JPH07230320A - Servo control device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the vibration of the controlled object that occurs when changing the gain or control amount, and shorten the positioning time. [Configuration] At least one integral compensator 2 and other types of compensators 3 are provided, and a command to a control target is given with a deviation signal e between a target value signal Pr and a control amount signal P of the control target 1 as an input. In a servo control device comprising a compensating means for outputting a value u, and a changing means 4 for changing the gain or control amount type of each compensator in the compensating means,
An integral value correcting means 5 for correcting the integral value held in the integral compensator so that the command values output by the compensating means substantially match immediately before and immediately after the changing by the changing means.
1 and 6 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo controller which is used in a semiconductor printing apparatus, an XY table of a machine tool, or the like and which requires high-speed and highly accurate positioning.

[0002]

2. Description of the Related Art In a servo control device that requires high-speed and highly accurate positioning, it is frequently necessary to change the gain or the control amount according to the purpose of control. For example, during speed control, the gain of the compensator is changed at the time of acceleration, constant speed, deceleration, etc., and the gain is changed according to the deviation even during position control. In addition, a control method using both speed control and position control is often used. This is a method that uses speed control capable of moving at a high speed for a large movement from a stopped state to near the target position, and uses position control for accurate positioning near the target position. In this case, the input to each compensator and the gain are changed at the time of switching from the speed control to the position control and at the time of switching from the position control to the speed control.

On the other hand, a normal servo control device includes at least one integral compensator for making the steady deviation zero. The integral compensator has a memory function of holding the integral value of the values input to the integral compensator up to the present. However, when the input to the integrator is changed, such as when switching between speed control and position control, the value held until then becomes meaningless. Therefore, in such a case, the integrated value is reset to zero.

FIG. 10 is a block diagram of a conventional servo controller. Control amount of controlled object 1 (position or speed)
2) is subtracted from a target value detected by a detector (not shown) and input to each compensator. The compensator comprises an integral compensator 2, a proportional compensator 31, and a differential compensator 32, and the command value for the controlled object 1 is determined by PID control. The gain of each compensator can be changed by the gain changing means 4 as needed. FIG. 11 is a graph showing the change over time in the command value when changing the gain.

[0005]

However, when the change in the gain is large, as shown in FIG. 11, the value of the command value may change abruptly before and after the change in the gain, causing the controlled object to vibrate. It was Also, when switching the control amount (switching between speed control and position control, etc.), in addition to changing the gain, the input to each compensator changes and the value held in the integrator is also reset to zero. The change in the command value is often even greater. The abrupt change of the command value includes various frequency components over a wide band, and this causes resonance with the natural vibration of the controlled object, vibrates the controlled object, and is a cause of extending the positioning time.

On the other hand, compensators other than the integral compensator determine an appropriate command value at that time from the current state of the controlled object and the gain. However, since the integral value held in the integral compensator depends on the gain and control amount before change and the behavior of the controlled object up to the present, it has an appropriate value for the gain and control amount after change. There is no guarantee. Also, when the control amount is changed, it is reset to zero, but this is also a convenient measure because the integrated value up to that point does not make sense, and it is an appropriate value for the changed gain and control amount. There is no guarantee that it will. For this reason, it takes time to converge to an appropriate value for the gain and the control amount after the integrated value is changed, which also causes the extension of the positioning time.

SUMMARY OF THE INVENTION In view of the above problems of the prior art, an object of the present invention is to prevent the vibration of the controlled object that occurs when the gain or the control amount is changed, and shorten the positioning time in the servo control device.

[0008]

In order to achieve this object, the present invention has at least one or more integral compensators and compensators of other types, and provides a target value signal and a signal of a controlled variable to be controlled. In the servo control device, the compensating means outputs the command value for the controlled object by inputting the deviation signal and the changing means for changing the gain or control amount type of each compensator in the compensating means. Integral value correcting means for correcting the integrated value held in the integral compensator is provided so that the command values output by the compensating means are matched immediately before and immediately after.

As means for correcting the integral value, for example, command value holding means for holding the command value output by the compensating means immediately before the change by the changing means, and the command value held thereby and the changing means. Based on the command value output by the compensating means immediately after the change by, the integral value correcting means for correcting the integrated value held in the integral compensator so that the command values before and after the change substantially match. Or a command value generating means for generating a command value immediately after the change based on the command value before the change by the changing means, and the command value generated thereby and the compensating means immediately after the change by the changing means. Integral value correcting means for correcting the integral value held in the integral compensator based on the instruction value so that the instruction values before and after the change substantially match. Those having falls. In these cases, there is provided a means for setting the command value held by the command value holding means or the command value generated by the command value generating means as the command value for the controlled object immediately after the change by the changing means. May be.

