阅读说明：本技术 一种永磁无刷直流电机转子位置和速度估算方法 (Method for estimating position and speed of permanent magnet brushless direct current motor rotor ) 是由 孙仁科 于 2020-04-13 设计创作，主要内容包括：本发明为一种永磁无刷直流电机转子位置和速度估算方法,公开了一种无位置传感器控制方式下的无刷直流电机的转子位置检测方法,适用于电动机领域,将定子圆周等分为六个扇区,由于定子绕组换向的作用会产生续流,通过检测任意一相的续流结束时的反电势,估算出该相在刚刚经历的那个扇区开始换向位置的时间,如果该相在扇区开始的时候换向时间过早,那么该相在续流结束时检测的反电动势为0,如果该相在扇区开始的时候换向时间迟了,那么续流结束时检测该相的反电势则超过正常范围,通过检测相应相的续流结束时的反电动势的大小,从而估算出对应项的换向时刻的准确程度,进而可以估算出转子相对于该相定子的相对位置信息。可以减少磁场畸变对位置检测的影响,大大提高了转子位置检测的精度。(The invention is a method for estimating position and speed of rotor of permanent magnet brushless DC motor, disclosing a method for detecting position of rotor of brushless DC motor under control mode of no position sensor, suitable for field of motor, equally dividing stator circumference into six sectors, generating follow current due to commutation action of stator winding, estimating time of starting commutation position of sector just passed by any phase by detecting back electromotive force when follow current of any phase is finished, if commutation time of phase at sector is too early, back electromotive force detected by phase at end of follow current is 0, if commutation time of phase at sector is late, back electromotive force detected by phase at end of follow current exceeds normal range, by detecting size of back electromotive force when follow current of corresponding phase is finished, thereby estimating accuracy degree of commutation time of corresponding item, and the relative position information of the rotor relative to the stator of the phase can be estimated. The influence of magnetic field distortion on position detection can be reduced, and the precision of rotor position detection is greatly improved.)

1. A permanent magnet brushless direct current motor rotor position estimation method is characterized by comprising the following steps:

the method comprises the steps of equally dividing the circumference of a stator into six sectors, generating follow currents due to the effect of commutation of a stator winding, estimating the time of the phase at the beginning of commutation position of the just-experienced sector by detecting the magnitude of counter electromotive force of any phase at the end of the follow currents, if the commutation time of the phase at the beginning of the sector is too early, the counter electromotive force of the phase at the end of the follow currents is 0, if the commutation time of the phase at the beginning of the sector is too late, the counter electromotive force of the phase at the end of the follow currents exceeds a normal range, and estimating the accuracy of the commutation time of a corresponding item by detecting the magnitude of the counter electromotive force of the corresponding phase at the end of the follow currents, so that the relative position information of a rotor relative to the stator of the phase can be estimated.

2. The method for estimating the rotor position of the permanent magnet brushless direct current motor according to claim 1, characterized by comprising the following steps:

firstly, acquiring parameter information of a tested motor, wherein the parameter information comprises the number N of turns of a permanent magnet brushless direct current motor winding and an area S enclosed by the magnetic brushless direct current motor winding;

then starting the tested motor, generating a counter electromotive force E in a rotating magnetic field by a stator winding of the tested motor, and utilizing a formula: e is 2NS ω B, and the position of the rotor relative to the stator is calculated by detecting the back electromotive force characteristics of the motor; in the formula: e is counter electromotive force, B is magnetic flux density of an air gap, N is the number of turns of the permanent magnet brushless direct current motor winding, S is the area enclosed by the permanent magnet brushless direct current motor winding, and omega is the electrical angular velocity of the motor rotor;

