A BLDC motor starting method, control device and electric tool with salient polarity

Abstract

The embodiment of the present invention provides a BLDC motor starting method with salient polarity, a control device and an electric tool. In the method, a control signal is first injected into the BLDC motor with salient polarity at each potential angle in sequence, wherein the interval between two adjacent potential angles is 30 degrees; then, the current signal of each potential angle of the motor when the voltage is injected is read; then, the initial potential angle of the BLDC motor with salient polarity is determined according to each current signal, and the initial potential angle is used to indicate the initial position state of the BLDC motor with salient polarity; finally, the BLDC motor with salient polarity is started according to the initial potential angle. In the method, the motor is started by injecting a control signal into the BLDC motor with salient polarity at each potential angle of 30 degrees, and determining the initial position of the BLDC motor with salient polarity according to the current of each potential angle. The starting method has a high starting probability and strong anti-interference performance.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of BLDC motors with salient polarity, and in particular to a BLDC motor starting method, a control device, and an electric tool with salient polarity. Background Art

[0002] As an important component of the traction system, the motor plays a pivotal role in the national economy. Its use has penetrated almost all walks of life and is an important guarantee for the normal operation of industry, agriculture, national defense construction and people's lives.

[0003] At present, when starting a brushless direct current (BLDC) motor, it is usually necessary to first determine the initial position of the motor, and then start the motor according to the initial position. However, the existing starting method has a low success probability and weak anti-interference performance. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a BLDC motor starting method, a control device and an electric tool with salient polarity, which have high starting probability and strong anti-interference ability.

[0005] In the first aspect, a technical solution adopted in an embodiment of the present invention is: to provide a method for starting a BLDC motor with salient polarity, which is applied to an electric tool, wherein the electric tool includes a BLDC motor with salient polarity, and the method includes: injecting control signals into the BLDC motor at each potential angle in sequence, wherein the interval between two adjacent potential angles is 30 degrees, and the duty cycle of the control signals injected at each potential angle is the same; reading the current signal of the BLDC motor at each potential angle when the control signal is applied; determining the initial potential angle of the BLDC motor according to each current signal, wherein the initial potential angle is used to indicate the initial position state of the BLDC motor; and starting the BLDC motor according to the initial potential angle.

[0006] In some embodiments, reading the current signal of the BLDC motor at each potential angle when the control signal is applied includes: reading the current signal of the busbar of the BLDC motor at each potential angle at a preset time point each time the control signal is injected.

[0007] In some embodiments, the electric tool includes an inverter unit, and the inverter unit includes a first-phase upper bridge, a first-phase lower bridge, a second-phase upper bridge, a second-phase lower bridge, a third-phase upper bridge and a third-phase lower bridge, and the control signal is injected into the BLDC motor at each potential angle in sequence, including: in a first cycle, injecting a first control signal into the third-phase upper bridge, and controlling the second-phase lower bridge to be turned on; in a second cycle, injecting a second control signal into the third-phase upper bridge, and controlling the first-phase lower bridge and the second-phase lower bridge to be turned on; in a third cycle, injecting a third control signal into the third-phase upper bridge, and controlling the first-phase lower bridge to be turned on; in a fourth cycle, injecting a fourth control signal into the second-phase upper bridge and the third-phase upper bridge, and controlling the first-phase lower bridge to be turned on; in a fifth cycle, injecting a fifth control signal into the second-phase upper bridge, and controlling the first-phase lower bridge to be turned on; In the sixth cycle, the sixth control signal is injected into the second phase upper bridge, and the first phase lower bridge and the third phase lower bridge are controlled to be turned on; in the seventh cycle, the seventh control signal is injected into the second phase upper bridge, and the third phase lower bridge is controlled to be turned on; in the eighth cycle, the eighth control signal is injected into the first phase upper bridge and the second phase upper bridge, and the third phase lower bridge is controlled to be turned on; in the ninth cycle, the ninth control signal is injected into the first phase upper bridge, and the third phase lower bridge is controlled to be turned on; in the tenth cycle, the tenth control signal is injected into the first phase upper bridge, and the second phase lower bridge and the third phase lower bridge are controlled to be turned on; in the eleventh cycle, the eleventh control signal is injected into the first phase upper bridge, and the second phase lower bridge is controlled to be turned on; in the twelfth cycle, the twelfth control signal is injected into the third phase upper bridge and the first phase upper bridge, and the second phase lower bridge is controlled to be turned on.

[0008] In some embodiments, the reading of the current signals of the BLDC motor at each potential angle when the control signal is given, and determining the initial potential angle of the BLDC motor according to each of the current signals, includes: reading the first current, the second current, the third current, the fourth current, the fifth current, the sixth current, the seventh current, the eighth current, the ninth current, the tenth current, the eleventh current, and the twelfth current of the bus at preset time points of the first cycle, the second cycle, the third cycle, the fourth cycle, the fifth cycle, the sixth cycle, the seventh cycle, the eighth cycle, the ninth cycle, the tenth cycle, the eleventh cycle, and the twelfth cycle respectively; taking the maximum current value of the first current, the third current, the fifth current, the seventh current, the ninth current, and the eleventh current as a first value, and the second maximum current value as a second value; taking the maximum current value of the second current, the fourth current, the sixth current, the eighth current, the tenth current, and the twelfth current as a third value; and obtaining the initial potential angle of the BLDC motor according to the first value, the second value, and the third value.

