JPH10150790A - Equipment and method for controlling servo motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain smooth acceleration in rotation by preventing the appearance of foreign sound caused at the rapid acceleration. SOLUTION: In the case that a large deviation exceeding a predetermined value is caused between a speed command value and a detected value by a rapid acceleration command, the pulse width of a PWM driving and controlling signal is so controlled that to may not exceed the restricted predetermined value by the working of a pulse width limiting means of a PWM signal generator 6. By this method, the driving current to be supplied to a servo motor can be increased slowly, no increased rapidly to the limit current value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor control device and a control method for controlling a motor drive by modulating a pulse width of a motor drive control signal by so-called PWM control.

[0002]

2. Description of the Related Art Servo motors controlled by so-called PWM control have been widely known, but a schematic configuration of a control system thereof will be described. For example, as shown in FIG. The rotation speed of the motor is detected by a speed detector 3 through an encoder 2 attached to the motor, and a deviation signal between a speed detection signal issued from the speed detector 3 and a speed command signal issued from a rotation speed commander 4. Is calculated in the comparator 5 and output to the PWM signal generator 6.

The PWM signal generator 6 outputs a PWM control signal (motor drive control signal) to the drive circuit 7 of the servo motor 1, and generates an excitation pulse based on the above-mentioned deviation signal. Has the function of determining the width of

[0004] The drive circuit 7 drives the servo motor 1 based on a PWM control signal from the PWM signal generator 6 and a position detection signal from a pole sensor attached to the servo motor 1. For supplying a current, for example, it is configured as shown in FIG. That is, the drive circuit 7 includes:
A drive element 7a for outputting three-phase drive currents of U-phase, V-phase, and W-phase to the servomotor 1 is provided, and the three-phase drive current from the drive element 7a is controlled based on the above-described PWM control signal. By doing so, the rotation of the servomotor 1 is controlled.

Further, the drive circuit 7 is provided with a drive limiting signal generator 7b for limiting the current supply to the drive element 7a. This drive restriction signal generator 7b
Detects the supply current value to the drive element 7a at all times. If the detected current value exceeds the limit current value determined by the rating of the drive element 7a or the excitation ability of the servomotor 1, the drive element 7a has a function of outputting a limit signal for cutting off the current supply.

Further, the driving element 7a has a circuit configuration as shown in FIG. 8, for example. That is, the drive element 7a appropriately combines the switching elements Up, Vp, Wp on the upper side in the figure and the switching elements Un, Vn, Wn on the lower side in the figure according to the excitation combination determined based on the position detection signal from the pole sensor. The switching elements Up, Vp, and Wp on the upper side of the figure are on / off controlled based on the above-described PWM control signal.

FIG. 9 shows an example of a waveform when the U-phase switching element Up is turned on / off by a PWM control operation. In the case of the illustrated case, the excitation combinations include switching elements Vp, Wp, and U other than switching element Up.
n and Vn are kept in the off state while the switching element W
In the case where n is kept in the ON state, the pulse width of the switching element Up is PWM-controlled while the switching element Up is turned on in synchronization with a predetermined carrier frequency.

[0008] The PWM of such a switching element Up
By the control operation, the U-phase current flows as shown in the lowermost part of FIG. That is, while the switching element Up is on, the U-phase current is supplied through the switching elements Up and Wn, so that the supply current to the motor is increased (Ua), but the switching element Up is off. Then, the U-phase current supply is reduced until the next turn-on (Ub). Therefore, if the pulse width of the switching element Up is appropriately changed by the above-described PWM control operation, the average current Uc of the U-phase current is increased or decreased.

[0009]

However, such a conventional apparatus has a problem that abnormal noise is generated by a sudden acceleration command when a high-speed rotation command is suddenly issued from a motor stopped state. is there. That is, when a large deviation occurs between the speed command value and the detected speed value due to the sudden acceleration command, for example, as shown in the uppermost part of FIG. 10, the pulse width of the PWM control signal Pa becomes the large deviation. Accordingly, the U-phase drive current Ud sharply increases. When the U-phase drive current Ud reaches the limit current value Ioc,
A drive limiting signal is issued from the drive limitation signal generator 7b (see FIG. 7) to the drive element 7a, and the switching elements Up and Wn are turned off.

The off state of both the switching elements Up and Wn is continued until the next rise of the PWM control signal Pa, during which the U-phase drive current continues to decrease. And
The next rise of the PWM control signal Pa causes the U-phase drive current to increase again. In this way, the U-phase drive current becomes a pulsation, and a periodic noise is generated from the motor based on the pulsation.

