A position control method and device for a three-phase brushless DC motor

Abstract

The embodiment of the application discloses a position control method and device of a three-phase brushless direct current motor. The position control method comprises the following steps: obtaining the zero-crossing time of the back electromotive force voltage of the non-powered phase of the motor stator; determining the commutation time point of the motor stator driving coil according to the zero-crossing time of the back electromotive force voltage, the preset stator magnetic field and rotor magnetic field angle of the motor, the commutation angle greater than 30 degrees and less than 60 degrees, and the rotor speed; determining the starting angle of the stator-rotor magnetic field angle after commutation and recording the commutation frequency according to the rotor speed and the commutation time point, so as to control the position and speed of the brushless direct current motor; when the motor starts, the stator position and powered stator coil information recorded after the last motor stop are used to continue to power the motor and determine the power-on time and power supply voltage. The position control method and device of the three-phase brushless direct current motor provided by the embodiment of the application can guarantee the position control precision and rotation stability of the three-phase brushless direct current motor.

Description

Technical Field

[0001] The embodiments of the present invention relate to motor control technology, and more particularly to a position control method and apparatus for a sensorless three-phase brushless DC motor. Background Technology

[0002] Three-phase brushless DC motors, as synchronous motors consisting of the motor body and driver, are characterized by small size, high efficiency, high power and high reliability, and are widely used in many fields of life and production.

[0003] Currently, existing position control methods for three-phase brushless DC motors typically rely on sensors to acquire the motor's position information and control its position. During motor rotation, the angle between the stator and rotor magnetic fields cycles between 120 and 60 degrees, with the stator commutating at the 60-degree angle. For sensorless motors, the accuracy of position and speed control is relatively low. Summary of the Invention

[0004] This invention provides a position control method and apparatus for a three-phase brushless DC motor to ensure the reliability of position and speed control of the three-phase brushless DC motor.

[0005] In a first aspect, embodiments of the present invention provide a position control method for a three-phase brushless DC motor, comprising:

[0006] Obtain the zero-crossing time of the back EMF voltage of the drive coil of the unenergized phase of the motor stator;

[0007] Based on the zero-crossing time of the back EMF voltage of the drive coil, the commutation angle between the motor's preset stator magnetic field and rotor magnetic field (less than 60 degrees and greater than 30 degrees), and the rotor speed, the commutation time of the motor's stator drive coil is determined.

[0008] Based on the rotor speed and commutation time, determine the starting angle of the magnetic field angle between the stator and rotor after commutation and record the number of commutations in order to control the position and speed of the brushless DC motor.

[0009] When the motor starts, based on the stator position and energized stator coil information recorded after the previous motor stop, power is supplied to the motor again, and the energizing time and supply voltage are determined. Specifically, the energizing time for the first commutation step during motor startup is longer than the power supply time for the energized phase during normal motor rotation, causing the rotor to creep and reducing the angle between the stator and rotor magnetic fields. The supply voltage for the first commutation step is less than the supply voltage for normal motor rotation. The supply voltage for the second and subsequent n steps is greater than or equal to the supply voltage for normal motor rotation, and the power supply time for the second and subsequent n steps is less than the power supply time for the first step but greater than the power supply time for normal motor rotation. The n steps during motor startup are the starting steps; after these n steps, the motor rotates normally.

[0010] When the motor stops rotating, the voltage and energizing time supplied to the motor stator coils are determined based on the stator position and energized stator coil information recorded after the last motor stop, and the stator position and energized stator coil information are recorded; wherein, the energizing time is longer than the time required for the motor to rotate normally.

[0011] Optionally, the commutation time of the motor stator drive coil is determined based on the zero-crossing time of the back EMF voltage of the drive coil, the preset commutation angle between the stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed. This includes:

[0012] If commutation occurs when the angle between the stator magnetic field and the rotor magnetic field reaches the commutation angle, then the sum of the zero-crossing time of the back EMF voltage of the brushless DC motor and the time required for the current step to continue rotating to the commutation angle is determined.

[0013] The sum of the zero-crossing time of the back EMF voltage and the time required for the current step to continue rotating to the commutation angle is taken as the commutation time point.