[0009] In some embodiments, the initial potential angle of the BLDC motor is obtained according to the first value, the second value and the third value, including: if the first value is the first current, the second value is the third current, and the third value is the second current, then the initial potential angle of the BLDC motor is 0°-60°; if the first value is the third current, the second value is the fifth current, and the third value is the fourth current, then the initial potential angle of the BLDC motor is 60°-120°; if the first value is the fifth current, the second value is the seventh current, and the third value is the sixth current, then the BLDC motor The initial potential angle of the LDC motor is 120°-180°; if the first value is the seventh current, the second value is the ninth current, and the third value is the eighth current, the initial potential angle of the BLDC motor is 180°-240°; if the first value is the ninth current, the second value is the eleventh current, and the third value is the tenth current, the initial potential angle of the BLDC motor is 240°-300°; if the first value is the eleventh current, the second value is the first current, and the third value is the twelfth current, the initial potential angle of the BLDC motor is 300°-360°.

[0010] In some embodiments, starting the BLDC motor according to the initial potential angle includes: controlling the BLDC motor to operate according to the initial potential angle; obtaining the reaction electromotive force of the BLDC motor, and if the correct reaction electromotive force is obtained, controlling the BLDC motor to switch phases according to the reaction electromotive force; obtaining the reaction electromotive force of the BLDC motor again after the BLDC motor switches phases; when the reaction electromotive force of the BLDC motor is obtained M times in succession, causing the BLDC motor to enter closed-loop control, wherein M is a positive integer greater than or equal to 2.

[0011] In some embodiments, starting the BLDC motor according to the initial potential angle also includes: starting a timer after the BLDC motor starts working or after the BLDC motor changes phases; when the timing time of the timer is reached, if the correct reaction electromotive force is not obtained, forcing the BLDC motor to change phases; when the number of forced commutation of the BLDC motor reaches a preset number threshold, determining that the BLDC motor has failed to start; when the number of forced commutation of the BLDC motor does not reach the preset number threshold, obtaining the reaction electromotive force of the BLDC motor; if the reaction electromotive force is correct, controlling the BLDC motor to change phases according to the reaction electromotive force, and re-obtaining the reaction electromotive force of the BLDC motor.

[0012] In a second aspect, an embodiment of the present invention further provides a control device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the BLDC motor starting method with salient polarity as described in any one of the first aspects.

[0013] In the third aspect, an embodiment of the present invention further provides an electric tool, comprising: a BLDC motor with salient polarity, an inverter unit and a control device as described in the second aspect; the inverter unit is connected to an external power supply via a bus, the inverter unit and the BLDC motor are connected in three phases, and the control device is respectively connected to the inverter unit and the BLDC motor.

[0014] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the salient polarity BLDC motor starting method as described in any one of the first aspects.

[0015] In a fifth aspect, an embodiment of the present invention further provides a computer program product, wherein the computer program product comprises a computer program stored on a computer-readable storage medium, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer executes the method described in the first aspect above.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Different from the prior art, the embodiments of the present invention provide a BLDC motor starting method, a control device and an electric tool with salient polarity, in which a control signal is first injected into the BLDC motor with salient polarity at each potential angle in sequence, wherein the interval between two adjacent potential angles is 30 degrees; then, the current signal of the BLDC motor with salient polarity at each potential angle when the control signal is applied is read; then, the initial potential angle of the BLDC motor with salient polarity is determined according to each current signal, and the initial potential angle is used to indicate the initial position state of the BLDC motor with salient polarity; finally, the BLDC motor with salient polarity is started according to the initial potential angle. In this method, a control signal is injected into the BLDC motor with salient polarity at each potential angle of 30 degrees, 12 control signals with the same duty cycle are injected, and the current signal at each control signal is read, and then the initial position of the BLDC motor is determined according to the 12 current signals, thereby improving the accuracy of the initial position identification, starting the motor on the basis of accurately identifying the initial position, and improving the success rate of the motor start. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements / modules and steps with the same reference numerals in the drawings are represented as similar elements / modules and steps. Unless otherwise specified, the figures in the drawings do not constitute proportional limitations.

[0018] Figure 1 is a schematic diagram of one application environment of a BLDC motor starting method with salient polarity provided by an embodiment of the present invention;

[0019] Figure 2 is a structural schematic diagram of an electric tool provided by an embodiment of the present invention;

[0020] Figure 3 is a schematic structural diagram of another electric tool provided by an embodiment of the present invention;

[0021] Figure 4 is a structural schematic diagram of another electric tool provided by an embodiment of the present invention;

[0022] Figure 5 is a structural schematic diagram of a control device provided by an embodiment of the present invention;

[0023] Figure 6 1 is a flow chart of a method for starting a BLDC motor with salient polarity provided by an embodiment of the present invention;

[0024] Figure 7 yes Figure 6 Schematic diagram of the process of step S120;

[0025] Figure 8 yes Figure 6 Schematic diagram of the process of step S110;

[0026] Fig. 9 It is a partial flow chart of a method for starting a BLDC motor with salient polarity provided by an embodiment of the present invention;

[0027] Fig.10 yes Fig. 9 Schematic diagram of the process of step S123;

[0028] Fig.11 yes Figure 6 A schematic diagram of a flow chart of step S140;

[0029] Fig.12 yes Figure 6 Another flowchart diagram of step S140 in FIG. DETAILED DESCRIPTION

[0030] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0031] For ease of understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those generally understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not used to limit the present application. The term "and / or" used in this specification includes any and all combinations of one or more related listed items.

[0032] It should be noted that, if there is no conflict, the various features in the embodiments of the present invention can be combined with each other, and all are within the scope of protection of this application. In addition, although the functional module division is performed in the device schematic, in some cases, the module division can be different from that in the device. In addition, the words "first", "second", etc. used in this article do not limit the data and execution order, but only distinguish the same items or similar items with basically the same functions and effects.

