阅读说明：本技术 控制装置及马达驱动系统 (Control device and motor drive system ) 是由 森山胜敏 于 2020-02-05 设计创作，主要内容包括：实施方式涉及控制装置及马达驱动系统。根据实施方式,提供具有判定部、修正部及驱动控制部的控制装置。判定部判定步进电机的转子的相位相对于目标相位是提前还是滞后。修正部根据判定结果,从多个修正值选择对于步进电机的驱动电流的控制值的修正值。驱动控制部利用所选择的修正值对驱动电流的控制值进行修正而驱动步进电机。(The embodiment relates to a control device and a motor drive system. According to an embodiment, a control device is provided that includes a determination unit, a correction unit, and a drive control unit. The determination section determines whether the phase of the rotor of the stepping motor is advanced or retarded with respect to the target phase. The correction unit selects a correction value for the control value of the drive current of the stepping motor from the plurality of correction values based on the determination result. The drive control unit corrects the control value of the drive current by the selected correction value to drive the stepping motor.)

1. A control device is provided with:

a determination unit that determines whether the phase of the rotor of the stepping motor is advanced or retarded with respect to a target phase;

a correction unit that selects a correction value for a control value of the drive current of the stepping motor from a plurality of correction values based on the determination result; and

and a drive control unit that corrects the control value of the drive current by using the selected correction value to drive the stepping motor.

2. The control device according to claim 1,

the control device further includes:

a current-voltage conversion unit that converts a current flowing through the stepping motor into a voltage and detects the voltage;

a time measuring unit having a first reference voltage and a second reference voltage lower than the first reference voltage, measuring a first time until the detected voltage exceeds the first reference voltage and a second time until the detected voltage is lower than the second reference voltage, and calculating a difference time between the first time and the second time;

a zero-crossing determining unit for determining a zero-crossing position of the induced voltage of the stepping motor based on the difference time; and

and a rotor phase calculation unit for calculating the phase of the rotor based on the zero-crossing position of the induced voltage.

3. The control device according to claim 1,

the correction unit selects a first correction value that retards the phase of the rotor when the phase of the rotor is advanced with respect to the target phase, and selects a second correction value that advances the phase of the rotor when the phase of the rotor is retarded with respect to the target phase.

4. The control device according to claim 3,

the correction unit selects the second correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is less than a first number of times, and selects a third correction value that is larger than the second correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is equal to or greater than the first number of times.

5. The control device according to claim 4,

the correction unit selects the third correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is equal to or greater than the first number of times and less than the second number of times, and selects the fourth correction value that is greater than the third correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is equal to or greater than the second number of times.

6. The control device according to claim 3,

the correction unit selects the second correction value when the phase of the rotor is retarded with respect to the target phase and the rotation of the rotor is not in an accelerated state, and selects a third correction value larger than the second correction value when the phase of the rotor is retarded with respect to the target phase and the rotation of the rotor is in an accelerated state.

7. The control device according to claim 3,

the absolute value of the second correction value is larger than the absolute value of the first correction value.

8. The control device according to claim 4,

the absolute value of the second correction value is larger than the absolute value of the first correction value,

the absolute value of the third correction value is larger than the absolute value of the second correction value.

9. The control device according to claim 5,

the absolute value of the second correction value is larger than the absolute value of the first correction value,

the absolute value of the third correction value is larger than the absolute value of the second correction value,

the absolute value of the fourth correction value is larger than the absolute value of the third correction value.

10. The control device according to claim 6,

the absolute value of the second correction value is larger than the absolute value of the first correction value,

the absolute value of the third correction value is larger than the absolute value of the second correction value.

11. The control device according to claim 2,

the correction unit selects a first correction value that retards the phase of the rotor when the phase of the rotor is advanced with respect to the target phase, and selects a second correction value that advances the phase of the rotor when the phase of the rotor is retarded with respect to the target phase.

12. The control device according to claim 11,

the correction unit selects the second correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is less than a first number of times, and selects a third correction value that is larger than the second correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is equal to or greater than the first number of times.

