electromagnetic torque Te0 according to the actual rotation speed n of the motor and the target rotation speed n 0of the motor. The speed governor 78 may employ the speed governor 64 shown in fig. 12.

The second current distribution unit 732 distributes the first target id0 and the second target current iq0 according to the target torque Te0 output from the second rotation speed ring 731. Referring to fig. 15, the first and second target currents id0 and iq0 are vectors having directions and magnitudes, and an electrical angle between the first and second target currents id0 and iq0 is 90 °, the first and second target currents id0 and iq0 being located on d-and q-axes, respectively, and the first and second target currents iq0 and iq0 being able to vector-synthesize the target current is0. The target flux linkage calculation unit 739 can calculate a target stator flux linkage ψs0 from the first target id0 and the second target current iq0, the target stator flux linkage ψs0 being in the same direction as the target current is0. In this way, the controller 73 controls the included angle β between the stator flux linkage ψs and the rotor flux linkage ψf to be in the range of 90 ° to 135 ° or 135 ° to 180 ° by directly and dynamically adjusting the stator flux linkage, so as to improve the output performance of the electric tool under different actual working conditions.

The target stator flux linkage ψs0 and the target electromagnetic torque Te0 are compared and adjusted with the actual stator flux linkage ψs0 and the actual electromagnetic torque Te, and a control signal is generated to adjust the actual stator flux linkage ψs and the actual electromagnetic torque Te so that the actual stator flux linkage ψs0 and the actual electromagnetic torque Te can reach the target stator flux linkage ψs0 and the target electromagnetic torque Te0 as much as possible. The angle between the actual stator flux linkage ψs and the rotor flux linkage ψf is preferably in the range of 90 ° to 135 °, or 135 ° to 180 °. That is, by establishing a functional relationship of te=f (ψs, ψf, β), the stator flux is dynamically adjusted so that the included angle between the actual stator flux ψs and the actual rotor flux ψf is in the range of 90 ° to 135 °. In other embodiments of the present invention, the stator flux may also be dynamically adjusted by establishing a te=f (ψs, ψf, β) function such that the angle between the stator flux and the rotor flux may also range from 90 ° to 120 °, or 110 ° to 130 °, or 110 ° to 140 °, or 105 ° to 115 °, or 115 ° to 145 °, or 120 ° to 160 °, or 135 ° to 165 °.

Specifically, the second current transformation unit 737 acquires the detected three-phase currents Iu, iv, iw of the current detection module 731 and the position θ of the rotor of the output of the position and speed detection module 732, transforms the three-phase currents Iu, iv, iw into two-phase actual currents id and iq, the directions of id and iq being vectors having directions and magnitudes, and the directions of id and iq being perpendicular to each other.

The torque and flux linkage calculation unit 738 acquires the two-phase actual currents id and iq from the second current transformation unit 737, and generates the actual electromagnetic torque Te and the actual stator flux linkage ψs from the two-phase actual currents id and iq. The actual electromagnetic torque Te is output to torque ring 733 and the actual flux linkage ψs is output to flux linkage ring 734.

The torque ring 733 acquires the actual torque Te calculated by the torque and flux linkage calculation unit 738 and the target electromagnetic torque Te0 output by the second rotation speed ring 731, and generates the voltage adjustment amount v1 based on the actual electromagnetic torque Te and the target electromagnetic torque Te 0.

The flux linkage 734 acquires the actual stator flux linkage ψs calculated by the torque and flux linkage calculation unit and the target stator flux linkage ψs0 generated by the target flux linkage calculation unit 739, and generates a voltage adjustment amount v2 according to the actual stator flux linkage ψs and the target stator flux linkage ψs 0.

The feedback linearization control unit 730 generates a voltage control amount Uq and a voltage control amount Ud in a d-q coordinate system from the voltage adjustment amount v1 generated by the torque loop 733, the voltage adjustment amount v2 generated by the flux linkage loop 734, and the d-axis component ψd and the q-axis component ψq of the actual stator flux linkage ψs generated by the torque and flux linkage calculation unit 738.

The second voltage conversion unit 735 acquires the first voltage control amount Uq and the second voltage control amount Ud, and converts the voltage control amount Uq and the voltage control amount Ud into a voltage control amount uα and a voltage control amount uβ in an α - β coordinate system.

