Motor starting method and device, chain saw

Abstract

This application discloses a motor starting method and apparatus, and a chainsaw. The motor starting method includes: outputting a square wave signal to drive the motor and controlling the rotor in the motor to start rotating at a preset acceleration, so that the motor generates a back electromotive force; obtaining the midpoint voltage of N pulse waves in the back electromotive force between a first moment and a second moment to obtain N midpoint voltages, wherein the first moment is the moment when the motor ends its Mth commutation, the second moment is the moment when the motor begins its (M+1)th commutation, and N and M are both integers ≥ 1; based on the N midpoint voltages, controlling the motor to switch from an open-loop state to a closed-loop state to complete the motor starting process. This method can improve the starting speed of the motor.

Description

Technical Field

[0001] This application relates to the field of motor technology, and in particular to a motor starting method and device, and a chainsaw. Background Technology

[0002] Brushless Direct Current Motors (BLDCMs) overcome the inherent defects of brushed DC motors by replacing the mechanical commutator with an electronic commutator. BLDCMs combine the excellent speed regulation performance of DC motors with the advantages of AC motors, such as simple structure, no commutation sparks, reliable operation, and ease of maintenance, making them widely used.

[0003] Currently, when a brushless DC motor starts up, it needs to go through steps such as positioning, acceleration, and constant speed in an open-loop state before switching from an open-loop state to a closed-loop state, thus completing the starting process.

[0004] However, the above-mentioned startup process is relatively long, typically taking several seconds. For some devices that require rapid startup to output high torque, such as chainsaws, the existing startup methods cannot meet the startup speed requirements of such devices. Summary of the Invention

[0005] This application aims to provide a motor starting method and device, and a chainsaw, which can improve the starting speed of a motor.

[0006] To achieve the above objectives, in a first aspect, this application provides a motor starting method, comprising:

[0007] The output square wave signal drives the motor and controls the rotor in the motor to start rotating at a preset acceleration, so that the motor generates back electromotive force;

[0008] The midpoint voltage of N pulse waves in the back electromotive force between the first time and the second time is obtained to obtain N midpoint voltages, wherein the first time is the time when the motor ends the Mth commutation, the second time is the time when the motor starts the (M+1)th commutation, and N and M are both integers ≥1;

[0009] Based on the N midpoint voltages, the motor is controlled to switch from an open-loop state to a closed-loop state to complete the motor's startup process.

[0010] In an alternative approach, the method further includes:

[0011] When the motor is in an open-loop state, the duration of each commutation of the motor is determined based on the preset acceleration, wherein the duration of the commutation is the duration between the first moment and the second moment.

[0012] In one alternative approach, controlling the motor to switch from an open-loop state to a closed-loop state based on the N midpoint voltages includes:

[0013] Obtain J midpoint voltages that increase sequentially from the N midpoint voltages, and obtain K midpoint voltages that decrease sequentially from the N midpoint voltages, where J and K are both integers ≥ 1;

[0014] Based on the J midpoint voltages and the K midpoint voltages, the motor is controlled to switch from an open-loop state to a closed-loop state.

[0015] In one optional approach, controlling the motor to switch from an open-loop state to a closed-loop state based on the J midpoint voltages and the K midpoint voltages includes:

[0016] Calculate the average or median value of the J midpoint voltages to obtain the first voltage;

[0017] Calculate the average or median value of the K midpoint voltages to obtain the second voltage;

[0018] Based on the first voltage and the second voltage, the motor is controlled to switch from an open-loop state to a closed-loop state.

[0019] In one alternative approach, controlling the motor to switch from an open-loop state to a closed-loop state based on the first voltage and the second voltage includes:

[0020] Calculate the difference between the first voltage and the second voltage;

[0021] If the difference is less than a first preset difference, the motor is controlled to switch from an open-loop state to a closed-loop state.

[0022] In an alternative approach, the method further includes:

[0023] When the difference is not less than the first preset difference,

[0024] If the difference is negative, the duty cycle of the square wave signal is reduced.

[0025] If the difference is positive, the duty cycle of the square wave signal is increased.

