JPH0736546A - Positioning controller and stage device using the controller - Google Patents

Abstract

PURPOSE:To perform the highly accurate and stable positioning control in a short time by calculating and corresponding a deviated variable after confirming a fact that a controlled system is set in a steady state. CONSTITUTION:A steady state detecting part 2 periodically reads the values of secondary sensors 1-n to store them with these sensors defined as the inputs. Then the part 2 reads a pair of data out of a storage 3 to retrieve the maximum and minimum values out of these data and confirms whether the difference between both values is smaller than the stable width or not. When it is decided that the value of each sensor reaches a steady state, the part 2 outputs the present values 1-n. A comparing part 4 compares the target values 1-n given from a host master with the present values 1-n sent from the part 2. A command value generating part 5 outputs the command values 1-m to the drive control parts 11-1m based on the output of the part 4. Then the control outputs 1-m are transmitted so that the drive control parts 11-1m are coincident with the primary sensors 1-m respectively. Thus the feedback control is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device used in a general automatic machine, and particularly to a control system for controlling a stable target object with an offset from a target value, and a stable drive unit. The present invention relates to a control system when a delay occurs until the target stabilizes after the start.

[0002]

2. Description of the Related Art Conventionally, in a control system of this type, as represented by a servo driver, a Near occurring at a certain point in time when a difference between a target value and a current value enters a predetermined tolerance. It was recognized that the driving was completed by checking the bit.

[0003]

The control system for recognizing the completion of driving by using the above Near bit has the following problems.

1. If overshoot occurs in the hunting state when the drive is stopped, as shown in FIG.
Multiple ear bits are generated, and it is mistakenly recognized that the driving is completed.

2. It cannot be used in a system with an offset. This is because when the target object stabilizes at a value with an offset from the target value, the deviation does not become small in the control system configured as described above, and thus the Near bit does not occur, resulting in a timeout error. Will end up. The cause of the offset may be 1) when an operational amplifier is used as a difference circuit of the feedback loop as shown in FIG.

Even if the offset voltage of the operational amplifier itself is adjusted, the resistance value of the input stage (R1 and R2)
There is always an error within the standard. Since the output voltage is expressed by the following equation (1), the resistance value R1 of the input stage is
And R2 differ from each other, the deviation becomes 0 although the target value and the current value are actually different, and the deviation becomes stable there.

-V (deviation) = (Rf / R1) × V (target) -Rf / R2 × V (current) (1) This error is very small, but it is a highly accurate control system. Can't be ignored.

2) Change in posture of controlled object (pitching, etc.)
Therefore, even if the driving point reaches the target value, the measurement point may be stabilized at a value having an offset from the target value.

3) When the drive axis and the measurement axis are different, it is easy to stabilize with a value having an offset.

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and an object of the present invention is to realize a control device capable of performing precise and highly stable control in a short time.

[0011]

The positioning control device of the present invention comprises a measuring means for measuring the position of a controlled object, a calculating means for calculating a deviation amount between a current value and a target value of the controlled object, and a calculating means. In a positioning control device comprising a control signal output means for generating and outputting a control signal for driving a controlled object according to the obtained deviation amount, a steady state confirmation means for confirming that the controlled object has entered a steady state is provided. It is characterized by having.

In this case, after confirming that the controlled object has entered the steady state by the output of the steady state confirmation means,
The shift amount may be obtained.

The steady state confirmation means may select a part of the information obtained through the measurement means and recognize that the steady state has been entered when the variation in the selected information becomes small. .

In this case, it means that the variation is small.
It may be judged that the difference between the maximum value and the minimum value is small, and that the variation is small may be judged that the variance is small.

The stage apparatus of the present invention is characterized in that the stage is controlled by any one of the positioning control apparatuses described above.

[0016]

In the present invention, since the deviation amount is obtained after it is confirmed that the controlled object is in the steady state, the deviation amount becomes accurate, and erroneous recognition at the time of overshoot or the like is avoided. . Further, even in a servo system that is stable with an offset, an erroneous shift amount is not generated by confirming that the steady state has been entered. Therefore, it is possible to appropriately and promptly correct the deviation amount.

