JP4491401B2 - Motor driving circuit and motor driving method - Google Patents

Description

  The present invention relates to a motor drive circuit and a motor drive method, and more particularly to a motor drive system that controls the timing of switching between a drive phase current and a drive phase.

  Conventionally, a stepping motor is driven with a drive profile that starts at a low drive frequency (drive speed) first and then gradually increases the drive frequency.

  As described above, the stepping motor has a feature that the speed control and the position control can be easily performed only by controlling the drive frequency and the number of pulses. However, since the stepping motor rotates in synchronization with the drive pulse, An appropriate drive frequency must be determined in consideration of the load.

  For example, if a motor with a small load is driven at a slow speed relative to the torque of the motor, the motor vibrates. If the load is large and the operating frequency is fast, the motor cannot synchronize and step out. .

  As a method for driving the above stepping motor, there is a method disclosed in Japanese Patent Laid-Open No. 2003-235296 (Patent Document 1) issued by the Japan Patent Office. That is, in a stepping motor driving method that performs acceleration and deceleration driving with a predetermined driving profile via a gear transmission mechanism that has a backlash and is constituted by an elastic body, at least at the time of startup, the amount of displacement due to the backlash and the elastic body is reduced. In the corresponding acceleration region, driving is performed at a speed faster than the minimum speed. Then, after this driving, the stepping motor is accelerated and decelerated based on a driving profile in which the speed is switched to the minimum speed and accelerated sequentially.

By doing so, it is possible to prevent the occurrence of vibration and noise at the time of starting due to backlash and the amount of displacement by the elastic body, and to drive the stepping motor without stepping out.
JP 2003-235296 A

  The driving method of the stepping motor disclosed in Patent Document 1 described above is a method in which the stepping motor is driven early in a section where there is play (backlash) in the system, and then the speed is sequentially accelerated from the lowest speed. This technique assumes that there is play in the system when feeding at a high speed, so that it is difficult to apply to a system with large fluctuations in play. That is, in this method, if there is no play during feeding at high speed and the load increases, there is a risk of step-out, and if feeding is slow while the play is large and the load is small, vibration may increase.

  This problem occurs, for example, when a carriage that performs scanning for scanning such as a copying machine is driven by a gear. In other words, the carriage needs to repeat scanning and returning operations, and naturally there is a difference (referred to as machine difference) for each copying machine in the play of the gear when the returning operation is finished and the scanning is started. The amount of play fluctuates each time the same machine is started.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a motor drive circuit and a motor drive method capable of solving the above problems and accelerating the motor to the through region without being affected by the magnitude of backlash. .

The motor drive circuit according to the present invention comprises:
A motor drive circuit for accelerating the motor to a through region with a predetermined profile in a system in which at least play of the system due to backlash and deformation is large, and the play varies due to machine differences and fluctuations at each start,
After starting the motor, the motor is sequentially decelerated toward the lowest speed, and the rotation angle from the start of the motor to the lowest speed is set to be substantially larger than the backlash, and the motor from the start of the motor to the lowest speed is set. And a control circuit for setting the driving current to be smaller than the driving current of the motor in the section from the lowest speed toward the through region.

The motor driving method according to the present invention includes:
A motor driving method for accelerating a motor to a through region with a predetermined profile in a system in which at least play of the system due to backlash and deformation is large and the play varies due to machine differences and variations at each start-up,
After starting the motor, the motor is sequentially decelerated toward the lowest speed, and the rotation angle from the start of the motor to the lowest speed is set to be substantially larger than the backlash, and the motor from the start of the motor to the lowest speed is set. It has a drive control step of setting a drive current to be smaller than the drive current of the motor in a section from the lowest speed toward the through region.

  That is, in the motor drive circuit of the present invention, in a system in which the play of the system such as backlash and deformation is large and the play fluctuates at each start, the rotation angle from the start of the motor to the lowest speed is set larger than the backlash. In addition, prior to accelerating the stepping motor to the through region, when the play of the system is larger than the backlash, a speed reduction section that starts at a high speed and then sequentially decelerates is provided. In this case, the current for driving the stepping motor is set smaller than the subsequent acceleration section to the through region, thereby making it difficult for vibration to occur.