[0026] Secondly, this application provides a motor starting circuit, comprising:

[0027] Control processing unit, inverter and motor;

[0028] The control processing unit is connected to the motor via the inverter. The control processing unit outputs a square wave signal to the inverter to drive the motor. The control processing unit includes:

[0029] At least one processor and a memory communicatively connected to the at least one processor, the memory storing instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the method as described above.

[0030] In one alternative embodiment, the motor starting circuit further includes a voltage divider branch;

[0031] The voltage divider branch is connected between the motor and the control processing unit. The voltage divider branch is used to divide the voltage of each phase winding of the motor and input it to the control processing unit so that the control processing unit can determine the back electromotive force of each phase winding of the motor.

[0032] In one alternative embodiment, the voltage divider branch includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor;

[0033] The first resistor and the second resistor are connected in series, and the non-series connection end of the first resistor is connected to the first phase winding of the motor. The connection end between the first resistor and the second resistor is connected to the control processing unit, and the non-series connection end of the second resistor is grounded.

[0034] The third resistor and the fourth resistor are connected in series, and the non-series connection end of the third resistor is connected to the second phase winding of the motor. The connection end between the third resistor and the fourth resistor is connected to the control processing unit, and the non-series connection end of the fourth resistor is grounded.

[0035] The fifth resistor is connected in series with the sixth resistor, and the non-series connection end of the fifth resistor is connected to the third phase winding of the motor. The connection end between the fifth resistor and the sixth resistor is connected to the control processing unit, and the non-series connection end of the sixth resistor is grounded.

[0036] Thirdly, this application provides a chainsaw, including the motor starting circuit described above.

[0037] The beneficial effects of this application are as follows: The motor starting method provided by this application includes outputting a square wave signal to drive the motor and controlling the rotor in the motor to start rotating at a preset acceleration, so that the motor generates a back electromotive force (EMF). The midpoint voltages of N pulse waves in the back EMF between a first moment and a second moment are obtained to obtain N midpoint voltages, where the first moment is the end of the motor's Mth commutation, the second moment is the start of the motor's (M+1)th commutation, and N and M are both integers ≥ 1. Based on the N midpoint voltages, the motor is controlled to switch from an open-loop state to a closed-loop state to complete the motor starting process. Through the above process, the timing of switching from the open-loop state to the closed-loop state can be controlled based on the detected actual back EMF. Therefore, as soon as the back EMF meets the set conditions, the motor can be controlled to switch from the open-loop state to the closed-loop state, without needing to go through positioning, acceleration, and constant speed steps as in related technologies. This allows for faster motor starting, thus improving the motor's starting speed. Attached Figure Description

[0038] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0039] Figure 1 This is a schematic diagram of the structure of the motor starting circuit provided in the embodiments of this application;

[0040] Figure 2 A flowchart of a motor starting method provided in an embodiment of this application;

[0041] Figure 3 A schematic diagram of the back electromotive force provided in an embodiment of this application;

[0042] Figure 4 Provided for the embodiments of this application Figure 2 A schematic diagram of one embodiment of step 203 is shown in the figure;

[0043] Figure 5 Provided for the embodiments of this application Figure 4 A schematic diagram of one embodiment of step 402 is shown in the figure;

[0044] Figure 6 Provided for the embodiments of this application Figure 5 A schematic diagram of one embodiment of step 503 is shown in the figure;

[0045] Figure 7 A schematic diagram illustrating the automatic adjustment of motor rotor speed provided in an embodiment of this application;

[0046] Figure 8 This is a schematic diagram of the structure of the motor starting device provided in an embodiment of this application. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0048] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the motor starting circuit provided in an embodiment of this application. Figure 1 As shown, the motor starting circuit includes a control processing unit 100, an inverter 200, and a motor M1. The control processing unit 100 is connected to the motor M1 via the inverter 200. The control processing unit 100 outputs a square wave signal to the inverter 200 to drive the motor M1. In some embodiments, the motor M1 is a brushless DC motor.

[0049] Specifically, the control processing unit 100 may be a microcontroller unit (MCU) or a digital signal processing (DSP) controller, etc.