[0014] Optionally, based on the rotor speed and commutation time, the initial angle between the stator magnetic field and the rotor magnetic field after commutation is determined and the number of commutations is recorded to control the position and speed of the brushless DC motor, including:

[0015] Control the next phase commutation of the stator based on the commutation timing;

[0016] If the rotor speed increases, the starting angle of the next step is controlled to decrease according to the rotor speed; if the rotor speed decreases, the starting angle of the next step is controlled to increase according to the rotor speed.

[0017] Optionally, the starting angle range is the range of the included angle between the stator and rotor magnetic fields, which is 60 to 30 degrees.

[0018] Optionally, after determining the initial angle between the stator magnetic field and the rotor magnetic field after commutation, the following steps are included:

[0019] Record the target sector and stator coil energization information corresponding to the stop of rotation of the brushless DC motor from rotation to stop.

[0020] Based on the target sector, control the brushless DC motor to perform forward or reverse rotation in the target sector during the next startup.

[0021] Optionally, after determining the initial angle between the stator magnetic field and the rotor magnetic field after commutation, the following steps are included:

[0022] Record the target sector corresponding to the point where the brushless DC motor stops rotating as it goes from rotation to a complete stop.

[0023] Based on the target sector, when the brushless DC motor rotates to the target sector before the next stop, the power supply time of the brushless DC motor is increased.

[0024] Optionally, the power supply time of the brushless DC motor is extended, the magnetic field angle between the stator and rotor of the brushless DC motor approaches 0 degrees, and the brushless DC motor decelerates until it stops rotating.

[0025] Secondly, embodiments of the present invention provide a position control device for a brushless DC motor, comprising:

[0026] The data acquisition module is used to acquire the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator;

[0027] The commutation determination module is used to determine the commutation time of the motor stator drive coil based on the zero-crossing time of the back EMF voltage of the drive coil, the preset commutation angle between the stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed.

[0028] The position control module is used to determine the starting angle of the magnetic field between the stator and rotor after commutation based on the rotor speed and commutation time point, and to record the number of commutations, so as to control the position and speed of the brushless DC motor.

[0029] The voltage determination module is used to continue supplying power to the motor and determine the energizing time and supply voltage based on the stator position and energized stator coil information recorded after the motor stopped last time when the motor starts. Specifically, the energizing time for the first commutation step of the motor startup is longer than the power supply time for the energized phase during normal motor rotation, so as to induce rotor creep and reduce the angle between the stator and rotor magnetic fields. The supply voltage for the first commutation step is less than the supply voltage for normal motor rotation. The supply voltage for the second step and the subsequent n steps is greater than or equal to the supply voltage for normal motor rotation. The power supply time for the second step and the subsequent n steps is less than the power supply time for the first step but greater than the power supply time for normal motor rotation. The n steps during motor startup are the starting steps, after which the motor rotates normally.

[0030] The information recording module is used to determine the voltage and energizing time to be supplied to the motor stator coils based on the stator position and energized stator coil information recorded after the motor stopped rotating, and to record the stator position and energized stator coil information; wherein, the energizing time is longer than the time required for the motor to rotate normally.

[0031] Optionally, the commutation determination module includes:

[0032] The time determination unit is used to determine the sum of the zero-crossing time of the back EMF voltage of the brushless DC motor and the time required for the current step to continue rotating to the commutation angle if commutation is performed when the angle between the stator magnetic field and the rotor magnetic field reaches the commutation angle.

[0033] The commutation determination unit is used to take the sum of the back EMF voltage zero-crossing time and the time required for the current step to continue rotating to the commutation angle as the commutation time point.

[0034] Optional, the position control module includes:

[0035] The commutation control unit is used to control the current sector of the stator magnetic field and rotor magnetic field to the next commutation step according to the commutation time point;

[0036] An angle control unit is used to control the starting angle of the next step to decrease if the rotor speed increases, and to control the starting angle of the next step to increase if the rotor speed decreases.