13. The control device according to claim 12,

the correction unit selects the third correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is equal to or greater than the first number of times and less than the second number of times, and selects the fourth correction value that is greater than the third correction value when it is determined that the number of consecutive times that the phase of the rotor lags the target phase is equal to or greater than the second number of times.

14. The control device according to claim 12,

the correction unit selects the second correction value when the phase of the rotor is retarded with respect to the target phase and the rotation of the rotor is not in an accelerated state, and selects a third correction value larger than the second correction value when the phase of the rotor is retarded with respect to the target phase and the rotation of the rotor is in an accelerated state.

15. The control device according to claim 11,

the absolute value of the second correction value is larger than the absolute value of the first correction value.

16. The control device according to claim 12,

the absolute value of the second correction value is larger than the absolute value of the first correction value,

the absolute value of the third correction value is larger than the absolute value of the second correction value.

17. The control device according to claim 13,

the absolute value of the second correction value is larger than the absolute value of the first correction value,

the absolute value of the third correction value is larger than the absolute value of the second correction value,

the absolute value of the fourth correction value is larger than the absolute value of the third correction value.

18. The control device of claim 14,

the absolute value of the second correction value is larger than the absolute value of the first correction value,

the absolute value of the third correction value is larger than the absolute value of the second correction value.

19. A motor drive system is provided with:

a stepping motor; and

the control device according to any one of claims 1 to 20 for driving the stepping motor.

Technical Field

The present embodiment relates to a control device and a motor drive system.

Background

In the control device of the stepping motor, the stepping motor is driven by supplying the generated driving current. In this case, it is desirable to suppress the step-out of the stepping motor with respect to the change in the load.

Disclosure of Invention

Embodiments provide a control device and a motor drive system capable of suppressing step-out of a stepping motor.

According to an embodiment, a control device is provided that includes a determination unit, a correction unit, and a drive control unit. The determination section determines whether the phase of the rotor of the stepping motor is advanced or retarded with respect to the target phase. The correction unit selects a correction value for the control value of the drive current of the stepping motor from the plurality of correction values based on the determination result. The drive control unit corrects the control value of the drive current by the selected correction value to drive the stepping motor.

Drawings

Fig. 1 is a configuration diagram of a control system including a control device according to an embodiment.

Fig. 2A to 2C are diagrams illustrating a process of determining a zero-crossing position of an induced voltage in the embodiment.

Fig. 3 is a diagram showing a configuration of a control device according to an embodiment.

Fig. 4 is a diagram showing a configuration of a control device according to a first modification of the embodiment.

Fig. 5 is a diagram showing a data structure of correction information in a first modification of the embodiment.

Fig. 6 is a diagram showing a configuration of a control device according to a second modification of the embodiment.

Fig. 7 is a diagram showing a configuration of a control device according to a third modification of the embodiment.

Fig. 8A and 8B are diagrams showing a data structure of correction information in a third modification of the embodiment.

Detailed Description

Hereinafter, the control device according to the embodiment will be described in detail with reference to the drawings. The present invention is not limited to the embodiment.

(embodiment mode)

Fig. 1 is a configuration diagram of a motor drive system. The motor drive system includes a stepping motor 3 and a control device 10. The control device 10 generates a drive current and controls the driving of the stepping motor 3.

The control device 10 includes an H-bridge circuit 11, a drive control unit 12, a current-voltage conversion unit 14, a time measurement unit 15, a zero-cross determination unit 16, a rotor phase calculation unit 17, and an induced voltage detection unit 18. The stepping motor 3 includes a rotor including a plurality of magnetic poles and a stator including a winding (a plurality of coils) of a plurality of phases, which are not shown. Fig. 1 illustrates a configuration corresponding to a 1-phase winding. The configuration corresponding to the winding of the other phase requires a configuration of a control device other than the drive control unit 12. Here, the illustration is not shown for the sake of simplicity.