specifically, the stator circumference is divided into six sectors, when it is detected that the back electromotive force E suddenly changes in a large span in one carrier period, for example, suddenly changes from a maximum value to a minimum value, the follow current is terminated, and the end of the commutation time of one sector of the six sectors divided into the stator circumference is indicated, so as to estimate the commutation time of the last terminated sector and the position of the rotor relative to the stator; if the current back electromotive force E is detected to be less than or equal to 0, the stator commutation time at the beginning of the section which is just passed by the rotor is too early, and the stator energization time delta t of the section needs to be increased so as to delay the stator commutation time point; if the current counter potential E is detected to be larger than or equal to the bus power supply voltage U_dcWhen the current is measured, the commutation time point at the beginning of the section which is just passed by the rotor is too late, and the commutation time point of the rotor needs to be advanced by reducing the stator energization time delta t of the section, wherein a measuring point which the rotor section passes through is a position point at which the counter electromotive force E is greater than 0 or less than the bus power supply voltage Udc;

under the working mode that the direct current motors are electrified pairwise, the suspended corresponding counter electromotive force E of the direct current motors is measured, and the corresponding follow current phase bus power supply voltage U is measured according to the requirement_dcOr the ground line is used as counter potential E, and the counter potential E and the ideal counter potential E are calculated_iThe difference Δ E, using the formula:estimating the actual position theta, theta of the rotor relative to the stator_iFor an ideal rotor position relative to the stator, since the angular velocity ω is constant over a short time, the formula is used:estimated actual and ideal rotor positions theta_iIs, theoretically, the boundary of each sector isIdeal positions, each phase has two ideal positions, the total six positions of the three phases are positions corresponding to 30 degrees, 90 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees respectively,

using the formula:calculating the deviation of the delay and the advance commutation time when the sector starts, wherein the physical meaning of delta t is the time difference between the ideal position and the actual position of the rotor, delta theta is the deviation between the ideal position and the actual position of the rotor relative to the stator, and omega is the electrical angular speed of the motor rotor;

according to the time t of starting reversing of the sector_sAnd a sector end time commutation time t_eUsing the formula: t is_i＝t_e-t_sCalculating the actual reversing time of the sector as T_iI is a sector number, i is (1, 2 … … 6), and since the six electrical angle sectors are 360 ° of a circle, the electrical angular velocity of the rotor of the motor is determinedUsing the formula: t is_ideal＝T_i+ Δ T calculates the ideal sector time T_idealThe ideal sector time T_idealNamely the optimal commutation time of the next sector of the drill, and at the commutation finishing moment, the steps are repeated for repeated iteration, so that the relative position of the rotor and the stator can be continuously calculated.

3. A speed estimation method using the permanent magnet brushless dc motor rotor position estimation method according to claim 1, characterized in that:

the reversing time of the current sector of the stator is subtracted by the starting reversing time of the current sector to calculate the rotating time T of each sector_iI is the sector number, i ═ 1, 2 … … 6, then using the formula:and calculating the electrical angular velocity omega of the motor rotor.

4. The speed estimation method according to claim 3, characterized in that: because the current can not change suddenly, at any commutation moment of six sectors of the stator, afterflow phenomenon always occurs in mosfets of upper and lower bridge arms of any phase of the direct current motor, and the time t when the tested motor starts to commutate is the reverse electromotive force waveform containing the afterflow process₁Generating follow current, detecting that the current counter potential E is the bus power supply voltage Udc by the counter potential detection module, indicating that the current commutating phase is a suspended phase and the phase is in a follow current state, and continuously detecting until the counter potential E is detected to meet the following conditions:the end of the continuous flow is indicated, namely the reversing time t at the end moment of the sector₂The back electromotive force E detected at this time includes the actual position θ and the ideal position θ of the rotor_iPosition information, another freewheel time can be detected similarly: when the counter potential is detected to be 0, the time t is marked as the time t for starting commutation₃Detection is continued until detection of a back electromotive force E satisfyingIs recorded as the sector end time commutation time t₄。

5. A speed estimation method according to claim 3, characterized in that the method of estimating the position of the rotor with respect to each phase based on the magnitude of the back electromotive force E after the end of the continuous flow of the phase comprises:

taking the phase a of the permanent magnet brushless dc motor as an example, it can be seen that when the back electromotive force E of the detected suspended phase a is suddenly changed to the minimum value, indicating that the stator freewheeling of the phase a is just finished, and if the back electromotive force position E1 detected at this time is greater than 0, indicating that E₁The rotor position is located on the right side of the ideal position by 90 deg., and if the detected back electromotive force position is 0 or less, e is indicated₁The rotor position is located at the left side of the ideal position by 90 deg., and similarly, it can be detected that the rotor is located at the ideal position by 270 degThe left side or the right side of the rotor is also used for solving the relative position of the rotor relative to the other two phases of the B phase and the C phase.