[0037] The position control method and apparatus for a three-phase brushless DC motor provided in this invention obtains the zero-crossing time of the back EMF voltage of the drive coil of the unenergized phase of the motor stator; determines the commutation time of the stator drive coil based on the zero-crossing time of the back EMF voltage of the drive coil, the preset commutation angle between the stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed; and determines the starting angle of the angle between the stator and rotor magnetic fields after commutation based on the rotor speed and the commutation time, and records the number of commutations, thereby controlling the position and speed of the brushless DC motor. The position control method and device for a three-phase brushless DC motor provided in this invention determines the initial angle between the stator magnetic field and the rotor magnetic field after commutation based on the rotor speed and commutation time. If the rotor speed increases (or decreases), the initial angle between the stator magnetic field and the rotor magnetic field after commutation is controlled to decrease (or increase). Since a sudden increase (or decrease) in load will lead to deceleration (speed increase), the increase (or decrease) in the initial angle will cause the rotor to obtain a larger (or smaller) torque for acceleration (or deceleration), thereby realizing the sensorless return of the three-phase brushless DC motor speed, ensuring uniform motor rotation, preventing motor step loss, and ensuring the reliability of motor position and speed control. Attached Figure Description

[0038] Figure 1 This is a flowchart of a position control method for a three-phase brushless DC motor provided in Embodiment 1 of the present invention;

[0039] Figure 2 This is a flowchart of a position control method for a three-phase brushless DC motor provided in Embodiment 2 of the present invention;

[0040] Figure 3 This is a schematic diagram of an electromagnetic torque of a motor provided in Embodiment 2 of the present invention;

[0041] Figure 4 This is a schematic diagram of another type of motor electromagnetic torque provided in Embodiment 2 of the present invention;

[0042] Figure 5This is a schematic diagram of another type of motor electromagnetic torque provided in Embodiment 2 of the present invention;

[0043] Figure 6 This is a flowchart of a motor speed control method provided in Embodiment 2 of the present invention;

[0044] Figure 7 This is another flowchart of motor speed control provided in Embodiment 2 of the present invention;

[0045] Figure 8 This is a flowchart of a motor position control method provided in Embodiment 2 of the present invention;

[0046] Figure 9 This is a structural block diagram of a position control device for a three-phase brushless DC motor provided in Embodiment 3 of the present invention. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0048] Example 1

[0049] Figure 1 This is a flowchart of a position control method for a three-phase brushless DC motor according to Embodiment 1 of the present invention. This embodiment is applicable to the position control of three-phase brushless DC motors, such as sensorless brushless DC motors. The method can be executed by a position control device for the three-phase brushless DC motor, which can be implemented in software and / or hardware. The device can be integrated into the controller of the three-phase brushless DC motor. The method specifically includes the following steps:

[0050] Step 110: Obtain the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator.

[0051] In the case of a three-phase brushless DC motor, when the three-phase sensorless brushless DC motor is rotating normally, the rotor magnetic field and the stator magnetic field are in the same sector for part of the time. The position control device of the three-phase brushless DC motor can detect and obtain the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator in real time.

[0052] Step 120: Determine the commutation time of the motor stator drive coil based on the zero-crossing time of the back EMF voltage of the drive coil, the commutation angle between the motor's preset stator magnetic field and rotor magnetic field (less than 60 degrees and greater than 30 degrees), and the rotor speed.

[0053] Specifically, the brushless DC motor employs a six-step commutation method, with each phase having an electrical angle of 60 degrees and each step rotating 60 degrees, totaling 360 degrees. Commutation occurs when the rotor magnetic field and stator magnetic field are in the same sector, i.e., the angle between the stator and rotor magnetic fields is less than 60 degrees. When the zero-crossing point of the reverse electromotive force (EMF) voltage is detected when no power is applied, the commutation time can be calculated. For example, the sum of the zero-crossing time of the brushless DC motor's voltage and the time required for the current step to continue rotating to the commutation angle can be used as the commutation time point to control the commutation of the brushless DC motor.

[0054] Step 130: Based on the rotor speed and commutation time, determine the starting angle of the magnetic field angle between the stator and rotor after commutation and record the number of commutations to control the position and speed of the brushless DC motor.

[0055] Specifically, if the load increases (or decreases), the starting angle between the stator magnetic field and the rotor magnetic field in the S+1 sector is increased (or decreased). Since the sudden increase (or decrease) in load will lead to deceleration (speed increase), the rotor will obtain a larger (or smaller) torque to accelerate (or decelerate) as the starting angle in the S+1 sector increases (or decreases), thereby realizing the return of motor speed and making the motor rotate at a more uniform speed.