[0033] At present, the commonly used method for starting the sensorless BLDC motor is to adopt a three-step starting method. In this three-step starting method: first, the two fixed phases of the motor are energized, and the motor stops at a fixed position, so that the motor can be positioned; then, the order of phase switching is set according to the set time, so as to drive the motor to run, and observe the reaction electromotive force of the motor; finally, after observing the reaction electromotive force of the motor, switch to using the reaction electromotive force to drive the motor, and switch from open loop to closed loop control. However, this positioning starting method has a small starting torque. In the case of fans and other conditions where the starting torque is not required, the motor can be started. When the motor is loaded, the probability of successful starting of the motor is not high.

[0034] Figure 1 A schematic diagram of one of the application environments of the salient polarity BLDC motor starting method provided in an embodiment of the present invention, wherein the application environment includes: an electric tool 100 and an external power supply 200, wherein the electric tool 100 includes a salient polarity BLDC motor 10 and an inverter unit 20. The input end of the inverter unit 20 is connected to the external power supply 200 via a bus, and the output end of the inverter unit 20 is connected to the three-phase salient polarity BLDC motor 10. The electric tool 100 can be a beauty instrument, a refrigerator, or any other device including a salient polarity BLDC motor.

[0035] It should be noted that the BLDC motor 10 and the BLDC motor with salient polarity referred to in the present invention are BLDC motors with strong salient polarity, that is, the position of such BLDC motors when stopped is usually fixed, and the stopped position is usually a multiple of 30° in electrical angle. Therefore, when starting such BLDC motors, it is often necessary to locate the initial position of the BLDC motor so that the motor can be started according to the initial position of the BLDC motor with salient polarity, thereby controlling the normal operation of the motor.

[0036] In order to improve the positioning accuracy of the BLDC motor with salient polarity so that the BLDC motor with salient polarity can quickly enter high-speed operation, the embodiments of the present invention provide a BLDC motor starting method, a control device and a power tool with salient polarity, by injecting a control signal into the BLDC motor with salient polarity at every potential angle of 30 degrees, and determining the initial position of the BLDC motor with salient polarity according to the current at each potential angle, thereby starting the motor according to the initial position of the BLDC motor with salient polarity. This positioning starting method has a high starting probability and strong anti-interference ability.

[0037] It should be noted that the salient polarity BLDC motor starting method provided in the embodiment of the present invention is generally performed by the above-mentioned power tool, and the control device provided in the embodiment of the present invention is generally arranged in the power tool. Specifically, the embodiment of the present invention is further explained below in conjunction with the accompanying drawings.

[0038] See also Figure 2 , Figure 2 is a schematic diagram of the structure of an electric tool 100 provided in an embodiment of the present invention. Figure 2 As shown, the electric tool 100 includes: a BLDC motor 10 with salient polarity, an inverter unit 20 and a control device 30. The inverter unit 20 is connected to an external power supply 200 via a busbar, the inverter unit 20 and the BLDC motor 10 with salient polarity are three-phase connected, and the control device 30 is respectively connected to the inverter unit 20 and the BLDC motor 10 with salient polarity.

[0039] In some of these examples, see Figure 3The inverter unit 20 includes a first-phase upper bridge Q1, a first-phase lower bridge Q2, a second-phase upper bridge Q3, a second-phase lower bridge Q4, a third-phase upper bridge Q5 and a third-phase lower bridge Q6. The first end of the first-phase upper bridge Q1, the first end of the second-phase upper bridge Q3 and the first end of the third-phase upper bridge Q5 are connected to the bus positive electrode VCC; the second end of the first-phase upper bridge Q1 is connected to the first end of the first-phase lower bridge Q2, the second end of the second-phase upper bridge Q3 is connected to the first end of the second-phase lower bridge Q4, the second end of the third-phase upper bridge Q5 is connected to the first end of the third-phase lower bridge Q6, the common connection end of the first-phase upper bridge Q1 and the first-phase lower bridge Q2, the common connection end of the second-phase upper bridge Q3 and the second-phase lower bridge Q4, and the third-phase upper bridge Q5 and the third-phase lower bridge Q6. The common connection end is respectively connected to the three phases of the BLDC motor 10 with salient polarity; the second end of the first phase lower bridge Q2, the second end of the second phase lower bridge Q4 and the second end of the third phase lower bridge Q6 are commonly connected to the ground; the control end of the first phase upper bridge Q1, the control end of the first phase upper bridge Q1 of the first phase lower bridge Q2, the control end of the first phase upper bridge Q1 of the second phase upper bridge Q3, the control end of the first phase upper bridge Q1 of the second phase lower bridge Q4, the control end of the first phase upper bridge Q1 of the third phase upper bridge Q5 and the control end of the first phase upper bridge Q1 of the third phase lower bridge Q6 are respectively connected to the control device 30. Specifically, the first phase, the second phase and the third phase can be U phase, V phase and W phase, which are respectively connected to the three-phase winding of the BLDC motor 10 with salient polarity.

[0040] In some of these examples, see Figure 4 , the electric tool 100 also includes a current acquisition unit 40, the input end of the current acquisition unit 40 is connected to the negative bus, and the output end of the current acquisition unit 40 is connected to the control device 30. Specifically, the input end of the current acquisition unit is connected to the common connection end of the second end of the first phase lower bridge, the second end of the second phase lower bridge and the second end of the third phase lower bridge, and the output end of the current acquisition unit is connected to the control device. The current acquisition unit is used to collect the current signal of each potential angle of the BLDC motor when the control signal is received, and send the current signal to the control device, so that the control device reads the current signal of each potential angle of the BLDC motor when the control signal is received. For example, the current acquisition unit can be an operational amplifier circuit, or any other suitable circuit structure in the prior art that can be used to collect the current signal of each potential angle of the BLDC motor when the control signal is received, which is not limited here.