Technical Field

The invention relates to a method for estimating the position and the speed of a permanent magnet brushless direct current motor rotor, and belongs to the technical field of permanent magnet brushless direct current motor control.

Background

The brushless direct current motor has the remarkable advantages of wide speed regulation range, high power density, small electromagnetic pollution, reliable operation and the like, and is more and more widely applied to the fields of servo control, electric vehicles, robotics, household appliances and the like. Brushless dc motors typically rely on position sensors mounted inside the motor to detect rotor position, which adds to some degree to the cost of the motor and reduces system reliability. The brushless direct current motor under the control mode without the position sensor has the advantages of high reliability, strong anti-interference capability and the like, and simultaneously overcomes the phase change torque fluctuation caused by inaccurate installation of the position sensor to a certain extent.

Brushless direct current motor rotor position estimation is a hot spot of research on brushless direct current motor control systems. The existing rotor position estimation method mainly utilizes a back electromotive force zero crossing point detection method. However, the method needs to detect the back electromotive force by a fictitious motor midpoint, and needs to delay an electrical angle of 30 degrees after detecting the zero crossing of each back electromotive force to obtain a corresponding phase-change time point, and the zero crossing position at the midpoint has a large limitation, thereby limiting the application range of the brushless direct current motor without the position sensor.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a method for estimating the position and the speed of the rotor of the permanent magnet brushless direct current motor, which has simple steps, can detect the position of the rotor before the position of a zero-crossing point while giving consideration to the follow current time of large current.

In order to realize the defects of the technology, the method for estimating the position of the rotor of the permanent magnet brushless direct current motor is provided, and the method comprises the following steps:

the method comprises the steps of equally dividing the circumference of a stator into six sectors, generating follow currents due to the effect of commutation of a stator winding, estimating the time of the phase at the beginning of commutation position of the just-experienced sector by detecting the magnitude of counter electromotive force of any phase at the end of the follow currents, if the commutation time of the phase at the beginning of the sector is too early, the counter electromotive force of the phase at the end of the follow currents is 0, if the commutation time of the phase at the beginning of the sector is too late, the counter electromotive force of the phase at the end of the follow currents exceeds a normal range, and estimating the accuracy of the commutation time of a corresponding item by detecting the magnitude of the counter electromotive force of the corresponding phase at the end of the follow currents, so that the relative position information of a rotor relative to the stator of the phase can be estimated.

2. The method for estimating the rotor position of the permanent magnet brushless direct current motor according to claim 1, characterized by comprising the following steps:

firstly, acquiring parameter information of a tested motor, wherein the parameter information comprises the number N of turns of a permanent magnet brushless direct current motor winding and an area S enclosed by the magnetic brushless direct current motor winding;

then starting the tested motor, generating a counter electromotive force E in a rotating magnetic field by a stator winding of the tested motor, and utilizing a formula: e is 2NS ω B, and the position of the rotor relative to the stator is calculated by detecting the back electromotive force characteristics of the motor; in the formula: e is counter electromotive force, B is magnetic flux density of an air gap, N is the number of turns of the permanent magnet brushless direct current motor winding, S is the area enclosed by the permanent magnet brushless direct current motor winding, and omega is the electrical angular velocity of the motor rotor;

specifically, the stator circumference is divided into six sectors, when it is detected that the back electromotive force E suddenly changes in a large span in one carrier period, for example, suddenly changes from a maximum value to a minimum value, the follow current is terminated, and the end of the commutation time of one sector of the six sectors divided into the stator circumference is indicated, so as to estimate the commutation time of the last terminated sector and the position of the rotor relative to the stator; if the current back electromotive force E is detected to be less than or equal to 0, the stator commutation time at the beginning of the section which is just passed by the rotor is too early, and the stator energization time delta t of the section needs to be increased so as to delay the stator commutation time point; if the current counter potential E is detected to be larger than or equal to the bus power supply voltage U_dcAt that time, it is said that the immediately past sector of the rotor beginsWhen the commutation time point is too late, the commutation time point of the rotor needs to be advanced by reducing the stator energization time delta t of the sector, wherein a measuring point passed by the rotor sector is a position point where the back electromotive force E is greater than 0 or smaller than the bus power voltage Udc;

