JP2007037320A - Drive method and drive device for stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive method and a drive device for a stepping motor which can avoid a step-out phenomenon, and can drive the stepping motor efficiently. <P>SOLUTION: In this drive method for the stepping motor, a current controller 8 which detects a current supplied to the stepping motor 1 and determines an output voltage sent to a voltage command operating part 6 based on this detected current and a current command is provided, and a voltage command value for motor drive is determined based on the output voltage (V<SP>*</SP>) sent from the current controller 8 and a positional command (θ*) signal sent from the outside. The stepping motor 1 is provided with a positional detector 5 that detects a rotor position (θ<SB>m</SB>), and deviation between the positional command (θ*) and the rotor position(θ<SB>m</SB>) is calculated from the detection signal of the rotor position(θ<SB>m</SB>) and the positional command (θ*), and a current signal (i<SP>*</SP>) outputted to the current controller 8 is outputted from the calculation result. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stepping motor driving method and a driving apparatus capable of driving a stepping motor with high efficiency and avoiding a step-out phenomenon.

Conventionally, the following techniques are known as a method for driving this type of stepping motor.
1. A method of adjusting the excitation position while viewing the position signal (Patent Document 1).
2. A method of controlling the motor current with the converter output current (Patent Document 2).
3. A method of performing current control by detecting a torque load with a winding voltage of a stepping motor (Patent Document 3).
4). A method of adjusting the distribution of current instructions between the stepping motor controller and the servo motor controller (Patent Document 4).
JP-A-2-23100 Japanese Patent No. 3158093 JP 2000-236696 A JP 2004-328821 A

However, the above prior art has the following problems.
In the method of Patent Document 1, since the excitation position is adjusted while looking at the position signal, the step-out phenomenon can be avoided, but high-efficiency operation cannot be realized.
In the method of Patent Document 2, since the motor current is controlled by the converter output current, an experiment is required to determine the current value for the target load, and the step-out phenomenon cannot be avoided.
Furthermore, in the method of Patent Document 3, torque load is detected by the winding voltage of the stepping motor and current control is performed. Therefore, the method cannot be used other than the stepping motor in which the winding is configured in a ring shape. Therefore, the step-out phenomenon cannot be avoided.
Furthermore, since the method of Patent Document 4 is a method of adjusting the current instruction distribution between the stepping motor controller and the servo motor controller, the ratio of current distribution must be adjusted in advance by the load.

  The present invention solves the above-mentioned problems, can be applied to microstep drive, does not require a special motor, and provides a position detector in the stepping motor, calculates the deviation between the position indication and the rotor position, and the calculation result A stepping motor driving method capable of driving the stepping motor with high efficiency and avoiding a step-out phenomenon by increasing / decreasing the current flowing from the stepping motor to the stepping motor according to the load and controlling the excitation position of the stepping motor; An object is to provide a drive device.

In order to solve the above problems, the present invention provides a current control unit that detects a current supplied to the stepping motor and determines an output voltage to be sent to the voltage command calculation unit based on the detected current and the current command. A stepping motor driving method for determining a voltage command value of a motor drive based on an output voltage sent from a current control unit and a position command signal sent from outside,
A position detector is provided in the stepping motor to detect a rotor position, a deviation between the command position and the rotor position is calculated from the rotor position detection signal and the position command signal, and the current control unit is calculated from the calculation result. Is to output a current command signal to be output.
The present invention also includes a current control device that detects a current supplied to the stepping motor and determines an output voltage to be sent to the voltage command calculation device based on the detected current and the current command, and is sent from the current control device. A stepping motor driving device for determining a voltage command value of a motor drive from the voltage command calculation device based on an output voltage and a position command signal sent from outside, and a position detection for detecting a rotor position of the stepping motor A position deviation calculating device that receives a detection signal of the position detector and the position command signal and calculates a deviation between the command position and the rotor position from the rotor position detection signal and the position command signal. And a current command calculation device to which a position deviation signal calculated by the position deviation calculation device is input. It is to determine the current command to be sent to the control device.
Further, according to the present invention, a switch for selectively switching the position command signal and the detection signal of the position detector is provided in a circuit for sending the position command signal to the voltage command calculation device.

According to the present invention, the effects listed below can be obtained.
Since the winding voltage of the stepping motor is not detected at the time of excitation switching in order to detect the step-out phenomenon, it can be applied to microstep driving.
In order to avoid the step-out phenomenon, a detection motor or the like is not used in the motor, so no special motor is required.
Since no detection winding or the like is used, a special detection circuit is not required and calculation can be performed by the CPU.
Since the position detector to be used only needs to be able to determine whether or not the load angle exceeds ± π / 2, a high-resolution position detector is not required.