[0050] The control processing unit 100 includes at least one processor 101 and a memory 102. The memory 102 can be built into the control processing unit 100 or external to the control processing unit 100. The memory 102 can also be a remotely configured memory connected to the control processing unit 100 via a network.

[0051] Memory 102, as a non-volatile computer-readable storage medium, can be used to store non-volatile software programs, non-volatile computer-executable programs, and modules. Memory 102 may include a program storage area and a data storage area, wherein the program storage area may store the operating system and application programs required for at least one function; the data storage area may store data created based on the use of the terminal, etc. Furthermore, memory 102 may include high-speed random access memory and may also include non-volatile memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, memory 102 may optionally include memory remotely located relative to processor 101, and these remote memories can be connected to the terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0052] The processor 101 performs various functions of the terminal and processes data by running or executing software programs and / or modules stored in the memory 102 and calling data stored in the memory 102, thereby performing overall monitoring of the terminal, such as implementing the motor starting method described in any embodiment of the present invention.

[0053] Processor 101 can be one or more. Figure 1 The example provided uses a processor 101. The processor 101 and memory 102 can be connected via a bus or other means. The processor 101 may include a central processing unit (CPU), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a controller, a field-programmable gate array (FPGA) device, etc. The processor 101 can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0054] In one embodiment, please continue to refer to Figure 1 The motor starting circuit also includes a voltage divider branch 300. The voltage divider branch 300 is connected between the motor M1 and the control processing unit 100.

[0055] Specifically, the voltage divider branch 300 is used to divide the voltage of each phase winding of motor M1 and input it to the control processing unit 100 so that the control processing unit 100 can determine the back electromotive force of each phase winding of motor M1. Then, when motor M1 starts, the control processing unit 100 can control motor M1 to start quickly based on the back electromotive force of each phase winding of motor M1.

[0056] In one embodiment, the voltage divider branch 300 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a sixth resistor R6.

[0057] The first resistor R1 and the second resistor R2 are connected in series, and the non-series connection end of the first resistor R1 is connected to the first phase winding of the motor M1. The connection end P1 between the first resistor R1 and the second resistor R2 is connected to the control processing unit 100, and the non-series connection end of the second resistor R2 is grounded to GND.

[0058] The third resistor R3 and the fourth resistor R4 are connected in series, and the non-series connection end of the third resistor R3 is connected to the second phase winding of the motor M1. The connection end P2 between the third resistor R3 and the fourth resistor R4 is connected to the control processing unit 100, and the non-series connection end of the fourth resistor R4 is grounded to GND.

[0059] The fifth resistor R5 and the sixth resistor R6 are connected in series, and the non-series connection terminal of the fifth resistor R5 is connected to the third phase winding of the motor M1. The connection terminal P3 between the fifth resistor R5 and the sixth resistor R6 is connected to the control processing unit 100, and the non-series connection terminal of the sixth resistor R6 is grounded to GND.

[0060] Specifically, the first resistor R1 and the second resistor R2 are used to divide the voltage of the first phase winding, and the voltage across the second resistor R2 is input to the control processing unit 100. The control processing unit 100 can deduce the voltage of the first phase winding, i.e., the back electromotive force generated by the first phase winding, based on the received voltage. The specific functions of the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 are similar to those of the first resistor R1 and the second resistor R2, and are readily understood by those skilled in the art, and will not be elaborated further here.

[0061] This application also provides a chainsaw, which includes the motor starting circuit found in any embodiment of this application. In one embodiment, the chainsaw can be a diesel chainsaw or an electric chainsaw.

[0062] Please refer to Figure 2 , Figure 2 This is a flowchart illustrating a motor driving method provided in an embodiment of the present invention. The method can be... Figure 1 The motor starting circuit shown is executed. For example... Figure 2 As shown, the motor driving method includes:

[0063] Step 201: Output a square wave signal to drive the motor and control the rotor in the motor to start rotating at a preset acceleration so that the motor generates back electromotive force.

