JPH0535335A - Controller for stage - Google Patents

Abstract

PURPOSE:To improve the control characteristic and reliability of the controller for a stage. CONSTITUTION:This controller 10 consists of a selection part 15 to output the output signal of a compensator 12 to any one of (n) pieces of output terminals, (n) pieces of resonance removal parts 13-13n, to which output signals are respectively inputted from the respective output terminals of the selection part 15, a little differring cut-off frequencies and cut-off peak values with an initial state as a center, resonance detection part 16 to prepare a signal for resonance detection according to a displaced variable X and selection judgement part 17 to control the selection part 15 while judging either a non-resonated state or a resonanted state according to the signal for resonance detection; and when the selection judgement part 17 judges the resonated state, the selection part 15 is controlled so as to first output the output signal of the compensator 12 to the output terminal connected to the resonance removal part having the adjacent cut-off frequency and to afterwards output the signal to the output terminal connected to the resonance removal part having the adjacent cut-off peak value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stage control device for controlling the amount of displacement of a stage which is slid on a slide guide by a drive device.

[0002]

2. Description of the Related Art FIG. 11 is an explanatory view of a conventional example of a stage controller of this type.

The stage 61 has first and second sliding guides 62 ₁ and 62 ₂ provided on the front side and the back side in the figure, each of which is a slide guide or a rolling guide.
Is slid by a driving device including an actuator 63 and a feed screw 64. Also, stage 6
The control device 70 that controls the displacement amount of 1 has a subtracter 71 that obtains a difference X ₀ −X between a predetermined target value X ₀ and the displacement amount X.
The output signal (difference X ₀ −X) of the subtractor 71 is input, and the compensator 72 is formed of a known PID compensator or the like, and the compensator 7.
The output signal of the resonance removing unit 73 is input to the actuator 63 via the amplifier 75.

The amount of displacement of the stage 61 is controlled as follows.

(1) A displacement amount X of the stage 61 is measured by a laser interferometric measuring system including a mirror 65 provided on the upper surface of the stage 61 in the figure and a laser length measuring device 66 for emitting a laser beam toward the mirror 65. To do.

(2) In the control device 70, the subtracter 71 subtracts the target value X ₀ from the displacement X, and the difference X ₀ −
X 1 is input to the actuator 63 via the compensator 72, the resonance removing unit 73 and the amplifier 75.

Here, the resonance removing section 73 operates as follows.

As shown in FIG. 12A, the stage 61
The open loop frequency characteristic generally has a high-order resonance peak, and the phase is greatly delayed at the resonance frequency (frequency of resonance peak) fc as shown in FIG. As a result, if the output signal of the compensator 72 is input to the actuator 63 without passing through the resonance removal unit 73 to form a closed loop, resonance may occur, which is not preferable. Therefore, the resonance removing unit 7
It is common practice to provide 3 in a closed loop to eliminate the higher order resonance peaks. That is, as the resonance removing unit 73, a notch filter having a narrow-band cutoff characteristic at the resonance frequency fc is used as shown in FIG. 13, and the output signal of the compensator 72 is passed through the notch filter to obtain the gain characteristic of the closed loop system. Is converted as shown in FIG. 14 to remove the high-order resonance peaks and stabilize the system.

[0009]

However, in the above-described conventional stage control device 70, the resonance frequency is reduced due to the deterioration of the viscosity of the brease of the _two sliding guides 62 ₁ and 62 ₂ and the deterioration of the rigidity of the bearing 67. Although fc and the resonance peak value (peak value of the resonance peak) gradually change, the frequency characteristic of the notch filter that constitutes the resonance removing unit 73 is fixed. Therefore, when the resonance frequency fc and the resonance peak value change, Has a problem that the resonance peak cannot be completely removed, which causes oscillation of the entire system. That is, when the resonance frequency fc decreases, the resonance frequency fc does not match the cutoff frequency (notch frequency) of the resonance removing unit 73, and the gain characteristic of the output signal from the resonance removing unit 73 is shown in FIG. As shown, the resonance peak and the anti-resonance peak appear as they are. Also, when the resonance peak value fluctuates, the resonance cannot be removed sufficiently,
As shown in FIG. 16, the resonance peak remains.