The H-bridge circuit 11 is electrically connected to the stepping motor 3. The H-bridge circuit 11 supplies a drive current (motor current) Imc to the stepping motor 3 under the control of the drive control unit 12. The H-bridge circuit 11 has high-side transistors Tr1, Tr2 and low-side transistors Tr3, Tr 4. The transistors Tr1 to Tr4 are NMOS transistors, for example. The transistor Tr1 has a source connected to one end (node N1) of the stepping motor 3, a drain connected to the power supply voltage Vm, and a gate connected to the drive control unit 12. The transistor Tr2 has a source connected to the other end (node N2) of the stepping motor 3, a drain connected to the power supply voltage Vm, and a gate connected to the drive control unit 12. The transistor Tr3 has a source connected to the ground potential Vss, a drain connected to one end of the stepping motor 3, and a gate connected to the drive control unit 12. The transistor Tr4 has a source connected to the ground potential Vss, a drain connected to the other end of the stepping motor 3, and a gate connected to the drive control unit 12.

The H-bridge circuit 11 has a first operating state, a second operating state, and a third operating state. In the first operating state, the transistor Tr1 and the transistor Tr4 are maintained in an on state, and the transistor Tr2 and the transistor Tr3 are maintained in an off state. Thereby, a current is supplied from the power supply voltage Vm to the stepping motor 3 via the transistor Tr1 and the node N1. In the second operating state, the transistor Tr2 and the transistor Tr3 are maintained in an on state, and the transistor Tr1 and the transistor Tr4 are maintained in an off state. Thereby, a current is supplied from the power supply voltage Vm to the stepping motor 3 via the transistor Tr2 and the node N2. In the third operating state, the transistor Tr1 and the transistor Tr2 are maintained in an off state, and the transistor Tr3 and the transistor Tr4 are maintained in an on state. Thereby, the electric charge accumulated in the coil of the stepping motor 3 is discharged and a current flows to the ground potential Vss. The third motion state is also called Slow Decay.

When the transistors Tr1 and Tr2 are turned off and the transistors Tr3 and Tr4 are turned on, the current-voltage converter 14 converts the current flowing from the stepping motor 3 side to the transistor Tr3 or Tr4 into a voltage and detects the voltage. The current-voltage converter 14 supplies the detection voltage to the time measuring unit 15. Fig. 2A shows an example of a temporal change in the detection voltage of the current-voltage conversion unit 14. During a period (charging period) Tc during which the motor current Imc is supplied to the stepping motor 3, the detection voltage is boosted from a state lower than the reference voltage (second reference voltage) V2 to a state higher than the reference voltage (first reference voltage) V1. In a period (discharge period) Td during which the electric charges accumulated in the stepping motor 3 are discharged to the ground potential Vss side, the detection voltage is lowered from a state higher than the reference voltage V1 to a state lower than the reference voltage V2. The reference voltage V1 can be determined experimentally as a value lower than the peak on the high voltage side in the detection voltage and near the peak. The reference voltage V2 can be determined experimentally to be a value higher than and near the peak on the low voltage side in the detection voltage.

The time measuring unit 15 measures the time during which the amount of current changes based on the detection voltage. For example, the time measuring unit 15 generates a result CM1 of comparing the detection voltage with the reference voltage V1, and generates a result CM2 of comparing the detection voltage with the reference voltage V2. Fig. 2B shows an example of the comparison result in the time measuring unit 15. The time measuring unit 15 measures a time difference Δ t between a timing t1 at which the comparison result CM1 shifts from the H level to the L level and a timing t2 at which the comparison result CM2 shifts from the H level to the L level. This time Δ t is a difference time between a first time until the detected voltage exceeds the reference voltage V1 shown in fig. 2A and a second time until the detected voltage becomes lower than the reference voltage V2. The time measuring unit 15 supplies the measurement result (time Δ t) to the zero-crossing determining unit 16.

The induced voltage detection unit 18 detects the induced voltage Ve generated at both ends of the stepping motor 3. Fig. 2C shows an example of temporal changes in the induced voltage Ve and the motor current Imc. For example, the induced voltage Ve changes as indicated by a dotted line with respect to the motor current Imc (solid line) flowing through the stepping motor 3. Induced voltage detecting unit 18 supplies the detection result (induced voltage Ve) to zero-crossing determining unit 16.

