JP2007325395A - Controller for stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller of a stepping motor with which vibration of a rotator of the stepping motor can always be suppressed stably, regardless of the state of the load. <P>SOLUTION: The controller controls the stepping motor (10) by a current command corresponding to a position command. The controller is provided with speed deviation detecting means (42, 43 and 47) for detecting the speed deviation of the stepping motor (10), a correction value calculating means (46) for calculating the correction value of torque current of the stepping motor (10) based on the speed deviation, and a means (48) for correcting the current command by the correction value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control device for a stepping motor, and more particularly to a device for controlling the stepping motor so that vibration of a rotor during operation is suppressed.

When the stepping motor is controlled by a current command based on the position command, vibration may be generated in the rotor of the stepping motor. The following factors can be considered as the cause of the vibration.
(A) Resonance between torque ripple and inertia (b) Effect of roughness of time interval of sampling control (c) Other unknown factors

  Therefore, conventionally, a technique has been proposed in which the rotational speed deviation of the stepping motor is detected and the vibration of the rotor of the stepping motor is suppressed by correcting the excitation phase based on this rotational speed deviation. (For example, see Patent Document 1)

Japanese Unexamined Patent Publication No. 2000-4598

  However, according to the above prior art, as will be described later, the torque change amount accompanying the excitation phase control depends on the load, and the torque change amount accompanying the phase control is limited. Therefore, depending on the state of the load, vibrations of the rotor of the stepping motor may not be sufficiently suppressed.

  The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a stepping motor control device capable of stably suppressing vibration of the rotor of the stepping motor regardless of the state of the load. It is to provide.

  The present invention is a control device for controlling a stepping motor by a current command corresponding to a position command, and includes a speed deviation detecting means for detecting a speed deviation of the stepping motor, and a torque component of the stepping motor based on the speed deviation. The object is achieved by comprising correction value calculation means for calculating a correction value of current and means for correcting the current command with the correction value.

  The speed deviation detecting means includes position detecting means for detecting an actual rotational position of the stepping motor, first calculating means for calculating a speed command based on a time change of the position command, and a time change of the rotational position. The second calculating means for calculating the rotation speed of the stepping motor based on the second calculation means and the third calculating means for calculating a deviation of the rotation speed with respect to the speed command can be provided.

  The stepping motor control device according to the present invention includes a position detection unit that detects an actual rotational position of the stepping motor, and a step-out that detects a step-out state of the stepping motor based on a deviation of the actual rotational position with respect to the position command. The apparatus may further include a state detection unit and a switching unit that switches a current command corresponding to the position command to a current command corresponding to the actual rotational position when the step-out state is detected.

  In order to cope with the torque ripple having the period of the number of teeth of the rotor of the stepping motor, a high resolution is required as the position detecting means. Therefore, it is desirable to use a variable reluctance type resolver having the same number of poles as the number of teeth of the rotor of the stepping motor as the position detecting means.

  According to the present invention, the speed deviation detecting means for detecting the speed deviation of the stepping motor, the correction value calculating means for calculating the correction value of the torque current corresponding to the torque fluctuation of the stepping motor based on the speed deviation, And means for correcting the current command with the current command correction value, so that the torque change amount accompanying the control of the torque current does not depend on the load (phase), and the current limit or the torque limit is reached. Divided current control is possible. Therefore, the vibration of the rotor of the stepping motor 10 can always be stably suppressed regardless of the load state.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, a stepping motor (for example, two-phase) 10 is coupled to a position sensor 20 that detects the position of the rotor. Since the torque ripple of the stepping motor 10 depends on the period of the number of teeth of the rotor, a high-resolution position sensor 2 is used as the position sensor 2 in order to control an appropriate motor current corresponding to the torque ripple. It is desirable. Therefore, in this embodiment, a variable reluctance resolver having the same number of poles as the number of teeth of the rotor of the stepping motor 10 is used. In this case, the output signal of the resolver is demodulated by the demodulator 30 into a signal indicating the position of the rotor.

The signal processing unit 40 generates a position command signal (a signal for commanding the target position of the rotor) and a signal indicating the actual position of the rotor (hereinafter referred to as a position detection signal) output from the demodulator 30. A current command value is determined based on this, and this current command value is input to the power amplifier 55.
As shown in FIG. 2, the signal processing unit 40 includes a switching control unit 41, a speed command unit 42, a speed detection unit 43, a step-out prevention switch 44, a current command calculation unit 45, and a vibration suppression current calculation unit. 46 grade. Then, in the signal processing unit 40, a timing · · · t _in the unit interval of time _{Δt, t in-1, ···} , t i-3, t i-2, t i-1, t i, · The position command signal and the position detection signal are sampled by.