As a means for solving this problem, it is conceivable to widen the band stop region of the notch filter which constitutes the resonance removing section 73, but there is a problem that the control characteristic is deteriorated. Further, as another means, it is conceivable to perform maintenance and parameter adjustment manually, but there is a problem that specialized knowledge is required and reliability is lowered.

An object of the present invention is to provide a stage control device capable of improving control characteristics and reliability.

[0012]

A stage control device of the present invention is a stage control device for controlling a displacement amount of a stage which is slid on a slide guide by a drive device. A compensator to which a difference from the quantity is input, a selection unit to which the output signal of the compensator is input and which outputs the output signal of the compensator to any one of a plurality of output terminals, and a selection unit of the selection unit. A plurality of resonance elimination units having cut-off frequencies and cut-off peak values that are slightly different from each other around the initial state, to which the output signals from the output terminals are respectively input, and the displacement amount is input, and resonance detection is performed based on the displacement amount. A resonance detection unit that generates a use signal, and a selection determination unit that controls the selection unit by determining whether the resonance detection signal generated by the resonance detection unit is in a non-resonance state or a resonance state. Including the selection When the section determines that it is in a resonance state, it controls the selection section to output the output signal of the compensator to the output terminal connected to the resonance removal section having the cutoff frequencies adjacent to each other, and then the cutoff frequency. The selection unit is controlled so that the output signal of the compensator is output to the output terminal connected to the resonance removal unit having the adjacent peak value.

Here, the resonance detecting section has a bandpass filter, and the output amplitude of the bandpass filter is created as the resonance detecting signal, and the selection determining section outputs the reference value set in advance and the output. It may be judged from the difference with the amplitude whether it is in the non-resonant state or the resonant state.

Further, the resonance detecting section has a fast Fourier transforming means, creates a frequency spectrum obtained by the fast Fourier transforming means as the resonance detecting signal, and the selection judging section makes a reference frequency preset. It may be determined from the difference between the spectrum and the frequency spectrum whether the resonance state or the non-resonance state.

[0015]

The controller of the stage according to the present invention includes a plurality of resonance elimination units to which the output signals from the output terminals of the selection unit are respectively input and whose cutoff frequencies and cutoff peak values are slightly different from each other around the initial state. The selection determination unit determines whether it is in a non-resonance state or a resonance state from the resonance detection signal created by the resonance detection unit, and when the selection determination unit determines that the resonance state is present, First, by controlling the selection unit to output the output signal of the compensator to the output terminal connected to the resonance removal unit adjacent to the cutoff frequency, the resonance removal unit having the cutoff frequency matching the resonance frequency can be selected,
After that, when the selection determination unit determines that the resonance state is still present, the selection determination unit controls the selection unit to output the output signal of the compensator to the output terminal connected to the resonance removal unit having the adjacent cutoff peak value. Since the resonance removing unit having the cutoff peak value that matches the resonance peak value can be selected, the displacement amount of the stage can be controlled in a state where there is no resonance.

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

FIG. 1 is a block diagram showing a first embodiment of a stage controller according to the present invention.

The control device 10 comprises a subtracter 11 for obtaining a difference X ₀ -X between a predetermined target value X ₀ and a displacement amount X, and a PID compensator to which an output signal of the subtractor 11 is input. The point that the compensator 12 is included is the same as that of the conventional control device 70 shown in FIG. 11, but a selection is made to output the input output signal of the compensator 12 to any one of the n output terminals. The output of the output signals from the output terminals of the selection unit 15 and the resonance removal units 13 _{1 to} 13 _{n of} which the cutoff frequency and the cutoff peak value are slightly different from each other around the initial state, The resonance detection unit 16 that receives the amount X and generates a resonance detection signal from the displacement amount X, and determines whether the resonance detection signal is a non-resonance state or a resonance state based on the resonance detection signal generated by the resonance detection unit 16. Then, the selection unit 1
5 includes a selection judgment unit 17 for controlling 5 and the selection judgment unit 1
When it is determined that 7 is in the resonance state, the selection unit 1 outputs the output signal of the compensator 12 to the output terminals connected to the resonance removal units 13 _{1 to} 13 _n having the cutoff frequencies adjacent to each other.
5 is controlled, the compensator 12 is connected to the output terminals connected to the resonance removing units 13 _{1 to} 13 _n having the cutoff peak values adjacent to each other.
The control unit 70 is different from the conventional control device 70 in that the selection unit 15 is controlled to output the output signal of.

