JP5418769B2 - Method for estimating electric angle of brushless motor and brushless motor - Google Patents

Description

  The present invention relates to a method for accurately estimating an electrical angle used when calculating PWM and a brushless motor capable of accurately estimating the electrical angle.

  In recent years, in the fields of electric equipment and electric vehicles, miniaturization and improvement in efficiency of a motor that is a power source are one of the important issues in order to reduce power consumption and downsize devices. There are various types of small motors. In particular, brushless motors are often used in office automation equipment because of their low noise and long life.

  In the brushless motor, a permanent magnet is used for its rotor, and a coil that is excited by applying a multiphase drive voltage is disposed on the stator. Therefore, when applying the driving voltage in multiple phases, it is necessary to grasp the relative position of the rotor with respect to the stator. A sensor using a Hall element is generally used as a sensor for detecting the position of the rotor. The Hall element is a magnetic sensor that has the effect of discriminating the strength of the magnetic field and the magnetic pole. By arranging the Hall element along the direction of rotation, the rotational position of the rotor necessary for multi-phase switching of the drive voltage can be determined. Can be detected.

Further, the brushless motor controls the current flowing in the coil that generates the magnetic field by PWM in order to control the rotation of the rotor. When the current value is obtained, the rotation angle of the rotor, that is, the electrical angle is used as one of the parameters.
In particular, a motor for driving a photoconductor of an image forming apparatus requires high-precision rotation control (for example, rotation accuracy of about several percent), and an accurate electrical angle is also calculated in PWM calculation for controlling rotation. Estimation is desirable.

As a method for obtaining the electrical angle, a method of installing a high resolution encoder and estimating a rotation angle of the rotor, that is, an electrical angle based on a detection result of the high resolution encoder is generally used.
In addition to this, a method (such as a Kalman filter estimation method) for calculating an electrical angle by a statistical method using a change in induced voltage generated in a coil when the rotor rotates is known.

  In addition, the phase difference corresponding to the electrical angle of the rotor and the cycle of the position sensor and the voltage phase command are stored in the ROM as calculation parameters, and the count cycle is determined based on the change cycle of the position sensor. There has been proposed an apparatus capable of reading the count value of the time counter, reading the calculation parameter corresponding to the count value from the ROM, and calculating the voltage phase by calculation (see Patent Document 1). The current flowing through the coil is determined by determining the voltage phase.

JP-A-9-74790

However, the method using a high-resolution encoder for estimating the electrical angle requires an expensive high-resolution encoder, resulting in a problem that the motor cost increases, and there is a space for mounting the encoder. There is also a problem that it becomes necessary and becomes an obstacle to miniaturization.
In addition, in the method of obtaining the electrical angle by the calculation of the statistical method using the induced voltage of the coil, a complicated calculation processing function is required, so it is necessary to provide an expensive calculation device, and the cost increases. There's a problem. Moreover, a space for installing this arithmetic unit is necessary, which is an obstacle to miniaturization. Furthermore, the multipole structure of magnetic poles found in small motors has a problem in accuracy of calculation results because the time for the magnetic poles to pass through one sector is extremely short. For example, in the case of a three-phase DC brushless motor having 16 poles and a rotational speed of 3000 rpm, one cycle of the electrical angle is 1/3000 rpm / 60 sec / (16 pole / 2) / 6 sector = 1.157e-7 sec. When performing vector control, it is necessary to perform angle correction further divided with respect to this time, and it is difficult to obtain a highly accurate result by the above calculation.

  Furthermore, the voltage phase calculation method disclosed in Patent Document 1 assumes that the voltage phase changes linearly with time, and it is difficult to satisfy this condition unless the motor is a fairly expensive motor. is there. Actually, when the motor load fluctuates, rotation may be uneven particularly in a small motor, so that it is difficult to satisfy the above linear relationship and it is not suitable for practical use.

  The present invention has been made to solve the above problems, and accurately estimates the electrical angle of a brushless motor at a low cost by using functions essential to the configuration of the motor without requiring a high-resolution encoder. It is an object of the present invention to provide a method of estimating an electrical angle that can be performed and a brushless motor capable of performing rotation control with high accuracy by the estimation.

That is, the brushless motor of the present invention in an electric angle estimation method, an electrical angle used for the operation of the PWM drive voltage for rotating the rotor at a target rotational speed, the PWM drive voltage of lube Rashiresumota be estimated by using the period of the An electrical angle estimation method ,
The rotation angle at which the rotor rotates at the target rotation speed during one period in the PWM drive voltage is set as a reference electrical angle resolution,
Using the duty of the PWM drive voltage when the rotor is rotating, the estimated passing time for the rotor to rotate through the one or more sectors at the duty is calculated, and the estimated passage A correction electric angle resolution obtained by correcting the reference electric angle resolution using the number of repetitions and the rotation angle over one or more sectors is obtained by determining the number of repeatable cycles in the PWM drive voltage within a time. The electrical angle is calculated using the corrected electrical angle resolution .
In another method of estimating the electrical angle of a brushless motor according to the present invention, the brushless motor that estimates the electrical angle used for the calculation of the PWM drive voltage for rotating the rotor at the target rotational speed using the period of the PWM drive voltage. An electrical angle estimation method of
The rotation angle at which the rotor rotates at the target rotation speed during one period in the PWM drive voltage is set as a reference electrical angle resolution,
Using the duty of the PWM drive voltage when the rotor is rotating, the theoretical reference average duty required to obtain the target rotation speed and the average when the rotor is rotating A corrected electrical angle resolution obtained by correcting the reference electrical angle resolution is calculated based on a deviation from a duty, and the electrical angle is estimated using the corrected electrical angle resolution.