The embodiments shown in the drawings will be described in detail below with reference to the drawings.
In FIG. 1, reference numeral 1 denotes an N-phase stepping motor, and the N-phase stepping motor 1 is connected to an AC power supply 4 via a motor driver 3. The AC power supply 4 supplies power to the motor driver 3, and the motor driver 3 supplies power to the N-phase stepping motor 1. A current detector 2 is provided between the N-phase stepping motor 1 and the motor driver 3, and the current detector 2 is connected to the current control device 8. A current command calculation device 10 is connected to the current control device 8, and a current command i ^* is input from the current command calculation device 10. The constant current command i ^* and the N-phase AC current i _N detected by the current detector 2 are input to the current control device 8, which outputs the magnitude V of the output voltage sent to the voltage command calculation device 6. ^* Determined. On the other hand, the position command θ ^* is input to the voltage command calculation device 6 via the changeover switch 7. The changeover switch 7 has a switch s for switching the contact point a and the contact point b, and the switch s is switched to either the contact point a or the contact point b via the operation switching device 11. The contact a is supplied from the position instruction theta ^*, to the contact b side is to output theta _m of the position detector 5 is supplied.

  If the switch s of the changeover switch 7 is set to the contact a side, the electrical angle that is the input of the voltage command calculation device 6 becomes the position command θ *, and the voltage command calculation device 6 determines the N-phase voltage command value VN. The N-phase stepping motor 1 is driven by being supplied with a constant current with a sinusoidal amplitude.

Here, θ _m that is the output of the position detector 5 of the N-phase stepping motor 1 and the position command θ ^* are input to the position deviation calculation device 9 to calculate the position deviation θ _err .
The position deviation computing device 9 is connected to the current command computing device 10 and the operation switching device 11, and the position deviation θ _err computed by the position deviation computing device 9 is sent to the current command computing device 10 and the operation switching device 11.
Position deviation calculation unit positional deviation theta _err calculated at 9 determines the current command i ^* by the current command computation unit 10 which receives the computed positional deviation theta _err.
Further, in the operation switching device 11 that _receives the position deviation θ _err , which of the position command θ ^* or the output θ _m of the position detector 5 is used for the electrical angle used in the voltage command calculation device 6 is used. decide. In the changeover switch 7 based on this result, the electrical angle used theta ^*, which switches the theta _m.

Next, taking the two-phase stepping motor as an example, the operation of the above embodiment will be described.
The field α and β-phase electric coil winding interlinkage magnetic flux numbers Φ _f α and Φ _f β of the two-phase stepping motor are expressed by the following equations when the maximum value is Φ _f ′.

Here, the theta _re a rotor position taken clockwise relative to the α-phase armature winding (electrical angle).
In general, in driving a stepping motor, an excitation position is determined regardless of a rotor position, and a phase field controlled to a constant current is generated and driven at an electric angular velocity corresponding to an indicated rotation speed. The current at this time is represented by the following equation.

  Since the torque generated by the stepping motor is expressed as the sum of products of the current of each phase and the number of flux linkages, the following equation is obtained.

Since the number of interlinked magnetic fluxes in the above formula is a motor-specific constant, the generated torque of the stepping motor is determined by the load angle theta ^* - [theta] _re the current i. FIG. 2 shows the torque generated by the stepping motor with respect to the load angle.
If the current i is constant from the equation (5), the generated torque becomes the maximum value when the load angle θ ^* −θ _re is + π / 2 and becomes the minimum value when −π / 2.

In general, a constant current driving method in which a current is constant is used as a stepping motor driving method. However, if the current value is constant, power is supplied to the stepping motor regardless of the load, so that all excess power is lost.
Therefore, when torque is generated in the positive rotation direction, the current is controlled so as to keep the load angle θ ^* -θ _re at + π / 2, and when torque is generated in the negative rotation direction, the load angle θ ^* -θ _{re is set} to If the current is controlled so as to maintain −π / 2, maximum efficiency operation can be realized. However, if the load angle θ ^* −θ _re exceeds ± π / 2, the stepping motor will cause a step-out phenomenon, and will be out of synchronization and cannot rotate.

Therefore, high-efficiency operation was realized by controlling the current according to the load angle θ ^* -θ _re . In practice, the stability of the stop is an advantage of the stepping motor is impaired resulting in the current instruction i ^* to zero, the rated if the load angle theta ^* - [theta] _re was a small value of about [pi / 8 The current instruction is set to about 1/4 of the current, and when the current instruction is exceeded, the current instruction is gradually increased. This is shown in FIG.

When θ _m which is the output of the (rotation) position detector 5 is attached in accordance with the rotor position θ _re , the load angle θ ^* −θ _re can be obtained by θ ^* −θ _m . This calculation is performed by the position deviation calculation device 9. A current instruction for the load angle as shown in FIG. 3 is calculated and determined by the current instruction arithmetic unit 10 from the positional deviation θ _err equal to the load angle θ ^* −θ _re , and the stepping motor is operated efficiently by controlling the current. Is realized.