The second control signal generation unit 736 generates PWM control signals for controlling the driving circuit 74 according to the voltage control amount uα and the voltage control amount uβ in the α - β coordinate system, so that the power supply device 71 outputs three-phase voltages Uu, uv, uw, which are three-phase symmetrical sine wave voltages or saddle wave voltages, to be applied to windings of the motor 77, 120 ° phase differences from each other, and the three-phases Uu, uv, uw applied to the motor 77 make an angle between the stator flux linkage ψs0 and the rotor flux linkage ψ _f be in a range of 90 ° to 135 °, or 135 ° to 180 °.

That is, the second rotation speed ring 731 is for generating a target torque of the motor 77 according to the target rotation speed and the actual rotation speed of the motor. The torque ring 733 is used to generate a third voltage adjusting amount v1 according to the target torque and the actual torque of the motor 77; the magnetic link 734 is configured to generate a fourth voltage adjustment v2 based on the target stator flux and the actual stator flux of the motor 77; the second voltage conversion unit 735 is configured to generate a third voltage control amount uα and a fourth voltage control amount uβ according to the third voltage adjustment amount v1 and the fourth voltage adjustment amount v 2. Optionally, the controller 73 further comprises a feedback linearization control unit 730, with an input connected to the torque loop 733 and the flux linkage loop 734 and an output connected to the second voltage conversion unit 735. The second control signal generation unit 736 is configured to generate control signals for controlling the drive circuit 74 based on the third voltage control amount uα and the fourth voltage control amount uβ. The control signal is a PWM signal, and the duty ratio of the PWM signal changes following the change in the position of the rotor. The controller 73 controls the driving circuit 74 so that the input voltage of the motor 77 varies approximately in a sine wave. The motor 77 is a three-phase motor, and three-phase input voltages of the motor 77 are 120 ° phase angle to each other.

In this way, direct torque control is directly performed according to the actually fed-back electromagnetic torque and the stator flux linkage, so that the included angle beta between the rotor flux linkage ψs and the stator flux linkage ψ _f of the motor is in the range of 90 ° to 135 °, or 135 ° to 180 °, thereby improving the driving performance of the motor 77.

Fig. 16 shows the manner of controlling the angle grinder shown in fig. 12 from the perspective of a motor speed versus motor torque curve. Wherein the horizontal axis represents motor output torque in N.m units and the vertical axis represents motor speed in rpm. The solid line is a control mode of the present embodiment, and the thick dotted line indicates a conventional square wave control mode.

As shown in fig. 16, since the load of the motor increases, the motor output torque should also increase accordingly, and in the present embodiment, the first load section corresponds to a torque section of 0 to Tn1 and the second load section corresponds to a torque section greater than Tn 1.

In the first load interval, the driving circuit 74 is controlled in a first characteristic control manner to rotate the motor 77 within a first preset rotation speed range, and the first characteristic control manner can control the motor to reach a higher rotation speed of the motor 77 after the voltage applied to the motor 77 reaches the maximum supply voltage of the power supply device 71. In the first load section, the motor 77 outputs a first rotation speed when the controller 73 controls the driving circuit 74 in the first characteristic control manner, and in the second load section, the motor 77 outputs a second rotation speed when the controller 73 controls the driving circuit 74 in the second characteristic control manner, and the motor 77 outputs a third rotation speed when the controller 73 controls the driving circuit 74 in the third control manner, wherein the first rotation speed is greater than the third rotation speed, and the second rotation speed is greater than the third rotation speed. In this way, compared with the traditional square wave control mode, the control mode of the embodiment makes the motor rotation speed higher than that of the traditional square wave control mode under the condition of the same motor output torque no matter the condition of light load or medium load. Alternatively, the third control mode is a conventional square wave control mode.

Referring to fig. 16 and 17, in a first load section (i.e., in the torque section 0 to Tm 3), the driving circuit 74 is controlled in a first characteristic control manner so that the motor 77 is smaller than a preset threshold value, which is set according to the characteristics of the motor and the current of the motor. In this embodiment, the magnitude of the preset threshold is KtIs, where kt=1.5 Pn ψf, pn is the number of pole pairs of the magnets, for example, 4 magnets have 2 pole pairs, and ψf is the flux linkage constant of the motor. Is the current of the motor. And in a second torque interval (i.e., greater than Tm3 interval), the drive circuit 74 Is controlled in a second characteristic control manner such that the torque of the motor 77 Is continuously greater than a preset threshold KtIs for at least a preset time period, the preset threshold KtIs being set in accordance with the characteristic kt of the motor and the current Is of the motor. Wherein the motor load torque of the first load section is less than the motor load torque of the second load section.