under the working mode that the direct current motors are electrified pairwise, the suspended corresponding counter electromotive force E of the direct current motors is measured, and the corresponding follow current phase bus power supply voltage U is measured according to the requirement_dcOr the ground line is used as counter potential E, and the counter potential E and the ideal counter potential E are calculated_iThe difference Δ E, using the formula:estimating the actual position theta, theta of the rotor relative to the stator_iFor an ideal rotor position relative to the stator, since the angular velocity ω is constant over a short time, the formula is used:estimated actual and ideal rotor positions theta_iTheoretically, the boundary of each sector is an ideal position, each phase has two ideal positions, and the total six positions of the three phases are positions corresponding to 30 degrees, 90 degrees, 120 degrees, 180 degrees, 240 degrees and 300 degrees respectively,

using the formula:calculating the deviation of the delay and the advance commutation time when the sector starts, wherein the physical meaning of delta t is the time difference between the ideal position and the actual position of the rotor, delta theta is the deviation between the ideal position and the actual position of the rotor relative to the stator, and omega is the electrical angular speed of the motor rotor;

according to the time t of starting reversing of the sector_sAnd a sector end time commutation time t_eUsing the formula: t is_i＝t_e-t_sCalculating the actual reversing time of the sector as T_iI is a sector number, i is (1, 2 … … 6), and since the six electrical angular sectors are 360 ° of a circle, the electrical angular speed of the rotor of the motor is increasedDegree of rotationUsing the formula: t is_ideal＝T_i+ Δ T calculates the ideal sector time T_idealThe ideal sector time T_idealNamely the optimal commutation time of the next sector of the drill, and at the commutation finishing moment, the steps are repeated for repeated iteration, so that the relative position of the rotor and the stator can be continuously calculated.

A speed estimation method of a permanent magnet brushless direct current motor rotor position estimation method comprises the following steps:

the reversing time of the current sector of the stator is subtracted by the starting reversing time of the current sector to calculate the rotating time T of each sector_iI is the sector number, i ═ 1, 2 … … 6, then using the formula:and calculating the electrical angular velocity omega of the motor rotor.

Because the current can not change suddenly, at any commutation moment of six sectors of the stator, afterflow phenomenon always occurs in mosfets of upper and lower bridge arms of any phase of the direct current motor, and the time t when the tested motor starts to commutate is the reverse electromotive force waveform containing the afterflow process₁Generating follow current, detecting that the current counter potential E is the bus power supply voltage Udc by the counter potential detection module, indicating that the current commutating phase is a suspended phase and the phase is in a follow current state, and continuously detecting until the counter potential E is detected to meet the following conditions:the end of the continuous flow is indicated, namely the reversing time t at the end moment of the sector₂The back electromotive force E detected at this time includes the actual position θ and the ideal position θ of the rotor_iPosition information, another freewheel time can be detected similarly: when the counter potential is detected to be 0, the time t is marked as the time t for starting commutation₃Detection is continued until detection of a back electromotive force E satisfyingIs recorded as the sector end time commutation time t₄。

The method for estimating the position of the rotor relative to each phase according to the magnitude of the back electromotive force E after the continuous flow of each phase is as follows:

taking the phase a of the permanent magnet brushless dc motor as an example, it can be seen that when the back electromotive force E of the detected suspended phase a is suddenly changed to the minimum value, indicating that the stator freewheeling of the phase a is just finished, and if the back electromotive force position E1 detected at this time is greater than 0, indicating that E₁The rotor position is located on the right side of the ideal position by 90 deg., and if the detected back electromotive force position is 0 or less, e is indicated₁The rotor position is located on the left side of the ideal position by 90 degrees, and similarly, whether the rotor is located on the left side or the right side of the ideal position by 270 degrees can be detected, and the relative positions of the rotor with respect to the other two phases, phase B and phase C, can be obtained by the same method.