Here, each of the resonance removing portions 13 _{1 to} 13 _n is formed of a narrow band cutoff filter such as a notch filter. In the initial state, the characteristics of the resonance peak (resonance frequency fc and resonance peak value) can be known from the design value or by performing an evaluation test. It is possible to determine the characteristic of the notch filter (the initial state of the cutoff frequency and the cutoff peak value) that can most effectively remove the resonance peak with respect to the resonance characteristic thus found. The resonance removing unit composed of this notch filter is prepared as the first resonance removing unit 13 ₁ .

When the resonance frequency fc gradually changes from the initial state, the resonance frequency fc is changed to the first resonance removing unit 13.
_Since the cutoff frequency is different from that of 1, the first resonance removing unit 1
3 In ₁ sufficiently resonance peak can not be removed. Therefore, as shown in FIG. 5, the cutoff frequency is slightly shifted with respect to the first resonance removal unit 13 ₁ with the same cutoff peak value, and the resonance peak that cannot be removed by the first resonance removal unit 13 ₁ is removed. A resonance removing unit composed of a notch filter having such characteristics is prepared as the second resonance removing unit 13 ₂ .

Further, the first and second resonance removing sections 1 are provided so as to cope with the case where the resonance frequency cannot be removed even if the second resonance removing section 13 ₂ is used to change the resonance frequency.
A resonance removing unit composed of a notch filter in which the cutoff frequency is slightly shifted with respect to 3 ₁ and 13 ₂ with the same cutoff peak value is prepared as the third resonance removing unit 13 ₃ .

In addition, as shown in FIG. 6, the resonance removing section formed of a notch filter having a characteristic in which the cutoff peak values are slightly different for the same cutoff frequency is used to remove other resonances even if the resonance peak value changes. Parts 13 _{m to} 13 _n are prepared.

In this way, as shown by the squares in FIG. 7, the resonance peak is expected to fluctuate within the range of the frequency and the peak depth (peak value) around the initial state in the center of the drawing. Resonance peaks are removed for all conditions, and resonance removal sections with slightly changed characteristics (cutoff frequency and cutoff peak value) are prepared as comprehensively as possible so that resonance peaks are not detected by the resonance detection section. deep.

When the cutoff frequency band of each resonance removing section 13 _{1 to} 13 _n is narrow, the difference in cutoff frequency between the resonance removing sections 13 _{1 to} 13 _n is small, and a large number of resonances exist within a certain frequency range. It is necessary to prepare the removal units 13 _{1 to} 13 _n . On the other hand, when the cutoff frequencies of the resonance removal units 13 _{1 to} 13 _n are wide, the difference in cutoff frequency between the resonance removal units 13 _{1 to} 13 _n can be increased, and the resonance removal units 13 ₁ to 13 _n number n
Can be reduced. Resonance removing units 13 _{1 to} 13 _n
Does not need to be the same in the cut-off frequency band, and the band is narrowed in an important part to finely adjust the resonance elimination parts 13 ₁ to ₁ 1.
It is also possible to reduce the number n of the resonance removing units 13 _{1 to} 13 _n by preparing 3 _n and widening the band in a relatively unimportant portion. Similarly, with respect to the cutoff peak value, it is possible to close the interval in the important part and leave the interval in the relatively unimportant part. However, it is necessary to prepare a resonance removing unit having the same cutoff peak value for each cutoff frequency. This state is shown in FIG.

When the number n of the resonance elimination units 13 _{1 to} 13 _n is small, it may be configured by an analog circuit, but since it is generally considered to be large, it is realized by software using a computer. Is effective.