As a countermeasure, as shown in FIG. 11, when the U-phase drive current Ud reaches the limit current value Ioc and a drive limit signal is issued, the switching element Up is turned off. , Wn remain on. However, in this case, the fall of the U-phase drive current becomes considerably slow, so that the next PW
Even when the M control signal Pa rises, the drive limiting signal continues to operate, and the switching element Up is maintained in the off state. As a result, the cycle of the pulsation is simply extended, and abnormal noise is rather increased. May be.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a servomotor control device and a control method capable of favorably preventing generation of abnormal noise at the time of sudden acceleration and obtaining smooth rotational acceleration. I do.

[0013]

In order to achieve the above object, a servo motor control device according to the present invention comprises a speed command signal generated by a rotation speed commander and a speed detection signal obtained by a rotation speed detector. In a servo motor control device including a PWM control signal generation unit that modulates a pulse width of a drive control signal output to a motor drive circuit in accordance with a deviation from the above, the PWM control signal generation unit includes:
When the rotational acceleration of the motor exceeds a predetermined value, a pulse width restricting means for restricting a pulse width of the drive control signal is provided.

Further, the servo motor control method according to the present invention provides a method for controlling a motor drive circuit corresponding to a deviation between a speed command signal issued from a rotation speed commander and a speed detection signal obtained by a rotation speed detector. In a servo motor control method in which the pulse width of a drive control signal to be output is modulated, the pulse width of the drive control signal is limited when the rotational acceleration of the motor exceeds a predetermined value.

In this invention, when a large deviation exceeding a predetermined value occurs between the speed command value and the detected speed value due to the rapid acceleration command, the PWM signal generating means is operated by the pulse width limiting means. The pulse width of the drive control signal output from the controller is limited so as not to exceed the regulated predetermined pulse width. As a result, the drive current supplied to the servomotor does not immediately reach the limit current value. It grows smoothly.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a servo motor PWM control device according to the present invention will be described below in detail with reference to the drawings. First, in the control device according to the embodiment shown in FIG. 1, the same components as those of the conventional control device shown in FIG. The speed detection signal S1 from the detector 3 is PW
This is a point output to the M signal generator 6.

That is, in the present embodiment, the PWM
The current acceleration state is determined based on the speed detection signal S1 input to the signal generator 6, and when it is determined that the acceleration state is abrupt, the pulse width limiting means provided in the PWM signal generator 6 The PWM control signal is configured to be restricted. Hereinafter, an embodiment of the pulse width limiting means in the PWM signal generator 6 will be described.

First, FIG. 2 shows a structural example of the pulse width limiting means in the PWM signal generator 6 using an analog signal. A deviation signal S2 from a comparator (not shown in FIG. 1) (not shown) is set to be within a range of 0 to 5 V, and a first one-shot multivibrator to which the deviation signal S2 is input. 61 output signal S
3 becomes “H” when the carrier signal S4 output from the carrier signal generation circuit 62 is received as a trigger pulse, and the output signal S3 of the first one-shot multivibrator 61 is changed to an AND gate 63 described later.
You can receive it.

At this time, the first one-shot multivibrator 61 sets the pulse width of the output signal S3 to
The circuit is configured to change linearly in proportion to the deviation signal S2 (0 to 5V). The maximum pulse width is obtained by inputting the maximum deviation signal S1 of 5V.
The maximum pulse width of the output signal S3 is set to be equal to or less than the generation cycle of the carrier signal S4 from the carrier signal generation circuit 62.

On the other hand, the output of the second one-shot multivibrator 64 also becomes "H" by receiving the carrier signal S4 from the carrier signal generating circuit 62 as a trigger pulse. The pulse width of the output signal S5 is determined so as to correspond to the limited voltage signal S6, and the output is performed in synchronization with the generation cycle of the carrier signal S4 from the carrier signal generation circuit 62. I have. In the present embodiment, the voltage of the limited voltage signal S6 is 0 to 5 V
, And the pulse width of the output signal S5 from the second one-shot multivibrator 64 is output from the above-described first one-shot multivibrator 61. It is always maintained at a constant width slightly shorter than the maximum pulse width.

A speed detection signal S1 from the above-described rotation speed detector (see reference numeral 3 in FIG. 1) is applied to the acceleration determination circuit 65. The acceleration determination circuit 65 has a function of calculating the current degree of rotation acceleration based on the speed detection signal S1 and determining whether or not to limit the PWM control signal. If it is determined that there is no limit, the output becomes "H" so as not to perform the restriction,
When it is determined that rapid acceleration is being performed, the output becomes “L” to perform the restriction.

The output signal S7 from the acceleration determination circuit 65
Is input to the OR gate 66 together with the output signal S5 from the second one-shot multivibrator 64, so that either one of these signals S7 and S5 is output from the OR gate 66. Has become. That is, it is determined that rapid acceleration is not being performed, and the acceleration determination circuit 6
5 while the output of the OR gate 6 is "H".
The output from the second one-shot multivibrator 64 is not output from the OR gate 66, because the output from the output 6 is also kept at the "H" state. On the other hand, when it is determined that rapid acceleration is being performed and the output of the acceleration determination circuit 65 becomes "L", the output from the OR gate 66 becomes the output signal S5 from the second one-shot multivibrator 64. .