[0056] Step 140: When the motor starts, based on the stator position and energized stator coil information recorded after the motor stopped last time, continue to supply power to the motor and determine the energizing time and supply voltage.

[0057] In this process, the energizing time for the first commutation phase during motor startup is longer than the energizing time for the motor's normal rotation phase, causing the rotor to creep and reducing the angle between the stator and rotor magnetic fields. The energizing voltage for the first commutation phase is less than the energizing voltage for the motor's normal rotation. The energizing voltage for the second and subsequent n steps is greater than or equal to the energizing voltage for the motor's normal rotation. The energizing time for the second and subsequent n steps is less than the energizing time for the first step but greater than the energizing time for the motor's normal rotation. The n steps during motor startup are the starting steps, after which the motor rotates normally.

[0058] Step 150: When the motor stops rotating, refer to the stator coil power supply voltage and energizing time recorded during the previous motor stop to determine the voltage and energizing time supplied to the motor stator coil, and record the stator position and energized stator coil information; wherein, the energizing time is greater than the time required for the motor to rotate normally.

[0059] The position control method for a three-phase brushless DC motor provided in this embodiment determines the initial angle between the stator magnetic field and the rotor magnetic field after commutation based on the motor speed and commutation time. If the rotor speed increases (or decreases), the initial angle between the stator magnetic field and the rotor magnetic field after commutation is reduced (or increased). Since a sudden increase (or decrease) in load will lead to deceleration (speed increase), the increased (or decreased) initial angle will cause the rotor to obtain a larger (or smaller) torque for acceleration (or deceleration), thereby realizing the speed return of the three-phase sensorless brushless DC motor, making the motor rotate at a more uniform speed, and ensuring the reliability of the motor's position and speed control.

[0060] Example 2

[0061] Figure 2 This is a flowchart of a position control method for a three-phase brushless DC motor provided in Embodiment 2 of the present invention. This embodiment is applicable to position control of three-phase brushless DC motors, etc. The method can be executed by a position control device for the three-phase brushless DC motor, which can be implemented in software and / or hardware. The device can be integrated into the controller of the three-phase brushless DC motor. The method specifically includes the following steps:

[0062] Step 210: Obtain the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator.

[0063] In the case of a three-phase brushless DC motor, when the three-phase sensorless brushless DC motor is rotating normally, the rotor magnetic field and the stator magnetic field are in the same sector for part of the time. The position control device of the three-phase brushless DC motor can detect and obtain the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator in real time.

[0064] Step 220: If commutation occurs when the angle between the stator magnetic field and the rotor magnetic field reaches the commutation angle, then determine the sum of the zero-crossing time of the brushless DC motor voltage and the time required to continue rotating to the commutation angle in the current step.

[0065] The position control device for the three-phase brushless DC motor can determine the voltage zero-crossing time. The specific method for determining the voltage zero-crossing time can refer to the zero-crossing calculation process in existing technology, and will not be elaborated here. The time required for the current step to continue rotating to the commutation angle can be determined according to the actual control requirements of the motor, and is not limited here.

[0066] Step 230: Take the sum of the voltage zero-crossing time and the time required to continue rotating to the commutation angle in the current step as the commutation time point.

[0067] Specifically, signals such as current signals from three-phase brushless DC motors are filtered to prevent signal interference. Because filtering introduces a delay, the voltage zero-crossing time needs to be delayed by the time required for the current step to reach the commutation angle before commutation, ensuring the accuracy of the commutation timing.

[0068] Step 240: Control the next phase commutation of the stator according to the commutation time point.

[0069] Step 250: If the rotor speed increases, control the starting angle of the next step to decrease according to the rotor speed; if the rotor speed decreases, control the starting angle of the next step to increase according to the rotor speed.