The zero-crossing determining unit 16 determines the zero-crossing position of the induced voltage waveform from the time Δ t and the induced voltage Ve, and supplies the determination result (zero-crossing position information) to the rotor phase calculating unit 17. For example, an equivalent of the stepping motor 3 is represented by the following formula (1).

V₃-Ve＝(Rm×Imc)+{Lm×(Δi/Δt)}···(1)

V₃Is a power supply voltage applied to the stepping motor 3, Rm is an internal resistance (motor constant) of the stepping motor 3, Lm is an inductance (motor constant) of a coil of the stepping motor 3, and Δ i/Δ t is a control current change amount per unit time.

When the H-bridge circuit 11 changes from the first operating state to the third operating state, the stepping motor 3 is electrically disconnected from the power supply voltage Vm, and V₃0V, and thus formula (1) can be represented as,

-Ve＝(Rm×Imc)+{Lm×(Δi/Δt)}···(2)。

the same applies to the case where the H-bridge circuit 11 changes from the second operating state to the third operating state. When the expression (2) is modified, it can be expressed as,

Δt＝(Lm×Δi)/[-(Ve+(Rm×Imc))]···(3)。

since the induced voltage Ve becomes 0 at the zero crossing position of the induced voltage in equation (3), it can be expressed as,

Δt＝(Lm×Δi)/[-(Rmm×Imc)]···(4)。

here, Δ i is controlled by the ratio of the motor current Imc (proportional value a). For example, in

Δi：Imc＝A：1···(5)

In the case of performing the control, the formula (4) can be expressed as,

Δt＝(Lm×A)/[-(Rm)]···(6)。

since Rm and Lm are constants specific to the motor, the time position at which the value Δ t is the value obtained on the right side of equation (6) can be found to be the zero crossing position of the induced voltage Ve shown in fig. 2C.

The rotor phase calculation unit 17 receives the determination result (the zero-crossing position of the induced voltage) from the zero-crossing determination unit 16, and calculates the phase of the rotor as a parameter indicating the rotor position. For example, the induced voltage is represented as a voltage by a change in the magnetic field of the rotor, and the phase of the magnetic field of the rotor and the induced voltage are shifted by 90 degrees. Therefore, when the zero-crossing position of the induced voltage is detected, the vertex position of the magnetic field of the rotor can be detected, and the phase of the rotor can be estimated.

The controller 10 obtains a phase deviation of the rotor with respect to a target phase (ideal phase), and controls the stepping motor 3 so as to reduce the phase deviation. For example, if the phase of the rotor is retarded with respect to the target phase, the control device 10 increases the drive current so as to advance the phase of the rotor and reduce the phase deviation. The control device 10 reduces the drive current so as to retard the phase of the rotor and reduce the phase deviation if the phase of the rotor is advanced with respect to the target phase. In the drive control using this phase deviation, when the load changes abruptly, the phase deviation becomes excessively large abruptly, and the like, and thus, there is a case where a step motor 3 is difficult to follow the control.

In order to suppress the step-out, for example, it is conceivable to detect the rotation amount of the rotor in the stepping motor 3 by a position detection sensor such as an encoder, and perform PI control or PID control using the detected position information. In these controls, the phase deviation is obtained from the target phase (ideal phase) of the rotor detected by the position detection sensor. Then, P, I, and D are performed for each phase deviation, and a corrected current value corresponding to the sum of these values is added as an operation amount to the control value of the current drive current. That is, in the PI control and the PID control, complicated arithmetic processing is performed, and adjustment is performed for a long time in order to optimize an arithmetic parameter in accordance with the characteristics of the control system. Therefore, the cost of the control device 10 may increase. In addition, in these controls, when a load is abruptly changed, phase deviation may be abruptly excessively large, and the stepping motor 3 may be difficult to follow up control in some cases.