Has the advantages that: the invention can detect the position of the rotor in advance before the zero crossing point detection by detecting the follow current time and the back electromotive force, provides sufficient time for commutation and field weakening control, and ensures the performance of the motor. The position of the rotor can be detected before the zero-crossing position while the follow current time of large current is considered, and the possibility is provided for flux weakening control and advanced commutation.

Drawings

FIG. 1 is an air gap flux density distribution trapezoidal wave of the present invention;

FIG. 2 is a block diagram of the present invention for estimating rotor position and speed through back emf detection;

FIG. 3 is a schematic diagram of back emf detection of the present invention;

FIG. 4 is a schematic view of the rotor position calculation of the present invention.

The specific implementation mode is as follows:

the invention is further explained below with reference to the drawings.

The invention relates to a position and speed estimation method of a permanent magnet brushless direct current motor rotor, which is applied to a brushless position-sensorless motor control system;

the three phases of the motor have symmetry, only phase A is analyzed, phase B and phase C are similar, as shown in fig. 3, when the phase A winding is located near 90 degrees of the ideal position in the plane space, the positions of two magnetic poles of rotor N and S can be detected, and the principle is to detect the back electromotive force waveform of N or S passing through winding A, and then judge the position of the rotor.

The distribution waveform of the no-load air gap magnetic flux density B of the brushless motor is close to a trapezoidal wave, as shown in figure 1, and as shown in figure 2 according to the waveform of formula I, and as shown in figure 3, a follow current phenomenon can be generated in the stator commutation overshoot, the position of the rotor relative to the stator can be calculated by detecting the characteristics of the back electromotive force of the motor;

E＝2NSωB Ⅰ，

can calculate the counter electromotive force E, wherein E is the counter electromotive force, N is the number of turns of the permanent magnet brushless direct current motor winding, S is the area enclosed by the permanent magnet brushless direct current motor winding, omega is the electrical angular velocity of the motor rotor,

specifically, it is necessary to detect the magnitude of the back electromotive force E in each cycle of the carrier, and when an abrupt change in the magnitude of the back electromotive force E is detected (the value suddenly changes from the maximum value (minimum value) to the value close to the minimum value (maximum value) in one carrier cycle), the end of the free-wheeling is described, and the end of the commutation time of one sector is also described (theoretically, a 360 ° circle is divided into six sectors). The magnitude of the back emf E detected at this time can estimate the accuracy of the commutation start time of the just completed sector, and thus the position of the rotor relative to the stator.

When the current counter electromotive force E is detected to be less than or equal to 0, the stator commutation time at the beginning of the immediately past sector is too early, the commutation time point of the rotor needs to be delayed, if the counter electromotive force E is greater than or equal to the bus power voltage U_dcWhen the rotor is in the middle of the sector, the time point of the rotor is needed to be changed; since the time of passage of a sector is proportional to the length of the sector at the same speed, the delay and advance of the commutation time points translates into a problem of delay and advance of the rotor with respect to the stator position, the rotor delay time Δ t and the advanced positionThe detailed calculation method of Δ θ is as follows:

as shown in fig. 4, the back electromotive force E of the corresponding free-wheeling phase is measured, and the back electromotive force E and the ideal back electromotive force E are calculated_iAnd the difference delta E is obtained by utilizing a formula II to estimate the actual position theta of the rotor relative to the three-phase ideal position of the stator, and the angular speed omega is constant in a short time, so that the actual position theta and the ideal position theta of the rotor can be estimated according to a formula III_iThe deviation delta theta of the sector, using equation iv, can be calculated as the deviation of the delay and advance commutation time at the beginning of the sector. (ii) a According to the time t of starting reversing of the sector_sAnd a sector end time commutation time t_eCalculating the actual reversing time of the sector as Ti by using a formula IV, and calculating the ideal sector time T by using a formula VI according to the formula IV and the formula V_idealThe ideal sector time T_idealThat is the required commutation time for the next sector, which uses this time T_idealAnd (4) reversing, and repeating iteration according to the process at the moment of finishing reversing to continuously calculate the relative position of the rotor and the stator.