[0010]

According to the present invention, the command value immediately after the change of the gain or the like is substantially equal to the command value immediately before the change in the simple structure by adding only the command value holding means or the command value generating means and the integral value correcting means. Since the value held in the integrator is corrected as described above, a rapid change in the command value that occurs when the gain or the like is changed is suppressed, and the vibration of the controlled object is prevented. Further, if the state of the controlled object is the same, the command value should be the same regardless of the gain and the control amount. Therefore, correcting the value held in the integrator so that the command value immediately after changing the gain etc. is approximately equal to the command value immediately before changing the gain etc. will affect the integrated value before changing the gain or control amount. Instead, the integral value is corrected to a value that is appropriate for the state after the change of the gain or control amount. Therefore, the time required for convergence of the integrated value is shortened, and the positioning time is shortened.

[0011]

【Example】

(Embodiment 1) FIG. 1 is a block diagram of a servo controller according to a first embodiment of the present invention. In this device, the control amount (position or speed) P of the controlled object 1 is detected by a detector (not shown), and the difference e from the target value Pr is input to each compensator. The compensator comprises an integral compensator 2, a proportional compensator 31, and a differential compensator 32.
The command value to the controlled object 1 is determined by the D control. The gain of each compensator can be changed by the gain changing means 4. The command value holding means 51 holds the command value determined by each compensator, and outputs it to the integral value correction means 6 as necessary. The integral value correcting means 6 determines the integral value by comparing the value of the instruction value holding means 51 with the current instruction value, and corrects the integral value held in the integral compensator 2.

FIG. 2 is a flow chart during the sampling period when the gain is changed in this apparatus.
Now, the command value u (t-1) in the sampling period immediately before the gain change is held in the command value holding means 51. Then, the gain of each compensator is changed at the beginning of the sampling period in which the gain is changed. Alternatively, the gain may be changed at the end of the sampling period immediately before that. After changing the gain, the control amount P and the target value Pr of the controlled object 1 are read into each compensator, and the command value u (t) is calculated by each compensator. At this time, the integrator updates the integrated value based on the input value and sets a new integrated value i (t). The command value u (t) and the command value u (t-1) in the immediately preceding sampling period held by the command value holding means 51 are read by the integral value correcting means 6 and the corrected integral value is calculated. The integral value is corrected so that the command value u (t) calculated by using the command value u (t) becomes equal to the command value u (t-1) in the immediately preceding sampling period held by the command value holding means 51. Further, as the command value in this sampling period, the command value holding means 51
The command value u (t-1) in the immediately previous sampling period held by is output.

The correction method performed by the integral value correction means 6 is as follows.
It depends on the integral value held by the integral compensator 2. First,
When the integral compensator 2 holds the input integrated value of the deviation e, i ′ (t) = i (t) − (u (t) −u (t−1)) / ki (equation The integrated value i '(t) corrected by 1) is determined. Here, ki is the integral gain after the change. Second
In addition, when the integral compensator 2 holds the integrated value of the deviation e multiplied by the gain, i '(t) = i (t)-(u (t) -u (t-1)) The integrated value i '(t) corrected by (Equation 2) is determined.

Even when the control amount is changed at the same time as the gain is changed (speed control and position control are switched),
The integral value is corrected by the exact same procedure.

The abruptly changed command value u contains various frequency components over a wide band, and this causes resonance with the natural vibration of the controlled object 1 and vibrates the controlled object 1. However, by correcting the integral value in this way, as shown in FIG. 3, the command value does not suddenly change before and after the gain change and the control amount change, and as a result, the controlled object is vibrated. Things will disappear.

Further, by correcting the value held in the integrator so that the command value immediately after the gain change becomes equal to the command value immediately before the gain change, a value appropriate for the state after the gain / control amount change is obtained. Since the time for the integrated values to converge can be saved,
The positioning time can be shortened.

Furthermore, in order to realize these effects, only the command value holding means 51 and the integral value correction means 6 for performing the calculation of the above equation 1 or 2 should be added. The calculation time required for these is short, and the sampling period is hardly extended.

(Embodiment 2) FIG. 4 is a block diagram of a servo controller according to a second embodiment of the present invention. It differs from the first embodiment in that the command value holding means 51 is replaced by a command value estimating means 52 for estimating a command value in the current sampling period from a past command value. The integral value correcting means 6 determines the integral value by comparing the command value estimated by the instruction value estimating means 52 with the current command value, and corrects the integral value held in the integral compensator 2.