Therefore, in the present embodiment, the control device 10 corrects the control value of the drive current by using the correction value selected as a result of the determination as to whether the phase of the rotor is advanced or retarded with respect to the target phase. Specifically, focusing on the direction (advance, retard) of the error of the phase of the rotor with respect to the ideal phase, the correction value is selected from a plurality of candidates based on the estimation result of the error. The plurality of candidates are fixed values, respectively. The correction value is a value M in a direction in which the drive current increases (hereinafter referred to as an increase direction) when the phase of the rotor lags behind the ideal phase, and a value N in a direction in which the drive current decreases (hereinafter referred to as a decrease direction) when the phase of the rotor advances with respect to the ideal phase. When it can be considered that the phase of the rotor follows the ideal phase, the value may be set to 0 without correction. Thus, when there is a sudden change in load, the correction value can be prevented from becoming excessively large, and the occurrence of step-out can be prevented.

In addition, in the stepping motor 3, there is a tendency that the possibility of the step-out is high when the phase of the rotor is delayed compared to when the phase of the rotor is advanced. The relationship of the absolute value of the correction value is defined as | M | > | N | in consideration of this tendency. Thereby, the offset can be effectively suppressed.

More specifically, the control device 10 further includes a determination unit 22 and a correction unit 21. The determination unit 22 determines whether the phase of the rotor is advanced or retarded with respect to the ideal phase, based on the error of the rotor with respect to the target phase. The determination unit 22 supplies the determination result to the correction unit 21. The correction unit 21 selects a correction value for the drive current based on the determination result, and supplies the selected correction value to the drive control unit 12. The drive control unit 12 may perform the correction by adding the correction value to the control value of the drive current, for example. The drive control unit 12 controls the drive of the H-bridge circuit 11 using the corrected control value of the drive current. The H-bridge circuit 11 supplies a drive current to the stepping motor 3 according to the control value of the drive current.

Fig. 3 is a configuration diagram of the control device 10 according to the embodiment. For the sake of explanation, the control device 10 of fig. 3 is shown only in part. For example, the rotor phase calculating unit 17 obtains the phase of the rotor from the zero-crossing position of the induced voltage, and supplies the phase to the determining unit 22. The determination unit 22 detects the time from the start of the stepping motor 3 by a timer or the like, not shown. The determination unit 22 holds an ideal phase periodically obtained from waveform information indicating an ideal rotor phase set in advance and the time from the start. The determination unit 22 includes an error determination unit 22 a. The error determination unit 22a obtains the error of the rotor with respect to the ideal phase by means of subtracting the ideal phase from the phase of the rotor.

In the error determination unit 22a, a predetermined range including 0 and having a negative threshold value and a positive threshold value is set as an allowable range of the error. The error determination unit 22a generates a signal S1 indicating the direction of the error and a signal S2 indicating the presence or absence of correction based on the result of comparing the error with the allowable range, and supplies the signals to the correction unit 21. The correction unit 21 includes a selector 21a and a selector 21 b. The signal S1 is supplied to the selection node S of the selector 21a, and the signal S2 is supplied to the selection node S of the selector 21 b. A correction value (first correction value) N is supplied to the input node "0" of the selector 21a, and a correction value (second correction value) M is supplied to the input node "1" of the selector 21 a. The output node of the selector 21a is connected to the input node "1" of the selector 21 b. A fixed value of 0 without correction is supplied to the input node "0" of the selector 21 b.

The error determination unit 22a sets the signal S2 to 0 (not increased or decreased) if the error falls within the allowable range, and sets the signal S2 to 1 (increased or decreased) if the error falls outside the allowable range. The error determination unit 22a determines that the phase of the rotor is retarded with respect to the ideal phase (i.e., advanced) if the error is smaller than the negative threshold, and determines that the phase of the rotor is retarded with respect to the ideal phase (i.e., retarded) if the error is larger than the positive threshold, and sets the signal S1 to 1 (i.e., retarded).

When the error is out of the allowable range and smaller than the negative threshold, the selector 21a selects the correction value N and supplies the correction value N to the selector 21b in response to the signal S1 being equal to 0. When the error is out of the allowable range and greater than the positive threshold, the selector 21a selects the correction value M and supplies it to the selector 21b in response to the signal S1 being equal to 1. In response to the signal S2 being equal to 1, the selector 21b selects the output of the selector 21a and supplies the selected output to the drive control unit 12. On the other hand, when the error falls within the allowable range, the selector 21b selects a fixed value of 0 and supplies the selected value to the drive control unit 12 in response to the signal S2 being equal to 0.