[0041] In some of these embodiments, please continue to see Figure 4The electric tool 100 also includes a reaction electromotive force acquisition unit 50, the input ends of the reaction electromotive force acquisition unit 50 are respectively connected to the three-phase windings of the BLDC motor 10 with salient polarity, and the output ends of the reaction electromotive force acquisition unit 50 are connected to the control device 30. The reaction electromotive force acquisition unit is used to collect the reaction electromotive force of the BLDC motor 10 with salient polarity after the BLDC motor 10 with salient polarity starts to work, and send the reaction electromotive force to the control device 30, so that the control device 30 reads the reaction electromotive force of the BLDC motor 10 with salient polarity.

[0042] Specifically, the reaction electromotive force acquisition unit can be three voltage-dividing circuits composed of voltage-dividing resistors, the first end of each voltage-dividing circuit is connected to a phase winding of the BLDC motor, and the second end of each voltage-dividing circuit is connected to the control device. It can be understood that the reaction electromotive force acquisition unit can also be any other suitable circuit structure in the prior art that can be used to collect the reaction electromotive force of a BLDC motor with salient polarity, which is not limited here.

[0043] In some embodiments, the control device can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a single-chip microcomputer, an ARM (Acorn RICS Machine) or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or any combination of these components. In addition, the control device can also be any conventional processor, controller, microcontroller or state machine. The control device can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a DSP and / or any other such configuration.

[0044] See also Figure 5 , Figure 5 1 is a schematic diagram of a control device provided by an embodiment of the present invention. The control device includes at least one processor and a memory connected to the at least one processor in communication, wherein: Figure 5 A processor is taken as an example.

[0045] The memory 32 stores instructions that can be executed by the at least one processor 31. The instructions are executed by the at least one processor 31 so that the at least one processor 31 can perform the following Figures 2 to 6 The processor 31 and the memory 32 may be connected via a bus or other means. Figure 5 The control device may be a bus connection. Figure 2 Controls shown.

[0046] The memory 32 is a non-volatile computer-readable storage medium that can be used to store non-volatile software programs, non-volatile computer executable programs and modules, such as program instructions / modules corresponding to the salient polarity BLDC motor starting method in the embodiment of the present application. The processor 31 executes various functional applications and data processing of the control device by running the non-volatile software programs, instructions and modules stored in the memory 32, that is, the salient polarity BLDC motor starting method in the following method embodiment is implemented.

[0047] The memory 32 may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required by at least one function; the data storage area may store data created according to the use of the control device, etc. In addition, the memory 32 may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the memory 32 may optionally include a memory remotely arranged relative to the processor 31, and these remote memories may be connected to the control device via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0048] The one or more modules are stored in the memory 32, and when executed by the one or more processors 31, execute the BLDC motor starting method with salient polarity in any of the following method embodiments, for example, execute the following description Figures 6 to 12 method steps.

[0049] The above-mentioned product can execute the method provided in the embodiment of the present application, and has the functional modules and beneficial effects corresponding to the execution method. For technical details not fully described in this embodiment, please refer to the method provided in the embodiment of the present application.

[0050] The following is a detailed description of a BLDC motor starting method with salient polarity provided by an embodiment of the present invention in conjunction with the accompanying drawings. Figure 6 , which shows a schematic flow chart of a method for starting a BLDC motor with salient polarity provided by an embodiment of the present invention, wherein the method for starting a BLDC motor with salient polarity can be Figure 2-Figure 5 The control device in the embodiment of the present invention is executed, and the method includes but is not limited to the following steps:

[0051] Step S110: injecting control signals into the BLDC motor at each potential angle in sequence, wherein the interval between two adjacent potential angles is 30 degrees;

[0052] Since the salient polarity of the BLDC motor is strong, its initial position is usually a multiple of 30° in electrical angle. In order to determine the initial position of the salient polarity BLDC motor, after the BLDC motor triggers the starting condition, a control signal is injected into the BLDC motor when the motor is at a potential angle of 30 degrees. Specifically, after the BLDC motor triggers the starting condition, a control signal is injected into the BLDC motor to rotate the potential angle of the BLDC motor from the initial potential angle to the next potential angle. When the potential angle of the BLDC motor rotates to the next potential angle, another control signal is injected into the BLDC motor, and this cycle is repeated until 12 control signals are injected into the BLDC motor cycle.

[0053] In this embodiment, the duty cycle of the control signal injected at each potential angle is the same.

[0054] Step S120: reading the current signal of each potential angle of the BLDC motor when the control signal is applied;

[0055] Specifically, the current signal of the potential angle of the BLDC motor is obtained through the current acquisition unit each time the control signal is injected.

[0056] In some of these examples, see Figure 7 , the step S120 comprises:

[0057] Step S121: reading the current signal of the busbar of the BLDC motor at each potential angle at a preset time point of each injection of the control signal;

[0058] Specifically, the preset time point is a fixed time point of each injection cycle, and the injection cycle is the time for injecting a control signal. Then, when 12 control signals are injected into the BLDC motor cycle, the current signal of the bus of the BLDC motor is read at a fixed time point in each injection cycle, thereby obtaining 12 current signals. By sampling at a fixed time point in each injection cycle, it can be ensured that the current signals of each bus obtained are comparable. The fixed time point can be a time point near the end of each injection cycle, such as a time point several μs in advance when each injection cycle is about to end. In this way, it can be ensured that the collected current signal is the bus current signal of the potential angle when the control signal is about to be fully injected, which is beneficial to improve the accuracy of the current signal.

[0059] Step S130: determining an initial potential angle of the BLDC motor according to each of the current signals, wherein the initial potential angle is used to indicate an initial position state of the BLDC motor;

[0060] By injecting a control signal into the BLDC motor at every 30-degree potential angle, 12 current signals with 30-degree potential angles can be obtained. Since the magnitudes of the 12 current signals have a certain relationship with the initial potential angle of the BLDC motor, the initial potential angle of the BLDC motor can be obtained through the magnitudes of these 12 current signals.