[0064] Specifically, the motor can be started by outputting a square wave signal to drive it. The duty cycle of the square wave signal determines the starting torque of the motor. In practical applications, the duty cycle of the square wave signal at the start of motor operation can be set according to the load conditions. The heavier the load, the larger the duty cycle of the square wave signal can be set. Load weight is relative to the power consumption of the load; a light load means low power consumption and low motor torque requirement; conversely, a heavy load means high power consumption and high motor torque requirement. In some implementations, the duty cycle of the square wave signal at the start of motor operation can be set to greater than or equal to 50% to quickly drive the motor rotor to rotate.

[0065] Simultaneously, the rotor speed in the drive motor is accelerated from 0 using a preset acceleration. In some embodiments, when the motor is in open-loop mode, the duration of each commutation can be determined based on the preset acceleration. The commutation duration refers to the interval between the end of the Mth commutation and the start of the (M+1)th commutation. For example, the duration between the end of the 1st commutation and the start of the 2nd commutation is the duration of one commutation. A larger preset acceleration results in a shorter commutation duration; conversely, a smaller preset acceleration results in a longer commutation duration.

[0066] Understandably, in the embodiments of this application, when the motor starts, direct control of the motor is implemented without collecting the motor's operating signals for feedback control, so the motor is in an open-loop state. Only after the motor is running at a constant speed can the commutation time be accurately estimated. Therefore, after the motor starts, it is necessary to first drive it to a constant speed before switching from the open-loop state to the closed-loop state, completing the motor startup. In the closed-loop state, the motor's operating signals (such as operating speed signals) are collected in real time for feedback control to achieve precise control of the motor, such as controlling the actual operating speed of the motor to be equal to the preset target operating speed.

[0067] Step 202: Obtain the midpoint voltage of the N pulse waves in the back electromotive force between the first and second time moments to obtain N midpoint voltages.

[0068] Step 203: Based on N midpoint voltages, control the motor to switch from open-loop state to closed-loop state to complete the motor starting process.

[0069] Here, the first moment is the moment when the motor ends its Mth commutation, and the second moment is the moment when the motor begins its (M+1)th commutation, where N and M are both integers ≥ 1. Based on the above explanation, the commutation duration is the time between the first and second moments.

[0070] Taking a three-phase motor as an example, assume that at the end of the first commutation, the motor switches to operation with the first phase winding. After the first phase winding finishes operating, it needs to commutate to the second phase winding. Then, after the first phase winding finishes operating, commutation begins again, which is the start time of the second commutation. Therefore, in this embodiment, the duration of this commutation is the time between the end of the first commutation and the start of the second commutation, which is also the operating time of the first phase winding.

[0071] Please refer to the above as well. Figure 3 , Figure 3 The diagram illustrates three possible back electromotive forces generated by any one phase of a motor during operation.

[0072] like Figure 3 As shown, curve L1 represents the back electromotive force (EMF) waveform of one phase winding of the motor rotor during uniform speed operation; curve L2 represents the back EMF waveform of one phase winding of the motor rotor during acceleration operation; and curve L3 represents the back EMF waveform of one phase winding of the motor rotor during deceleration operation. Taking curve L1 as an example, the back EMF pulse wave occurs between time T1 and time T2, with a midpoint voltage of V1. Furthermore, when time T1 corresponds to the end of the Mth commutation, time T3 corresponds to the start of the (M+1)th commutation. In this case, time T1 corresponds to the first time, and time T2 corresponds to the second time. There are N pulse waves between the first and second times, i.e., between time T1 and time T2. By sampling the midpoint voltage of each pulse wave, N midpoint voltages can be sampled from the N pulse waves.

[0073] Subsequently, by combining curves L1, L2, and L3, it can be seen that the distribution of the N midpoint voltages differs depending on the motor windings' operating states (including constant speed, acceleration, and deceleration). Therefore, based on the N midpoint voltages, the time point at which the motor can be switched from an open-loop state to a closed-loop state can be determined to complete the motor's startup process.

[0074] In related technologies, the startup process requires steps such as positioning, acceleration, and constant speed in an open-loop state before switching to a closed-loop state. On the one hand, these technologies require each step to be executed sequentially, typically taking several seconds, making them unsuitable for devices requiring rapid startup. However, the embodiments of this application eliminate the need for a positioning step and utilize back electromotive force after acceleration to determine the switch from open-loop to closed-loop, further reducing time. Therefore, this application typically achieves motor startup within one second. Clearly, compared to related technologies, the solution described in this application significantly improves motor startup speed.