The brushless motor of the present invention includes a rotor having a plurality of magnetic poles formed of permanent magnets, a stator having a plurality of coils excited by application of a driving voltage, and a relative relationship between the rotor and the stator. A rotor position detection sensor for detecting a correct position, a drive circuit for applying a multi-phase PWM drive signal using a PWM carrier to the coil, a rotation speed detector for detecting the rotation speed of the rotor, A current detector for detecting a current value energized in the coil;
A controller for controlling the rotation of the rotor,
The controller determines an excitation sequence including a plurality of sectors in response to a detection result of the rotor position detection sensor, and the rotor rotates at the target rotation speed during one period of the PWM drive voltage. Using the rotation angle as the reference electrical angle resolution and the duty of the PWM drive voltage when the rotor is rotating, the rotor is estimated to pass through the one or more sectors at that duty. A passing time is calculated, a number in which the period of the PWM drive voltage can be repeated within the estimated passing time is determined, and the reference electrical angle is calculated using the number of repetitions and a rotation angle over one or more sectors. resolution calculates a correction electrical angle resolution has been corrected, estimating the electrical angle of the rotor by using the correction electrical angle resolution, at least the rotational speed detection A command signal for generating the PWM drive voltage according to a target rotation speed of the rotor in response to a detection result of the detector and the current detector, using the electrical angle, and calculating the command signal in the drive circuit It is characterized by transmitting to.
Another brushless motor of the present invention includes a rotor having a plurality of magnetic poles formed of permanent magnets, a stator including a plurality of coils excited by application of a driving voltage, and the rotor with respect to the stator. A rotor position detection sensor for detecting a relative position, a drive circuit for applying a multi-phase PWM drive signal using a PWM carrier to the coil, and a rotation speed detector for detecting the rotation speed of the rotor; A current detector for detecting a current value passed through the coil;
A controller for controlling the rotation of the rotor,
The controller determines an excitation sequence including a plurality of sectors in response to a detection result of the rotor position detection sensor, and the rotor rotates at the target rotation speed during one period of the PWM drive voltage. Based on the deviation between the theoretical reference average duty required to obtain the target rotation speed and the average duty when the rotor is rotating, with the rotation angle as the reference electrical angle resolution, the reference Correcting the electrical angle resolution to calculate a corrected electrical angle resolution, estimating the electrical angle of the rotor using the corrected electrical angle resolution,
A command signal for generating the PWM drive voltage according to a target rotation speed of the rotor in response to detection results of at least the rotation speed detector and the current detector is calculated using the electrical angle, and the command A signal is transmitted to the driving circuit.

  According to the present invention, the position of the rotor with respect to the stator is detected by the rotor position detection sensor, and the excitation sequence including a plurality of sectors is determined by the control unit based on the detection result. Further, the control unit estimates the electrical angle of the rotor by using the period in the PWM drive voltage, thereby performing an operation for generating the PWM drive voltage without providing a special component such as a high-precision encoder in the motor. It can be carried out. As a result, the difference between the actual electrical angle and the estimated electrical angle can be minimized, and highly accurate rotation control is possible.

The PWM drive voltage is generated using a PWM carrier having a predetermined frequency in the drive circuit based on a command signal calculated by the control unit of the motor. That is, since the cycle of the PWM carrier is directly taken over as the cycle in the PWM drive voltage, the control unit can use the cycle parameter already used for control without preparing the cycle of the PWM drive voltage as a special parameter. it can. Therefore, the electrical angle can be estimated without requiring a complicated arithmetic processing function, that is, an expensive arithmetic processing device.
As a method for estimating the electrical angle using a specific period, it is conceivable to use a timer period. However, in this case, it is necessary to specially prepare a timer, resulting in an increase in cost, and there is a problem that a high-functional computing means is required for installing the timer. On the other hand, the present invention has a special advantage over the timer in that the electrical angle can be estimated without requiring a special component by using the period of the PWM drive voltage used for PWM control. Have.

  The duty of the PWM drive voltage is determined by the control unit so that a desired current is obtained in the coil provided in the stator. For example, the duty is set according to the rotational position (electrical angle) of the rotor so that a sine wave current flows through the coil. Therefore, it is possible to accurately control the rotation of the rotor by accurately estimating the electrical angle.

  The PWM drive voltage is a signal obtained by modulating the width of a pulse. The pulse repeats within a position corresponding to the pulse width at regular intervals, and rising and falling edges appear. Therefore, the use of the period of the PWM drive voltage is facilitated by using the edge, particularly the reference edge appearing at a constant period interval, for the timing of estimating the electrical angle.

  Further, the electrical angle can be estimated more accurately by including the electrical angle resolution as a parameter. Therefore, the rotation control of the motor can be more accurately performed by appropriately grasping the electrical angle resolution regardless of the rotation speed of the motor or the state of the load. In the present invention, the electrical angle can be estimated by obtaining the electrical angle resolution using the period in the PWM drive voltage. A known method can be employed for estimating the electrical angle using the electrical angle resolution as a parameter. In determining the electrical angle resolution, the edge of the PWM drive voltage can be used for timing. As a result, the electrical angle is estimated using the edge of the PWM drive voltage as the timing.