  Further, in the motor drive circuit of the present invention, when the backlash that is the play of the system is sufficiently small, the backlash becomes zero almost simultaneously with the start-up, and the driven object generates a relatively large vibration. That is, in the stepping motor drive circuit of the present invention, assuming a sufficiently large reduction ratio and a complete elastic collision, an initial speed that is twice the speed at which the driven object collides is obtained, and then the elasticity (spring characteristics) of the drive system is obtained. Oscillates at the natural frequency of the system constituted by the inertia of the driven object and attenuates due to the viscosity of the system.

  When the backlash of the system is sufficiently large, the backlash becomes zero near the lowest speed, and the driven object generates a relatively small vibration. In other words, the vibration has an initial speed that is twice the minimum speed.

  In the motor drive circuit of the present invention, since the ratio between the speed at the time of start-up and the minimum speed is set to be approximately equal to the ratio (amplitude attenuation ratio) at which the vibration amplitude of the system in the deceleration zone attenuates, acceleration is started. At this point, the amplitude of vibration is approximately equal when the backlash is maximum and minimum.

  Thus, in the motor drive circuit of the present invention, as described above, the vibration at the start of acceleration can be made almost equal and small regardless of the magnitude of the backlash, so that it is not affected by the magnitude of the backlash. In addition, the stepping motor can be accelerated to the through region.

  Further, in the motor drive circuit of the present invention, the stepping motor is driven at a high speed at the beginning, so that the time for driving the same distance is shortened compared with the case where the motor is driven at a low speed from the beginning. It is possible to reduce the required time.

  Further, in the motor drive circuit of the present invention, since the current of the stepping motor is reduced in the section where the backlash exists in the system, vibration in this section is less likely to occur, and further, the feeding at a constant speed is not performed. Vibration is less likely to grow and operation is stable.

  With the configuration and operation described below, the present invention provides an effect that the motor can be accelerated to the through region without being affected by the size of the backlash.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a stepping motor driving circuit according to an embodiment of the present invention. In FIG. 1, a stepping motor driving circuit according to an embodiment of the present invention includes a control circuit 1 having a profile table 11, a driving circuit 2 for driving a stepping motor (M) 3, and a program executed by the control circuit 1. And a recording medium 4 to be stored.

  The profile table 11 stores data for decelerating and accelerating the stepping motor 3. The control circuit 1 sequentially reads data from the profile table 11 and controls the control lines (current setting signal 101 and control pulse 102) to the drive circuit 2.

  The drive circuit 2 sequentially switches the phase for driving the stepping motor 3 in accordance with the control pulse 102 from the control circuit 1. Further, the drive circuit 2 sets the magnitude of the current supplied to the stepping motor 3 in accordance with the current setting signal 101 from the control circuit 1. Since current control and phase switching of the stepping motor 3 are general techniques, a detailed description thereof will be omitted.

FIG. 2 is a diagram showing a configuration example of the profile table 11 of FIG. FIG. 3 is a diagram showing the response (Ya, Yb) of the system according to an embodiment of the present invention. The straight line portions X1, X2 correspond to the input of the system, and the rotation of the stepping motor 3 is approximated linearly. Is. FIG. 4 is a sequence chart showing operations of the control circuit 1 and the drive circuit 2 of FIG. The operation of the stepping motor driving circuit according to one embodiment of the present invention will be described with reference to FIGS. The operation of the control circuit 1 shown in FIG. 1 is realized by executing the program of the recording medium 4.

  When receiving a start signal (not shown), the control circuit 1 sequentially reads data from the profile table 11, and outputs a current setting signal 101 and a control pulse 102 to the drive circuit 2 based on the data (a1 to a4 in FIG. 4). ).

  The drive circuit 2 sequentially switches the phase for driving the stepping motor 3 in accordance with the control pulse 102 from the control circuit 1. The drive circuit 2 sets the magnitude of the current supplied to the stepping motor 3 in accordance with the current setting signal 101 from the control circuit 1 (a5 in FIG. 4).

  As shown in FIG. 2, each entry of the profile table 11 includes data and a tag indicating the type of the data. The tag of the first data in the profile table 11 is “Tag A”, which indicates that this data is current setting data. Therefore, the control circuit 1 outputs “L 1” to the current setting signal 101.