Of course, the present embodiment is not limited to the controller 73 of fig. 14, and the controller 43 of fig. 4 may be used to indirectly control the stator flux linkage by directly controlling the stator flux linkage to adjust the included angle between the stator flux linkage and the rotor flux linkage, so as to adjust the included angle between the stator flux linkage and the rotor flux linkage, and the motor speed of the present embodiment is higher than that of the conventional square wave control method under the same motor output torque no matter in light load or medium load. Specifically, the controller 73 includes a first current distribution unit 432 for distributing a direct-axis target current and a quadrature-axis target current according to the target current of the motor 47 generated by the first rotating speed ring 431; the current transformation unit 427 is used for generating a direct-axis actual current and a quadrature-axis actual current according to the actual current of the motor 47 and the position of the rotor of the motor; the first current loop 433 is used for generating a first voltage adjustment amount Ud according to the direct-axis target current and the direct-axis actual current; the second current loop 434 is configured to generate a second voltage adjustment amount Uq according to the quadrature target current and the quadrature actual current; the first voltage conversion unit 435 is configured to generate a first voltage control amount Ua and a second voltage control amount Ub according to the first voltage adjustment amount Ud and the second voltage adjustment amount Uq; the first control signal generation unit 436 generates a control signal for controlling the drive circuit 44 based on the first voltage control amount Ua and the second voltage control amount Ub. The control signal is a PWM signal. The duty cycle of the PWM signal varies following the change in the position of the rotor. The controller 43 controls the drive circuit 44 so that the input voltage to the motor 47 varies approximately in a sine wave. The motor 47 is a three-phase motor, and three-phase input voltages of the motor 47 mutually form 120-degree phase angles.

Fig. 18 compares the effects of the control method of the present embodiment with those of the conventional square wave control method from the perspective of the motor efficiency versus motor torque relationship, wherein the horizontal axis represents motor output torque in N.m and the vertical axis represents motor efficiency in no units. Wherein the solid line is the effect curve of the motor efficiency changing along with the motor torque in the control mode of the embodiment, and the thick dotted line represents the effect curve of the motor efficiency changing along with the motor torque in the traditional square wave control mode. As can be seen from the figure, the motor employing the control mode of the embodiment is more efficient in the light-medium load range than the conventional square wave control mode.

Referring to fig. 19, the effects of the control scheme of the present embodiment and the conventional square wave control scheme are compared from the perspective of the motor bus current versus motor torque curve, where the horizontal axis represents motor output torque in N.m and the vertical axis represents motor bus current in a. Wherein the solid line is the effect curve of the motor efficiency changing along with the motor torque in the control mode of the embodiment, and the thick dotted line represents the effect curve of the motor efficiency changing along with the motor torque in the traditional square wave control mode.

In the present embodiment, the bus current of the motor 77 increases with a first slope in a first torque section (for example, 0 to Tn 2) and increases with a second slope in a second torque section (for example, tn2 to t 4), wherein the first slope is larger than the second slope. In summary, in the present embodiment, the bus current of the motor 77 has the inflection point S, and the first slope before the inflection point is larger than the second slope after the inflection point S, regardless of whether the first load section is a torque section or the second load section, or the first load section is a torque section crossing the first load section and the second load section. That is, the bus current of the motor increases with the motor torque at a faster rate before the inflection point S, and the bus current of the motor increases with the motor torque at a slower rate after the inflection point. Alternatively, the first slope may be a slope of a virtual straight line connecting two end points 0 and Tn2 of the first torque section corresponding to the rotational speed, the second slope is a slope of a virtual straight line L3 connecting two end points of the second torque section, and the second slope is a slope of a virtual straight line L4 connecting two end points Tn2 and Tn4 of the second torque section corresponding to the rotational speed. Alternatively, the first slope is a slope of the motor bus current at any point on the torque curve over the first torque interval, and the second slope is a slope of the motor bus current at any point on the torque curve over the second torque interval.

In the present embodiment, when the controller 73 controls the driving circuit 74 in the second characteristic control manner to rotate the motor 77 at the preset torque, the output current of the power supply device 71 is the second output current; assuming that the controller 74 controls the driving circuit 74 in the third control manner to rotate the motor 77 at the preset torque, the output current of the power supply 71 is the third output current; wherein the second output current is less than the third output current. Alternatively, the third control mode is a conventional square wave control mode.

Referring to fig. 19, when the torque Tn4 is preset, the bus current of the motor in the second characteristic control mode of the present embodiment is I3, and the bus current in the conventional square wave control is I4, I3< I4. Therefore, the second control method of the embodiment is adopted, and the current output from the power supply device 71 is smaller at the time of medium-heavy load than the conventional square wave control method.