[0070] The initial angle range is the range of the included angle between the stator and rotor magnetic fields, which is 60 to 30 degrees. The angle at which the initial angle increases or decreases is less than 60 degrees. For example, Figure 3 This is a schematic diagram of an electromagnetic torque of a motor provided in Embodiment 2 of the present invention. (Reference) Figure 3 A brushless DC motor generates a rotating magnetic field in a six-step process. Each commutation (or each step involves rotating the motor by an electrical angle of 60 degrees) assumes the stator generates the rotating magnetic field through UVW energization, and the rotor is a permanent magnet. The motor starts when the stator and rotor magnetic fields are completely aligned, i.e., the angle between them is 0 degrees. Stator commutation energization can achieve ±60 degrees, ±120 degrees, and 180 degrees with the rotor magnetic field, with 180 degrees being the critical state. Typically, energizing at ±120 degrees results in high torque and efficiency; energizing at ±60 degrees results in low efficiency. The electromagnetic torque formula for the motor is N = K * I * sinθ, where K is a coefficient, I is the current, and θ is the angle between the stator and rotor magnetic fields. Under rated voltage and rated motor speed, the angle between the stator and rotor magnetic fields operates between 60 + α and α. When the speed remains constant, the initial angle α changes according to the motor speed. For motors with an angle of α less than 60 degrees and greater than 30 degrees, the larger the angle of α, the greater the average output torque of the motor and the higher the motor efficiency. The specific value of α is related to the motor power, motor load, motor speed, motor speed and position control accuracy, and is not limited here.

[0071] For example, Figure 4 This is a schematic diagram of another type of motor electromagnetic torque provided in Embodiment 2 of the present invention. Figure 5 This is a schematic diagram of another method for reducing the electromagnetic torque of a motor according to Embodiment 2 of the present invention, used to stop the motor rotation, i.e., the final step in the motor rotation process. (Reference) Figure 4 When the motor load increases, the motor speed decreases, leading to a larger angle between the stator and rotor magnetic fields. This, in turn, increases the α angle during the next commutation phase, providing greater driving force to the motor and increasing its speed. This feedback loop then stabilizes the speed. (Reference) Figure 5When the motor load decreases, the motor speed will increase, which will cause the magnetic field angle between the stator and rotor to decrease. This will result in a smaller α angle during the next commutation, providing less driving force to the motor and causing the motor speed to decrease. This will cause the speed to return to the speed before the change, forming a speed control feedback closed loop, thereby achieving speed stability.

[0072] Step 260: Record the target sector corresponding to the point where the brushless DC motor stops rotating.

[0073] Step 270: Based on the target sector, when the brushless DC motor rotates to the target sector before stopping, control the power supply time of the brushless DC motor to be extended.

[0074] Specifically, as the power supply time of a three-phase brushless DC motor increases, the angle between the stator and rotor magnetic fields approaches 0 degrees, causing the motor to decelerate until it stops. Conversely, as the power supply voltage decreases, the motor's torque decreases, further decelerating until it stops. Based on the recorded sector S (S = 0-5) when the motor stops, a longer power supply in the final step of the target position (stop position) gradually reduces the motor's torque to below the level of rotational friction, leading to deceleration and stop. However, due to the motor's high inertia, if the rotor passes the target sector... Figure 5 As shown, the motor stator provides a reverse braking torque to stop the motor. Low-speed, low-inertia three-phase brushless DC motors are easier to control with high precision, achieving a control accuracy within one step. For a six-pole three-phase brushless DC motor, the position equivalent is 10 electrical degrees per step. If the motor has high inertia and cannot stop rotating in the final step, low-voltage power supply and counter-braking can be applied in the last few sectors before reaching the target position.

[0075] Additionally, based on the target sector, the three-phase brushless DC motor is controlled to rotate forward or reverse to the target sector during the next rotation. Specifically, based on the recorded sector S (S=0~5) when the motor stops rotating, the motor rotates forward to the target position: When the motor starts in sector S or S-1, the motor is controlled to rotate forward with UVW power supply, and low voltage (or through PWM modulation) power supply is applied for a relatively long time to induce creep in the motor, turning the static friction of the motor rotation into dynamic friction. If the actual position of the motor is not in sector S, it can be rotated back to its original position, and the initial angle between the stator and rotor magnetic fields of the motor is made as similar as possible. Then, UVW power supply is applied to the motor to rotate forward, so that the initial angle between the stator and rotor magnetic fields of the motor is basically the same each time it starts, so as to achieve precise start-up at the same position (with the stator and rotor magnetic field angle as small as possible). Motor reverses to target position: When the motor starts, in sector S or S+1, the motor is controlled to rotate forward with UVW power supply. Low voltage (or through PWM modulation) power supply is applied for a relatively long time to make the motor creep, so that the static friction of the motor rotation becomes dynamic friction. At the same time, the initial angle between the stator and rotor magnetic fields of the motor rotation is made as similar as possible (the angle between the stator and rotor magnetic fields should be as small as possible) during startup. Then, the motor is reversed with UVW power supply to achieve that the initial angle between the stator and rotor magnetic fields of the motor is basically (as much as possible) the same each time it starts, so as to achieve precise position start.