FIG. 5 is a flow chart during the sampling period when the gain is changed in this apparatus. This is different from the first embodiment in that the command value estimating means 52 estimates the estimated value us (t) of the command value at the current sampling from the command value up to the sampling period immediately before the gain change. Then, the gain of each compensator is changed at the beginning of the sampling period in which the gain is changed. Alternatively, the gain may be changed at the end of the sampling period immediately before that. After changing the gain, the controlled variable P of the controlled object 1
And the target value Pr are read, and the command value u is read by each compensator.
(T) is calculated. At this time, the integrator updates the integrated value based on the input value e, and a new integrated value i (t)
Is set. On the other hand, the command value estimating means 52 estimates the estimated value us (t) of the command value in the current sampling period. This estimation may be performed in the immediately preceding sampling period. The command value u (t) and the estimated value us (t) of the command value in the current sampling period are integrated value correcting means 6
And the integrated value is corrected so that the command value calculated using the corrected integrated value becomes equal to us (t). Furthermore, as the command value in this sampling period,
The estimated value us (t) of the command value in the current sampling period is output.

The correction method performed by the integral value correction means 6 is as follows:
It depends on the integral value held by the integral compensator 2. First,
When the integral compensator holds the input integrated value of the deviation, it is corrected by i '(t) = i (t)-(u (t) -us (t)) / ki (Equation 3) The integrated value i '(t) thus determined is determined. Here, ki is the integral gain after the change. Second
In addition, when the integral compensator 2 holds the integrated value of the deviation e multiplied by the gain, i ′ (t) = i (t) − (u (t) −us (t)) (equation The integrated value i '(t) corrected by 4) is determined.

Even if the control amount is changed at the same time as the gain is changed (switching between speed control and position control, etc.),
The integral value is corrected by the exact same procedure.

In the first embodiment, the same command value is output during the sampling period in which the gain is changed and the sampling period immediately before that. Therefore, when the command value is changing, the change of the command value is interrupted. On the other hand, in the second embodiment, since the change in the command value is estimated, the command value can be output more smoothly, as shown in FIG. On the other hand, more computation time is required than in the first embodiment due to the amount required for estimation. In order to estimate the command value, the first-order approximation using the command values of the past two samples is the simplest, but more accurate estimation can be performed by using more command values. However, the amount of calculation required for the estimation increases accordingly, and more sampling time is required.

(Embodiment 3) FIG. 7 is a block diagram of a servo controller according to a third embodiment of the present invention. It differs from the first embodiment in that it does not have a path for outputting the command value held in the command value holding means 51.

FIG. 8 is a flow chart in the sampling period immediately before the gain is changed in this apparatus. The difference from the first embodiment is that the operation related to the integral value correction is performed in the sampling period immediately before the gain is changed.
The control amount P and the target value Pr of the controlled object are read in the sampling period immediately before the gain is changed, and the command value u (t-1) is calculated by each compensator. This command value u (t-1) is output as a command value in the sampling period immediately before the gain change and is held in the command value holding means 51.
Next, the gain of each compensator is changed, and the command value u (t) is calculated using the new gain. When the control amount is changed, the command value u is changed using the changed control amount and the target value.
(T) is calculated. At this time, the integrator updates the integrated value and sets a new integrated value i (t). This command value u (t) and the command value u (t-1) in the previous sampling period held by the command value holding means 51.
Is read by the integral value correction means 6 and the command value calculated using the corrected integrated value is held by the command value holding means 51 in the previous sampling period command value u (t-
The integral value is corrected so as to be equal to 1). The formula used for the correction is the same as that in the first embodiment. In the next sampling period, the command value is calculated using the corrected integral value and the changed gain.

In this embodiment, the correction of the integral value is performed in the sampling period immediately before the gain is changed, so that the command value can be calculated using the corrected value in the sampling period in which the gain is changed. Therefore, it is not necessary to output a command value based on a past value such as a command value in the immediately preceding sampling period or an estimated command value, and a command value based on a smooth and current control amount / target value is output. be able to.
However, in the sampling period immediately before the gain change, the compensator calculates the command value twice, so that the amount of calculation is increased to about twice and the sampling time may be significantly increased.

(Embodiment 4) FIG. 9 is a block diagram of a servo controller according to a fourth embodiment of the present invention. The difference from the first embodiment is that a state feedback compensator 33 is provided instead of the proportional compensator 31 and the derivative compensator 32. The flowchart in the sampling period in which the gain is changed and the formula for correcting the integral value are also the same as those in the first embodiment except that the state feedback compensator 33 is used instead of the proportional compensator 31 and the derivative compensator 32. .