Referring to fig. 20, in the present embodiment, when the controller 73 controls the drive circuit 74 in the first characteristic control mode, the output power of the electric power tool 60 is the first output power; when the controller 73 controls the driving circuit 74 in the second characteristic control manner, the output power of the electric power tool 60 is the second output power; assuming that the controller 73 controls the driving circuit 74 in the third control manner, the output power of the electric power tool 60 is the third output power; the first output power is larger than the third output power, and the second output power is larger than the third output power. Alternatively, the third control mode is a conventional square wave control mode, that is, in the present embodiment, the output power of the electric tool 60 is higher than the output power of the electric tool 60 under the conventional square wave control, regardless of the first characteristic control mode or the second characteristic control mode.

Fig. 20 compares the effect of the control method of the present embodiment with that of the conventional square wave control method from the point of view of the variation curve of the output power of the electric tool with the motor torque, wherein the horizontal axis represents the motor torque in N.m, and the vertical axis represents the output power of the electric tool in W. As can be seen from fig. 20, the control method of the present embodiment is higher in output power of the electric power tool 60 when the motor output torque is the same as that of the conventional square wave control method.

Referring to fig. 19 and 20, in the control manner of the present invention, when the motor rotates (for example, tn 4) with a preset torque in a preset torque range (greater than Tn 3), the motor bus current is smaller, the output current of the power supply device 71 is smaller, and the output power of the electric tool 60 is higher, so that energy can be saved, which makes the cruising ability of the battery pack higher for the electric tool employing the battery pack as the power supply device 71.

Referring to fig. 16, 19 and 20, in the control manner of the present invention, when the motor rotates at the preset torque (for example, tn 4) in the preset torque range (greater than Tn 3), the current of the bus bar of the motor is smaller, the output current of the power supply 71 is smaller, and the output power of the electric tool 60 is higher, and the rotation speed of the motor is higher, so that energy can be saved, which makes the cruising ability of the battery pack higher for the electric tool using the battery pack as the power supply 71.

In the above embodiment of the present invention, the characteristic curves of fig. 8 to 11 are obtained by establishing a te=f (ψs, ψf, β) function relationship and dynamically adjusting the included angle between the stator flux linkages ψs and the rotor flux linkages ψf, or the characteristic curves of fig. 16 to 20 are obtained on the electric tool, so that the output performance of the electric tool of the present invention is better.

In other embodiments of the invention, the controller is configured to control the drive circuit based on at least one of a current of the motor, a rotational speed of the motor, and a position of the rotor, to output a PWM signal that varies in response to a variation in the position of the rotor such that an input voltage of the motor varies in an approximately sinusoidal or saddle-like manner, and to adjust an amplitude and/or phase of the input voltage and/or current to adjust an angle between the stator flux linkage and the rotor flux linkage such that the motor has a continuous, alternating current state on three-phase stator windings during at least one electrical cycle or portion of the electrical cycle, the three-phase input voltages of the motor being 120 ° phase angle to each other. The current states on the three-phase stator windings can synthesize vector moments which move continuously along the circumference approximately, and the rotor of the motor rotates synchronously along with the vector moments which move continuously along the circumference approximately. By the above control method, the electric power tool of the present invention can obtain more preferable output performance of fig. 8 to 11, or fig. 16 to 20.

The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be appreciated by persons skilled in the art that the above embodiments are not intended to limit the invention in any way, and that all technical solutions obtained by means of equivalent substitutions or equivalent transformations fall within the scope of the invention.

Claims

1. A power tool, comprising:

the motor comprises a stator and a rotor, and the motor is capable of generating reluctance torque;

A power supply device for supplying electric power to the motor;

The driving circuit is electrically connected with the motor to drive the motor;

a controller for controlling the driving circuit, the controller configured to perform the following operations:

In a first load interval, controlling the driving circuit in a first characteristic control mode to enable the motor to rotate in a first rotation speed range;

In a second load interval, controlling the driving circuit in a second characteristic control mode to enable the motor to rotate in a second rotating speed range;

the first characteristic control mode includes: dynamically adjusting the current loaded to the stator according to at least one of the current of the motor, the rotating speed of the motor and the position of the rotor of the motor so as to enable the value range of the included angle between the stator flux linkage and the rotor flux linkage to be 135-180 degrees;

The second characteristic control mode includes: dynamically adjusting the current loaded to the stator according to at least one of the current of the motor, the rotating speed of the motor and the position of the rotor of the motor so as to enable the value range of the included angle between the stator flux linkage and the rotor flux linkage to be 90-135 degrees;

Wherein the output torque of the motor when the controller controls the driving circuit in a second characteristic control manner is greater than the output torque of the motor when the controller controls the driving circuit in a first characteristic control manner; the load of the motor in the first load interval is smaller than the load in the second load interval.