[0061] Step S140: starting the BLDC motor according to the initial potential angle.

[0062] Specifically, after the initial potential angle of the BLDC motor is obtained, the BLDC motor can be controlled to start according to the initial potential angle of the BLDC motor, thereby achieving the BLDC motor start-up.

[0063] In the BLDC motor starting method provided in an embodiment of the present invention, a control signal is injected into the BLDC motor at a potential angle interval of 30 degrees, and the initial position of the BLDC motor is determined according to the current at each potential angle, that is, a control signal is injected into the BLDC motor with a salient polarity at a potential angle interval of 30 degrees, 12 control signals with the same duty cycle are injected, and the current signal of each control signal is read, and then the initial position of the BLDC motor is determined according to the 12 current signals, thereby improving the accuracy of initial position identification, starting the motor on the basis of accurate identification of the initial position, and improving the success rate of motor starting.

[0064] In some embodiments, the electric tool includes an inverter unit, and the inverter unit includes a first-phase upper bridge, a first-phase lower bridge, a second-phase upper bridge, a second-phase lower bridge, a third-phase upper bridge, and a third-phase lower bridge. The connection relationship of each bridge in the inverter unit can refer to the aforementioned connection method, which will not be repeated here. Please refer to Figure 8 , the step S110 comprises:

[0065] Step S111: In the first cycle, inject a first control signal into the third phase upper bridge, and control the second phase lower bridge to be turned on;

[0066] Step S112: In the second cycle, injecting a second control signal into the third phase upper bridge, and controlling the first phase lower bridge and the second phase lower bridge to be turned on;

[0067] Step S113: In the third cycle, inject a third control signal into the third phase upper bridge, and control the first phase lower bridge to be turned on;

[0068] Step S114: In the fourth cycle, inject a fourth control signal into the second phase upper bridge and the third phase upper bridge, and control the first phase lower bridge to be turned on;

[0069] Step S115: In the fifth cycle, injecting a fifth control signal into the second phase upper bridge, and controlling the first phase lower bridge to be turned on;

[0070] Step S116: In the sixth cycle, injecting a sixth control signal into the second phase upper bridge, and controlling the first phase lower bridge and the third phase lower bridge to be turned on;

[0071] Step S117: In the seventh cycle, injecting a seventh control signal into the second phase upper bridge, and controlling the third phase lower bridge to be turned on;

[0072] Step S118: In the eighth cycle, injecting an eighth control signal into the first phase upper bridge and the second phase upper bridge, and controlling the third phase lower bridge to be turned on;

[0073] Step S119: In the ninth cycle, injecting a ninth control signal into the first phase upper bridge, and controlling the third phase lower bridge to be turned on;

[0074] Step S1110: In the tenth cycle, inject the tenth control signal into the first phase upper bridge, and control the second phase lower bridge and the third phase lower bridge to be turned on;

[0075] Step S1111: In the eleventh cycle, injecting the eleventh control signal into the first phase upper bridge, and controlling the second phase lower bridge to be turned on;

[0076] Step S1112: In the twelfth cycle, inject a twelfth control signal into the third phase upper bridge and the first phase upper bridge, and control the second phase lower bridge to be turned on.

[0077] Specifically, the first phase upper bridge is the U phase upper bridge, the first phase lower bridge is the U phase lower bridge, the second phase upper bridge is the V phase upper bridge, the second phase lower bridge is the V phase lower bridge, the third phase upper bridge is the W phase upper bridge, the third phase lower bridge is the W phase lower bridge, and each control signal is a PWM signal. Then, when the BLDC motor triggers the starting condition, the electrical angle at the start-up moment of the BLDC motor is the initial potential angle θ; then, in the first cycle, the first PWM signal is injected into the W phase upper bridge, and the V phase lower bridge is controlled to be turned on, so that the BLDC motor rotates 30°, at this time, the electrical angle of the BLDC motor is θ+30°; in the second cycle, the second PWM signal is injected into the W phase upper bridge, and the U phase lower bridge and the V phase lower bridge are controlled to be turned on, so that the BLDC motor rotates another 30°, at this time, the electrical angle of the BLDC motor is θ+60°; in the third cycle, The third PWM signal is injected into the W phase upper bridge, and the U phase lower bridge is controlled to be turned on, so that the BLDC motor rotates another 30°. At this time, the electrical angle of the BLDC motor is θ+90°; in the fourth cycle, the fourth PWM signal is injected into the V phase upper bridge and the W phase upper bridge, and the U phase lower bridge is controlled to be turned on, so that the BLDC motor rotates another 30°. At this time, the electrical angle of the BLDC motor is θ+120°; in the fifth cycle, the fifth PWM signal is injected into the V phase upper bridge, and the U phase lower bridge is controlled to be turned on, so that the BLDC motor rotates another 30°. At this time, the electrical angle of the BLDC motor is θ

[0078] +150°; in the sixth cycle, the sixth PWM signal is injected into the upper bridge of the V phase, and the lower bridge of the U phase and the lower bridge of the W phase are controlled to be turned on, so that the BLDC motor rotates another 30°. At this time, the electrical angle of the BLDC motor is θ+180°; in the seventh cycle, the seventh PWM signal is injected into the upper bridge of the V phase, and the lower bridge of the W phase is controlled to be turned on, so that the BLDC motor rotates another 30°. At this time, the electrical angle of the BLDC motor is θ+210°; in the eighth cycle, the eighth PWM signal is injected into the upper bridge of the U phase and the upper bridge of the V phase, and the lower bridge of the W phase is controlled to be turned on, so that the BLDC motor rotates another 30°. At this time, the electrical angle of the BLDC motor is θ+240°; in the ninth cycle, the ninth PWM signal is injected into the upper bridge of the U phase, and the lower bridge of the W phase is controlled to be turned on, Make the BLDC motor rotate another 30°, at this time, the electrical angle of the BLDC motor is θ+270°; in the tenth cycle, inject the tenth PWM signal to the U-phase upper bridge, and control the V-phase lower bridge and the W-phase lower bridge to be turned on, so that the BLDC motor rotates another 30°, at this time, the electrical angle of the BLDC motor is θ+300°; in the eleventh cycle, inject the eleventh PWM signal to the U-phase upper bridge, and control the V-phase lower bridge to be turned on, so that the BLDC motor rotates another 30°, at this time, the electrical angle of the BLDC motor is θ+330°; in the twelfth cycle, inject the twelfth PWM signal to the W-phase upper bridge and the U-phase upper bridge, and control the V-phase lower bridge to be turned on, so that the BLDC motor rotates another 30°, at this time, the electrical angle of the BLDC motor is θ+360°.