Theta is the actual position of the rotor relative to the ideal three-phase position of the stator, theta_iThe ideal rotor position relative to the stator (theoretically, the boundary of each sector is the ideal position, each phase has two ideal positions, and the total six positions of the three phases are the positions corresponding to 30 °, 90 °, 120 °, 180 °, 240 ° and 300 °, respectively), Δ E is the difference between the measured back electromotive force and the ideal back electromotive force, and Udc is the bus supply voltage.

Δ t time difference between ideal position and actual position of rotor, Δ θ is deviation between ideal position and actual position of rotor relative to stator, and ω is electrical angular velocity of motor rotor

T_i＝t_e-t_sⅤ

te is the time of the ending time of the sector, ts is the time of the starting time of the sector, and Ti is the time occupied by the ith sector

T_ideal＝T_i+Δt Ⅵ

From the above description, the time T of each sector can be calculated_iI represents a sector number, six sectors are provided, the time used by one sector is calculated by subtracting the moment when the sector starts to commutate from the moment when the sector ends, and the electrical angular speed omega of the motor can be calculated according to the formula VII because the six sectors in electrical angle are 360 DEG of a circle.

Omega is the electrical angular velocity, T, of the rotor of the motor_iDetecting a freewheel time T for the time used by the i-th sector_xThe method comprises the following steps: because the current can not change suddenly, the follow current phenomenon always occurs at any commutation moment, as shown in fig. 3, which illustrates the waveform of the A-phase back electromotive force containing the follow current process, when the A-phase winding is positioned near the ideal position 90 DEG in the plane space, the positions of two magnetic poles of the rotor N and S can be detected, the principle is to detect the back electromotive force waveform of the N or S passing through the winding A, further judge the position of the rotor, and at the moment t of starting commutation of the tested motor, the follow current phenomenon always occurs₁The upper bridge arm of the phase A generates a follow current phenomenon, and the counter potential detection module detects that the current counter potential E is the bus power supply voltage U_dcExplaining that the item A is in a follow current state at present, continuously detecting the counter electromotive force E of the phase A until the moment t is detected₂At this time, the counter potential E of the phase A satisfies the following condition,the end of the continuous flow state of the phase A is explained, and the detected back electromotive force E of the phase A comprises the rotationActual position theta of the stator relative to the A-phase stator and ideal position theta of the rotor_iPosition information, and likewise a further freewheel time, i.e. at the commutation time t₃Detecting until the time t⁴The counter potential E at that moment satisfies

As shown in fig. 4, taking phase a as an example, it is understood that when the back electromotive force E of the floating phase a is detected to be suddenly low, it indicates that the stator freewheeling of phase a is just finished, and if the back electromotive force position E1 at this time of detection is greater than 0, it indicates that the rotor position at E1 is located on the right side of the ideal position 90 °, and if the detected back electromotive force position is equal to or less than 0, it indicates that the rotor position at E1 is located on the left side of the ideal position 90 °.

After the 90-degree position of the flywheel is finished, the counter potential is detected to be E1, if E1 is greater than or equal to 0, the rotor is positioned on the right side of the 90-degree ideal position of the A phase, and delta E is equal to E1 and theta is equal to theta_iThe rotor position can be calculated according to formula II at 90 DEGIf e1 is less than or equal to 0, indicating that the rotor is on the left side of phase a,T_iis a sector of time. Similarly, the position of the rotor near the ideal position of 270 DEG can be calculated6 andthe same applies to determining the position of the rotor relative to the other two phases, i.e. to determine θ_30°，θ_90°，θ_150°，θ_210°，θ_270°，θ_330°And simultaneously calculating the time of each sector, and recording as T₁，T₂，T₃，T₄，，T₅

Calculating the speed of the rotor, calculating the electrical angular speed omega of the rotor according to the formula VII,

the relative ideal positions of the rotor in the B phase and the C phase can be obtained by the same method.