[0076] It should be noted that the specific power supply time and voltage level (or through PWM modulation) of the first step of low-voltage power supply for motor startup need to be determined based on the actual situation of the motor, motor speed, and motor load, and are not limited here.

[0077] Figure 6 This is a flowchart of a motor speed control method provided in Embodiment 2 of the present invention. Figure 7 This is another flowchart of motor speed control provided in Embodiment 2 of the present invention. Figure 8 This is a flowchart of a motor position control method provided in Embodiment 2 of the present invention. (See reference) Figure 6 , Figure 7 ,and Figure 8 When the actual speed V1 of the motor is less than the given motor speed V0 and / or the actual load N1 of the motor is less than the given motor load N0, the included angle between the stator and rotor magnetic fields increases. The motor is controlled according to the relationship between the current position S1 and the target position S0. For example, when the motor rotates in the forward direction and the positioning completion flag is 1, the start program is called to control the motor to start, thereby controlling the current position of the motor.

[0078] The position control method for a three-phase brushless DC motor provided in this embodiment determines the initial angle between the stator magnetic field and the rotor magnetic field after commutation based on the motor speed and commutation time. If the motor speed increases (or decreases), the initial angle between the stator magnetic field and the rotor magnetic field after commutation is controlled to decrease (or increase). Since a sudden increase (or decrease) in motor load will lead to deceleration (speed increase), the increase (or decrease) in the initial angle will cause the rotor to obtain a larger (or smaller) torque for acceleration (or deceleration), thereby realizing the sensorless return of the three-phase brushless DC motor speed, ensuring uniform motor rotation, and ensuring the reliability of motor position and speed control.

[0079] Example 3

[0080] Figure 9 This is a structural block diagram of a position control device for a three-phase brushless DC motor provided in Embodiment 3 of the present invention. The position control device for the three-phase brushless DC motor includes: a data acquisition module 310, a commutation determination module 320, a position control module 330, a voltage determination module 340, and an information recording module 350. The data acquisition module 310 is used to acquire the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator; the commutation determination module 320 is used to determine the commutation time of the motor stator drive coil based on the zero-crossing time of the back EMF voltage of the drive coil, the preset commutation angle between the stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed; the position control module 330 is used to determine the starting angle of the stator and rotor magnetic field angle after commutation based on the rotor speed and the commutation time, and to record the number of commutations, so as to control the position and speed of the brushless DC motor; the voltage determination module 340 is used to continue to supply power to the motor and determine the energization time and supply voltage based on the stator position and energized stator coil information recorded after the last motor stop when the motor starts; wherein, the first commutation step of motor start-up is the commutation time of the drive coil of the motor stator drive coil. The energizing time is greater than the power supply time of the energized phase during normal motor rotation, causing the rotor to creep and reducing the angle between the stator and rotor magnetic fields. The power supply voltage for the first commutation step is less than the power supply voltage for normal motor rotation. The power supply voltage for the second step and the subsequent n steps is greater than or equal to the power supply voltage for normal motor rotation. The power supply time for the second step and the subsequent n steps is less than the power supply time for the first step but greater than the power supply time for normal motor rotation. The n steps during motor startup are the starting steps, after which the motor rotates normally. The information recording module 350 is used to determine the voltage and energizing time provided to the motor stator coils based on the stator position and energized stator coil information recorded after the last motor stop, and to record the stator position and energized stator coil information. The energizing time is greater than the time required for normal motor rotation.

[0081] Based on the above implementation, the commutation determination module 320 includes: a time determination unit and a commutation determination unit; wherein, the time determination unit is used to determine the sum of the zero-crossing time of the back EMF voltage of the brushless DC motor and the time required for the current step to continue rotating to the commutation angle if commutation is performed when the angle between the stator magnetic field and the rotor magnetic field reaches the commutation angle; the commutation determination unit is used to take the sum of the zero-crossing time of the back EMF voltage and the time required for the current step to continue rotating to the commutation angle as the commutation time point.