The resonance detector 16 needs to operate in the frequency band in which the resonance peak including the resonance frequency fc is expected to change, but must not operate in the other frequency bands. In the present embodiment, the resonance detector 16 is composed of a bandpass filter, and the output amplitude of the bandpass filter is created as the resonance detection signal.

The selection judgment section 17 has a preset reference value R and the output amplitude (hereinafter referred to as "detection value a") of the bandpass filter which is inputted as the resonance detection signal from the resonance detection section 16. It is determined whether it is in a non-resonant state or in a resonant state based on the difference between. That is, the selection determination unit 17
As shown in FIG. 2 (A), when the detected value a is smaller than the reference value R, it is judged to be in the non-resonant state. On the other hand, as shown in FIG. 2 (B), the detected value a is larger than the reference value R. Is also large, it is determined that the resonance state exists.

Resonance removing section 13 ₁ -in control device 10
The selection of 13 _n is performed as follows.

(1) The resonance elimination section indicated by "1" in FIG. 9 is connected to the resonance elimination section indicated by "0" in FIG. The selection determination unit 17 controls the selection unit 15 so that the output signal of the compensator 12 is output to the output terminal.

(2) The test operation is carried out in this state, and the selection judging section 17 judges whether it is the non-resonant state or the resonant state by the method described above.

(3) When the selection judging section 17 judges that the resonance state is not present, the operation is started with the resonance removing section indicated by "1" in FIG. 9 being selected.

(4) When the selection judgment section 17 judges that the resonance state is present, the resonance elimination section shown by "1" in FIG. 9 is removed from the initial resonance elimination section shown by "0" in FIG. The selection determination unit 17 outputs the output signal of the compensator 12 to the output terminal connected to the resonance removal unit indicated by "2" in FIG. 9 in which the cutoff frequency differs by one step in the direction opposite to the unit. After controlling the selection unit 15, it is similarly determined whether it is in the non-resonant state or the resonant state.

(5) When the selection judgment section 17 judges that the resonance state is not present, the operation is started with the resonance elimination section indicated by "2" in FIG. 9 selected.

(6) When the selection judging section 17 judges that the resonance state is present, the case where the resonance removing section shown by "1" in FIG. 9 is selected and the resonance removing section shown by "2" in FIG. 9 are selected. It is determined which one has a smaller degree of resonance than when a part is selected.

(7) When it is judged that the resonance is smaller when the resonance eliminating section indicated by "1" in FIG. 9 is selected,
Resonance canceling parts in the same direction as the resonance canceling part shown in FIG. 9 are sequentially selected from the side closer to the original resonance canceling part shown in “0” in FIG. Judge whether it is in a state.

(8) When the selection judgment section 17 judges that the resonance state is not present, the operation is started with the resonance elimination section selected at that time.

(9) As compared with the resonance state of the preceding resonance eliminating unit for each judgment of each resonance eliminating unit, when the resonance state of the preceding resonance eliminating unit has a smaller degree of resonance, The determination is stopped at that point, and the previous resonance removing unit is selected.

(10) That is, the cutoff frequency indicated by "1" in FIG. 10 is equal to the cutoff frequency indicated by "0" in FIG. 10 and the cutoff peak value differs by one step. After selecting, it is determined whether it is in a non-resonant state or a resonant state.

(11) When the selection judgment section 17 judges that the resonance state is not present, the operation is started with the resonance elimination section indicated by "1" in FIG. 10 being selected.

(12) When the selection judging section 17 judges that the resonance state is present, the resonance removing section shown by "0" in FIG. 10 is different from the resonance removing section shown by "1" in FIG. After selecting the resonance elimination part indicated by "2" in FIG. 10 in which the cutoff peak value differs by one step in the opposite direction, it is judged whether it is in the non-resonance state or the resonance state.

(13) When the selection judging section 17 judges that the resonance state is not present, the operation is started with the resonance eliminating section indicated by "2" in FIG. 10 being selected.

(14) When the selection judging section 17 judges that the resonance state is present, the case where the resonance removing section shown by "1" in FIG. 10 is selected and the resonance removing section shown by "2" in FIG. It is determined which one has a smaller degree of resonance than when a part is selected.