  As the electrical angle resolution, a rotation angle at which the rotor rotates at a target rotation speed during one cycle of the PWM drive voltage can be used. The period can be easily grasped by the edge of the PWM drive voltage, and the electrical angle resolution can be easily known by detecting the edge or the like. The electrical angular resolution can be determined on the assumption that the motor rotates ideally with no load fluctuation, and can be positioned as the reference electrical angular resolution.

The reference electrical angle resolution can be calculated using the following equation, where N is the number of rotations of the rotor at the target rotation speed and T is the period of the PWM drive voltage.
Reference electrical angle resolution = 2π / ((1 / N) / T)

The reference electrical angle resolution can be calculated in one or more sector units of the excitation sequence. In this case, the number of rising or falling edges of the pulse of the PWM drive voltage is determined while one or more sectors of the excitation sequence are switched, and the rotor rotates to the target rotational speed between the number of edges and the switching. The reference electrical angle resolution is calculated using the rotation angle that is rotated by.
For this reason, the period of the PWM drive voltage is 1 / m times the time that the rotor passes one or more sectors at the target rotational speed so that good reproducibility is obtained (m is an integer greater than or equal to 1). It is desirable to set so that The period in the PWM drive voltage can be set by adjusting the frequency of the PWM carrier, and it is desirable to adjust the frequency of the PWM carrier so as to satisfy the above relationship.

  The control unit receives at least the rotation speed and the current value energized to the coil as a detection result by feedback control, and performs PWM so as to maintain the target rotation speed by P control, PI control, PD control, PID control, or the like. Perform the operation. Thereby, elimination of periodic rotation fluctuations and energization control according to the load are performed. However, when the load fluctuates in a short time, such as when the photosensitive drum of the image forming apparatus is driven, it is difficult to follow in a short time with normal feedback control, resulting in uneven rotation. In addition, it is difficult to perform highly accurate rotation control with normal feedback control.

  Therefore, in another embodiment of the present invention, the electrical angle is estimated based on the corrected electrical angle resolution obtained by correcting the reference electrical angle resolution based on the change in the PWM drive voltage when the rotor is rotating. Since the PWM drive voltage is quickly adjusted according to the rotational speed, the current supplied to the coil, etc., the motor drive state can be easily and immediately grasped by the change in the PWM drive voltage. By correcting the electrical angle resolution based on the change in the PWM drive voltage, it is possible to perform highly accurate rotation control according to the drive state of the motor.

The change in the PWM drive voltage can be determined based on the theoretical PWM drive voltage determined to obtain the target rotation speed, and in particular, the change in the duty of the PWM drive voltage is regarded as the change in the PWM drive voltage. be able to.
The corrected electrical angle resolution can be calculated by correcting the reference electrical angle resolution in accordance with the change in duty. A change in duty can be easily grasped by a change in average duty over one or more sectors.
For example, assuming that the duty of the PWM drive voltage when the rotor rotates is A, the theoretical reference duty of the PWM drive voltage required to obtain the target rotational speed is B, and the reference electrical angle resolution is θrs, The corrected electrical angle resolution can be calculated from the equation.
Corrected electrical angle resolution = A / B × θrs

  The PWM drive voltage is generated in the drive circuit based on a command signal created in the control unit so as to obtain a predetermined duty. Therefore, the information on the duty of the PWM drive voltage to be observed for change can be easily acquired by the control unit. The change of the duty is to obtain an average duty in the same sector before n periods of one or two or more sectors (n is an integer of 1 or more) capable of deriving the reference electrical angle resolution using the period of the PWM drive voltage. Can be obtained. This past duty can be used for calculation by storing it in a storage unit such as a RAM provided in the control unit and reading it out as necessary. The reference duty is obtained by calculating a theoretical average duty of one or more sectors from which a reference electrical angle resolution can be derived.

  The derivation of the corrected electrical angle resolution can also be performed by the following method. That is, based on the changed duty, the time for the rotor to pass through a predetermined sector or two or more sectors is estimated, the number of repeatable periods of the PWM drive voltage within this time is counted, and the range of the sector The corrected electrical angle resolution can be calculated by dividing the angle by the count number. Since the estimated passage time changes according to a change in duty, the corrected electrical resolution is appropriately corrected according to the operating state of the motor.

  The present invention can be applied to a brushless motor in various applications and is not limited to a specific application. However, the image forming apparatus (especially a photosensitive drum) that requires highly accurate rotation control is particularly applicable. Remarkably useful in driving.

  As described above, according to the present invention, it is possible to easily and accurately estimate the electrical angle of a permanent magnet type multiphase brushless motor without using a new mechanism by using the period in the PWM drive voltage. it can. Moreover, even if the set rotational speed and load are different, the electrical angle can be estimated with high accuracy at low cost, and a small high-precision brushless motor with low cost and low power consumption can be obtained.