[0075] On the other hand, the methods used in related technologies to implement each step typically involve applying a pre-set voltage to the motor to drive it through positioning, acceleration, and constant speed processes. However, this is an open-loop control method that does not acquire information about whether the motor is operating according to the pre-set parameters. In contrast, this application utilizes the back electromotive force of the motor during actual operation, meaning that the motor's starting is controlled based on its actual operating conditions. Therefore, compared to the solutions in related technologies, the starting method of this application offers higher reliability and stability.

[0076] In one embodiment, such as Figure 4 As shown, step 203, which controls the motor to switch from an open-loop state to a closed-loop state based on N midpoint voltages, includes the following steps:

[0077] Step 401: Obtain J midpoint voltages that increase sequentially from the N midpoint voltages, and obtain K midpoint voltages that decrease sequentially from the N midpoint voltages.

[0078] Step 402: Based on the J midpoint voltages and K midpoint voltages, control the motor to switch from open-loop state to closed-loop state.

[0079] Where J and K are both integers ≥ 1.

[0080] Still with Figure 3 Taking curve L1 as an example, at the first time point corresponding to time T1 and the second time point corresponding to time T3, the J midpoint voltages that increase sequentially include the first midpoint voltage V1, the second midpoint voltage V2, ... the Jth midpoint voltage VJ. The K midpoint voltages that decrease sequentially include the first midpoint voltage V11, the second midpoint voltage V12, ... the Kth midpoint voltage V1K.

[0081] Depend on Figure 3 As shown by curves L1, L2, and L3, the back electromotive force (EMF) of the motor undergoes three processes after each commutation: a sequential increase in voltage, a period of constant voltage, and a sequential decrease in voltage. Furthermore, the difference in back EMF under different operating states of the motor rotor (including constant speed, acceleration, and deceleration) lies in the difference between the sequential increase and decrease in voltage components. For example, when the motor is operating at a constant speed, the sequential increase and decrease in voltage components exhibit a symmetrical relationship, with the axis of symmetry being the straight line containing the midpoint between the first and second time points. Therefore, in practical applications, by determining the relationship between these two components, the actual operating state of the motor can be determined, thereby identifying the time point for switching from the open-loop to the closed-loop state.

[0082] In one implementation, such as Figure 5As shown, step 402, which controls the motor to switch from an open-loop state to a closed-loop state based on J midpoint voltages and K midpoint voltages, includes the following steps:

[0083] Step 501: Calculate the average or median value of the J midpoint voltages to obtain the first voltage.

[0084] Step 502: Calculate the average or median value of the K midpoint voltages to obtain the second voltage.

[0085] Step 503: Based on the first voltage and the second voltage, control the motor to switch from the open-loop state to the closed-loop state.

[0086] Specifically, taking J=K=3 as an example, assuming that the J midpoint voltages are 1V, 2V and 6V respectively, and the K midpoint voltages are 6V, 4V and 2V respectively, then the first voltage can be the average value of 3V or the median value of 2V; the second voltage can be the average value of 4V or the median value of 4V.

[0087] In practical applications, by determining the relationship between the first voltage and the second voltage, it is possible to determine the relationship between the two parts of voltage increasing sequentially and voltage decreasing sequentially, so as to determine the actual operating state of the motor and then determine the time point for switching from the open-loop state to the closed-loop state.

[0088] It should be noted that in this embodiment, the average value or median value is used as an example. In other embodiments, other methods can be used to determine the relationship between the two parts of voltage increasing sequentially and voltage decreasing sequentially, such as using the root mean square of J midpoint voltages and K midpoint voltages.

[0089] In one implementation, such as Figure 6 As shown, step 503, which controls the motor to switch from an open-loop state to a closed-loop state based on J midpoint voltages and K midpoint voltages, includes the following steps:

[0090] Step 601: Calculate the difference between the first voltage and the second voltage.