(15) When it is judged that the resonance is smaller when the resonance eliminating section indicated by "2" in FIG. 10 is selected, the same direction as that of the resonance eliminating section indicated by "2" in FIG. 10, the resonance removing unit is sequentially selected from the side closer to the resonance removing unit indicated by "0" in FIG. 10, and it is determined whether the resonance removing unit is in the non-resonance state or the resonance state.

(16) When the selection judging section 17 judges that the resonance state is not present, the operation is started with the resonance eliminating section selected at that time.

By doing so, it is possible to select the resonance removing portions 13 _{1 to} 13 _n which are in the non-resonant state with a small number of tests.

Therefore, by controlling the displacement amount of the stage shown in FIG. 11 by the control device 10 of the present embodiment, it is possible to always operate in a resonance-free state.

Next, the second stage controller of the present invention will be described.
An example will be described.

In the control device of this embodiment, the resonance detecting section has the fast Fourier transforming means, creates the frequency spectrum obtained by the fast Fourier transforming means as the resonance detecting signal, and the selection judging section presets the frequency spectrum. It is different from the control device 10 shown in FIG. 1 in that it is determined whether it is in a non-resonant state or a resonant state based on the difference between the reference frequency spectrum and the frequency spectrum.

That is, as the reference frequency spectrum,
As shown by the solid line in FIG. 3, the gain characteristic (reference pattern) in the frequency band f _w in which the resonance peak including the resonance frequency fc is expected to change is set in advance, and the gain characteristic in the frequency band f _w obtained during the test operation is set. The difference between the gain characteristic (shown by the broken line in the figure) and the reference pattern is detected by the least square method or the like, and it is determined whether the state is the non-resonant state or the resonant state depending on the magnitude of the difference.

Since the control device of this embodiment uses the fast Fourier transform to determine whether it is in the non-resonant state or in the resonant state, it is possible to perform higher control than the control device 10 shown in FIG. Become.

Next, the third stage controller of the present invention will be described.
An example will be described.

The control apparatus of the present embodiment has a frequency spectrum (shown by a solid line in the figure) obtained by the fast Fourier transform means and has a preset allowable maximum value (shown by a broken line in the figure) as shown in FIG. If there is a part that exceeds the
The difference from the control device of the second embodiment described above is that the selection determination unit determines that it is in the resonance state.

Also in this control device, oscillation of the entire system can be prevented in advance.

Next, the fourth stage controller of the present invention will be described.
An example will be described.

In the control device of this embodiment, the resonance detecting section has a bandpass filter and a fast Fourier transforming means, and the selection judging section has the above-mentioned first and second embodiments.
It also has the judgment function according to the embodiment.

That is, when the fast Fourier transform is used to determine the non-resonant state or the resonant state as in the second embodiment, the calculation time for obtaining the frequency spectrum is long. Although there is no problem in making the above judgment during the test operation, it is difficult to make the above judgment in real time during the driving. Therefore, at the time of test operation, it is determined whether the resonance state is in the non-resonance state or the resonance state by using the fast Fourier transform, and whether the resonance peak fluctuates during the operation is determined by the output amplitude of the bandpass filter. When it is determined that the resonance peak fluctuates from the output amplitude, the operation is temporarily stopped, another resonance removing unit is selected again, and then the operation is restarted.

[0056]

As described above, the present invention has the following effects.

The stage controller according to the present invention includes a plurality of resonance elimination units to which the output signals from the output terminals of the selection unit are respectively input and whose cutoff frequencies and cutoff peak values are slightly different from each other around the initial state. The selection determination unit determines whether it is in a non-resonance state or a resonance state from the resonance detection signal created by the resonance detection unit, and the selection determination unit,
When it is determined that the resonance state is present, the selection unit is controlled so that the output signal of the compensator is output to the output terminal connected to the resonance removal unit whose cutoff frequency is adjacent, and then the resonance removal unit whose cutoff peak value is adjacent. By controlling the selector so that the output signal of the compensator is output to the output terminal connected to, it is possible to control the displacement of the stage without resonance at all times, improving control characteristics and reliability. Can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a stage controller according to the present invention.