It is a control block diagram of one embodiment of the present invention. Similarly, it is a circuit diagram of a brushless motor. Similarly, it is a figure which shows schematic structure of a brushless motor. Similarly, it is a figure which shows the coordinate system which shows the detection result of the Hall element which is a rotor position detection sensor in the case of 120 degree | times electricity supply, the flow direction of the electric current of each phase, and sector switching. Similarly, it is a figure which shows the detection result of the Hall element which is a rotor position detection sensor, and the repetition of the PWM drive voltage pulse of a fixed period. Similarly, it is a figure which shows the count procedure of the repetition number of the period in a PWM drive voltage. Similarly, it is a flowchart showing a procedure of PWM calculation using the estimated electrical angle. Similarly, it is a flowchart which shows the estimation procedure of an electrical angle. Similarly, it is a vector diagram showing Clark conversion in PI control. Similarly, it is a vector diagram showing Park conversion in PI control.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a control block of the brushless motor, FIG. 2 shows a circuit diagram of the brushless motor, and FIG. 3 shows a schematic structure of the brushless motor.

  The brushless motor 1 has a rotor 3 in which a plurality of magnetic poles 2a and 2b are formed by permanent magnets, and a plurality of iron cores are disposed so as to face the magnetic poles of the rotor 3, and a coil 4 is wound around the iron core. A fixed stator 5 is arranged. In this example, for the sake of convenience, four magnetic poles and six stator iron cores are illustrated, but these numbers are not particularly limited in the present invention.

  Further, in the brushless motor 1, three hall elements Hu, Hv, Hw are arranged at intervals of 120 degrees along the rotation direction of the rotor 3, and the rotor according to the present invention is provided by the hall elements Hu, Hv, Hw. A position detection sensor is configured. In the present invention, the type of the rotor position sensor is not limited to the Hall element, but a magnetic sensor such as a Hall element is suitable in consideration of the installation space of the sensor.

  Further, in the figure, the stator 5 is shown as being arranged on the outer peripheral side of the rotor 3, but the arrangement relationship is not particularly limited, and the stator is on the inner peripheral side, The rotor may be located on the outer peripheral side, or the stator and the rotor may be arranged so as to face each other in a plane with an interval in the axial direction.

  In the brushless motor 1, the coils 4 are connected in three phases by delta connection or star connection (star connection in the figure), and a drive circuit 10 is connected as shown in FIG. The drive circuit 10 has a bridge circuit 12 so that a drive current is supplied to the coil 4 by switching in three phases of U phase, V phase, and W phase. The bridge circuit 12 includes a number of transistors corresponding to the number of iron cores, and is configured by a full bridge circuit, a half bridge circuit, or the like. A known configuration can be employed for the bridge circuit 12.

  FIG. 1 shows a control block of a brushless motor, and a control unit 20 that controls the brushless motor 1 is connected so as to send a command signal to the drive circuit 10. In the brushless motor 1, a rotation speed detector 6 that detects the rotation speed of the motor is arranged, and the detection result of the rotation speed detector 6 and the detection results of the Hall elements Hu, Hv, and Hw are input to the control unit 20. Has been. In addition, a current detector 7 is provided for detecting the current supplied to the coil 4 as the U phase, V phase, and W phase from the drive circuit 10, and the detection result of the current detector 7 is input to the control unit 20. Has been.

The control unit 20 receives the detection results of the Hall elements Hu, Hv, and Hw, determines the sector position of the excitation sequence, switches the energization of the U phase, the V phase, and the W phase so as to obtain the excitation sequence, and rotates. In response to the detection results of the speed detector 6 and the current detector 7, an operation is performed so that the rotation of the rotor 3 becomes the target rotation number, and a command signal is generated. In this example, PI control is performed in response to the rotation speed and the current detection result.
Further, in the above calculation, the estimated electrical angle is used as a parameter, and in the estimation of the electrical angle, the electrical angle resolution is used as a parameter.

The drive circuit 10 includes a PWM circuit 11 that generates a PWM drive voltage, and a PWM drive voltage is generated using a PWM carrier having a predetermined frequency based on the command signal. It is desirable for the control unit 20 to be able to adjust the frequency of the PWM carrier.
In the bridge circuit 12, the switch is switched according to the PWM drive voltage generated by the PWM circuit 11, and a current flows through the coil 4 of each phase. The coils 4 of each phase generate a magnetic field when current flows. Then, the rotor 3 formed of a permanent magnet rotates at a target rotation speed under the action of the magnetic field of the coil.

  Next, the method for estimating the electrical angle of the brushless motor of the present invention and the operation of the brushless motor including the method will be specifically described below.

First, the control unit 20 determines the excitation sequence in response to the detection results of the Hall elements Hu, Hv, and Hw.
FIG. 4A shows the detection result of each Hall element Hu, Hv, Hw and the direction of the current flowing through the coil 4 every time the position of the rotor 3 rotates by 60 ° with reference to the U phase. An excitation sequence during energization is shown.

When energized at 120 degrees, the hall elements Hu, Hv, and Hw output Hi and Lo every 180 degrees with a phase difference of 60 degrees as the rotor 3 rotates. Therefore, the control unit 20 determines an excitation sequence for switching energization every time the rotor rotates 60 degrees based on the output results of the Hall elements Hu, Hv, and Hw. By including this switching command in the command signal, the bridge circuit 12 operates and switches energization. As a result, as shown in the figure, the direction of the current flowing through the coils of each phase is switched, and the sector of the excitation sequence is determined.
By this excitation sequence, for example, sector 1 is in the state where the signal from the Hall element is (101) and is ON in the U-phase and W-phase and OFF in the V-phase. Current flows. The direction of current flows from the V-phase to the U-phase and from the V-phase to the W-phase. Is done.