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram describing the configuration of an embodiment of the present invention. In the figure, 11 to 1m are a first drive control unit to an mth drive control unit (m is an integer of 1 or more). The first drive control unit 11 to the m-th drive control unit 1m output the control output 1 to the control output m so that the command value 1 to the command value m and the primary sensor 1 to the primary sensor m respectively, and perform feedback control. It is carried out. Reference numeral 2 denotes a steady state detection unit, which receives the secondary sensor 1 to the secondary sensor n as input, periodically reads the sensor value, and stores it in the storage device 3. And
When it is detected that each sensor value has reached the steady state, the current values 1 to n are output. n is an integer of 1 or more like m. Reference numeral 4 denotes a comparison unit that compares target values 1 to n given by a master (not shown), which is higher than the present system, with current values 1 to n output from the steady state detection unit 2. Reference numeral 5 denotes a command value generation unit, which outputs command values 1 to 1st drive control unit 11 to m-th drive control unit 1m based on the output of the comparison unit 4.
The command value m is output.

In the above embodiment, the steady state detecting section 2 is described as inputting the secondary sensors 1 to n, but one steady state detecting section 21 to 2n is provided for each secondary sensor. May be. In addition, a plurality of secondary sensors can be input to one steady state detection unit, and a steady state detection unit of 2 or more and less than n can be provided.

The current value output by the steady state detection unit 2 is obtained by diverting the data obtained at the time of steady state detection, which will be described later,
There is a method of setting the average value of the secondary sensor values of several times in the past or an intermediate value of the maximum value and the minimum value, or it is possible to newly read the secondary sensors 1 to n and set the current value. ,
Various methods are possible.

Further, the steady state detecting section 2 can always output the present value and output the steady state signal when the steady state is detected.

FIG. 2 shows an example of the controlled object according to the present invention. The figure shows a stage movable in the XY directions.

A Y stage 205 is provided on the base 206. X stage 204 on Y stage 205
Is provided, and an object 203, which is a control target object in this embodiment, is placed thereon.

The Y stage 205 is driven by a motor 207 that rotates according to a control output from a drive control unit (not shown). The amount of rotation of the motor 207 is the encoder 2
08 and is input to the drive control unit as a primary sensor input.

On the other hand, the position of the object 203 is measured by the laser interferometer 201 which irradiates the laser beam 202, and is input to the steady state detection unit (not shown) as a secondary sensor input.

The X-axis has the same structure as the Y-axis. However, if attention is focused only on the Y stage, the control system with n = 1 and m = 1 in FIG. 1 is applied.

Next, the operation of the control device of the present invention will be described with reference to the flow chart shown in FIG.

First, a target value of the Y stage is input from a master (not shown) (step S301). Then, the command value is output to the drive control unit (step S30).
2). In the case of the first time, the command value may be the target value, or the command value may be calculated after calculating the deviation amount using the current value output from the steady state detection unit.

However, as shown in FIG.
03, tilt stage 402 on Y stage 404
In the case where there is an inclination and there is an inclination, the command value does not necessarily match the target value. In the figure, when the Y coordinate of the center of the object 401 to the Y ₀ Y Y coordinate of the center of the stage and the Y _S, the Y ₀ and Y _S △ difference Y occurs.

It is also conceivable that the scale of the laser interferometer and the scale of the encoder have an error in scale, and the measured values are different at the same position. In such a case, if the target value is corrected to obtain the command value, the number of times of driving is reduced,
Can be positioned faster.

When the command value is output in step S302, the drive control unit outputs a control signal so that the encoder value becomes equal to the command value, drives the motor, and eventually becomes stable. After that, it waits until the output of the laser interferometer, which is the input of the secondary sensor, reaches a steady state (step S30).
3). A specific stability check method will be described later.

In such a case, it is general to use a stability check timer to confirm that the stability is achieved within a prescribed time, instead of waiting indefinitely. If it does not stabilize within the specified time, an error occurs.

Before the above step S303, it may be possible to wait for the Y stage to reach a steady state by referring to the encoder output which is the primary sensor. Similar to step S303, the stability check method described later may be used in this step, but a method of confirming that the difference between the command value and the sensor value is less than the tolerance may be used as in the conventional method. However, when the difference circuit as described above is used in the feedback loop, it is necessary to take measures such as increasing the tolerance and strictly adjusting the gain.

When the object is observed when the Y stage reaches the steady state, it is not always in the steady state. This is because there is an X stage between the Y stage and the object, and many other components may exist. When there are such a plurality of constituent elements, their spring components act respectively, so it takes time from the stabilization of the Y stage to the stabilization of the object.