[0079] By using the above-mentioned method of periodically injecting PWM signals, it can be ensured that the BLDC motor is injected with control signals at a potential angle interval of 30 degrees from the initial potential angle.

[0080] In some of these examples, see Fig. 9 , the step of reading the current signal of each potential angle of the BLDC motor when the control signal is applied, and determining the initial potential angle of the BLDC motor according to each current signal, comprises:

[0081] Step S121: reading a first current, a second current, a third current, a fourth current, a fifth current, a sixth current, a seventh current, an eighth current, a ninth current, a tenth current, an eleventh current and a twelfth current of the bus at preset time points of the first cycle, the second cycle, the third cycle, the fourth cycle, the fifth cycle, the sixth cycle, the seventh cycle, the eighth cycle, the ninth cycle, the tenth cycle, the eleventh cycle and the twelfth cycle respectively;

[0082] Step S122: taking the maximum current value among the first current, the third current, the fifth current, the seventh current, the ninth current and the eleventh current as a first value, and the second maximum current value as a second value; taking the maximum current value among the second current, the fourth current, the sixth current, the eighth current, the tenth current and the twelfth current as a third value;

[0083] Step S123: obtaining an initial potential angle of the BLDC motor according to the first value, the second value and the third value.

[0084] Specifically, the current is obtained at a fixed time point in each injection cycle, so 12 current signals can be obtained. Then, the first current, the third current, the fifth current, the seventh current, the ninth current and the eleventh current are placed in the first array, and the second current, the fourth current, the sixth current, the eighth current, the tenth current and the twelfth current are placed in the second array; then, according to the magnitude of each current, the largest current value in the first array is obtained as the first value, the second largest current value in the first array is obtained as the second value, and the largest current value in the second array is obtained as the third value; since the initial position in the BLDC motor has a certain corresponding relationship with the first value, the second value and the third value, the initial potential angle of the BLDC motor can be obtained according to the first value, the second value and the third value.

[0085] Specifically, in some of the embodiments, please refer to Fig.10 , the step S123 comprises:

[0086] Step S1231: if the first value is the first current, the second value is the third current, and the third value is the second current, then the initial potential angle of the BLDC motor is 0°-60°;

[0087] Step S1232: if the first value is the third current, the second value is the fifth current, and the third value is the fourth current, then the initial potential angle of the BLDC motor is 60°-120°;

[0088] Step S1233: if the first value is the fifth current, the second value is the seventh current, and the third value is the sixth current, then the initial potential angle of the BLDC motor is 120°-180°;

[0089] Step S1234: if the first value is the seventh current, the second value is the ninth current, and the third value is the eighth current, then the initial potential angle of the BLDC motor is 180°-240°;

[0090] Step S1235: if the first value is the ninth current, the second value is the eleventh current, and the third value is the tenth current, then the initial potential angle of the BLDC motor is 240°-300°;

[0091] Step S1236: If the first value is the eleventh current, the second value is the first current, and the third value is the twelfth current, then the initial potential angle of the BLDC motor is 300°-360°.

[0092] For example, the first value is the current value of the first current, the second value is the current value of the third current, and the third value is the current value of the second current, then it can be determined that the initial potential angle of the BLDC motor is 0°-60°, and so on. According to the current serial numbers corresponding to the first value, the second value and the third value, the initial potential angle of the BLDC motor can be obtained.

[0093] In some of these examples, see Fig.11 , the step S140 comprises:

[0094] Step S141: controlling the BLDC motor to operate according to the initial potential angle;

[0095] Step S142: obtaining the reaction electromotive force of the BLDC motor, and if the correct reaction electromotive force is obtained, controlling the commutation of the BLDC motor according to the reaction electromotive force;

[0096] Step S143: acquiring the reaction electromotive force of the BLDC motor again after the BLDC motor is commutated;

[0097] Step S144: when the correct reaction electromotive force is obtained M times in succession, the BLDC motor is put into closed-loop control, wherein M is a positive integer greater than or equal to 2.

[0098] Specifically, after the initial potential angle of the BLDC motor is obtained according to the above steps, the BLDC motor can be controlled to work according to the initial potential angle; then, the reaction electromotive force of the BLDC motor is obtained through the reaction electromotive force acquisition unit and combined with the enabled majority filter algorithm; if the correct reaction electromotive force is obtained, the BLDC motor is controlled to change phase according to the reaction electromotive force; after the BLDC motor changes phase, the reaction electromotive force is collected again through the reaction electromotive force acquisition unit, and the reaction electromotive force of the BLDC motor is obtained by enabling the majority filter algorithm, and it is continued to be judged whether the reaction electromotive force is correct. If it is correct, the BLDC motor is continued to be controlled to change phase according to the reaction electromotive force, and this cycle is repeated until the correct reaction electromotive force is obtained twice in a row, and the BLDC motor is controlled to enter the closed-loop control operation. In this way, it is helpful to solve the problem of position commutation error and software execution logic of the BLDC motor, and improve the safety and reliability of the BLDC motor when running at high speed. In practical applications, the number of M can be set freely, and it is not necessary to stick to the limitations in this embodiment.