In the case of 120-degree energization, the current vectors of the U, V, and W phases are determined in accordance with the detection timings of the Hall elements Hu, Hv, and Hw as described above. On the other hand, in the vector control using the electrical angle, the position of the rotor is estimated by the electrical angle, and the current vectors of the U, V, and W phases are determined.
In this embodiment, vector control is used. FIG. 4B shows the relationship between the electrical angle of the rotor in vector control and the output vector of each phase of U, V, and W. For example, in the case of sector 1, the current vector is calculated from the position of the rotor. , U phase: -Vdd, V phase: Vdd, W phase: -Vdd.
In the vector control, the rotor position is estimated in the range of 0 to 60 degrees between each sector, and based on the current value of each phase, the PI control for the target / position, and then the inverse Clarke / park conversion. Based on the calculated voltage vector, Space Vector conversion is performed to control the ON / OFF pattern of each phase of U, V, and W. In this embodiment, Hall elements Hu, Hv, and Hw signals are used to determine each sector. In this embodiment, the position of the rotor is estimated by using the edge of the PWM carrier signal in the range of 0 to 60 degrees, for example, and the edge signal counter is cleared at the switching of sector 1. The electrical angle may be estimated every 360 degrees. In this case, only the edge counter of sector 1 need be cleared.

Next, the procedure for obtaining the reference electrical angle resolution for estimating the electrical angle will be described with reference to FIG.
In this figure, signals from the Hall elements Hu, Hv, Hw in the brushless motor 1 and pulses of the PWM drive voltage are shown.
In this example, the period of the PWM drive voltage is set to have a relationship of 1 / m times (m is an integer equal to or greater than 1) the time for passing through one sector. Show.

The PWM drive voltage is a pulse with a fixed period, and the number of repetitions of the period in one sector is counted at the timing of the edge (rising edge in this example) of the pulse serving as the reference of the PWM drive voltage. At this time, along with the detection of sector switching, the count is once cleared by detecting the first edge, and the number of repeated cycles in the sector is counted. In this example, since the first edge is cleared, the edge is counted as 8. However, since the number of edges is 9, this is set as the count number. By dividing the sector range angle (60 degrees) by this count number and converting it to radians, the reference electrical angle resolution is calculated by the following equation.
Reference electrical angle resolution = 60/9 × 2π / 360 = 0.116355 rad

It is possible to estimate the electrical angle using the reference electrical angle resolution and perform the PWM calculation.
The reference electrical angle resolution can also be calculated using two or more sectors.
The above calculation is performed from the viewpoint of setting the rotation angle at which the rotor rotates at the target rotation speed to the reference electric angle resolution while one pulse of the PWM drive voltage is generated, and at the target rotation speed of the rotor. It is also possible to calculate using the following equation, where N is the rotation speed and T is the period of the PWM drive voltage.
Reference electrical angle resolution = 2π / ((1 / N) / T)

Further, by calculating the reference electrical angle resolution in the same manner in different sectors, the electrical angle can be estimated even when the number of periods of the PWM drive voltage differs between sectors.
An example of a procedure for counting the number of periods in each sector will be described with reference to the flowchart of FIG.
First, it is determined whether or not a rising edge is detected in the U-phase hall element Hu (step U1). If the rising edge is not detected (step U1, NO), the process proceeds to the next flow. If the rising edge is detected (step U1, YES), the edge count number in the hall element of the other phase is stored in the storage unit of the control unit 20, and then the PWM edge count is cleared (step U2). 4, the PWM edge count is started, and the process proceeds to the next flow.

In the next flow, it is determined whether or not a rising edge is detected in the V-phase hall element Hv (step V1). If the rising edge is not detected (step V1, NO), the process proceeds to the next flow. If the rising edge is detected (step V1, YES), the edge count number in the V-phase Hall element is stored in the storage unit of the control unit 20, and then the PWM edge count is cleared (step V2). 6, the PWM edge count is started, and the process proceeds to the next flow.
In the next flow, it is determined whether or not a rising edge is detected in the W-phase hall element Hw (step W1). If the rising edge is not detected (step W1, NO), the process proceeds to the next flow. If the rising edge is detected (step W1, YES), the edge count number in the W-phase Hall element is stored in the storage unit of the control unit 20, and then the PWM edge count is cleared (step W2). 2, the PWM edge count is started, and the process proceeds to the next flow.

In the next flow, it is determined whether or not a falling edge is detected in the U-phase hall element Hu (step U10). If the falling edge is not detected (step U10, NO), the process proceeds to the next flow. If the falling edge is detected (step U10, YES), the edge count number in the U-phase Hall element is stored in the storage unit of the control unit 20, and then the PWM edge count is cleared (step U11). . 1, the PWM edge count is started, and the process proceeds to the next flow.
In the next flow, it is determined whether or not a falling edge is detected in the V-phase hall element Hv (step V10). If the falling edge is not detected (step V10, NO), the process proceeds to the next flow. If a falling edge is detected (step V10, YES), the edge count number in the V-phase Hall element is stored in the storage unit of the control unit 20, and then the PWM edge count is cleared (step V11). . 3, the PWM edge count is started, and the process proceeds to the next flow.

  In the next flow, it is determined whether or not a falling edge is detected in the W-phase hall element Hw (step W10). If the falling edge is not detected (step W10, NO), the process proceeds to the next flow. If a falling edge is detected (YES in step W10), the edge count number in the W-phase Hall element is stored in the storage unit of the control unit 20, and then the PWM edge count is cleared (step W11). . 5, the PWM edge count is started, and the process proceeds to the next flow.