  The tag of the next data in the profile table 11 is “Tag B”, and this data represents the time until the control pulse 102 is output. Therefore, the control circuit 1 outputs a control pulse 102 after T10. Thereafter, the control circuit 1 outputs control pulses 102 at intervals determined by the data in the profile table 11 until T1n. Here, from T10 to T11,..., T1n, the intervals determined by the data in the profile table 11 are set so that the time gradually increases.

This will be explained in comparison with the response shown in FIG.
T10 = α / V0
T1n = α / Vmin
T10 <T11 <...... <T1n
It becomes. Here, V0 is the initial speed at start-up, and Vmin is the lowest speed. Α is a constant determined by the reduction ratio of the system. That is, the steps so far correspond to the deceleration section T1 shown in FIG.

Since the tag of the next data in the profile table 11 is “Tag A”, this data is current setting data. Therefore, the control circuit 1 outputs “L 2” to the current setting 101. L2> L1. Hereinafter, the control circuit 1 outputs the control pulse 102 at intervals of T20, T21,..., T2m. This section corresponds to the acceleration section T2 shown in FIG.
T20>T21>……> T2m
It is.

  As described above, for each of the deceleration section T1 and the acceleration section T2 shown in FIG. 3, the current setting signal 101 is “L1” and “L2”, and the control pulse 102 is the intervals T10, T11,..., T1n and T20, T21. ,..., T2m are output. As a result, as shown in FIG. 3, when the play is sufficiently small, the response of the system follows the locus of Ya, and when the play is sufficiently large, the response of the system follows the locus of Yb.

  In the trajectory of the response Ya when the play is small as shown in FIG. 3, the amplitude of the vibration is large in the initial stage, but the amplitude is attenuated as time passes. In the locus of the response Yb when the play is large, the input speed is small, so the amplitude of vibration is small from the beginning.

  In this example, according to the vibration amplitude, the ratio between the speeds V0 and Vmin is made substantially the same as the rate at which the amplitude of the natural vibration of the system decays from the start to the minimum speed (amplitude decay rate). Thus, at the start of the section T2, the vibration amplitude can be made equal for both Ya and Yb. Therefore, at the time when acceleration is started (starting point of the section T2), the amplitude of vibration is almost equal regardless of whether the backlash is maximum or minimum.

  In FIG. 3, the point in time when Yb starts to move from "0" corresponds to the point in time when the backlash becomes zero. This is from the start of the motor (V0) to the minimum speed (Vmin). This means that the rotation angle is set substantially larger than the backlash. Thus, the reason why the motor rotation angle is set to be substantially larger than the backlash is as follows.

  That is, when the backlash becomes zero (or disappears), if the motor speed is large, the vibration of the driven object increases and the motor starts to accelerate (from the deceleration section T1 in FIG. 3 to the acceleration section). When the backlash is eliminated (when shifting to T2), the motor will continue to be accelerated with large vibrations, and in the worst case, the motor will step out. Therefore, in the present invention, the rotation angle from the start of the motor to the lowest speed is set to be substantially larger than the backlash.

  Next, the operation of making the current I1 in the deceleration zone T1 smaller than the current I2 in the acceleration zone T2 will be described based on specific data. FIG. 5 is a diagram showing a response example Ya4 in which acceleration is stably performed according to an embodiment of the present invention. FIG. 6 shows that the current in the deceleration section T1 is too large and the stepping motor 3 vibrates to cause a step-out. It is a figure showing the example of response Ya5.

  Like the response Ya5 shown in FIG. 6, the driven object is temporarily stopped from the middle, and the vibration of the driven object thereafter is much larger than that in FIG. This is because the stepping motor 3 has stepped out during the response Ya5. Low-speed step-out tends to occur when the torque of the stepping motor 3 is too large compared to the load, and can generally be prevented by reducing the current of the stepping motor 3.

  It should be noted that the current setting in the section T1 should be set as small as possible within a range in which the stepping motor 3 can be stably started by itself at a pulse interval T10 corresponding to the speed V0 without any play with respect to the driven object. Needless to say.

  In this way, in this embodiment, the vibration at the start of acceleration can be made substantially equal and small regardless of the magnitude of the backlash, so that the stepping motor 3 can be bypassed without affecting the magnitude of the backlash. Accelerate to the area.

  In this embodiment, the current in the stepping motor 3 is made smaller (I1 <I2) in the deceleration zone T1 where the system has backlash than in the acceleration zone T2, so that vibration in this zone T1 is less likely to occur. Become. Further, since the feed is not performed at a constant speed, the vibration of the stepping motor 3 is difficult to grow, so that the operation can be stabilized.