[0099] In some of these examples, see Fig.12 , the step S140 further includes:

[0100] Step S145: after the BLDC motor starts to work or after the BLDC motor changes phase, start the timer;

[0101] Step S146: When the timing time of the timer is reached, if the correct reaction electromotive force is not obtained, forcing the BLDC motor to commutate;

[0102] Step S147: when the number of forced commutation of the BLDC motor reaches a preset number threshold, it is determined that the BLDC motor fails to start;

[0103] Step S148: when the number of forced commutation of the BLDC motor does not reach a preset number threshold, obtaining a reaction electromotive force of the BLDC motor;

[0104] Step S149: If the reaction electromotive force is correct, controlling the commutation of the BLDC motor according to the reaction electromotive force, and reacquiring the reaction electromotive force of the BLDC motor.

[0105] Specifically, after the initial potential angle of the BLDC motor is obtained according to the above steps, the BLDC motor can be controlled to work and the interrupt time of the timer can be set according to the initial potential angle; then, the reaction electromotive force of the BLDC motor is obtained through the reaction electromotive force acquisition unit and combined with the enabling majority filter algorithm.

[0106] If the correct reaction electromotive force is obtained, the BLDC motor is controlled to perform phase change according to the reaction electromotive force, and the timer is re-driven to obtain the reaction electromotive force again after phase change. If the correct reaction electromotive force has not been obtained when the timer interrupt time is reached, the BLDC motor is controlled to perform forced phase change and the timer is re-driven; at this time, if the number of forced phase changes is greater than the set threshold number, it is determined that the BLDC motor fails to start, and if the number of forced phase changes is less than or equal to the set threshold number, the reaction electromotive force of the BLDC motor is obtained again.

[0107] Next, continue to check whether the reaction electromotive force obtained after commutation is correct. If the correct reaction electromotive force is obtained, continue to control the BLDC motor for commutation according to the reaction electromotive force, re-drive the timer, and re-obtain the reaction electromotive force after commutation. If the correct reaction electromotive force has not been obtained when the timer interrupt time is reached, control the BLDC motor for forced commutation and re-drive the timer. At this time, if the number of forced commutations is greater than the set threshold number, it is determined that the BLDC motor has failed to start. If the number of forced commutations is less than or equal to the set threshold number, the reaction electromotive force of the BLDC motor is re-obtained.

[0108] This cycle is repeated until the correct reaction electromotive force is obtained M times in succession, and then the BLDC motor is controlled to enter a closed-loop control mode, or until it is determined that the BLDC motor fails to start.

[0109] It can be seen that in the motor starting method provided by the present invention, the initial position of the motor is determined by injecting pulses and driving the motor, and the timer is started. When there is a correct reaction electromotive force signal, the reaction electromotive force commutation is used. When there is no correct reaction electromotive force signal, the timer is used for forced commutation. Generally, 2-3 pulses of forced commutation can detect the correct reaction electromotive force signal. By means of timer and forced commutation, the position commutation error of the BLDC motor with salient polarity is further solved, and the safety and reliability of the BLDC motor with salient polarity during high-speed operation is improved.

[0110] The present application also provides a non-volatile computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are executed by one or more processors, for example, to execute the above-described Figures 6 to 12 method steps.

[0111] The present application also provides a computer program product, including a computer program stored on a non-volatile computer-readable storage medium, wherein the computer program includes program instructions, and when the program instructions are executed by a computer, the computer executes the BLDC motor starting method with salient polarity in any of the above method embodiments, for example, executing the above described Figures 6 to 12 method steps.

[0112] The embodiment of the present invention provides a BLDC motor starting method with salient polarity, a control device and an electric tool. In the method, a control signal is first injected into the BLDC motor with salient polarity at each potential angle in sequence, wherein the interval between two adjacent potential angles is 30 degrees; then, the current signal of the BLDC motor with salient polarity at each potential angle when the control signal is applied is read; then, the initial potential angle of the BLDC motor with salient polarity is determined according to each current signal, and the initial potential angle is used to indicate the initial position state of the BLDC motor with salient polarity; finally, the BLDC motor with salient polarity is started according to the initial potential angle. In the method, the motor is started by injecting a control signal into the BLDC motor with salient polarity at each potential angle of 30 degrees, and determining the initial position of the BLDC motor with salient polarity according to the current at each potential angle. The starting method has a high starting probability and strong anti-interference performance.

[0113] It should be noted that the device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0114] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a general hardware platform, and of course, by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the relevant technology can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions to use at least one computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiment.