If the required torque is increased, the current instruction is increased, but there is an upper limit value of the set current due to the rated current of the motor and the restriction of the power circuit. If this is exceeded, a step-out phenomenon will occur and the motor will stop.
Therefore, when the position deviation θ _err is likely to exceed ± π / 2, the switching switch 7 is switched from the contact a to the contact b by the operation switching 11.
At this time, the current instruction becomes the maximum value, and the load angle θ ^* −θ _re is fixed at π / 2, so the generated torque is expressed by the following equation.

When the required torque falls below the value of equation (6), the positional deviation θ _err gradually decreases.
When the position deviation θ _err is within ± π / 2, the operation switch 11 switches the switching switch 7 from the contact b to the contact a.
As can be seen from the above description, the position detector used in the present invention only needs to be able to determine whether or not the load angle exceeds ± π / 2, and therefore does not require a high-resolution position detector.
Further, since no detection winding or the like is used for the motor in order to avoid the step-out phenomenon, no special motor is required.
Furthermore, since no detection winding or the like is used in the motor, a special detection circuit is not required, so that calculation by the CPU is possible.

  In the case of a three-phase, five-phase stepping motor, the expression of induced electromotive force and the definition of the current are required for the number of phases, and the phase difference in the formula is 2π / 3 for three phases and 2π / 5 for five phases. However, the generated torque is expressed by equation (5), and the same control is possible.

FIG. 4 shows another embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and the description of the same parts is omitted.
In this case, the resolution adjusting device 12 is provided on the output side of the position detector 5, and the output of the rotation detector 5 combined with the position command (position indication) θ * is connected to the contact b via the resolution adjusting device 12. θ _m is supplied.
Therefore, even if the resolution of the position detector 5 is not matched with the resolution of the microstep drive, it is possible to match the position command θ * by placing the resolution adjusting device 12 at the output of the position detector 5.
This can be realized even by using a low-resolution position detector.
In the present invention, since the winding voltage of the stepping motor is not detected at the time of excitation switching for step-out detection, the present invention can be applied to microstep driving.

According to the above embodiment, the following effects can be obtained.
Since the winding voltage of the stepping motor is not detected at the time of excitation switching in order to detect the step-out phenomenon, it can be applied to microstep driving.
In order to avoid the step-out phenomenon, a detection motor or the like is not used in the motor, so no special motor is required.
Since no detection winding or the like is used, a special detection circuit is not required and calculation can be performed by the CPU.
Since the position detector to be used only needs to be able to determine whether or not the load angle exceeds ± π / 2, a high-resolution detector is not required.
Even if the resolution of the position detector 5 is not matched with the resolution of the microstep drive, the position command θ * can be matched by placing the resolution adjusting device 12 at the output of the position detector 5.
Therefore, since it can be realized even by using a low-resolution position detector, a high-resolution position detector is not required. In this way, the current flowing through the stepping motor can be increased or decreased according to the load, and the step-out phenomenon can be avoided by controlling the excitation position of the stepping motor.

  Needless to say, the present invention is not limited to the above-described embodiment, and can be implemented with appropriate modifications within the scope not changing the gist of the present invention.

1 is a system configuration diagram showing an embodiment of a stepping motor driving apparatus according to the present invention. FIG. It is a figure which shows the relationship of the generated torque with respect to the load angle of a stepping motor. It is a characteristic view showing the relationship between the current instruction and the load angle for driving the stepping motor with high efficiency. It is a system block diagram which shows other embodiment of the drive device of the stepping motor by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 N phase stepping motor 2 Current detector 3 Driver 4 AC power supply 6 Voltage command calculating device 8 Current control device 9 Position deviation calculating device 10 Current command calculating device 11 Operation switching device

Claims (3)

A current control unit that detects the current supplied to the stepping motor and determines the detected current and an output voltage to be sent to the voltage command calculation unit based on the current command is provided. The output voltage sent from the current control unit and the external A stepping motor driving method for determining a voltage command value of a motor drive based on a position command signal sent from
A position detector is provided in the stepping motor to detect a rotor position, a deviation between the command position and the rotor position is calculated from the rotor position detection signal and the position command signal, and the current control unit is calculated from the calculation result. A stepping motor driving method comprising: outputting a current command signal to be output to the stepping motor. A current control device that detects the current supplied to the stepping motor and determines an output voltage to be sent to the voltage command calculation device based on the detected current and the current command is provided. The output voltage sent from the current control device and the external A stepping motor drive device that determines a voltage command value of the motor drive from the voltage command calculation device based on a position command signal sent from the position command signal, provided with a position detector for detecting the rotor position of the stepping motor, A position deviation calculation device is provided for receiving a detection signal of a position detector and the position command signal, and calculating a deviation between the command position and the rotor position from the rotor position detection signal and the position command signal. A current command calculation device is provided to which the position deviation signal calculated by the calculation device is input, and the current command calculation device sends the current command calculation device to the current control device. Drive of the stepping motor, characterized by determining the flow command. 3. The stepping motor according to claim 2, wherein a circuit for sending the position command signal to the voltage command calculation device is provided with a selector switch for selectively switching the position command signal and the detection signal of the position detector. Drive device.

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