By doing so, the stability check timer of the Y stage and the stability check timer of the object can be set independently, and the stability check timer of the object can be started when the encoder output is in a steady state. Then, the stability check timer of the object has an advantage that an appropriate timer value can be set regardless of the driving amount of the Y stage and an error can be detected early.

When it is confirmed that the output of the laser interferometer has reached a steady state, then the deviation amount is obtained (step S30).
4). The calculation formula for obtaining the shift amount is the following formula (2).

Deviation amount = target value-current value (2) In the model shown in FIG. 2, some causes of the deviation amount between the target value and the current value will be described.

1) Backlash, backlash, etc. of the transmission system 2) By changing the posture of the stage (pitching, etc.)
The object 203 tilts and does not reach the target value.

3) The object 203 is displaced because there is another component in the Y direction due to another drive axis.

4) Laser interferometer 201 and encoder 20
8 because there is a scale error between the laser interferometer 201 and the encoder 208, even if the value indicated by the encoder 208 becomes the command value, the laser interferometer 201
Then, it does not go to the target value.

Although not applicable to the model shown in FIG. 2, if a measuring instrument having a non-linearity component such as a capacitance sensor is used as the primary sensor, it may not reach the target value due to the linearity error. .

For these reasons, drive-in drive may be required.

The control operation will be described with reference to FIG. 3 again.

After obtaining the shift amount in step S304,
The calculated shift amount is compared with the preset tolerance to determine whether or not the drive-in drive is necessary (step S305). If the absolute value of the deviation amount is within the tolerance, the drive is not performed and the present processing is ended. If the absolute value of the deviation amount is outside the tolerance, the Y stage is driven in drive, so the deviation amount calculated in step S304 is added to the command value to obtain a new command value. Then, the process returns to step S302 and the above-mentioned processing is repeated.

However, it is normal that the number of times of drive-in is not unlimited, and if the number of times of drive-up reaches the limit value, it is judged as an error.

Although the position control has been described in the above embodiment, the same applies to the case where speed control is performed.

Next, the stability check method used in step S303 will be described in detail with reference to FIG.

The steady-state detector 2 periodically reads the secondary sensor input obtained from the laser interferometer, and stores it in the storage device 3.
And the stable state is evaluated by using the past k consecutive data stored as one set.

The evaluation criteria in the first stability check method performed by the steady state detector 2 will be described with reference to the flowchart shown in FIG.

The steady state detection unit 2 reads a set of data from the storage device 3 (step S501), retrieves the maximum value and the minimum value from them (step S502), and sets them as Max and Min. Then, it is confirmed whether the difference between Max and Min is less than or equal to a predetermined stability width (step S503). If it is less than or equal to the stability width, it is recognized that the steady state is reached, and the stability check is ended. .
If the difference between Max and Min is larger than the stable width,
It is judged that it is not in the steady state yet, the evaluation is performed using another set with new data added, and if it is not so, the evaluation is repeated until it stabilizes.

The above-mentioned stability check method will be specifically described below with reference to the drawings.

FIG. 6 shows an example of a graph in which the vertical axis represents the position of the object 203 and the horizontal axis represents time in the model of FIG.

When speed control is performed, the vertical axis represents the speed of the object 203.

In the figure, for example, k = 5.
At time t = t5, the data obtained in t1 ≦ t ≦ t5 is evaluated as one set. If yi is the data obtained when t = ti, Max is y1 and Min is y3. Then, the difference between Max and Min, Δy5, is obtained and compared with the stability width ε.

Δy5 = y3−y1 The stability width ε is not shown, but if Δy5> ε,
Judging that it is not stable yet, at the time of t = t6, y2 ~
Reassess using y6.

In this way, when yi-4 to yi are evaluated, if Δyi ≦ ε, it is confirmed that the steady state is reached.

Next, the evaluation criteria of the second stability check method performed by the steady state detector 2 will be described.

In the second stability check method as well, as in the first stability check method, continuous k pieces of data are evaluated as one set.

In the second stability check method, the square of the difference between the average of the measured values of the past k times from the measurement time point and the data obtained this time is averaged for k times to obtain the variance, and this variance is set in advance. If it is within the stable width, it is assumed that the steady state is reached, and will be described below with reference to the flowchart (FIG. 7) and the graph (FIG. 8).

First, the total SUM of the k data so far
This time's data is added, and the data before k times is subtracted to obtain a total S
The UM is updated (step S701), the total SUM is divided by k, and the average of the past k times is calculated. In FIG. 8, the position variation of the object is shown by a solid line, and the average when k = 5 is shown by a broken line. For example, the position of the broken line at t = t5 indicates the average value of y1 to y5.