FIG. 2 is a diagram showing a method of determining whether it is in a non-resonant state or a resonant state in the selection determining section shown in FIG.
(A) is a diagram showing a magnitude relationship between a reference value and a detected value when it is determined that a non-resonant state is present, and (B) shows a magnitude relationship between a reference value and a detected value when it is determined to be a resonant state. FIG.

FIG. 3 is a diagram showing a method of determining whether a state is a non-resonant state or a resonant state using a fast Fourier transform.

FIG. 4 is a diagram showing another method of determining whether a state is a non-resonant state or a resonant state using a fast Fourier transform.

5 is a diagram showing one gain characteristic of the resonance removing unit shown in FIG.

FIG. 6 is a diagram showing another gain characteristic of the resonance removing unit shown in FIG. 1.

FIG. 7 is a diagram showing an example of gain characteristics of each resonance elimination unit shown in FIG. 1.

FIG. 8 is a diagram showing another example of the gain characteristic of each resonance elimination unit shown in FIG.

FIG. 9 is a diagram for explaining the operation of the selection determination unit shown in FIG.

FIG. 10 is a diagram for explaining the operation of the selection determination unit shown in FIG.

FIG. 11 is an explanatory diagram of a conventional example of a stage control device of this type.

12 is a diagram showing an open-loop frequency characteristic of the stage shown in FIG. 11, (A) showing a gain characteristic,
(B) is a diagram showing a phase characteristic.

FIG. 13 is a diagram showing a gain characteristic of a notch filter most commonly used as the resonance removing unit shown in FIG.

FIG. 14 is a diagram showing a gain characteristic of the displacement amount shown in FIG. 11.

15 is a diagram showing the gain characteristic of the displacement amount shown in FIG. 11 when the frequency of the resonance peak is lower than the frequency fc shown in FIG.

16 is a diagram showing a gain characteristic of the displacement amount shown in FIG. 11 when the peak value of a resonance peak varies.

[Explanation of symbols]

10 Control Device 11 Subtractor 12 Compensator 13 _{1 to} 13 _n Resonance Removal Unit 15 Selection Unit 16 Resonance Detector 17 Selection Judgment Unit X Displacement X ₀ Target Value R Reference Value a Detected Value fc Resonance Peak Frequency fw Frequency Band 1

Claims (3)

[Claims] 1. A stage control device for controlling a displacement amount of a stage which is slid on a slide guide by a drive device, and a compensator to which a difference between a predetermined target value and the displacement amount is input, An output signal of the compensator is input, and a selection unit that outputs the output signal of the compensator to any one of a plurality of output terminals and an output signal from each of the output terminals of the selection unit are input. A plurality of resonance removal units whose cutoff frequencies and cutoff peak values are slightly different from each other around the initial state; a resonance detection unit which inputs the displacement amount and creates a resonance detection signal from the displacement amount; A selection determination unit that controls the selection unit by determining whether the resonance detection signal is in a non-resonance state or a resonance state from the resonance detection signal created by the unit, and the selection determination unit is in a resonance state. When it is determined that After controlling the selection unit to output the output signal of the compensator to the output terminal connected to the resonance removal unit having the cutoff frequency adjacent thereto, the cutoff peak value is connected to the resonance removal unit adjacent to the resonance removal unit. A control device for a stage, wherein the selection unit is controlled to output the output signal of the compensator to the output terminal. 2. The resonance detection unit has a bandpass filter, and the output amplitude of the bandpass filter is created as the resonance detection signal, and the selection determination unit includes a preset reference value and the output amplitude. 2. The stage control apparatus according to claim 1, wherein it is determined whether it is in a non-resonant state or in a resonant state based on a difference between and. 3. The resonance detecting section has a fast Fourier transforming means, creates a frequency spectrum obtained by the fast Fourier transforming means as the resonance detecting signal, and the selection judging section sets a preset reference frequency. 2. The stage control device according to claim 1, wherein it is determined whether it is in a non-resonant state or a resonant state based on a difference between a spectrum and the frequency spectrum.