The switching control unit 41 monitors the deviation between the position command signal and the position detection signal, and switches and connects the step-out prevention switch 44 to either the terminal a or the terminal b based on the deviation (electrical angle).
The speed command unit 42 includes a difference extraction unit 42a that extracts a difference between the position command signals at the times t _i and t _i−1 , that is, a change of the position command signal at the time Δt as a speed command signal, and an extracted speed command signal. And a low-pass filter 42b that removes the noise component contained therein.
Further, the speed detection unit 43 removes a noise component included in the extracted speed signal, and a difference extraction unit 43a that extracts a difference between the position detection signals at the time t _i and the time t _i-1 as a speed detection signal. And a low-pass filter 43b.

The step-out prevention switch 44 receives a position command signal at the terminal a and a position detection signal at the terminal b. The switching control unit 41 switches and connects the step-out prevention switch 44 based on the deviation between the position command signal and the position detection signal as follows.
(A) When −90 ° ≦ deviation ≦ + 90 °, it is determined that the stepping motor 10 is in a synchronized state, and the step-out prevention switch 44 is connected to the terminal a side. As a result, the ST mode (stepping motor mode) is selected and so-called open loop control is executed.
(B) When −90 °> deviation amount or + 90 ° <deviation amount, it is determined that the stepping motor 10 is in a step-out state, and the step-out prevention switch 44 is connected to the terminal b side. Thereby, the BL mode (brushless motor mode) is selected, and so-called closed loop control is executed.

Hereinafter, the operation of the signal processing unit 40 will be described. In the signal processing unit 40, the step-out prevention switch 44 is normally connected to the terminal a, and in this case, the position command signal is input to the current command calculation unit 45 through the step-out prevention switch 44. Is done.
The current command calculation unit 45 is a current command based on the position command signal, that is, the current command calculation unit 45 is a phase A current command I _Acmd (sin phase current command) and phase B winding for the phase A winding of the stepping motor 10. A B-phase current command I _Bcmd (cos-phase current command) for the line is calculated, and this current command is input to the adder 48.

On the other hand, the subtractor 47 performs a calculation of subtracting the speed detection signal V _FB output from the speed detection unit 43 from the speed command signal V _CMD output from the speed command unit 42, and the speed deviation V _CMD which is the calculation result. −V _FB is input to the vibration suppression current calculation unit 46.
The speed deviation V _CMD −V _FB corresponds to the torque fluctuation (torque ripple) of the stepping motor 10. The torque component current (q-axis current) I _qD corresponding to this torque fluctuation is given by the following equation (1).
I _qD = K _D × (V _CMD −V _FB ) (1)
Here, K _D is a constant.
Therefore, the current command calculation unit 45 uses the torque component current I _qD and the following conversion equation (2) to correct the torque fluctuation, the A-phase vibration suppression current I _AD and the B-phase vibration suppression current I _BD. Is calculated. Note that the parentheses on the right side of Equation (2) are rotation transformation matrices.

ここで、θ_eは前記ステッピングモータ１０の回転子回転位置である。

Here, θ _e is the rotor rotation position of the stepping motor 10.

The A-phase vibration suppression current I _AD and the B-phase vibration suppression current I _BD calculated by the current command calculation unit 45 are input to the adder 48. Accordingly, the adder 48, the A-phase current command I _ACMD to the A-phase vibration suppression current I _AD was added corrected A-phase current command I _ACMD 'and the B-phase current command I _BCMD the B-phase vibration suppression current I _The corrected B-phase current command I _Bcmd 'added with _BD is output.

The A-phase current command I _Acmd ′ and the B-phase current command I _Bcmd ′ are respectively supplied to the A-phase winding and the B-phase winding (not shown) of the stepping motor 10 via the power amplifier 50 shown in FIG. As a result, the stepping motor 10 is driven to rotate.
As described above, the A-phase current command I _Acmd ′ and the B-phase current command I _Bcmd ′ are corrected by the A-phase vibration suppression current I _AD and the B-phase vibration suppression current I _BD . As a result, the driving current of the stepping motor 10 is controlled so that there is no torque fluctuation, and as a result, the vibration of the rotor of the stepping motor 10 is suppressed.