  The number of edges counted as described above can be read from the storage unit as necessary, and used for calculation of the reference electrical angle resolution. In this case, a reproducible sector in which the repetition period of the PWM drive voltage in the sector is positively coincident with the rotation time of the rotor in the sector can be selected as the reference electrical angle resolution. Thereby, the reference electrical angle resolution with the smallest error can be selected.

  As the electrical angle resolution used for the estimation of the electrical angle, the above-mentioned reference electrical angle resolution can be used, but a change in which the reference electrical angle resolution is corrected based on this change by observing a change in the PWM drive voltage. Electrical angular resolution can be used. In this example, an example in which a change in duty is used as a change in PWM drive voltage will be described.

  Based on the theoretical average duty in one or more sectors, the average duty in the same sector in any period before n (n is an integer of 1 or more) periods is compared. The information on the average duty can be obtained by storing the information in the storage unit in the control unit 20 and reading out the information as necessary during the PWM calculation.

For example, when the theoretical average duty is 64% and the average duty of the same sector n cycles before is 65%, the duty is larger than the reference, and this is a load near the sector. There is a possibility that the rotational speed change is microscopically negative. Therefore, the control accuracy can be improved by correcting the reference electrical angle resolution with the duty deviation. Specifically, the ratio of the average duty to the reference duty (65/64) is obtained, and the corrected electrical angle resolution is obtained by the following formula by multiplying this ratio by the obtained reference electrical angle resolution.
Corrected electrical angle resolution = 65/64 × 0.116355 rad
= 0.1181717468875 rad
By estimating the electrical angle using this corrected electrical angle resolution and performing the PWM calculation, it is possible to accurately control the rotation by applying an appropriate PWM drive voltage even when the load fluctuates.

In addition, a method for obtaining the corrected electrical angle resolution using the average duty that is a change in the PWM drive voltage without using the reference electrical angle resolution will be described.
Information on the average duty before n cycles is acquired, and when the rotor rotates by the average duty, the time for the rotor to pass through the sector given the average duty is estimated. If the average duty is greater than the theoretical duty, the estimated time is greater than the theoretical value. Within this estimated time, the number of repeatable cycles in the PWM drive voltage is calculated, and the sector range angle is divided by the calculated number. This value indicates the corrected electrical angle resolution. As a timing for obtaining the average duty, an edge in the PWM drive voltage can be used.

Next, the PWM calculation procedure by the control unit using the electrical angle estimation method of the present invention will be described with reference to the flowchart of FIG.
First, the reference electrical angle resolution is obtained by counting the edges of the pulses of the PWM drive voltage when the rotor passes through one or more sectors. In the case of one sector, the cycle count in each sector can be performed according to the flowchart shown in FIG.
When the edge count of the pulse of the PWM drive voltage is performed (step 1, YES), since the count number is cleared in the first edge detection, one is added to the count number (step s2), To do. Next, an electrical angle is estimated (step s3).

The estimation of the electrical angle is performed by the control unit according to the procedure shown in the flowchart shown in FIG.
First, the average duty of one or more sectors before n cycles (n is an integer of 1 or more) is calculated. The past duty is stored in the storage unit of the control unit 20, and the average duty can be calculated by reading the duty corresponding to the sector (step s30).

  Next, the theoretical duty when there is no speed fluctuation in the same sector is calculated from the target rotational speed (step s31). Then, assuming that the average duty is A, the theoretical duty is B, and the reference electrical angle resolution obtained from the edge count obtained in steps s1 and 2 is θrs, the reference electrical angle resolution is corrected (step s32). The corrected electrical angle resolution is obtained by A / B × θrs. The electrical angle is estimated using the corrected electrical angle resolution (step s33). In the estimation of the electrical angle, the electrical angle can be calculated by a known method using the electrical angle resolution as a parameter. Since this method is known, its detailed description is omitted here.

In this way, by correcting the reference electrical angle resolution based on the past duty and estimating the electrical angle using the corrected electrical angle resolution, the electrical angle can be accurately accurately reduced so as to reduce the difference from the actual electrical angle. Can be estimated.
Further, since the duty of the PWM drive voltage used as a parameter is data stored in the storage unit of the control unit, it is easy to read past data and use it in calculations, requiring a complicated calculation device. do not do. Therefore, rotation can be controlled with high accuracy at low cost.

After the electrical angle is estimated, calculation is performed by the control unit 20 by a known method.
First, the U-phase, V-phase, and W-phase currents detected by the current detector 7 and input to the control unit 20 and flowing through the coils 4 are converted into two phases by Clarke conversion (step 4).
FIG. 9 shows a vector diagram in the Clarke transformation. The currents iu, iv and iw flowing through the coils of the stator are converted into is on the α and β axes using the determinant in FIG. Yes. In this example, currents flowing from the V phase and the W phase to the U phase are shown.
In this way, the three-phase current flowing through each coil of the stator is converted into two phases (iα, iβ) on the α and β axes, thereby facilitating calculations when calculating the current value.