Further, the output from the OR gate 66 is input to the AND gate 63 together with the output from the first one-shot multivibrator 61, and the output of the shorter one of the two output signals is output. Is output from the AND gate 63 as a PWM control signal.

That is, since it is determined that rapid acceleration is not being performed, the output of the acceleration determination circuit 65 becomes "H" and the OR gate 6
6 is maintained in the “H” state, the PWM output from the AND gate 63 is the output signal S3 from the first one-shot multivibrator 61. On the other hand, when it is determined that rapid acceleration is being performed and the output of the acceleration determination circuit 65 becomes “L” and the output from the OR gate 66 becomes the output signal S5 from the second one-shot multivibrator 64, Of the output signals S3 and S5 from the first and second one-shot multivibrators 61 and 64, the output having the smaller pulse width, that is, the output having a constant pulse width from the second one-shot multivibrator 64 The signal S5 is output from the AND gate 63 as a PWM control signal. With this, PWM
This means that the control signal is restricted.

In the control method using the control device according to the embodiment, when a large deviation exceeding a predetermined value occurs between the speed command value and the detected speed value due to the rapid acceleration command, the PWM is used. By the action of the pulse width limiting means provided in the signal generator 6, the PWM signal generator 6
The pulse width of the PWM drive control signal output from is controlled so as to be shorter than the original pulse width, and is regulated so as not to exceed a predetermined pulse width.

This control method will be described in more detail with reference to FIG.
This will be described with reference to FIG. First, following the rapid acceleration command, the first
The output pulse width from the one-shot multivibrator 61 is extended as shown in FIG. 3 (a).
The output of the PWM signal generator 6 shown in FIG.
The output from the second one-shot multivibrator 64 has a constant short and long pulse width.

The PW limited to this short and long pulse width
For example, if the ON time of the switching element Up is controlled to be short as shown in FIG. 3C in accordance with the output of the M signal generator 6, it is supplied to the servomotor as shown in FIG. The U-phase drive current Uf smoothly increases without immediately reaching the limit current value Ioc, and pulsation as in the related art is prevented.

In this case, if the speed detection signal S1 is input as the limit voltage signal S6 to be input to the second one-shot multivibrator 64 for limiting the pulse width, the second one-shot multivibrator 64 can be used. The width of the limit pulse output from the shot multivibrator 64 changes according to the rotation speed. That is, in this case, it is possible to limit the PWM control signal according to the counter electromotive force of rotation. Therefore, at a low speed in which the counter electromotive force is small and the current pulsation is large, a larger restriction is applied and the counter electromotive force is increased. At high speeds with small current pulsations, the restriction can be relaxed and current pulsations can be effectively prevented.

The limiting voltage signal S input to the second one-shot multivibrator 64 on the pulse width limiting side.
Assuming that 6 is appropriately controlled from the outside,
It is possible to arbitrarily set the limitation of the PWM control signal.

On the other hand, in the embodiment shown in FIG.
Although the pulse width limiting means in the PWM signal generator 6 in the above-described embodiment is replaced with a device using a digital signal, the replaced portion will be described.

A deviation signal generated by a comparator (not shown) is input to the load data of the first counter 71 as 8-bit binary data, and the load data of the second counter 72 has an 8-bit limit. The data is entered. The clock signal from the oscillator 73 is
The signals are input to the first and second counters 71 and 72 as operation signals, and are also input to a carrier signal generation circuit 74.

The carrier signal generating circuit 74 outputs a carrier signal obtained by dividing the clock signal from the oscillator 72 by 256 to the first and second counters 71 and 72 as a load signal. Both counters 71,
Reference numeral 72 denotes a down counter which sets the output BRO to "H" when the data is other than "0" data. When the output BRO becomes "0" after the clock corresponding to the load data, the output BRO becomes "L". And the counter operation is stopped when the enable input E becomes "L". Then, the counter operation time at this time is set as the output pulse time.

The other parts operate in the same manner as the control device according to the embodiment shown in FIG. 2 and thus will not be described. However, in this case, the limit data is also fixed. In such a case, when the speed detection value is used as the limit data, or when the limit data is externally adjusted, the same operation and effect as those of the above embodiment can be obtained.

FIG. 5 shows another embodiment.
An example of a comparator 51 for similarly controlling a PWM signal by the control system shown in FIG. 6 is shown. The arithmetic circuit 51a provided in the comparator 51 has a function of multiplying a difference between the speed command signal a and the speed detection signal b by a coefficient K to obtain a deviation output C (C = K × (ab)). And
The coefficient K is obtained by inputting a table designation to the data table 51b.