Thus, according to this embodiment, since the vibration of the rotor is suppressed by controlling the torque component current (current proportional to the load torque), compared with the above-described conventional technique, the following The following advantages are obtained.
The stepping motor 10 has a phase-torque (θ-T) characteristic A as exemplified by a solid line in FIG. That is, the torque has a characteristic that changes in a sinusoidal shape with respect to the excitation phase.
The stepping motor 10 having such characteristics rotates around a torque = 0 (phase = 0) when there is no load, and rotates at a phase where the load torque and the motor torque are balanced when there is a load.

In the above-described prior art, the vibration of the rotor of the stepping motor is suppressed by the excitation phase correction process based on the rotational speed deviation of the stepping motor. In this case, torque changes due to phase control (assuming that the phase control amount is the same) when there is no load and when there is load are expressed as ΔT1 and ΔT2, for example. That is, the torque change is greater when there is no load than when there is a load.
Thus, according to the prior art, the amount of torque change accompanying control depends on the load (phase), and the amount of torque change is limited based on the characteristic A. Therefore, depending on the state of the load, vibration may not be sufficiently suppressed.

On the other hand, according to the control device for the stepping motor according to the present embodiment, when a certain torque component current is added to the current command (during torque component current control), θ as illustrated by the dotted line in FIG. -T characteristic B, that is, characteristic B obtained by vertically moving the solid line θ-T characteristic in the torque axis direction is set. The torque change during no load and when there is a load based on this torque component current control is indicated, for example, as ΔT3 and ΔT4 (≈ΔT3), respectively.
Eventually, in the present embodiment for controlling the torque component current, the amount of torque change associated with the control does not depend on the load (phase), and the current can be controlled until the current limit or the torque limit is reached. Therefore, the vibration of the rotor of the stepping motor 10 can be always stably suppressed regardless of the load state.

  When the stepping motor 10 enters the step-out operation state, the step-out prevention switch 44 is switched to the terminal b side by the switching control unit 41, and the current command calculation unit 45 calculates the current command based on the position detection signal. Therefore, the closed loop control is performed so that the stepping motor 10 is in a synchronized operation state. Even in this case, the control for suppressing the vibration of the rotor is continued. When the stepping motor 10 returns to the synchronized operation state, the step-out prevention switch 44 is connected to the terminal a side, so that the motor 10 is again subjected to open loop control based on the position command signal.

  The present invention is not limited to the above-described embodiment, and various modifications and additions are possible. For example, a PWM inverter may be applied instead of the power amplifier 50, and the signal processing in the signal processing unit 40 may be executed by program processing by a microprocessor.

1 is a block diagram illustrating an overall configuration of a stepping motor according to an embodiment of the present invention. It is a block diagram which shows the structural example of a signal processing part. It is the graph which illustrated the torque change by phase control, and the torque change by shunt current control, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Stepping motor 20 Position sensor 30 Demodulator 40 Signal processing part 41 Switching control part 42 Speed command part 43 Speed detection part 44 Step-out prevention switch 45 Current command calculating part 46 Vibration suppression current calculating part 47 Subtractor 48 Adder

Claims (4)

A control device that controls a stepping motor by a current command corresponding to a position command,
A speed deviation detecting means for detecting a speed deviation of the stepping motor;
Correction value calculating means for calculating a correction value of the torque component current of the stepping motor based on the speed deviation;
Means for correcting the current command by the correction value;
A stepping motor control device comprising: The speed deviation detecting means includes
Position detecting means for detecting the actual rotational position of the stepping motor;
First calculating means for calculating a speed command based on a time change of the position command;
Second computing means for computing the rotational speed of the stepping motor based on the time change of the rotational position;
Third computing means for computing a deviation of the rotational speed with respect to the speed command;
The stepping motor control apparatus according to claim 1, further comprising: Position detecting means for detecting the actual rotational position of the stepping motor;
A step-out state detecting means for detecting a step-out state of the stepping motor based on a deviation of the actual rotational position with respect to the position command;
Switching means for switching a current command corresponding to the position command to a current command corresponding to the actual rotational position when detecting the step-out state;
The stepping motor control device according to claim 1, further comprising:   4. The stepping motor control device according to claim 2, wherein the position detecting means is a variable reluctance resolver having the same number of poles as the number of teeth of the rotor of the stepping motor.

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