  Subsequently, coordinates based on the stator are converted into coordinates (dq coordinates) based on the rotor by Park conversion (step 5). FIG. 10 shows a vector diagram in the Park transformation. In the Park conversion, the Clark-converted current is is converted into dq coordinates using the determinant in FIG. At this time, it can be seen that the coordinate axis is rotated by θ. Since the Clark converted is is a current flowing in the coil, it is converted on the coordinates with respect to the stator side. However, in order to control the rotation of the rotor, for example, it is necessary to calculate the rotation angle of the rotor in each sector of the excitation sequence using the coordinates on the rotor side. Therefore, as shown in FIG. 10, the coordinates are converted into rotor coordinates with θ rotation by Park conversion.

  Then, in the dq coordinate, the current value of the coil is calculated using the estimated electrical angle, the current value is compared with the target current value, and the current control value is obtained by dq PI control (step 6). ). Subsequently, it is determined whether or not it is a timing to control the rotation speed of the rotor (step 7). In the case of the timing, the rotation speed of the rotor is compared with the target rotation speed, and the rotation speed of the rotor is speed PI controlled. A current control value for obtaining the value is obtained (step 8). Thereafter, in order to return the coordinates to the stator side, inverse Park transformation is performed (step 9). Then, a three-phase applied voltage to the coil is obtained by calculation using space Vector Modulation so as to obtain a current value of the coil corresponding to the target rotational speed of the rotor (Step 10). The calculation result is transmitted as a command signal to the drive circuit 10, a PWM drive voltage is generated, and the rotation control of the brushless motor is performed with high accuracy.

  In the above embodiment, the three-phase brushless motor has been described in detail. However, the present invention is not particularly limited with respect to the number of phases, the number of magnetic poles of the rotor, and the number of magnetic poles of the stator. In addition, in the estimation of the electrical angle, even when the target rotational speed is different, the electrical angle is estimated and high-precision rotation control is possible, and the speed used for current vector calculation and space vector conversion changes. When this happens, it is possible to respond by changing the PWM carrier cycle.

  The present invention has been described based on the above embodiment, but the present invention is not limited to the content of the above embodiment, and can be appropriately changed without departing from the scope of the present invention. is there.

DESCRIPTION OF SYMBOLS 1 Brushless motor 2a, 2b Magnetic pole 3 Rotor 4 Coil 5 Stator 6 Rotational speed detector 7 Current detector Hu, Hv, Hw Hall element 10 Drive circuit 11 PWM circuit 12 Bridge circuit 20 Control part

Claims (21)