Next, the current data is subtracted from the average to obtain the current difference (step S703). As an example, t =
The difference at t5 is shown in FIG.

Subsequently, the square of the difference this time is added to the sum of squares of the difference k times in the past, the square of the difference k times before is subtracted, and the sum of squares is updated (step S704). When updated, t = t
When 5, the sum of squares is the sum of squares of difference 801 to difference 805.

Subsequently, the updated sum of squares is divided by k to obtain the variance (step S705), and it is further determined whether the variance is within the specified stability range (step S706). If the dispersion is within the stable range, it is recognized that the steady state has been reached, and the stability check ends. If it is not within the stable width, it is determined that the steady state has not been reached yet, the process returns to step S701, and another set with new data is used for evaluation again.

In the stability check method as described above, since the measured data changes greatly at the beginning,
The average also changes with time, but the average becomes stable as it approaches a steady state. Further, since the average has a time delay with respect to the data, the difference takes a large value during the fluctuation. In the steady state, the average hardly moves, and the measured data vibrates within the range of steady vibration, so the difference becomes small and the dispersion falls within the stable range.

It is possible to perform this check all the time and refer to it when necessary, or to activate this check only when necessary. In the latter case, although not shown in FIG. 7, the total SUM of the measurement data is updated after the stability check is started until the k measurement data are obtained, and the average of the past k pieces is obtained. Then, a process for obtaining the difference of the current value from the average and further accumulating the square of the difference for k times is performed.

In both the first and second stability check methods, as described above, the stability check timer is set, and if it does not become stable within the specified time, there is some other cause, so error processing is performed as a stability error. I do.

In both the first and second stability checking methods, the sampling interval is preferably set to the extent that steady vibration can be reproduced, and k is set to about one cycle.

Since the first method is simple in processing, it can be easily configured by hardware. If the method of holding the maximum value is processed by an analog circuit or the like, a storage device is not necessary and it can be deleted at all.

Since the second method does not search all data, it has an advantage that the processing time is short even if k becomes large. Therefore, it is suitable for a control system having many axes to be judged by one steady state detection unit.

Further, these methods can be directly applied not only as a stability check after driving, but also as an in-position check method during non-driving.

In particular, when the second method is used, an error occurs even when the measured value suddenly shifts due to electrical noise or disturbance in the measuring instrument, even though the controlled object does not move. It can be none. In addition, even if the controlled object moves, if the high-frequency component is insensitive to the process actually performed on this device, there is also a demand that it should not be an error.

As shown in FIG. 9, conventionally, it has been necessary to deal with the above-mentioned disturbance by widening the tolerance so as not to cause a position error. However, originally, the tolerance should be limited to the range of steady vibration, and the tolerance should be limited. Is not desirable to deal with.

According to the second method, it is possible to keep the tolerance within the range of steady vibration, and even if a disturbance occurs, an error will occur if the dispersion at that time is within the tolerance. There is no.

Another embodiment of the controlled object according to the present invention is shown in FIG.

FIG. 10A is a side view of a mechanism that can be driven in the Z, ωx, and ωy directions, and FIG. 10B is a top view.

In this embodiment, inch worms 1008, 1010, 1012 moving in the z direction are placed at three points on an arc centered on the center of the object 1002 and the object 1002 is held. 1 inch worm each
Reference numerals 008, 1010 and 1012 denote the first drive control unit to
It is connected to a third drive control unit (both not shown) and driven by a pulse (control output) output from each drive control unit. Also, each inch worm 1008, 101
Gap sensors 1009, 1011 and 1013 are prepared on concentric circular arcs corresponding to 0 and 1012, and measure the distance to the back surface of the object 1002. The measured gap value is input to each drive control unit as a primary sensor input.

On the other hand, the posture of the object 1002 is measured by laser interferometers 1001 and 1005 for measuring the tilt component. ωy laser interferometer 1001
Irradiates the object 1002 with the laser beam 1004 and measures its tilt component ωy. In addition, the ωx laser interferometer 1005 is a laser beam 101
4 is directed toward the object and its tilt component ω
Measure x. The tilt component (ωx, ωy) obtained by these is input to the steady state detection unit as a secondary sensor input.

In the present embodiment configured as described above, a control system with n = 2 and m = 3 is applied to the control mechanism shown in FIG.

The operation of the control device when the object 1002 is tilted will be described. The flowchart uses FIG. 3 similarly to the above-described example.