At this time, as the table designation input to the data table 51b, a fixed value is selected, and the data table 51b includes the acceleration limit data,
Normal limit data is allocated, and data is selected by a signal of the acceleration determination circuit 65. When the limiting data at the time of acceleration is selected, the coefficient K is made to correspond to 0.5. At the time of selecting the normal limiting data, the coefficient K is set to 1 so that the deviation is distinguished according to the state of acceleration.
(0.5).

In this case, if a speed detection signal is input to the table designation input and the contents of the data table 51b are changed according to the rotation speed, it is possible to execute the deviation limit according to the rotation speed of the motor. Becomes If the table designation input is controlled from the outside, the coefficient K
Can be controlled while appropriately changing the value of.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say. For example, in the above embodiment, the drive current of the U phase is described, but the same applies to the drive currents of other phases. Further, in the above embodiment, the control operation at the time of the start of rotation of the motor is described, but the present invention can be similarly applied not only to the start of rotation but also to any sudden acceleration.

Further, the present invention can be similarly applied to various kinds of motors regardless of the presence or absence of a DC machine, an AC machine, and a brush.

[0039]

As described above, the servo motor control apparatus and control method according to the present invention provide a servo motor control method in which a sudden acceleration command causes a large deviation exceeding a predetermined value between a speed command value and a detected speed value. In addition, the operation of the pulse width limiting means of the PWM signal generating means limits the pulse width of the PWM drive control signal so as not to exceed a regulated predetermined pulse width, thereby limiting the drive current supplied to the servomotor to the limited current. Since the value is smoothly increased without immediately reaching the value, generation of abnormal noise at the time of sudden acceleration can be satisfactorily prevented, smooth rotational acceleration can be obtained, and the reliability of the motor is improved. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a servomotor P according to an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a WM control device.

FIG. 2 is a block diagram showing an embodiment of a PWM signal generating means in the PWM control device shown in FIG. 1;

FIG. 3 is a timing chart at the time of rapid acceleration controlled by the PWM signal generation means according to FIG. 2;

FIG. 4 is a block diagram illustrating a structure of a PWM signal generating unit according to another embodiment of the present invention.

FIG. 5 is a block diagram showing a structure of a PWM signal generating means according to still another embodiment of the present invention.

FIG. 6 is a block diagram showing a PWM control device in a general servo motor.

FIG. 7 is a block diagram illustrating a configuration example of a motor drive circuit.

FIG. 8 is a block diagram illustrating a configuration example of a drive element provided in a motor drive circuit.

FIG. 9 is a timing chart illustrating an example of PWM control.

FIG. 10 is a timing chart illustrating an example of a case where a conventional PWM control device starts rotating a motor.

FIG. 11 is a timing chart showing another example of starting rotation of a motor by a conventional PWM control device.

[Explanation of symbols]

 Reference Signs List 3 rotation speed detector 6 PWM signal generator 61 first one-shot multivibrator 62 carrier signal generation circuit 63 AND gate 64 second one-shot multivibrator 65 acceleration determination circuit 66 OR gate 71 first counter 72 second Counter 73 Oscillator 74 Carrier signal generation circuit 51 Comparator 51a Operation circuit 51b Data table

Claims (5)

[Claims] A pulse width of a drive control signal output to a motor drive circuit is modulated in accordance with a deviation between a speed command signal issued from a rotation speed commander and a speed detection signal obtained by a rotation speed detector. In a servo motor control device provided with a PWM control signal generation means, the PWM control signal generation means includes a pulse width restriction means for restricting a pulse width of the drive control signal when a rotational acceleration of the motor exceeds a predetermined value. A control device for a servomotor, comprising: 2. The pulse width restricting means according to claim 1, wherein the pulse width of the drive control signal is limited to a predetermined fixed pulse width when the rotational acceleration of the motor exceeds a predetermined value. A control device for a servo motor, comprising: 3. The pulse width restricting means according to claim 1, wherein when the rotational acceleration of the motor exceeds a predetermined value, the pulse width of the drive control signal is limited to a pulse width proportional to the rotational speed of the motor. A control device for a servo motor, comprising: 4. The pulse width restricting means according to claim 1, further comprising a function of restricting a pulse width of the drive control signal to an appropriately selected pulse width when the rotational acceleration of the motor exceeds a predetermined value. A servo motor control device. 5. A pulse width of a drive control signal output to a motor drive circuit is modulated in accordance with a deviation between a speed command signal issued from a rotation speed commander and a speed detection signal obtained by a rotation speed detector. A servo motor control method according to claim 1, wherein the pulse width of said drive control signal is limited when the rotational acceleration of said motor exceeds a predetermined value.