[0082] In one embodiment, the position control module 330 includes a commutation control unit and an angle control unit; wherein, the commutation control unit is used to control the current sector where the stator magnetic field and the rotor magnetic field are located to the next commutation step according to the commutation time point; the angle control unit is used to control the starting angle of the next step to decrease according to the rotor speed if the rotor speed increases, and to control the starting angle of the next step to decrease according to the rotor speed if the rotor speed decreases.

[0083] Optionally, the position control device further includes a sector recording module and a motor control module; wherein, the sector recording module is used to record the target sector and the energization information of the motor stator coil corresponding to the stop rotation of the brushless DC motor when it stops rotating, after the position control module 330 determines the starting angle between the stator magnetic field and the rotor magnetic field after commutation; the motor control module is used to control the brushless DC motor to perform forward or reverse rotation in the target sector during the next rotation, based on the target sector.

[0084] Optionally, the position control device further includes a sector recording module and a voltage control module. The sector recording module records the target sector corresponding to the point of complete stop of the brushless DC motor after the position control module 330 determines the initial angle between the stator and rotor magnetic fields following commutation. The voltage control module controls the power supply time of the brushless DC motor to increase based on the target sector, when the brushless DC motor reaches the target sector before its next complete stop. As the power supply time increases, the angle between the stator and rotor magnetic fields of the brushless DC motor approaches 0 degrees, and the brushless DC motor decelerates until it stops.

[0085] The position control device for the three-phase brushless DC motor provided in this embodiment belongs to the same inventive concept as the position control method for the three-phase brushless DC motor provided in any embodiment of the present invention, and has corresponding beneficial effects. For technical details not detailed in this embodiment, please refer to the position control method for the three-phase brushless DC motor provided in any embodiment of the present invention.

[0086] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A position control method for a three-phase brushless DC motor, characterized in that, include: Obtain the zero-crossing time of the back EMF voltage of the drive coil of the unenergized phase of the motor stator; Based on the zero-crossing time of the back EMF voltage of the drive coil, the commutation angle between the preset stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed, the commutation time of the stator drive coil of the motor is determined. Based on the rotor speed and the commutation time point, determine the starting angle of the stator and rotor magnetic field angle after commutation and record the number of commutations to control the position and speed of the brushless DC motor. When the motor starts, based on the stator position and energized stator coil information recorded after the previous motor stop, power is supplied to the motor again, and the energizing time and supply voltage are determined. Specifically, the energizing time for the first commutation step during motor startup is longer than the power supply time for the energized phase during normal motor rotation, causing the rotor to creep and reducing the angle between the stator and rotor magnetic fields. The supply voltage for the first commutation step is less than the supply voltage for normal motor rotation. The supply voltage for the second and subsequent n steps is greater than or equal to the supply voltage for normal motor rotation, and the power supply time for the second and subsequent n steps is less than the power supply time for the first step but greater than the power supply time for normal motor rotation. The n steps during motor startup are the starting steps; after these n steps, the motor rotates normally. When the motor stops rotating, the voltage and energizing time supplied to the motor stator coils are determined based on the stator position and energized stator coil information recorded after the last motor stop, and the stator position and energized stator coil information are recorded; wherein, the energizing time is greater than the time required for the motor to rotate normally; After determining the initial angle between the stator magnetic field and the rotor magnetic field after commutation, the process includes: Record the target sector corresponding to the point where the brushless DC motor stops rotating from its initial rotation to a complete stop; According to the target sector, when the brushless DC motor rotates to the target sector before stopping again, the power supply time of the brushless DC motor is increased; as the power supply time of the brushless DC motor increases, the magnetic field angle between the stator and rotor of the brushless DC motor approaches 0 degrees, and the brushless DC motor decelerates until it stops rotating.

2. The position control method according to claim 1, characterized in that, The step of determining the commutation time of the motor stator drive coil based on the zero-crossing time of the back EMF voltage of the drive coil, the preset commutation angle between the stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed includes: If commutation occurs when the angle between the stator magnetic field and the rotor magnetic field reaches the commutation angle, then the sum of the zero-crossing time of the back EMF voltage of the brushless DC motor and the time required for the current step to continue rotating to the commutation angle is determined. The sum of the zero-crossing time of the back EMF voltage and the time required for the current step to continue rotating to the commutation angle is taken as the commutation time point.