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

In the second characteristic control mode, the torque of the output torque of the motor in the preset time range is larger than a preset threshold value, and the preset threshold value is set according to the characteristic of the motor and the current of the motor.

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

The load torque of the motor in the first load interval is smaller than the load torque of the motor in the second load interval.

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

When the controller controls the driving circuit in the first characteristic control mode, the motor outputs a first rotating speed;

the controller outputs a second rotating speed when controlling the driving circuit in the second characteristic control mode;

The motor outputs a third rotating speed when the controller controls the driving circuit in a third control mode; wherein the first rotational speed is greater than the third rotational speed, and the second rotational speed is greater than the third rotational speed.

5. The power tool of claim 1, wherein the power tool comprises a power tool,

The bus current of the motor increases with a first slope in a first torque interval and increases with a second slope in a second torque interval, wherein the first slope is greater than the second slope.

6. The power tool of claim 1, wherein the power tool comprises a power tool,

The controller controls the driving circuit in a second characteristic control mode to enable the motor to rotate with preset torque, and the output current of the power supply device is second output current;

When the controller controls the driving circuit in a third control mode to enable the motor to rotate with the preset torque, the output current of the power supply device is a third output current;

wherein the second output current is less than the third output current.

7. The power tool of claim 1, wherein the power tool comprises a power tool,

When the controller controls the driving circuit in the first characteristic control mode, the output power of the electric tool is first output power;

When the controller controls the driving circuit in the second characteristic control mode, the output power of the electric tool is second output power;

assuming that the controller controls the driving circuit in a third control mode, the output power of the electric tool is a third output power;

Wherein the first output power is greater than the third output power and the second output power is greater than the third output power.

8. The power tool of claim 1, wherein the power tool comprises a power tool,

The controller outputs a PWM signal to the driving circuit, a duty ratio of the PWM signal varying with a change in a position of the rotor.

9. The power tool of claim 1, wherein the power tool comprises a power tool,

The controller controls the driving circuit so that an input voltage of the motor approximately varies in a sine wave.

10. The power tool of claim 9, wherein the power tool comprises a power tool,

The motor is a three-phase motor, and three-phase input voltages of the motor are 120-degree phase angles.

11. The power tool of claim 1, wherein the power tool comprises a power tool,

The controller includes: and the first rotating speed ring is used for generating a target current of the motor according to the target rotating speed of the motor and the actual rotating speed of the motor.

12. The power tool of claim 11, wherein the power tool comprises a power tool,

The controller further includes:

the first current distribution unit is used for distributing a direct-axis target current and a quadrature-axis target current according to the target current of the motor generated by the first rotating speed ring;

A first current conversion unit for generating a direct-axis actual current and a quadrature-axis actual current according to an actual current of the motor and a position of a rotor of the motor;

the first current loop is used for generating a first voltage regulating quantity according to the direct-axis target current and the direct-axis actual current;

The second current loop is used for generating a second voltage regulating quantity according to the quadrature target current and the quadrature actual current;

a first voltage conversion unit configured to generate a first voltage control amount and a second voltage control amount according to the first voltage adjustment amount and the second voltage adjustment amount;

and the first control signal generation unit is used for generating a control signal according to the first voltage control quantity and the second voltage control quantity, and the control signal is used for controlling the driving circuit.

13. The power tool of claim 1, wherein the power tool comprises a power tool,

The controller includes:

And the second rotating speed ring is used for generating target torque of the motor according to the target rotating speed and the actual rotating speed of the motor.

14. The power tool of claim 13, wherein the power tool comprises a power tool,

The controller further includes:

A torque ring for generating a third voltage adjustment amount according to a target torque and an actual torque of the motor;

The magnetic chain ring is used for generating a fourth voltage adjustment quantity according to the target stator flux linkage and the actual stator flux linkage of the motor;

A second voltage conversion unit configured to generate a third voltage control amount and a fourth voltage control amount according to the third voltage adjustment amount and the fourth voltage adjustment amount;

And a second control signal generating unit for generating a control signal for controlling the driving circuit according to the third voltage control amount and the fourth voltage control amount.

15. The power tool of claim 1, wherein the power tool comprises a power tool,

The power tool further includes:

And the speed regulating mechanism is at least used for setting the target rotating speed of the motor.