[0115] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for starting a BLDC motor with salient polarity, applied to an electric tool, wherein the electric tool comprises a BLDC motor with salient polarity, characterized in that: The method comprises: Injecting control signals into the BLDC motor at each potential angle in sequence, wherein the interval between two adjacent potential angles is 30 degrees, and the duty cycle of the control signals injected at each potential angle is the same; Reading the current signal of the busbar of each potential angle of the BLDC motor when the control signal is applied; Determining an initial potential angle of the BLDC motor according to each of the current signals, wherein the initial potential angle is used to indicate an initial position state of the BLDC motor; Starting the BLDC motor according to the initial potential angle; The step of reading the current signal of the busbar of each potential angle of the BLDC motor when the control signal is applied, and determining the initial potential angle of the BLDC motor according to each current signal, comprises: Respectively at preset time points of the first cycle, the second cycle, the third cycle, the fourth cycle, the fifth cycle, the sixth cycle, the seventh cycle, the eighth cycle, the ninth cycle, the tenth cycle, the eleventh cycle, and the twelfth cycle, read the first current, the second current, the third current, the fourth current, the fifth current, the sixth current, the seventh current, the eighth current, the ninth current, the tenth current, the eleventh current, and the twelfth current of the bus; take the maximum current value of the first current, the third current, the fifth current, the seventh current, the ninth current, and the eleventh current as the first value, and the second maximum current value as the second value; take the maximum current value of the second current, the fourth current, the sixth current, the eighth current, the tenth current, and the twelfth current as the third value; and obtain the initial potential angle of the BLDC motor according to the first value, the second value, and the third value; The obtaining the initial potential angle of the BLDC motor according to the first value, the second value and the third value includes: If the first value is the first current, the second value is the third current, and the third value is the second current, then the initial potential angle of the BLDC motor is 0°-60°; If the first value is the third current, the second value is the fifth current, and the third value is the fourth current, then the initial potential angle of the BLDC motor is 60°-120°; If the first value is the fifth current, the second value is the seventh current, and the third value is the sixth current, then the initial potential angle of the BLDC motor is 120°-180°; If the first value is the seventh current, the second value is the ninth current, and the third value is the eighth current, then the initial potential angle of the BLDC motor is 180°-240°; If the first value is the ninth current, the second value is the eleventh current, and the third value is the tenth current, then the initial potential angle of the BLDC motor is 240°-300°; If the first value is the eleventh current, the second value is the first current, and the third value is the twelfth current, the initial potential angle of the BLDC motor is 300°-360°.

2. The method for starting a BLDC motor with salient polarity according to claim 1, characterized in that: The step of reading the current signal of the busbar of each potential angle of the BLDC motor at the time of the control signal comprises: At a preset time point each time the control signal is injected, a current signal of the busbar of the BLDC motor at each potential angle is read.

3. The method for starting a BLDC motor with salient polarity according to claim 2, characterized in that: The electric tool includes an inverter unit, the inverter unit includes a first-phase upper bridge, a first-phase lower bridge, a second-phase upper bridge, a second-phase lower bridge, a third-phase upper bridge and a third-phase lower bridge, and the control signal is injected into the BLDC motor at each potential angle in sequence, including: In the first cycle, injecting a first control signal into the third phase upper bridge, and controlling the second phase lower bridge to be turned on; In the second cycle, injecting a second control signal into the third phase upper bridge, and controlling the first phase lower bridge and the second phase lower bridge to be turned on; In the third cycle, injecting a third control signal into the third phase upper bridge, and controlling the first phase lower bridge to be turned on; In the fourth cycle, injecting a fourth control signal into the second-phase upper bridge and the third-phase upper bridge, and controlling the first-phase lower bridge to be turned on; In the fifth cycle, injecting a fifth control signal into the second phase upper bridge, and controlling the first phase lower bridge to be turned on; In the sixth cycle, injecting a sixth control signal into the second phase upper bridge, and controlling the first phase lower bridge and the third phase lower bridge to be turned on; In the seventh cycle, injecting a seventh control signal into the second phase upper bridge, and controlling the third phase lower bridge to be turned on; In the eighth cycle, injecting an eighth control signal into the first phase upper bridge and the second phase upper bridge, and controlling the third phase lower bridge to be turned on; In the ninth cycle, injecting a ninth control signal into the first phase upper bridge, and controlling the third phase lower bridge to be turned on; In the tenth cycle, injecting a tenth control signal into the first phase upper bridge, and controlling the second phase lower bridge and the third phase lower bridge to be turned on; In the eleventh cycle, injecting an eleventh control signal into the first phase upper bridge, and controlling the second phase lower bridge to be turned on; In the twelfth cycle, a twelfth control signal is injected into the third-phase upper bridge and the first-phase upper bridge, and the second-phase lower bridge is controlled to be turned on.

4. The method for starting a BLDC motor with salient polarity according to any one of claims 1 to 3, characterized in that: The starting of the BLDC motor according to the initial potential angle comprises: According to the initial potential angle, controlling the BLDC motor to operate; Acquire the reaction electromotive force of the BLDC motor, and if the correct reaction electromotive force is acquired, control the commutation of the BLDC motor according to the reaction electromotive force; Acquiring the reaction electromotive force of the BLDC motor again after the BLDC motor is commutated; When the correct reaction electromotive force is obtained M times in succession, the BLDC motor is put into closed-loop control, wherein M is a positive integer greater than or equal to 2.

5. The method for starting a BLDC motor with salient polarity according to claim 4, characterized in that: The step of starting the BLDC motor according to the initial potential angle further includes: After the BLDC motor starts to work or after the BLDC motor changes phase, starting a timer; When the timing time of the timer is reached, if the correct reaction electromotive force is not obtained, forcing the BLDC motor to commutate; When the number of forced commutation of the BLDC motor reaches a preset number threshold, it is determined that the BLDC motor fails to start; When the number of forced commutation of the BLDC motor does not reach a preset number threshold, obtaining a reaction electromotive force of the BLDC motor; If the reaction electromotive force is correct, the BLDC motor commutation is controlled according to the reaction electromotive force, and the reaction electromotive force of the BLDC motor is reacquired.

6. A control device, characterized in that: The control device comprises: at least one processor; and, a memory communicatively connected to the at least one processor; wherein, The memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the BLDC motor starting method with salient polarity as described in any one of claims 1-5.

7. An electric tool, characterized in that: The electric tool comprises: a BLDC motor with salient polarity, an inverter unit and the control device according to claim 6; The inverter unit is connected to an external power supply via a busbar, the inverter unit and the BLDC motor are connected in three phases, and the control device is connected to the inverter unit and the BLDC motor respectively.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and the computer-executable instructions are used to enable a computer to execute the BLDC motor starting method with salient polarity as described in any one of claims 1 to 5.

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