  In the present invention, even if the motor 3 is not a stepping motor, it can be applied if speed control is possible. For example, in the case of a servo motor, there is no need to control the drive current, but before acceleration, a deceleration zone from medium speed to low speed is secured larger than the play of the system, and the speed ratio between medium speed and low speed is ensured. Is substantially matched to the damping rate of the vibration of the system in the deceleration zone, so that the vibration of the system during acceleration can be effectively reduced.

It is a block diagram which shows the structure of the stepping motor drive circuit by one Example of this invention. It is a figure which shows the structural example of the profile table of FIG. FIG. 4 is a diagram illustrating the response of a system according to an embodiment of the present invention. 2 is a sequence chart illustrating operations of a control circuit and a drive circuit in FIG. 1. It is a figure which shows the example which performed acceleration stably by one Example of this invention. It is a figure which shows the example which stepped motor vibrated and caused step-out because the electric current in deceleration area T1 was too large.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control circuit 2 Drive circuit 3 Stepping motor 4 Recording medium 11 Profile table

Claims (12)

A motor drive circuit for accelerating the motor to a through region with a predetermined profile in a system in which at least play of the system due to backlash and deformation is large, and the play varies due to machine differences and fluctuations at each start,
After starting the motor, the motor is sequentially decelerated toward the lowest speed, and the rotation angle from the start of the motor to the lowest speed is set to be substantially larger than the backlash, and the motor from the start of the motor to the lowest speed is set. A motor drive circuit comprising: a control circuit for setting the drive current of the motor to be smaller than the drive current of the motor in a section from the lowest speed toward the through region. The motor is linearly decelerated from the start to the lowest speed, and the ratio between the start speed and the lowest speed of the motor is attenuated in the time from the start of the motor to the lowest speed. 2. The motor driving circuit according to claim 1, wherein the motor driving circuit is substantially the same as the rate of the motor driving.   The motor drive circuit according to claim 1, wherein the control circuit includes a profile table that stores data for decelerating and accelerating the motor.   4. The motor drive circuit according to claim 3, wherein the profile table stores at least current setting data for the motor and data of time until a pulse is output to the motor. The profile table, prior to the motor to accelerate to the through region, when the play of the system is greater than said backlash is initially provided with a section for sequentially decelerate started at high speed, this Stores data set so that the current for driving the motor becomes smaller than when accelerating to the through region in the section where the vehicle is sequentially decelerated,
5. The motor drive circuit according to claim 4, wherein the control circuit sequentially reads out the data from the profile table and sequentially executes drive control of the motor.   6. The motor drive circuit according to claim 1, wherein the motor is a stepping motor. A motor driving method for accelerating a motor to a through region with a predetermined profile in a system in which at least play of the system due to backlash and deformation is large and the play varies due to machine differences and variations at each start-up,
After starting the motor, the motor is sequentially decelerated toward the lowest speed, and the rotation angle from the start of the motor to the lowest speed is set to be substantially larger than the backlash, and the motor from the start of the motor to the lowest speed is set. A motor drive method comprising: a drive control step of setting a drive current to be smaller than a drive current of the motor in a section from the lowest speed toward the through region. The drive control step includes a step of linearly decelerating from starting of the motor to the lowest speed,
The ratio between the starting speed and the minimum speed of the motor is substantially the same as the rate at which the amplitude of the natural vibration of the system decays in the time from the starting of the motor to the minimum speed. Motor drive method.   9. The motor drive method according to claim 7, wherein the drive control step performs drive control of the motor using a profile table storing data for decelerating and accelerating the motor.   10. The motor driving method according to claim 9, wherein the profile table stores current setting data for the motor and time data until a pulse is output to the motor. Prior to accelerating the motor to the through region, the profile table is provided with a section that starts at a high speed and decelerates sequentially when the play of the system is larger than the backlash. Stores data set so that the current for driving the motor becomes smaller than when accelerating to the through region in the section where the vehicle is sequentially decelerated,
11. The motor driving method according to claim 10, wherein in the driving control step, the data is read from the profile table and the driving control of the motor is sequentially executed.   The motor driving method according to claim 7, wherein the motor is a stepping motor.

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