Compared with the PID compensator, the state feedback compensator 33 has a higher degree of freedom in gain setting and can change the gain more greatly. Therefore, the change of the command value due to the gain change tends to be large. The correction of the integrated value according to the present invention is effective. Similarly in the second and third embodiments, the state feedback compensator 33 may be used instead of the proportional compensator 31 and the differential compensator 32. Further, in Examples 1 to 3, as the compensator 3 other than the integral compensator, compensators other than the proportional compensator 31, the differential compensator 32, and the state feedback compensator 33 may be used.

[0028]

As described above, by adding only the command value holding means or the command value generating means and the integral value correcting means, the command value immediately after the change of the gain or the like becomes approximately equal to the command value immediately before the change. By correcting the value held in the integrator, it is possible to eliminate a sudden change in the command value that occurs when the gain is changed, so that the controlled object does not vibrate and the positioning time It can be shortened. In addition, since it is possible to correct the integrated value to a value that is appropriate for the state after the change of the gain or control amount without being affected by the integrated value before the change of the gain or control amount, the time required for the convergence of the integrated value. Can be omitted, and the positioning time can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram of a servo control device according to a first embodiment of the present invention.

2 is a flowchart showing the operation of the apparatus of FIG.

3 is a schematic diagram showing how the command value changes when the gain is changed in the apparatus of FIG.

FIG. 4 is a block diagram of a servo controller according to a second embodiment of the present invention.

5 is a flowchart showing the operation of the apparatus of FIG.

FIG. 6 is a schematic diagram showing how the command value changes when the gain is changed in the apparatus of FIG.

FIG. 7 is a block diagram of a servo controller according to a third embodiment of the present invention.

FIG. 8 is a flowchart showing the operation of the apparatus of FIG.

FIG. 9 is a block diagram of a servo controller according to a fourth embodiment of the present invention.

FIG. 10 is a block diagram of a servo control device according to a conventional example.

11 is a schematic diagram showing how the command value changes when the gain is changed in the apparatus of FIG.

[Explanation of symbols]

1: Control object, 2: Integral compensator, 3: Compensator other than integral compensator, 31: Proportional compensator, 32: Differential compensator,
33: state feedback compensator, 4: gain changing means, 51: command value holding means, 52: command value estimating means,
6: integral value correcting means, P: control amount, Pr: target value, e:
Deviation, u: command value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/68 K

Claims (4)

[Claims] 1. At least one integral compensator and other types of compensators are provided, and a deviation signal between a target value signal and a control amount signal of a controlled object is input and a command value for the controlled object is output. In a servo control device comprising a compensating means and a changing means for changing the gain or control amount type of each compensator in the compensating means, a command for holding a command value output by the compensating means immediately before the change by the changing means Based on the value holding means and the command value held thereby and the command value output by the compensating means immediately after the change by the changing means, the integral compensator is configured so that the command values before and after the change substantially match. Integral value correcting means for correcting the held integral value, and the command value immediately before the change held in the command value holding means for the controlled object immediately after the change A servo control device comprising: 2. At least one integral compensator and other types of compensators are provided, and a command value for the controlled object is output by inputting a deviation signal between the target value signal and the signal of the controlled variable of the controlled object. In a servo control device comprising a compensating means and a changing means for changing the gain or control amount type of each compensator in the compensating means, a command value immediately after the change is generated based on the command value before the change by the changing means. Based on the command value generating means, and the command value generated thereby and the command value output by the compensating means immediately after the change by the changing means, the integral compensation is performed so that the command values before and after the change substantially match. Integral value correcting means for correcting the integral value held in the container, and the command value generated by the command value generating means as the control target immediately after being changed by the changing means. And a means for setting a command value for the servo control apparatus. 3. At least one integral compensator and other types of compensators are provided, and the command value for the controlled object is output by inputting the deviation signal between the target value signal and the signal of the controlled variable of the controlled object. In a servo control device comprising a compensating means and a changing means for changing the gain or control amount type of each compensator in the compensating means, a command for holding a command value output by the compensating means immediately before the change by the changing means Based on the value holding means and the command value held thereby and the command value output by the compensating means immediately after the change by the changing means, the integral compensator is configured so that the command values before and after the change substantially match. A servo control device, comprising: an integral value correcting means for correcting the held integral value. 4. Having at least one or more integral compensators and other types of compensators, and outputting a command value for a controlled object by inputting a deviation signal between a target value signal and a signal of a controlled variable of the controlled object. In a servo control device including compensating means and changing means for changing the gain or control amount type of each compensator in the compensating means, the command value output by the compensating means is almost equal to immediately before and immediately after the changing by the changing means. An integral value correcting means for correcting the integral value held in the integral compensator so that they coincide with each other.