[0091] Step 602: If the difference is less than the first preset difference, control the motor to switch from open-loop state to closed-loop state.

[0092] The first preset difference can be set according to the actual application situation, and this application embodiment does not impose specific restrictions on it.

[0093] When the difference between the first voltage and the second voltage is less than a first preset difference, the difference can be considered negligible, meaning the first voltage and the second voltage are considered equal. In this case, the sequential increase and decrease of voltage described in the above embodiment are symmetrical about the line containing the midpoint between the first and second moments. Therefore, it can be determined that the motor rotor should be running at a constant speed. Subsequently, the motor can be controlled to switch from an open-loop state to a closed-loop state, thus completing the startup process.

[0094] In another embodiment, the motor starting method further includes the following steps: when the difference is not less than a first preset difference, if the difference is negative, the duty cycle of the square wave signal is reduced; if the difference is positive, the duty cycle of the square wave signal is increased.

[0095] Specifically, if the difference between the first voltage and the second voltage is not less than a first preset difference, then it is determined that the first voltage and the second voltage are not equal. The motor rotor is in an acceleration or deceleration state.

[0096] When the difference is negative, it indicates that the motor rotor is accelerating. In this case, the duty cycle of the square wave signal of the drive motor should be reduced to decrease the rotor speed.

[0097] When the difference is positive, it can be determined that the motor rotor is in a deceleration state. At this time, the duty cycle of the square wave signal of the drive motor should be increased to increase the speed of the motor rotor.

[0098] In one embodiment, please refer to the following: Figure 7 , Figure 7 The example illustrates a method for adjusting the rotor speed of a motor. For instance... Figure 7 As shown, Erro is the difference between the first voltage and the second voltage; ∑ is the summation calculation used to accumulate the difference; PI is a proportional-integral controller; the initial duty cycle is the duty cycle of the square wave signal output when the motor just starts, that is, the duty cycle of the square wave signal in step 201 of the above embodiment; the new duty cycle is the duty cycle that needs to be updated after PI adjustment, that is, the duty cycle of the square wave signal of the drive motor is adjusted to this new duty cycle.

[0099] Taking an initial duty cycle of 50% as an example. When Erro < 0, the motor rotor is in an accelerated state. After PI regulation, the new duty cycle output is 50% - A%. Here, A is the adjustment parameter, and A > 0. The value of A is determined by the value of Erro. ​​The larger Erro is, the larger the adjustment range required, and therefore the larger A is; the smaller Erro is, the smaller the adjustment range required, and therefore the smaller A is.

[0100] When Erro > 0, the motor rotor is in a deceleration state, and the new duty cycle output after PI regulation is 50% + B%. Here, B is the adjustment parameter, and B > 0. The value of B is determined by the value of Erro; the larger Erro is, the larger the adjustment range required, and therefore the larger B is; the smaller Erro is, the smaller the adjustment range required, and therefore the smaller B is.

[0101] The above method achieves the adjustment of the duty cycle of the square wave signal, thereby quickly adjusting the motor rotor speed to a uniform operating state. This allows for a faster switch from open-loop to closed-loop operation, facilitating faster startup. Furthermore, in applications with lighter loads, the switch from open-loop to closed-loop operation can be accelerated by increasing the P value and decreasing the I value in the PI converter. For example, in some implementations, the P value is set to Q15 (0.5), and the I value is set to Q15 (0.001), where Q15 is a per-unit format, with a maximum value of 32768 representing the value 1. Q15 (0.5) is 16384, and Q15 (0.001) is 32.768.

[0102] Figure 8 This is a schematic diagram of the structure of a motor starting device provided in an embodiment of the present invention. Figure 8 As shown, the motor starting device 800 includes a back electromotive force generating unit 801, a voltage acquisition unit 802, and a state switching unit 803.

[0103] The back electromotive force (EMF) generation unit 801 outputs a square wave signal to drive the motor and controls the rotor in the motor to start rotating at a preset acceleration, thereby generating a back EMF. The voltage acquisition unit 802 acquires the midpoint voltage of the N pulse waves in the back EMF between a first moment and a second moment, thus obtaining N midpoint voltages. The first moment is the end of the Mth commutation of the motor, and the second moment is the start of the (M+1)th commutation of the motor; N and M are both integers ≥ 1. The state switching unit 803 controls the motor to switch from an open-loop state to a closed-loop state based on the N midpoint voltages, thereby completing the motor startup process.