First, the target value (ωx, ωy) is designated. Then, the target values (ωx, ωy) are distributed to the three Z axes based on the mounting position coordinates of each gap sensor, and command values 1 to 3 are obtained. The determined command values 1 to 3 are output to the first to third drive control units.

Then, the first to third drive control units operate to drive the inchworms 1 to 3 until the primary sensor inputs 1 to 3 become the command values 1 to 3, and eventually become the steady state.

At this time, the output of the laser interferometer, which is the input of the secondary sensor, is not always about to converge to the target value. Therefore, it waits for a steady state by the above-mentioned stability check method.

When it is confirmed that the output of the laser interferometer is stable, each tilt component (ω) is calculated according to the following equation (3).
x, ωy) shift amount is obtained.

Ωx deviation amount = ωx target value−ωx current value ωy deviation amount = ωy target value−ωy current value (3) The calculated deviation amounts are compared with preset tolerances. Then, it is determined whether or not the drive is required. If the absolute value of the shift amount is within the tolerance, the drive is not performed and the present process is terminated. Each Z if out of tolerance
Drives the drive of the axis. The drive-in amount is calculated by distributing the respective shift amounts of the tilt component calculated by the above equation to the Z-axis based on the mounting position coordinates of the gap sensors.

By adding the drive-in drive amount obtained as described above to the previous command values 1 to 3, new command values 1 to
3 is obtained, and this is output to the first to third drive control units, and the above processing is repeated.

[0086]

Since the present invention is constructed as described above, it has the following effects.

Even in the case of overshoot, it is not erroneously recognized as being in a steady state, and even in a servo system that is stable with an offset, it is correctly and quickly recognized that the steady state has been reached, and the deviation amount is determined. Since it can be corrected, there is an effect that precise and highly stable control can be performed in a short time.

Further, the present invention can be applied to a system having no ordinary offset and also to in-position check, and even if it is used for a control object having many drive axes, it can be controlled by the same method as all axes, so that the processing is simple. In addition, there is an effect that it becomes clear and quick control can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram describing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is an example of a controlled object according to the present invention.

FIG. 3 is a flowchart showing the operation of the control device of the present invention.

FIG. 4 is a diagram for explaining correction of a command value.

FIG. 5 is a flowchart showing a first stability check method used in the present invention.

FIG. 6 is a graph for explaining a first stability check method.

FIG. 7 is a flowchart showing a second stability check method.

FIG. 8 is a graph for explaining a second stability check method.

FIG. 9 is a graph for explaining tolerance against noise.

FIG. 10 is another example of the controlled object according to the present invention.

FIG. 11 is a graph showing a conventional drive completion detection method.

FIG. 12 is a block diagram for explaining that an offset occurs in a feedback circuit.

[Explanation of symbols]

2 Steady state detection unit 3 Storage device 4 Comparison unit 5 Command value generation unit 11 First drive control unit 12 Second drive control unit 201, 1001, 1005 Laser interferometer 202, 1004, 1014 Laser beam 203, 401, 1002 Object 204 , 403 X stage 205, 404 Y stage 206, 1003 Base 207 Motor 208 Encoder 402 Tilt stage 1008, 1010, 1012 inch worm 1009, 1011, 1013 Gap sensor S301-S306, S501-S503, S701-
Step S706

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

Claims (6)

[Claims] 1. A measuring means for measuring the position of a controlled object, a calculating means for obtaining a deviation amount between a current value and a target value of the controlled object, and a control object for the controlled object according to the deviation amount obtained by the calculating means. A positioning control device comprising: a control signal output means for generating and outputting a control signal for driving; a positioning control device comprising a steady state confirmation means for confirming that the controlled object has entered a steady state. . 2. The positioning control device according to claim 1, wherein the deviation amount is obtained after it is confirmed by the output of the steady state confirmation means that the controlled object has entered a steady state. Control device. 3. The positioning control device according to claim 1, wherein the steady state confirmation means selects a part of the information obtained through the measuring means, and when the variation of the selected information becomes small. A positioning control device characterized by recognizing that a steady state has been entered. 4. The positioning control device according to claim 3, wherein the small variation is determined by the small difference between the maximum value and the minimum value. 5. The positioning control device according to claim 3, wherein the smaller dispersion is determined by the smaller dispersion. 6. A stage device, wherein the stage is controlled by the positioning control device according to any one of claims 1 to 5.