The drive control unit 12 includes an adder 12 a. The adder 12a adds the correction value supplied from the correction unit 21 to the control value of the current drive current, and supplies the resultant to the H-bridge circuit 11 as the control value of the next drive current. The H-bridge circuit 11 causes a drive current to flow in accordance with a control value of the newly supplied drive current.

As described above, in the present embodiment, the control device 10 corrects the control value of the drive current by the correction value selected according to the result of determining whether the phase of the rotor is advanced or retarded with respect to the ideal phase. Thus, when there is a sudden change in load, the drive current is corrected at a fixed value, so that the correction value can be prevented from becoming excessively large, and the occurrence of step-out can be prevented. Further, since there is no complicated arithmetic processing such as PID control, an adjustment work for optimizing the parameters is not necessary. This makes it possible to suppress the offset due to a sudden change in load at low cost.

When the advance and retard of the phase of the rotor have a negative correlation with the increase and decrease of the control value of the drive current, the control device 10 may be configured correspondingly to this. That is, in the control device 10, the correction value of the drive current may be set to the correction value N when the phase of the rotor lags behind the ideal phase, and may be set to the correction value M when the phase of the rotor advances from the ideal phase. In this case, the correction value M is supplied to the input node "0" of the selector 21a, and the correction value N is supplied to the input node "1" of the selector 21 a. With this configuration, even when there is a sudden change in load, the drive current can be corrected with a fixed value, and therefore, the correction value can be prevented from becoming excessively large, and the occurrence of step-out can be prevented.

Alternatively, when the advance and retard of the phase of the rotor have a positive correlation with the increase and decrease in the control value of the drive current, the correction value M may be changed by the number of times the estimation result of the error continuously becomes the same direction. The controller 10 changes the correction value to a larger value as the number of times the error estimation result continues in the same direction increases.

Fig. 4 is a diagram showing a configuration of the control device 10 according to the first modification of the embodiment. The control device 10 further includes a detection unit 24 and a storage unit 23.

The detection unit 24 detects the number of times that the estimation result of the difference continues in the same direction, and supplies the count value to the storage unit 23. The detection unit 24 has a counter, not shown, and counts up each time the difference estimation result and the previous estimation result are in the same direction, and resets each time the difference estimation result and the previous estimation result are in different directions.

The storage unit 23 has correction information for associating the count value with the correction value M. The storage unit 23 refers to the correction information, selects the correction value M corresponding to the count value, and supplies the correction value M to the correction unit 21.

Fig. 5 is a diagram showing an example of a data structure of the correction information. In the correction information, the number of times the estimation result of the difference continues in the same direction is associated with a plurality of correction values M. In the correction information, the number of times increases, and the correction value increases stepwise, and corresponds to the correction value. In the correction information of fig. 5, the correction value (second correction value) M is 1 when the count is 1, the correction value (third correction value) M is 2 when the count is 4, and the correction value (fourth correction value) M is 256 when the count is 11 or more. That is, the larger the number of times the error estimation result continues to be in the same direction, the larger the correction value. This makes it possible to achieve both responsiveness to a phase error and stability against external disturbances. In the correction information of fig. 5, 1 in 256 is set as 1 with respect to the control range of the drive current, but any fixed value may be used.

Fig. 6 is a configuration diagram of a control device 10 according to a second modification of the embodiment. The control device 10 of fig. 6 includes a correction unit 121 further including a selector 21c instead of the correction unit 21 of fig. 3, and includes a detection unit 124. The control device 10 operates according to a step clock received from the outside or generated internally. The detection unit 124 measures the period of the step clock, and detects the acceleration state of the rotor rotation based on the measurement result. The control device 10 changes the correction value M to a larger value when the rotor rotation is in an acceleration state than when the rotor rotation is in a steady state.

The detection unit 124 includes an acceleration detection unit 24 b. The acceleration detection section 24b has a cycle threshold value related to the cycle of the step clock. The acceleration detection unit 24b generates a signal S3 indicating the acceleration state of the rotor rotation based on the result of comparing the measured cycle of the step clock with the cycle threshold value, and supplies the signal to the selection node S of the selector 21 c.