[0104] Since the device embodiments and method embodiments are based on the same concept, the content of the device embodiments can refer to the method embodiments, provided that the content does not conflict with each other, and will not be repeated here.

[0105] This invention also provides a non-volatile computer-readable storage medium storing computer-executable instructions that, when executed by a motor starting circuit, cause the motor starting circuit to perform the method described in any of the above embodiments.

[0106] This invention also provides a computer program product, which includes a computer program stored on a computer-readable storage medium. The computer program includes program instructions that, when executed by a computer, cause the computer to perform the method in any embodiment of this application.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method of starting an electric machine, characterized in that include: The output square wave signal drives the motor and controls the rotor in the motor to start rotating at a preset acceleration, so that the motor generates back electromotive force; The midpoint voltage of N pulse waves in the back electromotive force between the first time and the second time is obtained to obtain N midpoint voltages, wherein the first time is the time when the motor ends the Mth commutation, the second time is the time when the motor starts the (M+1)th commutation, and N and M are both integers ≥1; Based on the N midpoint voltages, the motor is controlled to switch from an open-loop state to a closed-loop state to complete the motor's startup process; The step of controlling the motor to switch from an open-loop state to a closed-loop state based on the N midpoint voltages includes: Obtain J midpoint voltages that increase sequentially from the N midpoint voltages, and obtain K midpoint voltages that decrease sequentially from the N midpoint voltages, where J and K are both integers ≥ 1; Calculate the average or median value of the J midpoint voltages to obtain the first voltage; Calculate the average or median value of the K midpoint voltages to obtain the second voltage; Calculate the difference between the first voltage and the second voltage; If the difference is less than a first preset difference, the motor is controlled to switch from an open-loop state to a closed-loop state.

2. The method of claim 1, wherein, The method further includes: When the motor is in an open-loop state, the duration of each commutation of the motor is determined based on the preset acceleration, wherein the duration of the commutation is the duration between the first moment and the second moment.

3. The method of claim 1, wherein, The method further includes: When the difference is not less than the first preset difference, If the difference is negative, the duty cycle of the square wave signal is reduced. If the difference is positive, the duty cycle of the square wave signal is increased.

4. A motor starting circuit, characterized by include: Control processing unit, inverter and motor; The control processing unit is connected to the motor via the inverter. The control processing unit outputs a square wave signal to the inverter to drive the motor. The control processing unit includes: At least one processor and a memory communicatively connected to the at least one processor, the memory storing instructions executable by the at least one processor to enable the at least one processor to perform the method according to any one of claims 1-3.

5. The motor starting circuit of claim 4, wherein, The motor starting circuit also includes a voltage divider branch; The voltage divider branch is connected between the motor and the control processing unit. The voltage divider branch is used to divide the voltage of each phase winding of the motor and input it to the control processing unit so that the control processing unit can determine the back electromotive force of each phase winding of the motor.

6. The motor starting circuit of claim 5, wherein, The voltage divider branch includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor; The first resistor and the second resistor are connected in series, and the non-series connection end of the first resistor is connected to the first phase winding of the motor. The connection end between the first resistor and the second resistor is connected to the control processing unit, and the non-series connection end of the second resistor is grounded. The third resistor and the fourth resistor are connected in series, and the non-series connection end of the third resistor is connected to the second phase winding of the motor. The connection end between the third resistor and the fourth resistor is connected to the control processing unit, and the non-series connection end of the fourth resistor is grounded. The fifth resistor is connected in series with the sixth resistor, and the non-series connection end of the fifth resistor is connected to the third phase winding of the motor. The connection end between the fifth resistor and the sixth resistor is connected to the control processing unit, and the non-series connection end of the sixth resistor is grounded.

7. A chain saw, characterized in that Includes the motor starting circuit as described in any one of claims 4-6.

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