An electrical angle used for the operation of the PWM drive voltage for rotating the rotor at a target rotational speed, an electrical angle estimation method of lube Rashiresumota be estimated by using the period of the PWM drive voltage,
The rotation angle at which the rotor rotates at the target rotation speed during one period in the PWM drive voltage is set as a reference electrical angle resolution,
Using the duty of the PWM drive voltage when the rotor is rotating, the estimated passing time for the rotor to rotate through the one or more sectors at the duty is calculated, and the estimated passage A correction electric angle resolution obtained by correcting the reference electric angle resolution using the number of repetitions and the rotation angle over one or more sectors is obtained by determining the number of repeatable cycles in the PWM drive voltage within a time. A method for estimating an electrical angle of a brushless motor , wherein the electrical angle is estimated using the corrected electrical angle resolution . An electrical angle used for the operation of the PWM drive voltage for rotating the rotor at a target rotational speed, an electrical angle estimation method of lube Rashiresumota be estimated by using the period of the PWM drive voltage,
The rotation angle at which the rotor rotates at the target rotation speed during one period in the PWM drive voltage is set as a reference electrical angle resolution,
Using the duty of the PWM drive voltage when the rotor is rotating, the theoretical reference average duty required to obtain the target rotation speed and the average when the rotor is rotating An electrical angle of a brushless motor , wherein a corrected electrical angle resolution obtained by correcting the reference electrical angle resolution is calculated based on a deviation from a duty, and the electrical angle is estimated using the corrected electrical angle resolution. Estimation method. 3. The method of estimating an electrical angle of a brushless motor according to claim 1, wherein a rising edge or a falling edge of the pulse of the PWM drive voltage is used as a timing for estimating the electrical angle. The electric angle of the brushless motor according to any one of claims 1 to 3, wherein a rising edge or a falling edge of a pulse of the PWM drive voltage is used as a timing when determining the reference electric angle resolution. Estimation method. The rotational speed at the target rotational speed of the rotor of N, the period as T in the PWM drive voltage, using the following equation, any one of the preceding claims, characterized in that calculating the reference electric angle resolution The electrical angle estimation method for a brushless motor according to item 1 .
Reference electrical angle resolution = 2π / ((1 / N) / T) 6. The method of estimating an electrical angle of a brushless motor according to claim 1, wherein the reference electrical angle resolution is calculated in units of one or more sectors of an excitation sequence.   While one or two or more sectors of the excitation sequence are switched, the number of rising or falling edges of the pulse of the PWM drive voltage is obtained, and the rotor rotates at the target rotational speed between the number of edges and the switching. The method for estimating an electrical angle of a brushless motor according to claim 6, wherein the reference electrical angle resolution is calculated using a rotational angle of rotation. The reference average duty is an average value of the duty of the PWM drive voltage when the rotor rotates over one or more sectors for which the reference electrical angle resolution is calculated, and the average duty value is the one or more sectors. 3. The duty value of the PWM drive voltage when the rotor rotates over the same sector n cycles before two or more sectors (n is an integer of 1 or more). The method for estimating the electrical angle of the brushless motor described. The duty of the PWM drive voltage when the rotor rotates is A, the theoretical reference duty of the PWM drive voltage required to obtain the target rotational speed is B, and the reference electrical angle resolution is θrs. 9. The method of estimating an electrical angle of a brushless motor according to claim 2 , wherein the corrected electrical angle resolution is calculated using the following equation.
Corrected electrical angle resolution = A / B × θrs The period of the PWM drive voltage is set so as to have a relationship of 1 / m times (m is an integer of 1 or more) the time for which the rotor passes through one sector at a target rotational speed. The electrical angle estimation method of the brushless motor according to any one of claims 1 to 9 . A rotor having a plurality of magnetic poles formed by permanent magnets;
A stator having a plurality of coils excited by application of a driving voltage;
A rotor position detection sensor for detecting a relative position of the rotor with respect to the stator;
A drive circuit for applying a multi-phase PWM drive signal using a PWM carrier to the coil;
A rotational speed detector for detecting the rotational speed of the rotor;
A current detector for detecting a current value passed through the coil;
A controller for controlling the rotation of the rotor,
The controller determines an excitation sequence including a plurality of sectors in response to a detection result of the rotor position detection sensor, and the rotor rotates at the target rotation speed during one period of the PWM drive voltage. Using the rotation angle as the reference electrical angle resolution and the duty of the PWM drive voltage when the rotor is rotating, the rotor is estimated to pass through the one or more sectors at that duty. A passing time is calculated, a number in which the period of the PWM drive voltage can be repeated within the estimated passing time is determined, and the reference electrical angle is calculated using the number of repetitions and a rotation angle over one or more sectors. resolution calculates a correction electrical angle resolution has been corrected, estimating the electrical angle of the rotor by using the correction electrical angle resolution, at least the rotational speed detection A command signal for generating the PWM drive voltage according to a target rotation speed of the rotor in response to a detection result of the detector and the current detector, using the electrical angle, and calculating the command signal in the drive circuit A brushless motor characterized by being transmitted to. A rotor having a plurality of magnetic poles formed by permanent magnets;
A stator having a plurality of coils excited by application of a driving voltage;
A rotor position detection sensor for detecting a relative position of the rotor with respect to the stator;
A drive circuit for applying a multi-phase PWM drive signal using a PWM carrier to the coil;
A rotational speed detector for detecting the rotational speed of the rotor;
A current detector for detecting a current value passed through the coil;
A controller for controlling the rotation of the rotor,
The control unit receives a detection result of the rotor position detection sensor and determines an excitation sequence including a plurality of sectors,
The rotation angle at which the rotor rotates at the target rotation speed during one period in the PWM drive voltage is set as a reference electrical angle resolution, and the theoretical reference average duty required to obtain the target rotation speed; Based on the deviation from the average duty when the rotor is rotating, the reference electrical angle resolution is corrected to calculate a corrected electrical angle resolution, and the electrical angle of the rotor is calculated using the corrected electrical angle resolution. And calculating a command signal for generating the PWM drive voltage according to a target rotation speed of the rotor by using at least the detection results of the rotation speed detector and the current detector using the electrical angle. And transmitting the command signal to the drive circuit. The brushless motor according to claim 11 , wherein the control unit uses a rising edge or a falling edge of a pulse of the PWM drive voltage as a timing when the electrical angle is estimated. The said control part uses the rising or falling edge of the pulse of the said PWM drive voltage for the timing at the time of determining the said reference | standard electrical angle resolution, The any one of Claims 11-13 characterized by the above-mentioned. Brushless motor. Wherein the control unit, the rotational speed at the target rotational speed of the rotor of N, the period as T in the PWM drive voltage, using the following equation, according to claim 11, characterized in that calculating the reference electric angle resolution The brushless motor of any one of -14.
Reference electrical angle resolution = 2π / ((1 / N) / T) The brushless motor according to any one of claims 11 to 15, wherein the control unit calculates the reference electrical angle resolution in one or two or more sectors in the excitation sequence. The control unit obtains the number of rising or falling edges of the pulse of the PWM drive voltage during switching of one or more sectors of the excitation sequence, and the rotor is operated between the number of edges and the switching. The brushless motor according to claim 16 , wherein the reference electrical angle resolution is calculated using a rotation angle that rotates at the target rotation speed. The reference average duty is an average value of the duty of the PWM drive voltage when the rotor rotates over one or more sectors for which the reference electrical angle resolution is calculated, and the average duty value is the one or more sectors. or before n cycles of the two or more sectors (n is an integer of 1 or more) according to claim 12, wherein the said rotor over the same sector of the average value of the duty of the PWM drive voltage when rotated Brushless motor. The control unit is configured such that the duty of the PWM drive voltage when the rotor rotates is A, the theoretical reference duty of the PWM drive voltage required to obtain the target rotational speed is B, and the reference electrical angle 19. The brushless motor according to claim 12 , wherein the corrected electrical angle resolution is calculated by using the following formula with a resolution of θrs.
Corrected electrical angle resolution = A / B × θrs The period of the PWM drive voltage is set so as to have a relationship of 1 / m times (m is an integer of 1 or more) the time for which the rotor passes through one sector at a target rotational speed. The brushless motor according to any one of claims 11 to 19 . The brushless motor according to any one of claims 11 to 20, wherein the control unit includes a storage unit that stores a change in duty of the PWM drive voltage.

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