The acceleration detection unit 24b determines that the rotor is in a stable state if the period of the step clock is equal to or greater than the period threshold, and sets the signal S3 to 0 (stable). The acceleration detection unit 24b determines that the rotation of the rotor is in the acceleration state if the cycle of the step clock is lower than the cycle threshold, and sets the signal S3 to 1 (acceleration).

The input node "0" of the selector 21c is supplied with the correction value M1, and the input node "1" is supplied with the correction value M2. The selector 21c selects the correction value M1 or M2 in accordance with the signal S3 and supplies the correction value M1 or M2 to the input node "1" of the selector 21 a. The absolute value of the correction value M2 is larger than the absolute value of the correction value M1. The correction value M1 is selected when the signal S3 is 0, and the correction value M2 is selected when the signal S3 is 1. This can suppress the step-out in the case of a rapid speed change.

The control device 10 may perform control combining the control in the first modification of the embodiment and the control in the second modification of the embodiment. The control device 10 may change the correction value M to a correction value that increases as the number of times the estimation result of the error continues in the same direction increases. The correction value may be set to a larger value when the rotor rotation is in an accelerated state than when the rotor rotation is in a steady state.

Fig. 7 is a configuration diagram of a control device 10 according to a third modification of the embodiment. The correcting unit 121 is similar to the correcting unit 121 shown in fig. 6. The detection unit 224 is a combination of the detection unit 24 of fig. 4 and the detection unit 124 of fig. 6, and includes a count detection unit 24a and an acceleration detection unit 24 b. The detection unit 224 detects the number of times the estimation result of the error continues in the same direction. The detection unit 224 detects the acceleration state of the rotor rotation based on the result of measuring the cycle of the step clock.

The storage unit 223 has correction information for a steady state and correction information for an acceleration state, which correspond to the correction value M and the number of times the estimation result of the error continuously becomes the same direction, respectively. The storage unit 23 refers to the 2 pieces of correction information, and selects correction values corresponding to the number of times of detection results from the plurality of candidates.

Fig. 8A and 8B are diagrams showing an example of the data structure of the correction information for the steady state (fig. 8A) and the acceleration state (fig. 8B). Both the correction information in fig. 8A and 8B correspond to correction values that become larger in stages as the number of times increases, but the correction information for the acceleration state (fig. 8B) corresponds to larger correction values in stages of a smaller number of times.

The memory 223 supplies the selected correction values M1 and M2 to the correction unit 121. That is, the storage unit 223 supplies the correction value M1 to the input node "0" of the selector 21c, and supplies the correction value M2 to the input node "1" of the selector 21 c. The acceleration detector 24b generates a signal S3 indicating the acceleration state of the rotor rotation and supplies the signal to the selection node S of the selector 21 c.

The acceleration detection unit 24b determines that the rotor is in a stable state if the period of the step clock is equal to or greater than the period threshold, and sets the signal S3 to 0 (stable). The acceleration detection unit 24b determines that the rotor rotation is in the acceleration state if the cycle of the step clock is lower than the cycle threshold, and sets the signal S3 to 1 (acceleration).

The input node "0" of the selector 21c is supplied with the correction value M1, and the input node "1" is supplied with the correction value M2. The selector 21c selects the correction value M1 or M2 in accordance with the signal S3 and supplies the correction value M1 or M2 to the input node "1" of the selector 21 a. The absolute value of the correction value M2 is larger than the absolute value of the correction value M1. The correction value M1 is selected when the signal S3 is 0, and the correction value M2 is selected when the signal S3 is 1. This can suppress the step-out when the speed changes rapidly.

In this way, the controller 10 changes the fixed value (+ M) in the increasing direction to a larger correction value as the number of times the error estimation result continues to become the same direction increases. The correction value is set to a larger value when the rotor rotation is in an accelerated state than when the rotor rotation is in a steady state. This makes it possible to achieve both responsiveness to a phase error and stability against external disturbances, and to suppress a step-out when the speed changes rapidly.

Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, substitutions, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.