3. The position control method according to claim 2, characterized in that, The step of determining the initial angle between the stator magnetic field and the rotor magnetic field after commutation based on the rotor speed and the commutation time point, and recording the number of commutations, in order to control the position and speed of the brushless DC motor, includes: Based on the commutation time point, control the next commutation of the stator; If the rotor speed increases, the starting angle of the next step is controlled to decrease according to the rotor speed; if the rotor speed decreases, the starting angle of the next step is controlled to increase according to the rotor speed.

4. The position control method according to claim 3, characterized in that, The starting angle range is the range of the included angle between the stator and rotor magnetic fields, which is 60 to 30 degrees.

5. The position control method according to claim 1, characterized in that, After determining the initial angle between the stator magnetic field and the rotor magnetic field after commutation, the process includes: Record the target sector and stator coil energization information corresponding to the stop of rotation of the brushless DC motor from rotation to stop; Based on the target sector, the brushless DC motor is controlled to rotate forward or reverse in the target sector during the next startup.

6. A position control device for a brushless DC motor, characterized in that, include: The data acquisition module is used to acquire the zero-crossing time of the back EMF voltage of the drive coil of the non-energized phase of the motor stator; The commutation determination module is used to determine the commutation time of the motor stator drive coil based on the zero-crossing time of the back EMF voltage of the drive coil, the preset commutation angle between the stator magnetic field and the rotor magnetic field of the motor (less than 60 degrees and greater than 30 degrees), and the rotor speed. The position control module is used to determine the starting angle of the magnetic field angle between the stator and rotor after commutation and record the number of commutations based on the rotor speed and the commutation time point, so as to control the position and speed of the brushless DC motor. The voltage determination module is used to continue supplying power to the motor and determine the energizing time and supply voltage based on the stator position and energized stator coil information recorded after the motor stopped last time when the motor starts. Specifically, the energizing time for the first commutation step of the motor startup is longer than the power supply time for the energized phase during normal motor rotation, so as to induce rotor creep and reduce the angle between the stator and rotor magnetic fields. The supply voltage for the first commutation step is less than the supply voltage for normal motor rotation. The supply voltage for the second step and the subsequent n steps is greater than or equal to the supply voltage for normal motor rotation. The power supply time for the second step and the subsequent n steps is less than the power supply time for the first step but greater than the power supply time for normal motor rotation. The n steps during motor startup are the starting steps, after which the motor rotates normally. The information recording module is used to determine the voltage and energizing time supplied to the motor stator coils based on the stator position and energized stator coil information recorded after the motor stopped rotating, and to record the stator position and energized stator coil information; wherein the energizing time is greater than the time required for the motor to rotate normally; It also includes a sector recording module and a voltage control module. The sector recording module is used to record the target sector corresponding to the stop rotation of the brushless DC motor when it stops rotating, after the position control module determines the initial angle between the stator magnetic field and the rotor magnetic field after commutation. The voltage control module is used to control the power supply time of the brushless DC motor to increase when the brushless DC motor rotates to the target sector before the next stop rotation, based on the target sector. As the power supply time of the brushless DC motor increases, the angle between the stator and rotor magnetic fields of the brushless DC motor approaches 0 degrees, and the brushless DC motor decelerates to stop rotating.

7. The position control device according to claim 6, characterized in that, The commutation determination module includes: The time determination unit is used to determine the sum of the zero-crossing time of the back EMF voltage of the brushless DC motor and the time required for the current step to continue rotating to the commutation angle if commutation is performed when the angle between the stator magnetic field and the rotor magnetic field reaches the commutation angle. The commutation determination unit is used to take the sum of the zero-crossing time of the back EMF voltage and the time required for the current step to continue rotating to the commutation angle as the commutation time point.

8. The position control device according to claim 6, characterized in that, The position control module includes: The commutation control unit is used to control the current sector where the stator magnetic field and rotor magnetic field are located to the next commutation step according to the commutation time point; An angle control unit is used to control the starting angle of the next step to decrease according to the rotor speed if the rotor speed increases, and to control the starting angle of the next step to increase according to the rotor speed if the rotor speed decreases.

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